HOW TO: Make your untuned PFC basemap safer/idle better (no Datalogit needed)
 

--Note: revised 11/22/2010 per Raymond's request to clarify/revise certain points - Gracer7-rx7


First I want to credit Chuck Westbrook for a lot of my PFC knowledge and thank him for his many contributions to this forum. He has passed on his PFC tuning notes to me. If you have a Datalogit or just want to know more about the PFC you can send me a PM about the notes package.

Key words:

idle surging, boost creep, PFC, safety, knock, detonate, tune, Commander, Power, FC, AFR

I have dished out this advice in bits and pieces in other people's threads, and now I want to put together a full writeup for all PFC users running an untuned unit on the base map who just have a Commander at their disposal. This is not a substitute for a real tune, just a way for owners to get some incremental improvements in driveability and safety.

Introduction

Most people have PFC model #414-Z004 (look on the box) if they have a 92-95 car. The basemap isn't so bad. The leading timing map, while not perfect, is safe for most setups (including many single turbo setups IMO), and the trailing timing just needs a few minutes of tediously changing values across-the-board to make it safer. Fuel can be made safer using a fuel correction feature that is buried in the Commander's menus. The idle problems that people encounter with the PFC can take a lot of time to figure out, but I'm going to give a basic strategy to try before you give the car to a professional. I also personally think the PFC controls boost fine as long as you understand how it works and set it up properly, but unfortunately the documentation for this feature is sketchy.


Idle

One of the first things owners may notice when they get a PFC is that their idle may be surging. The PFC is simply more sensitive than the factory ECU is, as OEM computers tend to be pretty forgiving. Usually the culprit is too much air getting past the throttle plates, or a lean mixture due to an untuned correction map. I'm just going to give the advice that is usually given around here. What you are going to do is decrease the amount of air entering past the throttle plates, and then see if the PFC will adjust to this new condition.

Remove/back off the TB elbow. Tighten the air adjust screw all the way in, then back it out 1/4 to 1/2 turn, then reinstall the elbow.


https://www.rx7club.com/attachment.p...1&d=1243108512

Now reset the Power FC at Etc. --> all data init (you will lose all your settings from this). Then turn off O2 feedback (your stock O2 sensor now does nothing) under Etc. --> Function select. There should be some funny Japanese -ooking characters there. Perform the idle learning procedure as outlined in the PFC manual:

https://www.rx7club.com/attachment.p...1&d=1243110575

Don't tighten that screw in all the way. If you can't figure the idle out, leave it to your tuner. Or get Chuck's tuning notes and read the sections on setting the idle with the ISC unplugged/removed. He also has a more thorough discussion of how to adjust all the TB screws.

Timing

Here is the leading timing map for Power FC model #414-Z002 , the early production ones that most people don't have. Supposedly this is very similar to the stock ECU's timing map. X axis is RPM (the "N" columns in the Commander), Y axis represents MAP (the "P" rows in the Commander). 10000 units is about 1 bar, so at 10psi boost you are at something near 17000 units. (.70 kg/cm^2 or so, 1 kg cm^2 = ~14.22 psi I think ) The boost readings on the Commander are not completely accurate without recalibrating the MAP sensor using a Datalogit. The PFC usually reads a little bit lower than a mechanical gauge without this calibration.

https://www.rx7club.com/attachment.p...1&d=1243103323

Now here is the leading timing map for Power FC model #414-Z004, the model that most people have. Notice less leading timing advance in the boost area? A higher number means the plug fires earlier, a lower number means the plug fires later and there will be less chance of detonation.

https://www.rx7club.com/attachment.p...1&d=1243103323

The basemap trailing timing on the PFC model #414-Z004 , the model that most people have, is less safe once you get over about 10psi (and the timing progression is sloppy). But the safety aspect is correctable even with a Commander just by tediously going through the IGT screen, rows P16-P18 (8.5psi to 14 psi range), and retarding the timing (decrease the timing value) by about 4 degrees in every cell over say 2400 rpm (N7 and higher columns in the commander). So take whatever value is in a particular cell, subtract 4 from it, and then input that new value in the cell.

https://www.rx7club.com/attachment.p...1&d=1243109296

Fuel

To make the fuel safer (provided that your fuel pump and injectors can flow enough) you can quickly add fuel across the board based on RPM. It is a sub menu under setting --> PIM volt.

Get to the RPM correction screen and add whatever % fuel you think may be necessary. While cars with less mods may need no adjustments at all, more modded cars could start with 105-110%. You can fiddle with it more if you have a wideband. I'm pretty sure the RPM based correction would affect your AFR's under cruising as well.

You could also do boost-based compensation (the bottom screen there) but since it is in MAP sensor voltage you would be doing a lot of guesswork. Just try to get the AFR under boost to be somewhere in the 11.0-11.5 range, but don't go too rich because the car will worse and build up a lot of carbon. Remember that we are doing this to decrease the chance of the car detonating, not tuning for power.

Protecting Your Motor With Overboost Fuel Cut

Without some form of overboost protection, you can blow your engine up in the event of boost control failure. Overboost fuel cut isn't the only way to protect your engine from boost control failure, but it is the simplest to implement. Later in this thread (page 2) I will discuss how to calculate the values you need to set an overboost fuel cut at whatever boost level you want.

These guideline values apply only for engines running an external boost controller (EBC, MBC) with the stock MAP sensor using the default MAP sensor calibration.

If you intend to run 10psi of boost with an external controller, set all boost settings in the boost menu to .55 kg/cm^2 .

If you intend to run 12psi of boost with an external controller, set all boost settings in the boost menu to .70 kg/cm^2 .

If you intend to run 14psi of boost with an external controller, set all boost settings in the boost menu to .95 kg/cm^2 .

To make the fuel cut more likely to kick in (PFC allows less overboosting), lower this value in .05 increments. To make it less likely to kick in (PFC allows more overboosting), raise this value in .05 increments. If you feel like the engine has "hit a brick wall" you may have hit fuel cut, so you need to check all aspects of your boost control system.

Boost Control

This applies for engines running the PFC as a boost controller. The default settings (option 1 in the boost menu):

Boost (in Kg/cm^2) Precontrol/Wastegate solenoid duty cycles

Primary .80 56%
Secondary .70 64%

Besides affecting the fuel cut, think of the boost value as a "coarse" adjustment to your boost, while the duty % is a "fine" adjustment to the boost. I usually set the primary value to the same value as the Secondary number. If you are overboosting, start by setting boost to

Pr .70 56%
Sc .70 56%

And if you have to, try going back and forth with lowering both the boost and duty values. Otherwise I would leave it to the tuner or just get a separate boost controller. Remember that playing with the boost setting in the commander will not fix a mechanical limitation such as an undersized wastegate.

I have done extensive testing of the PFC boost control logic on a sequential car and it is documented in this thread: https://www.rx7club.com/power-fc-forum-47/pfc-wasgate-precontrol-710953/ from post #22 on. The PFC can also be used to control boost on a single turbo or non sequential twin turbo car but that's a little more involved than I want to cover here.


Conclusion

The PFC base leading map, coupled with some adjustments to the trailing map and a fuel correction adjustment will make your car much safer to drive until you can get a proper tune done with someone you are comfortable with.

threads like this is what this forum is really about...............THANKS!!!!

a couple things. when you reset the Power FC before the idle learning procedure, you must turn the key off and back on immediately after you select the reset option from the menu.

the other thing is the fuel injector correction menu, which I meant to put in the first post as I refer to the pictures in it:

https://www.rx7club.com/attachment.p...1&d=1243124607

I have personally never used the pressure sensor voltage (boost-based as opposed to rpm-based) fuel enrichment map in the diagram above. But I will say that according to my Datalogit logs, 10psi is a little less than 4 volts on the default MAP sensor calibration. So if you want to ramp up enrichment when it hits near full boost, you could try something like this:

PIM 1.0V 100%
PIM 1.5V 100%
PIM 2.0V 100%
PIM 2.5V 100%
PIM 3.0V 100%
PIM 3.5V 102%
PIM 4.0V 105%
PIM 4.5V 105%

I wouldn't use both the rpm and the pressure sensor voltage table at the same time though.

"threads like this is what this forum is really about...............THANKS!!!!"

couldn't have said it better.

hc

I've used the same techniques on my car, thanks for posting this, you obviously put a lot of time and effort into this, it's very much appreciated. YOu can do quite a bit with the commander, but to really take advantage of PFC, you need a datalogit :) (I know the point of the thread is that no datalogit is needed)

I know this thread is about doing this without a datalogit, however, for those of us who do have a datalogit, do you have this optimized basemap available for datalogit users ?

Thanks,
:-) neil

I don't think it would be appropriate for me to post maps here. What I have suggested can be done with a Datalogit in 30 seconds if you know how to use the program. Timing can be adjusted by selecting multiple cells at once and using the "-" key to retard. The same menus from the Commander that I discussed are also in the Datalogit software in similar form. That's all I'm going to say about that, I want to keep this thread focused.

should be sticked in the proper section.
glad I've checked the forum today!

In the section on boost control, I mentioned a set of boost values to try if you happened to be overboosting some:

Pr .70 56%
Sc .70 56%

.70 kg/cm^2 is 10psi when you do the math (multiply by 14.22). But the problem is, the PFC usually reads lower than a mechanical gauge unless you change the MAP sensor calibration with a Datalogit. So you may actually have to try a lower boost level like .65 or .60 if you want to stay at 10psi according to whatever gauge you have.

After a WOT run, press the up key on the Commander in Monitor mode. That will display peak boost. If the target boost values are set to .70 and peak boost reads .70 kg/cm^2 (10psi), the PFC is actually doing its job. But your mechanical gauge may read 11psi (because of the sensor calibration issue), in which case you may mistakenly think something is messed up when it's just two measuring devices disagreeing with each other.

So at that point, if you want to see 10psi on your mechanical gauge you should reduce your target boost. Drop both the "primary" and "secondary" target boost values in .05 kg/cm^2 increments each time and see if that helps. Clear the peak boost value (press the up key to enter peak-hold mode and the right arrow key to clear) before each run.

Adjust duty values if necessary depending on whether you are overboosting or underboosting before or after transition. See https://www.rx7club.com/3rd-generation-specific-1993-2002-16/why-engine-so-damn-complicated-part-1-sequential-turbos-demystified-841821/ , scroll towards the bottom of post #9, the section titled "A possible method for setting PFC boost control duty."

So the rule is:

After a WOT pull (2nd or 3rd gear), check the peak boost using peak-hold mode. If the peak boost in the PFC mostly agrees with the target boost setting, you need to adjust the target boost setting if you are not happy with what you see on your mechanical gauge. That's to compensate for the MAP sensor calibration issue. If the peak boost is significantly off from the target value in the PFC, you need to adjust the duty cycles.

I feel like a fool for not finding this thread earlier. Doh! Awesome info here. I'm going to be late for work now... but totally worth it!

BTW, would you still suggest a tune by a competent tuner (either w/ experience using the Commander or Datalogit) for a car that is just running stock ports, stock twins, w/ downpipe and exhaust?

Thanks again. This info is long overdue and you delivered big-time!

--Note revised 11/22/2010 to correct/clarify a few points at Raymond's request. - Gracer7-rx7

The answer to the question is that it depends on the car, it depends on the tuner, and it depends what you are going to get from the tune.

I see a more limited value in the kind of professional tune where the tuner sits there at the dyno and essentially reproduces what I just suggested in this thread. That would be starting from the default map and then making minor timing adjustments while checking that the AFR under a WOT dyno pull is ok. As I've demonstrated, it doesn't take that long to mess with a few settings to reduce the chance of your car from blowing up, especially if you have a little knowledge and a wideband. You can add fuel and pull timing under an hour if you are comfortable attempting that yourself. Or you can go online and figure out what other people are doing for AFR's and timing on a given setup, reproduce that and cross your fingers.

I've especially seen local professionals at smaller shops who have more outward confidence than experience and knowledge. It's like taking your retirement fund to an investment manager with credentials on paper and yet he can't do any better than you could have done at a given level of investment risk. The PFC basemap really needs driveability tuning, especially cruising and idle AFR's. The default map is designed to get your car starting, idling, and driving while hopefully not causing engine damage to a car with a certain level of modifications. Tuning the low load AFR's is the kind of thing that takes a lot of time and changes with different setups. So if you take the car to a tuner, he's going to do one of 4 things:

1) He can mostly ignore driveability or spend only a small amount of time on it trying to do some custom tuning for AFR's under low load. I'd expect this especially from a tuner who isn't an Rx-7 and Power FC specialist, but rather runs an "Import Shop." If you think about it, they can't really charge the full hourly value for building a full custom driveability tune. It would cost you the customer too much. It's just an unprofitable road for a shop that's trying to keep the lights on.

2) He can go through a large library of his own maps and load one that matches your setup as closely as he can manage. The specialists are going to have this kind of library, and the more common your setup the better that map will work out-of-the-box. Nowhere near as much time is needed to make the individual car run better in this case because the work has been done beforehand in building the library of maps. I would expect this type of work from traveling tuners especially.

3) He can spend lots of time on the car for all these driveability aspects and lose money or barely break even on the amount of work put into it. I've seen local shops lose their shirts on this kind of work (not necessarily Rx-7's but other custom cars).

4) He can spend a decent amount of extra time on it if necessary, probably working off a map that he already had, and make a profit based on how much he's charging (tiered pricing plan) and whether you are paying him for other services as part of a package. I suspect a lot of the big guys do this.

There can be a lot of gray areas in the realm of tuning once you get past the standby rule of "don't run too much timing or too little fuel under boost, however you define 'too much' or 'too little."

Great thread :)

When adjusting the PIM volt menu, be sure to leave it on 'Normal,' when/if you accidentally move the cursor to Option1 the car will immediately run like shit :D

Also, keep in mind you're adding fuel based only on rpm, not boost. It's a temporary 'safety' bandaid but is not a proper tune because (among other things) it's not taking boost pressure/vacuum into account.

And you are correct, 1.0 kg/cm^2 does equal 14.22 psi.

on the idle learn, I never turned off the o2 feedback. my car learned the idle with it on. also if i turn it off, won't it be in open-loop?

wow...subscribed!!!

--revised 11/22/2010 per Raymond's request to clarify/correct certain points - Gracer7-rx7


If it runs ok, LEAVE IT ALONE! I can't emphasize this enough. It's so easy to make the car run worse before it runs better. The O2 feedback can cause problems on some cars, but I know of some that run fine with it on (especially those with an airpump still). The car will be open-loop without O2 feedback, but the closed loop system was designed to run with the airpump still installed. As I said in my last post, there can be a lot of gray areas in tuning where rules become guidelines or just get thrown out altogether. This isn't a comprehensive tuning guide, just a seat-of-the-pants kind of thing.

There is also boost-based compensation menu that relies on pressure sensor voltage. I have never used it personally (no point when you have a Datalogit and know how to use it) but in a previous post I provided some guidelines to consider if you wish to experiment, namely that 10psi seems to be over 3.5 volts on a stock MAP sensor calibration.

Tuning Cruising AFR's

Here's a little technique I developed a couple years ago when I was first messing around with the Commander and didn't have a Datalogit. My friend and I were heading to Atlanta for the NOPI Nationals show in his FD. He was running on the PFC basemap and we were getting horrid highway mileage, maybe 13mpg. AFR's were maybe in the 11's on that car.

First, make sure the engine is at operating temperature (over 80C) so that the PFC isn't applying warm-up enrichment. Under the Setting ---> INJ map, your low-load cruising range in vacuum is something like N6-N10 columns, P3-P8 rows. The car can run pretty lean here, anywhere from 14:1 - 16:1. I personally run in the mid 15's in most of those cells, although you can't expect to have every cell perfect nor should you try. Running lean here doesn't damage anything. Worst case scenario, the car will stumble from lack of fuel and you'll need to add some back in.

If you want to try and adjust this, don't do anything dangerous while driving. Get a friend to drive the car in a safe and controlled environment. Have him hold a steady engine load with constant pedal position or cruise control so that the car isn't moving in between cells too much. You are going to use the map trace function to figure out what cells you are in, then switch back to the INJ map to start leaning things out.

This process requires you to look back and forth between the Commander and the wideband and be quick with switching between menus. Once you get the hang of it, it's still tedious but you can do it efficiently. A Datalogit drastically cuts the amount of time needed to do this because you can modify a bunch of cells at once and have your map trace function overlaid on the INJ map so you're not flipping around.

https://www.rx7club.com/attachment.p...1&d=1243484112

https://www.rx7club.com/attachment.p...1&d=1243484112

https://www.rx7club.com/attachment.p...1&d=1243484112

I would lean cells out about 5 percentage points at a time when you first start messing with it. So if the original value was 1.00 , drop it to .95 .

While you could use this technique to adjust the idle cells, you have to be really careful. Idle AFR's can swing widely with changing engine conditions and changing ambient conditions, especially on hot starts. I would discourage all but the most adventurous from messing with the idle AFR too much (if you've got 850 primary's, forget it). Once it gets over 13:1 (no airpump) the idle can get unstable pretty quickly and you can have all sorts of surging or hunting if you don't have it already. If you want to do serious idle tuning, get a Datalogit and PM Chuck Westbrook about tuning notes (cewrx7r1). It's pretty advanced stuff.

Cruising AFR tuning--the Cheap Bastard Way

I haven't personally had to do this, but if you don't have a wideband, you can tune cruising AFR's only with the factory narrowband O2 sensor. Instead of reading a wideband display, you will be checking factory O2 sensor voltage through the Commander. Here's a graph I ganked off Google showing the voltage range of a narrowband sensor.


https://www.rx7club.com/attachment.p...1&d=1243484112

The voltage will fluctuate, but you want to aim for a range between .6 and .2 volts.

https://www.rx7club.com/attachment.p...1&d=1243484112

One last thing. If you end up making the car drive like crap and you can't figure it out, you can either 1) reset the Power FC and start everything all over again 2) just call a professional. If at any point you don't feel you are up to adjusting the PFC, get a professional. When in doubt, get a professional. I take no responsibility for anything you do with your PFC!

mods,

attached is a corrected graph for above. the axis labels were a bit misleading. you can delete this post after making a correction if you want to. Thanks.

https://www.rx7club.com/attachment.p...1&d=1243519864

Same here Im keeping up with this one .Thanks for some much needed help:icon_tup:

I like your replies and really admire your honesty/bluntness about paying a tuner vs. doing it yourself. I hate to pay for something I know that I'm capable of, but in the end I might just pay someone since I'm limited on free time these days and I don't own a wide-band. If I can find the time though and I can borrow a wide-band I still might be tackling this; all thanks to you!

Warm-up AFR Tuning

Tuning the AFR's after a cold start (under 80C) can be a very time-consuming process that will can take multiple sessions to get right. I usually prefer to use Commander for this because adjustments can be made quickly and you don't need to hassle with a Datalogit and laptop.

This is a more advanced tuning process. Always dial in the AFR's at operating temperature before you attempt to tune warm-up fuel correction. Under some conditions, if your car has insufficient warm-up enrichment it will not idle! This isn't a problem on the default map which is plenty rich. But I've said it before and I'll say it again, it's easy to make your car run worse before it runs better. So be careful

First there is the matter of warm idle AFR tuning. On less modded setups (stock primary injectors) mostly involves adjusting the INJ map in the idle cells found in the map watch feature. I haven't talked about warm idle AFR tuning too much because I am reluctant to encourage novices to attack something as tricky and time consuming armed only with a Commander and this writeup of limited scope. But you need to expect the idle AFR to fluctuate up to half a point of AFR, so maybe from 12.5:1 - 13.0:1 just in normal operation. When the idle AFR gets leaner than 13:1, you increase the chances of hunting and surging. Again, be careful.

With all that out of the way, I'll begin by saying that you may find a car without a cat will be a little smokey (fuel smoke) after initial startup. While this may not be avoidable 100% of the time, you can try to ameliorate it by adjusting the water temperature correction to lean out the AFR. In my experience the car can also tend to run richer than really needed while you are driving it easy during warm up. During warm up IMO there is really no point in running 11:1 AFR's in a cruising range where you would normally be running 14's or 15's. It can be in the 13's or whatever you want it to be, just don't give it much throttle or boost when cold.

https://www.rx7club.com/attachment.p...1&d=1243747650

There are two sets of warmup correction values, one for low load (idle mostly) and the other for moderate boost levels. The Power FC is going to interpolate between the temperature breakpoints and interpolate between the two correction values based on whatever the manifold pressure is. A higher number means a greater amount of fuel is added on top of what the normal fuel calculation would be. The two reference values in that pic are me doing a rough conversion of the pressure coordinates given in the datalogit (PIM 4864 for low load and PIM 14848 for higher load).

When I actually tune this, I start the car up and look at the water temperature in the "monitor" screen. Then I try to find the nearest temperature breakpoint and just fiddle with the values at little bit at a time. The car will keep warming up and you will have to play with the whole map. On another session you can start the car up and immediately go driving and start fiddling with the higher load correction numbers. The best thing I can tell you to do is just play with the settings until you are happy with the AFR's that you see, mindful of the fact that ambient conditions change throughout the year and the AFR always fluctuates within a certain range.

Here's another narrowband response plot that may help. Besides really high NOx (which is bad) there's nothing that says an engine can't happily run 16+:1 at low load cruise:

http://img.villagephotos.com/p/2004-...rrowbando2.JPG

I wanted to add a section on leaning your car out for an emissions test, although I've never personally had to do this (don't have sniffer tests here anymore). You should have O2 feedback turned on, and your airpump installed and working. You can go into the diagnostic screen on the PFC and temporarily lean your AFR's out across the board. If you have 850 primaries this may not work so well.

https://www.rx7club.com/attachment.p...1&d=1247773177

These changes will go away once you turn the car off. Unless you have the factory precat installed, ideally you would want to drive the car hard to heat the cat up, then quickly lean it out with this diagnostic mode before it's pulled into the station.

Just don't boost the car after you lean it out (unless you reset the changes made here). Having a wideband would help when you are messing with it. If your ACV is installed and working right then your AFRs should be very lean at idle because the ACV directs air pump air in order to dilute the exhaust right as it exits the exhaust ports.

Advanced Idle Troubleshooting - Fast Idle Cam

I'm going to add in some more stuff about getting your car to idle right after you've performed the baseline TB adjustment procedure mentioned earlier. This first little article is about checking your fast idle system (if still equipped).

Here's what you can do to see if the fast idle cam is affecting warm idle speed (it shouldn't). With the engine cold, bring your Commander into the engine bay. Go to etc.-->sensor/sw check. note the VTA1 and VTA2 values. Now rotate the fast idle cam with your finger. The VTA values should drop, especially VTA2 which is your narrow range sensor that is designed to detect throttle angle at idle. Return the fast idle cam to its normal position.

Now warm the engine up (get it to 82 C or so) and cut it off (you don't have to cut it off but it may make it easier to work back there). Look at your VTA values--they should be lower than before. Perform the same cam rotation test. The VTA values should NOT change as you rotate the cam away from its resting position on the now-extended rod. If they do change (more than say .01 VTA2 volts), your fast idle cam has not fully rotated away, most likely due to adjustment of the cam adjust screw:

https://www.rx7club.com/attachment.p...1&d=1250832601

adjust the fast idle cam screw so that, with the engine completely warm, VTA voltages do not change as you physically rotate the cam. Does that make sense? You are just trying to make sure the fast idle system isn't making the throttle plates stick open once the car is at operating temp. The way it works is that the hot coolant makes the rod extend, which rotates the cam. That screw mostly sets the angle of the cam when the rod is fully extended.

I'm not sure how hard it is to get to that screw, I've only adjusted a fast idle cam screw on a 2nd gen turbo throttlebody which has the fast idle cam in a different orientation.

Awesome info. I'm gonna go print all that out, put it in a binder and use it as a back up :)

D

Just wanted to give a little trick i learned when adjusting the fast idle cam. depending on what oil filter you have the adjustment screw can be very hard to get to with a screwdriver. one trick I learned while fixing my idle is that the adjustment screw isn't locked with a nut like the other throttle plate screws are,so its pretty easy to turn, if it seems tough, just spray it with some wd-40 or carb cleaner to remove some of the rust, dust, etc and then us the tab from a coke can to turn the screw while you hold the cam open a little bit to relieve the friction from the waxrod. It worked like a champ for me!

This is the best thread ever. Thanks guys as this is really helpful info.... specially for newbies like me.

Advanced Idle Troubleshooting - Idle IG control

Based on your settings in the etc. --> function select menu, the PFC controls idle with the following logic:

1. O2 feedback and Idle IG Control ON (default): PFC controls idle fuel based on factory O2 sensor signal, PFC uses closed loop idle control. Neither fuel nor timing are directly adjustable by the user.

2. O2 feedback OFF, Idle IG control ON: User can control fuel, closed loop fuel is disabled completely, PFC varies idle timing in an effort to reach target idle speeds. Turning off O2 feedback is usually necessary on cars without an airpump.

3. O2 feedback OFF, Idle IG control OFF: Ignition timing is fixed at

-5 L, -20 T for no load idle, same as the FC and FD service manual spec and same as the yellow and red timing marks on the FC crank pulley

4 L, -6 T for electrical load idle. electrical load is triggered by either engaging the fans (fan output) or by the PFC receiving a signal from the electrical load detection computer (ELD input)

I don't know the fixed A/C ignition timing values off the top of my head.

The ignition timing is completely static for the three idle conditions (no load, fans or electrical load applied, A/C load). The PFC manual specifically states that turning off Idle IG control was intended for checking ignition timing with a timing light. On an FD that's not normally necessary, although it is on an FC because the crank angle sensor is installed like a distributor.

4. O2 feedback OFF, Idle IG control OFF, idle speeds set to 0. This is what many refer to as "manual idle control," and can only be enabled with a Datalogit. The user has complete control over idle ignition timing but the ISC valve no longer functions for A/C or E/L idle up or improved cold starting. There are advantages and disadvantages to this configuration, and all I will say is that using this depends on your setup and your personal preferences. PM Chuck Westbrook (cewrx7r1) about tuning notes, I won't go into it much because this thread is all about Commander tuning.


With an ISC installed and no airpump, I personally prefer to have O2 feedback OFF and Idle IG control ON. Now let's discuss steady state (not decelerating or free revving) idle speed control before we get to the very thorny issue of deceleration idle problems.

With Idle IG control ON, the PFC calculates ignition timing in this basic way:

base idle ignition timing (a separate value for no load, electrical load, or A/C) + closed loop correction factor

The closed loop correction factor is somehow calculated by measuring how far the current speed differs from its target, or the "error" term for those of you with any knowledge of closed loop jargon. With idle IG control on, the PFC will vary the ignition timing within some range of authority in order to stabilize engine vacuum and get closer to the target idle speed. The PFC will also add more idle air through the ISC valve when electrical or A/C load are applied, even if they have the exact same target idle speeds.

https://www.rx7club.com/attachment.p...1&d=1255544038

https://www.rx7club.com/attachment.p...1&d=1255544038

The PFC will advance ignition timing to raise the idle speed or retard ignition timing to lower the idle speed. While it is not possible to directly set idle ignition timing without full manual idle control, a little fiddling with the idle settings will accomplish the same goal. As counterintuitive as it may seem, my current idle speeds are:

1000rpm no load
950 rpm E/L
950 rpm A/C (no A/C is installed on my 2nd gen but I have tuned A/C idle before)

Yet with my throttlebody adjustments, I actually idle at around 900rpm with no load or electrical load applied. Basically I adjusted the idle through the TB down (in order to prevent idle sticking on decel) then effectively raised the base idle speed through indirectly manipulating the PFC's ignition timing logic. Note that this is on an engine with large intake and exhaust ports that pulls very little vacuum for a non-bridge engine. The work-arounds and manipulations I have done are probably not necessary on most people's setups. You need to remember that The PFC and the throttlebody adjustment all work together to control idle speed under various driving conditions.

Advanced Idle Troubleshooting -- The Dreaded Sticking/Surging Idle

This section will focus on a troubleshooting process. It's not going to just give you some settings that you can mindlessly enter into your PFC you can go off on your merry way--if only it were that simple. Fixing these deceleration idle problems could take as little as 5 minutes (just a quick change in the PFC) or as much as 10 hours (testing all sorts of combinations of PFC settings and TB adjustments).

For those of you with an ISC valve installed, this is one of the most common and frustrating problems with the Power FC. I have covered this in another thread: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/new-pfc-idle-sticking-problem-solving-strategy-isc-installed-853278/ but I want to update, condense, and simplify the information here. You should have already checked the obvious stuff (throttle cable etc), you should have tried adjusting the air adjusting screw under the TB elbow, and you should have set up everything else properly in the PFC (O2 feedback for example).

Now here are the typical symptoms: You start the car up, and properly perform the idle learning procedure. Everything idles fine and the car is at operating temperature. Then you go drive the car. Eventually you get to a stop sign or a traffic light and one of these three things may happen:

1. The idle sticks at 1200-1500rpm and just stays there.

2. The idle sticks at 1200-1500rpm and eventually drops.

3. The idle drops too fast, the engine stumbles, then surges as the PFC struggles to keep it alive. It may just surge once and settle down, or may be hunting up and down for a while, making you look like a complete idiot to anyone else in traffic.

You may not be able to make the car idle like it did brand new off the showroom floor, but there are a number of strategies you can employ to mitigate those problems. First, here's a little background on the idle speed control system.

Sources of Idle Air for the FD

1. the throttle plate opening angle. This is controlled by the fast idle cam, which I've already covered. It's also controlled by the throttle adjust screw, which acts as a stopped for the primary throttle plates. Finally, extra tension in the the throttle and cruise cables can open the throttle plate. Both should have 1-2mm of freeplay)

2. a vacuum leak

3. air bypassing the throttle plates, controlled by the air adjust screw

4. duty controlled bypass air from the ISC valve, controlled by PFC target idle speed (and the learning process) and the fuel cut settings, which indirectly determine ISC behavior on decel.

On deceleration, the dashpot function of the idle control system controls the amount of air entering the engine as you release the accelerator pedal. There are two components to the dashpot function:

1. an electronic dashpot based on how much air enters the engine through the ISC valve.

2. an actual damper on the throttlebody which slows the closing of the throttle plates

The PFC gives us somewhat crude control over the electronic dashpot function (other standalones like the AEM EMS are more adjustable but also more complicated). Adjusting the PFC can often mitigate the problem to the point that the car drives a lot better and thus TB dashpot adjustment would be unnecessary.

Dashpot function--Electronic

The PFC controls the ISC valve dashpot function based on the target idle speed and especially the target fuel cut recovery speeds (we'll call them "fuel cut" or "F/C" settings). The fuel cut recovery speeds are here:

https://www.rx7club.com/attachment.p...1&d=1248301334

When you let off the gas, the fuel injectors stop firing. The F/C settings control two things:

1. They control the rpm at which the fuel injectors come back on line after deceleration. So if you come to a stop light and push the clutch in, the mixture will go super lean until the rpms drop near this setting.

2. They indirectly control how much air is supplied by the ISC during deceleration and how long it will be supplied. I wish I could give some breakdown of the ISC control logic here, but I just don't know exactly and neither does anybody else. I will say this: different idle speed settings and ambient conditions seem to have some effect on how the PFC determines the amount of air supplied for the dashpot function. Different clutches/flywheels, and different adjustments of the TB can all make a difference in what kind of settings may be required. You just have to fiddle with the thing.

Here are the two fundamental rules of the fuel cut settings.

The higher the F/C rpm settings, the more air will be supplied as engine rpms drop. Higher F/C settings will hopefully help address stumbling and subsequent surging. If you raise the F/C speeds too high, you may get a sticking idle.

The lower the F/C rpm settings, the less air will be supplied as engine rpms drop. Lower F/C settings should hopefully help address many instances of a sticking idle. Note that the F/C rpm settings must be at least 100 rpm higher than the target idle speeds. If you lower the F/C speeds too much, you may experience stumbling, surging, or stalling.

An example of Decel Idle Troubleshooting With the PFC Fuel Cut Settings

1. Park the car with the engine running, in a place that will tolerate you revving the engine. Start by setting all your F/C settings to the same value. In the end they don't all have to be the same, but again this is a basic approach to start with. Here's an example.

F/C A.E. 1200
F/C E/L 1200
F/C A/C 1200

Rev the car multiple times. Give it some small throttle movements and see what happens as you let off the gas. Give it some larger throttle movements and higher revs.

If you notice stumbling, raise all the F/C speeds and continue to test with free revving. Try it in 50rpm increments at first, and then you may have to make 20 or 10rpm changes. The PFC can be very sensitive. Remember, if you over compensate you will have the opposite problem (sticking idle).

If you notice the idle hanging up for a significant period of time, lower all the F/C speeds and continue to test with free revving. As you let off the gas, you want the rpms to drop to maybe 1200 rpm and then slowly fall. Try making changes in 50rpm increments at first, and then you may have to make 20 or 10rpm changes. The PFC can be very sensitive. Remember, if you over compensate you will have the opposite problem (stumbles, surges, stalling). This is something you have to tune by 'feel'. Later on you may have to adjust the dashpot on the throttlebody to improve this further, which I am still going to cover. Hopefully at this point you have made some kind of improvement in the way the ISC behaves during free revving.

Now take the car out for some city driving. As you slow for a stop sign, pop the clutch in while the vehicle is still rolling. On many cars the rpms should stay anywhere from 1000-1200 rpms until the vehicle comes to a complete stop. The PFC is designed to raise the idle speed if the vehicle is moving, in order the prevent stalling. Unfortunately you don't have direct control over this. Lowering the fuel cut speeds will reduce this behavior, but again you can overcompensate and compromise idle stability.

If you come to a complete stop at a traffic light with the clutch in, and the idle takes a very long time to drop down near the target speed, you can adjust the PFC fuel cut settings down further. But you may actually have to adjust the mechanical dashpot on the throttlebody for further improvement.

Dashpot function--Throttlebody

I'm going to be more succinct in this section, as you are using the same basic tuning principles as adjusting the PFC F/C settings. The dashpot is this plunger looking thing that slows the closing of the throttle plates.

https://www.rx7club.com/attachment.p...1&d=1260651113

https://www.rx7club.com/attachment.p...1&d=1260651113

Increasing the plunger's contact with the throttle has a lot of the same effects as raising the fuel cut speeds in the PFC. My car has a lightish flywheel and a sprung 6 puck clutch. I found that dashpot adjustments made the car a lot less prone to stalling in low speed parking lot maneuvers. The fuel cut settings couldn't completely cure that issue.

Decreasing the plunger's contact with the throttle has a lot of the same effects as lowering the fuel cut speeds in the PFC. Try that if the idle is taking too long to drop down as you decelerate no matter what adjustments you try in the PFC. Note that any adjustments to any part of the TB may necessitate further adjustment in to PFC settings. Your car may run worse before it runs better, but that's just the nature of driveability tuning.


I want to conclude by saying that you just need to keep fiddling until you're satisfied with the way the car drives. Use whatever combination of throttle body and PFC adjustments you need to make the car run the best. Focus on incremental improvements and don't expect the car to idle exactly like it did stock, especially if you have a 6 puck clutch and a 9 pound flywheel.

im going to make my PFC self set idle later never knew that was the way to do it.. good write up

Guys,

At the time of this writing the Power FC Commander manual is not available on the Apex'i website. They're not that hard to find from Google searches however.

Right now you can get the Commander manual here: http://bagpuss.swan.ac.uk/200sx/apex...der_manual.pdf . this link may eventually stop working but a search for "Power FC Commander Manual" works well enough

I've seen a few posts of people trying to diagnose problems by looking at the Power FC etc.-->Sensor/Sw check screen but not understanding what they are looking at. The description of each symbol is buried in the PFC manual and also buried in a less important section of this thread, so I'll post again here:


https://www.rx7club.com/attachment.p...1&d=1264916619

copied and pasted into my mountain of RX files. Thanks, ARGHX

nice...

Hard or Slow Starts

When you start removing idle control components or changing primary injectors you may find that the car takes longer to start, or won't start without using the accelerator pedal. This problem can often be improved with fuel and timing changes, although not necessarily eliminated.

Factors that affect cranking and starting:

-- Cranking speed, which is affected by battery voltage, the health of the starter, oil temperature, and oil viscosity

-- Cranking ignition timing, a function of the N1-P2, P9-P10 cells of the IGL and IGT maps and [unconfirmed] the ignition timing retard setting in the Datalogit

-- Fuel pressure

-- Throttle plate opening angle (VTA1 and VTA2 tps voltages), affected by the fast idle cam position (if still installed), the primary throttle plate adjust screw, and whether the accelerator pedal is being pressed

-- ISC valve duty cycle (if still installed), which will be 100% during cranking and then taper down

My latest testing indicates that even with Idle IG control on, the PFC will use the values from the IGL and IGT map until the engine is partially warmed up (about 60C ?). I will have to verify this, but it should also apply a warm up timing retard correction on top of the values in the maps. The warm up timing retard is 15 degrees by default until water temp reaches 60C. It is only adjustable with a Datalogit. A lot of tuners disable it, but there are times when it can be useful for smoothing out idle during warmup.

I recently figured out how to log ISC valve duty cycle with the Datalogit, shown as the bottom chart in the log below. Who would've thought that it's labeled with 3 question marks, parentheses, and the number 2? aka Advanced ??? (2). Here is a log of a street ported FD with stock sequential twins, 550/1300 injectors, and stock rats nest (ISC valve and fast idle cam). The FD is hot starting (which is normally not problematic on most healthy engines). The fast idle is not active and the accelerator pedal is not being pressed. Idle IG control is not on and idle speed is set to 850, so ignition timing is fixed during normal idle depending on electrical load etc.

https://www.rx7club.com/attachment.p...1&d=1270822444

Here are a few things to notice in this log. As I said, it is a hot start with coolant temperature heat soaking at 102C. Fast idle cam is down due to the temperature; if it were active, TPS voltage (VTA1 under Commander sensor/sw select) would be closer to 1 volt and narrow range TPS voltage (VTA2) would likely be over 1 volt. This is because the fast idle cam is the same as you hitting the gas pedal a little bit during cranking.

In this log the cranking speed is around 180rpm which is a little slow, but the battery was a bit discharged on this car. The four yellow cells in the IGL map trace the cells that the PFC is falling into when determining ignition timing during cranking . On default PFC calibrations there is a 15 degree ignition retard value for water temps below 60 C. I believe applies to cranking ignition timing as well, but I don't have a log which verifies that.

Cranking fuel injection, which is labeled here as InjFrPR (Advance InjFrPr, only loggable with a Datalogit), is initially at 13.56 msec and then tapers down. The 80C value for cranking fuel is 12 msec by default, so there must be some unseen correction added in there to increase the fuel. Cranking fuel is NOT determined by the INJ map, don't get confused.

The bottom chart is ISC valve duty. As soon as the engine begins to turn over, the ISC valve goes to full open (100%, labeled as 1000 in the PFC). As the engine fires up, engine speed rises over 2000rpm as a result of the ISC duty and the ignition timing values (throttle plate is closed the whole time). The ISC duty tapers down and idle speed falls.

Cranking Ignition Timing

To adjust cranking ignition timing, use the IGL and IGT screens:

https://www.rx7club.com/attachment.p...1&d=1243109296

Locate the matrix of N1-N2, P9-P10. Go to the IGL screen and try advancing the leading timing in increments of 5 degrees. So take the value that's in there and add 5 to it. Then try setting the corresponding trailing cell to the same value, resulting in a trailing split of zero degrees. So for example, if our IGL N1-P10 value is 6 degrees, set that to 11. Find the same cell in the IGT map and set it to 11 degrees as well. Do this for the whole cranking matrix. I wouldn't increase the leading cranking timing any more than 15 degrees over the original value.

Cranking Fuel

Note: some aftermarket FPR's don't hold fuel pressure as well when the engine is turned off. This in itself can make cold starts a little slower despite changes to the cranking fuel map.

https://www.rx7club.com/attachment.p...1&d=1270822444

The 50C and 80C settings rarely need to be changed, I wouldn't touch them. For the other temperatures you can try multiplying the cranking values by an adjustment percentage. For example, at 30C I may want to increase my cranking fuel by 10%. Say I had a value of 15 msec. I multiply by 1.10 for a final value of 16.5. I input this value (or whatever number closest that the PFC will allow). Then I apply the same percentage correction to the 10C, -10C, and -30C values. On most setups I would not add any more than 15% additional cold start cranking fuel. It might flood or (more likely) just not help any more.


So to review: Changing porting or injectors, removal of the ISC valve/fast idle, or changing the FPR may result in slower cranking times. Startability can be improved in many cases by advancing the timing (increase IGL values and set IGT value to match IGL) or increasing fuel through by a percentage. You probably won't need to adjust fuel and timing on setups with stock primary injectors and FPR that also retain the ISC valve and fast idle cam.

Just wanted to say thanks. This is great info.

Idle learn Procedure explained
 

Below is a partial log of an idle learn procedure being performed on a cold engine. This engine is running an ISC valve, fast idle system, PFC controlled idle with o2 feedback off. doing. The log is from over a year ago so I don't have the actual map I was running with it.

In this log the engine starts and up until 60C the idle control is in open loop. The PFC uses the timing values in the IGL and IGT maps. ISC duty is mostly fixed at 20%. The TPS voltage slowly drops as the hot coolant flows through the fast idle system. The voltage drop is somewhat exaggerated here due to the scaling I have chosen to illustrate it.

As the learning procedure begins, the PFC sets the leading and trailing timing to fixed values. It then varies the ISC duty as part of the learning process. Then the ISC duty is held fixed and the PFC tests ignition. At the very end of the log the idle speed has begun to stabilize as the engine fully warms up. I do not have a log of the electrical load and A/C portions of the learning procedure, but they may work in a similar way.

https://www.rx7club.com/attachment.p...1&d=1278619565

So does it matter whether the engine is cold or warm when performing the learning procedure? From what I've seen, I don't think so. I have tried it both ways and the PFC still tests ISC duty and timing.

Great post

WOW... yes.
great new Information here..

from my point of view I can give some additional informations, too.
This might be some information tuners could have made alot of money with...
but for you, its for free!:icon_tup:
A DAMN!Nice motorsports gift. :nod:

First of all some informations about my circumstances to understand why and how I did what I did.


As I bought my car, it already had 850 primaries installed.
I never had issues with the 850s in terms of driveability etc.

Now that I have my parts together to go for tuning (Datalogit, wideband, EGT, etc.) I started out improving every part of the map.
One of those is the idle.

Idle was High and rich (so smelly) all the time.
I had two problems with this fact:
1. my girlsfriend always talked bad about my smelly car :lol:
2. emmision tests here in germany are really really strict.


So I tried some things, already posted on this forum to lean it out:

- change lag-time to negative values
- lower idle rpm
- negative split.

As arghx showed on his posts, is the Idle controlled by the PFC:
- fuel wise if you turn on "O2 control"
- Ignition wise, if you turn on "IG control"

If you turn out both, it uses a fixed idle Ignition timing.

So yesterday I tried to set idle rpm to 0 to achieve the negative split on idle.
To my surprise. there wasn`t to much change. so it seemed that my idle (skrews) was set real nicely (mechanically).

then I started to tinker around with the timing. leading and trailling.

Here to sum up for you:

1. It is not that important which coil fires first (leading or trailling). there is one thing you should know.
the first one is responsible for the torque.

so I tested some things.
I used the standard PFC - fixed ignition times.
so leading = -5
trailling = -20

and then I switched those two.

The result was, the idle began to change in terms of sound, completely. It wasn´t that smooth as before but still accapteable.
Big difference was AFR: they changed from 12,7 to around 13,2

so i advanced trailling idle to around 0 to get a smoother more strong idle.
AFRs dropped a bit by doing so, but I was able to get a smooth idle.
then I realized that the great AFRs are because of the late firing of the leading plug which seems to work perfect as a waste ignition. (ignition all of the fuel rest)

by tinkering around some more with the idle adjust skrew and trailling timing, I was able to get a idle @ 700rpm @ 14AFR with 850 primaries which was also stable when I swiched on every electrical load by using those values:
(please keep in mind that it worked on my car. It might not work on yours!)

lag time: -0.26
timing:
http://i27.tinypic.com/2145sv7.jpg


when I´ve tested it under different conditions (it was 35°C yesterday [95°F])
I´ll post some logs.

Maybe I have to play with my idle adjust skrews some more to keep idle where I want it to be. But I think it is possible.


One more thing is startup of the engine.

Arghx is right.
When ISC isn´t working you probably will have the need to start up with throttle pushed in.
On my car it was able to start without, but alot worse then before!

Good luck to you all finding the perfect way.
I hope my information could help some people heaving problems with emission tests.
lean Idle is key on those tests...

regards

Marc

^ Good insight, albeit beyond the scope of this thread. Larger primaries create additional complications for having a good idle, and I tell people to only increase the size of the primary injectors if necessary.

Sorry for being dump but i am new to my power fc. If I follow your timing how to for the power fc.
I have. P16
(N7=2) (N8=3) (N9=4) (N10=4) (N11-4) (N12=5) (N13=5) (N14=5) (N15=4) (N16=5) (N17=6) (N18=9) (N19=13) (N20=14)

So if I fallow your intructions I shuld change it to this? P16
(N7= -2) (N8= -1) (N9= 0) (N10=0) (N11=0) (N12=1) (N13=1) (N14=1) (N15=0) (N16=1) (N17=2) (N18=5) (N19=9) (N20=10)


One othere thing please check out the pic. Do I just subtract from that number and leave the rest as is?

Yes

https://www.rx7club.com/attachment.p...3&d=1278707005

I'm not exactly sure what you mean by "the rest" but yes that number on the left is the number you are starting with, and the number on the right is the number you will be changing it to.

So for example in the picture provided. I leave the 8 number alone and subtract 4 from it which equals 4 and input the # 4 on the right and leave the 8 alone as is? What I mean by the rest is that if I hit left, right, up or down the numbers at the top also change. I think I saw that if I hit up it gives me a different number at the top then when I hit the right botton.

Yes

That's the same as moving around in the "map display mode" that you already went through (see step 1 in screenshot above). So if you plan on changing more than one cell in the P16 row, you could would hit the right key to move from say N7 to N8. You will see on the Commander that it will go from "Ne 7:" to "Ne 8:" . "Ne" is basically shorthand notation for engine speed. It's used in a lot of literature from Mazda and Toyota (one of the crank angle sensors is called an Ne sensor).

https://www.rx7club.com/attachment.p...1&d=1278817098

Thank you so much for the helps. Great thread

Acceleration Enrichment and Stumbling
 

One of the common problems on these engines, especially ones that are ported, is a stumble as the throttle opens. At one point I doubted this, but I now believe that the PFC delivers one major shot of fuel as the throttle opens. It is most likely "asynchronous," where the primary injectors fire at the same time and the normal injector firing order is ignored. Normally the injector firing order would go F primary, R primary, essentially synchronized with the top dead center signal ("G" signal) from the crank angle sensor. The tip-in fuel ignores the crank angle sensor. Just about every modern port injected gas engine does it that way, and Mazda actually describes it in an SAE paper for the series 5 FC3S Rx-7:

https://www.rx7club.com/attachment.p...1&d=1281651956

The Power FC has two main tables for this "accelerator pump" system (like on a carb) which is supposed to prevent/reduce stumbles as the throttle opens. The first one is the "Acceleration Enrichment" table, accessible in the Commander:

https://www.rx7club.com/attachment.p...1&d=1281651383

"Accelerate injector" is a max amount of injector pulsewidth that can be added at a given rpm, and I assume it interpolates between the rpm breakpoints. The middle column sets the max allowable pulsewidth for this extra shot of fuel at a given rpm. From what I've seen the rightmost "decay" setting has to do with how the fuel tapers off after that initial shot. The setting isn't very important and is best left alone. Playing around with that rightmost column will most likely just hurt your fuel economy in my experience.

So in the Commander we can set the max allowable fuel for the "accelerator pump" in the PFC. But what if you are only moving the throttle open a little bit? If you need very fine adjustment of this type of fueling you will need a Datalogit unfortunately. The Inj vs Accel TPS1 table determines what % of this max value (Accelerate injector "amount") will actually be delivered:

https://www.rx7club.com/attachment.p...1&d=1281651956

That is the factory table (viewed in the latest 2.128 FC-Edit software). On the left is the rate of change of TPS voltage (the speed at which the throttle is opening), based on change of voltage over time. On the right appears to be a multiplier of the "amount" (middle column) of the PFC Accelerate Injector/Acceleration Enrichment table. Basically the faster you stab the throttle, the more additional fuel (from the Accelerate Injector table) will be injected. This Datalogit log illustrates how these settings come into play:

https://www.rx7club.com/attachment.p...1&d=1280927688

As the throttle opens quickly (top red line), the PFC calculates the total amount of fuel (blue red line) it could inject based on rpm (Accelerate Injector table). Then it uses the INJ vs Accel TPS1 table to figure out what % of that maximum fuel to use based on the rate of change of TPS voltage. Finally, the "decay" value is used to taper off the fuel after the initial shot.

For those of you who don't want to get deep into tuning your own car, you could attempt to increase the values in the middle column of the "Accelerate Injector" table in the commander. It might help reduce stumbling a little, or it might just hurt your fuel economy. Most people will try to increase the millisecond values in this table by some fixed percentage, say 10%.

Overboost Fuel Cut with External Boost Controllers
 

Note: revised 11/22/2010 to correct/clarify certain points per Raymond's request by Gracer7-rx7

If you are using an external boost controller, you must adjust the Power FC overboost fuel cut. You have two options:

-- You can disable the overboost fuel cut entirely. The main advantage of this choice is that you can very quickly raise boost with your separate boost controller without being concerned about the Power FC interfering. Without any "last resort" overboost protection you could blow your motor if boost control fails. This overboost fuel cut isn't the only way to protect the motor in the event of a boost control failure, but it is the simplest to implement. Now to effectively disable the overboost fuel cut, go into the boost control screen on the Commander:

https://www.rx7club.com/attachment.p...1&d=1287170228

Select option 1 and adjust the boost setting to 2.00 kg/cm^2. So you want option 1 to read

Pr 2.00
Sc 2.00

the duty % settings don't matter because you are using a separate controller.


-- You can set an overboost fuel cut relative to your intended boost level. So if/when you raise the boost on your external controller you will probably need to raise the fuel cut in the PFC. There are two boost/fuel cut settings allowed in the PFC, so you could have option 1 be your low boost fuel cut setting and option 2 be your high boost fuel cut setting.

Configuring Overboost Fuel Cut -- Stock MAP Sensor With Default Calibration

https://www.rx7club.com/attachment.p...1&d=1287169874


The PFC instructions mention that overboost fuel cut occurs .25 kg/cm^2 higher than the boost setting in the Commander. My own testing says it can sometimes kick in at a little less boost than that, maybe .22 kg/cm^2 higher than the target boost. This section will show you how to set up the boost settings correctly for overboost fuel cut. Many/most people reading this guide are running the stock MAP sensor with the Apex'i default calibration. The default MAP sensor calibration reads boost slightly low so I have added an additional step to account for this.

1) Figure out what you want your fuel cut to be in psi and then convert to kg/cm^2. One guideline to follow is to set fuel cut about 2psi higher than your normal intended boost. So if I want to run 10psi I could set my fuel cut to 12psi.

To convert 12psi to kg/cm^2, divide it by 14.22 and then round up. 12 / 14.22 = .84 kg/cm^2, then round up to .85 kg/cm^2 .

2) Subtract .05 kg/cm^2 from the value in step 1. This is a rough compensation for the fact that the default MAP sensor calibration reads low. .85 kg/cm^2 - .05 kg/cm^2 = .80 kg/cm^2 . You will skip step 2 if you are not using the stock MAP sensor with default calibration.

3. Subtract .25 kg/cm^2 from the value you just calculated to get the final boost setting you will be using. So .80 kg/cm^2 - .25 kg/cm^2 = .55 kg/cm^2

4. Go to the boost control screen in your commander. Select the option you want to use, and set Pr and Sc boost setting to that final value you just calculated. So in this case if you wanted to use option 1 with a ~12psi fuel cut, you would want your setting to be:

Pr .55
Sc .55

This is a guideline value. Decreasing this number will make the fuel cut kick in sooner, while increasing this number will allow more overboosting before the fuel cut kicks in. You could also set option 2 to higher values, and then switch to it when you raise the boost on your external controller.

Configuring Overboost Fuel Cut -- other MAP sensor/calibration

If you have recalibrated the factory sensor or you are using some other MAP sensor such as a GM 3 bar, the calibration should read more accurately. Setting up the fuel cut is the same basic process, we are just going to skip step 2 above. So for a ~12psi fuel cut:

12 psi / 14.22 = .843 --> .85 kg/cm^2 . Subtract .25 kg/cm^2 and you get a setting of .60 kg/cm^2 . So set your boost control to Pr .60 Sc .60 and you're done.

Whenever I read one of your posts Arghx I feel like my brain is on a treadmill or something.

Great info, and great ability at communicating it.

Okay I went ahead and changed my Ign Map to the older version using datalogit. If I understand it, it is a better map than the older version, correct?

Now I want to make my fuel maps safer, any tips?

I'm just want to be extra careful when doing this since I never dealt with this before.

I know the two maps you are referring to (from the first post of this thread). From what you've posted here I'm not clear on what you just did, but for now you should "undo" it. I think you should start searching in the PFC section and learn a little bit more about timing.

There is some discussion of this is in post # and post #4. But you're getting beyond the scope of this thread, as you are getting into more advanced Datalogit tuning. You can PM cewrx7r1 about the Datalogit tuning notes and tuning group.

At this point I think it would be better if you slowed down a little bit and learned more. Put the timing map(s) back to where they were before and learn how everything works before you make changes. I'm concerned you are going to make a mistake.

What I did was changed my 5.08 ignition map to the 2.01 map thinking it was the changes you commented on. I just realized what the changes are for the 5.08 map. I'm going now to change the ignition map to the original then retard the ignition like you posted. My car has all the bolts ons and I went ahead and increase my fuel to 110% on all RPMS.