I have a build as follows:
1987 RX-7 TII 94xxx km's
Rebuilt to OEM spec, OEM 2 pc seals, Hand fit OEM side seals, all new springs, seals and o'rings.
RB Rev TII Full exhaust
Greddy 720cc secondaries
Treperformance 255LPH pump (walbro rip off, Nice quality though)
Rtek 2.1 ECU w/palm
Innovate LM-2 wide band
Home brew TID
S5 TO4B V-trim Hybrid 360* thrust bearing Garrett rotating assembly .50a/r coldside housing
Synapse Synchronic BOV
K&N drop in oem filter
Crane cams HI-6 ignition box
Autometer ES boost and Pyrometer
Act Streetlight flywheel
Centerforce Clutch

When Sitting at idle car has afr's of 11.5 -12
Under light to no load 12-13
Under cruising power 14.7
Under Medium load no boost 14.7
Under light boost 12
Under Heavy boost 9.5-10 (6psi oem wastegate)

I have not been able to tune the idle correctly as the when initial set couple is enabled and variable resistor is changed the car tries to stall i have fudged it for the short term to idle and drive acceptably. Idle adjustment screw will only bring the idle to a meager 750MAX and as low as stalling no matter what position variable resistor is set at.

I am confident that there are no vacuum leaks are occurring as much care was taken in the build to assure no leaks. Not only that but I have removed upper intake and spent time tracing all remaining vacuuming lines and means of vacuum leaks just to be sure.

Car seems to drive quite acceptably under most conditions except under boost it hesitates and misses is quite disconserning.

I have set the TPS via instructions in Rtek 2.1 and seems to be in good condition.
I have checked the fuel pump resistor relay, and fuel pump voltages 8.90 when resistor relay active 11.6-11.8 full power.

Checked timing at 750 RPM (as best i could 700-750rpm) and the timing was bang on.

Checked the bac valve for cleanliness (it was spotless like the rest of intake)

Bac valve works great with air conditioning on car handles it fine even though it seems to have slightly weak idle.


Any help would be greatly appreciated.
Thanks,
Keith

 

You're working within the limits of a stock FPR and a modified stock ECU. Those bigger fuel pumps tend to cause a richer idle by bumping up fuel pressure. That being said, you can still fiddle with the various idle adjustments and see if you can get improvements. On cars with standalones, a stock port motor can idle at least as lean as 13:1 (no airpump).

If you feel you have exhausted your current set of options, you may have to mess with the throttle stop screw for the primary TB butterflys. I would recommend this be done while the engine is running (fully hot), with initial set enabled. The screw is on the back of the TB (stock TB pictured here, turbo model):


(courtesy of a random pic I got off a thread here)

FSM diagram, stop screw in pink, everything else is related to thermowax adjustment



There is an FSM procedure for adjusting this screw, but it is IMO worthless. It's for a bone stock car pretty much. You just have to play with it to get the idle right.

Do you still have a top mount intercooler? If so, you will need to build a custom crossover pipe such as this out of home depot parts:


(courtesy NZConvertible, who hasn't posted on here in a long time)

This is going to be a tricky process, with a lot of stuff going on at once. With the engine running, try setting the initial set coupler. loosen the locknut on the adjuster screw. tighten the screw to open the throttle plates a bit--maybe 2 turns max. then you may have to adjust your TPS to keep it in spec. Check the voltage (not resistance) and make sure it is .75-1.0 volts with your foot off the gas pedal and the car fully warmed up. Then you can try adjusting the variable resistor to pull some fuel out of it. I would leave the BAC adjuster screw alone for now, although it may be another way to fine tune the amount of idle air if it comes down to that.

You're going to be jumping back and forth between these various forms of adjustment. This is the basic process you would use on a standalone to stabilize, except on a standalone you have to adjust timing as well. I have done it on FC's and FD's, it is a process that requires a lot of patience.

I like to idle at 850 on a modded car, especially with a lightweight flywheel, but your target idle speed is your choice. just make sure you keep your TPS in spec or things will start going crazy once you disable initial set. Under WOT you just need to pull more fuel out of the correction maps. Do not let it run richer than 11:1, certainly not at that low of a boost level.

 

if you have no air pump those numbers are about right. with the air pump the air pump air goesinta the exhaust ports, and the o2 sensor will read about 16:1, but the engine is still running about 12:1

 

I totally agree what to what arghx has to say but with that in mind i checked the primary throttle plate setting which has a accuracy range from .040thou-.070thou mine was about .050thou which is not really out of spec cause im stilling using stock boost pressure settings.
One other thing i should mention the Rtek 2.1 ECU wants me to to set the TPS to 20% to be within what it considers "Factory spec" and i have noticed with my multimeter that this is not the conventional 1ohm resistance usually reccomended for stock tps position. The datalogging program wont actually let you go ahead with its virtual variable resistance idle tuning process unless the stock tps is set to +20%, I dont quite understand the reasoning behind this maybe because the oem variable resistor is disabled? It is driving me quite insane as I have spent a large amount of time researching upgrades and doing clean installations only to have the same problems many other rotary owners suffer.

 

20% should be around 1 volt or so (5 volt sensor). that's why I said 1 volt, not 1 ohm. The resistance checks are really just for making sure the TPS is not bad (the TPS is a simple potentiometer), the voltage is what the ECU sees. It is the same on a Honda for example: the Civic FSM calls for a 20% throttle position (as logged through an OBD II scanner), which is right around 1 volt on the Civic TPS.


FSM page 4B-32 . I didn't just make that number up.

disregard the factory specs on primary throttle plate to bore clearance. that is for a factory engine, requiring the factory amount of idle air. Trust me on this. I have seen every FSM spec you are referring to. If the BAC adjuster won't work, you have to adjust the TB screws, whether they appear to be in spec or not. If the Rtek won't let you do the initial set, you still need to try that procedure, but with the car off. Loosen the locknut, tighten the stop screw down maybe a turn or two, and re tighten the locknut. Note that the act of tightening it will probably move the screw at least a bit tighter. Set the TPS to 1 volt. Set the initial set (do you have to have the car running?) and start the car, and then play with the variable resistor function and possibly the BAC adjuster again.

On a T2 with all factory idle control systems present, think of your total idle air as a function of this basic equation:


hole inside the TB bore (which is cast into the TB, look at it and you'll see what I mean) + primary butterfly opening angle (which is a function of fast idle cam position and the stop screw) + BAC valve adjuster screw setting + BAC duty cycle + vacuum leaks


change any one of those factors and you get more idle air, which then may require compensatory fuel adjustments.


training manual page 4-53

my feeling is that, when you adjust the screw on the BAC, you are tightening the spring on the left part of the diagram. Thus for any given BAC duty cycle, more air would allowed in. But clearly there are limits to that. If you look at where the BAC valve mounts to the UIM, it is just two tiny holes that lead to the primary runners. Only so much bypass air can get in through there, limited further by the characteristics of the BAC system itself.

 

20% on the rtek is what the ECU wants to see regardless of anything else. Set it to there and it's good

 

my car likes to idle around 12.2 afr as well, no biggy.

 

Im not adjusting the screw that actually dictates how the BAC valve functions, im turning the idle air screw that is located on the BAC. BTW I have a series 4 so if and when I make that TMIC delete piece to work on TB do I need to include the two air fittings on the back of the TMIC that connect to TB/BAC valve?? I totally understand what you are saying about the total air being let into the engine dictates idle and it is a fine combination of multiple adjustments that make a good idle, what im more worried about is the stumbling/hesitation I get when under medium heavy load with boost (rediculous rich afr's causing issues?) and how much fuel I'm wasting at idle, my eyes burn if you stand behind the car at idle for any amount of time lol. I should mention that I can work the initial set coupler and idle adjustment in rtek just the adjustment range is not large enough (ie I cant get it to idle much above 700) to actually acurately set the idle mixture via variable resistor, so in the meantime its pretty much wild guess at the best idle combination I could achieve via use of idle air screw on BAC and Rtek variable resistor feature.

Also why would the oem throttle plate setting be insufficient for tune? I haven't ported the car or messed with intake much other then the actual turbo/exhaust and basic emissions removal. Theoretically my car should act exactly as stock other then when im under boost and even still it would only differ if I increase boost levels over oem.

I should also note that from oldschool mechanics techniques hints that my car can't be running too too rich being the fact that when I run my finger inside exhaust tip there is VERY little carbon, IE enough to get black on your finger but not enough the hide fingerprint.

The engine was a fresh rebuild (120 front/rear rotor before rebuild) with all oem parts (except FD corner seal springs, FD oil pressure regulator, 2pc new fd style oem apex seals) it has about 2500km on it now and has been running quite nicely other then these nuicances.

I will not be satisfied until shes running nice, nor will I feel safe pushing the hp boundaries via boost until these basic tuning issues are resolved.

 

when you remove the emissions, the car will idle low and rich. due to there being no air pump air in the exhaust. the air pump air in the exhaust does a bunch of things. without it the engine does not run as well, the ecu isnt as happy etc etc. opening the throttle plate a little more with the setscrew adds more air, but its more of a bandaid than a fix.

solution is either to run the airpump, or start tuning the ecu

hesitation up top could be several things, plugs, plug wire condition and routing matter.

actually i just noticed you're running 720's, unless you have it set to 550/720 in the map its going to be really super rich. you may have to pull a little fuel to get back to an AFR where it actually runs.

 

I have the ECU set to 550/720cc injectors. I am having my suspicions that it may be a few things that need to be upgrades, first off I'm going to get my oem secondary 550cc injectors cleaned and put them in place of oem 550cc primary's(original to car). I also am suspecting that the oem fuel pressure regulator is not keeping up with regulating demands of new pump, might buy a fuel pressure regulator and under hood fuel pressure gauge.

I have checked the resistance of plug wires all within spec, ignition system In my personal opinion is working awesome w/ or w/o the crane cams box installed. It does't really hesitate in the high rpms under high load that much it just stumbles pretty bad getting there it seems.

Does removing the ACV and air pump really mess with the idle and running of the car that much? Is it because its messing with the oxygen sensor readings relative to oem mapping because of the lack of airpump and ACV. By adjusting the throttle plate set screw can I compensate to some degree for this difference?

Noticed a few more things:
When looking at the readings coming from my rtek I noticed that my tps actually never reads 100% at WOT the most I could get it to read was 89% I can imagine this would be a large factor in my hesitation problems could it not? I visually checked throttle linkage actuation by hand and it it all working smoothly with full tps actuation at WOT.

 

I've got an FMIC on my car but I would say that you should incorporate those air hoses through some test pipe as well. a lot of the people who use the delete piece don't have a BAC valve.

lean it out to at least 11:1 and then get back to me. At that boost level a lot of people would run 12:1. the stock ignition would struggle to light a mixture as rich as you are running... misfiring is very common at 10.5:1 or richer. People detonate from mixtures that rich! Ask BDC, he blew a motor from misfire/detonation due to a pig rich mixture.

How exactly do you have your wideband hooked up? I've never set up the LM-2 (it's pretty new) but I've hooked up the LC-1, and you have to be careful with the grounding and make sure you calibrate it.

This is the right mentality. Too many people just want to have the fastest **** possible and skip out on basic driveability, then complain about it later.


an overloaded FPR is like an overloaded wastegate--the result is a spike in pressure. a spike in boost pressure often means a lean mixture (and detonation), a spike in fuel pressure means a rich mixture like you are experiencing, at the very least under idle.

It is well known that removing the ACV affects both observed idle mixture and the overall feedback system of the ECU. The ECU was designed to first and foremost meet emissions and driveability. What do you expect when you do something that is way outside of its design parameters? FD's are especially notorious for shitty idles when the airpump is removed, at least without tuning.

Most OEM TPS's I have seen on all sorts of cars have an operating range from 20%-80/90% "absolute" value, based on sensor voltage. In OBD II terminology, that would be called the "absolute" TPS % if you are datalogging with a scantool. Hondas are a great example of this. Their TPS ranges from 20%-80% or so according to FSM specs.

It is partly because:

1) on the low end of the voltage/% range, the throttle plates are never 100% closed. right at exactly 5 volts usually a sensor is considered to be messed up in some way. most 0-5v sensors max out below the full 5 volts.

2) a TPS is basically a potentiometer (resistance varies with position of the measuring device), and over time the sensor degrades, so the ECU needs to be able to work within a range of values. The "20%" absolute value can also be effectively normalized for ECU calculations, although it is not done so in this ECU. On an OBD II car, this would be reported on a scantool as "relative TPS," where an "absolute" value of 20% is normalized to 0%, and an absolute value of say 80% effectively becomes WOT. The absolute and relative % concepts were officially defined long after our stoneage ECU was developed, by SAE J1979 (OBD II loggable paramters list), but the same principle applies here.

I bought a brand new s4 TPS from Mazda. With the TPS adjusted to 1V (throttle closed), max voltage is about 4.7 . As the sensor degrades and internal resistance increases, you will find that a TPS adjusted to 1 Volt will hit a lower and lower max voltage, meaning a lower % read by the ECU. My old out-of-spec TPS, properly adjusted to 1 volt, read a max of 3.9 volts. Resistance was something like 8K ohms on that one if you did the resistance test that everybody does. Do you see now the relationship between TPS voltage, TPS resistance, and TPS % as read by the ECU?

The ECU is expected to work within a range of deterioration of the TPS. Once it gets out of that range, everything starts flaking out. The series 5 and series 6 cars are a bit more forgiving than the series 4.


Enough of my long-winded technical discussion. If you want to just try and get through this quick, skip the TMIC bypass pipe, pull the TMIC off and tighten down the stop screw about two turns. Put the TMIC back on, set the TPS to 20%, and try the idle adjustment procedure then. See if you can bump the idle up to 750-850, you might be able to further lean out the idle then. Otherwise if that doesn't work you will need an aftermarket FPR. I used to run at 11.5:1 AFR with an FD fuel pump on my nonturbo car, stock FPR. Under boost you need to lean it out to at least 11:1 and you may find it running a lot better.

 

The amount of good info on this thread is too damn high!

I don't care that it's a rise from the dead bump, this info is what I've been searching for and wondering about for over a week. Thanks to the guys who typed this out and made it available info - will be going after this issue of running rich tomorrow and this weekend.