I'm envious of your AIT's..not so much of your AFR's . Is your mid-range kind of sluggish running that rich? I know I could feel a significant difference when I upgraded to the 1000cc secondaries and was tuned for 720cc. My mid-range is worthless at the moment.

p.s. I have a vid of me spankin a stang in the first race but my mom can't hold a camera very well .

p.s.s 12v fuel pump pressure ripped the diaphragm in my pulsation dampener within a few miles. Leaked fuel all over engine bay and had to get towed home in front of the whole neighborhood (who came outside to watch). Damn rotaries ...banjo bolt on the way

 

the pressure is the same, b/c the Fuel pressure regulator is what determines the pressure. but i had the same kinda of mentaility when i first 12v'd mine. but it does FLOW alot more that extra flow is what made a probobally allready failing part, go belly up.

 

Yea, the midrange is a little sluggish, but it's getting better and I wouldn't call it sluggish really. I'm working on getting better gas mileage because the last tank I figured I was getting about 13mpg. Open loop works great bouncing between 14 & 15 afrs, but in closed loop seems to be a little rich 12's and 13's under vacuum.

Sux about your dampener, but hey it didn't catch fire!

I spanked on a VR6 jetta, and I was spinning all of second had to let off because the tail was walking out.

Attached is a 6 min log of some driving. .pdb renamed to .zip afr scaling 5V=20afr 0V=10afr (or is it the other way?)

Been DD'ing it for a few weeks now...

 

Still working on leaning it out. Still...

2nd gear pull, no boost. (not really a pull, but just accelerating, in the rain)



I've been pulling fuel, but man... seems like it doesn't get any leaner.

 

Post whoring continues...

So under vaccuum is it perfectly safe to shoot for 14-15 afrs throughout the RPM range? Can I go leaner? Should I stay richer on the upper rpms?

 

Solid 3rd gear pull. Felt real strong. Still rich in the lower-midrange... Going to be a nice week, I'm hoping to have it around 11.8-12.3's across the board by next Friday. Seems just after the secondaries come on, it pegs 10's then after 5k it's almost right. Did see IAT jump from 15*C to about 18.125*C

Is 12.5 too lean at 10psi? at 14psi shoot for 11's?

 

Most people would consider 12.5 as pushing it for 10psi, at least once you get over say 3000-3500rpm or so (although I doubt you could hit 10psi under 3000rpm). It sounds like you are just working out injector staging related stuff. Your IAT's at the elbow are low.

As for AFR's in vacuum, well remember that you are still going to be in closed loop for a lot of that.

 

My fuel correction maps bar graphs 8 and 10 psi.





Kinda wierd that my rich spots(10 AFRs) I'm at -(neg) values and the leaner higher RPM corrections I'm way positive and seeing ~11.8-12.5 AFRs at 10psi.

That being said I'm a little nervous about raising the boost with the amount of correction available... but its gotta be possible. I mean SilverFC88 did like 400 hp with 720x1000...

 

What you are seeing makes perfect sense when you look at your graphs and consider how the basic fuel calculation is performed (according to the Series 3 GSL-SE training manual page 4B-33).



Injection pulsewidth is proportional to airflow divided by rpm (before the Rtek boost-based corrections are applied). That's a pretty typical way of calculating fuel requirements on a Bosch L-Jetronic derived system (airflow-based load calculation). Now look at your rpm and airflow curves from your prior post. Divide your airflow and RPM at a few points and you will get an idea of why it wants to run leaner up top. Your airflow signal essentially flattens out at around 720 units at what looks like 4000rpm

airflow/RPM = 720/4000 = .18
at redline: 720/7000 = .102

So the ECU is probably calculating less fuel. On a newer car you would make MAF changes: either rescale the MAF, change out the MAF sensor altogether, or change the MAF housing. This would give you more accurate airflow measurement.

 

^ Very Interesting...

Thank you for that little peice of information and how the hell did you know where to find that? Maybe I need to read up more on the training manuals...

Question though, So if I continue to raise the boost will the AFM value increase with PSI? So at 12 Psi it might read 800 and at 14 psi it reads 900? And considering that at ~6600 @ 10psi I already have a fuel correction of +28. When I raise to 12 or 14psi will I have enough correction ( up to 40?? Or is it only 32?) to supply enough fuel?

I'm itching to turn it up.

 

What's confusing to me is that we don't know what exactly the AFM units are. Are they a total airflow value, like total airflow grams/whatever per second used on many other airflow based systems? Or is it a calculated airflow unit per intake stroke like other systems use?

Fuel and Emissions section of the little-known GSL-SE training manual. PM me if interested in this document. It's a lot of the same stuff as the more widely-available S4 manual though. The S3 is just more primitive in the way it controls the injectors, spark advance, and idle. There are two injectors and they fire at the same time (batch fired) as opposed to sequential fuel injection on the FC. The spark advance is controlled by a distributor and the ECU will cut vacuum to the advance diaphragm, just like on the 12A. The idle is controlled with a BAC valve, but the BAC valve is actually a primitive mechanical vacuum diaphragm valve rather than the duty controlled valve of S4 and later engines. How did I know where to find that specific part about the fuel injection calculation? I remember reading it before. I have a photographic memory for such things.

I'm not completely sure. My advice is that you test turn up the boost. Start doing part throttle pulls in 2nd gear, and then eventually wide open in 2nd. DO NOT adjust the boost controller and then go WOT in 3rd or 4th. That's very a quick way to break something. When I am dyno tuning a car I do 80% of my tuning in 2nd gear, as unconventional as that sounds. You can get much of the tuning done without continuously beating the **** out of the engine. Then I do 3rd and 4th gear pulls toward the end of the tuning session.

If you can't get it to run safely at part throttle in 2nd, then you shouldn't go WOT in 2nd. And if you can't get it to run safely at WOT in 2nd you shouldn't go put it in 3rd or 4th and romp on the gas. That's asking for it. It's the proverbial "walk before you run."

 

According to the code, it's lbs/min or kg/hr depending on what units you have it on. If you put the display on the number screen when logging, you will see the units.

 

so if it's kilograms/hour and you are at about 700 units, that's almost 26 lb/s min or 195 grams/sec. I don't trust the AFM reading under these types of conditions. We're using it in a way that it was clearly not designed for. That's the whole point of the boost-based fuel correction maps.

 

Yea, the Palm says 25.6 lbs/min... Still hitting 10AFRs. AAhh!!

 

According to the Basic Inj. Characteristics arghx posted I came up with this.

AFR's are good at 4500 and AFM maxed at 26.3lbs/min So that is my benchmark.

26.3\4500rpm = 0.00584
26.3\5000rpm = 0.00526
26.3\6000rpm = 0.00438
26.3\7000rpm = 0.00375

0.00526\0.00584 = 0.9 which means it's injecting 90% of what it was at 4500 at the same airflow. I should multiply my correction at 4500 by 1.1 to give my correction at 5000 assuming the airflow is the same.

0.00375\0.00584 = 0.64 which means it's injecting 64% of what it was at 4500 at the same airflow. I should multiply my correction at 4500 by 1.56 to give my correction at 7000 assuming the airflow is the same but, it is not. er' nevermind.

So am I tuning blind then?

Why is my AFM maxing at 720? and others are seeing above that? Suppose it has to do with the IAT? or??? Can I mod the AFM to read higher? Sounds dangerous. But so does 'hoping' that my correction can compensate for the increased boost/airflow, when the Airflow is maxed?...
Suppose the AIT isn't reading correclty or it is, maybe the signal can be manipulated to Increase the airflow reading?

I can't even verify that 26.3 lbs/min is what I'm flowing at and above 4500 at 10psi, now if I start upping the boost, I see trouble ahead...

 

Sounds like you have found a logical starting point.


In a word, yes. The fuel injection system is just too old/primitive. If this were an Rx-8, Evo, or STi you would change the diameter of the MAF sensor housing or do some other MAF modification. Then you would rescale the 2 dimensional map of voltage vs airflow. The Rtek boost-based airflow and timing adjustments are the primary work-arounds for the limitations of the airflow sensor.

If you want to experiment and don't mind hacking up wires, install some sort of resistor in-line for the AFM temperature sensor and see if that changes the airflow calculation. Another option would be to feed the elbow AIT sensor signal into the pin for the AFM temperature sensor. That would create a screwy reading but it would be something to observe.

Maybe the spring in the AFM can be modified or something. First thing to do is check whether the AFM voltage is maxed out. And yes modifying it does sound dangerous. But I'm not convinced it's necessary at this point.

Tell that to oldschool DSM owners who run 11's with just an SAFC or FD owners who cranked up the boost on stock ECU and injectors plus a rising rate fuel pressure regulator. These types of work-around solutions are hardly ideal but can perform better than you would expect at times.

See above. Installing a resistor into an AIT signal is a common trick when using an "uber-piggyback" (Emanage Ultimate etc) to eliminate an airflow meter on other cars.

I think you're worrying too much. Keep timing conservative, max out the fuel corrections, turn up the boost, and then slowly decrease the corrections until you lean it to the AFR you want. Worst case scenario you need bigger injectors (as a work-around for the correction limit) or you need to abandon the Rtek altogether.

Just don't turn up the boost controller and immediately go WOT in 3rd. Start with part throtlte in 2nd. If it's running lean in part throttle 2nd gear then there's no point in going WOT and risking something bad happening.

 

^ Food for thought indeed...

I will not be modifying the wiring or AFM or AIT sensor if I don't have to.

Traction is becoming a serious problem in second... I'm very happy with it. I'm just going to keep the boost at ~12#'s until I can verify at that I'm not leaning out on the top end at WOT. Fingers Crossed!

Wheel hop is taking a toll on my rearend though, This winter I will be doing some rear diff/subframe/suspension modifications to reduce neg camber and increase traction and hopefully eliminate wheel hop...

Thanks mang!

 

Well It seems to be maxed at 12 psi. I have the last row in the 12AFC index (13AFC index is 14psi and 11AFC index = 10psi) maxed and I'm still seeing +12AFR's (yikes) at 5600-7000rpm ish...

So, I can upgrade to 720 primaries and hopefully gain a little more out of it, or I can raise my fuel pressure slightly. Also my correction only goes to like +41.2 I think. If I remember correctly there has been an update to allow more correction?

From pocketlogger, "The S4T2 Fuel Correction Map is 14x14 with an adjustment range of +/- 37%" soo, hmm...

Another question, it seems that I'm lifting off of the throttle at the upper rpms(tps going from 90 to 88,86... although I'm pretty sure I'm not? WOT!) but could this cause the leaner afrs at the upper rpm range? The psi's and Airflow is still ~12 and 715 (26.3 lbs/min).

Any and All Suggestions are appreciated...

 

What is your base fuel pressure (without vacuum applied to the regulator) right now? Is it the factory 2.5bar (36psi)? Raise the pressure to 3 bar (43.5psi) and then try to adjust your variable resistor to lean out idle some. 3 bar is a pretty typical fuel pressure on normal fuel injected cars actually. For whatever reason Rx-7's run relatively low pressure from the factory. You've bypassed the fuel pump resistor and rewired everything right?

The whole throttle thing is probably just electrical noise, I wouldn't worry about it. fuel and timing are being calculated mostly by signals from your AFM and CAS

 

Fuel pressure around Idle is about 31psi.. Fuel Pressure is solid, I have bypassed the resistor and ran a 12GA wire from the main relay to the pump. Going to get a camera mount hooked up soon.

 

Little bit rich coming onto boost but leaner at the top. I richened it up a little on top after this. It was a cold morning.

 

At that boost level you may want to keep your AFR in the 11's at least. I like to assume that the engine could run .25 - .50 AFR leaner as conditions change. So build some kind of similar assumption into your tune so that you create a safety margin.

 

I hope some of this apply's here.

What do you guys reccomend loging when tuning? So does fuel index RPM an fuel index Boost tell you what cell needs to be adjusted, also does this rely on the map sensor, AFM or both? When tuning timing an fuel do you mainly go with AFR's or AFR's an EGT's, if just AFR's I may nix my EGT gauge an get a gauge for my lc-1. I'm also thinking my timing map would possibly need to be different from what a car would take in the bottom end due to my weight of 3440lbs, although the "safe map" that was posted earlier definately helped with low end already.

 

I recommend logging at least RPM, MAP(boost), MAF(airflow), Lead Timing, AFC boost index, WB02, TPS, AIT(intake temp), Inj DC, whatever else you want really.

Fuel index RPM = cell along rpm axis, Fuel Index Boost(AFC Boost index) = cell along boost axis

Tuning Timing can be risky if you want to be aggressive. I've been running the timing maps posted with no problems. Gains could be found probably, but I'm staying safe(I think) and just using something very close to the maps posted earlier in this thread.

 

Couple of questions:
What's is your [good] idle idle A/F ratio?
Is that with a working air pump?
What's your vacumm @ idle (inHg)/
thx