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Stock BPU Supra TT 1994 AEM V2 Accel Tables

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Hello,

I'm looking for some advice related to the accel tables in the AEM V2 ECU. I did the installation and calibration to my father in law supra tt and its run very well. I having some issues with a tip lean spot when hit the throttle slightly. As per what I have read apparently I need to modify the accel tables. I did some modifications but the problems persist. Is there anything that I'm missing here?

Besides, I having a random issue when stopping the car shut down. Basically whe I hit the cluth to stop in a light or stop sign the RPM decay completly. What table should I play to add contributions during decay accel?

I will appreciate any advice.

1. Regarding accel tables, that ECU is capable of good accel fueling but the it's a bit tricky to get things dialed in due to so many tables and options. There will be a few combinations of values that work well, and plenty of combinations that don't. Watch the logged values for dTPS (delta throttle, which is how quickly the throttle is being opened) and adjust those areas in the tables. It's also important to have the fuel injector phasing angles correct or reasonably close. If the accel fuel pulse contains the right amount of fuel but gets fired after the intake valve has already closed, it won't help the engine respond well. Here's a link to advice that a co-worker posted on the AEM forums: http://aemelectronics.com/?q=forum/aem-v2-lean-tip-and-stumbles-2jz

2. Stalling after decel could be a few different things. Idle feedback is the most likely cause, when you decelerate in gear and idle feedback becomes active, the RPM is usually higher than the Idle Target RPM so the feedback will go negative (less airflow). The engine speed will remain high while the engine is in gear (because the wheel speed has more control over engine RPM than the IAC airflow), so the feedback will continue to try removing airflow. When you press the clutch and the wheels are no longer connected to the engine, the IAC airflow is not enough to keep the engine idling at your target RPM. To check this is happening, I would disable idle feedback by setting the min & max limits to zero. If that helps, a more permanent solution without disabling feedback is to limit the amount of negative feedback the ECU can use, or adjust the Idle Max RPM lower so the feedback doesn't turn on when the engine is in gear. If disabling idle feedback doesn't help, it may be as simple as needing to clean up the fuel map if you are running through cells that weren't tuned well the first time.

Hope that helps,

SB

The problem is that the AEM V2 just doesn't have very modern controls and calculations. All the newest standalones, such as the AEM Infinity, can use a wall wetting (X-Tau, whatever you want to call it) function. Those are pretty easy to tune compared to older accel enrich functions. It basically models how much fuel is sticking to the walls during tip in and tip out, and you just adjust a couple parameters a little bit to get it more dialed in. http://aemelectronics.com/?q=comment/660#comment-660 . Wall wetting has been in stock ECUs for a long time.

Also, "injector phase angle" is another outdated control. The newer standalones let you specify an exact injection timing, either start of injector or end of injection. "Phase angle" is not an intuitive way to tune injection timing, as it doesn't correspond to an easy to understand physical angle. It's just easier for the programmers.

I'm not saying this to be negative. I'm explaining that the reason why you are having trouble tuning this is because, well, it's hard to tune this stuff. It's an uphill battle with these older control systems. There's a reason why the newer ones use some kind of simplified model based tuning (VE tuning, wall wetting, etc).

Thanks guys for the reply. I will do some testing again using your recommendations to see where ends up. I will update the thread as soon as I get some new information.

If you get stuck, there are quite a few tuners in the US who are very experienced using that ECU with that engine. It's unlikely they are going to share their work for free, but some may be willing to help with some basic drivability cleanup for reasonable prices.

I know this is an old thread. I'm tuning my own 95 Supra TT (stock block, 1000cc delphi injectors, pte 6766 turbo). I've been trying better understand the injector phasing. I too had the lean issue when blipping the throttle. A 5% throttle blip would send my afr from 14.7 at idle to 17.9. Messing with the accel tables wasn't really doing it for me.

I did see in the AEM notes that it recommended setting the "Injector Phase" to 1.5 teeth below the "Injection Synch" since the coils/injectors share the same teeth settings (INJ #1 and Coil#1 start at 4 teeth). So I did exactly that. My synched timing was 5.539 so I set the "Injector Phase" to 4. AEM had delivered it in their Supra Calibration file as 17.625 and the Injector Advance table was +100 across the board. Anyways I tried every advance setting afterwards +360 to -200. I found around -80 to -100 to be pretty good. It dropped the afr blip down to the high 15 afr instead of 17.9. From there I found that the same changes I had once tried to my accel tables seemed to have more of an effect now. I no longer run lean when I blip the throttle from idle.

My "Fuel Inj 1 open teeth" for -100 advance is 23. There are 24 teeth on the supra crank gear so that is 360/24 = 15 crank degrees per tooth. That would be 23*15 = 345 degrees when it starts spraying. I don't know where this exists on the 4 stroke chart or if it's skewed because of the "Injector Phase" changes I made. I don't fully grasp how AEM calculates this stuff or how their 1.5 Teeth less than "Injection Synch" works. If someone could help me better understand this I would really appreciate it. I've been about 10 searches pages deep on google and watched both the haltech and motec videos here on injector phasing.

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