Im curious if anyone has had the same issue that I currently have. So background, before my car was FI, the idle was PERFECT, car ran like a dream being maintained by Ben at Dairy Imports. After the AP-X (Angus) turbo kit was installed with FIC and 550cc injectors, had the car tuned and A/F is in range 11-12 at WOT. Here is the issue, cold and warmed up, the idle is not stable as it constantly bounces and exhaust is "popping". Also noticed a lot more soot on my left exhaust tip vs the right. Another bigger issue is when the car is fully warmed up (Idling for over 10 minutes), it drives fine minus the idling, BUT if I even touch the accelerator at all before its fully warmed up, the RPMs drop to zero and the car stalls and shuts off. If I attempt to drive it before letting it fully warm up, it jumps and surges randomly on its own, and if I hit WOT, RPMS drop like a rock and stalls/shuts off. Any ideas of the problem because im out of them! lol
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AP-X (Angus) Tubro NSX with Idling/stall issue
- Thread starter Italianx333
- Start date
who tuned the car?
PTuning did the dyno tune and street tune. I think I am going to take out my AEM FIC and send the unit to AEM to have them certify it isn't damaged, or has a bad map sensor as it shows symptoms of that. If it checks out, going to take it to Peter and Brad at ISP for a re-tune.
Car runs strong and pulls when its fully warm, but the idle/stall issue and gas smell is throwing it off.
One thing to consider is that it is very difficult to tune a FIC with a non OBD2 car. It is difficult due to the fact that you can't really monitor fuel trims on your car. Go with a AEM S2 standalone or Infinity . You are paying with a ticking time bomb with that FIC.
I think sending back your AEM FIC is a good place to start.
I don't know much about your car or your tune so what is your rear wheel horsepower?
I have a similar set up to you but I use the 440 injectors. If your horse power is around 400
It is likely that the 440 injectors will run better. You may also want to swap out all of your
Ignition coil's. BTW my FIC did have a failure and AEM replaced no questions 2 months past warranty.
7 years later still running like a champ!
I don't know much about your car or your tune so what is your rear wheel horsepower?
I have a similar set up to you but I use the 440 injectors. If your horse power is around 400
It is likely that the 440 injectors will run better. You may also want to swap out all of your
Ignition coil's. BTW my FIC did have a failure and AEM replaced no questions 2 months past warranty.
7 years later still running like a champ!
I am making 420 RWHP, 305tq @ 7psi on 93 pump. Wil sent me brand new updated 550cc injectors that we put in, ignition coils are brand new also, done with maintenance. My tuner even talked to Wil and they were both on same page with everyone, and my A/F is in the 11's at full throttle. Car runs like a champ when its fully warmed, its the cold issue. But I agree, I might send in my FIC and have them check it out to eliminate that.
In your original post you said:
"Another bigger issue is when the car is fully warmed up (Idling for over 10 minutes), it drives fine minus the idling, "
So, is idling performance always a problem or only a problem when the engine is not up to operating temperature? If idling is always a problem, then give some consideration to the fact that the problem may be related to the larger injectors. You only mentioned the Angus turbo kit, so I am assuming that the engine other wise has no modifications to the head, valves, size of the engine? If so, then the fuel delivery requirements at idle are pretty much the same as a stock engine. Because your injectors are much larger than on a stock engine, the injector pulse width at idle has to be much shorter than stock to deliver the same amount of fuel. Every conventional port injector that I have seen (which is not all of them) has a range of pulse widths over which the flow remains linear. At very short pulse widths the injectors typically enter a non linear flow regimen which means that you are typically getting less fuel than the ECU is asking for and engine operation becomes unstable. All the injectors that I have seen are linear above 2 msec pulse widths and a lot of them are linear down to 1 msec. Most of the injectors that I have seen enter a highly non linear region below 1 msec, although some vendors claim to provide linear operation below 1 msec. Kookoo4nsx is using 440 cc injectors which means that his injector pulse width is longer at idle than yours and may help to insure that his injectors are not operating in or at the edge of the non linear flow region which helps to insure stable idle performance.
I know zip about the AEM FIC. If you had a standalone EMS you would normally be able to record the injector pulse widths at idle. The injector manufacture should be able to provide you with the injector flow curves which define the linear operating area for the injector. If you know your idle pulse width and you have the injector flow curve, you should be able to tell whether you are in the linear operating region (good), at the edge of the linear operating region (iffy) or in the non linear region (bad). This would be a first step to determining if the injectors are the source of your problem. If it turns out that you are trying to run the injectors in a non linear region, you could try dropping the injector flow rate by dropping the fuel pressure; but, that also can change the other characteristics of the injector. Better off to try a smaller injector if you want to fix your idle problem.
The other injector characteristic that can drastically affect idle performance is the injector offset (some people call it opening delay) and the voltage sensitivity of the offset. Some injectors are super sensitive to the operating voltage and the offset / opening time increases a lot as the voltage drops. Confirm the correct injector offset and voltage sensitivity values for your injector and make sure that these are programmed correctly - assuming the AEM FIC allows you to enter these values. Wide open throttle tuning is less sensitive to correct injector offset and voltage correction; but, if you make significant changes to these values you may need to go back and check your wide open throttle tune.
You indicated what the AFR was at full throttle. That is not meaningful for idle performance. What are your idle AFRs and are they bouncing around a lot at idle? If the AFRs are unstable at idle that could be further indication that you may be attempting to run the injectors in or at the edge of the injector's non linear region.
"Another bigger issue is when the car is fully warmed up (Idling for over 10 minutes), it drives fine minus the idling, "
So, is idling performance always a problem or only a problem when the engine is not up to operating temperature? If idling is always a problem, then give some consideration to the fact that the problem may be related to the larger injectors. You only mentioned the Angus turbo kit, so I am assuming that the engine other wise has no modifications to the head, valves, size of the engine? If so, then the fuel delivery requirements at idle are pretty much the same as a stock engine. Because your injectors are much larger than on a stock engine, the injector pulse width at idle has to be much shorter than stock to deliver the same amount of fuel. Every conventional port injector that I have seen (which is not all of them) has a range of pulse widths over which the flow remains linear. At very short pulse widths the injectors typically enter a non linear flow regimen which means that you are typically getting less fuel than the ECU is asking for and engine operation becomes unstable. All the injectors that I have seen are linear above 2 msec pulse widths and a lot of them are linear down to 1 msec. Most of the injectors that I have seen enter a highly non linear region below 1 msec, although some vendors claim to provide linear operation below 1 msec. Kookoo4nsx is using 440 cc injectors which means that his injector pulse width is longer at idle than yours and may help to insure that his injectors are not operating in or at the edge of the non linear flow region which helps to insure stable idle performance.
I know zip about the AEM FIC. If you had a standalone EMS you would normally be able to record the injector pulse widths at idle. The injector manufacture should be able to provide you with the injector flow curves which define the linear operating area for the injector. If you know your idle pulse width and you have the injector flow curve, you should be able to tell whether you are in the linear operating region (good), at the edge of the linear operating region (iffy) or in the non linear region (bad). This would be a first step to determining if the injectors are the source of your problem. If it turns out that you are trying to run the injectors in a non linear region, you could try dropping the injector flow rate by dropping the fuel pressure; but, that also can change the other characteristics of the injector. Better off to try a smaller injector if you want to fix your idle problem.
The other injector characteristic that can drastically affect idle performance is the injector offset (some people call it opening delay) and the voltage sensitivity of the offset. Some injectors are super sensitive to the operating voltage and the offset / opening time increases a lot as the voltage drops. Confirm the correct injector offset and voltage sensitivity values for your injector and make sure that these are programmed correctly - assuming the AEM FIC allows you to enter these values. Wide open throttle tuning is less sensitive to correct injector offset and voltage correction; but, if you make significant changes to these values you may need to go back and check your wide open throttle tune.
You indicated what the AFR was at full throttle. That is not meaningful for idle performance. What are your idle AFRs and are they bouncing around a lot at idle? If the AFRs are unstable at idle that could be further indication that you may be attempting to run the injectors in or at the edge of the injector's non linear region.
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