Hello guys, maybe someone can share some ideas. For a few months now my buddy has been having an issue with boost cut or fuel cut not sure which.

The car is an S2000 with an AEM infinity ecu on electronic boost controller. We have tried multiple things but nothing seems to help. The car was tuned with no problems but a couple months later he started getting a boost cut under engine load. We replaced the electronic boost controller (solenoid?) twice.. replaced the spark plugs. Tuner recommended 0.18 gap. Hardwired the fuel pump (walbro450). No solution.

The issue went away when we ran the car with only the 10psi wastegate. Anything above 13psi there is a boost cut. The car was tuned at 16 psi. We tried a manual boost controller but the issue remains the same at high boost.

The tuner sent him a map with lower boost around 12psi and the car ran great. We checked the wastegate for leaks and replaced all hoses. We still cannot get the car to run good under high boost. Any recommendations please. I'm not sure what else to check. My personal car is on hondata with a manual boost controller. It's all I ever used and never had any issues. I'm not too familiar with electronic boost controllers or aem.

 

sounds like boost spike normally caused by manifold design, as far as "not running good" hard to say but most likely the tune.

need more info - motor specs - turbo - manifold used - whats boost cut set to?

 

It's a PLM twin scroll manifold, precision 6262 turbo..tial wastegate.. 1200cc injectors..Boost cut is set at 22psi. Completely Stock engine.

 

What size gate?

 

44mm

 

1) Check the wastegate vacuum reference point. If it's on the compressor cover, that could easily cause boost spike and cut issues. This boost reference should be at the intake manifold groom the side of the gate and not to the compresser cover.

2) wastegate placement: considering it's a divided manifold with one wastegate, it needs to be centrally located, but the divided flange may cause some issues with boost stability.

You're using a larger mid-framed sized turbo on lower/mid-levels of boost pressure, with a low boost pressure spring. Your best best is to reconfigure this manifold to use 2 smaller gates , one for each set of runners.

Your boost is inconsistent because the solenoid (electronic) or ball/spring (manual) is getting an inconsistent vacuum source. you need a slightly larger spring in the single gate, or 2 gates with lower pressure springs to work.

3) Boost control - your boost cut is set too low, thou want that much higher than your target pressure so that ever if it spikes towards your target pressure, boost cut won't come in so early. The boost cut is trying to prevent the car from over boosting, so it's actually doing it's job.

4) .018 Gap? Way too low to use. You need some sort of spark enhancement with a better plug. Keep your heat range of your plug at 7, and relax. You can either enhance the distributor with an ignition box and new internal coil or tho to external coil. You don't need to convert to coil-on-plug yet.

5) time to retune - After your changes

 

do u have closed loop under wot?? because we had this issue. target afr was 11.5 and by higher afr boostcut.

 

Thank you.. the boost source is at the compressor cover.. I will go thru the other items on your list and try to get this figured out. The car is a 2001 s2000 I believe they are already coil on plug. We have alot to look at thank you.

 

I'm not sure. We would have to ask the tuner

 

That's right, I forgot about that. Yes. You're on coil-on-plug already. You are experiencing spark blowout, and need new plugs... AND at the proper gap.. Make sure they are NGKs.