AusS2000

I have an MY2000 S2000 with Comptech SC (no aftercooler), 8lb pulley, 440cc injectors, enlarged throttle body, SARD FPR and E-manage (Injector and Ignition harnesses).

The car runs beautifully when I first start up. Pulls hard and has loads of power (214Kw in fact). But after a short period of time it has trouble launching. I'll be sitting at lights and when they go green I give it some throttle and start releasing the clutch and it just dies. It doesn't actually stall if I'm quick with the clutch, and if I rev it and drop the clutch it behaves fine.

My tuner keeps telling me it's due to the ECU learning fuel trims and then changing between open and closed loop with throttle position. He suggests removing the larger injectors although I doubt the stock injectors can deliver enough fuel without the Comptech FPR. I don't think that is the solution nor the soure of the problem and would rather try some other ideas before I go through the task of swapping injectors again.

Hardtutame's throttle body problem has me thinking I should try the original TB again and see if that changes things. Anybody else have any ideas as to why this is happening and possible solutions?

AusS2000

Come on guys, 17 views, no news!

kstokell

Hi Aus,

Difficult one to help with this, as you are one of the few running the E-manage with SC etc.

You say it starts after a while. Does that mean its OK when cold but starts to occur once the engine reaches normal operating temperature. Or is it after a random period of time not related to engine temp.
Does it happen after you have been sitting at idle at the lights for a long period of time? Or is it not related to the idle time?
Do you experience the problem after a period of high speed activity? Or is it again random?
I think if you start to try and identify when and where it happens you will be half way to solving the problem.
If a pattern can be established you may be able to identify the cause, timing, fuel, etc.
If it is a completely random type thing you might need to start changing thins until you find the underlying problem.

Sorry I can't be of more help.

Regards Kevin

kstokell

Aus,

Just a couple of extra questions,

I assume it's a low rev pull that's causing the problem?

At what revs does it start to bog down?

What I mean is that I assume the SC is not delivering any boost?

Kevin

chris_barry

Aus2000,

Your stumbling sounds like its fuel related. It will be either rich or lean. How can you tell which is which? Its easiest with a naturally aspirated engine as you can hear the induction note which is important. You could try driving off idle with the elbow between the grunt pump and throttle body removed. This will show if its boost related.

Lean mixture. The car will bunny hop off idle and will spit back through the throttle body. The exhaust note will be relatively quiet as there is very little going bang inside. Once you get through the lean spot the engine will recover cleanly.

Rich mixture. The engine note will become pulsing and the engine will bog down. There will still be an exhaust noise. When you get through the bad section the engine will take a little while to clear the fuel. Get someone to follow you as the exhaust will emit black smoke.


The best way to tell is to get a good quality a/f meter and drive the car around. You should be able to similate this on a dyno and look at the mixtures. One thing to watch out for is that a really rich mixture can show up as a lean mixture on the meter. This happens when the mixture is so rich the flame goes out and unburn fuel and lots of oxygen goes down the exhaust. The meter sees lots of oxygen and thinks the car is running lean. When its this rich you need to go back to basic as above.

Speedracer.

Call me if you want a contacts for a guy in Sydney who can rig up an AF meter to your car and ride shotgun with you. To do this properly you need an extra nut on your exhaust so you can bolt in a third sensor.

AusS2000

I seem to have fixed the problem. Looking at the E-manage maps there is a huge change from 0% to 5% throttle position. I simply brought the entire top row up to -35.



I guess the sudden change in the MAP sensor was confusing the hell out of the ECU and causing the stumble.