Debugging, again!!

[horsewidower]

I need cooler heads to help me think through the issues we're having on the roadrace car.

While on the dyno the car performs without a problem. Runs up through the rpm range without a complaint and AFRs look good.

Then we go to the racetrack and it starts breaking up, can't tell if its a lean misfire or an ignition problem. It pops and seems to misfire, I'm not hearing any detonation. Plugs look good, we're running on E85.

So its something that only happens in a dynamic situation. Are we running a map that is not tuned to take all the situations on the track? Data logging would probably help, but the damn Haltech won't download to the laptop. So we need to fix that first, I guess. Could it be a bad wiring connection? But you'd think that would manifest itself on the dyno. It could have been that the fuel pump was going away.

Anyhow, any thoughts on what I'm missing?

Bob

[Matt Cramer]

Re: Debugging, again!!

When it was tuned at the dyno, was it just tuned at full throttle, or did they do any steady state tuning at low load?

[horsewidower]

Re: Debugging, again!!

The cert run was on a Dyno Jet with full throttle runs. The initial tuning was a Mustang and they did some steady state work. I'm not sure it was enough.

[dieselgeek]

Re: Debugging, again!!

When popping and banging under load, I always want to look at a datalog. Usually I see "RPM nonsense" - i.e., the computer's not tracking RPM properly. It'll show up as inconsistent RPM data...

it can be a lot of things. Cracked spark plug porcelain seems to be a recurring theme lately - double check for the little things like this.

Is it only under the hardest acelleration? or is it at light throttle as well?

[horsewidower]

Re: Debugging, again!!

Also occurs under light, maintenance throttle as I'm trying to go around a corner.

I've had the porcelain issue a couple of times.

[dieselgeek]

Re: Debugging, again!!

Also occurs under light, maintenance throttle as I'm trying to go around a corner.

I've had the porcelain issue a couple of times.

this is where a datalog of the problem happening is of massive value :-\

[horsewidower]

Re: Debugging, again!!

Yeah, I agree, its job #1. I thought we had it, but it won't download onto the laptop. Very frustrating. You can see the traces realtime, so we know that it should be storing.

[dieselgeek]

Re: Debugging, again!!

could it be something dumb like a lost temp sensor or MAP sensor? even with the laptop plugged in, you should be able to see that you have good temps and MAP values.

[horsewidower]

Re: Debugging, again!!

We have it on the computer during warm up and those sensors appear to be working.

[horsewidower]

Re: Debugging, again!!

I've been redoing the pump calculations as we've been looking for a new fuel pump. I'm embarrassed to say that after doing the calcs and accounting for the loss of volume due to pressure and voltage drops, that we were probably underpumped. I should have checked things better when I changed to E85. Finding the voltage drop and pressure drop maps can be a bitch, though.

We should probably put a boost a pump on the car in order to maintain 14v at the pump. I wonder if anyone has ever tied one into the ECU power supply? I can tell you that the car runs well on 14v, like shit on 12v.

[dieselgeek]

Re: Debugging, again!!

how about a proper sized pump instead of a boost-a-pump? those things have a habit of crapping out quickly. Don't run it on the EMS, as it throws off the injector open time calculations...

[horsewidower]

Re: Debugging, again!!

Well of course that's the best solution.

Thanks for the info.

Bob