1996 Camaro Z28 LT1 Project

[alone_and_insane]

I'm pretty sure they're BWD wires. Plugs are NGK TR55, gapped to .050"

[alone_and_insane]

Thinking out loud here, so bear with me.

First, it seems the stock injectors are providing adequate fuel, but i don't know what kind of duty cycle they're running. I've heard it's not good to run injectors at too high of a duty cycle, but i don't know why. Could someone perhaps enlighten me?

Also, i realized later that i neglected to mention to the tuner that i have a modified (de-screened and de-finned) MAF. I suppose i forgot because the car always had that as long as I've had it. Could that cause problems with airflow calculations from the sensor?

[JoeliusZ28]

Descreening a MAF is a bad idea imo, generally causes way more problems than it solves. Id try another MAF. My car has stock injectors with 370rwhp and its been fine for 8 years that way. No idea what my duty cycles are, but i imagine im pushing their limits.

[alone_and_insane]

For the record, i didn't do any of the modification haha. What's the screen even for? Prevent debris from hitting the hairs on the sensor?

[JoeliusZ28]

Its more to smooth/even out the air flow as it passes by the sensor. So without the screen you might get more erradic readings from the sensor which can make the pcm think it needs to make adjustments when everythings fine.

[alone_and_insane]

Ah, brings me back to fluid dynamics and laminar/turbulent flow. I know MAF sensors don't like turbulent flow, i just didn't know the screen was meant to smooth it out. Do you think it's possible that at that RPM the airflow is getting too turbulent for the de-screened MAF to handle?

[alone_and_insane]

This is the kind of thing that makes the powertrain calibrator in me wish i was there and could see the data real-time

[birdie2000]

Peter, I have a good MAF if you want to try another and/or buy one. Not sure if you would need the tune adjusted to see any difference though since it was tuned around your old one, not well versed on that stuff.

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[alone_and_insane]

Well they said that once i got the issues sorted i could take it back and they'd finish the tune at no extra charge, so if a new MAF changes it won't be a big deal

[birdie2000]

Cool. Let me know if you decide you want it. The one I have was a new GM part and has less than 1,000 miles on it.

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[Schuby87]

Isn't the ECU OL at WOT? If so, the MAF reading doesn't matter.

[JoeliusZ28]

Isn't the ECU OL at WOT? If so, the MAF reading doesn't matter.

^Good point. Youre right it shouldnt matter. Also the maf is going to modify fueling not spark, im curious what information the tuner had that had him convinced it was an ignition issue. (Not doubting him but to help track down the problem)

[alone_and_insane]

Thanks Brett, that's an excellent point. I guess the only thing that would indicate it's not a fuel issue is the fact that I'm running rich up where it's breaking up. Again, i don't have any data to say what the injectors are being commanded to at that point, but if it's getting plenty of fuel, and i don't see how airflow would be an issue with my heads and cam, all that's left is spark.

[MP81]

Thanks Brett, that's an excellent point. I guess the only thing that would indicate it's not a fuel issue is the fact that I'm running rich up where it's breaking up. Again, i don't have any data to say what the injectors are being commanded to at that point, but if it's getting plenty of fuel, and i don't see how airflow would be an issue with my heads and cam, all that's left is spark.

Spark, or spark timing. Can you log data while doing a WOT run? Maybe it's sensing knock (whether it actually is or not) and retarding timing?

[alone_and_insane]

Unfortunately I don't have any data logging equipment or software, so i have no way to correct any data