E38 ECM only allowing half throttle after high RPM?

I?m running into a weird issue where my E38 ECM will only allow roughly 50% throttle after hitting the rev limiter on my LS7. You can see from the log that the first pull is normal and pulls strong all the way to the rev limiter at 7,200. After that, the car runs and drives fine but will only allow up to about 50% throttle. The next pull on the log file is with my foot to the floor (which can be seen by throttle pedal voltage) but only a commanded 45-50ish percent throttle and won?t go into power enrichment. After I cycle the key, it?s back to normal. I did check to see if it threw any codes and only got a permanent P0503 code for speed sensor ? Intermittent/Erratic/High.

Any idea what might be the root cause of the computer limiting throttle?

I had recently changed injectors to 54lb flex fuel L94 injectors with a ZL1 pump because my previous injectors did not have correct data. It definitely looks like I?m running out of fuel by 6,000RPM. I realize that needs to be addressed, but not sure if it?s related to the limited throttle issue.

The engine has heads/cam (naturally aspirated) and makes about 620HP to the wheels and is swapped into a 69 Camaro. I used an E38 ECM from a 2015 Z28 Camaro with a ZL1 FPCM and pump. Let me know if you need any more info.

Log and tune attached.

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Attachment 119291

Try disabling throttle torque limit.

Just looking at the log it appears something is off in either engine displacement or injector data. A NA motor will never go above a 1.1ish cyl air mass and even then that's with really high rpms and big money components.

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Originally Posted by Mr.z0611

Try disabling throttle torque limit.

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That didn't seem to work.

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Originally Posted by GHuggins

Just looking at the log it appears something is off in either engine displacement or injector data. A NA motor will never go above a 1.1ish cyl air mass and even then that's with really high rpms and big money components.

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I will double check the injector settings. I did compare a few logs from a Friend's Z06 and my own 08 Z06 and both get into the 1.3-1.35 range with about 600-610 wheel HP. (Not saying they aren't wrong as well)

Update: It must be correlated to the rev limiter. I lowered the limiter to 4500 and changed a few other things. It still does it as soon as it hits the rev limiter. It won't allow me to go full throttle until I cycle the key. I also swapped throttle bodies to see if that could be the problem.

shouldnt have extreme cutoff same as rpm limiter, then ur never on the actual limiter as it will just go into fuel cut, change the ''in gear'' limiter to where u want it then have the extreme cutoff and resume few hundred rpm higher its only there encase the actual limiter dosnt work, not sure if that will help but just noticed it

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Originally Posted by 07GTS

shouldnt have extreme cutoff same as rpm limiter, then ur never on the actual limiter as it will just go into fuel cut, change the ''in gear'' limiter to where u want it then have the extreme cutoff and resume few hundred rpm higher its only there encase the actual limiter dosnt work, not sure if that will help but just noticed it

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I had my hopes up, but no dice. I tried setting the extreme cutoff higher and it still limits throttle after hitting the rev limiter. I made sure I didn't overshoot and hit the extreme limiter.

try max out the wheel speed limit and the oil temp limit just so u dont have all the limits reacting at once see if that does anything

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Originally Posted by 07GTS

try max out the wheel speed limit and the oil temp limit just so u dont have all the limits reacting at once see if that does anything

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I tried maxing both with no change. I also tried messing with the switchover delays just to see what happened. Then things got really weird....

See attached log and tune. When I changed the switchover delays to 5 seconds in all gears/neutral, the rev limiter completely changed. It's no longer cutting throttle. It appears like it's just pulling spark (and sounds like a machine gun vs the ETC rev limit). But after backing off of the rev limiter, it still limits my throttle to about 40%. Then on top of that, it would let me go way past the rev limiter before kicking in the ETC limiter the next time. It only does the spark limiter once per key cycle.

Note I changed the rev limiter to 4,500 so I'm not bouncing off the 7,200 limiter in the garage all of the time trying to test this.

I also found my fuel issue with a clogged fuel filter and took the car to a track day this weekend. I had zero issues in 3 sessions because I stayed off of the rev limiter. I finally touched the rev limiter in the 3rd session and sure enough, I was only allowed part throttle until I cycled the key.

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Attachment 119418

yea that delay is between the settings, first it will use spark if that dosnt stop rpm after 5 sec it uses throttle then if that dosnt stop it after 5 sec it then uses fuel, disable the fuel and ETC see if spark can control it and if it still limits throttle after as it shouldnt be involving throttle anymore see if that helps

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Originally Posted by 07GTS

yea that delay is between the settings, first it will use spark if that dosnt stop rpm after 5 sec it uses throttle then if that dosnt stop it after 5 sec it then uses fuel, disable the fuel and ETC see if spark can control it and if it still limits throttle after as it shouldnt be involving throttle anymore see if that helps

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I did disable ETC. I did keep fuel on though.

when it is limiting have u checked for any codes ? encase there is something in the background causing it and key off/on clears the code

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Originally Posted by 07GTS

when it is limiting have u checked for any codes ? encase there is something in the background causing it and key off/on clears the code

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I have after I hit the limiter on the same key cycle but havent checked the codes while actively hitting the rev limiter.

Finally figured it out! I am using L94 flex fuel injectors and I had copied all of the parameters on the Fuel -> General page from a stock L94 tune. I changed everything back to stock LS7 settings, then only copied the flow rate and offset tables from the L94 tune. I kept everything else in the Fuel -> General page untouched from the stock LS7 settings. Not sure why, but that fixed it!