5600 rpm limit I can not get rid of or find.

[vr4508]

I have a 2005 silverado with a 400" engine, big cam, headers ect. It hits a mystery limiter at 5600 rpm in neutral or in gear. At first i thought it was just a shift issue but it does it in neutral as well. Attached is a pair of logs that show it and the tune I currently have in the ecu. The tune has a bunch of stuff changed i normally don't mess with but I'm kinda grabbing at straws.

All the normal limiters have been changed, abuse mode off, it does it with either the etc limiter on or off, I'm not sure what I'm missing.

Thanx for any and all help.

[04silverado6.0]

Log misfire, o2 voltage b1s1 b2s1, stft and ltft both banks. Doesnt look like a limiter to me. Are you getting valve float?

[edcmat-l1]

The tune has a bunch of stuff changed i normally don't mess with but I'm kinda grabbing at straws.

If this is the case you need to flash it back to stock and start over.

After looking at a data log how can you even tell? Looks like the throttle blade shut because you let off the pedal.

[vr4508]

Log misfire, o2 voltage b1s1 b2s1, stft and ltft both banks. Doesnt look like a limiter to me. Are you getting valve float?

Thanx for looking. as requested here is the log.

I dont think its valve float, its just too consistent.
I tried logging the cam hi low to see if I was loosing a cam or crank signal but it looks to not count that above about 4000.

[04silverado6.0]

Here is a file with some corrections. Probably not going to help with the issue. I would pull the valve covers and check for a broken spring or rocker arm loose, etc.

[vr4508]

Here is a file with some corrections. Probably not going to help with the issue. I would pull the valve covers and check for a broken spring or rocker arm loose, etc.

Yeah, same issue. Thanx though. Appreciate it.

[blindsquirrel]

Is there an app that translates 'big cam' into actual numbers that mean something?

[vr4508]

Is there an app that translates 'big cam' into actual numbers that mean something?

summit 8709r1
238I 246E 113* 626I 605E
Factory rockers
comp 26918 springs locks and retainers

[edcmat-l1]

Why don't you trying pushing the pedal all the way to the floor? I know, it's a novel idea....

[vr4508]

Why don't you trying pushing the pedal all the way to the floor? I know, it's a novel idea....

Cuz it didn't seem to matter.

Novel idea performed. Here is log.

[edcmat-l1]

No MAF or MAP in the data. Looks like it just runs out of airflow.

Also need to log your injector on time and duty cycle.

When in doubt, flash it back to stock and start over. Might not be a "tuning" problem but if the calibration has a bunch of weird changes to it, it's always best to wipe it out and start over.

[codykeen0923]

Yeah, same issue. Thanx though. Appreciate it.

hey buddy try this and let me know if it works!!!!

limiter (1) 2024.hpt

[vr4508]

hey buddy try this and let me know if it works!!!!

limiter (1) 2024.hpt

Unfortunately, no it did not. But thanx for the attempt.

I tried downloading a fresh stock tune file from the repository. I changed just the bare minimum things like injectors and idle speed and tried again with the same results. I'm kinda stumped still.

[SiriusC1024]

I think you're just running out of fuel. Verify pressure. Log Injector Duty Cycle for both banks as well as Cylinder Airmass.

[edcmat-l1]

You're not logging MAF or MAP. It could be an airflow issue. You wouldn't know because you're not logging the right pids.

[SiriusC1024]

Yeah those, too.

[vr4508]

I had logged some of that stuff previously but didn't notice anything weird.
But I re-added those suggestions and made another log. I was only given the option to log the PW on one bank for some reason. I also tried it without the maf by failing it, unplugging it trying it with the same results. I did this because the maf signal is all over the place while its on the "limiter" I thought that could be a cause, but it does it regardless.
Fuel pressure stays steady.
Thanx alot for the input.

[edcmat-l1]

MAP sensor ever so slightly drops as long as you're on the "limiter". Need to buy or rent an exhaust back pressure gauge and check the BP. It's going to be something weird. Airflow in or out or valve springs. I've seen weak springs do pretty much the same thing. It's nothing toon related. The blade stays open, it has enough fuel to keep the narrowbands 800ish mv. It doesn't pull the timing way down. Tooning wise that's about all you need to know.

[SiriusC1024]

He's got Comp 26918 springs. 372 lb/in rate, 125 on the seat. Unless install height is wrong...

You don't think the MAF reporting wrong airflow>wrong cylair>too much spark advance is limiting it? Look what happens after 4800rpm.

[edcmat-l1]

Nope I think the MAF is a symptom not the cause. Airflow drops. The MAF is only reporting what it sees.

It's sucking the air filter shut, or the exhaust is plugged up, something weird.