Cutting power before fuel cut off?

[kjlindgr]

Hopefully this is a softball issue for you guys. I'm having an issue where I have an Gen-3 setup that's cutting power way before the scheduled RPM limits. I'm scratching my head as to why. Fuel cutoff is set to 6800 but injectors cut at about 5500-ish. The vehicle is a manual trans application with cable throttle. Tune is set accordingly as far as I can tell.

I have a tune file and log of the activity attached.

In the log you can see right around 5500 RPM the TPS is still 100% and injectors are 12ms. Right after that you can see TPS is still 100% but injectors cut to 2ms. I can't say I've ever run into this.

Thanks guys!


run5_cut.hpl
TUNE_SD_KR_0013.hpt

[blindsquirrel]

Your MAF is not failed correctly, for one thing. Was that log the first engine run cycle after a flash; do you normally get a Current P0102/P0103 set?

Is the injector data correct? Something is not right with numbers in your VE peaking at only 68, yet injector flow rate is showing li'l ol' 26lbers...

[kjlindgr]

Can you help me understand what I missed with failing the MAF?

The car has some cheap-o MAF on it. The IAT works, but the air flow sensor part of it does not. So it will set a P0103 circuit code which is why I have that disabled. This is the first run after a flash, yes.

The issue you are seeing with VE is not the injectors. I made an oops and have this cylinder volume set as a 6.0L when it's really a 5.3L. I'm planning to go back and adjust but I didn't figure that was my issue with fuel cut.

[kevin87turbot]

Sometimes, when you're datalogging a P01, you'll have some channels that lag a bit when you datalog numerous channels. In your case, you'll likely find that you can remove 1/2 of your channels and the datalog will make more sense. Once you do that, and log the remaining channels at the same frequency, you'll get a better picture of what the problem is.
In your case, the VE table appears to be way too low in the upper region. With those 26 lb injectors, you should be using way more than 62% Injector DC at upper rpm.

[kjlindgr]

I believe the VE is a reflection of me mistakenly scaling the engine size incorrectly. It's currently scaled as a 6.0L when it's a 5.3L engine.

I didn't seem to have any lag in the logs on this run. I do know what you are saying though and have had that issue in the past.

[Alvin]

Hopefully this is a softball issue for you guys. I'm having an issue where I have an Gen-3 setup that's cutting power way before the scheduled RPM limits. I'm scratching my head as to why. Fuel cutoff is set to 6800 but injectors cut at about 5500-ish. The vehicle is a manual trans application with cable throttle. Tune is set accordingly as far as I can tell.

I have a tune file and log of the activity attached.

In the log you can see right around 5500 RPM the TPS is still 100% and injectors are 12ms. Right after that you can see TPS is still 100% but injectors cut to 2ms. I can't say I've ever run into this.

Thanks guys!


run5_cut.hpl
TUNE_SD_KR_0013.hpt

The manifold pressure is dropping quick even with throttle wide open at 5500RPM.

This points to a intake elbow sucking shut.

[kjlindgr]

Huh...that's very interesting. I had someone watching on a few of the pulls and they indicated that the elbow would suck down "after" the pull, but I'm thinking it's actually sucking closed "during" the pull and I'm letting off because the engine hits a wall because the manifold pressure plummets.

I will report back!