2006 8.1L turbo, ETC closing to 70% @WOT and 4000RPMS

[Robi's Repair]

The title pretty much explains the problem. What we have here is a Dart block, 588 cubic inch engine. 2 67mm precision turbos. I am nearing 400whp and 600wtq at 7psi. What is happening is that the Electronic Throttle is closing from 100% to around 70% at about 4000RPMS at WOT which causes an unwanted loss in power. My concern is that it is a VCM limitation because the Max Torque value in the tune file cannot be set higher than 640. Any thoughts or suggestions are appreciated.

LOG:

588tt-lost throttle.hpl

Tune:

2006 Chevy 2500HD 588_006.hpt

[mecanicman]

Disabling the knock retard is a very bad idea on any engine, but the 8.1 especially. I strongly suggest you put it back to stock settings. You have applied a 2 bar o/s but you have switched it back to maf? Its not the torque max holding you back. You didnt mention any codes, are there any? I suspect the check between map/maf is failing and that is cutting your power.

You need to add commanded afr and 2 bar map to the scanner so you can actually tune it.

[Robi's Repair]

I did not realize the knock was disable, that has been restored. Please give me some more insight as to how to switch from MAF to MAP. The a/f commanded PID is not highlighted in the VCM scanner which leads me to believe it will not work. Is there another way around this or some other way to set it up? If there is some "getting started" reading material that you can recommend, I would appreciate that.

Thanks,
Chris

[Robi's Repair]

Well, I figured out how to add the other pids to the scanner. I'm not sure why it took me so long to find that little piece of information.

[mecanicman]

What injectors are you running? I missed the part where this dart block, whats the bore stroke? Do you even have the knock sensors?

[Robi's Repair]

65lb injectors, aeromotive a1000 and FPR. I don't have the bore/stroke in front of me but it is 588 cubic inches, which is reflected in the engine displacement per cyl. under Engine General. The knock sensor is installed and active as I found today. It is pulling a few degrees after a minute or more of driving which leads me to believe that I need to redo the PCV system a little, maybe add a catchcan.

[mecanicman]

Whats the firing order, you just moved the wires around to accomodate this? Injector brand?

[Robi's Repair]

the coils are set up to fire factory firing order. Being a Gen 4 block(I think) it may have the old 18436572 firing order...though that hardly seems possible because it runs very well. I have been tuning on it all morning, and got the MAF dialed in and my commanded a/f is very close to actual measured with a wideband.

injectors are deatschworks.

[Robi's Repair]

firing order is ok. it is the same as a LS1. I just talked to the engine builder, so that is not an issue.

also, I am starting to believe that the throttle closing is an ABS/traction control issue that I may not be able to turn off since it does not do it on the road.

[MikeOD]

On the trans desired torque table (Trans - Torque Management) you have that set to 600 across the board. You also have the performance TQ management table still reducing torque during shifts...not sure what you're running for a transmission (allison I guess, but I don't know how strong it is) or if you wanted that to occur, but you could zero that out to be sure. While abuse mode is disabled, the reduction table for it is not zeroed out...can't hurt.

I also noticed that your Desired Throttle Area Alternate table is set to max at 69.7%...while normal is set to max at 100%. I don't know what will command it to use this table, and I'm not sure if you can modify it without sending the computer into a permanent DTC, but this and the 600 ft*lbs number you mentioned both seem to be the same numbers as your problems. You also have not maxed out any of the trans input/output max front axle max and rear axle max stuff...can't hurt to do that too.

I don't know if any of it is going to solve your problem, but it's a few more places to look.

[MikeOD]

Aos, I just realized, you're running the 1 bar MAP OS, but it looks like you're running it MAF only? Why not run the MAF enhanced OS instead? Or the standard OS?

[Robi's Repair]

Thanks for the suggestions. I am not sure about any of the differences in the different operating systems or their benefits. Is there a 'read me' that I can check out to get more info on this?

[mecanicman]

Aos, I just realized, you're running the 1 bar MAP OS, but it looks like you're running it MAF only? Why not run the MAF enhanced OS instead? Or the standard OS?

I think you better look again.........

[Robi's Repair]

I am running the 2bar OS with a 2 bar sensor. I'm not sure if that is working in my favor or just there.

[Pekka_Perkeles]

Which TB? NW 102?

[mecanicman]

Go to the speedo section, max out all the speed limiters. its holding you to 98 mph, like the limiters are set to.

[Robi's Repair]

Go to the speedo section, max out all the speed limiters. its holding you to 98 mph, like the limiters are set to.

Dang. You got it. how many speed limiters are needed?!?!

THANK YOU

[MikeOD]

I think you better look again.........

I made a typo, I meant it's the 2-bar OS, but it's running in MAF only...this is actually a Gen 3 PCM, which I think HPTuners says is untested.

[Robi's Repair]

Just so I am sure, to fail the MAF and work in SD, all I have to do is set the MAF Fail High to "0"? I read the "how to" in the help file and that seems to be it other than forcing OL. Do people fail the MAF a little higher so as to use it in low engine speed operation and switch to SD later. I think in the case of a giant cam with a lot of overlap it would be beneficial to use MAF to get a stable idle.

[MikeOD]

The MAF won't "unfail" after it's failed, so you can't set it to something in hopes of using it down low...and SD is generally better/more stable for idle and low RPM as a cam gets more bumpy anyways.

You need to set the fail high frequency to 0 and then on the DTC tab, set P0103 to "0 - MIL On First Error". If you uncheck the box the code will set but the light on the dash wont turn on. After that you'll see the code with a scan tool, which will tell you you're in SD mode.