Adjusting Defuel - A brief How-to

[Nick]

To fix a defuel issue on an '01-05 Duramax/Allison, adjust the torque limited injection quantities in the rpm range where the shift is taking place, at the torque number you're seeing while logging DMAX_TRQ_DMA during the shift.

While watching the main rate in the log you'll see a dip from say 95mm3 to 25mm3 (this indicates a shift, also notice RPM decrease for the next gear), go back to your TBIQ table, with the scan tool open and the cursor highlighting the 'shift', ajust the highlighted cell/s to somthing more reasonable like 70mm3.

The shift RPM (base Tq/TLIQ) and trans tune (read max torque by RPM/TPS) both play into shift torque request. So you may have one truck that shifts well on an engine tune and one that defuels hard, it's likely that the defueling one is shifting higher in the rev range.

Hope this helps folks,

Nick

[stacks04]

thanks nick

[FIREFIGHTER 503]

Is that the same method used for LBZ?

[James Hess]

What exactly is the reason for defuel? <-- I am a little confused by this feature cause i havnt heard much about it.

[hondarider552]

What exactly is the reason for defuel? <-- I am a little confused by this feature cause i havnt heard much about it.save the trans from going boom, but a reason to call mike ):h

[Crazy_Steve]

save the trans from going boom

I never really believed in that...... ):h

I think I'm on my last leg...

[Ridge_Runner_Diesel]

TCM Files on 2001-2005 are not all the same..........;)

If you want to see the differences you will have to do some digging into them.

:thumb:

Also the WOT request is IMHO ties somehow to transmission temp, although I am not positive, but from logs I have the trans temp will make a difference.

):h

[James Hess]

I figured it was to keep the tranny alive.

[Mike L.]

Just remember if you do not defuel on your shifts, you will loose the trans. Then you can send the bill to your tuner.:thumb:

[EDP]

Like Mike stated above be sensible on the defuel. Though it will make for quicker E.T.s it will also make for a quicker trip to the trans shop. I would highly recommend that if you decide to take away the defuel use it for competition use only!

Nice way of explaining the process on how it can be done Nick. Great help to the average guy trying new things.:thumb: