DFCO Not possible with loose converter?

[Time2Kill]

I recently bought a turbo truck and I've been going through the tune to try and increase the MPG since it only gets about 10mpg.

I've been fighting DFCO and have been having problems with it. I can get DFCO to enable, but it disables after about 2 to 3 seconds because the RPM of the truck is falling below 400 rpm (I have it set to disable at 400) when DFCO enables while cruising between 50 and 60 mph. Is DFCO not possible with a loose converter or could something else be causing the major RPM drop? I'm running a 4L80E with a Precision Industries 3800 stall.

Any help would be appreciated!

[Time2Kill]

Just an update to original post. I can get DFCO to work above 55~60mph.

Anything less than 50mph, the truck will actually stall out (I had exit limits very low for testing/scanning). I've now got DFCO exit at 750rpm and the truck will stay in DFCO until about ~50-53mph at which point it hits 750rpm and exits out. I was able to take a freeway this morning and it seems to work pretty good above 60mph. Just wish I could make more use of it for city driving as that is what I do the most of.

[wyochimneysweep]

if there was a way to hold lockup on decel it would really help

[LSxpwrdZ]

I'm assuming that you did a segment swap for the 80e, that is the reason. They unlock when you let off the throttle. Most of the 60e segments do not unlock when the throttle closes. There are tables for this that we cannot see in hptuners software.

[carlrx7]

need to figure out a way to keep converter locked. i have a 3600 yank that i can keep locked and can stay in DFCO all the way from 76 to 20 downshifting with the paddles.

[wyochimneysweep]

Yes I did a segment swap

[Chris@HPTuners]

email your tune to support, i'd like to solve this for all 4L80e's

[LSxpwrdZ]

[wyochimneysweep]

You talking about the segment swap from a 4l80e to 4l60e. what should i put in the subject line. I'd like to get my mine to hold on throttle lift. Sucks when you cruise at 40mph at 3 percent throttle and any little decline you have the tcc unlock.

[edcmat-l1]

email your tune to support, i'd like to solve this for all 4L80e's

I'm going to send one in.

[wyochimneysweep]

sent my file in. hopefully it can be fixed. it would be nice

[Chris@HPTuners]

quick question, when you log TCC Mode and are cruising with TCC in Locked state, what happens when you let off the gas? Does it go directly to Off or something else in between?

[Chris@HPTuners]

also someone please post a tune that does not unlock when you let off, preferably OS 12212156

[wyochimneysweep]

I havent log tcc state but i got the tables set to 99 min and 100 max and as soon as i let off it unlocks and then the sec i push down a little it lock almost right away

[Chris@HPTuners]

ok added some new params to the editor for OS 12212156, under Trans TCC section. Requires version 2.23.590 or later.

Minimum throttle release
- this sets the TCC to Off when ever the TPS is below the thresholds
- there are two vehicle speed modes, high speed and low speed
- for each mode there is a low TPS threshold, if the TPS is below that threshold the TCC will switch to Off if the PCM is not in Coast mode.

From what ive seen the 4L80e cals do not use the Coast mode, but let me know if this new stuff just doesn't work for you and you see TCC Mode as "Coast" at any time.

When you set the thresholds it's probably a good idea to make sure the TCC will unlock at low throttle and low speeds, so try to change the VSS modes and high speed thresholds only as a first attempt.

I have also added a bunch of TCC related status bits to the scanner which will help you see why the TCC is changing to "Off". There are a lot of reasons why the TCC can be set to the Off mode.

eg.
- TqMgt or Misfire request Off
- trans is in 1st gear
- trans cold
- brake is on
- TCC fault
- slip related
- min throttle mode (the new params control this)
- large negative or positive TPS transients
- Off during upshift or downshift
etc.

[wyochimneysweep]

Will scanner status bits work with other OS? attached is my tune

[Chris@HPTuners]

new beta up with support for your OS as well in the editor. 2.23.591 or later

Yes the new PIDs will work for all 99+ LS1's

[wyochimneysweep]

ty chris

[LSxpwrdZ]

AWESOME!!!! This will make alot of 80e swapped customers very happy!!

[Chris@HPTuners]

Please let me know if it works, before we all get too excitied