CM848 rev hang defuel touchy throttle

[Diamondfabrication]

Hi everybody, Ive spent a lot of time reading and looking at other tunes. I Have tuned a lot of gas engines and had a big injector compound 12v. Iv been making adjustments on this truck for over a year. Certain things I just cant get figured out.

2004.5 6 speed stock injectors, stock turbo, stock intake, 4" exhaust

Question 1
Having a hard time understanding the pedal map, if I raise the mm3 in the 100% column I notice it wont reduce the fuel rate as early ie steady part throttle 2100ish rpm it feels like you hit a wall and have to throttle more to maintain the same acceleration. But I think this is also causing the throttle to be extremely touchy right off idle and in the lower rpm's.

Question 2
Currently I have a lot of rev hang on shifts. I tried reducing fuel pressure to stock below 30 mm3 across all rpms's to stock and it didn't really make a difference. I tried adjusting governor settings: No throttle fuel, deceleration limit rate select rpm, High speed governors, P.I.D. Feedback. But whatever I did caused my main injector pw to drop to 1500us under wot and I still had the rev hang so I reverted back to my previous tune. I was also hoping these Gov settings would help with the defueling under partial throttle.

Question 3
In the 5th gear wot pull this is probably the best I've ever had the truck maintain Fuel Rate and injector pw but you can see it still starts dropping at 26-2700 rpm. Like I said this is the best it has ever been but still seems to be worse in lower gears. Curious what causes that.

Still working on cleaning up spool up and timing but all in all pretty happy with the power output and how the truck pulls our camper, I've noticed egt's are a little lower if I add timing in the 50-90mm3 1800-2200rpm area but hurts spool and smoke a bit under unloaded driving.

I'm sure I'm forgetting a few things and not explaining things properly. Any help or advice is greatly appreciated! Thanks guys, Darren REV HANG.hpl 5THWOT.hpl

[Diamondfabrication]

Forgot to attach tune file. Stormtrooper Current tune.hpt

[Rainman1]

I did the same g56 swap. Go to your turbo wastegate timing for closed/no throttle. It's set from factory at like 3 seconds. Change it to .5 seconds.. should fix it..

basically what you are experiencing is: when you let go the go pedal, the turbo is staying in boost. The PCM actually fuels based on intake pressure so the fuel will still stay on too.. it's like no lift shift in the GM cars. Causes the rpm to stay exactly where it was when you let off for 3 seconds. That was designed to perfectly mesh with the 3 second cycle of the transmission shifts.

[Rainman1]

Changing it from 3 seconds to .5 basically makes it to where the second you let off the pedal, the boost disappears. Thus your fuel problem as well. Once you fix that, you will have to go through your fuel map and fix any fuel changes you made to prevent the hanging revs. I fell for it too. I kept changing fuel and timing when it was literally a boost release delay. Lol. Hope that helps

[Diamondfabrication]

That definitely sounds like it could help! Is that under the airflow/turbocharger tab? I'm having trouble finding it. Not sure if it makes a difference but mine is a factory manual truck and if I load in the factory tune it doesn't rev hang at all. Thanks for the reply!

[Diamondfabrication]

Here is a screen shot of an example of when my fuel rate drops even though i'm 100% throttle and it says running normal under the master fuel correction reason.

dropping fuel rate.png

Also should I have any smoke or haze with this duration and timing table after I have reached full boost? Or are my injectors just getting a little tired? I've tuned and 03 truck and a 06 truck and both run completely clean.