LLY hesitation

[LarryJewell]

I'm looking for some tuning input, Say i'm in traffic going about 40mph and I stab the throttle, there is a hesitation of like about 1 sec., then my truck slingshots forward. The truck is shifting awesome, has great boost, etc, I just would like for it to hammer from the start of the throttle jab without the hesitation, kinda like the LB7 does.

I'm thinking its one of the maf limiting tables in the fuel injection group causing this, B0751, B0752 or B0728.............I'm thinking they may be set to agressive possibly or is this just a LLY thing we need to learn to live with.

FWIW, I have tried all kinds of different settings with these tables.

Maybe the folks at EFI Live could open up a few more tables for the LLY's to play with
__________________

[beach_33]

well for what it is worth larr i am tring to go through some of the lb7 tunes that i have to see if there are any tables that we are missing

[LarryJewell]

Possibly TBIQ, maybe the transition between 3/4 fuel to full fuel, maybe bring it together tighter.

[GMPX]

What I'd like to see in this thread is the current problem list the LLY tuners are having and then some responses if anyone has cured the problems with what we have available before I go hunting down tables that don't exist.

Cheers,
Ross

[beach_33]

well ross the biggest problem that i think most of us are having is the way when you punch the throttle the truck doesnt seem to go to full throttle instantly. instead it seems to ramp up. if you are crusiing around town and mash it, it downshifts, and you can literally count "one-onethousand" before it "rolls" in the fuel. Thats a good way to describe it...the LLY's dont fuel hard when you mash it; they "roll" in the throttle.

i dont know exactly where the fix for this would be. and as far as i know no one has come up with a fix. i think pat and brayden are the closest but still no actuall fix

[DURAtotheMAX]

here is some wierd LLY stuff.

It always seems to occur at ~3100rpm. Whats with the defuels.

SOmetimes it does it, sometimes it doesnt. Sometimes its a violent on/off/on/off defuel, as if im taking my foot off the pedal quickly, then mashing it again, then other times, it just lays down.

stupid LLY electronics.

ben

[DURAtotheMAX]

btw the only consistancy in logging is "driver demanded torque"

Ross, what tables/things INTERNAL to the ECM can affect/modify the "driver demanded torque" levels/limits?

Its not my pedal position sensor.

ben

[beach_33]

i think i see what you are talking about. i see that your mm3 bounces from 105 all the way down to 90mm3. mine does the same thing. i cant figure out why. i also had thought that when we where talking about the way the motor seems to stumble when you stab the peddle that maybe it had something to do with a peddle table that we dont have. perhaps some kind of limiter that doesnt let mm3 go to full on with in a certain amount of time :bad:.

[beach_33]

here is my latest log

[GMPX]

Ben, thanks for the log.
As an indication of the problem, would I be looking at frame 1132 - 1168 where the throttle is at 100% but the mm3 is not consistent? particularly 1132 - 1138.

Cheers,
Ross

[LarryJewell]

here's a log from a while back, pulse width is hunting in the later part, mm3 jumps around a little too. I'll try and get a log of the throttle heistation this weekend.

[Big D]

here is some wierd LLY stuff.

It always seems to occur at ~3100rpm. Whats with the defuels.

SOmetimes it does it, sometimes it doesnt. Sometimes its a violent on/off/on/off defuel, as if im taking my foot off the pedal quickly, then mashing it again, then other times, it just lays down.

stupid LLY electronics.

ben

I think you may have to log different pids to get a better picture of what is really happening. Your current pids work good for a LB7 but dont tell us the whole story for your LLY.

log
GM.ENGTQRREF_DMA
SAE.TP
GM.MAIN1Q_DMA
SAE.BARO
If available, GM.TRQ_FACT_DMA

This should reference your tables better and then you will be able to see what is being desired vs. commanded.
I find your pulsewidth interesting, frames 3246-3289. It does not seem to be consistent with rpm, TP or VSS.
If you could post up another log with the 3 additional parameters with some wot runs at various speeds showing down shift and "rolling" in one gear. I would like to see you tune to correctly reference the tables and give you a different set of eyes if something can be enhanced.

[DURAtotheMAX]

Ive logged "driver demanded torque" a couple times and it was ALLLLL over the place! Definetly the root of the problem/what the ECM is referring to when it does screwy things with the main rate.

Ill have to find the logs though.

ben

[LarryJewell]

here is a log from a buddies truck "05 LLY", near stock tune, stock transmission, this shows a classic up & down mm3 fuel shot at 100% throttle. The only mods this truck has is a Volant intake, pcv reroute, Opies turbo inlet and 4" exhaust. The truck holds rail pressure good, but notice the mm3 hunting throughout the run.

Actually attached is a before and after log of installing Opies turbo inlet and the pcv re-route.

Opies turbo inlet is actually the part used in some MPI twin turbo kits.

[killerbee]

Larry, the problems with your logs (defuel) is torque table settings.

Ben, I was surprised to see you didn't log "maximum engine torque". Looks like the dips you are referring to are colocated with shifts.

[LarryJewell]

bumpty :angel_innocent:

Ross, please see this thread

http://www.duramaxdiesels.com/forum/showthread.php?p=207018#post207018

[cmitchell17]

I always though this was just bad turbo lag with my LLY. It looks like it from my logs seeing how slow boost comes in. I have maf limiting on but its still slow with no maf limiting. I don't have another truck to compare it with so it might not be slow.

[GMPX]

Please see here for some testing to try to track down this problem -
http://forum.efilive.com/showthread.php?t=10732

Cheers,
Ross

[DURAtotheMAX]

here is a log from a buddies truck "05 LLY", near stock tune, stock transmission, this shows a classic up & down mm3 fuel shot at 100% throttle. The only mods this truck has is a Volant intake, pcv reroute, Opies turbo inlet and 4" exhaust. The truck holds rail pressure good, but notice the mm3 hunting throughout the run.

Actually attached is a before and after log of installing Opies turbo inlet and the pcv re-route.

Opies turbo inlet is actually the part used in some MPI twin turbo kits.


Larry thats interesting that after the mouthpiece install it started to drop off mm3 more rapidly... hmm

ben

[abkimble]

I always though this was just bad turbo lag with my LLY. It looks like it from my logs seeing how slow boost comes in. I have maf limiting on but its still slow with no maf limiting. I don't have another truck to compare it with so it might not be slow.


I see six things happening in a 1.5 second time frame. Pilot going off, engine rpm climbing faster than mph in scale, throttle based injection quantity dropping due to rpm, torque limited injection quantity changing due to anticipated shift, rail pressure way below desired and a gradual increase back up to mm3/commanded pw... All of these symptoms compound to create one huge problem. Even with a vvt it's hard to get boost from fuel that will not burn. I say you have a bunch to fix before you can pick on the poor turbo.

I'm referring to 1496 to 1504

[abkimble]

here is a log from a buddies truck "05 LLY", near stock tune, stock transmission, this shows a classic up & down mm3 fuel shot at 100% throttle. The only mods this truck has is a Volant intake, pcv reroute, Opies turbo inlet and 4" exhaust. The truck holds rail pressure good, but notice the mm3 hunting throughout the run.

Actually attached is a before and after log of installing Opies turbo inlet and the pcv re-route.

Opies turbo inlet is actually the part used in some MPI twin turbo kits.

The hunting through the run is the starting at frame 31 tliq goes to a lower torque request until frame 32 and because rpm has changed in just the right amount according to the tune you get a bit of a jump all the sudden in mm3. Then torque limiting is asking for a huge torque decrease and from 33 to 34 has another huge drop in mm3 then 34 to 37 is torque coming back on gradually. From frame 48 on tbiq starts cutting mm3 because of rpm { my guess because I don't have the tune }.

[abkimble]

Possibly TBIQ, maybe the transition between 3/4 fuel to full fuel, maybe bring it together tighter.


Have you logged vane position? Is it progressively getting worse with the large diameter compressor wheel you run in your cheetah? Did it change to a bit more lag compared to the last cheetah you had?

[abkimble]

here's a log from a while back, pulse width is hunting in the later part, mm3 jumps around a little too. I'll try and get a log of the throttle heistation this weekend.


pw hunts because of actual fuel pressure changes. And, as KB says, the torque thing. B0744 to be exact. May want to make this table reflect a bit better in tbiq.

[killerbee]

I'm looking for some tuning input, Say i'm in traffic going about 40mph and I stab the throttle, there is a hesitation of like about 1 sec., then my truck slingshots forward. __________________

I came across something odd.

Is your issue with DSP or a non-dsp OS?

[LarryJewell]

been running dsp exclusively since it was available

[killerbee]

I was kept very busy trying to resolve a fuel/defuel related hesitation, off idle. It was driving me crazy, very annoying, because I sell refinement. Hickups don't work for me. Anyway, then, in analyzing my logs, I saw that it was happening in all of the DSP switch selections, BUT NOT the main tune, (position 1). I looked at every table to be sure I hadn't copied/pasted incorrectly, took me hours of backtracking.

And then I noted there seemed to be a speed correlation, in my case it was happening off-idle, and until I got to 2 mph, then was not detectable. On a whim, I went to A0136 and changed it from 2 to 0 (I don't know why I set it to 2). Problem gone.

Maybe these parameters are causing your issue. A0136-A0138

[killerbee]

A0137 might create this delay issue also, as the throttle passes the elected setting.

[Cougar281]

Michael, FWIW, I've noticed the same thing as you with the off-idle hesitation with the DSP OSes. My A0136-A0138 are set to 0. Any other thoughts?

[killerbee]

No. Mine are fine now as far as I can tell. They are set to 0, 90, and 0. This works perfect for that first touch of throttle. Kitten smooth now. Maybe you should raise the 0137 value. ???