Part Throttle/Torque Cut Blip

[nmartin6631]

Hey all,

Trying to get some advice as to what exactly is causing a blip in power while driving under part throttle.

In the log, at 4:34:34.897 PM, you'll see the engine torque is @ 220 lb-ft, but trans torque is at -54. Next frame, trans torque drops to -74. Prior to the mentioned frame, the engine and trans torque are within spec. I can only describe it as the vehicle completely cut power for a second (fuel was cut, but spark wasn't???).

At this moment, I was on a straightaway, and the vehicle was already traveling at 44-45mph. Yes, I know it's running lean for E85 - I've completely reworked my VVE table to account for this. I needed the vehicle to get me around town for the day, so this tune is what I had. I've adjusted the VVE table and torque table to accommodate for more torque/a richer mixture, but it still happens. There isn't any reason (from what I can tell) why it's cutting torque/fuel. Probably missing a PID, but I thought I had enough data logged already for this.

Vehicle mods: no cats, shorty headers 3" collector to 3" dual side exit

Any advice is appreciated.

suburban_SD_STAGE_2.hpt
drive32.hpl

[LS ROB]

I'd say you probably hit a lean cell @88 kpa. Or at least that's what it seems to me. Someone with more experience should be able to say for sure.

[blindsquirrel]

Catalyst test is still enabled. So is Desoot. What else has been overlooked?

[blindsquirrel]

Why is closed loop disabled? Why are you worrying about it not running perfect when it's set up like that?

[nmartin6631]

Why is closed loop disabled? Why are you worrying about it not running perfect when it's set up like that?

I am doing speed density, therefore, commanded OL and failed the MAF. I also have no O2's, other than my wideband (the PIDs are false readings if you're looking at them). The existing P0430 P0030 P0036 are all old before the exhaust work was done. Is there no other way to prevent the ECM from performing the test?

Catalyst test is still enabled. So is Desoot. What else has been overlooked?

Honestly, I thought I disabled these, but they could've been set to back to default when things didn't go quite as planned.

[nmartin6631]

I'd say you probably hit a lean cell @88 kpa. Or at least that's what it seems to me. Someone with more experience should be able to say for sure.

If you look at the VVE table/graph the cells in that area are fairly smooth transitions, so I really suspect that is not the case. Also, MAP cells are 85, 87.5, 90 kPa, so it could bounce around a few cells there. I also decided to smooth the troublesome VVT table as I also think that can be contributing to my issues.

[blindsquirrel]

No O2 sensors at all? Ever? Dumb. You want it to run like stock with none of the tools it uses to get there.

[nmartin6631]

No O2 sensors at all? Ever? Dumb. You want it to run like stock with none of the tools it uses to get there.

I have my wideband in the vehicle at all times. Anytime it's running, I can monitor it visually or via logging.

Anyway, I reimaged a new computer dedicated for tuning and noticed this thread about that parameter missing.

https://forum.hptuners.com/showthrea...on-cold-starts

What version of VCM are you using? I am running the newest beta as I had some issues with the virtual torque table. Is this what you were referring to as "catalyst test"?

[blindsquirrel]

This.

screenshot.17-03-2024 22.37.43.png

Full-time open loop is just stupid. I'm not helping with this any more.

[nmartin6631]

This.

screenshot.17-03-2024 22.37.43.png

Full-time open loop is just stupid. I'm not helping with this any more.

I've ignored your complacency long enough man. You keep saying "dumb" and "stupid". I asked for assistance in tracking down the issue, not a comment about what you think is a smart or dumb thing to be doing.

FWIW - it's not there in the newest beta or stable HPT.
image.PNG


So again, instead of helping, you ranted. If you don't want to help anymore, then don't waste my time.

[DirtyDave86]

I?m here reading trying to learn could someone tell me where I would find desoot settings in the file?

[07GTS]

desoot is in the injector data tab

[LS ROB]

If you look at the VVE table/graph the cells in that area are fairly smooth transitions, so I really suspect that is not the case. Also, MAP cells are 85, 87.5, 90 kPa, so it could bounce around a few cells there. I also decided to smooth the troublesome VVT table as I also think that can be contributing to my issues.

Such an easy task to write off. I mean, you're tuning anyway right? So why not add fuel in that area just to rule that out?

[edcmat-l1]

Put it back in closed loop. Let the PCM do the corrections. Unplug your wideband. Ignore it. Your PCM doesn't care what your wideband says. Neither should you.

[DirtyDave86]

desoot is in the injector data tab

Thanks, I found it. What exactly is desoot mode and would I be correct to disable this if I?m not running cats? Sounds like it?s meant to heat up the converters and clean them out periodically?

[DirtyDave86]

Seems to cause a lot of lean issues on tip in especially on G8s. From what I read it will periodically cut injector pulse to clean out the cats?

[nmartin6631]

Such an easy task to write off. I mean, you're tuning anyway right? So why not add fuel in that area just to rule that out?

I already richened these cells up and it happened anyway. It seems to do it regardless of KR or lean/rich.

I was able to tune the cat test out as well as the desoot (overlooked when jumping to 5.X Beta).

Thanks for your advice Rob. I'll finish tuning up the VVE table to +/-2.5% before moving further with it.

[nmartin6631]

Seems to cause a lot of lean issues on tip in especially on G8s. From what I read it will periodically cut injector pulse to clean out the cats?

Probably what was happening to me, but I have yet to test. I'll likely test it in a few days. Back to work.

[GHuggins]

Desoot is a function to lean out the engine right around 2500 under full power only to super heat the combustion chambers and burn the built up carbon off of the pistons. Just one of many things the OE tried during the gen 4 era to keep things clean. They even introduced spark knock for a time period below 2000 rpms via converter lock and higher timing to try and bust carbon out on some of the truck and van platforms.

[DirtyDave86]

Desoot is a function to lean out the engine right around 2500 under full power only to super heat the combustion chambers and burn the built up carbon off of the pistons. Just one of many things the OE tried during the gen 4 era to keep things clean. They even introduced spark knock for a time period below 2000 rpms via converter lock and higher timing to try and bust carbon out on some of the truck and van platforms.

Very interesting, thanks for the reply