E38 PE Issue. Lean 2.1 Seconds. Can we solve this?

[NJ_Phil]

That may be where I lifted after seeing WB hit 14:1 about 2 seconds into the pull. See below arrow pointing to it.
desoot1.png

[rich24v]

I expect within the next month. Meanwhile there is nothing wrong with requesting and using the beta.

Hello, have been struggling with this exact issue for months !!! how can I get a beta copy.....or how close is the proper release update please ?

Capture.JPG

[GHuggins]

Go to HP tuners.com and send a request asking for beta...

[rich24v]

Go to HP tuners.com and send a request asking for beta...

Thankyou....all sorted (with a lot of help)....literally a on/off switch !

desootoff.jpg

I think there is a certain aussie tuner glad to see the back of this too!

[RRRocketMan]

Because I found the original explanation a bit terse, I would like to ask for further clarification. The desoot mode, as the name suggests, prevents the formation of soot in the cylinder. No problem. It does so by modifying the injector pulse timing. OK. But how does it achieve this number 1 and number 2, what are the repercussions of de-activating it? Also why only in PE mode? If I were to cobble together a theory, it might be that PE mode is so rich that this is the only time when soot would form, that this lean spike is somehow supposed to "burn off" the excess fuel and that this is like the self-cleaning mode on an oven, to use an analogy. However if it happens right in the middle of WOT and causes a dangerous lean condition, then it's not a very robust theory for a bunch of GM engineers to come up with so I'm inclined to discard it in favor of a more rational explanation. Does HPT have a more complete explanation as to the purpose of this desoot mode? Myself, I'm not comfortable just turning off a bunch of stuff because it makes a specific problem go away. Everything is there for a reason so... what's the reason for this odd lean spike behaviour?

[rich24v]

Agree?.I would like to understand a bit more about this.
This guy gets talking about effects of changing injector timing and how this can change afr, I don?t know if the timeframes actually support this ??
https://youtu.be/TDNA3OeWp-4
However??I can say the desoot mode was present and turned on in the stock NA tune, I have a supercharger giving moderate boost with mild cam on otherwise stock engine. This mode activates based on time after PE activation, so I could be holding 3krpm light throttle waiting to nail a run, I bury the throttle and 2.1 seconds later it spikes lean?..at that point I may be 6krpm full boost??.I really don?t want this to spike lean. Maybe oversimplistic??but I?m more than happy it?s gone.

[RRRocketMan]

Indeed and to add to that, "multiple" vs "single" vs "disabled" injection pulses should also be explained. I've heard that disabling this is "good" but with no explanation as to why. This and the desoot parameter would really benefit from some further elaboration else we could end up with transient issues and fouled plugs or worse.

[APS Luis]

Does HPT have a more complete explanation as to the purpose of this desoot mode? Myself, I'm not comfortable just turning off a bunch of stuff because it makes a specific problem go away. Everything is there for a reason so... what's the reason for this odd lean spike behaviour?

Emissions , emissions , emissions

Good work Chris

[RRRocketMan]

Emissions indeed. However sometimes, the more environmentally friendly way is also the better performance way. For example, when you change manifold pressure, the injector pulse width changes to compensate for the extra air. This changes the size of the fuel puddle on the port walls and the evaporation rate, which temporarily creates a discrepancy in the tau model. The solution is to inject more or less fuel based on the anticipated discrepancy. What if the "single" and "multiple" options in the makeup mode are designed to do that... to activate again after the first pulse, in response to a rapid change in throttle plate angle? Sure disabling makeup mode may make for a simplified fueling model, which might make it easier to tune in some ways, but it also reduces the fidelity of your fine-tuning of stoich (assuming my theory is sound). This is why it's important to known what the heck we're switching off, not just to take someone's word that, "oh it's good for performance!" and leave it at that.

Waiting for HPT to comment on these 2 features (Desoot and makeup mode).

[sillycon]

Desoot mode is fine when you're running 11.4:1 AFR in an N/A application that only occasionally sees WOT (e.g. an OE calibrated street car that will build up soot and NEED to be de-sooted). When you're running a custom tune at 12.5:1 on a track car, "desooting" is not necessary (the car is running hot enough to not soot up anyway) and desoot mode becomes a great way to cook an engine. Ditto if you're running E85 and boost; again, it's not going to soot to start with, and "desoot" mode will cause a lean spike that can (literally) grenade a motor.

[GHuggins]

I wouldn't over think this... Desoot is deactivated on a lot of OE tunes especially those running boost... It's mainly only present on the vehicles that rarely would see wot in factory form - the ones that are idled around in high gears for example...

[RRRocketMan]

Like a Camaro SS apparently, lol. I had mine on by default.

Actually I am far more concerned about the makeup mode, as that is less self-evident. Do you have any insight on what exactly that does? It was set to "multiple".

[10_SS]

Because I found the original explanation a bit terse, I would like to ask for further clarification. The desoot mode, as the name suggests, prevents the formation of soot in the cylinder. No problem. It does so by modifying the injector pulse timing. OK. But how does it achieve this number 1 and number 2, what are the repercussions of de-activating it? Also why only in PE mode? If I were to cobble together a theory, it might be that PE mode is so rich that this is the only time when soot would form, that this lean spike is somehow supposed to "burn off" the excess fuel and that this is like the self-cleaning mode on an oven, to use an analogy. However if it happens right in the middle of WOT and causes a dangerous lean condition, then it's not a very robust theory for a bunch of GM engineers to come up with so I'm inclined to discard it in favor of a more rational explanation. Does HPT have a more complete explanation as to the purpose of this desoot mode? Myself, I'm not comfortable just turning off a bunch of stuff because it makes a specific problem go away. Everything is there for a reason so... what's the reason for this odd lean spike behaviour?

On stock setups it doesn't create a dangerous lean condition, in fact on some bigger truck engines like the GM 8.1L workhorse in a 32' RV, PE is delayed entirely for 5-10 seconds in some cases while at WOT, depending on load, cyl temp, etc. I think it's strange but it would never knock at WOT during this "lean" condition. Now if I put a supercharger on it, I may have a problem, but stock it's fine. Who knows, maybe they run it this lean simply to clean out some excess buildup in the cylinders or CAT.

I have also wondered why on some cars when I see them floor it, sometimes I see some grey matter almost looks like "soot" come pufffing out of the pipe for about 1 sec... it's not quite vapor and not quite black like a rich condition... i wonder if this is desooting.. I'll see it more on stock family type cars like 4cy and 6cyl SUV's and mid-sized cars when they are getting it on the hwy, this way I know they are hammering down, usually in very mild road rage - get in front of the other car type situations. I never see it on vettes, v8 camaro's, mustangs, etc. Or maybe it's just transient fueling gone bad, little rich and the cat is turning it grey instead of black.

[RRRocketMan]

Well I can certainly attest that both my 3.4 grand am gt and 3.8 grand prix gt worked just fine at stoich during wot. A little gutless but fine. I mean they are so low compression to begin with. But the Camaro is what... 10.7:1 ? A little on the high side for 87 octane and aluminum doesn't have the heat capacity that iron does so WOT transients create high temps faster with the high compression to boot. I'm sure it's not the end of the world if you get 3* of knock at WOT on an N/A LS3 but still. Bad idea for a Camaro and it's on by default.

Now we only have the makeup mode to decipher... and by we I mean someone else smarter than I am lol.

[sillycon]

What is this "makeup mode" you're referring to? A search on here only turned up posts by you asking about it. One of those posts mentions "stratified injection", but I'd guess Camaro's are still port injected (not DI) in which case stratified injection (injecting during the compression stroke) isn't possible since the valve on the intake port would be closed. E.g. "stratified injection" likely doesn't apply to you/your situation.

[RRRocketMan]

If you have a look on the same tab where the desoot mode is (I think), 3/4 of the way down the page you'll see "Makeup mode" and options for none single and multiple. Essentially this dictates whether the fuel injectors may fire once, twice or multiple times per cycle. Despite Camaros being port injected I suspect there may be some reason it's set to multiple by default... such as spraying on an open valve after it's already sprayed on a closed one, to create a gradient in AFR along the charge for whatever reason. This is what I want to understand better.

[sillycon]

Can you post a screen shot, preferably with the mouse over the setting so the "help file" text is displayed? Unfortunately, not everyone sees the same settings as different OS's have different things enabled/disabled even within the same ECM.

Off the top of my head (e.g. having to guess based on what's posted in this thread) I'm wondering if this isn't perhaps somehow in reference to the ignition coils instead of the fuel injectors -- multi-spark/multi-strike is commonly used to improve emissions at lower RPM's; over ~3-4k though it usually will get disabled automatically though as there isn't enough time to spark a second time (due to recharge time, etc.) if it didn't light off the first time.

[RRRocketMan]

Can you post a screen shot, preferably with the mouse over the setting so the "help file" text is displayed? Unfortunately, not everyone sees the same settings as different OS's have different things enabled/disabled even within the same ECM.

Off the top of my head (e.g. having to guess based on what's posted in this thread) I'm wondering if this isn't perhaps somehow in reference to the ignition coils instead of the fuel injectors -- multi-spark/multi-strike is commonly used to improve emissions at lower RPM's; over ~3-4k though it usually will get disabled automatically though as there isn't enough time to spark a second time (due to recharge time, etc.) if it didn't light off the first time.

sure
Untitled.png

[sillycon]

Interesting! I've not seen such behavior (as described) in an ECM before, and I can't really think of a reason why one would really want such a feature. That said, I wonder if perhaps it's a selector for sequential vs batch injection mode and it's just not labeled very well?

If you are able to log your individual injector on/off events, you can try changing the mode and capturing an idle/cruise log in each mode to see what impact(s) it has to your injector PW's/operation. Once there's an understanding of what it's doing to the IPW (hopefully it's a loggable IPW behavior, unlike desoot mode), then perhaps we can back-track to figure out what it's intent is.

Edit: I just realized -- I suppose such behavior might be beneficial for REALLY big and sloppy injectors like SD 220's when trying to get a car to start and idle. The issue, however, with using it for this would be getting good atomization vs getting puddling on the back of the valve.

[RRRocketMan]

Whatever its function, I think we have to start with the assumption that it is an OEM requirement for stock components. Large vehicles would have large injectors clearly but they would be scaled proportionally so that the safety margin would be in the same neighbourhood as a car with tiny injectors. You get the best IPW resolution (and therefore the best control over afr) when you use as much of the available duty cycle as possible (ie. max throttle uses 100% DC). Of course nobody does this because it leaves no margin for safety. However whatever the margin of safety is (say 30%), I imagine it's pretty consistent in the OEM world and idle should be tunable without the need to "make up" for sloppy control of fuel metering. I'm inclined to go with some sort of complex emissions model that tries to keep the cat happy or control cylinder temperatures (like EGR). How this is achieved with multiple injections remains unknown but I think it's plausible.

I wish I could log individual injector events but I've never seen that in the scanner.