Post Stall Airflow

[macca_779]

Ok guys just a question on what the your thoughts are on this.

Say your stall an M6 LS1. From what I have found without turning the ignition off my IAC is not parking to a position open enough to allow for a seamless restart like when you would normall shut down the engine. Normal Hot Start and Cold Starts are fine but if you stall the car and try and kick it in the guts straight away it struggles without giving it some throttle.

So any ideas from guys that may have solved a similar issue or have ideas on where to work would be good.
I did drill my TB to improve this issue but its not as good as I would like it to be.

Cheers Macca

[joecar]

Do you have some logs showing IAC position/counts when this happens...?

[macca_779]

Do you have some logs showing IAC position/counts when this happens...?

No not yet Joe as its just something I thought of finally fixing right now. Its the kind of issue that doesn't bother me to much as I don't make a habit of stalling my car. Just something i'd like to understand a bit more to possibly fix it. I am assuming that the IAC is not parking as this is the only credible reason I can think of to cause the problem. Like I said. If you turn the car off its fine. But try and restart without power cycling the PCM and its no good without throttle application.

[edit] just a thought that popped into my head. Perhaps I'm relying to much on my parked position airlflow for a normal start and could possibly reduce that and offset it with more in the cranking areas. What do you reckon?
Currently commanding about 6.0g/cyl in B4343 at 80c+ and 30g/cyl for parked position airflow.

Would say 30g/cyl for B4343 and 6g/cyl for parked pos airflow work. I think it might make things a mess and I'm just thinking out load here.

[krisr]

Holy thread dig batman...

This exact same thing happened to me the other night so I thought i'd see if it was a once off anomaly, well I could reproduce the post stall difficult restart. I thought it was IAC airflow (ETC in my case) that was causing the problem as you'd give it a fraction of pedal and it would fire straight away, but after deliberately stalling my car during a log and trying to fire it back up again showed my IAC/TP position to be correct but the cranking pulsewidths to be abnormally large which would make sense as it needs the extra air to fire it.

It's a COS 04140003 running OLSD, logfile attached: 16149

Frame 87 - normal startup, PW ~5.7ms for short crank / 10.6% TP or 134 steps
Frame 193 - deliberately stalled motor (did NOT power cycle the car)
Frame 280 - tried to restart, PW ~8.7ms when cranking and took a few cranks / 10.6% TP or 132 Steps
Frame 371 - keyed the car off
Frame 400 - keyed the car back on, PW ~4.9 for short crank / 10.6% TP or 132 steps

The only PID I didn't log that could be relevant is volts but if anything the voltage should be the same for each crank/run event. Any ideas or anyone come about this before?

Kris

[krisr]

Just bumping this as yesterday I stalled the car a couple of times by mistake and exact same restart nature - high cranking PW which takes the car longer to get running without any throttle. Would be great to know if this is a bug in code or just a simple tuning issue.

[krisr]

Going to give this a bump to the top - is there any chance this can be looked at? Stalling in traffic = outright dangerous if it doesn't want to restart / floods...

[joecar]

Throttle cracker/follower, and idle desired airflow...?

Post logs.

[krisr]

The problem isn't stalling from airflow or coming to a stop and it stalls, as a matter of fact the car drives absolutely brilliantly and the cracker/follower settings are literally perfect for my engine combo, it's restarting the car after the occasional stuff up taking off from the lights (M6 transmission) is what I mean by stall.

Post #4 is the log/description of the issues when restarting - i.e. INJPW is massively larger than a key off/key on cycled restart. Throttle position (car has an ETC)/step count appears to be much the same for a normal start and for a stalled restart, but the fuelling is the issue from what I can see.

Will attach tune shortly - need to fire up laptop.

[krisr]

Tune attached - it's also worthy to note that the tune is largely based off the 2006 CV8Z Monaro stock tune as the car is a CV8Z Monaro with an LS1 and DBW. VE table left intact :rotflmao:

16633

[joecar]

Is the CPP switch working correctly...?

[statesman]

I think I might flog your VE table. :laugh:

[IJ.]

I think I might flog your VE table. :laugh:
Made me LOL for real :D

[joecar]

ROFLMAO :rotflmao:

[joecar]

( sorry, we're laughing because of another thread )

[darcy]

Is the CPP switch working correctly...?


I don't think we have CPP switches in Holdens, Joe.

[joecar]

I don't think we have CPP switches in Holdens, Joe.That explains the P/N idle airflow table being zeros.

[krisr]

I'd need to stick my head underneath the dash, but from memory there's 2 switches on the brake pedal but yeah, i'm not sure if we have a CPP switch. I can start the car without having to press down on the clutch pedal though and can't find any "clutch interlock" setting in the LS1B like in the later L98's. Whether starting without clutch in is normal or has been altered via Tech2 I couldn't say - I might post up the question on the local LS1 board. But for curiosity, would a CPP command 2 different mixtures for cranking? I wouldn't have thought so, because when you key off then key back on, it'll start normally with correctly commanded INJPW.

[joecar]

I forgot that GMH cars don't have the CPP switch.

No, not for cranking, but two different columns for desired idle airflow.

[5.7ute]

If you look at the commanded AFR in that log. The first start is at 23.5:1 until the engine fires, then follows commanded or thereabouts. After the stall restart attempt, AFR is at 23.5:1 for around 2 or 3 frames, then jumps up to 11.5:1 AFR, becoming too rich for a clean start. Hence the jump in IBPW.
Not cycling the key obviously doesn't follow the standard start routine.

[krisr]

Yeah, and that is the issue i've found - if you're in traffic and you stall the car at the lights (when I had the old Textralia Z-Grip, it wasn't abnormal without some revs onboard...) you could end up in a hairy spot and instinctively you wouldn't cycle the key you'd just be trying to get the car going again - one thing that I may do as an experiment is flash back the stock Holden tune and plug back up the MAF to rule out a COS issue as I've been through the tune many times trying to see what could possible cause the commanded PW to increase like that with no luck - perhaps the devs could chime in here if the source code is still available?

Does anyone with an LS1B / 04140003 COS3 / M6 combo in a position to log a stalled restart too? It may help localise the issue to either a potential COS bug or tuning (user) error.

[darcy]

I've got that krisr. Vz Crewman M6, running 04140003.

Can't say I've ever run into a problem restarting - and I do stall it a bit trying to be quiet and lazy with the throttle in the driveway - though I do sometimes get a Service Vehicle Soon message when it stalls.

[krisr]

Yeah I get the SVS message on occasion too when it cranks for longer than expected. Would you be able to scan your car by chance and check what the commanded AFR and IBPW under a normal crank/fire condition and a stalled/restart condition? Am very curious if what you see is the same with regards to those 2 PID's. When you try to restart your car, does it take a while to get going or just fires straight away?

[5.7ute]

I can do it in a different COS, but I do not think it will be down to an issue with any COS. More a standard routine.
A patch may be to "RAPE" the VE table/ maf table & commanded AFR cells used in the restart, as these will not be hit during normal driving.

[5.7ute]

Also log GM.INJFLOW.

[krisr]

I hate this car ... other than the fact the rear springs (Pedders XA Coilovers) have sagged and are ~1" from the bumpstops at full adjustment ... but I cannot replicate the large IBPW on a stalled restart now, I tried atleast 4 times, cold and hot. It fired perfectly each time - suggests to me it's most likely a user error rather than software issue. I may have to do some comparisons against the tunes from the 19th Nov till now and see what i've changed but god damn i've got alot of tunes to sift through as I typically save a new file each time I make a change :(

If I can pinpoint it, i'll update the thread as being a supporter of opensource I don't mind sharing, even my VE table - sorry, had to :D