Cluch in = Drastic RPM Drop during DFCO

[GHuggins]

Kind of lost on this one - basically it only does this if it goes into DFCO - won't do it if you just push the clutch in no matter the vehicle speed... I have taken min air, adaptive idle, idle timing, idle timing correction, VE, MAF and the torque model out of the picture and while modifying these does help "engine no longer stalls" it still has an rpm dip as the engine goes back into closed loop and re-catches itself... I even thought I had it fixed when I changed my entry and exit spark tables for DFCO all to values of 20 - this is honestly the single best thing I did to aid it, but then I did a dyno pull which resulted in the engine holding back and going into DFCO for a longer period of time and the dang thing did it again...

Mods on the car are Tony Mammo heads, very mild cam with negative overlap, ported TB, 1&7/8" ARH's with cats, full exhaust, cai, yella terra valve train and LSA injectors... Main car setup is an 08 Z06 LS7 with forged internals - compression roughly 11.5:1...

Posting dyno pull with the issue, current tune and stock file...

AND by taking them "out of the picture" - I tried with adaptives 0ed out, min air raised to the point that it was pulling up to 10 degrees of timing to idle, idle timing - raised up to nearly regular timing table, adaptive timing - nearly 0ed out overspeed values... Wondering if anyone has run across a fix for this yet - best thing I did was raise entry and exit spark, but it's like it's not coming out of DFCO fast enough rpm wise - if that makes sense

[GHuggins]

I guess the simplest thing to test would be to raise the deactivation and activation rpm points and lower the crank reference periods to for re-entry? Still - I've never had to do this on one before, so kind of stumped on this one - may just be the cams very high LSA with the loss of low end causing the problem, but then again the compression should have made up for that - or at least I would think as much?

[GHuggins]

At this point I'll take some thoughts on the subject Tweaking DFCO and adaptive some more is all I've got right now...

Thank You

[Frost]

DFCO comes and goes and so does CFCO, and it has it's own spark modifier/adder.

Try these DFCO and CFCO settings.

NEW Engine NEW Heads - CoastDown3b.hpt

Huge plus; all the popping and banging and carrying on associated with DFCO will be 85-90% reduced from OEM for that platform. I hate that.

[GHuggins]

Thanks, I honestly wasn't even thinking about CFCO... I've already edited DFCO quite a bit more than the one's you posted - pretty much all popping gone, but didn't fix anything - even had it setup to come back out of DFCO a lot sooner, but no go... The rpm settings for CFCO correspond to when the rpms finally try to catch themselves - think I might even take it a touch further and go ahead and put a two step in - not that this owner will ever use it, but it would completely take this out of the equation...

Something interesting I discovered was the airflow limits for adaptive idle - no idea why changing the airflow limits changes the throttle actions - changed it from -8 max to +10 max like most modern setups and couldn't get it to idle down until the tires weren't rolling anymore - slowly walked it down to +5 and wound up with the idle going back as long as you would push the clutch in at a speed of 40ish and below - still drops to 500 then back to 1000 then back to 600 and back to 800 until settling at 700 if your running around 60mph and push the clutch in and hold it... I even put adaptive idle into the picture the whole time using only the airflow settings to control it - made a lot better, but still no go at 60+mph clutch holds... Throttle follower or nothing else helped - going to try CFCO - couldn't see the forest for the trees sort of thing I guess

Thank You - will try the CFCO tomorrow...

[07GTS]

i dont like CFCO but also dont understand it, i assume if u are rolling with clutch in there is no load on engine (just idling) so any fuel cut is just going to kill it..? so i disable it and also if im driving hard and miss a gear and it takes a little longer i dont want fuel cut to begin when i get back into WOT with boost, this is how i have my dfco setup and i also have fuel cut [ecm12265] above 4000rpm delayed 500 so if im at track needing decel i keep fuel in for cooling which i have noticed if it cuts fuel manifold temps rise quickly with the blower

[GHuggins]

Well, it wasn't CFCO either... Thank You everyone for sharing on this, but what I wound up doing since HPT doesn't have one of the tables causing my fits and per Jslic's advise was I fired up EFI Live and changed (B2415) - DFCO RPM Delta Exit - If the rpm rate of change is greater than this value then DFCO will stop - to 300 rpms instead of it's pre-programmed value of 1800... This got it back to regular fueling quicker and allowed me to make changes to the proportional, integral, min air, idle timing and coastdown timing tables... It's still not perfect - if I do a dyno pull now and allow it to hold back until it drops back to around 60mph and push the clutch in - it now drops to 500 rpms, but immediately returns to the set idle setting... I will try to get HPT to add this table even though I know it's already been requested - just on the to-do list I guess...

Funny thing is this stinking car doesn't seem to like being adjusted in any traditional method - taking away min air to slow down the drop, taking away idle timing and coast timing to slow the drop, adding proportional and integral to smooth it out and keep it from loping as bad - think I'm going to make a note of this OS, so I don't go round and round again... I also found things mislabeled and missing from the regular idle section - another thing I discovered in EFI that explained why changing the airflow max settings were causing such other "weird" problems...

[jsllc]

This is already on the request list and I have been told I should see it by week's end. I also have all of the speedo stuff for staggered setups being added. Once in I can give a complete list.