Surge at idle after E85

[Lakegoat]

E38, 5.3 with Whipple 3.0, 235/250- 115 cam. Starts great, idles great at startup, after a little warmup, I revved it a few times and it went into surge city. When on 93 octane, it would drop to idle.
First log is immediately after filling with E85(71). Ends in 25.hpl. It was pretty rich---thought it would be lean with 85. At the end of the log, I stopped to turn off the scan and just as I stopped, it started surging.
I changed the VE table to lean it out and the second log (E85)is sitting on the rack in my garage. Refer to first sentence.
I thought I was thru with this---almost. Need to go to the track.
Thanks

[edcmat-l1]

You have an overactive throttle blade and under active timing control. You need to pull a stock file off the repository and put a bunch of stuff you've changed back to stock.

ALL of the idle adaptives and ALL of the idle airflow tables besides BRAF need to be returned to stock. Much of the problem lies in those changes.

You need to raise the idle area of the high octane table. With your idle spark set at 18 degrees and the high octane table at 22 in the same area, caps you to 22 degrees timing. In other words, if you're targeting 18 degrees and your under-speed spark table wants to add timing, it can only go as high as the numbers in your high octane table at the same rpm and (g).

[Lakegoat]

Got it. Be back later. Thanks

[Lakegoat]

Starts and idles good, even with the lower BRAF. Goose it and let off---throttle drops one time and recovers, but it almost dies when it drops. Got an idea for that one little #^%$%$$

[hjtrbo]

Good quality log, can you re-do it with engine torque and idle adapt added. +1 for putting all throttle settings back to stock as Ed said. For me, usually min air and airmass A will fix this up and maybe 1 or 2 other tables.

[hjtrbo]

Try this

[Lakegoat]

Thanks! Here is result. Still drops to almost 400rpm and then comes back after rev.
Scan attached---I added Engine torque and Idle adapt.

[ns158sl]

Are the idle airflow PIDS available to log? Integral, prop, throttle follower? I would log desired idle speed you can Math the error and see where prop or integral is adding/pulling too much. If you are in a rush you can always hack the minimum airflow table to get by until you can actually figure out the rest. Also log pedal position so you can see TF in action better.

[Lakegoat]

Don't know if I can log the PID's. I added the idle speed and pedal position. I will do another scan tomorrow morning.
Thanks

[hjtrbo]

What's the go with the oscillating at the start, no way that was on it's own...?

Back out my throttle follower changes next time you're out. Your engine torque is a smidge on the high side but not crazy.

[Lakegoat]

The oscillating starts after I give it a rev. Rev---let off the pedal---oscillating (1) starts.

[edcmat-l1]

The OE file I have says your adaptives are all modified.

As for the dip after the throttle blip, just add a bit to your BRAF. Your BRAF is 11.1 g/sec @ idle but you're idling between 11-12.8 g/sec dynamic.

See if this is any better.

Why do you have it idling so high?

Camaro SS EH1 BRAF TH FOLL_EH1.hpt

[Lakegoat]

I pulled file from the repository. Must not be stock---I used a 2012 Camaro because it is not even close to a truck setup any more.
Probably a mistake?
I set the idle for initial startup and haven't changed it.
I am going to load the tune that you sent and see what that does.

[Lakegoat]

Still has the big dip in rpm after a rev. Just before the dip, there is a drop to neg numbers in spark. Where is that coming from?
I reduced idle to 700 and that was too low. I settled for 800rpm and it seems ok.
Scan 3 is 700rpm, Scan 4 is 800 rpm idle.

[edcmat-l1]

What injectors are in it?

[Lakegoat]

Your Favorite



Bosch 210's
Don't quit on me now

[ns158sl]

Ah yes, thee ol natural gas injectors lol

[edcmat-l1]

Your Favorite



Bosch 210's
Don't quit on me now

That's part of the problem right there. Low pulse width control. It's overly rich for a few seconds when the throttle closes.

I'm impressed with how tight the trims are though for the most part.

[Lakegoat]

I went back to the repository and got a 2012 Sierra file and downloaded the adaptives and idle spark tables. Same problem.
Its weird that 93 octane didn't give me problems. Sending e mail

[JLawson240]

Jumping into this thread to tag along. Idle surge after switching to E85 seems to be an issue across platforms.... including my 2012 Coyote. I've gone after the surge some on mine with the idle airflow mult tables, torque tables, and a million other things including the PID idle controller although it's settled down quite a bit I just can't seem to eradicate it...

Seems like it has to be related to combustion of the fuel itself somehow and maybe a slight difference in torque delivered?? Could it have something to do with the transient fuel tables and the differences between gasoline and ethanol and how they stick to and evaporate off the port walls? Am I crazy?