shooting ducks with E85

[ecorl]

Car is running good with one minor exception: A few seconds after i turn the car off I am getting one or two bangs out of the drivers side exhaust. It is running a little rich (E85) and the oxygen sensor is on that side. A little odd that it is self igniting like that. Any thoughts?

[BKBridges]

E85 has a lower vapor pressure than gasoline I believe... Too rich at idle = fuel in the exhaust when you shut it off. The mufflers get hot and the vaporizing alcohol lights off in the mufflers. Pull a bit of fuel at idle and see if it helps. Im just guessing as Ive never tuned an E85 motor before. Hopefully someone that has will chime in.

[Deaf Bob]

Run E-85 in our derby motor.. Runs cooler and stops quick.. No hesination like with race gas

[Cyclone03]

Are you controlling timing? It sounds like your getting a random spark after you turn the ignition off.
I'm sorry I'm no help for why,or what causes it.
I've also heard of an MSD causing that.

[ecorl]

OK, thanks for the discussion. I have done a little research and also providing more information that might help me get a handle on this. Its a blown application and I am using wasted spark type ignition. It is running rich at idle and the idle is probably set a little high (1500 rpm). I can back down the idle to around 1000 or so but once its in gear it suffers from blower surge and I dont want to go lower than that for street use. I can lean the idle out some for the street but have to keep it rich for the track. This is because I am injecting above the blower only (no port injection). So, on tip-in, there is a momentary lean condition in getting fuel from the top of the blower into the cylinders. Timing is fine but the fact that I am using wasted spark could be contributing (just guessing). If I lean the idle out and bring the RPM's down it should help.

[Cyclone03]

I have never tuned a blown engine so take this for what it's worth.
I think if you add some base timing that will take some heat (EGT) out of the turbine that should also allow you to lean the idle mixture and lower the idle RPM calming your surge .

I also think if you add the engine is blown in the title above you'll get more action on this thread.

[BKBridges]

Not wanting to beat a dead horse, but... adding port injection would allow you to tune out the surge and the ducks. With the new LS7 style injectors you can squeeze port injection into almost any space.

[dieselgeek]

First thing I'd check is that your ignition coil power is controlled by the Fuel Pump Relay output of your ECU. Otherwise you might get an errant spark on shutdown. After that, maybe test a shutdown by killing the fuel like a mechanical system (injector power interrupt switch) and see if the problem goes away. The guys at BES said that O2 sensors will light residual fuel in the exhaust, I wasn't aware they got hot enough to do that though.

[ecorl]

Scott,

I am running MSII for fuel only. Electromotive is running the coils. Peter is selling me hard to control everything by the MSII and we may make that our winter project. Anyway.....you may be onto something with the BES theory. The after shutdown pop only happens on the bank with the o2 sensor! I may unplug it on the next start and see if it goes away.

[dieselgeek]

Be sure to test by killing just ignition, then just fuel, as well. I still doubt the O2 theory but knowing you are running a separate ignition, I bet you are getting an errant spark (trigger).