So I've been chasing a high RPM random miss for about a year, and today after installing a new set of 83# injectors from Jeff Stevens, I decided I'd try my alcohol injection system that I built as as well.

I put the fuse in, a 30# NOS jet in the alcohol injector nozzle, and upped the timing tables from 20 to 24.

The miss, for whatever reason, got a little better. I upped it to 28 degrees and the miss went away.

To make sure it wasn't related to the alcohol itself, I pulled the fuse, went back to 24 degrees, and it was still pretty much gone, especially compared to what it was at 20 degrees.

Does this give anyone a hint as to what might be up with the motor? Since I'm running a hot 12psi non-intercooled, I had to back the timing out to 20 degrees to avoid any knock retard. But that seems to cause my motor to miss.

Other details: 396 LT4, 210cc AFR heads, 238/238 cam, S-Trim

Thanks,
Dave

 

Really? No one has an idea? Everyone on vacation?

Ok, how about this: 20 degrees BTDC is closer to TDC than 28 BTDC, so the cylinder pressure at 20 is a lot higher than at 28, and if you have a marginal ignition problem, it might not be able to fire across the gap under boost at 20 BTDC even though it can at 28 BTDC.

It's not a forum if I'm talking to myself :-)

 

Yes retarding timing to much can cause problem. Friend with a BIG nitrous motor had to go to a crank trigger set up to avoid the possibility of misfire/arching cyl when pulling timing out with a multi stage kit. However, 20* should not be a problem at all other than maybe giving up a few hp- many of the guys over at turbomustangs.com are in that area.

Matt