jeepguy553

I am looking through my logs and I can't find the one single backfire I got today. I was tuning...of course...SA and it popped through the TB. I can't find it. I have been looking for sudden drops in MAP, but that's about the extent of what I know to look for.
Any suggestions?

Grumpy

At a ALDL sampling rate of 160 baud it's unlikely you will, and your looking for high spike. It's not too hard to hit 120+ K/Pa with an intake backfire. I just happen to have caught one with a 2 bar MAP running one time.....

funstick

just something to think about. ive had this 383 with a humoungugs cam ive been dicking with for about 3 weeks now. that had a bizaree pop back into the intake when hot. turned out that the swiper arm on the TPS was rubbing up against the accel 58mm tiwn TB and was hanging at 2.5 volts. and if you snapped back into the throttle for a shift you would miss it in the data logs. the only way i cuaght it was by revving the engine with hard throttle snaps when i noticed a streak in the body of the TB its posiable if its intermitent you could have a mechanically bad TPS that has a good sweep but sticks for very breif periods of time.

jeepguy553

I'll check the TPS tomorrow. thanx!
That's what I was looking for...a spike over about 80kPa. I found one at about 70kPa, but the TPS wasn't where I thought it should have been since I had the engine at about 2200 rpm and the TPS should have been at about 10% give or take a few %.

JPrevost

You won't find a backfire in a log other than TPS movement with slow RPM increase.
Lean backfire is a fuel delivery issue. Too lean and it'll backfire. It happens more frequently with TBI than port injection because of that stupid transport time issue we have .
Don't forget the AE is based on injector on-time so fuel pressure and injector size aren't considered. It's a good idea if you have larger injectors and/or more fuel pressure and/or larger intake volume to start with stock AE tables.

jeepguy553

Okay...
I wasn't really tuning AE yet. I have PE/WOT mode set for 80% in the BIN right now so it WON'T set PE for the time being. I have yet to get it past 50% TPS. I am not really sure what my AE table is...probably stock since I haven't messed with it yet.
I guess I am just gonna have to take really good notes and be on the watch for a backfire. It is lean at several points in the VE1 right now and I am currently ironing that out.
I may play with it again today and let you know what I get. I am thinking that it isn't gonna be happy with a 128 BLM in that RPM range.