Here is my setup:
AEM CIA, Apex'i dunk cat back, stock exhaust manifold, no cat, timing is at 16 btdc.

This thing backfires when I upshift, downshift (but not as much as up), and when I let off the throttle and get back on. My compression is in spec, the fuel pressure is in spec, the plugs all look perfect. What could be causing this. I think I might have an exhaust leak where the manifold mates to the head. Could that cause it?

thanks for any suggestions...

 

Im just trying to help,so correct me if im wrong.
im not sure about it but i think backfiring is caused by unburnt fuel in your exhaust system.

Simon
Red ITR 98
#04022 http://www.live2cruize.com/Members/Pages/Simon.htm

 

I would have to agree with you on that.

But how do I get that to stop? Are the valve not seating right or could I be running to rich? I'm using 93 or 94 octain fuel... anything less and I pig. But if it was too rich wouldn't spark plugs show this; same goes for it being lean, the spark plugs should show this. Right?

 

Sometimes a loose seal at the donut gasket can cause sounds similar to back firing. You mentioned you have no cat. Are you running a test pipe? Whatever it may be I would check the connection at the collector, make sure there is a good seal and the bolts are tight. It might be a good idea to check the rest of the exhaust joints as well.

 

are you sure it's not just the normal burbling/popping an aftermarket exhaust gives? My comptech would make some pretty cool noises, mostly when it was cruising in a low gear at mostly constant revs, little variations would give some nice pops (deep in a comptech though).

 

I can feel it in my feet... I know the sounds you are talking about. It's definatly a backfire.

I will check all the gaskets... I may as well just replace them all. I do have a test pipe in, made by midas.

 

I think I know which part I'd check first.

 

lol...I have a test pipe and my car farts a whole lot, I love the sound of it...lol

 

Midas made you a test pipe?!!

Is this a race only car? Cuz they can and should get in a shitload of trouble for that if you're streeting it..

 

Very unusual of them...

 

They made it... they didn't install it. I did that.