What is generally the cause of part-throttle intake backfires?

I did a bunch of mods this winter detailed in my last post this section.

One such mod was an elite engineering oil catch can plumbed inline into my PCV system. Open breathers on valve covers. There is a check valve to prevent backflow into the crankcase during boost.

The goal of the catch can was to catch any oily crankcase blowby vapors that could be sucked into my engine during either part-throttle (hopefully theres not a lot then) or right after boosted operation (some blowby is going to occur no matter what). The goal is to keep the heads clean.

Anyways, I will get an occasional part-throttle backfire. Its kind of goofy because it sometimes will generate enough pressure to engage the meth/water system.

Any idea if this could be related to the catch can? My theory is that the can is succesfullly catching 'heavy less volatile oil' and letting light 'more volatile' fuel vapors (from blowby) go back into the intake.

Since the heavy, less likely-to-combust oil is no longer diluting the fuel vapors, its more likely to ignite when it hits my intake.....

 

I'm running the Rx catch can (blower design with 3 lines & 2 check valves) and no issues with intake backfires. Might give Tracy (user name SC2150) a message; he's a catch can expert.

 

I did some more digging into my issue and I dont think its caused by my catch can (duh!).

I had to modify % throttle position for PE in my computer table for my 93 (vette) ECM.

I had to make it come on at say...50% throttle at 2400 RPM and up.

Essentially I was making 4 psi boost at 2400 RPM and it was getting lean enough to cause a backfire / stumble / detonation? event as my computer was still trying to make 128 on the BLM's.

This used to not be an issue as I had meth/water system come on as low as 2.75 psi boost (the meth would act as a fuel). However, now it doesnt come on until 4.25 psi boost.

So 4 psi boost and not enough fuel = lean out