I've been noticing a decent amount of N/A toyota minis are after firing on 22re's. How are they doing that? Straight pipes? My buddy has a straight piped 4x4 but it doesn't afterfire, anyone knows why?

 

Straightpipe or glasspack probably

 

Take the dashpot off and they all will...

 

Okay that makes sense, they just keep it from the throttle body shutting all the way right?

 

Let's it shut too fast...

 

It's an emissions thing not to keep the exhaust from popping. If the throttle plate shuts as soon as you let off the pedal it richens the mixture producing higher levels of NOx.

 

So the repair manual is incorrect in having it's user adjust the dashpot as a means to correct a back fire issue.....ok

 

I don't see how the dashpot makes a difference in backfires but it does make sense from the emissions standpoint.

I have noticed that any exhaust leaks before the muffler will induce popping on deceleration. If your system is sealed the popping will go away.