well i have a 93 honda prelude the block has been sleeved and i have forged pistons and rods the compression is 9:1. i have about a 150 shot of nitrous i have a .56 nitrous jet and a .31 fuel jet. and i am not sure what is causeing it but latly when i am useing it, it will backfire throu the intake if anyone has any help i would be very greatfull.

 

This ones yours NirVTEC

 

Im gonna go with timing.... altho I have never used nitrous so I not sure. But something tells me it might be timing....

 

There is a possibility fuel pooling in your intake manifold that explodes and goes backward when you let off the gas.
I had this particular issue when my Nitrous solenoid was on its way out. How old are your solenoids? Have you rebuilt them?
Curiously, have you been on the dyno to see how your AF Ratio is? I also suspect you're just dumping too much fuel.
How does it perform before the explosion? Mine was lagging because it wasn't letting enough nitrous through, thus causing a very rich mixture.
(Imagine having a Nitrous jet meant for a 35 shot with a Fuel jet meant for an 80 shot)
What is the condition of your spark plugs? What heat range are you using?

I got lucky with NOS brand jets because when I used the 75 and 100 shot combo they provided me, I had an almost perfect 12:1 AFR on Nitrous after we tuned it to 13:1 on motor.

I also have to ask, are you staging your shot in any way? I can't imagine using a 150 shot with anything short of massive slicks.

What are you using to tune your car as well, and does it tie into your Nitrous? I was old school and used a VAFC to tune N/A and an MSD dig6 for timing retard.

 

well the puddleing fuel sounds about like it cause it isnt till i let off the gas the nitrous is on a full throttle switch but i am stageing and not useing till at least middle of second gear. i have not made it into the dyno yet really want to but just havent had the time yet finishing work on a house just bought for me and the famliy. and i found a nitrous calculater is how i worked the jets looked and looked couldnt find a table for jet sizes that is consistant. but i put in my fuel pressure and nitrous pressuer and what size nitrous jet and it said i should be useing a .31 on the fuel. and it should be a 140 shot basicly and 120 should get to the ground. but till i let of the gas a lil the nitrous seems to work great get tones of power and then let off a little to shift and i get a load pop and pull over and have intake and vacume lines blown off .

 

Get to a dyno....
My friends was doing the similar thing before he found he had 10.5:1 AFR, and it wasn't making NEAR the power it should've until they cleared that up.