Nitrous backfiring on my CRX

I have a CRX with a SOHC ZC with 50 shot NX wet kit. The car has been running perfect even with the shot for the past two months. Lately it has been causing an explosive sound once I spray on third gear. I assume it to be backfire. The engine still runs smoothly though. No codes. Some have said the cat converter is damaged, there may be a hole in the exhaust or fuel is to rich once activated. I've checked my A/F gauge and it reads normal, not too rich/lean. I've retarded the timing 2 degress and the colder spark plugs show no signs of trouble internally. I'm not sure where the problem is. Any ideas will help. Thanks

The loud noise is comming from the exhaust right? not the intake? What kind of bottle pressure do you have? If it is too low it can cause some backfire unless you down size the fuel jet.

It is coming from the exhaust. The bottle pressure has been below 900psi so I'm guessing the fuel mix might be too rich. Causing the backfire. I have sprayed at about 800psi a few times and never had the problem. I don't keep the bottle heated all the time cause the NX heater requires the bottle to be open to regulate the pressure. It's warmer outside now so the bottle stays at about 850. I guess now I do have to keep the pressure at 950 to prevent this. Do you know of other problems that might cause this besides the rich fuel mix ? Down sizing the fuel jet seems risky, but if you had experience with downsizing the fuel jet, I'll try it out.

You only need to down size the fuel jet if you have really low bottle pressure. 850psi is still safe to keep the same size jet as on the chart. Below say 800 or 750 I would start down sizing the fuel jet, or increasing the size of the nitrous jet, but this would require a lot od different size jets, so I would just suggest keeping the bottle pressure up with the bottle heater. Even though it is warmer out side the bottle will cool down when in use so a bottle heater should be used when you are using the kit as well.

I agree with you on the bottle pressure. The only thing with NX is that the bottle has to stay open during the time it is being regulated for pressure. I had a shop tell me that I should only open the bottle when ready to use, not keep it open all the time due to small leaks in the lines and just the hazard of having a pressurized line all the time. I rarely use nitrous on the street, but there are those times when I wish I had full pressure all the time. Turbo rides are no problem, but if the pressure was up, it would be a better spankin. I'm thinking about trying the ZEX heater. That one does not require the open bottle. So that might actually help on optimal pressure all the time. Thanks for the help.

I have the zex heater and I like it. It just regulates the temp, and not the pressure. But keeping a steady temp will keep a steady bottle pressure until you get really low on nitrous.

Well, nitrous is still backfiring even with the correct pressure. My next guess is the ignition is not powerful enough once I hit the gas. What do you think about using an aftermarket ignition system such as the MSD Digital 6 ? I called NX, but they already told me what I know. I think a better spark will do the trick.

I was also looking at one of my old posts, and you had mentioned just using the coil and cap for the 50 shot. How does that work without using the the full system ?