Long post but please read/help:

I have a '99 JDM R engine with ~18k miles. Stock except for the JDM header, Icebox and Comptech filter I just cleaned and a Comptech exhaust. At high rpm's (8200-8400rpm's) I hear a popping noise from the car. Sounds like it's from the exhaust but not sure. I just started getting that sound about a week or two ago. At first it was with the JDM ITR ECU and now with the Mugen ECU. Is it detonation? I have a Halmeter a/f ratio meter and at 8200-8400rpm's it is showing that I'm running rich. I also run 93octane gas. (maybe it's bad gas? I usually use Chevron but I used Citgo this last time)

Here's what I've done so far:
I recently changed out the cap and rotor (OE Honda parts). I've done this twice before so it's nothing new to me. Could it be my wires are bad? I just ordered some NGK wires so I'll be replacing my old Magencore wires that were from my old GSR set-up. The NGK iridium plugs are a couple months old. When I pulled them out they were white on the top part above the electrode. Could that mean I'm running lean? The rest of the plug is black like I'm running rich. I put my B&M FPR back on and raised the pressure to 46psi, still within stock specs but at the high end. I also added 2-3% fuel on my VAFC from 7k - 9k rpm's. But I am still getting the popping noise.

I also checked my timing and I have it at 16 degrees, per specs and I did a compression check and I got 220, 220, 210, 210; still strong across the board.

Just a little while ago, I put my JDM ECU back in, reset my VAFC and added about 1-2% fuel from 7-9k rpm's. I ran the car and I'm not getting the popping sound anymore.

I've run both ecu's before with no popping so I want to know what could be causing this problem? I'd like to use the Mugen ECU for track days but if it's potentially a danger to my engine I'd like to know why and fix it.

Thanks for any help/suggestions. Let me know if you have any other questions about my setup and what I've done.

 

possibly the gas isn't burning competely in the combustion chamber and the excess gas is burning in your cat/exhaust pipes.

(above statement isn't for detonation)

edit: the sound of detonation sounds like ball bearing dropped on a dish.

 

Thanks for giving me an idea of what detonation sounds like. I've never heard it before so any wierd sound coming from my engine/car makes me nervous.

So what do you think I should do to correct this if it excess gas? I was getting the popping noises before I made the changes to the fuel pressure and the VAFC.

Thanks!
Gary

 

anymore suggestions?

Thanks!