Sorry this is so long, but maybe it will save someone's engine.

This weekend was going to be my first 3 day weekend on the juice. BUT last time I ran 2 weeks ago I had a back fire on my last run of the night - and got my *** beat in the finals. Any way didn't think much of it as everything ran fine. No SES lights, oil pressure problems. I had only about 8 runs on the 15 lb bottle

This last Saturday I had 2 more back fires. Than the car starting acting 'funny'. Again no SES lights, no outward sign of a problem. Again got beat due to no being able to finish the run. Only had 3 NOS runs - now a total of 11 runs on 15 lb bottle. -- Yes I purge.

Sunday morning. The SS wouldn't even run right, continued to die. I took the lid off (I run the SLP 85MM MAF - with MAFT, etc) and there was the screen - one big ball of metal. The MAF is shot. Took the ball of metl out, ran but continue to through SES lights for local MAF voltage, mis-fires etc.

I asked one of the local gurus on NOS. He weighed the bottle (15lb bottle). 4.2 lbs left. I was running 950+ psi. I THOUGHT no problem. Wrong. The problem was that the fuel was continuing to be pumped into the T/B but no or very little NOS. Than a little NOS and that created a back fire - a GAS back fire; thank god not a NOS back fire.

Monday I put the stock MAF back in - no NOS runs for me (was already in the middle of a great run on victories N/A).

I'll order a new SLP 85MM as my times were great. But I will never run more than 8 runs on a 15 lb bottle again <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

Again sorry so long, but your comments are welcome.

Thanks

David

<small>[ May 27, 2002, 09:36 PM: Message edited by: Navy David SS ]</small>

 

Look elsewhere. Something has to ignite the fuel in the intake. It just dont combust for no reason. Just like a N2O backfire, something has to set it off. I run raw fuel through my intake alot to clean out the oil that builds up and havent had any problems. I also had the same thing happen as you my last run at the track. Ran all fuel and no N2O (didnt know bottle was all air and no N2O <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" /> ) Didnt hurt anything, but turned off the spray and ran over a second faster <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> 13.9 N2O to a 12.8 N/A <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Find what set it off in the intake.

<small>[ May 27, 2002, 09:47 PM: Message edited by: Country Boy ]</small>

 

Perhaps your intake valve is open when the spark plug fires. Since the exhaust valve being open is the leading cause of back fires, it seems to me that the intake valve being open would ignite the gas from your wet kit in the intake. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
That might cause what you described.
Maybe you should check your Cam and/or how it is degreed.

<img border="0" alt="[guns]" title="" src="graemlins/gr_guns.gif" /> GO ARMY! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Thanks guys. Still haven't figured out the problem. I put the stock MAF back on. Had to run N/A last time out. Tomorrow is another race day. We'll see how the stock MAF does. I have both a Z06 85MM and another SLP 85MM MAF on order. Maybe I can do a little 'at the track' comparison.

My engine is totally stock-so far. I hope it wouldn't be the cam.

I have been reading that it is possible that you can run too rich that may be causing the backfire/denation.

Any ideas?

Thanks

David