Nitrous question and backfiring problem!
Thread Starter
On The Tree
Joined: Apr 2003
Posts: 165
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From: Houston, TX
Nitrous question and backfiring problem! Some basic info on my car:
The complete list of mods are in my sig. But this is basically a Stage II H/C + Nitrous car, dynoing 412 hp/373 tq NA (13.0:1 A/F), and 513 hp/521 tq 100hp N2O (11.0:1 A/F). Here's the dyno:
<img src="http://temp.corvetteforum.net/c5/dsk888//dyno_02-15-03.jpg" alt=" - " />
Question #1: The 11:1 air fuel ratio on the nitrous run was obtained by using the #52 nitrous jet and the #31 fuel jet provided by NX. Depending on which chart you have, it will either recommend a 52/31 combo or a 52/28 combo for the equivalence of a 100 hp shot on the C5. I have since ordered and replaced the fuel jet with the #28 size, since the A/F ratio is a bit on the fat side. How much leaner did I make it? Is it safe to run before being able to get her back on the dyno?
Question #2: I've just recently given her a much needed oil & spark plug change. Because of the calculations used for gap measurements (.004 per 50 hp, subtracted from .060 stock), I left the stock TR6 gap of .035 alone, even though they were more like .038. After going for a test drive, I got a pretty good kick from the juice, but also a bunch of backfiring. Pop pop pop pop......all the way through the rpm range. I have experienced this once before, but the issue was addressed by my tuner, and fixed at his shop. I have consulted the tuner with this matter, and heinstructed me to make the gaps even smaller, more like .032-.035. What are the effects of changing the gap size? And are there any pros and cons in going smaller?
Thank you for your help! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
<small>[ April 21, 2003, 03:48 PM: Message edited by: dsk888 ]</small>
The complete list of mods are in my sig. But this is basically a Stage II H/C + Nitrous car, dynoing 412 hp/373 tq NA (13.0:1 A/F), and 513 hp/521 tq 100hp N2O (11.0:1 A/F). Here's the dyno:
<img src="http://temp.corvetteforum.net/c5/dsk888//dyno_02-15-03.jpg" alt=" - " />
Question #1: The 11:1 air fuel ratio on the nitrous run was obtained by using the #52 nitrous jet and the #31 fuel jet provided by NX. Depending on which chart you have, it will either recommend a 52/31 combo or a 52/28 combo for the equivalence of a 100 hp shot on the C5. I have since ordered and replaced the fuel jet with the #28 size, since the A/F ratio is a bit on the fat side. How much leaner did I make it? Is it safe to run before being able to get her back on the dyno?
Question #2: I've just recently given her a much needed oil & spark plug change. Because of the calculations used for gap measurements (.004 per 50 hp, subtracted from .060 stock), I left the stock TR6 gap of .035 alone, even though they were more like .038. After going for a test drive, I got a pretty good kick from the juice, but also a bunch of backfiring. Pop pop pop pop......all the way through the rpm range. I have experienced this once before, but the issue was addressed by my tuner, and fixed at his shop. I have consulted the tuner with this matter, and heinstructed me to make the gaps even smaller, more like .032-.035. What are the effects of changing the gap size? And are there any pros and cons in going smaller?
Thank you for your help! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
<small>[ April 21, 2003, 03:48 PM: Message edited by: dsk888 ]</small>
TECH Regular
Joined: Feb 2002
Posts: 454
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From: RTP, NC
Re: Nitrous question and backfiring problem! That popping out your tail pipe is because of a few things:
1) too rich
2) timing too retarded
3) gap too small
When I installed my TR6s last weekend, they popped at first, but then I advanced my timing a few degrees and it went away.
1) too rich
2) timing too retarded
3) gap too small
When I installed my TR6s last weekend, they popped at first, but then I advanced my timing a few degrees and it went away.
Thread Starter
On The Tree
Joined: Apr 2003
Posts: 165
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From: Houston, TX
Re: Nitrous question and backfiring problem! Yes, that was my initial guess as well. But I called Mr. Mike Norris (my tuner) about the symptoms, and he instructed me to gap even closer, like .034 to be exact. I was at the stock gap for the TR6 plug, which is advertised at .035. But in actuality, it was closer to .038 according to my gapper. I pulled the plugs tonight, and regapped them at .034 on the dot. Went for a test drive, and PROBLEM SOLVED!!! I got sideways in 2nd and 3rd. I couldn't believe it actually worked. So I tried it again. But this time, off a roll at 3500 rpm in 3rd. And....INSTANT SIDEWAYS, hammered it in 4th, and took her all the way to 5k without a hint of backfiring or knocking.
It's amazing, but how the hell did Mike know, I mean, EXACTLY where it needed to be??? <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Thanks for the help! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
It's amazing, but how the hell did Mike know, I mean, EXACTLY where it needed to be??? <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Thanks for the help! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Thread Starter
On The Tree
Joined: Apr 2003
Posts: 165
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From: Houston, TX
Re: Nitrous question and backfiring problem! No, I didn't disconnect the ECU. But since it's working fine now, I guess I should just leave it alone. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Teching In
Joined: May 2003
Posts: 6
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Re: Nitrous question and backfiring problem! Definitely blowing out the flame, I would invest in a multi spark box in a hurry.
By taking a couple of thousandths out of your gap fixed the problem?
That issue will be back in a jiffy!
Plugs wear quick in high stress situations.
By taking a couple of thousandths out of your gap fixed the problem?
That issue will be back in a jiffy!
Plugs wear quick in high stress situations.
