PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

NO2 Backfire

Old Mar 22, 2009 | 05:31 PM
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Default NO2 Backfire

I am a little confused here about this. I just put a stand alone system in my car to support a higher volume of NO2. The car did not run near as expected last night at the track. My best time is a 6.69 at 106MPH and last night I ran a 7.14 at 98. This is on a 200 pill VS a 150 on a better time. Question is, am I running to rich, I really didn't bother to look over at my wide band when I was at WOT but I know my AFR on NA is right where it should be 12.4-12.8. I was backfiring constantly all the way down the track as well. So does anyone know what that could be. To rich? The fuel that I am running in the stand alone is C16 and 109 unleaded for the regular system. Plugs are NGK T-9. Plugs are cool enough but just a little confused as to what this could be. Any help would be appreciated.
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Old Mar 22, 2009 | 05:55 PM
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What pressure are you running the standalone at? What size pills are you using? Did you read the plugs?
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Old Mar 22, 2009 | 06:36 PM
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Originally Posted by jmill96Z
What pressure are you running the standalone at? What size pills are you using? Did you read the plugs?
Its a low pressure pump. 8 pounds is what its set at. 200 shot is the pill size and yes I looked at cylinder 3 plug and there was oil at the base of the plug next to the clinoid and it was pretty free of oil the rest of the way up.
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Old Mar 22, 2009 | 07:57 PM
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8 lbs is alot of pressure on a low pressure system. Most run at 6.5 ish. What exact jets are you running. What fuel pressure does your jet card rate these pills at for a 200 shot?
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Old Mar 22, 2009 | 08:12 PM
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Originally Posted by jmill96Z
8 lbs is alot of pressure on a low pressure system. Most run at 6.5 ish. What exact jets are you running. What fuel pressure does your jet card rate these pills at for a 200 shot?
28 fuel and 51 nitrous. But it is a single stage with 2 injectors. I would assume that's 100 shot each side
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Old Mar 22, 2009 | 08:31 PM
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Might want to look at the size of the fuel jet. The calculator I use shows a 51 and a 44 fuel jet will give you 198 to the wheels at 8 psi. The jets you are using look to me like the intended jetting for 55 psi. That will definately cause issues
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Old Mar 22, 2009 | 09:02 PM
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Originally Posted by jmill96Z
Might want to look at the size of the fuel jet. The calculator I use shows a 51 and a 44 fuel jet will give you 198 to the wheels at 8 psi. The jets you are using look to me like the intended jetting for 55 psi. That will definately cause issues
I just double checked the jets and the fuel is 28 and nitrous is 51. But that would mean that I would be leaning the car out, doesn't sound accurate unless you think that running the car lean would cause backfireing, and I am talking about constant backfiring, like every tenth of a second. I didn't hear it but everyone watching said it was backfiring ridiculously.

As for the jets, are you saying that I am running a nitrous system that came with jets designed for a high pressure pump. Which means that I was throwing a **** ton of nitrous and not enough fuel to supply the demand, so it was probobly running lean, I should have looked over at my wide band gauge, but just not thinking about it when I am running the car. What do you think.
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Old Mar 22, 2009 | 09:05 PM
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Originally Posted by jmill96Z
Might want to look at the size of the fuel jet. The calculator I use shows a 51 and a 44 fuel jet will give you 198 to the wheels at 8 psi. The jets you are using look to me like the intended jetting for 55 psi. That will definately cause issues
What formula or spreadsheet are u using for the jet siz with the fuel pressure set up? Can you send it to me. Hantzum@cableone.net
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Old Mar 22, 2009 | 09:11 PM
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http://ny-trex.com/calculator.php

Here is the calculator. There are a bunch out there if you google it.

I think you were having lean backfires due to the jetting. Another option would be to swap the spring out in the regulator on the cell, and run it in high pressure at 55psi. This would let you keep your current jetting
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Old Mar 22, 2009 | 09:18 PM
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Originally Posted by jmill96Z
http://ny-trex.com/calculator.php

Here is the calculator. There are a bunch out there if you google it.

I think you were having lean backfires due to the jetting. Another option would be to swap the spring out in the regulator on the cell, and run it in high pressure at 55psi. This would let you keep your current jetting
Got it, appreciate the help. Glad I caught the the backfiring issues before it really did something bad. Do you think that I did any real damage from one lean pass? Man I wish I would have looked at my damn gauge, its mounted on my full pillar riht by my head.
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Old Mar 22, 2009 | 09:25 PM
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It all depends on what kind of timing you were running. It might not be a bad idea to run a compression test to make sure the guts are OK.

I have the same problem with the wideband. I never look at it. Now I just log it and check it out back at the trailer.
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Old Mar 22, 2009 | 10:33 PM
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Originally Posted by jmill96Z
It all depends on what kind of timing you were running. It might not be a bad idea to run a compression test to make sure the guts are OK.

I have the same problem with the wideband. I never look at it. Now I just log it and check it out back at the trailer.

Timing was set at 22 for the 200 shot. I dont think that having one bad pass on a lean shot would have have done to much damage. Do you really think that having a compression test is necessary?
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Old Mar 22, 2009 | 10:43 PM
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Honestly, 1 pass could hurt the motor. Is it likely, maybe not. Chances are that nothing got hurt, but it is a cheap reassurance to make sure everything's Ok. It just depends what you want. I would also back the timing off to about 18* and creep up on timing while checking the plugs after every nitrous pass until you get it dialed in. Keep us updated.
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Old Mar 22, 2009 | 10:46 PM
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Pull the plugs and if they are all there then put a new set in and go racing.

The tune up is way off, 22* is alot of timing for a 200 shot also.
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Old Mar 24, 2009 | 08:19 PM
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Originally Posted by ATVracr
Pull the plugs and if they are all there then put a new set in and go racing.
Wahoooooooo!!!!



Originally Posted by ATVracr
The tune up is way off, 22* is alot of timing for a 200 shot also.
No doubt. He doesn't even talk about tuning the car at all on gas. Scary stuff right. Oh and a 9 is too cold for what you are doing.
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Old Mar 24, 2009 | 09:45 PM
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Tested the compression in all 8 cylinders and they where all within 172 PSI -194 PSI. So no fatal damage done to the motor. The spark plugs all looked fine as well no melted cylinoids or anything. Thank God I was running 1/8 not 1/4.

And yes, 22* timing is just fine especially when your running 109 unleaded and C16 for the stand alone.

As for the T-9, I had this setup for a 350 pill 2 stage. I ran a 200 single stage just to test the stand alone system. Good thing I did that.
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