Help, popping in 3rd gear spraying.

[WS6HUMMER]

@ the track this weekend.
I made 1 all motor pass just fine, but when I sprayed it for the first time with my new jets
(went from 125 to 150 shot) something weird happened. The AFR on the log was 19.XX
but I was told by someone that N2O can sometimes skew your AFR readings due to the way
it combusts. Anyway I made only 2 nitrous attempts due to time and people messing up the
track surface, both times it felt like I hit the revlimiter or what I thought a nitrous backfire
might feel like so after the first time it happened I moved the RPM limit from 6800 to 7200. It
happened again on the second pass, this time it did it just as I shifted into 4th after the 1/8th.
Both times when it happened I got out of the throttle,put the car in neutral and tried to rev
the motor but the pedal acted like it was dead so after coasting for another 2 seconds again
I hit the gas and I had throttle again. I am so confused I dont know what happened, I
rechecked my nitrous jets and everything was right. I know this is highly unlikely but could a
TPS malfunction cause this? The first time it happened I noticed on the log I got 4* of knock
and my timing tuner/window switch will shut down the nitrous if it gets a bad or noisy crank
signal, I guess it did. Here's a copy of both logs and my current tune. The timing tuner pulls
4* of timing on WOT when the nitrous is armed. I never had anthing like this happen when I
sprayed the 125 shot and pulled 3*. I appreciate any advice you can
give.

Hummer

[5_Liter_Eater]

Wet or dry?

[WS6HUMMER]

Wet or dry?

Wet, checked the noids as usual the day before I went to the track. All my friends seemed to think it was going lean, I dont see how. I have a Racetronix 255lph pump and am running one fuel jet size bigger than what is nescesarry.

[Dragman]

what was AFR on motor run??
Did u leave everything same on tune when u shoot NOS, since u have timing piece to pull timing? I wouldnt want 19.xx AFR at least mine is not. Mine around 11.8- 12.0 on 125 shot.

[WS6HUMMER]

what was AFR on motor run??
Did u leave everything same on tune when u shoot NOS, since u have timing piece to pull timing? I wouldnt want 19.xx AFR at least mine is not. Mine around 11.8- 12.0 on 125 shot.

I VE and MAF tuned the car and have the commanded AFR of 12.8, It usually runs pretty close to that on motor however on the all motor pass that night I forgot to push the record button on the MVPI. On the 125 shot my car would run high 11.xx to low 12.xx on the AFR but that night both times when I sprayed the AFR was in the 19's according to the LM1 through
all the gears that I could make it untill the popping occoured. A friend that sprays al lot of nitrous (3 stage) told me that you cant trust the LM1 on nitrous because nitrous is an oxidizer and it can make the oxygen content read wrong if not all burnt up in the combustion process. This is the first time this has ever happened though, every other time I have sprayed it always gave the proper reading on the LM1.

[Dragman]

I VE and MAF tuned the car and have the commanded AFR of 12.8, It usually runs pretty close to that on motor however on the all motor pass that night I forgot to push the record button on the MVPI. On the 125 shot my car would run high 11.xx to low 12.xx on the AFR but that night both times when I sprayed the AFR was in the 19's according to the LM1 through
all the gears that I could make it untill the popping occoured. A friend that sprays al lot of nitrous (3 stage) told me that you cant trust the LM1 on nitrous because nitrous is an oxidizer and it can make the oxygen content read wrong if not all burnt up in the combustion process. This is the first time this has ever happened though, every other time I have sprayed it always gave the proper reading on the LM1.

sounds lean to me. my LM1 works fine on my C5 when I spray it. I can not open up ur scan right now. I run speed density on my car and like it alot better than with MAF. Someone can chime in and look at ur scans. Good Luck!

[WS6HUMMER]

sounds lean to me. my LM1 works fine on my C5 when I spray it. I can not open up ur scan right now. I run speed density on my car and like it alot better than with MAF. Someone can chime in and look at ur scans. Good Luck!

Thanks.

[EC_Tune]

Definitely lean... Frame 330 shows it.

[WS6HUMMER]

Definitely lean... Frame 330 shows it.

Thank you so much for looking at this for me, I guess the fuel solenoid was failing. Cold fusion would not sell me a plunger so I ordered 2 brand new noids from dynotune that can be rebuilt. I cant think of any other reason it would go lean, I have good fuel pressure.

Do you think the AFR was really in the 19's? Is there anything else I
need to check that would make it lean out? I want to play it safe.
What log was it run 1 or 2 that it went lean on frame 330?

Thanks again!

Hummer

[EC_Tune]

IIRC Run 2. You were at WOT (TPS = 100%) and AFR > 18
If the fuel solenoid wasn't opening, then you were definitely that lean.
I think I would give the motor a onceover to make sure nothing got hurt (plugs are a good indicator).

[WS6HUMMER]

IIRC Run 2. You were at WOT (TPS = 100%) and AFR > 18
If the fuel solenoid wasn't opening, then you were definitely that lean.
I think I would give the motor a onceover to make sure nothing got hurt (plugs are a good indicator).

Changed the plugs already, they all looked like the one below. No melted ground straps or electrodes, the porcelan was however very clean for my car.
I'm told the burn mark on the ground strap being closer to the thread ring means lean.
Tell me what you think.

Thanks!

[EC_Tune]

What's the gap on that thing .010"? Looks pretty narrow...

Did any of them have cracked porcelain? IF not you got away with it this time...

[WS6HUMMER]

What's the gap on that thing .010"? Looks pretty narrow...

Did any of them have cracked porcelain? IF not you got away with it this time...

Nah the gap is .036, want to play it safe.
I inspected all of them pretty close and didnt see any cracks. I did some research on plug readig and learned if they got too hot the porcelan would be shiny, if they are chalky looking they are ok. They all look chalky to me, I'm glad it looks like everything might be ok

Is there anything else I can do to make sure this never happens again?
I am replacing the noids, they just came in today.

Thanks!

[EC_Tune]

Run w/o N2O? LOL Just kidding...

Solenoids can be/are an issue with N2O.
However there should be a way of checking the fuel solenoids without spraying N2O. Do it very briefly or you will choke the engine. As long as you have fuel you shouldn't go lean like that.

[WS6HUMMER]

Run w/o N2O? LOL Just kidding...

Solenoids can be/are an issue with N2O.
However there should be a way of checking the fuel solenoids without spraying N2O. Do it very briefly or you will choke the engine. As long as you have fuel you shouldn't go lean like that.

Thanks, I'm not taking any chances.

[Dragman]

What's the gap on that thing .010"? Looks pretty narrow...

Did any of them have cracked porcelain? IF not you got away with it this time...

look's like gap is alittle tight at that camera angle. But I would buy a tool to square up the strap as it is angled bad. not causing any your issues but I like mine to be straighter.

[rob82]

Sounds too rich to me - but I cant see the logs as I havn't got the software in front of me. From what you said in the original post its popping when the NOS is on. So I'm guessing this pop is a missfire which is why it shows up as a lean condition on the o2 sensor. As for the reason - it may be a rich missfire - overly retarded ignition or your have an ignition problem.

The reason it felt like you had no throttle was probably from a gross over fuelling for a sec or two. I would drop the fuel jet size down 1 from the recommended as they are usually massively on the safe side anyways.

[gold98Z28]

Nah the gap is .036, want to play it safe.
I inspected all of them pretty close and didnt see any cracks. I did some research on plug readig and learned if they got too hot the porcelan would be shiny, if they are chalky looking they are ok. They all look chalky to me, I'm glad it looks like everything might be ok

Is there anything else I can do to make sure this never happens again?
I am replacing the noids, they just came in today.

Thanks!

"I am replacing the noids" can i get your old ones.