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Discussion Starter #1
Car is a 416 LS, Holley EFI, 2 stage 4150 Wilson proflow plate, flowed by Steve at IS, pump gas with a dedicated low pressure fuel system for the nitrous (VP N02 fuel). I made three passes yesterday trying to improve the tune. Please take a look and let me know your thoughts. Base tune up in it is 46 N and 35 F. 900 psi bottle pressure and 6 lbs fuel pressure. All passes were done at the same bottle and fuel pressure. All of the plugs pictured were driven up to the line, burnout, then shut the motor down turning off the track and pulled out on the return road.

1st pass: Pulled 6 degrees to start

The plug looked rich and the log showed about a 12.0 afr. Pictures below





2nd pass: Pulled 8 degrees because I was told to play it safe to start and can always add the timing back in. It ran rich last pass, so I lowered the fuel jet from a 35 to a 34. Pictures below

The plug looked a little better, but not much, and the log shows the same 12.0 afr





3rd pass: Pulled 8 degrees. The plug still looked rich on the second pass so I dropped it another fuel jet from a 34 to a 33.

After dropping the fuel jet twice from the first pass, the log shows the afr got worse, but the plug looks better. Needless to say im confused. More detailed pictures below of the spark plug.















The erratic RPM in 1st gear is just traction issues. Thats another problem I have to figure out after this :-damnit. Any advice is greatly appreciated. Thanks in advance
 

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So you are shutting down the engine once you turn on to the return road? Are you letting the engine decel or are you putting it in neutral and coasting with it idling? What heat range plug? Looks like a -7 in the one pic.
 

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Discussion Starter #5
I started off pulling 6 degrees as recommended by Steve at IS. I pulled an extra 2 degrees because the ground strap looked too hot. A more experienced racer said to pull extra to be safe when figuring out the tune. I didn't keep pulling more after that. I had the same timing on the 2nd and 3rd pass.

I know I shouldn't rely on the wideband for tuning which is why I'm doing my best to learn how to read the plugs. I just don't understand why the wideband is showing opposite what the plugs say. Makes it very confusing

Heat range is -7. I am putting it in neutral and letting it idle while I slowdown, only hitting the gas to keep the engine alive. As soon as I am safely off the track, I shut it down.
 

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"Darkness"
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Removing 1 jet number of fuel won't show much on a plate system like that. I would start with a .030 fuel pill and leave the timing where you ended up for now.
 

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Discussion Starter #7
Okay I will try that. As far as the timing goes, I'm looking for the blue line to be on the curve of the ground strap, right? Like it is on the plug from the 3rd pass
 

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Discussion Starter #9
All three runs had very different 60 foot times so the ET and MPH are inconsistent.

1st pass: 153 mph (dead hook, bogged)
2nd pass: 156 mph (a lot of tire spin)
3rd pass: 150 mph (spun, peddled it)
 

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Okay I will try that. As far as the timing goes, I'm looking for the blue line to be on the curve of the ground strap, right? Like it is on the plug from the 3rd pass
I wouldn't say your "looking for a certain look" with a new combo......, tuning for a "LOOK" usually ends up in trouble.
What about 330' & 660' times?
 

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First question I have is what are you running a wet system?
Second 12:1 would be pig rich on my holley with that small of a hit. Try bringing the target a/f 12.8-13.0
 

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Discussion Starter #12
Yes it is a wet system.

Keep in mind it is a 2 stage plate so there are two 46 nitrous jets. I know that still isn't considered a big shot around here, but I just wanted to clarify.

I have been running the car with closed loop turned off. I was told not to set a target afr and not let the Ecu make changes during nitrous passes.
 

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Who told you not to run closed loop?
I run way more nitrous with my closed loop on. its limits are set to 10%.
I was wondering why you air fuel was all over the place.
Turn it back on and run the system dry.
 

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EFI/N2O JUNKIE
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Who told you not to run closed loop?
I run way more nitrous with my closed loop on. its limits are set to 10%.
I was wondering why you air fuel was all over the place.
Turn it back on and run the system dry.
He can't run it dry because he is running pump gas in the tank and race fuel for the nitrous enrichment. That is what makes tuning this type of combo tough.

I would look at the 1/8 and 1/4 mph as a tuning tool. The plug doesn't look like it has too much fuel on the porcelain. I know some like it snow-white, but that isn't always the best.

Looking at the cut-open plug, I would start putting timing back in and watch the time slip. So far all I see is that you got the strap hot enough to start cooking the cadium, but have not got it hot enough to start removing that.

There should be pictures around here that will better show the "timing line". This occurs after the cadium coating burns-off. I found my combo liked the "timing line" 1/2 way to the bend (NGK plugs). Ran it at the bend twice, no real gain in MPH, so took the timing back out. I think it was a 2* change to move that mark a lot.
 

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Run it in closed loop 12.7-13.0. Before pulling jets, I would start dropping fuel psi by 1/4 lb. Do you have "Pause Enabled"?

I am between 5 1/2- 5 3/4 psi.
 

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Discussion Starter #16
Mike, thanks for taking a look. Unfortunately I can't really tune based on 1/8 and 1/4 mph because of how inconsistent the car is leaving. isn't the timing line you're referring to already on the bend on the 3rd pass plug? Do you run your car in closed loop on nitrous too?

I tried dropping the fuel pressure 1/4 lbs each pass last time I was at the track before this (2 months ago), but there was no effect. That is what made me just keep it at 6 lbs and start dropping the fuel jet instead, hoping to see a bigger change. I do not have "pause enabled" because I am not progressing it or pulling different amounts of timing.
 

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Mike, thanks for taking a look. Unfortunately I can't really tune based on 1/8 and 1/4 mph because of how inconsistent the car is leaving. isn't the timing line you're referring to already on the bend on the 3rd pass plug? Do you run your car in closed loop on nitrous too?

I tried dropping the fuel pressure 1/4 lbs each pass last time I was at the track before this (2 months ago), but there was no effect. That is what made me just keep it at 6 lbs and start dropping the fuel jet instead, hoping to see a bigger change. I do not have "pause enabled" because I am not progressing it or pulling different amounts of timing.
Then I would look at the motor tune, depending how your inj are scaled, it may be dumping fuel when volts drop.

First above all, IMO, Closed Loop enabled.
 

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If you run close loop to 12.8, when the efi pulls fuel at least it will be pulling pump gas not race fuel, which is better then leaning out the race fuel.
 

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On a side note; is it possible to have timing retard delayed when it "turns off"
Much like an msd.
In case one peddles it or lifts momentarily.

I run a plate as well, dry however, and it sure seemed like 12.0 was pretty rich with my holley efi. I run it in closed with the kit on as well.
 

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On a side note; is it possible to have timing retard delayed when it "turns off"
Much like an msd.
In case one peddles it or lifts momentarily.

I run a plate as well, dry however, and it sure seemed like 12.0 was pretty rich with my holley efi. I run it in closed with the kit on as well.

I believe it's built in the holley not adjustable
 
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