Misfire from 3-4k rpm Pro Charger D1-X gt350 throttle body culprit ?

[Mike K.]

I just finished a full build with the d1x and it has a gt350 intake and TB. Dynod around 900rwhp on a Mustang Dyno however I found that out in the road driving in 3rd 4th and 5th gear if get on it from around 3k to 4K it misfires sometimes bad enough to throw a blinking check engine.

Oddly once it passes this range all is good and it takes off like a bat outta hell. The Fuel pressure looks good and it seems to run better at even higher boost so I’m not sure what’s up just looking for some ideas.

My tuner / builder said the gt350 TB was giving him fits yet on the dyno it seemed ok.

Any ideas ? Has anybody else used this TB on a boosted build and had issues ?

Clip attached. I’m a bit worried about detonation etc so I did it for only a short time, this was rolling into WOT.

At light throttle no issues fwiw and it runs on e85 w Fore triple pump / 1300 injectors.

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[80FoxCoupe]

Any codes? Share a datalog? Use datazap and post a link.

 

[Cory S]

What's the plug gap at?

 

[Whitedevil95]

Subbing for knowledge

 

[Mike K.]

I was talking to my builder / tuner today he was telling me that the plugs used were so Cold and that they use this type of plug / gap on most of the boosted cars in FL and that was likely the reason for the misfiring when under 3500 in higher gears 3rd and Up due to the increased load / low tq at those rpms. I'm gonna go over to the shop today and do more testing and go for a ride with him.

Ill watch those RPMs closely today but it is around that 3.5 -4K mark that it clears up and just goes and I didn't notice it in 1st or 2nd fwiw but those gears I am reluctant to go WOT cause of wheel spin etc.

GAP wise Ill find out when I talk to him and Log wise let me see what happens after today.

Is there a particular gap that you guys run ? The intake still has functioning IRMC's also fwiw could it be that ? I do have an Nguage I don't use it but I think based on the reading I did that I can plug it in and get a log file.

 

[Cory S]

GAP wise Ill find out when I talk to him and Log wise let me see what happens after today.

Is there a particular gap that you guys run ?

.023-.025" NGK 6510's.

 

[Mike K.]

Thanks and I assume you guys don’t have this issue at lower rpm’s ?

 

[Whitedevil95]

Im on 13psi NGK 6510s gapped at .027 and no stuttering or misfire issues here.

 

[Mike K.]

Just an update, no codes showed up but also when put on the dyno which is a Mustang dyno in this case there was no stumble or hesitation at all but it doesn't put load on the rollers until 3500rpm. Did a bunch of testing and 3500 rpm is right at the speed where the stumble goes away on the street. If I downshift or shift into the higher gears at above or near this rpm range there is also no issues.

1st and 2nd gears also don't exhibit this problem. The plugs in my case are TR7IX gapped at about .032 but I need to pull one to double check it.


I suppose it could be these plugs perhaps and the lower rpm pulling I am starting from ? I could try the 6's but down the line the goal was to pulley down a bit right to get a bit more power out of it so maybe these plugs are the way to go.

The car in all other aspects is unbelievably fast with no issues. it's just at these cruising speeds where this drivability issue and as I watch these videos I took i see that it really is about 3.5k rpm that all clears up. Maybe I just need to drive it more aggressively given what it is ?

 

[HKusp]

You want good drivability, I would think, unless it's a track only/mostly car. I would try and close that gap on those plugs a bit and see if that helps. If it does help but the issue is still there, then try going with the 6510's. Those are what I ran on my GT500, gapped at .028, but the TR7IX is a good plug too.

 

[Mike K.]

You want good drivability, I would think, unless it's a track only/mostly car. I would try and close that gap on those plugs a bit and see if that helps. If it does help but the issue is still there, then try going with the 6510's. Those are what I ran on my GT500, gapped at .028, but the TR7IX is a good plug too.

I hear ya I’m debating it, 6510s are 1 step warmer than these 7IXs but still 1 step colder than stock right ? Seems most people here use the 6510s

 

[Cory S]

6510's are the G.O.A.T...... Until like 1200whp and 7's........

 

[Proshop]

6510's are the G.O.A.T...... Until like 1200whp and 7's........

Agreed!
OP swap to the 6510’s with a proper gap and remedy the situation. You can always save the other plugs for a later time.

 

[80FoxCoupe]

6510's are the G.O.A.T...... Until like 1200whp and 7's........

I like Brisk rr12s for boosted app under 1khp, rr10s over 1khp. 6510 is only one range colder than stock and I Def wouldn't run that over 1khp. But I know everyone will say everyone does it LOL.

 

[Cory S]

I like Brisk rr12s for boosted app under 1khp, rr10s over 1khp. 6510 is only one range colder than stock and I Def wouldn't run that over 1khp. But I know everyone will say everyone does it LOL.

Right? Find someone that blamed an engine failure because their plug was one step too hot........

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