Car breaking up/stumbling around 6k

[hatchke]

Went out and was testing some 60-130's in Mexico and the damn thing was breaking up really hard in 3rd/4th around the 6k mark. I adjusted the plug gap on my TR6's to .025 and it ran/pulled MUCH better after I found 3 of the plugs were gapped pretty loose.

My dyno charts show a little bit of the hesitation and Blankenship suggested it was probably just the plugs.

Ran .5s faster after but still breaking up pretty hard around the same mark. Do I just keep tightening the gap down further than .025 or am I missing something here? From what I read, the TR6 seem to be fine around this gap for most on E85.

For reference, I made 690whp at 20psi on my Whipple 2.9 with E85. I'm running a decent bit of boost but this setup isn't anything crazy. I didn't see many people running much tighter than .025 but I guess i'll roll down to .023 next and see how it goes?

 

[MG0h3]

Think I’m at 26 or 28 on 20psi.

Confirm your AFR is good!


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[hatchke]

Think I’m at 26 or 28 on 20psi.

Confirm your AFR is good!


Sent from my iPhone using svtperformance.com

That's a good call. I'll see if I can log one of these runs and see what we're looking like.

 

[01yellercobra]

Check A/F, fuel pressure or FPDC if you're still returnless, and voltage.

 

[03cobra#2]

I would just throw a new set of plugs at it. Make sure you gap them using a feeler gauge. I personally run TR7ix and they are great for me. Let us know what you find.

 

[DSG2003Mach1]

My car would hit a wall at 5k, gap was still and plugs didn’t look awful but a fresh set cleared it up.

As mentioned I’d throw all fresh plugs in there and make a hit logging the stuff above. If that checks out and still doing it maybe coils are on the way out

 

[03' White Snake]

How’s your voltage? Alternator cutting out at high rpm?

 

[robvas]

Coils good? Have another set you can swap in?

 

[cobracide]

Good advise here, change plugs and datalog some pids.

 

[hatchke]

Thanks for all the advice here, this is all some really good information and things to check. I ordered a new set of Ford coil packs and some fresh TR6 to throw in.

On the alternator voltage, would it present only at higher loads in 3rd/4th gear at high RPM, or would it present in lower gears at high RPM and open-throttle too? I may or may not have just done a series of WOT donuts in 1st and 2nd to see what the voltage was doing. It's holding strong at around 14, maybe a touch under. It's just over 14 at idle, like 14.2/3 on the gauge

 

[LS WUT]

I’d say the coils and plugs would be my first go to. They’re really small thing in the grand a scheme of things but even if they’re fouled just a little bit and off by .01 in gap they can change the actions of the car. Secondly what I’d do is make she’s the cars up to operating temperature, and check the alternator under load in neutral at around 2,500 RPM’s.

 

[hatchke]

Interestingly, I did some more testing tonight to make sure the alternator/voltage was holding strong and the car pulled through 3rd and 4th pretty smoothly. Tiny hiccup in 3rd but 4th felt good.

I felt compelled to try again and 3rd - 4th both felt perfect after that. I feel like the intermittent nature of the problem is pointing to a coil that's going bad. Otherwise, I don't see how it could break up badly one run, be fine the next, and then be good for 1 gear, mediocre after the next shift.

 

[LS WUT]

Interestingly, I did some more testing tonight to make sure the alternator/voltage was holding strong and the car pulled through 3rd and 4th pretty smoothly. Tiny hiccup in 3rd but 4th felt good.

I felt compelled to try again and 3rd - 4th both felt perfect after that. I feel like the intermittent nature of the problem is pointing to a coil that's going bad. Otherwise, I don't see how it could break up badly one run, be fine the next, and then be good for 1 gear, mediocre after the next shift.

Couls are nasty little ****ers man. They’re so hot and cold lol. One little wire in there that’s burnt or pinched sends you to hiccup city.