# Misfiring at 20 PSI, high RPM. Spark Plug suggestions?



## Longitudinal (Nov 13, 2004)

I have plenty fuel up top, but am getting a misfire starting around 6KRPM. Plugs are B6ET. I am installing a set of B6ES plugs and am closing the gap a little, starting around .025. What about going to a B5ES?


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## rivethead (Nov 27, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

I assume you have decent plug wires? Under high boost levels you could blow the spark. 2 things to try are a smaller gap (which you are doing) - Colder plug (same thing)- then If you keep having problems you might want to try a better plug wire - or aftermarket ignition if you are not running one allready.


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## dcvento (Aug 1, 2001)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

try gapping them to 28 or so. im running nippon denso 3008's gapped to 28


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (rivethead)*


_Quote, originally posted by *rivethead* »_I assume you have decent plug wires? 

New Bosch. I have not yet been convinced I need any more than that.

_Quote »_ Under high boost levels you could blow the spark.

Extinguishing the spark is exactly my concern.

_Quote »_Colder plug (same thing)

Actually the NGK numbers run backward. The 5 is a hotter plug. I should be considering a COLDER plug to try to keep spark alive?

_Quote »_ or aftermarket ignition if you are not running one 

That might be necessary. Right now, it's Bosch KS with a turbo 5K coil. The turbo coil is known to work very well for 18+ PSI, and I am firing it earlier in the cycle than most, which should make the job of sparking easier (sparking under lower cylinder pressure than if timing is retarded a lot.)
.028", eh? By what interval should I adjust gap? I was thinking .005 closer (like .025",) but it seems like maybe I should take very small steps until the misfire goes away?
This FI tuning is mostly new to me. Previously, on NA engines, it was mostly set it and forget it.


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## Jefnes3 (Aug 17, 2001)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

NGK BKR 7E
(copper plug 2 steps colder than ~stock N/A plug)
Gapped to .022"

-Jeffrey Atwood


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Jefnes3)*


_Quote, originally posted by *Jefnes3* »_NGK BKR 7E
(copper plug 2 steps colder than ~stock N/A plug)
Gapped to .022"

-Jeffrey Atwood

Thanks. I don't recognize that part number. Is it still a large (21mm hex) spark plug?


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## Jesusloves20v (Sep 9, 2005)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

No, that plug is for x-flow, 16v's, vr6's, 20v's

Youll need a 7 range plug in a NGK and do what Jeff said, gap that sucker down to .022


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## vdubspeed (Jul 19, 2002)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Jesusloves20v)*

I run ngk bkr7e plugs gapped to .024 at 15psi. No probs here.
ignition is handling buy some stock GM coils(SDS provided) and some 8.8 Accell wires.


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## BoostedOne (Mar 30, 2003)

Wow, same problem I had a few months ago.
ABA head on a 1.8, above 20psi and 6K it just shuts down pretty much. Lower the boost it will go to 7K, lower the RPM it will go past 20psi.
I dont know if I fixed it, but my first shot at it was getting an better ignition box. Plug wires alone wont do much for you, unless you are arcing out the side of them, or you have junky ones.
I bought a MSD 7AL-2 off a Mustang board, and converted over to a Ford ignition coil.
Once Iget the car back together(I changed ALOT of stuff on it at the same time), I will see if it helped. I know Im going to be getting hold of Magnecore for some wires too.


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Jesusloves20v)*


_Quote, originally posted by *Jesusloves20v* »_No, that plug is for x-flow, 16v's, vr6's, 20v's

Youll need a 7 range plug in a NGK and do what Jeff said, gap that sucker down to .022

Figgers. So, I want maybe a BP7ES? I put in a set of BP6ES today, gapped to .022", and had every bit the misfiring problems as before, and probably a bit more severe and more frequent (every pull to/above 6KRPM instead of every now and again.)
Is a cooler plug gapped the same actually going to help? I will admit almost total ignorance when it comes to spark bolts.


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## Butcher (Jan 31, 2001)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

If the reasoning is that there is so much pressure that the spark cannot jump the gap whay would a colder plug be a way to go? I would think something that would jump the gap easier would be the way to go [ie smaller gap, stronger coil, etc.].
I had a smiliar problem many moons ago and the engine would not go past 5 psi boost. After several attempts of adjusting the wastegate I figured out it was the coil. I would think that since the coil you are using was never designed to see 20 psi and that that is one heck of a lot of pressure for the spark to jump thru I would check that. Another think might be that since spark will go to the least resistance I would think that maybe the wires/resister ends are where the spark is finding ground. Those shielded plug ends are difficult to find those shorts that only occur under load.


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## purple-pill (Feb 2, 2003)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Butcher)*

do your plug wires have beru ends on them? I had this problem way back they are plastic right above the metal and break run and idle fine and then when you start driving or racing the move and break up...that is when i switched to magnacore....try replacing them with other wires once...


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## purple-pill (Feb 2, 2003)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (purple-pill)*

you cant tell by looking at them...you can wiggle them and see sometimes


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## German VR6 (Dec 21, 2002)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (purple-pill)*

how do you know if your blowing out spark??


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## rivethead (Nov 27, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (German VR6)*

Why a cooler plug? From BDS (Blower Drive Service) info page. Forced induction is forced induction. 
Spark plugs should be one or two heat ranges colder than the recommended stock factory plug (never use extended tip spark plugs). The colder plugs need to be used due to the higher cylinder pressure created by supercharging; higher cylinder pressure means more heat. 
A cooler plug helps to keep pre-ignition levels down under high heat conditions (high boost). Since some plugs will actually glow after high boost, high use running. Plus running a cooler plug under high boost conditions helps to eliminate erosion of the tip over time.

High densities (like those under boost) require more voltage to spark.
Thus sometimes the smaller gap needed. This can be a detriment to optimum performance - You should run the widest gap possible. So the need for a more advanced ignition system at high boost levels.


_Modified by rivethead at 9:25 AM 9-12-2005_


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## Butcher (Jan 31, 2001)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (rivethead)*


_Quote, originally posted by *rivethead* »_Why a cooler plug? From BDS (Blower Drive Service) info page. Forced induction is forced induction. 
Spark plugs should be one or two heat ranges colder than the recommended stock factory plug (never use extended tip spark plugs). The colder plugs need to be used due to the higher cylinder pressure created by supercharging; higher cylinder pressure means more heat. 
A cooler plug helps to keep pre-ignition levels down under high heat conditions (high boost). Since some plugs will actually glow after high boost, high use running. Plus running a cooler plug under high boost conditions helps to eliminate erosion of the tip over time.

High densities (like those under boost) require more voltage to spark.
Thus sometimes the smaller gap needed. This can be a detriment to optimum performance - You should run the widest gap possible. So the need for a more advanced ignition system at high boost levels.
_Modified by rivethead at 9:25 AM 9-12-2005_

Thanks for the ignition lesson







but the question was how does a colder plug help a misfire under high boost. I know about heat ranges in plugs but I do not understand how that helps with misfires under high boost and maybe someone can enlighten my premadonna ego.


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (German VR6)*


_Quote, originally posted by *German VR6* »_how do you know if your blowing out spark??

Well, the dyno shows mixture running much richer from the moment the misfire starts, indicating both 1) ample fuel is present, and 2) that such a rich AFR following a not-so-rich one tells me that maybe combustion is stopping. Also, when driving the car and encountering the misfire, I can actually smell raw fuel on deceleration. 
Cooler plugs (NGK BP7ES) gapped first to .028, then to .025 have changed NOTHING. Peter recommends the W6DPO, but $12.50 each is a big plunge.
This problem is irritating because the car would love to rev to 6K or slightly more, but I can't rev past 5500 without encountering the misfire. Sometimes, if I get everything nice and hot, I can occasionally rev to 6K, but never any higher.
Oh, another indication to me that I am extinguishing spark comes when I change gears after the misfire occurs. I rev it out and it misfires. I change up one gear, then lean back into it. The engine stutters in the exact same way it did with the misfire for a second or two, then clears its throat and gets going. This, I believe, is the gasoline-soaked spark plugs drying off before they can spark effectively again. Does this make sense?


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## _Scirocco20v (Sep 10, 2005)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

What a/f's are you running when the misfire happens?
If you were blowing out the spark (too rich), the wideband would read it running lean as there is a lot of oxygen in the exhaust stream now since it wasnt used in the combustion process.


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## Mad Mel (May 14, 2002)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (_Scirocco20v)*

I used Bosch W4CS (cheap plug) with good results in my G60. W6DPO is the standard G60 plug.


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## rivethead (Nov 27, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Mad Mel)*


_Quote »_Thanks for the ignition lesson but the question was how does a colder plug help a misfire under high boost. I know about heat ranges in plugs but I do not understand how that helps with misfires under high boost and maybe someone can enlighten my premadonna ego.

I have been busy wiring up my tec3 trying to get the caddy ready for a run this weekend. I am not the expert by any means. But here goes. From what I can remember with plugs on old blower motors - The colder plug helps with pre-ignition which can sometimes be diagnosed as a missfire. A colder plug from what i was told has a shorter insulator which has a bit to do with helping the spark in a boost application. We used to run a surface gap plug with no heat range on very high horsepower motors. If you were not to careful you could foul up the plug quickly. The best solution outside of ultra high HP motors is probably a projected tip plug - Though you have to check piston clearance or (and I have not used them) the bosch pt+4. The other reason for a colder plug is that over time you can wear the tips on plugs - If you are changing plugs regularly this is not an issue. One way to see if you are running the right heat range of plugs is to look at the condition of the plug - You want a light reddish-brown tint. 
Champion plugs used to have a formula for heat ranges - 1 range colder for every point of compression increase. Don't remember the forced induction other than 2 ranges colder to start with.


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (_Scirocco20v)*


_Quote, originally posted by *_Scirocco20v* »_What a/f's are you running when the misfire happens?

It's showing about 12:1 and slowly but steadily moving richer. Lookie.








Misfire starts somewhere between 5500 and 6000 RPM. This is at 20 PSI. At 14-15 PSI, misfire didn't occur until 6500.


_Modified by Longitudinal at 7:50 AM 9-20-2005_


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Mad Mel)*


_Quote, originally posted by *Mad Mel* »_I used Bosch W4CS (cheap plug) with good results in my G60. W6DPO is the standard G60 plug.

W6DPOs are mad expensive. At what pressure did you run the W4CS? If they're cheap, I guess there's no harm in trying yet another plug. BP7ES gapped at .025 aren't doing it. I can gap them down to .022 as recommended, but am skeptical. 
I also have some STI wires I could swap on and see if they help. I am running Bosch wires right now.


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## Mad Mel (May 14, 2002)

1.4 bar/ 233whp.


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## Longitudinal (Nov 13, 2004)

*Re: (Mad Mel)*


_Quote, originally posted by *Mad Mel* »_1.4 bar/ 233whp.

1.4 bar is relative, I assume. That's right around 20 PSI, which is where I am.
You were doing this with factory ignition, yes?


_Modified by Longitudinal at 9:07 AM 9-20-2005_


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## Mad Mel (May 14, 2002)

Stock ignition yes.


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## _Scirocco20v (Sep 10, 2005)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*








14:1 a/f's at 18psi









You're waiting for a meltdown. 
If the misfire happens at the top end and if the a/f contiunes on its downward pattern, you're probably running too rich. 

The over all a/f chart shows that you need a better fueling solution.


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## Evolution Marine (Sep 18, 2003)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (_Scirocco20v)*

Heat Range Relates to Detonation and spark-plug gap relates to the level of resistance at the Gap in relation to Peak Cylinder Pressure (the higher the peak cylinder pressure the higher the resistance at the spark-plug gap). The fuel curve is lean in the Mid Range, at 3,500 RPMs the A/F Ratio should be at 13:1.







- Bob


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Evolution Marine)*


_Quote, originally posted by *Evolution Marine* »_The fuel curve is lean in the Mid Range, at 3,500 RPMs the A/F Ratio should be at 13:1.







- Bob

Yeah, thanks for pointing that out.







Here's for people who don't read the whole thread to see what has already been established. http://****************.com/smile/emthup.gif 
I need to read a book that covers spark plugs. All this conflicting information is driving me ga-ga.


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## rivethead (Nov 27, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Longitudinal)*

Try these links for plug information
http://www.carcraft.com/techarticles/64378/
http://www.boschusa.com/AutoParts/FAQs/SparkPlugs/
http://www.ngksparkplugs.com/t...ry=US


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## Longitudinal (Nov 13, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (rivethead)*


_Quote, originally posted by *rivethead* »_Try these links for plug information

Thanks for posting up the information. 
The cooler air has reminded me of one possibly important fact: this problem is notably worse when the engine is cooler. If I whip hard on it and get the temp up, it might occasionally get as far as 6K RPM before the misfire occurs. Does that help anybody diagnoe this?


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## BoostFactory (May 27, 2005)

Didn't know if it was covered on top or not since i didnt read most of it, but i've seen similar problems that were due to ignition. 
Are you running a strong ignition at all?
Paul


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## Longitudinal (Nov 13, 2004)

*Re: (BoostFactory)*


_Quote, originally posted by *BoostFactory* »_Didn't know if it was covered on top or not since i didnt read most of it, but i've seen similar problems that were due to ignition. 
Are you running a strong ignition at all?
Paul

KE-Jetronic harness with Audi 5KT coil. Current plugs are BP7ES gapped to .024". This coil has made it to 18 PSI dependably on I5s and at higher RPM than I have been able to manage. I wonder if ignition control is the issue.


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## NCabbyT (Jul 8, 2001)

Recently I've had some BIG misfire problems. Friday night, I got onto the throttle, and then buh...... BANG.
A big stall (mis) and then an afterfire out the exhaust. My buddy Alexi (from HPA) heard it, said it was pretty loud from right beside the car.
It's been ongoing now, missing under hard load, hi boost (20 PSI).
It all started happening when I gapped my plugs to .025. They must have been about .022 or .023 before because I couldn't even fit a guage into them and the shortest gap it had on it was .025.
I'm gonna go pick up some NGK BKR 7E's tomorrow from Lordco. I'll toss those in and see how she runs.


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## [email protected] (Mar 16, 2004)

*Re: Misfiring at 20 PSI, high RPM. Spark Plug suggestions? (Butcher)*


_Quote, originally posted by *Butcher* »_Thanks for the ignition lesson







but the question was how does a colder plug help a misfire under high boost. I know about heat ranges in plugs but I do not understand how that helps with misfires under high boost and maybe someone can enlighten my premadonna ego.

Are you serious...


rivethead}
A cooler plug helps to keep pre-ignition levels down under high heat conditions (high boost). Since some plugs will actually glow after high boost said:


> Colder spark plug because the pressure under BOOST is making it too hot.


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## NCabbyT (Jul 8, 2001)

Ok, I'm running the BKR 7E's now. Seems to have solved my problem, but it's pissing rain here and I haven't gone for a good rip yet.
I'm gonna dyno the car on friday though and take it for a rip to Whistler for the VWDOV Fall cruise.


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## Longitudinal (Nov 13, 2004)

*Re: (NCabbyT)*

I'm glad the 7s solved your problem. They didn't for me. .025" gap.


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## NCabbyT (Jul 8, 2001)

I've got bigger problems. Like exhaust reversion.


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## Longitudinal (Nov 13, 2004)

*Re: (NCabbyT)*


_Quote, originally posted by *NCabbyT* »_I've got bigger problems. Like exhaust reversion.

I built a 3" that has taken care of that. For my problem, I have considered a drive to MI to pick Peter's brain. Haven't axed him about it, though.


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