When is the misfiring occurring? Low engine speed or higher speeds? Cold engine or warm? You should be using the BRK6EK. Bosch and NGK heat rating system is different.

 

It misfires at low rpm....it clears up and doesn't miss under WOT....

It seems the car only runs good on multi ground electrode spark plugs??

 

Not at all. I have run the NGK BRK6EK for the past 50,000. Gonna change them soon with the same ones. What gap did you use? A 7 heat range may be just too cold for the engine, too and your plugs are fouling. Multiground electrodes have no more spark than a single electrode plug.

 

Interesting....ALLDATA says to ONLY use bosch multi ground electrode plugs...which is what's throwing me off here.

Isn't a heat range of 6 factory on these cars? So why would a 7(NGK) be too cold if its just 1 step colder?? Isn't a colder plug needed with a forced induction add on such as a supercharger for these cars??

I used BKR8E(2 steps colder) with a .024 gap...my guess is I obviously went too cold. But before trying the BRK8E, I had in the NGK BRK7EIX(1 step colder) iridiums, it ran like crap as well..... So the only plug I've had success on so far is the 6 heat range on the bosch multi-ground plug. I guess I need to run a heat range of 6 and try the BRK6EK's?

I'd really like to see if I could get away with a plug that is 1 step colder than the factory heat range, especially with this supercharger on this car. I believe it would run a lot more efficient. Please correct me if I'm wrong.

 

Increase your 0.024 gap to 0.028. Heat range numbers for different manufactuirers ARE NOT the same. In my experience, the NGK 6 plug is closer to the Bosch 5 heat rating. The higher the heat rating number on NGK, the colder the plug. It is the opposite for Bosch. Don't forget that your stock VF setup is running rich by design which helps keep your cylinders cooler. Only if you further tune your engine to run leaner, might it be necessary to move to the NGK 7 plug.

 

Wecome to the School of 1999..LOL!!!!
Trust him HE HAS helped me HUGE with my VF set-up!

Stacy

 

1999 Porsche....thank you SO much for all your help so far....looking forward to your new reply....

*Update* installed the NGK BRK6EK and the car runs great WOT...but still studders under partial throttles, even highway, but as soon as you go WOT, the car pulls very hard and smooth.....

I guess the ONLY plug that hasn't done this to me has been the Bosch 4 ground electrode plug(FGR6KQC). Why is this happening?

Also on the dyno I did realize my air/fuel ratio's were in the 10's on idle and partial throttle(needs to be in 13's or 14's even I would imagine) and went to 11.5-11.8 under WOT which was fine......could it be the ecu tune VF gave me from 2004 that may need to be reprogrammed?

The reason I'm kind of skeptical on the ECU tune being the issue is because the car ran fine a week ago with the Bosch FGR6KQC plugs in there.....however temps here were in the 50's if that matters....

 

Best Plug, Bosch fr6 ldc, will clear up your plug probs. Promise!

 

FWIW, a 3.4 litre engine with VF supercharger kit (with engine in good mechanical condition- ie solid compression- something you may want to check when you have the plugs out-, good plugs, no intake air leakages etc) should make 420 crank. If you factor a 20%drive train loss that puts you in the ballpark based on what you made on the dyno i believe.

 

update......all 6 coils were cracked! So I'm sure that's a HUGE part of what was causing my car to run rough and robbing quite a bit of power. I'll throw the brand set in that has the upgraded 997 parts in for tomorrow(tuesday) that I got from VERTEX auto and let you know what happens. I'll get it back on the dyno right away and update everybody with the dyno #'s within the next day or 2. It made 333rwhp before, so we'll see what the new parts do....

 

*update*....installed all 6 new coils...still runs like crap on idle and partial throttle acceleration....full throttle the car runs perfect.

IM OFFICIALLY CLUELESS...I have no idea what to do now....any thoughts? ideas? suggestions?

 

Do you have a scanner to look at various engine sensor readings?

 

getting it checked over right now by my performance shop.....no lights on the dash or anything no CEL, but my feeling is maybe its a bad MAF resistor or perhaps a boost/vacuum leak. I guess they'll let me know soon enough when they throw it back on the dyno and finally MONITOR BOOST THIS TIME Then I'll post the graph on here.

 

*update*....The shop pulled my exhaust apart and found that I blew apart the catalytic converters and pieces of them were stuck on the o2 sensors causing them to malfunction. They put new exhaust pipe in to replace the catalytic converters and put it on the dyno....

On the dyno it made 5.9lbs of boost and put out 351rwhp(SAE corrected) which I'm thrilled with! Maybe it may make even a bit more after they clean the rest of the exhaust out(I believe they told me the mufflers got clogged with catalytic converter material as well) so may even free up a few more hp.

The car a few weeks ago put down 333rwhp and I wasnt too thrilled with that, so I'm definitely a bit more happy now. I'll know more tomorrow as they're going to re-dyno it with a new air K&N air filter(one currently on car is 5 years old and very very clogged) and the new 02 sensors(which will hopefully make the car run smooth )

351rwhp with a 20% drivetrain loss nets me right at 420bhp...and thats exactly what VF rates their kits at for the 99-01 porsches, so I must say I'm very happy!

next step is to install my spec stage 2 clutch and a Aasco lightwight aluminum flywheel(13lbs lighter than stock) and see what the car does then power wise!

 

Good for you!
Congrats.........let us know how that LWFW works once you get it installed.

Stacy