What do you boys make of these plugs?

[Jon K]

These are NGK race plug V Grooves in heat range 9 (very cold plug) on the GTI VR6 Turbo racecar. Today the car developed a miss at high TPS levels so naturally we replaced the plugs. The owner of the car insists it is normal for this car to eat plugs about every 200 miles or so. We're running 50# injectors batch firing. Its a low compression 8.5:1 motor forged everything with ~10 psi of boost peak. One thing I will say - I am not content with the tune AT ALL. The car is turning a 12.0 - 12.6 AFR at IDLE. My buddy who owns it seems content with that but that is MUCH to rich in my opinion, however the plugs are not all showing a "rich" wear.



These are all used plugs. Left shows the electrode center ceramic portion clearly white... the next is grey and the final is BLACK. The final plug came from cyl # 6. The car is batch firing so I would think that all of the plugs would wear relatively evenly. I am going to have to look at his tune - 12.6 idle, even on a trackcar/rarely street car is way too rich. The car does have a turbo cam in it so it makes it a little tough to get a smoothe AFR at idle, but still.

[ericcamaro]

damn judging by that last plug I would say you are getting some seriouse blow by on #6 or a stuck open injector, i dont think there are too many other causes for a plug that black. especially since the first one is white and looks unused.

[Jon K]

#6 cyl is notorious for running a hint lean compared to other cylinders too... that's the weird ****. Hrm.

[Martin in Bellevue]

I think there isn't enough disclosure here. Is there a water/alcohol/windshield washer injection system mounted nearer the #1 intake runner? What is the wideband setup providing the 12.6:1 afr reading? The Innovate LC-1 analog output to cme can be set to correct for that pig rich idle, to the extent that the batch firing stuff allows. Has he, or anyone with a similar setup been happy with injectors with 3x flow from stock, without more appropriate management? Maybe at 10psi, he should look for injectors closer to 30 something # flow, or less. Is there a fmu used?
Maybe more-stock injectors would work if backed up by a pressure sensing split second psc-001 driving additional injectors under boost. It is programmable for such an application & might make for a happier drive.

[joshua43214]

plug #1 is too lean.
plug #2 is normal if the car was alowed to idle for a short while, or if plug is too cool. You can see the small ring of white arround the electrode showing it is trying to self clean but its too cool.
plug #3 is too rich

also, notice how the electrode is mushroomed on #1, this comes from running the wrong plug on the waste side. The small amount of ash on the ground is from improper ignition, maybe related to it running to lean to sustain full burn, or because the plug is too cool. It may be burning some oil, but I suspect it has more to do with it having the wrong plug, gas will leave ash as well as oil, especialy if they are running an additive.

None of the plugs show any of the glazing that typicaly comes from running the engine really hard, so they can safely use a hotter plug I would think. You should be able to go with a fairly hot plug at only 10psi with no real danger of drilling holes in the piston tops. It might be worth running a carbon clean to remove any crap from the cylinder that plug 3 came from since carbon in the cylinder will cause detonation.

I have never seen a VR6 run well with single electrode plugs, the correct plug will wear much better as well. Where the injectors sent out to be balanced? if they are running batch injection, they all need to have identical flow rates.

[Ausmpower]

Were the injectors flow tested and matched?

What's the fuel pressure doing under boost?

What condition is the ingition system in?

From my experience with modified turbo's (I used to own a modified Liberty RS turbo running 25 psi and a number of 13b turbo rotaries) I'd say there is a weak link in the ignition somewhere. I'd be looking at the coil(s) and leads first.

It could be caused by the ignition breaking down under boost, excessive fuel pressure or a combination of these.

Those NGk's hate rich mixtures and if given the opportunity to foul they don't recover.

That #6 plug definately wouldn't be firing under boost now in that condition that's for sure!

let us know how it goes.

Ross

[Ross]

Hey,another Ross!

[632 Regal]

#1 is spooky lean, thats dangerous. Not very close across the board there.

[Ross]

Did fresh plugs cure the miss? I'm very curious why the first plug is so clean esp. given the AFR. Does this thing have individual coils? Maybe the ign. weak at some cyl????