# Spark Plug Selection



## Matt_B (Apr 22, 2010)

Hi Guys

I am having some issues with meth related misfiring. I am running a GT2871R turbo on a 1.9L engine with low comp pistons (8.5:1). 
When I run with EBC off (12psi) no issues
When I run my low boost setting (21psi) no issues
When I switch to my high boost setting (26psi) - I seem to get lots of stutter, like misfiring under full load.

Currently running a 7 heat range NGK plug gapped to 0.028.

I am not spraying that much meth, AEM middle nozzle, starts spraying at 8psi and I have dialled the max spray back past the point I boost to so I dont think I am reaching max flow.

Question is, 
I am thinking of doing the following.
Fitting some 6 heat range plugs 
Reducing the plug gap.

Does this sound like a plan or am I missing some other possibilities??

Matt


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## Krieger (May 5, 2009)

how much are you flowing? You could be getting tons of timing pull from simply being way too hot and your motor is doing everything it can to save itself.

the 2.0t on a K03 can easily handle 4 or 5 gph, so with a larger turbo charger, running much higher boost, you can flow a bit more most likely.

try increasing your flow rate, and % of meth and water are you running? Water cools much better than meth, plus has an infinite octane rating, but can douse the flame front if there is too much, whereas meth usually evaporates before it can even enter the cylinder, and dissipates alot of heat as well, and has a pretty high octane rating as well (112 i think). 50/50 is a good place to start.


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## Matt_B (Apr 22, 2010)

Hey Krieger, thanks for the reply. after 50 odd views I was beginning to think no-one would come back to me.

The AEM nozzle sizing is weird, the nozzle states 315 cc/min but this is at a pressure of 150 bar and the later pump pushes 200 so if its a linear relationship it will be closer to 400 cc/min

My EGT's are well under control under normal use, nothing really over 700 degrees C. I should state that my map is mega rich and bottoms out the lambda at .751 under boost. Hence I am thinking this is about drowning my ignition rather than a symptom of massive timing pull.


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## Krieger (May 5, 2009)

400cc a min might be a bit too much for your motor, im not sure... hmm... try swapping down to a 225 or 300 or something.

also, running rich is also a side affect of either running super hot (your dumping fuel to save the turbo and internals), or your meth and water are naturally just fattening up the AFR.

what meth % you running? try a few logs with straight water, some with 50/50, and some with 70%+ meth. check timing, fuel, knock, egts, everything. if all seems well, you are probably looking at running too much WM and have two options: tune for it and take out fuel and make some serious power, or remove the WM in small amounts and see where your sweet spot is.

removing fuel is where the gains are to be made in WM setups, not just in having colder IATs. Don't go crazy though. Running lean isnt a great thing if your WM quits on you. lmao

im not at all familiar with the 1.9, but ill see if i cant do some homework.


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## Matt_B (Apr 22, 2010)

Hey, 
I should really tell the whole story here.
My car is a 1.8T which is fitted with 82.5mm wossner pistons and forged rods, which changes the displacement to 1.9L 
I am currently running a 50:50 mix of M1 grade meth and purified water. The car is running with no N75 or N249 and uses AEM truboost boost controller, and is on Revo Stage 3 software. 
I drive the car on a daily basis and have one of those LiquidTT gauges which spends most of its time on mult gauge setting showing inlet temp, coolant, oil temp and EGT, and like I said the EGT is well under control - In actual fact I think its a very conservative MAP that runs rich in order to keep the temps so low.
Your idea to experiment with different ratio's is interesting. I wonder if the mix had "gone off" in my shed. I bought a 25L drum of M1 back in March and have about a third of it left. I get purified water and mix up 5L batches of 50:50 and keep them in my shed at home to top up the bottle in the car. I might make up a fresh batch and see if things improve.
Temp over here in the UK is quite cold at the moment and intake temps run around 10-15 degrees before I start to spray so maybe everything is too cold to begin with.

The reason I was looking at plugs is that I have read a lot about BT setups and spark gap, with a lot of recommendations for a tight gap ~0.023 to prevent misfires. The heat range thing also appears to be open to interpretation - on one level the advice is that if your car is tuned that you should go colder. BUT factors such as compression ratio, boost levels, humidity target AFR etc all play a part. I have lower compression ratio, so by rights I should run a slightly hotter plug perhaps. 

I have some logs from the last time out, but have no idea how to post them on here


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## Krieger (May 5, 2009)

start simple and cheap. Meth and water dont mix exactly 50/50 when you dump in a cup of meth into a cup of water. the meth binds to the water and you end up with 50/50 volume, but not real 50/50, if that makes sense. there are some calculators floating around to better help you find out what you need to mix to hit it... but honestly, I always run more meth than water regardless... too much meth hasnt been a bad thing for me yet. lmao

if the mixes dont fix it, lower your flow rate, if that doesn't help, change your plugs to a tighter gap. if that doesnt work, go colder, or warmer.

also, think about this... if your tune is running rich before you spray meth, your defeating a huge portion of the purpose of WM. You can take out fuel since its being replaced with meth. You might simply be flooding the motor with so much fuel that it just doesnt operate as well as it would if you ran it a bit leaner.


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## Matt_B (Apr 22, 2010)

Thanks Krieger, thats exactly what I am gonna do.

I will try and adjust the meth in my tank first by making up to 50% w/v and see what that does.
I will then start spraying a bit later, and reduce the spray. Then its into plug land for plugs n gaps.

Cheers for the advice dude.


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## Krieger (May 5, 2009)

Matt_B said:


> Thanks Krieger, thats exactly what I am gonna do.
> 
> I will try and adjust the meth in my tank first by making up to 50% w/v and see what that does.
> I will then start spraying a bit later, and reduce the spray. Then its into plug land for plugs n gaps.
> ...


:beer:


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## Matt_B (Apr 22, 2010)

Update

So I decided to throw another 500ml of meth in my tank the other day to see if I could rectify my mixture.Still got the stutter of doom when goinfg WOT from low revs in 4th gear.
So I went for some BKR7E gapped down to 0.022. Took it out for another run (25 psi) and the car pulled to the redline perfectly 

Having said that I carried on driving for about another half mile and after going round some tight bends I put my foot down in 2nd and I got a rather large backfire 
Needless to say I nearly soiled myself, drove like a saint for a couple of miles to check I hadnt broken the car, then gave it a little burst of speed and all seemed well.

If I can find out why I backfired then I will be happy, as the small gap seems to be working for me on boost. 
As soon as I get a new battery for my laptop I will do some logs and post up.


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## DMVDUB (Jan 11, 2010)

Extra unburnt fuel hitting hot pipes = Backfire / Afterfire

My car did the same thing when I first started playing with the W/M. I'm used to it doing it during NLS but it was doing it randomly... turned the fuel down a bit and now it's all good.


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## [email protected] (Jan 13, 2005)

Matt_B said:


> So I went for some BKR7E gapped down to 0.022. Took it out for another run (25 psi) and the car pulled to the redline perfectly


Congratulations! Your cylinder pressures were too high for the electricity to make the jump. That's a good problem, indeed. :thumbup:



> If I can find out why I backfired then I will be happy, as the small gap seems to be working for me on boost.


Do you have a nozzle posted after the TB without a solenoid, by any chance? Otherwise, Krieger's advice is most probably spot on.


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## Gu4rDi4N (Mar 11, 2005)

Two weeks ago i have the similar problem with NGK 7 Iridium IX.

Needs gap from 1mm to 0.6mm and solved 

Amazing this "stupid" problem...


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## Vegeta Gti (Feb 13, 2003)

i dont think i saw you say it, but when do you START spraying? perhaps backing off the spraya little later will help. it did for me..i start at 11psi full at 20. 400/ml nozzle. billet 3071r, 9.5:1 stock disc 1.8t with a ton of other goodies. i also run [email protected] .024. no issues with or without meth on plugs/misfires,etc. and we have reaally crappy 92 that is usually 91 out here.:banghead:


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## Krieger (May 5, 2009)

400ml an hour at 60psi, if your using Snow's nozzle, is freaking HUGE. your pump is flowing more than twice that, and at 4 times the pressure, you flow twice the fluid... do the math and it's 

probably too huge...

you are gonna want to step it down. the water cannot cool the air as well if it's super saturated.


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## Matt_B (Apr 22, 2010)

Vegeta Gti said:


> i dont think i saw you say it, but when do you START spraying? perhaps backing off the spraya little later will help. it did for me..i start at 11psi full at 20. 400/ml nozzle. billet 3071r, 9.5:1 stock disc 1.8t with a ton of other goodies. i also run [email protected] .024. no issues with or without meth on plugs/misfires,etc. and we have reaally crappy 92 that is usually 91 out here.:banghead:


Was starting to spray at about 0.6 bar (9psi ish) and have now moved it out to 0.9 bar.
Car seems to like that better, especially in this cold weather.


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