Quote:
Originally Posted by shaneguags
everything you stated was checked and fine, I asked about maf, pvc, hosings, injectors, and coil ignitions, all was checked out. only thing I think is the issue are the spark plugs. he said he'll do it again for free to check if they bad and he said I can upgrade them even more but not needed. he gave me NGK 97968 step 1 colder plugs, stating if doesn't need more unless it's past 700whp. however, everywhere I'm seeing recommends NGK 97506 even just on stage 2 FBO. also, he stated he gapped them to .018 because he found that works best and have had issues with even .020. he said he gaps all turbo cars that are tuned to .018 for the most part and have fixed issues, but to me that doesn't sound right. I heard cars near 500whp should be at .022-.023 and right now I'm pushing 535whp on 21PSI (not crazy high boost). he said I can choose what I want with no extra cost, but if they issue still persists, I'll have to pay again with installation
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I don't like saying this but your mechanic is kind of uninformed about the spark plugs. You never gap based on the "prescribed" limits not two cars are ever the same, that is how you get rough idles.
At 500 whp you probably will need to start gapping down, but generally you would start at the stock gap and go down as needed, so start at 0.028" and gap down based on misfires due to the spark plug being blown out. But at 500 whp I wouldn't mind starting at 0.026 or even 0.025 then going down from there - I wouldn't go to 0.022 or 0.023 right away. You always want the largest possible gap to rpomote complete combustion.
BTW a gap of 0.018 is insanely tight for 500 whp, and generally in any application. At that point you should be looking for more powerful coils rather than gapping down that much, and I would wager this is what is causing your issues.
ZM2 was having some issues awhile ago on 0.023" gap iirc, and it went away after increasing the gap to 0.026". BTW
ZM2 are you still on 0.026" gap with your turbo pushing essentially 500 whp? If this is the case then shane you should be safe around this range too. Maybe you can start at 0.025" (and move your way down as necessary, but remember you want the largest gap possible not the smallest one possible.
Also your mechanic is wrong about the heat range of your plugs too... The stock ones are already 1 step colder than the normal n55's and 2 steps colder than the n54 and are the same heat range as the GTR's which run fine up to 700 whp. You also don't want to go colder if it is not needed because that also causes incomplete combustion and misfies although these engines seem to tolerate it just fine. But just letting you know so you don't waste your money on ngk's for no reason. There is alot of misinformation about plugs out there and unfortunately alot of shops and "tuners" are misinformed too, and I generally use this as a sign to weed out the good shops from the not so good shops.