Misfiring On High Boost

[ReflextioN]

My car runs fine on low boost (7 psi) but on high boost (13 psi) it starts misfiring.

Only mods are a BOV to atmosphere, Boost Controller and Exhaust.

S1 R33 RB25DET.

New plugs, coils look fine, AFM looks fine, could the fuel be doing this?

[StealthX]

try gapping your plugs down bro.

[ReflextioN]

i dont think that will help because it runs smooth on low boost, and misfires on high..

is it easy to do myself?

Edited September 11, 2010 by ReflextioN

[97R33MSPEC]

gap your plugs mate. try em around .75mm with high boost is higher cylinder pressures, harder for the spark to jump.

[ReflextioN]

makes sense, ill try that, thanks.

[StealthX]

i dont think that will help because it runs smooth on low boost, and misfires on high..

is it easy to do myself?

ok then, don't take my advice.

gapping your plugs should do the trick, but if not, then it may be your coils. Even though you ruled them out, try wrapping them in electrical tape so they don't earth on the head, sometimes the insulation wears out...

[ReflextioN]

haha sorry mate i assumed that it should work regardless of boost, i didnt know higher boost affects the spark, but now i do

Am getting it them gapped tomorrow and i will get the mechanic to double check the coils maybe ive missed something.

[StealthX]

haha all good bro

For future reference, what's happening is the spark is too weak to jump across the gap in your plugs, and the higher boost level is 'blowing out' the spark, and misfiring. When you gap the plugs down the gap is smaller and the spark has a shorter distance to travel

Good luck dood.

[defari]

stock ecu? if so, too much boost.

[Jezza-gtR]

haha all good bro

For future reference, what's happening is the spark is too weak to jump across the gap in your plugs, and the higher boost level is 'blowing out' the spark, and misfiring. When you gap the plugs down the gap is smaller and the spark has a shorter distance to travel

Good luck dood.

Not 100% correct. The spark is not ''too weak'' the fact is higher boost is causing the engine to rev quicker so air veloicity is alot quicker and will blow out a large spark (big gap eg. 1.1mm gap). So yes a smaller gap (and spark) is used on turbo cars becuase of this reason.

Cheers.

[StealthX]

Not 100% correct. The spark is not ''too weak'' the fact is higher boost is causing the engine to rev quicker so air veloicity is alot quicker and will blow out a large spark (big gap eg. 1.1mm gap). So yes a smaller gap (and spark) is used on turbo cars becuase of this reason.

Cheers.

Isn't that exactly the same thing I said, just worded differently?

i.e. too much boost blows out the spark, cos the gap between the electrodes is too large, hence the spark is not intense enough to jump the gap before the air blows it out.

[ReflextioN]

Do i still need to gap the plugs if they are iridium?

Im getting a new set tomorrow.

Edited October 6, 2010 by ReflextioN

[-_-StRyDeR-_-]

dont run iridiums...

Do i still need to gap the plugs if they are iridium?

Im getting a new set tomorrow.

[mad082]

+1 for not getting irridiums. in my opinion they aren't worth the extra money.

if you just get new plugs (even if you do get iridiums) that don't have -11 on the end of the part number then they should be pregapped to 0.8mm.