Hello people. So the car runs really nice and strong at 12psi, however I have noticed lately, that at higher boost levels (car was tuned by Evans at 16.5 psi, tends to hit 17-18 in this nice cool weather, no big deal). Anway so on the highway I did some high boost pulls and the car misfired pretty badly. I do have 98 Octane in it, and the logs show no knock, or pullng of timing so what could it be? I have 110,000 miles on the original coil packs. Car has been boosted since 60k. I also run water Meth with may or may not contribute?

Also, interestingly enough, it sometimes does not do this during a high boost pull if I have been beating on it and the EGTS are in the 1,100-1,200 range. Basically its like if I do a few pulls back to back and heat up the turbo (egts etc) it is less likely to misfire)

I had to pull on a modded Audi RS4 today in low boost, took slightly longer than it should have

 

Sounds like spark blow out to me. Yes water/meth will be a big contributor to this. I don’t know what plugs your running, but it may be as simple as needing a re gap or replacement, likely if coppers.

It’s possible if you got tuned at a particular % level of water and may be off in your mix with more water. water doesn’t burn so more water % in your mix will tax your spark for sure. Make sure your ratios are right. As a test you could run a strong meth % and see if the problem still persist.

Coil pack …or packs, maybe. But usually these go out all together I think, not just at high load/rpm. You would hear it miss at idle.

 

is it miss firing during the pulls or during light throttle high rpms?

 

during the pulls......... once it hits full boost in the higher RPMS. Plugs only have 1100 miles on the, and they look good, I just checked em out gap is like .30ish

 

Why are you running water/meth with 98 octane? I can see using it for 93 but not 98.

 

I don't normally run 98, I just recently did it because it got colder out and the car occasionally hits 18psi (tuned safely for 16), (just extra precaution). I also did it because at first I thought it was detonation, of course looking at my datalogs, it's not

 

are you using the NGK 8's or 9's?? does your boost guage match your map sensor? Also check your battery voltage during the pulls and regap your plugs to ~.22 I had a big miss fire issue at first with sunco 104 and I replaced the battery, map sensor, and tightened everything up including all vacuum lines and the miss fires went away.

 

Your plug gap is a bit too open for your setup. Gap the plugs to around .020" and it should clear it up. Also get some Iridium 8's if you aren't already using them.

 

thx guys, im using NGK copper plugs(7173), heat range 8's.I'm going to put new ones in, and get them gapped appropriately

 

Gap them down and check where ur boost cut is. I thougt my car was spitting turns out I was hitting my boost cut on spool up. Little tweak of the boost control and bam all good