Engine Stutter at high rpm's under boost
 

This is kind of a generic performance problem a buddy is having with a boosted motor so I thought I would post here for some theories. We were at the track Friday night running his car and he ran a respectable 12.7 @116 mph....15 lbs of boost. With more runs, the car started to break up at high rpm's. It got worse with each pass. All the wires and coil were replaced, plugs are gapped at .025 and are a 7 heat range. Plugs look good when they are pulled with no fouling. Data logs are clean with a good A/F through each pull. There is no interuption in the crank signal on the datalogs either. I suggested going to 1 heat range hotter plug to see if that would help with a better burn under high boost and rpm's. Any ideas as to what the issue might be?

It could be bad gas and timing being pulled. This is just a guess.

Sounds like a little aggressive timing up top. What's the boost, engine configuration and timing in the upper rpm's(6k and up).

Mine was doing the same thing until I adjusted the Air metering map on the EU. It tricked the computer in to thinking less air was comming through, helped lean me out a bit and after looking through the datalogging it added a few degrees of timing up top. So it looks like when it is adjusted it reduces/ increases injector output and Adds/ Pulls timming.

The car is running Hondata right now with a very conservative timing profile throughout the rpm range. Engine is a 2.2 L Honda motor. 9.4:1 compression Benson block, full race head, stock cams, MSD ignition system throughout. 15 lbs of boost. T3/T4 turbonetics turbo.

Ummm www.honda-tech.com . Lets see you got a h22 motor right, port and polished head, nice turbo...whats up with the fuel, your car is detonating bro. I know you know of JOTECH, call them ask for nick or mikey..tell them joey from 350z forum told you and you get a discount. 15lbs of boost on that motor should make over 500+...fix it for ya blow it...im a honda guy too

It's not detonation. Plugs are perfect. There is good A/F and there is no knock whatsoever on the data logs. I have heard detonation before and this is not it. Timing is dialed waaay back and it still does it. It's almost like the spark is being impaired by the higher boost pressures. Very odd.

Oil in your intake? If it's excessive from PCV then it will cause this.

what type of plugs? copper, platinum or iridium's?

i've heard that the copper & platinum plugs don't hold up well at high rpm
& that the iridiums do a much better job.

not sure if that helps...

My VQ35DETT (APS TT/ 8.5 PSI BOOST)had a Same Problem above 5300 ~ 7200 RPM
:confused: :confused:

Valve cover is vented to atmosphere. PCV has been removed.

I get the same thing in 5th gear sometimes above 5k rpms. I'm installing an oil catch can and swapping the plugs next week to see if it helps.

Well...went through everything on his car. Replaced the wires, coil, and still had a problem. Pulled the distributor apart and replaced the ignitor module. That seems to have fixed it. Pain in the ass!!! Apparently they don't like 9000 rpm's much.:rolleyes:

I was just about to say...on that Honda..its likely blowing out the spark. Looks like you found the problem.