im having this problem with my evo. Whenever i step on the gas a lil bit hard , right around 3500 - 4000 rpm the rpm drop 500 and then moving back up . Boost stay the same. It only does this one time whenever im boosting. anyidea?

 

Do you mean the rpms shoot up 500 rpm, then fall back down? If so, it sounds like a slipping clutch. It is not possible for you to accelerate under full boost and drop 500 rpm.

 

humm but when i launch it its fine no problem at all . Only when i accelerate slowly thats when its happen. Like if i floored it it will run fine .

 

are you backfiring when this happens?

 

i think so

 

Yes, that's because the clutch slips at peak torque with high load. The higher the gear, the more likely it is to slip. We hit peak torque right where we hit full boost in the 3500-4000rpm range like you said. On a launch, we are above 5k (I'm at 6k), and it's only 1st gear, so it's less likely to occur.

To test my theory, go out, put the car in 5th gear at 2500rpm, then floor it. When the boost builds fully, the rpms will jump up several hundred RPMs, the car won't accelerate much, but then the rpms will catch, lower down to normal, and then you accelerate normally. That's a slipping clutch.

 

ok i think you've just answer all the question lol thanx i need a new clutch