[SohcVtecCrix]

okay well i didnt fix my header yet but i noticed that my car has a really hard time revving past 6.5k rpm. At 6.5rpm my car makes that pulsing noise that is almost the same as a CRX HF reving past 5k. Whats wrong with my Motor if there is anything wrong...and i know for a fact power drop off beyond 7k is allot more than my friends 92 civic si. his car pulls all the way to 7.8k rpm easy while mine struggles past 7k.

compression
190,190,190,190

 

[CRX-RX]

Timing??

 

[PSIKOTICsi]

if you are runnin a pm6, how do you control the vtec? what activates the vtec?

 

[sonictronic]

Are you sure you dont have an 88 ecu?

The pm6 ecu on 88 models has a 6500 rpm redline and ~7000 rpm fuel cut. I dont know if the 89-91 models are the same or different.

I also heard that the ecu will substitute around a 6500 rpm fuel cut if the car is cold. So check your coolant temp sensor to see if it is working right.

I would also suggest upgrading to a p28 ecu so you will have the correct fuel maps when vtec engages and then you will have a 7500 rpm fuel cut. It will also engage vtec when it is supposed to be engaged.

Other than that, all i can think of would be the timing and vtec actuation like PSIKOTICsi and CRX-RX said.

 

[DonkeyKong]

That sound after 6.5K could be you hitting some sort of fail-safe rev-limiter. Are you sure that your vtec is engaging? Also WTF were you trying to accomplish by revving a HF past 3K rpm? they simply don't have much steam after 3500 rpm max.
-Mark