I've been searching for probably 20 minutes now looking at various threads concerning boost taper... I haven't found anything for an VIII.

I have a BR330, tuned. It spikes at around 21 PSI and tapers to around 19 usually in any gear, around redline. Mods are 255 FP, Forge MBC, Full 3" TBE, BR MAF Kit/Filter, and a Tune that I think was created pre-FP/MBC/3" DP.

But what I noticed is that in 4th and 5th, I never see past 20 PSI and it's never seen 20 in 4th on the highway. If I slow down to around 55-60(3300 or so RPM, maybe lower) and gun it, I will be lucky if I see 18-19. Is this because of boost leak or the stock, normal boost taper? Is it because I don't have the proper load on the engine at that speed? Should I be going to 3rd(Seems a bit fast for 3rd)...

Any insight? I don't THINK there's a problem however the car does seem fairly weak in 4th gear(I know Evos are not known for amazing top end).

 

thats odd. You should spike higher in the upper gears

 

Alright it looks like I'll just crank the boost!!!







Kidding.

 

If nothing was changed in your mods, I would start doing a boost leak test.

 

I bought the car used with the mods listed.

Would a boost leak only show itself in 4th?

 

Did you buy that car from a kid in Strongsville?

 

Yeah, I met you at the lot.

 

Try doing a roll on 3rd from 2500rpms. Note the boost spike and rpms it hits.
Then try doing it in 4th and note it as well.

You should be hitting a higher spike in 4th.

 

sounds like a boost leak....trying doing a leak test and see what your holding

 

I am having the same problem in my IX but I don't have near the mods.

 

I did this today and it did spike a little higher. Like very slightly. About 20 psi in 3rd, 20.5 in 4th.

 

Yeah I remember you of course. I'm still a little hazy on if you bought it from the kid in Strongsville. If so, I hate to let you know that that car has been ridden hard and put away wet. Really wet.

I'd definitely do a boost leak test. PM me if you want to know more about your cars history.

 

I just noticed your using an autometer gauge those things are crap. Your gauge might be off.

I had a buddy whose gauge read 6psi higher then what it was supposed to.

maybe look into getting a good electrical gauge, they're a whole lot more accurate.