I have an observation and need some help. I just installed an Autometer mechanical boost guage and noticed that the peak boost is only 16 psi (at 3500-4000 rpm, 2nd gear+). Assuming the guage is OK and the setup has no leaks, what could be the cause? (I'm making the assumption that the guage is OK as it runs a constant 20-22 in/hg max vacuum on decel - so no leaks there). The only mod is a Buschur intake filter. I run 91 Octane fuel (92 when avail).

I've done a search with no real help. Any suggestions???

Evo2003.5

 

Hmmm...peak boost should be 19 psi...but maybe that's with 93 octane??? Any of you tuners know what's up here???

 

its just barely spooling up so wait till you hit around 6500+ thats when you hit the peak boost.best to look at it is shifting from 3rd to 4th gear,i usually shift before 7k when i was tuning my boost controller.

 

Where did you tap in for your boost gauge.

I am running on 91 octane and it is running 19 till about 4500 then settles to 16 4500 on. You will first need to get a boost controller very good mod from ams it about 60 dollars and set it to 19 psi and it will stay there till 6500. you definately have a problem

 

Tighten your IC Clamps, mine leaked form the factory along with everyne elses...

 

really!?!?!?! man i need to check myn! thanks

 

Is it supposed to peak at 19 in every gear? I find it holding at 1.3 bar in 4th and 5th, but 2nd and 3rd seem to peak a little lower.

 

Thanks for the input. I'll check the IC clamps -- didn't even consider that! Right now they're covered in snow and ice, so I'll have to wait.

I tapped-in to the rubber hose on top of the intake manifold, which should hopefully give the best readings. I noticed today that at about 4000 rpm, it jumps to 17 psi for less than a second and backs off to 15 psi.

As I understand it, stock peak boost is accomplished at 3500 rpm at WOT, with it backing down to 16 psi closer to redline, to prevent detonation.

Evo 2003.5

 

That is what mine does. Autometer gauge tapped in the same location. I even went as far as checking my gauge calibration, I did a pressure test and have no leaks. I guess this is just the way some cars are. I still made 240 whp stock with lower boost so I'm happy. The only time I saw it peak up to 19 psi was on a very cold day (below freezing). Most of the time I see 17 peak and taper to about 15.5 psi by red line.

 

Wierd...

Mine always would run up to 19, then quickly taper down and hover at about to about 16-16.5psi. Now I'm running an MBC and can hold it at 19 (where I set it in this colder weather) till redline

Jason

 

Ya boost varies on stock evos, most will get 19 psi peak but some can only hit 16-17. I think my car is somewhere in between. My car stock hits 17.5 psi peak on the summer time and about 19 psi on cold days (like below 45 degrees).

 

Are any of the hoses pinched between the intake manifold and your gauge? I would check that also. I have an Autometer boost gauge also, and it reads just fine at 21-20psi then tapering to 19 until redline You gotta love the headbang!!

 

my peak has hit 1.48bar (approximately 21.75psi). I usually see about 1.37bar (approximately 20.14psi) and then it tapers down from there. It seems like mine runs a little high...