boost drop off at high rpm's?
 

Ok so I have a 05 evo with basic mods such as hks 272's, just a hks catback, walbro 255, 750cc injectors, intake etc etc. the problem is at wot it will build boost for a split second and then just drop... theres no boost leaks so im wondering if maybe it could be a problem with the wastegate?

Come on guys I need help ASAP :'(

like when you floor it you hit full then it starts to die? or like you hit 20 (for example) and then it immediately goes down to like 8?

It's normal for boost to lower a few psi on the stock turbo at higher rpms.

What PSI is your boost set at and what does it taper off to?

It's a 16G, it won't hold HUGE boost up top. Also could be your boost controller, makes a BIG spike then falls off.

How much boost are you running? Wastegate flapper might not be sealing off all the way.

Lets see a log.

It's typical for the pressure to drop after the spike, and really not much you can do about it on a stock turbo except tune around it. There are ways to lower the spike a tad and raise the pressure after the spike to some degree to match (using EcuFlash), but a lot of it has to do with the wastegate itself and the housing not being able to hold that much pressure at higher rpm's.

No I know its not gonna hold the boost up top, its set for the stock boost but it wont even make it to 19psi at wot it will hit 15psi at about 4k then just drop off totally... And I have no logger or else I would take some logs to post up. Normally it will hit around 18psi and drop off to 16 and occasionally spike at 20 and drop to around 16. I'm pretty sure it has something to do with my wastegate, I'm gonna pull the turbo today and check everything but what should I specifically look for? Before I pull the turbo I'm gonna check for boost leaks one more time.

A ~3 - 4psi drop could be 'normal' on an 8. How are you controlling boost? Are you logging boost or just looking at the gauge while watching the road :) ?

What DV/BOV do you have? Do you know how much WG preload you are running? Stock catalytic convertor?

I need to get a logger, it has the HKS SSQV and it has the stock cat. And its a MBC and I just check the boost by the gauge.

I worked on it a lil today and when driving around at WOT it started sputtering at 6k, the boost held a little better some times but still kinda having the same problems...

well i have an srt-4...so that isnt gonna help you. lol. but then again my car is made by :mitsu:

Say what?

Only thing made by mitsubishi on the srt-4 is the TD-04 turbo.