boost dropping at high revs

[Ady]

what is causing this?

its like boost creep, but in reverse. say i put my foot to the floor in 3rd gear, my boost hits 15psi for a second, then settles at 14.5psi. which is fine, it will hold 14.5psi just fine until the engine revs up to about 5k. but from then on it steadily drops to 14, 13.5, 13 psi. maybe even lower if i kept going!

what could it be? cracked wastegate? cracked manifold?

(its the original ct9 by the way)

 

[dac69er]

mine does this. i was told it could be the intake pipe but since taking the air intake assembly off and just having a meshed intake it still does exactyl the same, not sure why though, may be exhaust restriction. what size exhaust do you have? do you have a decat?

 

[Cooch]

How higher revs are we talking? Its only a small turbo and small engine so a little boost loss at higher revs is to be expected.

 

[dac69er]

mies drops from about a bar down to about 0.85 maybe a bit less. starts dropping off after about 5k rpm

 

[jimmer]

mine did somethin like this as well, found out that my turbo was on its way out. It just started loosin boost on higher revs, dunno if this would be the same on you cars, but just what happened to mine.

 

[dac69er]

mines should be fine. its always done it. no smoke and checked shaft play and it was rebuilt a year ago.

 

[Ady]

ive got a 2.5" decatted system. so i shouldnt think its exhaust restriction,
the turbo is on its last legs anyway, as it smokes like a slag, if i ever get round to changing the turbo then i guess that might solve the problem.

maybe the ct9 simply cant hold 1bar!

 

[Ted]

i tried everything to find out what was wrong when mine did this, it just the ct9 cant keep up when theres a bit of wear on it and you are running higher boost. theres nothing wrong with your car.

 

[GP82]

I think it's because the wastgate starts to open up early and the stock dual port actuator being weak. You need to setup for a better way of controlling boost so you can hold peak boost for longer. A good ebc + hks actuator will improve it. I don't think there is anything wrong with the ct9 unless the wastegate housing has cracked.

 

[Ady]

i have a hks actuator

 

[dac69er]

i have hks actuator and profec b ebc. mine still does it at 0.75 bar (my low setting) but not to the same extent.

wear is minimal on my ct9 as it was only rebuilt last year

 

[TurboDave]

Either the standard efi pipe is restricting it because its shit or the turbo cant flow enough air at higher rpm and is working at its maximum.

The ct9B will drop off more boost at higher rpm than the ct9A.

 

[dac69er]

just had a thought, i do have a ct9b so that probably some of it! must be the turbos fault on mine then as i have only mesh on the turbo and a decat and straight through system

 

[Dave.]

could be what dave said ^ good point

I'd place my bets on a bad actuator though, i had the same problem and a new actuator sorted it perfectly lets you run more boost safely and smoothly too!

Dave

 

[dac69er]

both me and ady have an hks actuator and both have boost dropping off problems though!

 

[Ady]

both me and ady have an hks actuator and both have boost dropping off problems though!

what boost are you running?

 

[dac69er]

0.75 lo and 1bar high. dont use high much as i need to get a manifold 1st

 

[starletgt-shady]

same problem guys i have a hks actuator aswell
was told that when i get a boost controller that it would hold boost not sure if thats true but will find out soon will be ordering a apexi avc soon

 

[Nwimie]

i think its just the ct9 running out of puff cos i get the same problem !!

 

[gayan_GT]

i got the same... and more