Boost problems.........help

[spoed]

---

Just got my car after many weeks of waiting. Took it off the truck and drove it home.
It has a problem and wonder if it is a eazy fix.........
As I accelerate, even mildly, I hear a pst...pst... pst..., on and on.
The boost needle bounces slightly as well. Almost as if the it is releasing boost in little squirts to the atmosphere. This even happens at low boost of .1 or .2 bar
It also happens under hard acceleration .
I was looking forward to a ride tommorow and this is real depressing. Can anyone advise me what to look out for ?

[mr2turbo300]

Has it got a Blow off valve fitted, wonder if it has stuck partially open with standing. If so rev the engine (with the clam up) and see if you can hear air leaking out.
Rob.

[Gadgeroonie]

you need a stronger spring in your dump valve

when you apply full throttle the problem should dissapear

[Blu3R]

Check the vac hose to the BOV for splits, tears, and that its actually there at all.

[spoed]

thanks for the replies guys. I just got the car. Its a m400 and pretty standard apart from a bigger intercooler and a 1.1 roush map.
Thing is if there were a leak it would be a continuous leak wouldnt it ?. This is a release, stop, release ,stop and so forth with about one second intervals.
How or what would cause this ?

[spoed]

The correct way is to say it is a pulsing release of pressure. It happens all the time at any rpm and boost. Does that explain better?

[Silent1]

Sounds like a worn out or loose spring in a BOV/diverter valve somewhere meaning it's yo-yo-ing

[Blu3R]

spoed said:

The correct way is to say it is a pulsing release of pressure. It happens all the time at any rpm and boost. Does that explain better?

Even on full throttle like Gadge suggested?

[spoed]

Silent1 said:

Sounds like a worn out or loose spring in a BOV/diverter valve somewhere meaning it's yo-yo-ing

Its a standard m400, where do i find this bov/diverter ? Can I check the spring ?

[spoed]

Blu3R said:

spoed said:

The correct way is to say it is a pulsing release of pressure. It happens all the time at any rpm and boost. Does that explain better?

Even on full throttle like Gadge suggested?

Do you mean flooring it and seeing if it still does it? I did accelerate from 2000rpm to 6000 rpm fairly hard , and I feel it pulsing.

[spoed]

how does a stock m400 blow off.? I dont have a extra BOV so maybe the standard one is broken/
What does it look like and where do I find it ??

[andygtt]

the other M12's dont have a BoV as std, so not sure if the M400 does.

[spoed]

andygtt said:

the other M12's dont have a BoV as std, so not sure if the M400 does.

So how do they blow off? is there a valve of sorts ?

[Adrian W]

spoed said:

andygtt said:

the other M12's dont have a BoV as std, so not sure if the M400 does.

So how do they blow off? is there a valve of sorts ?

M400's do not have a dump valve as standard, check the pipe under the throttle body to see if it is hanging off

[Blu3R]

spoed said:

andygtt said:

the other M12's dont have a BoV as std, so not sure if the M400 does.

So how do they blow off? is there a valve of sorts ?

No there's no valve, the 2 turbos don't produce enough boost combined to cause a problem otherwise you'd have stalling and get the familiar rally car chatter.

I wonder if you have a failing actuator? On higher boost cars, when you use partial throttle (easily noticable on motorways) you can cause the turbo to spin up but not fully open the wastegate and you can at times, manage to hold the pressure so that the wastegate cracks open (causing the turbine to slow and pressure of the compressor to drop) which then closes due to loss of pressure. That then builds again until the wastegate cracks open and the cycle continues.

Possibly the same phenomenon when an actuator spring is weak and not able to hold the wastegate shut?

[mr2turbo300]

If you did want to 100% rule out whether it has a BOV or not (many who have fitted the bigger IC also add them), you are looking for something like this
http://www.forgemotorsport.co.uk/content.asp?inc=p...

Obviously some of this will be hidden in the turbo pipework, but should be fairly obvious.
Rob.

[mr2turbo300]

Might also be worth keeping an eye on the result of this thread.
http://www.nobleforums.com/showthread.php?p=61926#...
Rob.

[spoed]

mr2turbo300 said:

Might also be worth keeping an eye on the result of this thread.
http://www.nobleforums.com/showthread.php?p=61926#...
Rob.

Thats also my post, maybe someone in the USA had some insight.

[spoed]

Just drove it again. The car accelerates in increments as the boost poips off and takes again. Each time a bit more boost. At 5000rpm Im only at .6/.7 bar. At 7500 it gets to.9.
It seems boost takes forever to build.
All pipes seem in good order.
There is one thing , the car came from 6000feet to sea level, but I doubt this is a issue.
At any rpm , as you accelerate, the car boosts then releases then reboosts a bit higher and so forth.
Damn, this is frustrating, new car and already hassles. I guess someone will fiqure it out eventually

[Silent1]

Split boost pipe?
Dodgy wastegate?