Inconsistent boost

Phil Rose pjrose at
Mon Aug 7 07:37:58 EDT 2006

At 11:17 PM -0600 8/6/06, Greg Watts wrote:
>I have just recently encountered some boost problems. I have a 
>Hoppen stage 2 chip, RS turbo and EM. Overall the car is running 
>good, good steady idle, starts right up. 1st gear the car pulls 
>strong to redline. In 2nd, if I floor it I get no kick at all, it 
>will barely make 1.4 bar (as shown on the digital readout on the 
>dash). I can play with the accelerator, gradually accelerating and 
>can see it is trying to acheive some speed, I get some boost then it 
>flattens out, then it kicks in again, then flattens out. 3rd, 4th 
>and 5th are similar, although I have hit 1.7 bar, but it did it 
>without alot of enthusiasm. I pulled all of the turbo/intercooler 
>hoses and they are fine. Checked all of the vacuum hoses, replaced 
>most of them, still the same performance. Pulled and cleaned all of 
>the sensor, MAF etc plugs. I have been reading the SJM info and will 
>start checking voltage etc but wanted to see if anyone had any I 
>deas as troo what is causing this.

Considering the symptoms (and what you have done so far) I can think 
of a few things you may not have checked yet:

# turbo bypass valve and its associated vac hose. The valve can leak 
and of course its vac hose is a prime source of leakage, especially 
if it's still routed along the manifold intake pipe.

# wastegate frequency valve--failure limits boost to 1.4 bar; perhaps 
yours is intermittant. Have you done an output test, as described by 

# Pressure testing. When all the hose clamps have been tightened and 
boost is still poor, there may be a "hidden" problem in a hose that 
only will become apparent under pressure testing. Sometimes hoses can 
have splits that are hidden from view unless removed and carefully 
inspected (in my car this was the case for the short section of 
"hose" connecting the throttle body to the big intake tube. A 
pressure test ought to reveal (audibly) such cases.

*  Phil & Judy Rose           Rochester, NY  *      
*        mailto:pjrose at       *

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