Help! Why does the turbo cut out of boost only in high ge..

So my brother has a 3.0 liter Volkswagon VR6. Dynos at about 340 whp.
1/4 et is 13.6 with a trap of 111 mph. Fast as shit and scary.


The motor is totally built and there really isnt anything left that
needs to be upgraded. The turbo is a Turbonetics TS04. The wastgate
is a factory Audi piece. The blowoff valve is a Greddy Type R. The
electronic boost controller is a HKS. We are running at about 17 psi.

However we have a major problem.

First, second and third gear the car pulls like a mother,

BUT.....

The moment you shift into 4rth or 5th gear the boost starts to majorly
waffle. It cuts and jumps from full 17 to 10 and back again and back
again and back again and back again. It never stops. You can get to
110 mph real easy but it then takes forever for the mph to climb as
the boost keeps cutting out.

It NEVER does this in 1st, 2nd or 3rd gear. If you are driving along
at 80 mph in 4rth or 5th, drop to 3rd and floor it, the boost jumps up
to 17 and stays there until you have to shift up. The moment you
shift into 4th, the boost starts waffling from 17 to 10 and back and
forth.

If you are at crusing at 80 in 4rth or 5th and floor it, the boost
climbs up to 17 and the moment it hits 17 just starts the waffleing
again.

Any clues or ideas?

I just found out about this problem this weekend. My brother is an
idiot and neglected to mention he has been living with this problem
for over a year.

Thanks!

Don't know the specifics of your turbo control system, but I wonder if the
car is having a detonation problem and the control is trying to correct by
reducing the boost pressure, stops detonating and increase the boost
pressure again until it sense detonation again. Detonation is mostly
present when motor is under the most load, such as higher gears. Many cars
on pump gas can have as much as 21 psi in 1st gear and pressure is reduced
to maybe 17 or so in the higher gears.

What would happen if he reduced the boost to about 10 psi? If all is okay,
increase the boost pressure a little at a time until the problem returns.
Maybe he needs to run a higher octane fuel or there is not enough fuel under
heavy load or the spark plug wires/plugs or injectors could be a problem.
There is such a thing as a detonation sensor that can be installed inside
the car.

Could be off base with the detonation theory but it would be a good place to
start. o




"Douglas Vincent" <dgvffd.DeleteThis@teleport.com> wrote in message
news:188971ad.0406061741.3330cfe@posting.google.com...
 > So my brother has a 3.0 liter Volkswagon VR6. Dynos at about 340 whp.
 > 1/4 et is 13.6 with a trap of 111 mph. Fast as shit and scary.
 >
 >
 > The motor is totally built and there really isnt anything left that
 > needs to be upgraded. The turbo is a Turbonetics TS04. The wastgate
 > is a factory Audi piece. The blowoff valve is a Greddy Type R. The
 > electronic boost controller is a HKS. We are running at about 17 psi.
 >
 > However we have a major problem.
 >
 > First, second and third gear the car pulls like a mother,
 >
 > BUT.....
 >
 > The moment you shift into 4rth or 5th gear the boost starts to majorly
 > waffle. It cuts and jumps from full 17 to 10 and back again and back
 > again and back again and back again. It never stops. You can get to
 > 110 mph real easy but it then takes forever for the mph to climb as
 > the boost keeps cutting out.
 >
 > It NEVER does this in 1st, 2nd or 3rd gear. If you are driving along
 > at 80 mph in 4rth or 5th, drop to 3rd and floor it, the boost jumps up
 > to 17 and stays there until you have to shift up. The moment you
 > shift into 4th, the boost starts waffling from 17 to 10 and back and
 > forth.
 >
 > If you are at crusing at 80 in 4rth or 5th and floor it, the boost
 > climbs up to 17 and the moment it hits 17 just starts the waffleing
 > again.
 >
 > Any clues or ideas?
 >
 > I just found out about this problem this weekend. My brother is an
 > idiot and neglected to mention he has been living with this problem
 > for over a year.
 >
 > Thanks!<!-- ~MESSAGE_AFTER~ -->