Well,

I recently installed the Tail 38mm with a MBC. I can dial whatever boost I want, but above 5k rpms it will fall back to about 13#. Initially, the Tial had the small red spring (.4 bar) so I figured it was too weak. Switched to a 1 bar (big blue) spring and the problem remains the same. Good boost, but still rolls off just as before to about 13# above 5k rpms. Happens no matter what gear I am in, and no matter how much boost I dial in (14-18#).

Danno suggested instead of the MBC, switch the WG to single port mode and run my old LBE to it. Have not tried this yet but I can't see why this would solve the boost roll-off.

I am wondering if the following would cause this:

1)bad rings/compression
2)bad turbo (mine is a stock 140k 26/6 which spits some oil out the tailpipe on start-up)
3)vacuum leak somewhere

The persistent loss of higher rpm boost makes me wonder if the turbo is on its way out. Any ideas?

 

My guess, as I think I'm having the same problem, is that you have a leaking exhaust gasket, paticulary to one going to the wastegate.
It will hold good untill it reaches the high boost then poof....blowby and then reseals when you shift.
Maybe.......HTH

 

Small turbo.

Install a larger turbo or an electronic boost controller.

The engine is fine and the turbo probably is too.

The oil is most likely from the blow by oil that collects in the pipe the returns the blow by to the front of the turbo. When you shut off the car, the oil that has collected on the inside of the pipe collects and drains into the turbo leaving a tiny pool of oil that gets sucked in when you start the car.

(my guess w/o actually seeing the car)

TonyG

 

Yeah, man, it is the turbo. Don't let anyone worry you about leaking this or that. I was hitting 22 psi EASILY when I forgot to hook up the banjo bolt tp my intercooler pipe the other day. This was a Tial, also. Its time for the GT30, dude.

 

The first +70hp = $1000

The following +20 hp = $500

The next +20 hp after that = $1000

Where does it end?

 

It doesnt :>)
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yea, the k26/6 is just running out of steam on you.

 

it never ends, for if it did what would you do next?

 

Interesting update:

just talked to Tim at SFR. I may not be maintaining boost if my Greddy BOV is not set correctly. I will attempt an adjustment and see what happens. FOund the following nice description of how the BOV works with diagrams here:

http://www.935motorsports.com/greddybov.htm

 

Another nice BOV adjustment FAQ

http://www.stealth316.com/2-bov1.htm

 

My k26/6 could not hold more than 14 or so to redline, with an electronic controller. When I added the bigger turbo, I could hold higher boost to redline. Now, with the bigger tubo and a deltagate, I can hold whatever I want to redline. My guess is that you can tweak this or that to get maybe 14 or 15 to redline, but that you will need a bigger turbo to get more than that.