losing manifold pressure at altitude

[Joes]

On the compressor side just remove the air filter and construct a plug made of high density foam with hole for a shop vac hose. The same for the exhaust side thru the exhaust pipe. Best to use a high pressure vacuum reversed. Joe

[GearUp]

Tracking down a very similar problem myself. One of the guys at Main Turbo suggested it's best to remove the spark plug from one cylinder, rotate the crank to open the valve on that cylinder, then use a compression tester to pressurize the cylinder and the intake or exhaust (whichever valve you opened). You'd also need to plug up the exhaust pipe at the end, or the intake at the air filter or inlet of the turbo. If you're looking at the intake side, you can also watch the MAP gauge.

I haven't done it yet, but love the high density foam plug suggestion. Thanks Joes.

[Dan schultz]

I had the same problem with the ball joints on my new exhaust from Acorn, had to send both back for re-work. I eliminated the springs and I am using titanium bolts and 12 point nuts was the only way that I could get them to seal to my satisfaction.
It does hold 75% power to 18k.

Dan
67S P337-0168

[Ed A]

Rear engine performance has never been as good as the front no matter how many times the turbo, wastegate and controller were overhauled. Cessna gave up on the exhaust with all the clamps after s/n 225.
I’m thinking about buying a brand new rear exhaust of the new design, made with slip joints, hoping it will solve the manifold pressure problems.
Has anyone already tried this?