losing manifold pressure at altitude - Page 2

Joes · #16 07-10-23, 10:24 PM

Was this issue ever resolved????? I currently have something similar going on. Any help would be appreciated.

B2C2 · #17 07-11-23, 11:23 AM

None of these replies mentions examining the air induction path to the engine. If there is blockage there the air delivery will be at reduced pressure to the turbo. If this is large enough it will prevent the turbo from developing full inlet pressure. A clogged inlet path or airfilter could cause this. During the bad fire seasons we had on the west coast the air filter on my turbo was clogged significantly with smoke particles. I did not see a turbo pressure issue but didn't take it to high altitude much either.

As a side note I had a problem where I could not get to full inlet pressure on my front engine a few years ago. It turned out the magnet that holds the emergency air inlet closed had fallen off and damaged the impeller on the compressor side. For the posts where the turbo was replaced this obviously isn't the issue but if its a new observation make sure to get a look at the impeller to make sure its not damaged.

Joes · #18 07-12-23, 06:49 AM

Found the leak! After pressurizing the compresor and the exhaust system I found a massive leak at the collector/ball assembly. Also just a few minor leaks on the injector o-rings. Thanks for all the input from the past and present. Joe

mshac · #19 07-12-23, 09:52 AM

Would you mind posting a photo of the exact location of the leak? As close-up as possible? TY!

Joes · #20 07-12-23, 10:46 AM

Here ya go

Dr.Dan · #21 07-12-23, 11:05 AM

Quote:

Originally Posted by Joes

Found the leak! After pressurizing the compresor and the exhaust system I found a massive leak at the collector/ball assembly. Also just a few minor leaks on the injector o-rings. Thanks for all the input from the past and present. Joe

How did you pressurize the system?

Cheers,
DD

mshac · #22 07-12-23, 11:10 AM

Quote:

Originally Posted by Joes

Here ya go

Great pictures!!!

Joes · #23 07-12-23, 06:22 PM

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 · #24 07-12-23, 06:34 PM

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 · #25 07-19-23, 09:44 PM

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 · #26 03-15-25, 02:41 PM

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?