turbo output at altitude

[Bryan Devault]

I test flew my Turbo twin comanche last night after a lot of work to get the turbo boost higher, which included replacing the wastegates, sealing the alternate air boxes and air filters, and replacing the left cable, and the right turbo now makes 25" of boost at 2700 rpm at 17500' (20000' density altitude on a hot Houston summer day). Pulling back the prop to 2500 rpm gives only about 23" of boost. Is this about all I can expect with everything working, or should I keep looking or air leaks? The right turbo was rebuilt right before I bought the aircraft in May, so I don't think that's the issue.

The new cable on the left engine doesn't seem strong enough to close the wastegate, since there's about a 2-3" boost differential between the left and right engines and the cable feels sticky and tentative. Does anyone have any ideas? We had no luck finding replacement for the original cable so the new one was fabricated for us.

[Jay]

23" of MP at 2500 RPM is about as good as I've ever been able to do at a DA of 20,000!

Could it be that your left wastegate is hanging up a bit? Perhaps as the metal gets hot and expands the fit is too tight. There is an article in the Tips Special about lapping the wastegates so that they close smoothly. That's just a thought, certainly not definitive!

Best,

Jay

[CLIPCLIP]

[Tony Scarpelli]

I have two new Turbos and 2 year old waste gates, rebuilt air box induction system and the highest I am able to get is 28.8" at 14k'

So that would be about 22.8" at 20k'

I have not had it above 14k and it may not be linear.

I am still looking for anything that can give me more boost as I have talked to someone with a 260TC and he says that he can get 29" at 20,000' without fully engaging the wastegates. So he has boost to go.

He has 200 hrs on a fwf oh.

[Bryan Devault]

[T210DRVR]

[Zach Grant L1011jock]

[KJB]

[Zach Grant L1011jock]