Wastegate

[meritflyer]

There is a very distinct crowd that believes wastegates on turbo charged engines are a must. Conversely, there's a very distinct crowd that believes wastegates on turbo charged engines are a complete sham.

Who to believe...

[trafficinsight]

Every turbocharged engine has a wastegate... some are automatic, some are adjustable, and some are fixed.

[patthepilot]

Yup, the whole purpose of the wastegate is to determine how much of the exhaust gas gets put into the hot side of the turbo. At high altitudes, the wastegate is totally closed and low it's somewhat open. If a plane doesn't have a wastegate, it might add some to the service ceiling, but nothing like FL320 and still not finding the top.

Why the question?

[shdw]

Correct me if I am wrong, but without a waste gate the engine is basically the same as a jet?

Can it operate without a waste gate though, wouldn't it overheat the turbo at lower altitudes?

[Mike H]

I believe the purpose of a wastegate is to prevent the turbocharger from overboosting the engine at lower altitudes-

[roundout]

There are turbos without wastegates, but I've never heard of one on an airplane engine. Modern diesel engines have them (VNT turbos). Airplane engines have 1930s technology wastegates to go with the 1930s technology engines. Modern installations have automatic wastegates.

[trafficinsight]

Originally Posted by roundout

There are turbos without wastegates, but I've never heard of one on an airplane engine. Modern diesel engines have them (VNT turbos). Airplane engines have 1930s technology wastegates to go with the 1930s technology engines. Modern installations have automatic wastegates.

Different method, same idea

[esa17]

It's not that they don't have them, some are just more sophisticated.

An automatic one does exactly the same thing as a manual wastegate but adds a great deal of expense you will never get back out of the plane. Sure, it looks cool on paper but it's just one more expensive part to fix when it breaks.

[DPApilot]

Originally Posted by Mike H

I believe the purpose of a wastegate is to prevent the turbocharger from overboosting the engine at lower altitudes-

Yes, and on the 320, if you advance the throttle too fast, it overboosts, fast!

[trafficinsight]

Originally Posted by Mike H

I believe the purpose of a wastegate is to prevent the turbocharger from overboosting the engine at lower altitudes-

Sort of... the purpose of a wastegate is to control the exhaust flow through the turbocharger, that's all that's it.

So, a fixed wastegate always sends a certain portion through the turbo. With a fixed wastegate you have to watch the manifold pressure and stop adding power when it hits redline. The Seneca 2 and, I think, the Turbo Arrow have a fixed wastegate.

A manual wastegate is adjusted with another lever or knob to give you the desired manifold pressure.

And an automatic wastegate adjusts automatically using engine oil... however, you have to watch it closely because it doesn't always work reliably.


The Turbo 182 has a wastegate that is actuated by the throttle knob, more throttle = more boost... but IIRC it's supposed to be adjusted so that full throttle = redline boost... it's been a long time since I've worked on one though.

[Roger, Roger]

Originally Posted by trafficinsight

And an automatic wastegate adjusts automatically using engine oil... however, you have to watch it closely because it doesn't always work reliably.


The Turbo 182 has a wastegate that is actuated by the throttle knob, more throttle = more boost... but IIRC it's supposed to be adjusted so that full throttle = redline boost... it's been a long time since I've worked on one though.

Most aircraft turbos are that way. I haven't flown enough of them to know if they're typically adjusted right.

[trafficinsight]

Originally Posted by Roger, Roger

Most aircraft turbos are that way. I haven't flown enough of them to know if they're typically adjusted right.

Most are actually the oil actuated type... the 182 is a mechanical linkage which, by the way, should be lubed at inspections

If you ever get a turbo 182 and they're complaining about low boost or hard throttle movement, lube the wastegate linkage!

[Roger, Roger]

Originally Posted by trafficinsight

Most are actually the oil actuated type... the 182 is a mechanical linkage which, by the way, should be lubed at inspections

If you ever get a turbo 182 and they're complaining about low boost or hard throttle movement, lube the wastegate linkage!

Yeah...I know they're mostly oil actuated...that was quotation usage fail. We had a Turbo Arrow with the fixed wastegate in the shop a little while ago. Interesting bird for sure.

[Baronman]

Originally Posted by trafficinsight

So, a fixed wastegate always sends a certain portion through the turbo. With a fixed wastegate you have to watch the manifold pressure and stop adding power when it hits redline. The Seneca 2 and, I think, the Turbo Arrow have a fixed wastegate.

Seneca 3 as well has a fixed waste gate. If I remember it was calibrated so that when the throttle was wide open, you'd get max MP at about 14,000' MSL. At sea level you got max MP 42'' (roughly) with the throttle about 2/3 open.

Sorry but no mashing the throttles forward...