Kelley Aerospace turbocharger relief valve vs. Merlyn Wastegate

[Schloff]

Can anyone tell me the differences between the  Kelley Aerospace turbocharger relief valve vs. the Merlyn Wastegate?  Are there advantages of one vs. the other?

[DonMuncy]

And are Kelly's STCed for Mooneys.

[Aerodon]

Don,

 

I'll give it a try:

 

1) The Merlyn waste gate replaces the fixed setting bypass on the TSIO360EB/FB/KB/LB series engines.  It is controlled by a pneumatic diaphragm with upper deck pressure on one side, can't remebr what is on the other.  It provides limited control (you can still over boost) but at least the small bypass is fully open at low altitudes and fully closed at higher altitudes.  I can get full power at 18,000 ft and 75% at 25,000 ft in my Seneca, or thereabouts.  The original factory setup was full power at about 11,000 ft and 75% at 18,000, probably 50% at 25,000.  Still have to what CHT's carefully at high altitudes.

2) The Kelly controller is hydraulic, controls a larger bypass, and in theory prevents over boost.  Much better controller, but a lot more money, not available as a retrofit, only on TSIO360MB/SB engines.  (252 type installation.

 

Aerodon

[DonMuncy]

Thanks

[N201MKTurbo]

The relief valve is there to protect the turbo. If you are at full power and suddenly close the throttle the pressure at the compressor outlet will go way beyond limits because of the inertia of the turbine/compressor wheel assembly. It takes some time for the turbo to slow down yet you can close the throttle almost instantly. This over pressure can damage the compressor wheel. The relief valve vents this over pressure.

On my turbo setup the relief valve also controls the upper deck pressure. This is not the case with the 231. The 231 is ground boosted and has a max MP of ??36 in. My setup is turbo normalized and has a max MP of 30 in. My relief valve opens at 32 in. I don't know the vent pressure of the 231.

BTW my setup seems to work very well.