Looking for insight/experience/suggestions….

 

I’m building an un-pressurized ES with a TSIO-550E.

 

I would like to put 8.5:1 pistons in it and run with 30-32”’ish MP.  Goal: Similar (350’ish) HP with cooler CHT’s and perhaps slightly better economy.

 

In this arrangement, I do not believe I need all the air the standard turbos are capable of delivering.

 

The standard turbos appear pretty “tight” with an A/R (area/radius) Ratio of 0.5 – which creates relatively high exhaust back pressure and otherwise robs economy when not WOT.

 

Since, I do not need bleed air for the cabin and am targeting lower max boost, I’m thinking I might replace the standard turbos for new turbos with a “looser” (higher) A/R ratio.  Perhaps around 1.0 or 2.0

 

I’d like to still maintain capability to deliver 32” to 25,000 ft.  Any suggestion on turbo sizing?

 

With the “looser” turbos, I might also be able to reduce and/or remove the sonic nozzles (which are theoretically an efficiency loss for an un-pressurized bird).  I’m looking for more information relative to turbo surging with higher A/R ratios (and the sonic nozzles plugged).

 

With reduced and/or removed sonic nozzles, I’ll also need an exhaust muff for heat.  While, I’m not a fan of exhaust muffs due to potential CO fumes, the capability for ground/descent heat in Michigan is a bonus (since bleed air is not hot when MP<29”).  Any suggestions on sources/designs for exhaust muffs for TSIO-550’s?

 

I have read lots of old archived messages here regarding related topics – but thought I’d open it up for a current discussion.

 

Rick Titsworth

rtitsworth@mindspring.com

313-506-5604

 

p.s. I saw a IV @ SNF with the sonic nozzles plugged (Jeff Hickman?).  It looked to have A/R=1.0 turbos, but was difficult to see with the lower cowl on.