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Bob;
I understand your position, please understand mine;
I don't want anything near 'maximum boost'. I'm willing to limit the turbochargers ability to make boost, by installing a turbine housing that is open enough to be in a perpetual bypass mode. I'm looking for a very modest increase in power, so I do not want a highly stressed turbine. I don't have an instrument rating, so I won't be flying much above 18,000 ft. Van designed the RV-8 airframe for 200 HP, and Tracy rated my gearbox at 200 HP as well. I am working toward a ballanced aircraft where all the systems meet the same performance point, which is flight in the 120 to 222 MPH range. I fly in Washington, with regular flights over the Cascade mountain range, and over water to the San Juan Islands. I seek good short field performance, and a substantial climb rate. After that I seek a strong cruise for 1 to 2 hours in the 7,000 to 12,000 ft zone followed by rapid decent without regard to shock cooling.
I'm not sure about this following point, but I am hoping to be able to lean out at cruise with open throttle to control turbo boost. It depends on many ballanced factors, but turbos are controlled by heat input. A bypass literally bypasses a portion of the engine exhaust heat around the turbine. The rotary engine's ability to run lean of peak has a potential application here.
Finally, I do have a plan for a waste gate if it turns out I need one. I'm just not willing to add stuff to my plane until I have a demonstrated need for it. If that occurs, I'll post my findings and you will be vindicated.
-----Original Message-----
From: Rogers, Bob J. <BRogers@FDIC.gov>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, Sep 8, 2009 9:14 am
Subject: [FlyRotary] Re: Regarding Scott Emery's turbo manifold
I recommend that you get the book Maximum Boost by Corky Bell if you want to know all about turbochargers, including wastegates.
You really need a wastegate and it is external to the TO4. The wastegate should be mounted in the exhaust manifold before the flow gets to the turbo. It controls the exhaust pressure and, when necessary, allows exhaust to bypass the turbo to control the amount of boost. The pop-off valve is on the intake side and serves primarily to protect from over pressuring the system when you rapidly close the throttle. This should not happen in an airplane, but it does not hurt to have one (other than extra cost and slight extra weight).
Bob
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Chris Barber
Sent: Sunday, September 06, 2009 8:06 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Regarding Scott Emery's turbo manifold
It looks great. It is continuing my motivation to pursue the turbo. I also have the Conversions Concepts mount. I too will likely have to fabricate - read that as have fabricated since, contrary to my manly man status :-), I know not how to weld :-( - my turbo manifold. I like how clean and simple yours is.
I am trying to decide the best position for it. The current extension that I have on my engine - in order to clear the Mistral Injectors location puts my aftermarket turbo manifold perilously close to my aileron control linkage (about 3/4 of an inch, or so). Also, it is right up on the top of the cowling.
My question to you is, I did not notice a waste gate mounting place on your turbo exhaust manifold. Both my aftermarket manifolds have a place to mount a waste gate. Did I miss it, is the wastage internal to the turbo? which I think is how Mazda did it, but figured this was not the case with the larger T04's we seem to be using). Where might I add one to a manifold I would have made. Would the position be secondary to just putting it in the place with most clearance?
While I have learned a great deal about how turbo's work, I am far from versed enough yet. Is there a conventional wisdom as to when to use a waste gate. I thought they were standard and the primary means to control boost, along with a pop off valve (if that is the correct term and idea?)
Advice and insight is sought and appreciated.
Thanks in advance guys and gals.
Cpl. Christopher Barber, JD
Bellaire Police Department
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