Mark,

For those of us not able to go to Florida could you post some pictures here? Do you have the model number for the Fluidyne? I have always been at odds with certain folks about the water to oil heat exchanger debate. I like the idea if properly designed. The other thing is that in cold weather the system will warm the oil! My thoughts have always been if Nascar could use these exchangers they should be good for us. (they operate at 100% for several hours) Excellent post Mark.
Bill Jepson (20B RV-10)


-----Original Message-----
From: Mark Steitle <msteitle@gmail.com >
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, 23 Oct 2007 6:00 am
Subject: [FlyRotary] Cooling Update - Lancair ES/20B

OK, I was going to wait to discuss this at the fly-in, but I was chastized for keeping this to myself, so here goes.

My 3-rotor Lancair ES has had excessive oil temps of 225 - 235*F (in climb) since first flight.  Opening the cowl exit area helped enough to get me in the air for more than a lap around the pattern, but I was climb-limited to about 500fpm.  I was anticipating better performance once the Texas summer heat subsided, but that just didn't happen this year (temps in the high 80's just last weekend).  So, I decided to try an oil/water heat exchanger.  I found a NASCAR Fluidyne unit on ebay and managed to "win" the bid.  It required that I do major surgery to the cooling system, including relocating some items on the firewall to make room for the new heat exchanger.  I finished it up Sunday afternoon and did a couple of ground runs and things looked promising (it didn't leak).  So, I decided to go for a short test flight. 

I set the  M/T constant speed prop to 2300 rpm, which will give me takeoff rpm in the mid to upper 6K range.  OAT was about 88*F.  I accelerated and where I would normally have to throttle back to keep temps under 230*F, the temps were in the 180* range.  So, I kept the power on, climbing like I have never climbed before (1400 fpm).  This is a 4-place, 2100# empty airplane.  I kept it WOT until I reached 2000 msl (1500agl) and then noticed that I forgot to retract the 10* flaps used for takeoff. So, I cruised around at 2500 - 3000 msl and water temp was 170 - 177*F, oil temps were 160 - 165*F.  Before this mod, my oil temps would normally be approx. 185 - 190*F in cruise.  Needless to say, I was very happy. 

The difference in my oil/water arrangement is that I tapped the water pump with a 1/2" line just before it enters the front side housing and I use this "cool" water to supply the water to the oil/water exchanger.  I return the heated water to the engine discharge leading to the radiator.  I felt this would still provide sufficient coolant flow through the engine as some guys are running the smaller 13B pump on their 3-rotor engines without a problem.  The 20B water pump impeller is 1/4" larger diameter.  From my initial flight, it seems that there is plenty of coolant flow to keep the engine cool.

It is really too early to tell for certain, but things look very promising.  I will try and take some pictures to bring with me to the Rotary Fly-In. 

Finally, to give credit where credit is due, I am told that Leon (from down under) has been using this design for years with great success.  I thank Leon for sharing his racer tricks with the group. 

Mark S.

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