flyrotary@lancaironline.net Mailing List Archive

The rotary is a sandwich of layers - end housing, rotor housing, center housing, rotor housing, end housing. Not only are these dissimilar shapes, they are also dissimilar metals and they have different thermal loads and cooling passages. The center housing for instance, has the least room of all the housings for coolant, yet has the greatest surface area exposed to combustion. (Lucky iron has half the coefficient of thermal expansion compared to aluminum, or maybe Mazda did that on purpose). On top of that, the combustion and exhaust half of the cycle put a lot more heat into the engine than the compression, and the intake actually cools it. When the engine heats up (or cools off) all these parts heat and expand at different rates. The water seals are sandwiched between these layers and somehow have to deal with this. The hotter the engine gets, the greater the effect. Those thin, fragile water seals get twisted and stretched, the damage is cumulative, and you can't see it until suddenly you need an engine rebuild.

235 is too hot. If your coolant temp got to 235, consider yourself fortunate you don't have to rebuild. A good temperature is 180-200, over 200 is pushing it. You can run a little hotter in a plane because it's a gentle, constant heat, not the abrupt sort of heat changes that kill car motors. But not 40 degrees hotter.

I think rotary-engine plane builders are going through a lot of the same stuff the car tuners went through a decade or two ago. There are going to be a lot of guys with blown water seals in a couple years, if everyone is flying around with temps 210+ all the time.

On Fri, Jun 12, 2009 at 7:09 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:

Point taken, Lynn.

I guess I was impressed John could run it for 55 minutes and only get 235F. If I run mine for over 2-3 minutes at WOT my temps would already be climbing over 200F. While not necessarily recommending it for others, my red line for oil is 200F (into block) and 220F coolant (out of block). I normally do not stay at these temps beyond 2-3 minutes during take off and initial climbout.

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lynn Hanover
Sent: Friday, June 12, 2009 9:14 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Water temps

Allow me to speculate:

I suggest that watertemps above 210 are out of bounds. Thus it should be looked at as something you got away with, not a number to look for in normal operation. I would retorque the stack cold if I had seen those numbers. (235)

Here is some dyno stuff for a 12A bridgeported engine with two 36MM chokes in a Weber carb.

6500 RPM (because there is no point in testing a racing engine below that), and even then it is to put up a starting point for a curve.

Torque 139.6 foot pounds.

HP 173.3

EGTs 1515 front 1491 rear

BSFC .666 (the devils own)

oil temp 162 (160 is ideal) Above 160 costs power due to rotor face temperatures.

Oil pressure 99.9 (relief set at 110 pounds)

Water temp is always 180 controlled by the cooling system on the dyno.

Air/fuel 12.3 (slightly rich is fine as it helps cooling and sealing)

I would expect to get as much as 10% more power from a 13B.

Lynn E. Hanover

Interesting questions: Is that data at full throttle?

You can hold cruise RPM at an A/F of 15?

Today I ran the engine .9 hour, .7th's static at 4700 rpm - 13B, Marcotte 2 - l redrive

Water temp         235               OAT 61            Spring hasn't arrived above the 44th parallel

oil temp              215                                        yet

Exh. temp         1500

Prop speed        2350

MP                      28

oil pres                75

air - fuel         15 to 1

fuel press             42

.2 hr high speed taxi

Water temp         188

oil temp               160

Ex temp             1400

Prop speed         2500

MP                        28

fuel press               42

The static engine run temperatures climbed quite a bit with the cowling on and working on the programming I didn't notice that this was happening, but they went right down when I idled back.

I will have to pull the cowling in the morning and check the redrive, it appears the seal is leaking on the flywheel side. With no support from Marcotte, I may have too much 80w in the gearbox. I believe that the temperatures look good for flight. JohnD