Rotax 912 oil cooler

[Mike Davis]

Hi Ian,

Didn't you know... we changed over way back in 1977! I remember because I was in junior high at the time and everybody was required to learn metrics because of the change.

Mike

----- Original Message -----
From: Ian Donaldson (allsure@iprimus.com.au)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Friday, October 04, 2002 3:59 AM
Subject: Re: Rotax 912 oil cooler


G'day Chuck

Now that's a really nice program.

I have found that 240F = 115C!

Just when are the Americas going to change to metrics?


Regards


Ian

----- Original Message -----
From: Charles Bailey (baileyca2@hotmail.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Friday, October 04, 2002 1:30 AM
Subject: Re: Rotax 912 oil cooler



Lan,
I use a program called Convert that will convert almost everthing I need. Freeware from:
http://www.joshmadison.com/software/convert/



Chuck Bailey

Rebel 176
N225PC

From: "Ian Donaldson"
Reply-To:
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Subject: Re: Rotax 912 oil cooler
Date: Thu, 3 Oct 2002 21:56:39 +1000

G'day again Bruce

I have learned that there is a larger size cooler available and I will investigate that.

Unfortunately here in Australia we are thoroughly metricated and I have forgotten how to convert Fahrenheit to Celsius and I don't know just how hot 220F is !
: Re: Rotax 912 oil cooler


Ian,

My 912S on a 100F summer day in climb out may hit oil temps 220F. Normally I can't get it hot enough to burn off the condensation. I left it 1/3 taped off all summer. The cooler came stock with Skystar fire wall forward package. It's an Earl cooler with dimensions about 3" high and 9" long. It sets right up front in the inlet so it gets lots of cooling air. I would examine the amount of air getting to your cooler. Good luck.

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[Ian Donaldson]

G'day


Some success!

Before flying yesterday, I took to the bottom of the cowling with a hacksaw and cut the moulded lip completely off. I even trimmed the cowling back far enough to allow me to take it off without removing the exhaust extensions.

There was a immediate marked reduction in oil temperatures. On a long hard climb it went to 115c (240f) and on cruise it seemed to settle on about 100c (212f) (I know how to do the conversions now as Chuck Bailey told me of a neat program!)
The water temp is about 40c (100f)

So I guess that part of the problem was that air was being trapped in the cowl. After comparing the cowl on the Rebel with other 912 aircraft here, it seems that the Rebel cowl is more than generous with the inlet sizes. Is there any general rule of thumb that I could use to work out the ratio of inlet vs outlet dimensions. I have not seen a cowl for a Locoing but the inlets appear similar sizes.
Could the inlets be too big?

Regards


Ian Donaldson







The oil cooler is about 40 square inches which is about the same as those used on other 912s engines in this area

[Mike Kimball]

I had chronic high temp problems on my Renegade Spirit while I was in Australia. There was baffling presumably to duct air to the oil cooler and around the cylinders that partially blocked the cowl opening behind the prop. I removed all the baffling and just had the engine wide open inside the cowl. Dropped oil temps by 40 deg F. Exactly the opposite thing you should do with a Lycoming, but it sure worked for the 912.

Mike Kimball
SR#044

-----Original Message-----
From: murphy-rebel@dcsol.com [mailto:murphy-rebel@dcsol.com]On Behalf Of Bill Delcambre
Sent: Wednesday, October 02, 2002 6:52 AM
To: murphy-rebel@dcsol.com
Subject: Re: Rotax 912 oil cooler


Hi, Ian!

My $.02;

I'm building a Super Rebel now, but flew a Kitfox IV for several years, with an 80 horse 912. My cooler was about 3" x 10", as I recall. I had the same problems at first. You didn't mention head temps, but I'm gonna assume they're a bit high, too. I'm gonna assume that airflow through the cooler is not the issue. Seems that everyone that I ever spoke with, who was flying a 912 (any version) had comments about temps. Some never warmed up enough and some, like you and I, were too hot. The first thing is to be absolutely sure that you've got no restrictions in your lines to and from the cooler. At first, I believed the owners manual about putting PURE antifreeze in the cooling system. I suspect that the European specs are different from our American ones. With Pure antifreeze, the thing would run about as you're describing. Water temps were around 250 F and the oil would darned near peg the gauge! Switching to 50% water, balance antifreeze brought water down to about 200 F. I had a temp sender in the head and one in the radiator. Radiator was always about 20 F cooler than the head temp. Whenever I felt that the head temps were running too high, I'd just start looking at the other gauge. (humor...) Oil was still a bit high until I switched to Mobil 1 synthetic oil. I seem to recall using 20w50 Mobil 1. My oil temps would run about 240 F, after that. This seems to be an ideal temperature for moisture boil off, and the engine was happy. I understand that the synthetics are good beyond 300 F, although I would fear for the engine at those temps. When I sold the Kitfox, it had about 430 hours and ran like an electric motor. Smooth and strong.
The Rotax is a fabulous engine, in my book. You'll get it sorted out, and enjoy flying behind it for years!

Bill Delcambre
SR172FB

----- Original Message -----
From: Ian Donaldson (allsure@iprimus.com.au)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Wednesday, October 02, 2002 8:55 AM
Subject: Rotax 912 oil cooler


G'day

My Rebel is fitted with the Rotax 912s 100hp engine, and I have a problem with high oil temperatures.
On a warmish day, (perhaps 25oC), when climbing hard the temperature climbs to 130oC and would go much higher if I continued.
I fear that I will cook the engine on a hot day!

The cooler that I am using is the standard one supplied by MAM, but I suspect that it is designed for the
80 hp engine.

I guess my question are;
Is if there is anyone out there using a 100hp engine?
If so what temps are you getting?
What size oil cooler are you using?
I would appreciate some dimensions on the size of the oil cooler to see if there is a difference.\


Thanks and regards

Ian Donaldson

(flying and loving it!)

[Ian Donaldson]

G'day Mike

Thanks for your response.

Cutting a larger cowl exit has made a difference.
However we have not had any hot weather yet so who knows what will happen then!

I will keep experimenting!

Regards


Ian Donaldson

I had chronic high temp problems on my Renegade Spirit while I was in Australia. There was baffling presumably to duct air to the oil cooler and around the cylinders that partially blocked the cowl opening behind the prop. I removed all the baffling and just had the engine wide open inside the cowl. Dropped oil temps by 40 deg F. Exactly the opposite thing you should do with a Lycoming, but it sure worked for the 912.

Mike Kimball
SR#044

[Legeorgen]

Ian,
Tony Bingales book "Firewall Forward" gives a rule of thumb for exit air to be 1.5 times the inlet air.

Bruce 357R

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[Ian Donaldson]

G'day Bruce


Thanks for the info.

I have Tony Bingales book "Sportplane construction" but did not know about "Firewall forward"


Regards

Ian Donaldson

Ian,
Tony Bingales book "Firewall Forward" gives a rule of thumb for exit air to be 1.5 times the inlet air.

Bruce 357R

[Rebflyer]

Hi Ian, the Tony Bengallis rule of thumb was an opening 1.5 bigger than the inlet. Thats where I started on my 0-320 powered Rebel. After opening the cowl more the best one shot result was when I cleaned up the firewall exit area. The test was with duct tape taped to the bottom of the fusealage to up about 2" on the firewall, over the firewall lip. Different engine, but the air still has to get out as smoothly as possible. Good luck, isn't flying great? Curt N97MR

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[Drew Dalgleish]

Hi Ian
FRom tony bingellis on engines your inlets should be .35xhp. So 100hp.
needs 35square inches of inlet total.Thats a 3"x6" opening on each side.
Drew Dalgleish

At 01:21 PM 10/7/2002 +1000, you wrote:

G'day Some success! Before flying yesterday, I took to the bottom
of the cowling with a hacksaw and cut the moulded lip completely off. I
even trimmed the cowling back far enough to allow me to take it off
without removing the exhaust extensions. in oil temperatures. On a
long hard climb it went to 115c (240f) and on cruise it seemed to settle
on about a neat program!) The water temp is about 40c (100f) So I
guess that part of the problem was that air was being trapped in the cowl.
After comparing the cowl on the Rebel with other 912 aircraft here, it
seems that the Rebel cowl is more than generous with the inlet sizes. Is
there any general rule of thumb that I could use to work out the ratio of
inlet vs outlet dimensions. I have not seen a cowl for a Locoing but the
inlets appear similar sizes. Could the inlets be too big? Regards Ian
Donaldson The oil cooler is about 40 square inches which is
about the same as those used on other 912s engines in this area

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