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Cavokev
13th January 2008, 21:29
Anyone got a thermostat fitted and passed as a mod on 912? I was thinking of the three way type. Kev A sent this and wondered if anyone's got one fitted.

Kev

Attached files cooling_9121.pdf (http://cloudniner.co.uk/images/converted_files/21578=1716-cooling_9121.pdf) (471.7 KB)

Kevin Armstrong
13th January 2008, 22:15
Pete Croney knows far more than most about the Internal Combustion engine (he used to run a Subaru Tuning workshop).

Sadly he advised that most of this article was utter crap, although the bits about the three-way thermostat was new and informative. Pete also advised that controlling the oil temp was useful, but the water temp wasn't worth bothering with. Pete actually got Chris Draper to add an Oil thermostat to his mod list for the 912 Raven, and reckons it knocks 30% off the warm - up time.

Further input from Roger Pattrick went further; he also advised that if I fitted an oil stat as Pete had, I'd STILL have to wait until the water temps rose to 100 before committing aviation - otherwise the water-fed carb heat wouldn't work properly, which risks carb icing.

So it wasn't worth me fitting either....

Still think that sliding muffs on water and oil rads are crude and would be considered out of date by the end of the 1930s on cars; the oil or water 'stat would at least bin the need for an oil cooler muff, and allow full exposure of the gills so that it could, at least, never overheat.

Kev

Andy_Fell
13th January 2008, 22:36
Kev wrote: full exposure of the gills so that it could, at least, never overheat.
Assuming the stat never gets stuck :freaked:

Cavokev
13th January 2008, 23:35
Nahh

Don't give a stuff about warm up time, its watching the temps drop below 80C in the descent, and waiting for the on set of a misfire just as you are 100' above trees, also when you've got something that can cruise from 45 to 85 mph but the only restriction is dependant on how much of your rad that's covered, it just seems crazy that its not a standard fit, unless i'm missing something.

Has anyone got a coolant thermostat fitted on a 912s in a flex?

Kev

Kevin Armstrong
14th January 2008, 22:13
Good point well made. If it wasn't such a scrotal-ache getting even the simplest mods through the Tech Office, I'd seriously consider doing this. Especially as the 912 gives you so much leeway, as in a claimed 20 minutes running even if it loses all water cooling.

Kev


Cavok-Kev wrote:

Nahh

Don't give a stuff about warm up time, its watching the temps drop below 80C in the descent, and waiting for the on set of a misfire just as you are 100' above trees, also when you've got something that can cruise from 45 to 85 mph but the only restriction is dependant on how much of your rad that's covered, it just seems crazy that its not a standard fit, unless i'm missing something.

Has anyone got a coolant thermostat fitted on a 912s in a flex?

Kev

bar shaker
15th January 2008, 09:35
Reggie Bender wrote:

Further input from Roger Pattrick went further; he also advised that if I fitted an oil stat as Pete had, I'd STILL have to wait until the water temps rose to 100 before committing aviation - otherwise the water-fed carb heat wouldn't work properly, which risks carb icing.


Kev I'm not sure why Roger would have said that because on most installations the water never gets to 100degC and it will certainly never get to it at anything less than full power.

The carb heaters are working very nicely once the water is at 60-70degC and at this time of year, my water is at 60degC when my oil is still only at 24degC... and that's with my oil stat accelerating the oil warm up times. At this time of year, my oil stat means I am at 50degC in less than 6 minutes from initial start up and the water is up to operating temps long before the oil.

The aim of the water is to keep the head as cool as possible and the fact that it is at 80-90degC in the cruise means we can use the waste heat to warm the carbs.

I cannot see any point in getting the water up to temp long before the oil is warm enough to use the engine at take off power.

Watch your temps during warm up, next time you fly and you will see that a water stat is not necessary.

Kevin Armstrong
15th January 2008, 09:58
Bar Shaker said

Watch your temps during warm up, next time you fly and you will see that a water stat is not necessary.

[/quote]
Agreed with all points Pete, your knowledge exceeds mine.

The issue is whether we do what Cavok-Kev originally proposed, ie give the trike radiator the ability to work properly if we sling the muffs. Whilst this might seem unecessary in winter, what the thread is about is the safety/peace of mind of knowing that you will never run out of cooling, say on a big trip over hostile territory in hot weather.

Fitting a water stat means that you will never be caught having set the muff nicely on the ground, only to find that the temps are going too high once airborne. It would stay mostly closed in all but the hottest conditions, but you could completely forget about it, as you do every day in your car. More modern in other words.

Kev

bar shaker
15th January 2008, 11:33
Kev

I think the comparison with cars is where the writer of the original document fell over.

912 engines only use water for cooling the heads and the cooler these are the better but a temp of 80-85degC is worked around for mixture purposes. Being carb'ed engines, our mixture is fixed.

The cylinder walls of a 912 are air cooled. In a descent, a certain amount of residual heat in the water will transfer from the heads and keep the top end of the cylinder walls up to temps but cooling will be to below optimum temps, thermostat fitted or not. That's why we should give an occasional prod of the throttle or leave 3000rpm on. During warm up, there is very little air flow through the cylinder wall vanes and the cylinder walls get to temp very quickly.

Car engines use water for cooling the whole engine and getting the cylinder walls up to temp quickly is more important to prevent cold seizure. The thermostat also allows the car's passenger heating system to be effective more quickly. Being a large lump of iron, the time to optimum temperature of a car engine is much longer than our small alloy engines.

Kevin Armstrong
15th January 2008, 12:57
Hello mate

This is all good stuff but still misses Cavok's point; he wants to dispense with 'muff control', so that the motor looks after itself from start up to shutdown. I must say he has a point, irrespective of whether the cylinders are air, water, alloy or pig-iron. We set the muffs to allow adequate airflow to cope with the hottest temp we might see in a typical flight profile; in a descent it could be a good thing for a 'stat. to reduce the cooling water flow so that the carbs see more heat, as the carb heaters are an effective short-circuit of the main flow.

Blades were prone to the odd stoppage in the circuit through icing - BJ will confirm.

Kev

Cavokev
16th January 2008, 16:28
Found a supply of these, opens at 80c and if it fails it fails open, not bad for £17 according to my local Quintin Hazell supplier. Now how hard is it to get passed? It'll fit nice and snug under the motor on me GT.

Kev

Attached files http://cloudniner.co.uk/images/converted_files/21787=1745-qth126k.jpg (http://cloudniner.co.uk/images/converted_files/21787=1745-qth126k.jpg)

Kevin Armstrong
16th January 2008, 16:59
Nice one Kev

Thing is, the only way to get such a mod through the current bods is to bung it on, get it thoroughly sorted via ground-running, then swap back to standard. Arm yourself with a tonne of piccies and data on performance of the 'stat, a P&M letter of no tech objection, then be prepared (if my experience is anything to go by) with a load of queries that betray the fact that the examiner has lots of qualifications and knowledge, not enough of which is about microlights....

Pete did the smart thing and asked Chris Draper to bung the oil stat on as a factory mod.

P&M are a bit reluctant lately, maybe because it costs them money

Good luck, you might also be wise to pick Nigel Beale's brains as he'll know someone with one fitted

Kev


Cavok-Kev wrote:

Found a supply of these, opens at 80c and if it fails it fails open, not bad for £17 according to my local Quintin Hazell supplier. Now how hard is it to get passed? It'll fit nice and snug under the motor on me GT.

Kev

crono33
18th January 2008, 15:12
a few folks i know have fitted the water/oil thermostatic valve and they love it. substantially shortens warming up times, and keeps fluids at constant temps, avoiding the use of those antiesthetic tapes on the rads :-)

i dont think there is a minimum coolant temp for the 912, however i would keep it between 80 to 110C, sort of

oil is all good after 50, and i think optimal should be around 80 to 100 to avoid too much h2o collecting in it

one thing i love of the rotax is that if properly installed, temps are not an issue at all. with air temps from -10 to +40 i have no problem whatsoever, and even long descents are not an issue.

hawk
19th January 2008, 11:45
Hi,
With reference to water temp thermstatic fitted to the 912S Air Creation have this fitted on they Tanarg and it works great. The oil temp comes up quicker as well the water, therefore saving fuel @£1.10 per liter.

Derek

bar shaker
19th January 2008, 20:01
Considering that the water only cools the heads, can someone explain to me how the water temp can 'substantially' accelerate the oil warm up time?

Kevin Armstrong
21st January 2008, 02:55
Maybe because the heads are partly cooled by oil; speed up the march of the head temps. to 100C and you'll speed up the rise in oil temp to 50C too; instead of bouncing it around on here, might be best to get some info from Tanarg owners on comparitive warm-up times? Be interesting to know their experiences.

Kev

crono33
21st January 2008, 11:29
i think there are different types of thermostats

AFAIK there is water, oil, and water/oil types.

oil thermostat
http://www.rotaxservice.com/rotax_engines/rotax_912UL.htm

oil and water thermostats (separate)
http://www.franz-aircraft.de/Rotax/sonderzuebehoer.htm

bithermostat for oil and water

http://www.ulm.it/com/machme/

bar shaker
21st January 2008, 12:22
Kev

The oil flow through the heads is negligible and far too small to be a major influence on overall oil temp, especially compared to the amount that is spraying around in the crankcase.

It is pumped up through the push rod, through the rocker bearing, allowed to spray and then runs down the tube around the push rod, back to the main sump. Whilst the oil is against the outer side of the water jacket when spraying around, it is also against the inside of the rocker cover plate (which will be close to OAT) and then runs down the oil return pipes which are isolated from the cylinders and will also be closer to OAT.

I suspect it comes from the back from the heads cooler than it goes in but I will put a probe on the pushrod oil return pipes, when it is safe to cross the swamp that is my airfield.

Kevin Armstrong
21st January 2008, 12:34
You've got a probe? Nice one my techie friend.

Pity this hasn't come under Paul Dewhurst's nose yet; he might have advised why Air Création think a water 'stat is a good idea.

Cheers

Kev

Cavokev
21st January 2008, 18:51
http://www.franz-aircraft.de/Rotax/thermostat180.htm are the dog’s I think, trying to understand German isn’t a strong point of mine, nice kit they supply as well. Thanks Giamarco.



I’ve tried to speak to Paul today but away today, but I did contact Skydrive and they’ve been working on a coolant stat, but they’re still working out the pros and cons, like how many thermostat kits would they need to sell to cover the cost of an engine if one of the kits causes a failure.



So if they are fitted to 912s Tanarg’s, should be ok to fit one to my lump eh?



Kev

bar shaker
22nd January 2008, 08:29
Kev

If you are serious about doing this, perhaps you could log your warm up times from various starting temps to 50degC at a constant 2500 rpm, so we can see if it makes a difference. Please log oil and water temps at 1 minute intervals, before and after fitting.

My oil stat gets my oil to 50degC in 6 minutes from 5degC. Before I fitted it, warm up from 5degC at 2500rpm was almost 11 minutes. I wish I had logged the 1 minute interval times too, but I am very pleased with what the oil stat does.

I would be interested in accurately documented times for a water stat, even though I remain very sceptical as to their benefit.

Cavokev
22nd January 2008, 14:00
Pete
I'll do that, but as I said before, I'm not bothered about the warm up time, its in the descent the coolant temps drop to 70c and lower thus the on set of carb ice is increased.

warm up times to 50c oil has been 12min with OAT 3c and 9min with OAT 15c, if i do get somthing fitted to the coolant side I'll do a before and after ,but I don't think it'll improve oil warm up times.

Kev