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Richard Lamprey
Joined: 15 Jul 2011
Posts: 95
Location: Kenya
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 Posted: Sun Jun 16, 2013 4:40 am Post subject: 912UL operating temperature |
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Greetings to all from Kenya.
Does anyone know what is the minimum cylinder head (coolant) temperature for normal operations? The manual gives maximum but no minimum, save for warming up to above 50C for takeoff power. I was told recently that cylinder head temp should not be too much below Oil temp, but not sure about this.
Some years ago I had new radiators made by Docking Engineering of Silverstone, after a leak in the Europa ones. They have proved so efficient that I cannot get the temp much above 105C after prolonged climb, and it settles to 80-90C in the cruise, against an oil temp of 105C. I put blanking strips on them to get the temp a bit higher, to 95C, but took these off to test recently, and down the temp went. The plugs are fouling up with carbon more now (with the odd missed beat), which according to the manual is caused by running too cool. But I cant find that optimum operating temperature stated anywhere. Any ideas appreciated.
A very simple Europa... 912UL, warp-drive fixed pitch.
Best
Richard
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graeme bird
Joined: 15 Jul 2010
Posts: 434
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| Posted: Sun Jun 16, 2013 9:38 am Post subject: Re: 912UL operating temperature |
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Kevin Dilks told me recently that running low was not an issue and a misnomer, not really affecting efficiency or engine wear.
I have been blanking off my radiator, but now find its getting too hot if I have to taxi for a while and long climb (probably not helped by the tundra tyre rubbing slightly).
I measure cylinder head and oil and the cylinder is always hotter.
Regards
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_________________
Graeme Bird
kit4 (Wagstaff) TBD
Kit3 G-CLXU (Gregory) mono 914 xs Woodcomp
Kit2 G-PATS - (kesterton) Mono Classic 912 warpdrive
Kit 1 G-UMPY - Mono Classic/XS 912S, Woodcomp G(@)gdbmk.co.uk |
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nigel_graham(at)m-tecque.
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| Posted: Sun Jun 16, 2013 11:53 am Post subject: 912UL operating temperature |
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Richard,
The only possible problem a seriously cool running engine could create would be water condensation in the oil. This manifests itself as a white emulsified scum deposited on the insides of the rocker-boxes and in the oil tank. Left un-corrected, this could cause bearing and piston wear. I would not think this would cause a modern plug to whisker.
The wrong heat-range plug could in extremis. They should all look whitish to light brown. Check that you are using the correct plugs and if “yes”, then I suspect that your problem is related to carburetion.
A rich mixture will cause the engine to run cool and the plugs to soot up and misfire occasionally – exactly the symptoms you describe. A number of things could cause this.
If you have always suffered from sooty plugs, it could be that your needles are set too high. If you regularly operate in a hot or high terrain, the lower density air will cause the mixture to go over-rich. The constant velocity carburettors will naturally compensate for this to some degree, but the coarse adjustment is made by the needle position. You might need to drop the needles one notch (Check your Rotax manual if you are unsure how to do this).
Are all the plugs black or just those on one side of the engine?
If the problem only affects the plugs on one side, then you could have a problem with the carburettor on that side. Remove the float bowl and check for:
Floats not punctured
Float height set correctly (arm should be parallel with base of carb)
Needles seating properly and Viton tip not damaged
No detritus on needle seat.
Gasket sealing properly (look for signs of leaking – light brown fuel deposits around the gasket line)
If the symptoms have only recently started and all the plugs are “sooty”, then you may need to look at the air filter. Check that it is not dirty or wet.
Also check that the float bowl vent pipes are not blocked and both connect to the airbox plenum, the float bowl needs to operate at the same pressure as the “filter” side of the carburettor and if it become blocked or disconnected, the differential pressure will cause the mixture to change.
Bit of a long answer, but the secret is to analyse how the problem began and use a process of elimination to point to the cause.
Lastly, if you do need to get hold of some Bing carburettor spares, let me know and I will put you in touch with an authorised Bing dealership that sells spares at sensible prices – not the kings ransom that Rotax charge.
Nigel
Normal 0 <![endif]--> On 16/06/2013 13:40, Richard Lamprey wrote:
[quote] | Quote: | --> Europa-List message posted by: "Richard Lamprey" <lamprey.richard(at)gmail.com> (lamprey.richard(at)gmail.com)
Greetings to all from Kenya.
Does anyone know what is the minimum cylinder head (coolant) temperature for normal operations? The manual gives maximum but no minimum, save for warming up to above 50C for takeoff power. I was told recently that cylinder head temp should not be too much below Oil temp, but not sure about this.
Some years ago I had new radiators made by Docking Engineering of Silverstone, after a leak in the Europa ones. They have proved so efficient that I cannot get the temp much above 105C after prolonged climb, and it settles to 80-90C in the cruise, against an oil temp of 105C. I put blanking strips on them to get the temp a bit higher, to 95C, but took these off to test recently, and down the temp went. The plugs are fouling up with carbon more now (with the odd missed beat), which according to the manual is caused by running too cool. But I cant find that optimum operating temperature stated anywhere. Any ideas appreciated.
A very simple Europa... 912UL, warp-drive fixed pitch.
Best
Richard
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402782#402782
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frans(at)privatepilots.nl
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| Posted: Mon Jun 17, 2013 1:03 am Post subject: 912UL operating temperature |
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On 06/16/2013 02:40 PM, Richard Lamprey wrote:
| Quote: |
<lamprey.richard(at)gmail.com>
Greetings to all from Kenya.
Does anyone know what is the minimum cylinder head (coolant)
temperature for normal operations? The manual gives maximum but no
minimum, save for warming up to above 50C for takeoff power. I was
told recently that cylinder head temp should not be too much below
Oil temp, but not sure about this.
|
My idea is that all the different materials and shapes in the engine
expand at a different rate when the temperature varies. For optimum
engine live and performance it is best to have the engine wearing its
moving parts against each other at one fixed temperature. If the
temperature varies, the wearing pattern also varies, and you will end up
with an engine wich is "loose" on all temperatures (i.e. loosing its
compression).
Also engine performance rises with rising temperature. Cooling the
engine means robbing its precious combustion energy, so keeping the
engine near its higher end of the temperature scale pays off. (Think
about that one: the reason we burn fuel is to rise the temperature of
the contents of the cylinder so that it expands and produces a force.
The more you take away the heat, the more you take away the driving
force. It is unfortunate that we have to cool at all, one reason why
engineers try to minimize cooling losses when designing efficient
engines. So keep the engine temperatures up, it is one of my secrets of
getting more speed for a liter of fuel).
The only way to achieve this properly is by controlling the amount of
cooling you apply. You can use thermostats or better yet, a movable cowl
flap.
I always maintain a coolant temp of 110C and an oil temp of 115C. This
also has the side advantage that I never reroute too much air for
cooling and this lowers the drag considerably. Some clever souls claim
that for the modern efficient airplanes 40% of the total drag consists
of cooling drag, so it pays off to tinker with the cooling system. (Of
course a thermostat instead of a cowl flap doesn't have this advantage).
Frans
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carl(at)flyers.freeserve.
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| Posted: Mon Jun 17, 2013 5:26 am Post subject: 912UL operating temperature |
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Hi,
We have been going through similar angst with our engine temperatures -
following a carburettor rebuild.
Ours was running hot due to us rebuilding/ servicing the carbs - we used the
proper Bing overhaul kit £145 per carb - ouch. We assumed that the float
levels would be set at the factory but this is not the case - there is a
tool for adjusting the float levels which can be hired (however there is a
much easier/ cheaper way - I can explain if you email me).
Anyway, during my attempts to get to the root of the problem I found a
really good chart listing all the engine temps/ pressures on a single page.
http://www.rotaxservice.com/documents/4STref.pdf
These guys are the Rotax service agents in Canada - they have loads of
really useful helps , tips and troubleshooting charts on their site
including all the carb data - jet sizes, settings etc.
Our cylinder head temps have always been fairly low - about 80% with oil
temps between 100 - 125 C. Max CHT I have seen was about 100 but that was on
the ground with reduced cooling.
I find EGT is a better indication of the mixture - before our problem was
fixed (getting the float levels correct) our EGT's were running at 870
(misfiring badly). Now correctly adjusted we are down to 780 and 800
(measured on the front cylinders - these are the coolest). My guess is the
rear cylinders would be 30-50 degrees hotter.
Good luck
Carl Pattinson
G-LABS
912 UL - 80hp
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Richard Lamprey
Joined: 15 Jul 2011
Posts: 95
Location: Kenya
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| Posted: Wed Jun 19, 2013 12:27 am Post subject: Re: 912UL operating temperature |
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Thanks everyone for their detailed responses, and to Nigel for info on carb adjustment.
This 912UL has 560 hrs, and I operate off a strip at 5500 asl, usual ambient temp is about 28C. So I am sure it will be running a bit rich, and I was used to slightly sooty plugs, but not to point of misfire. Recently I have been operatring a bit more at 12,000' asl (yes a 912UL/ fixed pitch prop will get me there, but only 1 up)
I havnt done any carb adjustments recently, but having unblanked the radiators it all got worse (all plugs but especially the cool back ones, (3 and 4) , so the first thing is to blank them again, and see. And fly lower. Not enough time for all these tests, but will try a bit at a time over the next few months.
If it persists, then I'll look at the carbs again.
Thanks again.
All best
Richard
Kenya
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