H2O

[666]

I notice that MVVS are now coming out with a water cooled 116 flat twin as well as a inline. They have had the water cooled 58 out for a long time, since 2004 or 5 but it isn't exactly a hot seller so far. I am thinking it was a product before its time.

It is in theory the inline that interests me, but since I found out the engines are coming out I have been doing some serious research on the concept of water cooling small gas engines.

One of the biggest issues the air cooled engines we use is varying temperature in flight and varying mixture because of it, also because the cylinders do not expand perfectly round at all the temperatures the cylinders go through there is premature wear and poor compression issues.

We tend to detune the engines as compensation, run them rich, and run excess cooling air to the cylinders so they won't overheat during the 2% of the flight when they are under the most load and get hottest, say on uplines, for the rest of the flight the cooling set up would then be severely compromised and also the tuning.

Water cooling and controlled cylinder temp means we can lean out the mixture for max power with confidence.

The boat guys say they get considerable power increase with water cooling.

People are quite willing to a small weight penalty by fitting tuned pipes to gain another couple of hundred rpm, water cooling would be very similar, a small weight increase for 3 or 4 hundred rpm more.

With speed controlled water pumps, computer radios, modern telemetary that could easily control say a ADI liquid onto a small radiator and valves depending on head aand water temp, could water cooling be the next new frontier of model engine development?

Discuss

 

[TazmanianDevil]

What you wrote already exist in UAVs.
MVVS main market for these engines is UAVs.
I'm not a teck guy but is t water cooling and tune pipes is a whole different concept ?
The thing is you'll need to control the temp not when you're 200 ft above when you fly it's when you fly your UAV 1000 or 3000 ft, the the air density and the outside temp are colder, much colder.

 

[3Dchief]

I guess it depends on what you are putting it in. I agree with all the benefits of water cooling and tuning, but for any plane weight is the enemy. In a large scale plane flown scale, it would be great. I don't think the same would be true in an acrobatic plane. I just don't think you would gain enough power to offset the weight penalty. Plus the cost goes up considerably compared to air cooled, more moving parts and machining, much more complicated than air cooled.

 

[666]

I agree weight and cost is the issue, even a cheap water pump and radiator would cost $ 200 minimum and weigh 400 grams extra. Engine would cost another 200$ to buy.

But I suppose my point is that is no more complex, expensive or heavy than changing simple cans out for tuned pipes and headers, with a similar level of performance increase and a smoothing of the mid range.

 

[3Dchief]

I know there would be increased performance similar to pipes, but I think the weight penalty would be higher. 400 grams for plumbing and radiator might be possible, but the coolant itself would be another 2 pounds minimum.

 

[666]

The long established MVVS 58 lc uses a radiator that weighs just 138 grams and uses less than 200 ml of cooling liquid, And it is more than up to the job. Pipework weighs almost nothing. Half a pound of cooling liquid even if two complete and seperate cooling systems were used, one on each cylinder.

In reality, a 20% weight saving could be got off of that by using a single system,

Not as heavy as people seem to assume.

On an aircooled twin, Headers, clamps, teflon joiners, tuned pipes and mounts add nearly 800 grams in weight above a simple can exhaust system.

Very similar weights, with similar performance increases.