Engine Event and Thermostat Operation

[daveb]

Running a 582 with 37 hrs. On warmer days water temp would go fairly quickly to 75 – 80 degrees centigrade and stay there. On a hot day it would start to edge over. I’ve added some cowling for the radiator and temp dropped to 65 to 75 although not yet tested on a hot day.

My last flight, air temp 16 degrees C, water temp was not above 60 during a X-Country flight and I had several engine ‘incidents’. At different times 3 loud bangs were heard and felt through the air frame. Finally a loss of power for a few seconds. I was able to land very shortly after this. This ‘bang’ had occurred once before after about 10 hrs.

I checked the fuel for water and the bowls were OK after landing. I didn't notice engine temp changes during the incidents but might have missed it.

Should the thermostat allow the engine to reach 80ish degrees and then stay there? Is 60 hot enough for the 582? Any thoughts on my big bangs :eek: :eek: and momentary loss of power?

Dave

[Ron Marlett]

What is the installed thermostat rated at? What do your spark plugs look like? I would think that 60C might be a little on the cool side, but it should still run OK. I think the bangs and unpredictable running are comming from another problem. Do you have EGT probes installed? Is this a dual ignition engine?

[daveb]

Ron,
I don't know what the thermostat is rated at, operating range for these engines is 65 - 80C, it has dual ignition, both working OK independently and together and oil injection which appears to be working and set correctly. EGT probes are installed and were showing normal although if there was a slight rise at the time of the events, I could have missed it. I haven't checked the plugs yet.

Dave

[bones]

Ok dave, a few things to ask 1- what fuel pumps do you run, pulse or electric, because i know that those bloody pulse pumps can stop and start when they feel like it, 2- do the bangs feel like they are motor or gear box, like i mean does the motor drop revs or does the thrust drop off, just thinking that if it was just the thrust it may be the cogs in the gear box slipping on the shaft. Either way it is a bit of a problem to try and find some thing that is so intermitent
The temp that your running at should not be a problem cause mine runs about 65 deg C and thats feedin it to all the time, the cooler you can keep it the easier the oil has to work to keep it spinnin

[daveb]

Using the brand new pulse pump for now that came with the new engine (an electric is on the job sheet!). I didn't notice any rev drop or thrust change for that matter just an audible bang and a bit of a jolt through the frame. The jolt might point to thrust?

While the engine is new, the C type gear box has had 400+ hours. Last oil change was 37hrs ago and a new gasket kit was installed then when it went on the new donk. I assume the guy who put it on had a good look.

One theory was that as it was running cooler I might be getting momentary seizures due to uneven expansion of the cylinders and cylinder walls and that a bit of wet and dry in the right spot would sort it out. This was from a racing motor cycle view point.. :confused:

The drop in power might be unrelated to the bangs as you say.

Dave

[gyromike]

Hmmm...

A cool motor on a cool day, maybe it was carb ice?

I don't have a whole lot of Rotax time, but I seem to recall this being brought up before.

I've had it happen on my Mac engine though.

[Ron Marlett]

That s why I asked if it was dual ignition. If you skipped a spark for 1 cycle, you would have 2 cylinder's worth of exhaust in the muffler that the next power pulse might ignite. This would give you a lag then surge that you could feel and a Bang/backfire through the exhaust that would be noticible. When we first got our riding lawnmower, My wife was not heavy enough to stay in the seat when she rolls over bumps in the lawn. She bounces up slightly, goes light in the seat and the seat mounted kill switch interrupts the ignition system for a short time untill she re-settles into the seat. When the engine re-fires a fraction of a second later, it ignites the unburnt fuel that was pushed into the exhaust by the previous non firing cycle. makes a really big bang... This of course is a less likley scenario on a dual ignition engine such as you described unless something is amiss that effects both ignition systems at the same time. Are the 2 ignition systems on seperate kill switches?

I would still investigate the plugs and look for any unusual running conditions. I would think that fuel starvation such as from a malfunctioning fuel pump would manifest itself over a slightly longer duration such as the momentary loss you described.

[Aussie_Paul]

:) :) :)

[Aussie_Paul]

.....What we have is a brand new engine. We all know that new engines are "tight" and have not worn the "high" spots off for at least 50 hours and possible longer.

If the thermostat fails and the engine temp is lower, or on the low side of the specs. Is it posibble that the opistons will have the usual expansion, and the cylider walls a little less expansion due to being colder. With this new engine, that has not worn all the miniscule high spots off yet, could the lack of piston to the cooler cylider walls clearance couse these min siezures?

Once the engines have done 100 hours, these emgines seem to be far less pron to water temp related problems.

After 100 hours, I have run them at all sorts of temps for short durations due to removing a faulty thermostat, and having to keep flying.


Am I out of my TREE or am I making any sense??

Mceagle Tim, I know, has humungus experience with Rotaxes used for mustering in the early 90's untill they went to the ea-81 and now to the Rotax 4 bangers.

Tim, could you please shed some light on experiences, relating to Daves problem, that you might have formed an opinion on?

Aussie Paul. :)