topper5

My Feedback: (12)

I recently bought a used 3w 80xi comp series motor here on RCU and it over heats, rather its on the ground or in the air, depending on how hard i fly it it gets between 225' and 260' degrees, i put new rings a new reed and carburetor kit in, i cleaned all the carbon off the piston and out of the head,
it still overheats, with in 5 minutes just trying to tune it on the ground it starts overheating and i have to shut it down so its not a baffling issue, i cant find an air leek, plus it only has the power of a 60 or 70cc motor, 6900rpm and 34lbs of thrust with a 26a vess, what am i missing here?????

MetallicaJunkie

thats the same problem i have on my 80xi but it would happen in flight... im just waiting for some gasket maker to fix it up

w8ye

My Feedback: (16)

Did you set the total timing at 28 degrees

dubs1946

Yes check the timing, mine was set at the factory at 8 degrees before TDC.and it should have been 28 degrees. that made it a pig to start and it turned 500 revs lower then it should.

MetallicaJunkie

how do you check the timing?

w8ye

My Feedback: (16)

To set Timing

topper5

My Feedback: (12)

i set the timing at 0' degrees for the red (north pole) witch makes the green (south pole) 55' degrees according to the 3w manual, im not using a CH ignition im using a 3w so i don't think the 28' degrees would apply, (but i could be wrong) i will check and see if the censer will hit 28' degrees

RTK

My Feedback: (1)

Dependin on where and when you take it, how accurate your measuments are, 225-260*F is not overheating, I don't care what the manual says.

topper5

My Feedback: (12)

i have only dwelt with about 12 gas engines thus far and none of them have ever gotten up to that kind of temp, but after a hard flight on the 80xi, i can drop the throttle to an idle and float by with out the motor skipping a beat, there is no indication of overheating other then the temp gun.
so saying its not overheating is kinda what i was hoping for, but it dose still have a strong lack of power, 6900rpm with a 26a is horrible at 4500 feet, i should get that and maybe more with a 27b

thanks all for all your input

w8ye

My Feedback: (16)

http://www.3w-modellmotoren.com/moun.../80xi_engl.pdf

RTK

My Feedback: (1)

http://www.prme.nl/forum/viewtopic.php?p=506#506

This is better than any manufacturer has ever explained or will ever explain about cooling. You can thank Pe

Tired Old Man

My Feedback: (1)

260-280 is not hot. Over 325 is hot. The 3w manual places an artificially low max temp number on their engines. The don't even start to run good until 225. I don't believe there's anyone in the entire RCU membership that has run as many 3w's as I have and I'll use that as a partial qualifier for the temp numbers.

RTK

My Feedback: (1)

TOM,-325*F might be hot for some engines, but it is not hot for some other engines. There isn't an echo blower that runs below 325*f in the summer, compression stays, there bearings don't fail, but then again they are not held in with lock-tite
Rotax/Hirth, one of them, red line is somewhere between 425-450*F if I remember correctly. I guess it all depends on the tolerances, metallurgy, and design. Some can take it, some can't, but they all can go past the numbers one manufacturer states.

Tired Old Man

My Feedback: (1)

Ralph,

I pull down several brands of engines every day. Because one does not immediately see the damage does not mean it did not occur. Usually it's initially found in a compression loss, or, if dynoed, in a substantial change in the exhaust gasses. What that upper level is does depend a lot on the brand and the amount of case and cylinder mass, but your 400 is a critical zone for any of them. Yes, I run up there too, and typically those engines have a pronounced loss of compression after shut down which recovers somewhat after cooling.

For some, redline temp is the temp the engine is no longer usable and establishes a point that the engine must be removed from service regardless of how long or short a period of time the engine had been at that temp. Others use a sliding scale basd on temperatures and time at temperatures. Lower temps permit longer periods at which they can run that way. Higher temps have shorter periods before removal from service. If you remain below 325-335 it will work for most all of them. Easier that toasting an engine by trying to determine the exact failure point.

Ih82crash

I have a 3w 85xi and I am only getting 6600 on a vess 26A. I had no idea it was running so badly until today!!

arobatx

Topper..

I've not run the 26a Vess on my 80....so perhaps they are a much lighter loading prop than I have heard. I'm alot closer to sea level here, and run a Mejzlik 26x10 on my near new 80xi (maybe a couple gallons through it), and I'm seeing 6500. I understand you have the comp series, where I don't. Yours may take a bit longer to be fully broken in, and even then, I wouldn't expect much if any more than a couple hundred RPM more on the same prop. If you fitted a new ring, your break in process started all over, and you have quite a long ways to go. I can't imagine getting more than 6900 out of a 26a Vess here at my level, let alone yours. I have quite a ways to go before I would consider mine broken in...at 6500 the mejzlik is just starting to think about ripping in the air...I bet the Vess is loud at 6900.

topper5

My Feedback: (12)

im only going off what others have said they got on rpm 6700 - 7200 with a 27x10, that's why i felt mine was under powered getting the same rpm with the 26a, but i am starting the break in over, i only ran 1 gallon of 32:1 break in to seat the rings, now im on 50:1 knowing the rings are not 100% broke in yet, but it is picking up rpm daily, Sunday i got 7050rpm with the 26a and backed it down to 6890 for flying, (witch produces 34lbs of thrust according to my fish scale) i guess im glad to here the motor is not a complete failure, but still under powered for my needs as a 3d pilot, im at 4500' feet so this motor would do a lot better closer to sea leave

RTK

My Feedback: (1)

A lot of people quoting numbers are forgetting to let people know they are running a pipe.

icando3d2

My Feedback: (15)

i have a 27 vess and its pulling 44 lbs of thrust on a digital set of scales after getting it back from AI. it really woke up after i changed the can out to a bison muffler they had there

topper5

My Feedback: (12)

44lbs is great, i haven't cheeked my thrust in a wile, the motor should be getting close to max performance by now, i have a vess 27a on the way and i will be checking the thrust again this week end with that, like i said the vess 26a was getting around 33lbs and on a 23lb plane and punch out sucks.

arobatx

When you had the cylinder off, did you confirm the cylinder bore is true throughout the stroke with the new ring placed into the bore just above the exhaust port, then again further toward the top of the stroke (measuring end gap)? This is probably something I would have done with a used one, especially exhibiting symptoms of overheating or loss of compression, just to be sure.

topper5

My Feedback: (12)

i didn't think about checking the bore until the day after the motor was back together, it would have been a good idea had i thought to check the bore wile i had the head off because one of the old rings was a little burnt showing signs of blow by, but the temp has come down after the re build and maintains about 225' verses 240'-250' F.

arobatx

...so what exhaust are you running?

topper5

My Feedback: (12)

pits

topper5

My Feedback: (12)

im running a pits