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Author Topic: diesel engine run in time  (Read 336 times)
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I hate trees
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« on: October 07, 2010, 03:22:44 AM »

Hi Guys,
I'm in the process of running in the CS Elfin 2.49 to go into my "All American" that I've posted about.

This engine was bought for my Dad, as he had an original Elfin, which he eulogised about. The CS was pretty bad and wouldn't run very well, particularly when it got hot and would not restart. I sent it to a respected engine man here in the UK and he rebuilt it, apparently it had a steel piston of the same material as the cylinder, consequently the expansion rates meant that it was never going to run properly. He made a new cast iron piston. The engine has a lovely bouncy feel and is a good starter. I have now run it for about 20mins or so. Whenever I try to increase the compression settings for a full power run it tightens up after a few seconds and I have to back it off and let it burble away again. It will happily run for 4-5mins slightly rich and under compressed without getting too hot. How much more running might it need?

Adam
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dputt7
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« Reply #1 on: October 07, 2010, 03:47:46 AM »

Adam
I'm no expert but I would have thought 20 mins was long enough. Dave Owen, a respected dealer in diesel engines in OZ, suggests to run 10 tanks through a new M.P. Jet diesel with just enough comp to keep it running, then you can start to lean it out and add more comp for full power. I say again Im not an expert and I would be contacting the "engine man" for his suggestions. Failing that I'm sure someone here will be able to advise you.

Best of luck
Dave
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DaddyO
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« Reply #2 on: October 07, 2010, 04:41:20 AM »

Hi Adam

Run In time will vary engine to engine, as you know. Wink

I used to run my diesels for about an hour before putting them in a model (flying control line). I'd run a tank full at a low burble and then let the engine cool down before repeating. After 20-30 minutes of this I'd increase the rpm and run it at a higher speed for a few runs gradually increasing the rpm till it was able to run flat out without overheating. I'm not sure that this process was the best for overall power, but it did give a nice reliable starter that would run at full rpm. Roll Eyes

When examining the piston after all this, (although I preferred not to disassemble the engine once it was running well), there is a ring of bright metal around the top edge.

Hope this helps and good luck with the model
Paul
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algy
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« Reply #3 on: October 07, 2010, 08:30:34 AM »

Hi Adam.
I am no diesel engine expert either but I have quite a few and have had no problems running them in. As Paul suggested each engine has it's own "run in" time. There is no magic duration. The best way seems to be short engine runs until the motor gets hot. Then stop it by pinching the fuel tube closed. Then let the motor cool right down. Then keep repeating the procedure gradually increasing both the duration of the engine runs and the revs.

It is usually acknowledged that it is the heat cycle that is very important. The heating up and natural cooling down of the motor and the subsequent expansion and contraction of the piston and piston cylinder. This allows everything to stabilize and form a good running fit.

Also suggest that your fuel have at least 20% Castor Oil for running in. 30% is better still. Diesels love Castor oil. Are you using Castor Oil? It is the only oil I recommend for them. If it does start to sound laboured or if it gets to hot close it down immediately. The symptoms you have are also the same symptoms for a lubrication problem of some kind. How do I know? Cos I have "Cooked" a perfectly good PAW Diesel by accidentally going below the recommended Castor Oil percentage for the engine (18%) by trusting to a "Supermarket" kitchen measuring jug". I now use a very accurate Dark Room Chemical measuring beaker. We all learn by our mistakes. I was flying it in a free flight model at the time.

Also as Paul also suggested it is not a good idea to take them apart once they are run in. It's very hard to exactly match up the working surfaces again and there could be some loss of power.

Hope that little bit helps and know doubt those more knowledgeable then me can also feed you some advise.

Cheers

Algy

Nope i will not go into any discussion on Castor Oil V Synthetic oils. That can of worms has been going on for centuries. Boring.
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applehoney
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« Reply #4 on: October 07, 2010, 09:26:46 AM »

I have to admit that I have never run-in an engine of any type in my life. I just bolt 'em into a F/F and go fly ... the typical short fast runs, well cooled between, have always seemed quite adequate and the engines just get better flight by flight.

My confession of the day..... Roll Eyes
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I hate trees
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« Reply #5 on: October 07, 2010, 11:49:54 AM »

Thanks for your words of advice and encouragement.

I've been out again today and another 5 mins of running has done the trick!

I adjusted it to run a little bit leaner and after two or three runs it ran undercompressed but gradually picked up until it after about a minute it was singing away. On the next run after letting it cool it started on the running settings and picked up and ran just the same again and ran a tankful out (approx 2 1/2mins) no problem. I put the tac on it and it was doing 12.5k on an 8x4 prop so it seemed to be going a treat. Smiley

I've bolted it to the model and will now start the long wait for a nice bit of trimming weather.
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