Diesel Advice

Godsey3.0 Thu Sep 20, 2012 4:21 pm

Hey everyone. I finally managed to get a good mix of diesel fuel. I ran a worn out Cox .049 and my .09 McCoy Redhead on it. The Cox was difficult to do anything with. It has very little compression when cold. Next to none when hot. Takes about a second to get it to tdc with constant pressure. The McCoy was difficult to start but way easier than the Cox. I find that they get difficult to start when flooded. Not flooded to the point of locking up. Just to much for it to light off. The fuel tank I have been using with my McCoy is up a little too high and it would pour into the engine. This stopped when fuel started to get lower in the tank. I could get the engine to start very easily with just a prime. With the tank connected it would hit and then die when fuel go to it. I leaned it out and tried again. It started up again. I raised the compression and leaned it out a bit more. When it died it would take off in rpms. I imagine I have it rather rich and raised the compression to compensate. I will try and adjust next run.

The whole reason I brought this up is to see if anyone had advice for diesel engines. Whether it be fuel percentages, prop size, or how to run them. I am going to see if I can scrounge up a better condition pylinder assembly and try it on my diesel Cox engine.

Rolla

Surfer_kris Thu Sep 20, 2012 4:26 pm

You need a good fuel, a good piston to cylinder seal and a large prop, that's all.
What fuel and props have you been using?

Godsey3.0 Thu Sep 20, 2012 4:58 pm

The fuel is not really exact percentages. I shot for around 25% Castor, 45% Ether, and 30% Kerosene. I think some of that ether evaporated during the whole process.

Prop for .049: 7x4

Prop for 1.5cc McCoy: 8x6

Godsey3.0 Thu Sep 20, 2012 8:50 pm

I just ran my Map3 2.5cc engine. It was loads easier than the other two. I could not really tune it too well as the needle valve is about level with the plywood I mounted the engine to. I cut out a small shape for the engine to slide into. I had to make a shape for the needle as well. But it is still difficult to get to it. I ran this one with a 9x5 Topflite. Same fuel as the others. I am starting to get attached to these diesel engines. I love the smell and the mess.

Would a throttle ring work well on a diesel Cox? I recall that mine tended to run hotter with the ring. Will this mess up the compression setting?

Rolla

Surfer_kris Fri Sep 21, 2012 12:35 am

I think you better get some good commercial fuel first before you mess with your own blends. That way you'll have a reference for how they should run. The level of ether is important and well as the level of ignition improver.

gcb Fri Sep 21, 2012 1:38 pm

This site have a lot of diesel info. It is presented by some Canadian Diesel Combat folks and has extensive information on break-in, running, fuel, etc.

http://www3.telus.net/dieselcombat/diesel_care.htm

Peruse through the different sections...LOTS of valuable info. Although some is specific to PAW, most works for ALL diesels.

George

Godsey3.0 Fri Sep 21, 2012 3:53 pm

Hey Kris: I have tried the Davis stuff and did not care for it. Mainly because the percentages are not listed. I am getting better runs with my own mix.

gcb: Thanks! I will definitely look through that!

Surfer_kris Sat Sep 22, 2012 12:21 am

Okay, I've never tried the Davis 1/2a fuel myself, just trying to eliminate a potential problem.

If you are using a diesel head with a Teflon gasket, I have never managed to get a good run from them either. The gasket always leaks more or less and it is impossible to get a stable run, even for just one tank, from them. You can use a gasket from a sheet of brass instead. This seals much better and will give you consistant runs for more than ten tanks at least. The brass can break too though if one changes the compression setting a lot. A 7x4 is a good starting point, I usually get the best results when aiming at top revs in the 10000rpm range. A larger prop means a lower load on these engines, contrary to glow engines.

Ivanhoe Sat Sep 22, 2012 1:36 pm

Small diesels are not easy to start, diesel conversions even worse. My advice on prop sizes would depend on the actual engine, but roughly, for control line use, an .09 or .10 would use a 7 x 6, a .15 8 x 6.
R/C or f/f increase the diameter by 1" but reduce the pitch to 4"
An 8 x 6 is too much prop for an .09, 8 x 4 would be as much as you want.

There is a definite knack to starting a diesel, with experience you can "feel" if the engine is going to fire, the technique is left hand on the compression screw, right hand flicking the prop, your left hand moves the compression back and forth until the engine fires, then increase or decrease until it starts.

I'm afraid there is no replacement for experience.

Godsey3.0 Sat Sep 22, 2012 5:27 pm

I ran the Map a bunch today. I am able to get it to start in about two flicks with a prime. I currently have it running rich and under compressed. I did some research on my .15 and some said for this engine to use up to a 10x6 at the most and an 9x4 for break in. With the 10x6 it runs great. I need to try a smaller prop.

Rolla

Surfer_kris Sun Sep 23, 2012 1:18 am

My peewee diesel is the most easy starting engine I have, just prime the side of the piston (port closed) and you get first flip starts. On engines with mufflers it is a little harder to prime correctly and it can actually be easier once they are in a plane as you can then rotate the engine an get the fuel to the top.

A think a cox engine on diesel needs a little tighter piston/cylinder fit compared to a cox engine running on glow fuel. On glow fuel they seem to rev a little better when everything is a little loose and sloppy, while on diesel you do need a very good compression seal for the cold start and for consistent running. The peewee has never seen any glow fuel, just diesel from the first run.

proctor Sun Sep 23, 2012 9:50 am

Couldn't help chipping in, been running an assortment of diesels all week.
Use commercial fuel but even then you sometimes get a tin where ether
has evaporated off and this can be a real time waster.
They all have there own characteristics. My long stroke Mills 0.75, 0.049 ci
will happily run an 8x4 for free flight or radio.
A way to avoid flooding is to disconnect fuel tube, prime through venturi,
flick and slowly increase compression till it starts and runs off the prime.
Connect fuel tube, one choked turn and it should start within a couple of flicks.
The small ones are harder to start and need a fast flick and I don't hesitate
to press a Cox spring into service.
Latest diesel I am using is a Schlosser 0.25 cc, a total joy, first flick starter
but I would hesitate to mention what I paid for it in polite company.
Good luck with you diesels, I love 'em.
John

gcb Sun Sep 23, 2012 5:39 pm

Godsey3.0 wrote:I ran the Map a bunch today. I am able to get it to start in about two flicks with a prime. I currently have it running rich and under compressed. I did some research on my .15 and some said for this engine to use up to a 10x6 at the most and an 9x4 for break in. With the 10x6 it runs great. I need to try a smaller prop.

Rolla

I broke mine in on a 9x4. By now you should be running at peak for 1-2 minute bursts followed by complete cool down. Stop the engine by pulling the fuel tubing and let it cool naturally. Each run/cool is called a heat cycle. After about 10 heat cycles it should be broken in.

Both of my MAP3's have the exhaust/muffler ring. I initially turned mine upside down to get access to the exhaust ports for break-in.

George

Godsey3.0 Sun Sep 23, 2012 7:14 pm

I fired up my Aurora .09 today. It ran good besides the fact I had little needle control. It must have an air leak somewhere. I will be sure to heat cycle the Map3. Mine does not have the exhaust ring. The engine is not that loud though so it is not a problem.

One problem I have now is, I RAN OUT OF FUEL!! I gotta buy more John Deere Starting fluid. I love running these things. It is really fun.

Rolla

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