I've been in this hobby less than a year. Started with a 4 stroker, then a 2, then a wankel, then electric, now diesel. Just got the Davis conversion for my .46fx. It took me quite a while to tune it. so here's the way it went.

It started but didn't run well. I followed directions and it sounded like a hard knock so I backed the compression off, trying to follow instructions... It ran worse. I ended up tightening compression all the way up to get it to run well (without misses) but couldn't get rid of the knock. I kept wanting to back the compression off as I didn't know of that was a bad "knock" or a predetonation thing (which it really couldn't be being a diesel).

So I finally toyed enough with it (I hope that oil doesn't stain the driveway too badly) that it seems to run well. I revved it enough and played with the needle valve and either it was going to fast to not notice the knock or it went away. When I came back to idle it finally sounded smooth. Went WOT again (rather around 80% as suggested) and transition sounded ok. My settings now are 1/8th turn back from all-in compression and about 1 turn out from needle valve all in. Are these bad settings? I'm swinging a 12x8 about 7500 rpm max. I just worry about too much compression....

I don't think the wife will like the smell around here too much but it more manly than glow fuel smell

Any suggestions on starting it next time? Should I even try hand flipping, back compression off....?

your not supposed to use an electric start on a diesel. they can flood easier and be damaged. thats all i know about them. sorry.

I sometimes use a starter on the initial setup, starting with the compression low enough that it won't start then work my way up. It should flip start quite easily once set up and you will seldom need to touch the compression or the mixture. Don't worry if it rattles a lot when first started, this only lasts a few seconds.

onthefly,
Next time check that the prop is actually revolving. Sometimes when you start a diesel it will detonate, that is pop so that the prop swings, then fire again as it comes up on compression, never completeing a revolution. It just oscillates back and forth. If this happens, usually lowering compression will get it firing in the correct direction. If it starts backward, the scavenging will shut it down and you can restart.
May not be the problem, but something to watch for.

George

Well got out there to start this morning, and what a great morning. 46F calm sunny, oughta warm up to the 70's.

So I tried hand flipping this 46fx conversion. No good. Backed comp off a little, nothin. After trying for 20 minutes (and after 10 I got a hair dryer to warm the cylinder head a bit) I threw the electric on and it started right up. White smoke, knocking then I screwed compression in a bit and it smoothed out. Still had a few knocks but when I put the plane in a nose up attitude it smoothed right out and sounded nice. Every time I put the plane level it would knock again. So I went down to idle and it died (around 2800 rpm). Opened throttle, hand flipped, no go. Primed again, hand flipped, no go. Electric, starts. I get 8600 rpm with the 12x8 - impressive. I richened it up and got it to idle but transition wasn't too good and nose up still does better. I'm lost on this thing and will it ever hand start?

This will tell you all you need to know!

http://www.carlsonengineimports.com/...eselinfo.shtml


Max

onthefly,
If it smoothed out when you put it in a nose-up attitude you may be running it too rich. That coupled with the idea that diesels run cooler may mean that you are not getting the ABC cylinder up to proper running temp. This COULD cause excessive wear.
I would suggest adjusting the needle to max, readjust compression, etc. until you find the optimum settings. Don't assume final settings until the engine has run a couple of minutes to warm up properly.
If the starter works for you, by all means use it. Just be careful of hydraulic lock. It is a good idea to flip the prop before applying the starter to prevent damage.

George

Was this a new 46FX?I guess my question is how much time was on the engine before
putting on the diesel head? You need a nice wear in burnish thing between the piston
and liner The OS46FX I think may use nickel in the liner plating which will break in
rather quickly,Irvine is a hard chrome plate takes a little longer,But they still must
be broken in on glow the fact that your are running the compression screw that far
down makes me think of the run in. You have compensated by "increasing the compression" not really your are bringing it up the the point it will run. When it is
well lapped in, You may find that you well could be a turn out for normal running
Also make sure there is only one head gasket in there, the OS46FX diesel conversion
is one of the best, I had a similar problem with my irvine 53 I benched it for a few
more tanks of glow-- bingo--Backed off the compression screw now have a big spread
but not needed,Yes when they first start knocks bangs which goes away when warmed
up. Years ago I had a mercedes 220 diesel you could hear this thing banging and knocking a block a way in the winter when first started. Little diesels or big ones
sound like this cold

Onthefly One more thing dieselfuel no nitro but nice oily kero along with the oil
what can rust??? I have never used afterrun oil in any of my diesels or every heard
of a rust problem with them. Last year I was flying one of the diesels and one of the
4 strks no after run oil I just put a little diesel in it cranked slowly by hand ether
evaporates its fine ( no not recommending for after run in glow engines but my mag52 4 strk is fine) Just ran it today

I broke the 46 in as per OS instructions. and then I probably have 2 hours on it.

I ran it for a couple of minutes over half throttle and it seems like I didn't do any favors to it[:@] Could the air temp of 46F make it difficult to get this dialed in?

And thanks for all your help so far. I may be leaning on you for more. The hobby stores I've talked to in and around Salt Lake don't know of anyone that uses diesel so I don't have anyone to show me the ropes.

46 degrees?? I think they figure on an ambient temp around 68-70 you may have to
figure a way to keep the heat in, diesels run cooler than glow to start with (by the way
2 hrs glow break in fine ) maybe block off a couple of fins with a foil wrap this would
certainly explain why you have the compression screw down that far for good running
it brings up the heat, if you are at a high altitude air is thinner too

I thought that once the compression was set correctly there wouldn't have to be adjustments at different altitudes. That went against what I reasoned but that is what I was told.

Onthefly,

Go ahead and use an electric starter, BUT be careful. Do not prime. One or two choked flips at most. An electric starter will get you going after a second or so. You mentioned that you used a 12x8. What brand? I use a Master Airscrew Scimitar 12x8 and my Mecoa .46 will turn 9,700 to 10,000 RPM. Your OS should be the same or mabey a little better. This Mecoa was my first "large diesel" and I had the same setup problems that you did. Take your time and try to sneek up on max power from a slightly under compressed condition. Exhaust residue may be dark amber but not inky black. With the 12x8 prop my engine was over compressed on the ground, but in the air when I throttled back below 1/2 throttle it burped and missed in a way that sounds quite cool. Transition and power were there for touch and go's.
To keep ypur fuel fresh (critical) and reduce smell. I recomend this method to ALL diesel users. After my first empty Davis gallon I soldered DuBro fuel can connectors thru two holes that I drilled into the cap (using the supplied nuts for extra strength. There is a brass tube to the bottom of the (with 45% bevel on the bottom end) can that the yellow tygon tube attaches to. The black neoprene connector only goes in an inch. I disconnect the filler nipple from the black tubing and 20 cranks (6.5 oz) later I reconnect to the black tubing and fly. My fuel does not go flat! Even the last third gallon can that sat in my garage all winter. No more messing around with pouring fuel from the gallon can to a smaller container. Now when one can empties I just move the lid with tubes. I've been flying diesel for four years now; I wish some one had shared this with "ME" when I started. In the summer time I also put my gallon fuel can in a bucket with whatever "blue ice" pieces I can also fit in the sides.


Oily in Germantown
Francis

Where did you get the hand crank diesel/gas fuel pump Francis(I've only seen electirc powered pumps for gas/diesel)?

Luftman,

It is a "Hanger Nine Ultra" from Horizon Hobbies.

Oily in Germantown
Francis

Francis,
I see the neoprene and tygon tubing but the white/translucent appears to be silicone. Have you had trouble with it? I would have used only tygon or neoprene.
Nice set-up!

George

I also use on of those hangar nine hand cranks for gas/kero but make sure your lines are ALL tygon...

AJC

GCB,

I do not know what the whitish looking tubing is made of but after several months of use it shows no ill effects and Hanger 9 says that this pump is for gas/diesel. It is, however, nice and flexible.

Oily in Germantown
Francis