Diesel Dave-RCU
Posts: 46
Joined: 12/22/2002
From: Monroe,
MI, USA
Status: offline
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ok guys here we go,
nose-dragger,
It looks like you have found the directions for the PAW diesels, Those are the ones that require the fuel from Tower, with the extra oil. All I have heard about them is good, but I don't have experience with them. "I have heard" they are hard to transition the throttle, they like to labor a lot. I don't know, I have never ran one.
John,
I have been flying with diesels exclusively since 1996. I had a trainer flying with one for 3 years till it got claimed by a radio hit at a float fly. I haven't seen any problem with structural integrity on any of my planes due to the fuel, residue, or torque. However reinforcing the firewall a bit, might not be a bad idea.
The fuel economy is almost double that of a glow engine. The reason is that a gallon of 10 percent glow, is worth about 10,000 BTU's, where a gallon of Diesel mix, is worth around 18,000 (my numbers might not be right, but they are ball park) Considering you have so much more power in the diesel fuel, over the glow, you will need less of it to do the same job. Matter of fact, in the directions for the Davis heads, they tell you to start with the needle valve set at HALF OF WHAT IT WAS SET AT TO RUN ON GLOW!
Starting them can be a challenge sometimes. An electric starter is a must. I don't usually prime the engines, because you could flood it out, and seriously damage it if it were to pull liquid fuel into the cylinder. I don't want to break a connecting rod. I just usually crank the snot out of them till they draw fuel and fire on their own. I have gave up on a field battery for this, and opted for a 55 cold crank amp tractor battery, and a high torque starter.
Your friend with the diesel. I am assuming he has a Davis conversion, by looking at what you wrote. Tell him to run the head screw all the way down, then back it out 1 1/8 turns. set the fuel mixture at half of what it was on glow, or start at about 1 turn out if he doesn't know the glow setting, open the air bleed, or idle air adjustment screw 2 full turns, and that should put him in the ballpark.
When he starts it, set the throttle on the radio to about 1/4 throttle, and crank the hell out of it. When it lights, it will miss, bang, clang, smoke, shake the plane, spit, sputter, and act like it is going to die, till, it warms up. This is normal, and usually draws very strange looks from people that don't know what is going on. (Told you these engines are fun.) Once it warms up, and smooths out, run the throttle up, and set the head first, with a tac, and listen very closely. as you turn it in you advance the engine timing, turn it out you retard it. Turn it in till peak rpm is reached, BUT DO NOT GO PAST IT, OR YOU WILL CAUSE A ROD KNOCK LIKE YOU GET IN A CAR, AND YOU WILL BREAK SOMETHING!!!
Then adjust the fuel mixture till you hit peak rpm, and slightly richen the mixture. Doing this is not like a glow engine. if it is missing it is too LEAN. if it is laboring it is too RICH. Be sure to use a tach. after you do all this, go back and reset the head as described earlier.
Slow the engine back to idle, wait 10 seconds, at slowest idle possible then slam the throttle open. If it labors, open the idle air bleed more, and try again.
Make sure you are using enough prop. I would prop a 25 with a 10x6 at least, 40s with 11x7, 61s with about 12,14x7,8. This all depends on the plane of course.
Your target rpms full throttle, just over 10,000, and making dark brown, or black oil at the exhaust, and around 2400 rpm at idle. If it is set just right, it should transition like a glow engine.
Now lets talk fuel. You said he is mixing his own. I would guess he has the mix from Davis, that you have to mix equally with kerosene. Using unscented lamp oil is quite ok, it "IS" the same thing. Matter of fact, you could use scented lamp oil, if they still made it. I have used lamp oil, scented, unscented, and citronella oil to literally "spray the field for insects". lets see what else, truck diesel fuel, but it didn't work too well. I haven't tried jet fuel yet, maybe someday. Now I just usually order the fuel mixed from Davis. the price is right when I order enough, usually 4 gallons at a time, and it is a consistent mix. Not to mention then I don't have to do it myself.
KEEP THE FUEL VERY AIR TIGHT!!! YOU LOOSE THE EITHER IN IT, THE ENGINE WON'T RUN WORTH A DAMN!!!
Cameras and diesels are not a problem, just port the exhaust away from the camera. The extra power will come in very handy for carrying it aloft.
Dave
< Message edited by Diesel Dave-RCU -- Dec 26 2002 10:25PM >
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automotive diesel?? - 
