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1/2A Diesel Engines?

Old 07-21-2006, 01:50 PM
  #51  
lildiesel
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Default RE: 1/2A Diesel Engines?

A small caveat on diesel conversions. From observation and personal experience a lot of failures with conversions stem from running lean and overcompressed. I think this can be attributed to modelers with lots of glow experience tuning a converted engine with all their notions based on glow performance -- ie high compression and high rpms are good.

If a modeler new to diesels and runnning a conversion can concentrate on running a bit undercompressed and a bit on the rich side after starting a lot of conversion failures can be avoided. Using a prop that is 1 or 2 inches greater in diameter than the recommended size for glow is a good place to start, since it keeps the rpms down. Diesels are happy with a big prop, lower rpms, and slightly undercompressed and rich settings. Think about running a Cox .020 conversion with a wooden 6x3. An .049 conversion with an 7x4. An .09 conversion with a 9x3.

Diesels are weirdly different until you get to love them.

Now, back to the bench for me -- I'm in series production of HLGs for some of the kids in the neighborhood. Our own Flugtag without the Redbull and vodka.
Old 07-21-2006, 09:25 PM
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efish
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Default RE: 1/2A Diesel Engines?

Thanks.

Just tracked down a NIB Enya 06 IID TV so I'll probably start with that. Bringing in a conversion head of any sort will cost about half the price of the Enya, so I guess I might as well start with a purpose designed diesel.

From what I gather, the main pointers are to run rich, run overcompressed, use an appropriate prop and beware of high torque starters. For my glow engines, I like spring starters a lot, but they're hard to find locally. So I generally either hand flick or run a normal starter off an older 3S lipo pack with a normal cup - the cup will just slip on the prop if the engine is flooded.

Thanks everyone.
Old 07-21-2006, 10:21 PM
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Jim Thomerson
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Default RE: 1/2A Diesel Engines?

You want to run a diesel as lean and undercompressed as it likes. Overcompressed is how you break engines. Rich is like overcompressed. You may have to start the engine rich and overcompressed, but, as it warms up, back off the compression and it will speed up, then lean it a little and it will speed up, now try backing off the compression a little more. etc. etc. Once you get it where you want it leave it alone as much as you can and use your starter.
Old 07-21-2006, 11:01 PM
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Default RE: 1/2A Diesel Engines?

About this conversion business. Had an interesting experience this evening. I took out my .074 powered Mini-Sport to test various turbo button designs on glow. At the field I swapped out the 8 X 4 prop for a 7 X 4. I took off the diesel head and installed one of the turbo buttons. Then I filled up the tank, primed into the intake and lit it off with the starter. Heres' the rub. I didn't have to change the high speed OR the low speed mixture. With the switch from diesel to glow, the engine never missed a beat. I DID tweak both needles in and out just to be sure and sure enough, the glow setting was exactly the same as the diesel setting. The glow fuel was 25% Cool Power and the diesel fuel was 40/40/20 with Amsoil cetane booster.

This brings to mind that I did a diesel to glow conversion on a Mills for Tom Anderson nearly ten years ago. This was after I installed an adjustable airbleed throttle, I THINK it was a from Wasp .06. Anyway, that engine ran so sweet, started sooo easily and throttled beautifully as a glow engine. I used a Cox glow head for the conversion and the compression ratio was guessed at. Using the same prop, I believe I got the same top end, on 25% Sig all castor. Sacrilege, I know but I DO have that PAW sitting in the corner that's now got me thinking. What with the ruggedness of diesel engines, a glow conversion would likely last till Armageddon.
Old 07-21-2006, 11:56 PM
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efish
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Default RE: 1/2A Diesel Engines?

Whoops, sorry, meant under compressed. Thanks George.
Old 07-22-2006, 07:23 AM
  #56  
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Default RE: 1/2A Diesel Engines?

Issues with 1/2A diesel conversions for me has been fuel tubing, especially in the tank for the clunk. Stock neoprene tubing is too stiff for the clunk in small tanks. In many cases, this is not a big deal, diesels seem to be able to run on fumes and if you go gear to the sky for a bit, no harm done, the engine might burp and just keep running. However, one of the deals with running diesel is to NOT let too much fuel get into the engine when starting, hydraulic lock and all.

Sucking fuel up the line while choking is the way but how on earth can you tell when the fuel is up to the carb and no more than that?

I wish I could remember/find the individual who gave us this tip but he tipped us off to the fact that the SILICONE tubing from Texas Timers resists diesel fuel amazingly well.

So, I just had to try it, got some and did a soak test for three days. The jar was not dead nuts airtight and all of the ether is now gone but aside from a very small amount of swelling, the tubing did well. In fact, after sitting on the bench overnight, the swelling is gone and the tubing looks new.

The soaked tubing has a faint, pink tint to it from the Klotz castor I use.

This is great news, now I can plumb tanks for my TD .010 and .020 and do diesel conversions for them. Yeah, I know I'll break cranks but I WANT to.

The tubing that TT has, even the large is a BIT small for 1/2A but I think it'll do. The ID is correct the only issue is to take more care not to kink the lines. Otherwise, IDEAL for clunks in small tanks.
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Old 07-24-2006, 12:55 AM
  #57  
efish
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Default RE: 1/2A Diesel Engines?

Hi guys, thought I had everything settled, but I need more help!

Went down to the shop today to buy the enya 06 IID and the 11CXD. Turns out the 06 IID is out of stock (they said they had 2 last friday!). Got a tip off and found that the neighbouring shop has an MVVS .25 diesel for sale at about 30% less than the Enya!!

Only problem with the MVVS is that it doesn't come with a muffler. The exhaust port does lok about the same as a 1/10 scale car engine though. Anyone tried installing a car tuned pipe system? its either that or a car header coupled to a Bolly Super pipe, I think. I understand diesels don't really respond to back pressure like 2 stroke glow engines, but this seems to be the only way forward as it does not seem possible to get an MVVS muffler locally. Would be pretty cool to route the tuned pipe through the fuselage like they do on the big pattern planes?

Thanks!
Old 07-24-2006, 01:43 AM
  #58  
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Default RE: 1/2A Diesel Engines?

Wise choice buying the MVVS 2.5cc diesel engine ..... this is a fantastic little diesel engine. If you decide to run it in the rear exhaust mode, you can fairly easily build your own muffler from an empty 'mousse can' or an empty 'butane-gas' lighter fuel can.
Old 07-24-2006, 07:24 AM
  #59  
efish
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Default RE: 1/2A Diesel Engines?

Thanks, injunnut. Hadn't thought of a mouse can muffler for the engine, but you're right - there's no reasn why it wouldn't work. Doubt it will give the RPM boost that it does on the glow engines, though.
Old 07-24-2006, 10:38 PM
  #60  
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Default RE: 1/2A Diesel Engines?


ORIGINAL: efish

Thanks, injunnut. Hadn't thought of a mouse can muffler for the engine, but you're right - there's no reasn why it wouldn't work. Doubt it will give the RPM boost that it does on the glow engines, though.

I agree, likely not ...... but you can probably get away with using a much smaller diameter muffler can? All you are trying to do is 'muffle' the engine, right? Have you picked up the MVVS 2.5 yet ..... might I be so bold as to ask, how $$much$$? I have messed with a lot of diesel and diesel conversion motors over the years ..... the MVVS 2.5cc is the 'creme de la creme' of the entire lot by a fair margin! Mine loves Davis Diesel fuel and a 10 x 3 APC prop.
Old 07-25-2006, 12:11 AM
  #61  
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Default RE: 1/2A Diesel Engines?

Hi injunnut - yes, I would really be trying just to muffle the engine; saw a shop with 15 class tune pipes going for 40% less so I got to thinking that a black tuned pipe would look pretty cool! Have more or less decided to put the engine on a 3DP Mini 3D plane as I figure the wing area of the plane would go help with the weight of the engine, plus a big prop going slow would be great for 3D!

Anyhow, should be picking up the engine this week and blowing my "plane budget" for the month! Costwise is about $80 USD equivalent - is that a good price?
Old 07-25-2006, 12:44 AM
  #62  
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Default RE: 1/2A Diesel Engines?

>Costwise is about $80 USD equivalent - is that a good price?<

Yes, I think that is a very good price, especially considering that there are none to be had here in the States, well, not as they once were anyhow! Carlson Engine Imports finally did get a few in a while back ..... he wanted an even One Hundred Dollars for the engine NIB with no muffler. Are you getting the latest version with the lovely blue anodized head and prop drive along with the metal (not plastic) backplate? See photo.

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Old 07-25-2006, 01:08 AM
  #63  
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Default RE: 1/2A Diesel Engines?

Well, I can remember the blue anodised head and prop driver, but I'm not sure about the backplate. Will have a look at *my* new engine tommorrow [>:] and let you know!

Thanks.
Old 07-25-2006, 01:24 AM
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Default RE: 1/2A Diesel Engines?


ORIGINAL: injunnut1


ORIGINAL: efish

Thanks, injunnut. Hadn't thought of a mouse can muffler for the engine, but you're right - there's no reasn why it wouldn't work. Doubt it will give the RPM boost that it does on the glow engines, though.

I agree, likely not ...... but you can probably get away with using a much smaller diameter muffler can? All you are trying to do is 'muffle' the engine, right? Have you picked up the MVVS 2.5 yet ..... might I be so bold as to ask, how $$much$$? I have messed with a lot of diesel and diesel conversion motors over the years ..... the MVVS 2.5cc is the 'creme de la creme' of the entire lot by a fair margin! Mine loves Davis Diesel fuel and a 10 x 3 APC prop.

MVVS 2.5,, that's a .15, isn't it? What's the top end on the APC 10 X 3?
Old 07-25-2006, 01:31 AM
  #65  
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Default RE: 1/2A Diesel Engines?

Andy,
The only figure I have for the MVVS15 is :- 9 x 4 APC 13,100
Stewart
Old 07-25-2006, 01:57 AM
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Default RE: 1/2A Diesel Engines?

Thanks, Stewart,

Gonna see if I've got that prop on hand.
Old 07-25-2006, 11:01 PM
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Default RE: 1/2A Diesel Engines?

>MVVS 2.5,, that's a .15, isn't it? What's the top end on the APC 10 X 3?<

As near as I can remember it turned in the mid 15,000 range, this open face (no muffler or pipe) during break-in. But I am only going by memory, so I could be off? Yes, it is a .15 cu.in. size engine.

Old 07-26-2006, 01:09 AM
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Default RE: 1/2A Diesel Engines?

OK, got my new engine... can anyone recommend a good breakin prop for the MVVS .15 diesel?
Old 07-26-2006, 04:07 AM
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injunnut1
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Default RE: 1/2A Diesel Engines?

The 10 - 3 APC prop is ideal for break-in of the MVVS 2.5cc engine ..... ideally you want a relatively big diameter prop for easy starting and flywheel effect and one of low pitch or LIGHT Load on the engine. Ideally (IMHO) an 11 - 2 prop would be even better for break-in on this engine, but there are none that I know of?


ORIGINAL: efish

OK, got my new engine... can anyone recommend a good breakin prop for the MVVS .15 diesel?
Old 07-26-2006, 04:50 AM
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Default RE: 1/2A Diesel Engines?

A 10 x 4" wood zinger is my choice, wood doesnt have the razor edges of the APC prop.
Stewart
Old 07-26-2006, 03:51 PM
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Jim Thomerson
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Default RE: 1/2A Diesel Engines?

I posted some extracts from the Aeromodeller review of the MVVS 2.5 cc diesel on the diesel forum. It is a screamer, not a lugger. I don't recall if they tried a 10 inch prop.

Here it is.
There is a review of the MVVS 2.5 in the Aug 1997 Aeromodeller, pgs 38-39. There is an offhand comment that it will turn a 10 x 4 at 10,000, so I would guess it will turn a 10 x 3 at around 11,000. Starting is excellent, used D2000 fuel, choke the venturi and flick. Started on third flick. Goes dead if flooded. (True of diesels in general.) Thats the good news. The bad news is that it is not designed for your application. Peak torque is at 17,000, peak HP at 20,000. Peak HP is 0.56, HP at 11,000 is @0.30. It is a high RPM engine, not a slogger. Even so, I would expect the prop to unload more in the air and maybe make the engine happier. Just have to try it and see if you can get it to go consistant enough for your needs. A review of the ST G20-15 diesel says 10,300 with at topflite 10 x 3.5 nylon prop. So we may be low on the RPM figures for the MVVS with a 10 x 3.
Old 07-26-2006, 07:18 PM
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Default RE: 1/2A Diesel Engines?

My MVVS .15 is quite happy with 9X3,9X4,
8X5,8X6,8X4,7X6 and does pretty well on
8X6 3 blade.
Old 07-26-2006, 07:43 PM
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Default RE: 1/2A Diesel Engines?

Thanks for the info guys. Will probably start with a 10 x 3 to break in and then play around with different props after that to see where that takes me. Gotta track down some fuel and build the plane first (presently 3rd in line on my building table) though.
Old 07-26-2006, 10:19 PM
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Default RE: 1/2A Diesel Engines?

efish,
You are making the right choice for break-in prop ...... but please DO thoroughly de-burr before using any plastic, nylon, glass, composite type props (and wood too) that you might decide to use. And DO Have Fun!!!!!


ORIGINAL: efish

Thanks for the info guys. Will probably start with a 10 x 3 to break in and then play around with different props after that to see where that takes me. Gotta track down some fuel and build the plane first (presently 3rd in line on my building table) though.
Old 07-26-2006, 10:31 PM
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Default RE: 1/2A Diesel Engines?


ORIGINAL: injunnut1

efish,
You are making the right choice for break-in prop ...... but please DO thoroughly de-burr before using any plastic, nylon, glass, composite type props (and wood too) that you might decide to use. And DO Have Fun!!!!!


ORIGINAL: efish

Thanks for the info guys. Will probably start with a 10 x 3 to break in and then play around with different props after that to see where that takes me. Gotta track down some fuel and build the plane first (presently 3rd in line on my building table) though.

And balance it !!

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