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ASP .46A Mk1 Diesel Conversion

Old 10-29-2011, 11:30 PM
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fiery
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Default ASP .46A Mk1 Diesel Conversion

Some years ago I acquired a NIB ASP .46A (first series) at modest cost from someone exiting the hobby. It sat in its box pretty much forgotten.

I recently re-found my ASP .46A Diesel Conversion head I purchased in the early 90's.

Having the engine on hand, I decided to try it out.

Unfortunately I forgot to take my camera to the field. So there are (as yet) no "in action" photo's. I will run it again in a few weeks with an alternate carb installed and take some, for posting on this thread.

The ASP conversion heads were sold for a short time in Australia with ASP .32 and .46 engines as an "optional extra". For the full story refer to my ASP .32A Diesel Conversion thread in this forum.

The .46 diesel conversion head differs in cosmetic detail from the conversion head supplied for the ASP .32A. It has no cooling fins. Apart from that, it is a similar set up in all material respects. Push-pull actuation of a brass contra piston situated in the head with a lapped fit (no "O" ring seal). Quality workmanship and materials. As with the .32 head I tested, there is very little blow by past the contra piston.

The photographs show a blackened combustion surface on the contra piston, and the heads combustion chamber. The head had much use in the early 90's powering some sports ships. It suffered a few mildly over compressed runs. I like to think I am a little better at adjusting my diesels these days. Before disassembly for the photograph the engine had received 2 hours running on the bench. When running in there were no signs of distress even when optimised for top RPM's at conclusion. Exhaust was always dark honey coloured. The liner and piston crown show a nice honey colour. The bottom end was clean, apart from remnants of congealed preserving oil from factory assembly.

I used the supplied carb. It has a 7.5 mm bore. It worked well, better than expected. Throttle response being quite linear. That surprised me. I will test it again with the MVVS carb shown in the later shots. The MVVS carb has a 6.75 mm bore. We will see how it works. The proof will be once it is put to the test.

Early ASP engines received mixed reviews from users. This one has excellent compression and fits. It is built to price. Presentation is not up to "top drawer" product standards. It had the usual high speed needle valve "O" ring issue. The "O" ring is not tight on the needle body. Fuel leaks out. The problem was solved after the first session with it's removal and replacement with an alternative from my "O" ring spares collection. The new "O" ring is smaller in inner diameter, and thicker. It now seals so tight the needle could not wander even without the spring clip. The needle is in fact now quite "stiff" to turn. This will improve with use.

The mating surface of the exhaust port to the muffler is less than perfect. It will require sealing with a gasket or silicone RTV sealant if put into service. No particular drama. Most if not all engines leak at this junction.

This ASP .46 diesel spun my favourite Taipan composite "test" orange 10 x 6 prop at over just 13,000 rpm steady. This is about 800 rpm down on glow figures using my FAI (nil nitro methane) test glow fuel. These engines can deliver very good sports engine performance. It will spin an 11 x 6 prop in it's next session.

Starting could not be achieved by hand. Starts were accomplished with use of my electric starter. It wanted to be decompressed to start. Perhaps I have not yet learned what it likes for a fast hand start. That is what I like about diesels. They are idiosyncratic. What works for one diesel model engine does not necessarily apply to another. They are like the most interesting of people. You need to take time to get to know them.





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Old 10-30-2011, 03:16 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

Very nice Derek, if you have time could you also run one of those 11x7 Taipans, I want to try one on my Fox .46. Today is my mother in laws 90th birthday so we're going to my brother inlaws in Huntingtown, Md. Today is used up in other words. I noticed that the contra is a little over extended, the 11x7 and probably the 11x6 should cure that. I have an ASP 1.08 that was a gift from w8ye, I've often thought that it would make a fine Diesel. Thanks, Dave
Old 10-30-2011, 03:45 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

G'day

I had that exact combination back about 1991. I think I put a 11 x 6 on mine but it may have been a 12 x 6. I had no problems hand starting it which really surprised me at the time. The problem I had was simply that the carby was too big and it would not throttle very well. I put it in an Aeroflyte Hustler but its only flight was very short as the throttling caused problems and it stopped.

I removed the diesel conversion and ran it as a glow for a while but ended up selling it. I kept the head and eventually used it on an old Magnum 46 with a 25 size carby. That combination ran well.

Have fun with yours.

Mike in Dubbo, Oz

Old 11-06-2011, 02:05 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

Session 2; 7th November 2011. Carb ASP 7.5 mm rotor bore.

APC gf 12x6 9,500 3,300

Taipan gf 11x7 10,400 3,300

Graupner 11x6 11,500 3,300

Engine started easily, and responded well to needle and compression adjustments. Throttling good, though idle became unstable in low 3,000's. HS needle now leak free.

Photo's with APC 12x6. MVVS carb installed in first shot. No operational improvement with MVVS carb, so it's use was abandoned.
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Old 11-06-2011, 03:44 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

Thanks Derek, been busy with winterising Geri's flower beds, cutting firewood, I promised you a Fox .46 run, maybe tomorrow. I don't winterise the Harley, I ride several times during the winter. That Taipan 11x7 looks like a great choice. Great numbers.
Old 11-06-2011, 04:30 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

That is pretty neat there fiery.
My Fox .45 likes a 12x8 prop on it. It has me thinking that maybe the 11x7 and 12x6 props may be too small for your engine.

Old 11-06-2011, 04:58 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

FIERY, nice numbers. I did notice on your pix of the head quite a bit of clearance at the 2 o clock area the contra in the head has quite a gap, the O ring is doing its job but wonder how long it will hold up. I have not seen this on my Davis, AJ colholics,enya 25? Irvines , you might consider have an other
made to play it safe, I do not have any MECOAs but their pixs do not show this much either martin

NOTE JUST REREAD YOUR POST AND YOU STATED PUSH-PULL SO A DROP WOULD NOT HAPPEN, HOW EVER IF A NEW ONE MADE
YOU WOULD NOT HAVE THAT BIT OF EXTRA VOLUME PAST THE CONTRA AND MOST LIKELY CONTRA COULD BE RAISED
A BIT IT STILL SEEMS LIKE A VERY STRONG ENGINE, BIGGER PROP LOAD WOULD RAISE IT TOO
Old 11-06-2011, 09:50 PM
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Default RE: ASP .46A Mk1 Diesel Conversion

I had my ASP 32 converted by a control line speed guy that lived in Cranbourne, forgot his name.  He lowered the liner, and did the diesel conversion to the head.  I supplied and fitted an OS 1 A carby and flew it with great effect in an Ethy in Texaco back in the days when SAM 1788 flew at the Pines at Canowindra.  That engine has powered an 85% Bomber and the other one that was converted at the same time is in a 75% Dallaire.  These were good engines and I am now about to use the head as described above on an ASP 46.  
The big problem with the ASP engines that were sold in OZ were that they were built up out of bits and pieces that were "seconds" and the instructions were crap.  When I was working in SE Asia I acquired a number of ASP engines from the factory (about 100 of various sizes) and I learnt how to tune the twin needle carby which was a novelty in those days.  I set up the engines and taught the people that I sold my engines how to handle them and look after them and not one missed a beat and apart from crashes most still survive and still give good service today.   
Old 11-06-2011, 10:06 PM
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Default RE: ASP .46A Mk1 Diesel Conversion

Interesting observation FNQ Flyer. It seems I am not the only one out there with the conversion head for these engines.

Your comments on build quality back up my personal experience. My first ASP .46 was purchased in the early 1990's (with the head shown above) directly from the original importer of the engines in Australia. It had a couple of major production flaws which resulted in its service life being short. The carb was very roughly made and transition was poor. I thought I may have just been unlucky.

The example shown in the above tests was orginally sold by World Engines in the US. Overall, it is definitely superior to my earlier example. The carb works smoothly and transition seems excellent.

I am shortly to acquire a rather rare "SY" .46 branded variant of this engine from Western Australia. It will be interesting to see how it's build quality is.

I am curious to know whether the head shown fits a current production Magnum / ASP .46. Bore diameter on the head is 22.25 mm. If anyone knows the bore specs for the current version of this engine, please post them here. The head does not fit any other engine I am aware of.

EDIT

Martin, the black line you refer to on the photo of the upturned head is shadow. Look closely at the other side of the contra piston. There is no gap. The contra piston is a very tight fit in the head. I use my tommy bar adjuster on this engine to adjust compression easily. The adjuster is shown in an earlier thread:

http://www.rcuniverse.com/forum/m_10624244/tm.htm

This highly technical invention makes adjusting a larger diesel engine with a tight contra piston a breeze. Keeps fingers well out of harms way too.

Old 11-07-2011, 04:43 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

FIERY quite sure Magnum. ASP, and Jen engines from Just engine UK are all made by Sanye now, and decent quality, the Just engines 56 is now a 57 ringed along with the 37 , the 47 still ABC I have their 56 (2) converted to diesel along with the ASP 12 and 15 all great runners, I must admit that I am an Irvine freak UK made and have their 25 39, 40s, 53s I do have a 39 and Davis made only one head I think as a test for it but is hanging on to it, I cannot pry it out of his hands
note and an irvine 20 Diesel and one more 20 diesel on the way from flea bay and awaiting its grub screw (when it gets here that you kindly sent to me)
regards martin
Old 11-10-2011, 07:31 PM
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Default RE: ASP .46A Mk1 Diesel Conversion

Martin

The Irvine .39 is still available to purchase new I believe. I would love to see how it performs with a DDD head. An annular head would look great on it. Especially if anodised black, to match the finish on the JetStream carb.

Please do try to run one, and post some figures. If numbers were good, perhaps you could persuade Mr Davis to do a small run?
Old 11-11-2011, 04:34 AM
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Default RE: ASP .46A Mk1 Diesel Conversion

FIERY humm need new reading glasses the 46 head contra thing is indeed a shadow on a close look, will haul out the plane with the irvine 39 (glow)
why try Sunday , playing pharmacist today regards martin

note can run the 39 irvine as glow only do not have a diesel head for it
Old 06-30-2013, 03:00 PM
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Default RE: ASP .46A Mk1 Diesel Conversion

Acquired a couple more of these beautifully made conversion heads.

The 40 size unit was installed on a new Magnum XL 40 for testing. Main needle was very rich as engine had never been run before.

http://www.youtube.com/watch?v=U6crqP1wURE

http://www.youtube.com/watch?v=Pk8KuHNlIXM

http://www.youtube.com/watch?v=oeewmBAmIb4
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Old 06-30-2013, 07:03 PM
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Default RE: ASP .46A Mk1 Diesel Conversion


ORIGINAL: fiery

Acquired a couple more of these beautifully made conversion heads.
Where does one 'aquire' these heads?
(They do look well made.)

Old 06-30-2013, 07:53 PM
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Default RE: ASP .46A Mk1 Diesel Conversion

PM sent.

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