jstanton

My Feedback: (14)

I just aquired barely used Magnum XL 108A engine. I did not get a owners manual so I need a little help form anyone who knows something about this engine. I have 10% Omega fuel and I was wondering if that will work in this engine or sjould I go get another gallon of 5%. I also have MAS 15x6 & 14x6 props. Are they the right size or is something smaller or larger better. Soulr I start with 2 1/2 turns out on the needle like mist 2 strokes? Also the carb that came with the engine says 91 on it. Is it the right carb?[:-]

FlyingPilgrim

My Feedback: (26)

15x8 prop, 10% will be fine. Carb is probably orig, as I believe the 108 was an overbore of the original 91.

Ed_Moorman

My Feedback: (1)

I have 2 of them. The previous answer is correct, is is an enlarged version of the older .91. The newer .91XLS is in a .61 crankcase.

The Magnum 1.08 is a fine running engine if you run it right. The factory instructions are totally incorrect-it won't turn a small prop very well. It is more of a torque engine meant for big props. Consider the 1.08XL a tractor engine and the .91XLS more of a sports car engine. A 15-8 will give you good speed and a 16-6 is good for pull. I used a 16-6 on a heavy Joss Stick. On a scale Northrop A-17, pre-WW II dive bomber, and on a Beechcraft Staggerwing, I use a 15-8.

I run 10% Omega, castor blend, fuel. Like most Magnums, it should start in one back flip after a good wet prime.

jstanton

My Feedback: (14)

Ed,

Thanks for the reply. I have a MAS 15x6 prop and an APC 14x8 prop to test run it on today. I also have a MAS 16x8 I could use but it might be a little to much load on it. Do you use a starter on your 108's or do you flup start them?

jstanton

My Feedback: (14)

Test ran the magnum 108 today with a MAS 15x6 simitar prop using Omgea 10% full. I have a good idle 2300RPM and a I am getting 9000RPM on the high end. I think this engine will be perfect my great Planes Escapde 60 I have it installed on. I am looking to do the maiden flight this weekend. Here is a pick of the plane.

jstanton

My Feedback: (14)

Sorry the pic did not take. Here it is again.

DarZeelon

Jim,


I am sorry to disappoint you, but according to the [link=http://www.mvvs.nl/prop-power-calculator.xls]PropPower calculator[/link], the output your new engine is showing is barely 1.156 HP at this RPM...

Just to give you a comparison point, and OS.46AX, spinning an APC 10x6 at 14,300 RPM, on 15% nitro (that is what various tests clocked it at), is putting out an actual 1.144 HP.


Check to find what is wrong; as this much larger engine should be showing much, much more power.

It really does not matter if the power is 'sufficient' for your needs. It's still very low for this engine.

Sport_Pilot

I have an ASP .91 that will turn that prop faster than that.  Also it doesn't like 10% fuel in the summer.  I would switch to 5% and a colder plug and see if that is better.  I think that engine is good for better than 10K or at least near 10K RPM.

spaceworm

Here is a related link: http://www.rcuniverse.com/forum/m_98...tm.htm#9859862.

I have an ASP 91 that will not run right, overheats and blows plugs if run on more than 5% Nitro fuel. It is one of the original high compreresion versions, but you might try some lower nitro fuel, and check for air leaks also. Good luck.

Ed_Moorman

My Feedback: (1)

I have both the Mag .91XLS and the Mag 1.08XL. On a smaller prop the .91 will out turn the 1.08. It has been my experience with 2 1.08s that it is not a good high rpm engine.

I still recommend a 15-8 or 16-6 for it. It needs some big lumber on the front.

The ASP engines, made for the European market, may have a higher compression than the Magnums, made for US use. The higher compression works better with a lower nitro fuel, 0% or 5%. I live in Florida and use 10% all the time with no ill effects.

jstanton

My Feedback: (14)

I still have this engine running a little on the rich side and I will go out and get a APC 15x8 prop tomorrow and try it once again. Ed, I do thank you for your help with this engine and it does start very easy. What RPM readings should I see with the APC 15x8 prop? Will it still be in the 9000 range?
I will be using Omega 10% for the next couple of gallons because I already have it on hand. I will try the 5% if I can find it at my LHS. I think they only have 10% and higher nitro on hand. I don't know if they will order any 5% for just one gallon[]

spaceworm

Buy straight methanol at your local speed shop and then dilute your 10% 1 to 1 to get 5 percent nitro. Be sure then to add castor or Klotz to bring your oil up to 18 or 20 %. Works for me in my 91 and 1.08 ASP's and 90 Como, and results in cheaper fuel than buying 5% pre- mixed. Good luck and don't forget to add the extra oil.

jstanton

My Feedback: (14)

Sounds like a good thing to do. I have 1 new gallon of 10% left. If I buy 1 gallon on methanol and mix it with my 10% that should make it two gallons at 5% right. Than how much castor do I put into the 2 gallons and where do you buy castor at. Do I pick it up and the local drug store?

DarZeelon

Quote:

ORIGINAL: jstanton

I still have this engine running a little on the rich side and I will go out and get a APC 15x8 prop tomorrow and try it once again. Ed, I do thank you for your help with this engine and it does start very easy. What RPM readings should I see with the APC 15x8 prop? Will it still be in the 9000 range?
I will be using Omega 10% for the next couple of gallons because I already have it on hand. I will try the 5% if I can find it at my LHS. I think they only have 10% and higher nitro on hand. I don't know if they will order any 5% for just one gallon[]

Jim,


It probably is more than just a prop selection matter.

The ASP 1.08 is an OS1.08FSR clone and I believe it was designed to top-out at more than just 9K.

This engine is not merely an enlarged, cloned .91FSR. The .91 had a 17 mm diameter crankshaft, while the 1.08 uses a much larger 20 mm diameter crankshaft (like their current 1.20-1.60 engines).
It is a size larger than the .91 'big-block'.

It has large passages that support higher RPM and a light 15x6 prop should not really an obstacle for it. Like a 14x8, it should be spun beyond 11K!


Try loading it with a larger prop; I suggest a 16x8 of the same series (MA S-2/Scimitar).
It should spin around 9K, drawing just under 2.00 HP.


If it does not, look for possible butting of the ring ends...
It could cause overheating and make the sleeve go south very rapidly. Do use only 5% nitro fuel!
You could make your 10% nitro fuel into 5%, by mixing each gallon with 103 ounces of pure methanol and 25 ounces of castor oil (BéNOL, Bakers/SIG AA, CleanCastor - all OK).

If you obtain castor oil in the drug-store, it will likely not be degummed and will make your engine rather filthy rather fast.

NM2K

My Feedback: (14)

The Sanye 1.08 was designed to top out in the high 8k rpm range. If the engine is running at over 9k rpm, it is under propped. Stick to 5% nitro or add a head shim to stop overheating in the summer. These are great engines and no, they are not OS clones.


Ed Cregger

DarZeelon

Quote:

ORIGINAL: NM2K

The Sanye 1.08 was designed to top out in the high 8k rpm range. If the engine is running at over 9k rpm, it is under propped. Stick to 5% nitro or add a head shim to stop overheating in the summer. These are great engines and no, they are not OS clones.

Ed,


Are sure about the ASP not being cloned after the OS?

Take a look at the photos below. They have the same bore, stroke, bearings and appearance (except the carburettor and prop-driver).
They are very much clones.

goirish

I see that the lower case is different. Has a brace going from the mounting lugs to the crankcase. However, very close.

DarZeelon

Quote:

ORIGINAL: goirish

I see that the lower case is different. Has a brace going from the mounting lugs to the crankcase. However, very close.

Had it been an exact copy, I guess OS would have a legal case...

So, Sanye are careful... But if you count the cooling fins, you'll see it is the same number.

goirish

OK, you convinced me.

Lovitlots

Hi Jstanton
I have an asp108 red head. I broke the engine in on omega 10%. and ran it with an apc 15x8 prop. The engine topped out at just over 10K. I later learned that asp engines are actually built FAI fuel. I haven't tested this on the 108 yet but I did try it out on a recently bought, new asp 52. The instructions said to use 10% nitro and I did. With an apc 12x6 prop it turned around 10.3K. Then I ran a tank of my home brew FAI fuel and the same prop. Now the engine turns at 11.5K and that is still slightly rich. I think your 108 will perform better with the no nitro fuel. Play with the prop sizes on the engine as well as any other engine untill you get the best thrust performance with that engine. I've been practicing this and I'm now getting the best performance of a particular engine plane combo that I have. The rule of thumb is if you have a slow flying model go higher dia. and smaller pitch. This will give stump pulling power. If you have a high speed performer then go with a smaller dia. and high pitch. This will give you speed. Bottom line, play with the props and try different fuels to see which will give you the best performance for that particular model.

Sport_Pilot

I have the Red Head .91 and it will only run on 10% in the winter and cooler spring weather. But has more power on 5% even then. It will detonate and overheat. It was bought from Indy R/C not an Europeanversion. I think the later grey head versions tolerate higher nitro.

Sport_Pilot

Uhh, no it is more like 9K underproped when hitting over 10 K. Ed was right about the prop selection. I just forgot that the older ASP Red Head has higher compression.

DarZeelon

Ed Moorman and Hugh,


Since the ASP is a clone of the OS; and since you discuss the ASP being at its best between 8K and 9K RPM, is the OS1.08FSR also at its best in this range???

I seem to remember it being good for much higher RPM and it's rated by its manufacturer at no less than 16K...


Please explain.

jstanton

My Feedback: (14)

Thanks for all of the info guy's. You all have been a big help. I will go with a APC 15x8 prop and try to lower the Nitro to 5% on my next gallon. I have 1/2 gallon of 10% I am workiong with right now. This engine does start very easy I most say. I also what to tell you all I am using a evolution glow plug in it that my be in the wrong heat range because it says it is good for both 2 and 4 stroke engines. What OS plug is the best for this engiine and I will pick up a few of them also.

Sport_Pilot

I think the ASP 108is more of a clone of the OS .91 FSR

http://www.osengines.com/history/osm...-max-91fsr.jpg

I have been told that the 1.08 has smaller passages than the OS 1.08 and does not breath as well, thus the slower revs than the ASP .91. But Ihave never compared them side by side. I stated that the ASP and Magnum 1.08 should rev at or slightly above 9 K not 8K. But come to think there are several versions and the timing may different for each. I think there is the ASP red head, the later grey head, the Magnum 108, 108A, and possiby a 108B. There may be differances in the best prop and revs for some of these versions.