HI ALL,
I need a participation in making a decision, between two brand new engines
Of the 80’s------OS.max 61 VF-------AND of the 90’s---OS.max 50 SX
Power output----1.8HP (17000 rpm)--------------------1.8HP (17000 rpm)
Prop size--------1X7------11X8------------------------11X7.7-----11X8
Weight-----------18.6 oz.------------------------------13.76 oz.
(The above data given by os.)

Now which one works better for a sport model 70 in wing span
(24 oz./sq.ft) wing loading, btw (both engines set ok. In the model)
If some one had actual tachometer. Reading for any of these engines, let us see it

go 80's and put in your 70'' model the .61 vf, if you want god performances the weihgt should no exceed 3kg

Hi!
The OS VF .61!
Nothing beats cubic inches! That simple.

Regards!
Jan K
Sweden

Like Jan says,

You cannot go by published HP figures anyway. They are almost meaningless. I suppose you will be running your engine at 17,000? The engine with the larger displacement will come out ahead up in the air.

At a normal rpm, the larger engine will have more power.

Enjoy,

Jim

The biggest difference betweeen the two is the VF is rear exhaust which means that it will be mounted different on the plane. If you have a tuned pipe on hand then the VF will give you great performance. With a Macs muffled tuned pipe (NOT a silent pipe) you could get upwards of 15,000rpm with an 11x7 prop. There's no way a stock 50SX will ever turn an 11x7 that fast.

The VF's were probably the best engine OS ever produced....and you've found a NEW one?? As others have said, forget about the stated HP figures, they're worthless. That weight for the 50SX is without a muffler. Although it's not necessary to use a tuned pipe you'll certainly get a big boost in power if you do. I've only had experience with the 40VF but it's one gutsy little engine, with or without a pipe.

IRAQ,


This engine has a separate front crankcase, I believe, making it essentially a rear-exhaust derivative of the .61FSR.

This should mean the ABC is really an ABC. Not an ABN titled as an ABC, as most SF engines and their derivatives were.

I guess you have a unanimous recommendation to get the .61VF and to pass the newer .50FX.
I guess that says it all.

The FSR and its derivatives are where OS of today still get much of their good name from.

There are tach measurements for both engines in the "Tachometer Readings" forum next to this forum.

hi jack,
i didn't fined a reading for the max 61 vf
could you Fwd some think

I can't say for certain about the 61VF because I've never even seen one but the 40VF is ABN. My SR and FSR 40's are both ringed so I can't check the later liners. However, I've never heard of any peeling problems with the VF liner.

That's right, later versions of the VF series were nickel plated.

I've got two VF .61s, both acquired NIB. Inspection of the liner has revealed that they are both ABN. I also have a .46 VF, which appears to be a genuine ABC engine.

I couldn't resist starting one of the VF .61s, so I mounted it in a test stand and broke it in using typical ABC/ABN procedures. It has the best idle and transition of any engine I own at the moment and it tached (with a Macs .60 pipe) at 14,200 with an APC 11x7.

In summary: A very strong performing .61 with impeccable manners.