O.S Max FP 40

I have an O.S.Max 40 FP. I am running a Master Airscrew 10x6 prop with a 255 castor and a 10% Nitro Sig Super fuel. What would be the idea RPM's to start with for this engine? I just put a new tank on for a longer run and am getting it all adjusted.

Hi Andrew

If the FP hasnt been reworked the 10x6 may not be the best prop for it.

Our host has a great rework service for this engine.

Thunder Tiger make an 11 inch prop which has proven to be helpful in taming it if you run it stock.

Others will no doubt be able to add more here.

A stock FP 40 will run fast pretty much no matter what you do. So put a low pitch prop on it, like the APC 11x3, and run where it's happy in a wet 2 stroke. The 10x6 prop is best suited to a lower rpm, iron pistoned engines like the Fox 35.

I use a MA 11x5 on my OS.40FP powered TF Nobler ARTF, seems to be O.K.

Check the size of your venturi. They vary a lot from the factory.
You are going to get a 1000 different sugggestions on this engine. I have had good luck with mine. I won't go into that here, b/c it would take an hour. I am in the PAMPA directory.

My os max 40 has the letters (Gt) stamped under the mounting lug. What dose that mean? Its an older engine.

>My os max 40 has the letters (Gt) stamped under the mounting
>lug. What dose that mean? Its an older engine.

It is a date or batch number, known only to the factory. Means nothing to us.

>Check the size of your venturi. They vary a lot from the
>factory.
>You are going to get a 1000 different sugggestions on this
>engine. I have had good luck with mine. I won't go into that
>here, b/c it would take an hour. I am in the PAMPA
>directory.

The "stock" venturi for stunt would be .265 with the OS needle. If you change to an ST or equivilent, then you need to up it 20 thousandths to compensate.

Again you can vary this according to conditions, muffler size, prop, etc., but if you are going to go by someone else's "stock" suggestion, this is where you need to start.

C'mon guys, let's not overcomplicate and jump right into "you gotta rework this" or "you gotta re-invent the wheel and blah-blah-blah". I'm assuming here that Andrew just needs to get some of the basics under his belt and go from there.

Just keep it simple for a while. Change only ONE thing at a time so you can learn and understand what each INDIVIDUAL change does. Assuming it's in good condition, the FP.40 in stock form will work just fine for an average sport/stunt flier.

Andrew,

What airplane do you have this engine on and how much does it weigh? Depending on the size and weight of the model, simply doing a little experimenting with different props can get you a long way. 9500 to 10,000 RPM is a good ballpark starting point for most of them. Balancing your props is something you should be doing too. It is worthwhile to get a good balancer and learn how to use it properly. I suggest the Top Flite magnetic balancer.

On basically stock FP.40's I've had good results with anything from Tornado 10x6 3-bladers, APC 10X6's, Zinger wood 11x5's and Master Airscrew 11x6's. Different airplanes like different props. A combo that works well on one model is not a guarantee on another. It takes some experimenting with each individual model to find that airplanes "happy" combo.

As you progress, and you get the engine running well and consistently, keep running it at that same setting and then start trying some different line lengths until you find yourself a comfortable lap time and also at a speed that the airplane performs well. Longer lines = longer lap times and shorter = faster etc.
Different people are comfortable at different lap times. Don't let anyone tell you it "HAS to be such and such". It may take you a while, but you'll know when you find your comfort zone.

>
> C'mon guys, let's not overcomplicate and jump right into
>"you gotta rework this" or "you gotta re-invent
>the wheel and blah-blah-blah". I'm assuming here that
>Andrew just needs to get some of the basics under his belt and
>go from there.
>
> Just keep it simple for a while. Change only ONE thing at a
>time so you can learn and understand what each INDIVIDUAL
>change does. Assuming it's in good condition, the FP.40 in
>stock form will work just fine for an average sport/stunt
>flier.
>
> Andrew,
>
> What airplane do you have this engine on and how much does it
>weigh? Depending on the size and weight of the model, simply
>doing a little experimenting with different props can get you
>a long way. 9500 to 10,000 RPM is a good ballpark starting
>point for most of them. Balancing your props is something you
>should be doing too. It is worthwhile to get a good balancer
>and learn how to use it properly. I suggest the Top Flite
>magnetic balancer.
>
> On basically stock FP.40's I've had good results with
>anything from Tornado 10x6 3-bladers, APC 10X6's, Zinger wood
>11x5's and Master Airscrew 11x6's. Different airplanes like
>different props. A combo that works well on one model is not a
>guarantee on another. It takes some experimenting with each
>individual model to find that airplanes "happy"
>combo.
>
> As you progress, and you get the engine running well and
>consistently, keep running it at that same setting and then
>start trying some different line lengths until you find
>yourself a comfortable lap time and also at a speed that the
>airplane performs well. Longer lines = longer lap times and
>shorter = faster etc.
> Different people are comfortable at different lap times.
>Don't let anyone tell you it "HAS to be such and
>such". It may take you a while, but you'll know when you
>find your comfort zone.

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Let's try again. Made a boo boo. Excellent tips, Wayne. I would have been talking till tomorrow. haha;@

This is from Dennis Moritz (sp), no credit to me. It works.

Re: OS Max FP35 vs S35
« Reply #18 on: November 25, 2010, 04:28:21 AM »
Reply with quoteQuote
In our club we setup FP35s and 40s as follows:

FP needle, 101/2x41/2 apc, free flowing exhaust (usually a tongue muffler with a lot of holes), .283 venturi, one or two extra head gaskets, Enya #3 plug, or Thunderbolt RC, Powermaster 22%(50/50) 5%. Needle is set to run a medium 2 stroke in flight which will break to a hard 2 stroke in maneuvers. If it take about 4.5 ounces of fuel to do the pattern, you're in the ball park. Sufficient fuel needs to be run through the engine to keep it cool and controllable. Or so we theorize. If the break is too hard an extra head gasket or two, usually solves the issue. Please note that head gaskets vary. Stock OS gaskets are .015, aftermarket gaskets from Leonard Neuman, RSM (I believe) or Tower, if you can find them, run .010. 2 OS means 3 Tower. Buy the gaskets from Leonard, very reasonable cost. Many many times we have found that a balky runaway engine is caused by the usual gremlins: clogged filter, leaky tank (even a pinhole leak raises havoc with uniflo), airplane vibration, poor choice of fuel, worn plug or wrong plug, venturi seal or back plate leak, worn front bushing, in other words the setup works when the plumbing etc. is as it should be. Vibration problems plague profiles, of course, and can be a factor in full fues planes as well. A solid front end is essential, it seems to me, to establishing a reliable and useful tune.

Needle valve adjustment can be critical and sensitive. A click or two either way can mean the difference between usable, predictable power, and over lean jet speed. These engines need to be tuned for performance in flight. Ground setting may or may not be an accurate predictor of in flight engine run. This is especially true on profiles, since vibe issues are common. If engine runs too rich when flying I add a click or two next flight. If too lean, the opposite. It usually works out better, when tuning a new engine/plane combo, to start with an overly rich setting gradually leaning a click or two each flight. The sweet spot may be narrow. Solid front end planes tends to provide more latitude in adjusting for the sweet spot.

Tower 40s are handled similarly and perform similarly in my experience. The Tower 40 is a near FP clone. The cylinder is chrome plated vs. nickel plated. The head appears to have deeper fining and the combustion chamber looks a bit more shallow (or visa/versa, I forget.) When tuned correctly we've found FPs to be powerful effective stunt power. Members have used them successfully in Advanced Pampa and Expert profile at local contests and Brodak. So far FPs and Towers with re-timed sleeves, that we've observed, are down on power. I have seen a Byron Barker modded engine that ran well. It's my understanding that BB does not re-time the engines. Hemi heads reduce the squish band and lower compression. I've seen them work. It's been our experience that adding head gaskets produces a similar effect while allowing for flexible adjustment.

Stock FP-.40 will run away after it gets warmed up. Send it to Leonard and get it retimed. Save fuel and buying all kinds of props and plugs . 11/5 retimed and good place to start. I have had many FP-.40's and all ran away till fixed. Dan

Yupper....
Though the 10.5X4.5 APC tames them a whole bunch, they tend to run away if over pitched.......
See Ya

Peabody

www.gscb.us / www.richpeabody.com

I keep hearing people say that they run away, but I've never once had that problem with FP's. Right along with the LA series engines, the FP's are the most user friendly two-strokes I've ever used.

On the other hand, I have always had that problem with the .35-S.

OS Max .35S fine engine/ FP-.35-.40 nice when retimed. Some are different as production moved along. Ask Leonard he works on them or did. I did have one .40 that ran pretty good stock. Dan