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Engine basics => Engine set up tips => Topic started by: Rob Killick on November 01, 2007, 07:02:58 PM
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Hi ,
I wanted to know if the OS Max FP-S , are a decent stunt engine , out of the box ?
Is there anything I can do to improve performance ?
Do they suffer from "run away" ?
Thanks
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They are fine "out of the box". There are a few things that people have done to make them last a little longer such as Super Tigre bushed conrods. We ran them for years with stock unbushed rods by adding oiling slots to the front thrust face of the rod. Other than that, just be patient with the break in. The piston will "grow" and actually tighten up the fit for about the first half hour then it will settle down. You will be alerted to the final faze by the engine starting to lean out in the middle of the bench run. It will be happily four cycling when it just decides to speed up a bit. Open the valve to settle it back down. When this stops (usually within about 5 to ten minutes of runnig time) the engine will be ready for rich flight with a gradual (over maybe five flights) approach to a good setting. As I said we flew many thousands of flights with this fine old warhorse and I don't ever remember a "run away". Have fun. DaveA
Guys, ignore this entire post or better cut and past it to a discussion of 35 - S characteristics. It was late when I read and posted this. DOH n~Sorry......
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Hi ,
I wanted to know if the OS Max FP-S , are a decent stunt engine , out of the box ?
Is there anything I can do to improve performance ?
Do they suffer from "run away" ?
Thanks
Hi Rob
They are Ok if you pay attention to fuel and do not run the stock muffler. They come with 2 sizes of venturies, use the one that is about 265 diameter. If you have the large one only you can either pick up a smaller venturie or drill and install a standard .157 diameter NVA such as a ST or PA type. You can use the stock muffler if you cut off and open up the tail cone, some use 1 extra head gasket. They usaully run well with 25% oil fuel and 10.5 to 12 diameter.4.5 to 5.5 pitch props, depends on if you FP is a 35 or a 40.
Many use a tongue muffler also.
Which FP do you have? the 25 35 or 40? and what will you use it on?
Regards
Randy
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Hi Randy ,
Thanks for the info ..
I have a .15 , .20 , .25 , .35 and two .40's .
I've flown the .15 on a Sig Ackrobat (quite fast) and the .40 , on a Sig Mustang (the Mustang was built about 15 years ago with the plastic parts) and the engine had a hard time making the plane do what it was supposed to do :)
I was thinking of usin the .35 on an Ares
Thanks again for the help
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Hi Randy ,
Thanks for the info ..
I have a .15 , .20 , .25 , .35 and two .40's .
I've flown the .15 on a Sig Ackrobat (quite fast) and the .40 , on a Sig Mustang (the Mustang was built about 15 years ago with the plastic parts) and the engine had a hard time making the plane do what it was supposed to do :)
Thanks again for the help
Hi Rob
The 15,20 and 25 many people run in a rich 2 stroke with a pitch of around 4. You may want to try that, The 35 and 40 will work in a 4-2 cycle type stunt run. Also the 40 works quite well with a 12 x 4 2 blade , running a high RPM 4/2. Again make sure you have fuel with around 25% oil. The Cyclone 11x4.5 prop is also used by many on both the 35 and 40.
REgards
Randy
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It always amazes me how cheap we are regarding the hobby we choose to relax ourselves. We always expect to buy a $70.00 engine designed to run at peak RPM for R/C folks to bore holes in the sky at max speed, to run like a stunt Fox .35 with twice the horsepower...C'mon folks it ain't gonna happen. You need to get it TUNED if you want it to run for stunt. The object is to go out there on Sunday morning, flip the prop, and have a great flight. Every flight. Every Sunday. The engines we are buying today, are not designed for us. Period. There are those folks who truly know how to mod these engines to do what we need them to do for out activity. Having worked in a shop where these engines were created for almost ten years I know the answers are not simple, despite what some folks might tell you.
The $30. to $50. invested in your engine for a professional stunt rebuild will provide you with YEARS of pleasure and enjoyment. I have watched MANY flyers go frustrated for years over poor equipment, fuels etc...(Sorry to admit it, but myself included!)
Folks, it's just not worth the $avings. That professional rebuild will cost you 1/2 a days outing on the golf course, and will provide you with 1 - 5 years of total joy.
Really! DOIT NOW.
Ward-O
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Hi Ward,
I think you must have missed my "Blind Hog and Engines" thread! LL~
Bill <><
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I've got a bunch of FP's. I used the 35 and 40 extensively for several years. I would like to say they're great stunt engines out of the box, and that they work great, etc, but I can't. They're nicely made, they make lots of power, start easily, etc. The problem is they do run away. Many times the needle could be moved one click and the engine would go from too rich to too lean. There are so many fixes for the FP, that a person can go mad trying them all and never find a solution. Sometimes they work perfectly but when they don't the troubleshooting flow chart is a mile long. 4-2-4, high rpm low pitch, stock mufflers, tongue mufflers, head gaskets, venturis, NVA's, fuel tanks, glow plugs, fuels, props, vomit.
I've also run the 15, 20, and 25. The 15 seemed to work ok but it's been quite a while since I've run it. It was too much power for the Akromaster I had it on. The 20FP is a real gem, take it out the box, set it up per the popular instructions and it's like a clock. The verdict is still out on the 25FP. Both that I've run are mildly flaky, not nearly as rock solid as the 20.
Dig around a little here and the other forums and you'll find a ton of information on the FP's.
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Dave A mentioned front oil slots in the connecting rod. I know of oil holes for lub in connecting rod bushing, not oil slots. It would help to have clarification as to depth, angle and number, and I assume these slots are on the front bearing surface to the connecting rod touching the crankshaft?
Thanks,
David
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Dave was referring to the Max-S series that used a softer aluminum connecting rod without bushings or oiling provisions. In stock form they tend to get sloppy pretty fast. The FP however has brass bushings and oiling holes.
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Hi ,
Yes, holes work well in the con rod bushings , but so will grooves .
Seeinghow , not a lot of libricant is being delivered to the bearing(s) a groove 1/2 way through the width of the bearing and two small grooves cicumferentialy from the width groove , will hold more lube and will also reduce surface area contact .
Technically , you wantthe oil to form a "wedge" in thejournal , floating the pin . The thing about castor oil , is that it flows to the hot spots .
Should be no problems with grooves .
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Dave was referring to the Max-S series that used a softer aluminum connecting rod without bushings or oiling provisions. In stock form they tend to get sloppy pretty fast. The FP however has brass bushings and oiling holes.
Thanks Andrew. I've ahhhh.... updated my original post. The groves we use in the 35 S rod are done in a cross pattern (top and bottom of the bog end hole) rotated plus and minus about the axis 25 degrees. The slots are ~0.010 deep and ~.010 wide. We do not use them on fp rods. When it comes to fp's, the only mod I hole heartedly recommend is filling the boost port passage in the c case. We use idlebar or extended tip (ala four stroke) plugs. We've been using some of the Hanger 9 Super Plugs lately and have been impressed with them. Again I will recommend against castor in this engine. We use 18% ucon.....
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What about reworking the head of the .35FP to a hemi shape?
Kim
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Come on guys! Rob, don't bother screwing around with these things. MANY people (including me) have been there, done that. Just send the engine(s) to Randy and have him tune them. I swear, you'll save yourself a whole lot of grief and have more fun flying.
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I've just measured some parts delivered by Tower in the last month. The venturi currently supplied for the FP 20/25 (OS Part No 22312000, Tower Stock No LXCW99) fits the FP40 and has a 0.26" (6.6mm) bore. This is, according to the chart Pat Johnston published in Stunt News a few years ago, ideal for the FP 40 with the standard OS needle. I also bought a couple of Tower 40 heads and I plan to try a hemi head per Bob Zambelli's drawing.
I hope this helps, Geoff
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We used to buy 25FP venturi's any time we bought a new 35 or 40FP-S. It was supposed to tame the characteristics a bit, it worked OK some of the time, but it doesn't fix the real problems with the 35/40.