Author Topic: 40 FP runaway (Read 4828 times)

Ironbomb · « **on:** February 25, 2006, 06:45:12 PM »

I put my profile cardinal up l couple weeks ago, and had some good flights, but, the engine went lean about at 1/2 tank of fuel. My lap time went from about 5.2 to 4.8 or so. ( it was hard to get an accuate time while flying).

Is this the much talked about "runaway" FP's are noted for?

tank is a 4.5oz profile wedge/uniflow.

1 headshim installed now, thickness unknown.

same problem with Powermaster 15/23 and Cooper 5/23

here is a pic of my engine set up. the tube under the tank is my overflow, and is in the flight position. I find it easier to plug the line like this than carry a plug and set it down and try to find it again.

Hit me back with questions, cause I am guessing more info will be needed to help get this sorted out.

thnaks gents

Greg

Bill Little · « **Reply #1 on:** February 25, 2006, 09:53:43 PM »

Yep, that is a runaway. Only going to about 4.8 though is not real bad for what I have seen!

peabody · « **Reply #2 on:** February 26, 2006, 06:24:32 AM »

While there are a bunch that swear that FP's don't "run away", there are several noted flyers that attest that they do, along with a whole passel of folks that have created or bolstered businesses based upon fixing that "run away"

I have used engines modified by several of these gurus and they all cure the problem some. Some do a better job than others and my favorite is the Randy Smith ABC set up, where he installs a new, custom timed sleeve fitted with a new piston.....
Another key that I have found is to run a flat prop...4 pitch, or a "magic" prop that we have found is a 10 1/2 X 4 1/2 APC....
The dreaded run away gets worse with temperature increases.
The LA 40 is an entirely different animal..and I believe that I might just put an FP "on the Bay" and spend the $60 on an LA ....
Hope this helps.

Ironbomb · « **Reply #3 on:** February 26, 2006, 08:45:11 AM »

Hi Rich, I just read Louis Rankin's post on his ST51 problem. It sounds like he has a runaway problem too. I read all the things he did to try to fix it. I have had no time for that many flights. I see where I must go to fix mine then.

I also thoght about your Ebay idea. I hate the thought of selling an engine, so If I dont get it worked out, I'll put it away till later.

I want to have a good engine for the online build project, so I may just go with the Brodak 40 I have.

Greg

peabody · « **Reply #4 on:** February 26, 2006, 08:54:40 AM »

Greg:
The "magic" 10 1/2 X 4 1/2 APC works very, very well with a Brodak 40 as well....
I hate to see guys chasing their tail trying to get engine runs when quality stick time is so much more productive...

Expecting what is essentially an RC motor to work satisfactorily is not going to lead to top performance (yes, I know about Mike Palko...the kid is, like 20, has reflexes that most only wish for......it's him and not the powerplant, believe me.

I also believe that most RC motors used in controline can be tamed quite a bit by affixing a flat prop....4 pitch stuff....

I also believe that air temperature and humidity contribute HUGELY to this, and that those that do their engine experiments in the winter are really masking problems...and that on a HHH day (remember those?_, a plane/engine combo that "runs away by a 1/2 second a lap might see such increases as two full seconds...speed racer stuff.....

Bill Little · « **Reply #5 on:** February 26, 2006, 09:10:37 AM »

Hi Rich,
I think you're somewhat right about the "weather" conditions. A good day in the summer here is when the heat index is below 100. I have seen the runaway where the plane has dropped well below a second on lap times.
Flat pitch does help because the engine is operating at a higher rpm, much closer to its power curve. Then it can't rev much more. IIRC, it usually occurs around the square 8's. Must be a heat buildup or something. Randy could tell us over on the "engine" area.

Ironbomb · « **Reply #6 on:** February 26, 2006, 10:06:27 AM »

I guess I shoulda mentioned that the prop I was using is the APC 11.5x4

This prop works wonders on my 40LA equiped airplanes.

I will try a smaller diameter prop when the weather permits. If its tame-able, I'll stick with it. I didnt know it was an RC engine gone over to C/L. I just liked the power and the growl.

So in cooler temps the runaway will not be as pronounced as in higher temp and humidity?

More time needs to be spent with this engine I know.

thanks heaps guys

Greg

Bill Mitchell · « **Reply #7 on:** February 26, 2006, 02:48:19 PM »

Hi Greg,

You didn't mention whether this happened once or every time at about 1/2 a tank. If you have a leak letting air into your fuel tank it will act exactly like that. Metal tanks are notorious for leaking around the end caps, back seam and tubes. The best way to test them is not under pressure, but to see if they will hold a partial vacuum. I use a fuel bulb. Just squeeze and leave it attached. If the bulb doesn't remain collapsed you have a leak. Some leaks won't show up pressurizing the tank because the pressure seals the leak, which is why I went to the fuel bulb test.

BTW, runaway is typically caused by heat. Under maneuvering loads the engine heats up then speeds up, much more than normal and will usually return to normal speed after several level laps. Smaller props help because they don't load the engine as much and allow the engine to run cooler. Unless your airplane is very light, you may be running too much too much prop for this engine. Look at the post about cutting down props.

Dennis Moritz · « **Reply #8 on:** February 27, 2006, 08:38:14 AM »

We've been through this many times. One extra head gasket, large venturi (.283), free flow muffler, either stock muffler opened up or tongue muffle with plenty of holes, 10 1/2/x 4 1/2 apc powermaster 22% (fifty/fifty) 5%. Muffler pressure, no uniflow. This setup works for Philly Flyers real well. Sometimes a second head gasket is needed. A small venturi or an overly restrictive muffler will cause the engine to heat up and runaway. The engine need lots of fuel running through to keep it cool. If you're doing the pattern on less than 4.5 ounces of fuel, could be the venturi is too small or muffler too restrictive. About ten of these set ups are being used by Philly flyers. We like them. Lots of power, 2x2 break. See if this set up works before you ebay. Or send the motor here.

Dennis

Ironbomb · « **Reply #9 on:** February 27, 2006, 09:00:08 AM »

I did not mention if it picked up rpm everytime. It did at half tank, which made me think "airleak", I pulled the tank, and pressureized it under water, no bubbles. The Vacuum check is something I never thought of before, I'll check it out. It may be the tank, I replumbed it to fit the plane.

I was confused cause the first couple times I flew the plane, it seemed fine, just the lean at the end. MAybe a bit too soon before the end of the run, but I was done with the pattern by then. I needled it rich as I flew it more, and it still went lean toward the last half of the tank, and ran like that the remainder of the flight, but with no lean sag.

I will measure the venturi

I looked at the muffler holes, (toungue muffle installed since the photo) and they are not diminished in diameter. I may try the stock muffler.

I am writing this stuff down, and I'll try all the suggested setups I can, thanks much Bill and Dennis and of course, you to Rich

More when I can get a flight in

Greg

Andrew Hathaway · « **Reply #10 on:** February 27, 2006, 09:22:45 AM »

There's no easy or politically correct way I can say this without ruffling anyones feathers...

I've had a lot of experience with 35-40FP's on profiles and on full fuse planes, and in the end it was more fun to run a Fox 35 and deal with less power then trying to fix the run away problem. Had lots of good luck with the FP's, but also lost enough pattern points that I'll probably never build another competition plane around that engine. There are too many other good engines that don't run away to waste time rolling the dice with a 40FP. I tried the 40LA also, and it seems like a cheap clone of the FP that exhibits the same problems with new ones thrown in for fun (leaking backplates, remote needles, etc etc etc).

Dennis Moritz · « **Reply #11 on:** February 27, 2006, 10:34:26 AM »

The tongue muffler looks too restrictive. Add holes or enlarge existing holes. Stock mufflers usually need to be opened up. Actually drilling out to the outside diameter of the tip pipe (eliminating the tip pipe) often works. Or secondary holes can be drilled around the end pipe, in the muffler body. The resulting fp40 is in our opinion a more powerful engine than an LA. (Also has more headbolts and nifty snob appeal-- can't buy one off the shelf.) Blocking the boost port takes an edge off power, I rather like the nasty edge. Have you tried tilting the rear of the tank out about an eight of inch? Might move the lean part of the flight closer to the tank run out. If you're completing the pattern and not running over, seems like you're close to getting sorted out. A mild boost in the overheads could be advantageous.

RandySmith · « **Reply #12 on:** February 27, 2006, 02:47:04 PM »

HI Greg

Many things that can cause that, but I wanted to ask if you had tried another Tank?
Many times I have seen tanks with cranks in the fuel pick up or uniflow line, That will make the engine act just as your stating.
It maybe worth while to at least try another tank

Regards
Randy

Steve Helmick · « **Reply #13 on:** February 27, 2006, 08:04:24 PM »

In any case (no pun intended), why sell a good .40FP (or Tower .40, etc.) to buy a .40LA? Plug the boost port and you have the same thing, a bit lighter and a good metal backplate. It's not that hard to do, and gives it much better manners.

Steve

Ironbomb · « **Reply #14 on:** February 28, 2006, 06:52:25 AM »

Well Randy, I have not tried another tank yet. I have only this one set up at the moment. I will check it out.

I know this stuff has been covered before, I cant find the old posts, so thanks for the input you guys.

Steve, I did not think of that, I stuffed a Fox .35, and cured the burp, so if doing the same to my FP is needed, I can do that. I will save stuffing as a last resort. What I dont want to do is waste flying time on an engine that needs more care than I have time to give.

again, thanks

Greg

catdaddy · « **Reply #15 on:** February 28, 2006, 07:07:03 PM »

Quote from: Ironbomb on February 28, 2006, 06:52:25 AM

Well Randy, I have not tried another tank yet. I have only this one set up at the moment. I will check it out.

I know this stuff has been covered before, I cant find the old posts, so thanks for the input you guys.

Steve, I did not think of that, I stuffed a Fox .35, and cured the burp, so if doing the same to my FP is needed, I can do that. I will save stuffing as a last resort. What I dont want to do is waste flying time on an engine that needs more care than I have time to give.

again, thanks

Greg

Put a Bruline green filter over the venturi. Here in Tulsa we Shim the head and choke down the venturi and they generally behave themselves on 10-22 running an 11-4 prop. I have one that is one of my favorite engines.

phil c · « **Reply #16 on:** March 01, 2006, 07:43:05 AM »

You also might want to think about how old the plane is. Profile noses are notorious for getting soft and vibrating as they age. The Cardinals in our club seem especially prone to this. There isn't much holding the front end onto the wing. The vibration can hit resonant frequencies with certain prop/rpm combinations and cause the engine run to behave erratically. The key is the fuel line to the needle valve. The fuel should flow through with no bubbles. If the fuel is bubble-free on the ground it usually stays that way after launch. Any visible wiggling of the nose during starting or ground running is a bad sign.

In this case, as the fuel is used the res frequency may change and lean the run out.

George Waters · « **Reply #17 on:** March 03, 2006, 06:17:51 AM »

I've had this problem once where at 1/2 tank the lap times went from 5.1 down to4.1 for the rest of the flight. What I found was that the fuel line had a crack in it about 1/2 way down it's length. I put in anew fuel tube problem solved. Hope this helps. George

Scott Dinger · « **Reply #18 on:** March 03, 2006, 08:44:25 AM »

Greg, I have an FP that NEVER runs away. Fuel-5 or 10 nitro[whatever mood Im in when I blend] 11/11 Klotz syn & Klotz Castor, Bolly clubman 10.5x5 [you can gut these from Randy Smith] and a cool running hyflo muffler. I'm flying a Caviler. I get asked all the time ''what engine do you have in that plane?

The prop is the only one I would EVER run on that engine-cause they allways work. It may look like an APC but it is totally different. Contest results speak for themselves. I placed 13 & VSC out of 70+ flyer's in classic with a$4.25 dollar prop. Scott Dinger

Ironbomb · « **Reply #19 on:** March 03, 2006, 11:17:28 PM »

Thanks for the great info you guys, I am writing this stuff down so I can track what results I get with each change.

I will order a Bru line filter, and some props form Randy,

and yes, Phil, I know the nose section is solid, the fueselage is new build, and pretty heavy. I think the fues weight alone came out at over 16oz, empty. 3/32 ply doublers, heavy maple bearers, some petrified balsa wood for the shape. ouch, but it does move, and suprisingly, can corner. Still, not a comp plane.

Greg

Mike Clark · « **Reply #20 on:** March 13, 2006, 07:24:17 AM »

What modifications have been performed on your FP40?

Blocking the boost port alone will not keep your engine from running away.
If you are using a box stock FP40, then you will need to either choke down the engine with a smaller venturi or use a more restrictive exhaust flow muffler.

I own FP40's from Randy Smith, Leonard Neumann, Tom Dixon and Bill Norman. All of these engines will run away if set up poorly by the flyer. Don't be afraid of going outside the box when approaching a fix for these engines. There is no sure fire or silver bullet solution to all problems.

I had one FP40 engine that was heads & heels above the rest in power. I could not find a decent solution to allow this engine to be used. Hell it had a mind of it's own! Runaway, choking, burping and flat crapping out. I picked a prop that I had not used in a long time a Rev Up 12/5 and install it. The engine seemed to like it but the power was GONE! I up the RPM to 8000 at take off and the engine improved greatly. I finally set the take off RPM between 8200- 8600 and Holy Cow the power came back.

In my use of these engines, I'll block the boost port with JB weld, use the original venturi, add a tongue muffler on pressure with a uniflow tank, Brodak or GRW. Fuel; Sig 5/22 Champion (Red)

Now load the motor with a prop and in my case that will be a 12/4.5 to 12/5.5.
Take off RPM should be around 8200 - 8600 RPM. I use a 12/5 or 12/6 Rev Up in almost all of my applications, in others I'll use a 12/4, 12/5 or 12/6 Zinger.

All of my FP & LA engines fly a 4/2 break without fail! No runaway and no wind up.
Lap time is 5.5 to 5.7. no rocket ships here.

Mike Clark
MikeC
FP40

Wynn Robins · « **Reply #21 on:** March 23, 2006, 04:34:34 PM »

dunno how many times I have told you to use a clunk tank, sintered brass clunk. and muffler pressure.

you still refuse to listen......I just dont get it.......... $:-\$

Bill Little · « **Reply #22 on:** March 24, 2006, 07:59:35 AM »

Just a point about different engines that are not "stunt specific".
A proven set up that works on one of these engines may or may not work in another part of the planet. What works in NC might not work in Colorado, and vice versa.
I tell all the "newbies" that ask me to get a stunt dedicated engine as soon as they can. The Magnum 36XL II square head works in most areas it seems as well as the 46LA. Seen varying results with the 40LA and other R/C engines that have not been reworked. The 20FP BBTU seems to work everywhere in the smaller planes. These engines do exhibit a different runstyle, however, from a stunt dedicated engine in some ways.
With the 40FP, stock, you may or may not get it to work consistently. This is proven through the numerous posts on the various forums. Even when using "proven set ups". There is enough manufacturing variances to make each engine just a little bit different.
I am not saying that the set ups don't work great for those people in their areas. Just that they may not work in another area.
An reworked engine from any of the noted engine guys is the best starting point for anyone.

Ron Varnas · « **Reply #23 on:** March 24, 2006, 04:10:49 PM »

I agree with Bill on the current available out of the box motors and using
the rework guys for FP's etc.
I've read a bit about the FP setups for a while, and doing some quick maths
at the end of the day (presuming) one picks up a Early iron version on the bay
or wherever.......you've got to add "all" the extras, NVA +Venturi+ Tounge or
Tube muffler+ Rework ??$$..........all this maybe passes a NIB B40 (if you like'em)
& very close to a Double Star 40 (which is totally Stunt dedicated) $:-\$

Bill Little · « **Reply #24 on:** March 24, 2006, 09:38:49 PM »

Hi Ron,
Tom Dixon sent me the initial correspondence that he had with the guys in the Ukraine about making the Double Star 40. This was back whe I was doing the Products column for Stunt News. The desire was to build a 40 size engine in the Fox 35 case, same weight, ABC construction. A great idea to boost the Classic ships tha twere powered originally with the Fox 35. They DS as it comes out of the box is set up for FAI (no nitro) fuel. Tom's suggestions for using nitro is to atart with 3 shims. I also have found that openimg the venturi up a little at the time will really bring some extra power out of the DS 40. The choke area is very small in its "stock" configuration. Mine run a perfect 4-2 when set up this way on 5% to !0% nitro.