Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

tuned pipes

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Old 10-19-2006, 10:01 PM
  #1  
lbarnes
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Default tuned pipes

Trying to get my first tuned pipe working. Does anyone know of a good website for tuned pipe issues?

I have a Mecoa .46 with a macs 1140 tuned pipe and 10 x 6 prop.. stock muffler gave me 12,900 rpm, tuned pipe gave me 14,200. Nice improvement but the plane still seems to flys at the same speed. I know someone is going to say how do you know. Well I expected a big change due to the increase is rpm but level flight seemed the same and it just didnt sound like it was on the pipe.

I have some issues with the needle valve adjustment that dosent seem right but since this is my first pipe and no one at the field has used one before, I am kinda the G-pig for this project.

Some info is, I am at 11.5 inches from the glow plug to the first widest point in the pipe. I have my fuel tank pressure nipple at the widest part of the pipe.

Macs website is useless for tips or help.

Any help is apreciated.

Larry
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Old 10-20-2006, 12:27 AM
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Flyboy Dave
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Default RE: tuned pipes

Is that is an APC prop ?....If it is, you won't get many revs out of it.
At least I didn't. []

FBD.
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Old 10-20-2006, 01:03 AM
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Default RE: tuned pipes

Here's a baseline chart I use, make sure you measure from the glow plug to the widest point of the pipe as the exhaust flows (not a strait line) I normally go with the next higher pitch on the prop than I plan on using then trim the pipe a 1/4 inch at a time until there is no more rpm gain, then run the prop with a little less pitch or cut down a bit and see how it performs, if the plane has alot of drag small speed props won't pull it well
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Old 10-20-2006, 01:19 AM
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Roary m
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Default RE: tuned pipes

Two things to remember when cutting 1/4" lengths of header to get the desired top end out of the engine. The first is that the shorter the header, the sooner the engine will come onto the pipe. The second is that the shorter the header, the lower the temperament of the engine; it will be more sensitive to high end needle valve changes.
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Old 10-20-2006, 09:07 AM
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Default RE: tuned pipes

Looks like you are off to a decent start with the pipe. Pipe tuning takes a bit of understanding and practice. The easy way to attack this for a novice is by setting the pipe 'close' at a recommended length, then changing load/prop. It is far easier to change the prop, and match the load to the pipe. Gives you at least an understanding of how it works.

The Mecoa .45 is not real-agressively timed. But it runs well. You showed a pretty substantial gain on that 10x6 prop - not too bad at all !!

As for tuning, leave the length where it is now. That 11.5 should be about right for a 10x6 on a .45 size engine (target about 14,500-15000 ground rpm), but where you set the pipe depends on the plane/prop/application. You noted that your current rpm with the pipe was a bit short of this, which indicates you may have the pipe set a little short for what the engine is capable of. But here is the way to find out for sure....

Instead of cutting or adjusting the pipe, change the props to see where you are (long or short) in tuning length. Do as much as you can on the ground. Avoid getting the engine hot - if it does not sound 'good', richen it up, and shut it off. Try again.

Start with a 9x6, find the peak rpm (Briefly, then back off the needle a bit). Wait 5 minutes, reinstall the 10x6. Try again. Then see what larger props you can drum-up. Try a 10x5, 11x6, 11x7 Document each of those. If you have a 9x7 or 9x8 available, try those as well.

When you find the engine drops in rpm with the heavier prop, surges, or is difficult to needle, do not try to force the engine to run - shut it down - you have reached a point where the pipe is 'too short' for that load/rpm. You know know the limits of what your engine and pipe are capabile of, as it is currently set.

Back off one prop size - and that is what you will need to run for that pipe length.

If you find the engine runs well with the larger 11x6 or 11x7 size props, the pipe is set long (for lower rpm). If your goal is speed, you may wish to shorten the pipe system a bit and re-evaluate all of the props.

If you wish to go up in rpm, go with a smaller prop size, and shorten the pipe 1/4"
If you wish to go down in rpm, go with a larger prop size, and lengthen the pipe 1/4"

As for your aircraft speed ----- keep in mind the added drag of the pipe installation. Also, if the airframe is generally draggy, it takes a huge increase in power to generate just a little more speed. So in the case of your 2000 rpm gain, you may only see 2-3 mph speed increase with the 10x6.

Ways to experiment here, are to change from the 10x6 to a 9x7 or 9x8 for flight - helps reduce frontal-disk area, reduces drag - can increase speed at the expense of some vertical and take-off performance. Again, you have a pipe set for a target rpm. Keeping the pipe the same, select larger or smaller diameter props that result in the same ground rpm.

A good reference on tuning pipes can be found on the jett engineering website, in the Tech section. Basically this technique - select the prop size you wish to run (example, 10x6). Then install a prop one size larger (example 10x7). Start with the pipe set long. Record rpm information. Cut the header 1/4" at a time until and re-test until you seen no further gain in rpm, and the rpm falls off slightly and the engine is difficult to needle. At this point, the pipe is not 'too-short' for that test prop. But it will now be perfectly set for your intended (10x6) prop.

A key here..... you have to think up front, about what prop is best suited for your aircraft application. Using a 9x7 on a quick plane like a Shrike, Q-500 or similar is a good selection. Using a 9x7 on a .40 size Super Sportster is probably not appropriate, you would want a bit more prop diameter, and the plane is inherently slower. It is somewhat like gearing in the transmission of a car or truck.

(shortcut here - from what you have descriped - a 9x7 or 10x5 would be a starting point - get the rpm up to or above 15,000 peak, set the needle on the rich side by about 500 rpm for flight)

I hope this is helpful.
Bob
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Old 10-20-2006, 12:17 PM
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Default RE: tuned pipes

Don't forget to richen the low needle and high needle as needed. The pipe won't work properly if it can't get the extra fuel to turn the extra rpms.
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Old 10-20-2006, 01:42 PM
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Default RE: tuned pipes

Also if you start blowing glowplugs you are getting detonation, this also shows up in erratic tach readings, it won't hold steady and jumps around a couple hundred rpm. If you have detonation it will also pit the top of the piston and maybe the bottom (inside) of the head. Usually adding a .005 thick head shim will eliminate detonation. Your fuel consumption will go way up when using a tuned pipe.
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Old 10-20-2006, 03:47 PM
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Default RE: tuned pipes

WOW, DANGER DANGER information overload

Really, thanks for all the info. My first try with the pipe I destroyed 3 plugs. The engine was just getting hot and could not richen it up. But that was at 9.5" from the plug. After I lengthened the pipe the temps went down, plugs survived and started working on trying to get it tuned.

One thing that bothers me is at open throttle I can open the needle valve as many as 6 turns (almost out of threads) and I cannot get it to blubber. At first I thought my tank was not presurized but I did confirm this by taking the pressure line off the tank at full throttle and placeing it in a glass of water, lots of bubbles.

If I lengthen the pipe then I can richen it up but dont know if this is the correct length (12.5in).

I forgot to mention the plane is a DD look alike, delta, 3.5lbs and thin wing.

I will go over all the notes on this thread and see if I can use the info you guys gave me to get this done.

Again thanks for your info.

Keep it comming if you have anything else to add.

Larry
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Old 10-20-2006, 04:32 PM
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rcflyer1970
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Default RE: tuned pipes

Make sure your tank and fuel lines are large enough to handle the fuel flow, I have had to drill out fittings and run a larger line in some tanks and drill the clunk. Tank pressure can be a culprit to, I run a large pressure tap if I seem to have fuel flow trouble.
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Old 10-20-2006, 06:56 PM
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Default RE: tuned pipes

You're wasting your time with a 10x6 on a DD type plane, and going through the tuning process. You should be tuning with the 9x7 or 8x8 and looking for better returns on your time invested.
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Old 10-20-2006, 07:27 PM
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Default RE: tuned pipes

In regards to info left by Roarym. You stated the following:

The second is that the shorter the header, the lower the temperament of the engine; it will be more sensitive to high end needle valve changes.

On a web site I found it stated that hot, burning up plugs and detionation was caused by a pipe that was too short (overall length). After reading this I added about 1 inch of header pipe and the engine ran much better and I didnt melt my glow plug driver. I did not reliaze the the length of the pipe is measured from the plug head to the first widest part of the pipe as the exhaust flows, I was doing it in a straight line from the plug to the pipe.. This method brings the straight line measurement to about 9.5 in.

It seemed that the shorter the pipe the harder it is to needle it for rich running. Maybe I'm off the page on this but wouldnt you run it rich and then lean it out like you do with a normal muffler?

The last problem I experienced was I could turn the needle way out and still not effect the running like a stock muffler. I am using the blue fuel tubing with 7/64 ID (the stuff I always used). I dont think using larger than this would do any good as the fitting on the carb is no bigger.

Larry
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Old 10-20-2006, 07:32 PM
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Default RE: tuned pipes

The two meccoa (I used lower case on purpose) engines I have aren't worth the hay it cost to put in the horse that dropped them[:'(]. FYI. No transition, I couldn't keep them running in the air at all. Ran fine on the gound till about 4 seconds after they broke free of the ground. I finally took them off and replaced them with other engines. One time I actually called the LHS to ask if they would stay open for me to pick up another brand so I could fly the next day. I really wish I had the K&B I traded for them.[&o]
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Old 10-20-2006, 08:17 PM
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Default RE: tuned pipes

Well I flew the Meccoa last week with the pipe on and it flew ok, but didnt get on the pipe like I thought it should. Since this is my first pipe experience and the Meccoa was given to me I figured that if I was going to burn up a engine I might as well use that one.
After I get it right, I want to pipe my OS .50 sx on a Dago Red.

Ok, guys with all the info. After cramming my brain and reading your suggestions and going to the Jett website.
I figured that if I can't get the engine too rich I may have a fuel flow issue.
SO.... I drilled out the carb fitting to 1.3mm to 2.0mm, changed the fuel lines to 3.6mm, drilled out the pressure fitting to 2.0mm.

Gee, too bad it is going to rain tomorrow.

Larry
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Old 10-20-2006, 10:51 PM
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Default RE: tuned pipes

Some tanks have very small lines, clunks, fittings, most of problems I had were with larger engines, good luck it's a trial and error thing with engines that were not designed for tuned pipes and hi performance applications some work ok and others fall short of expectations.
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Old 10-21-2006, 09:55 AM
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Default RE: tuned pipes

They're as ugly as sin, and not very aerodynamic, but I got a 1100 rpm jump using a mousse can pipe on a LA 40. This gain was made with either a 11x3 or 11x4 prop. There might still be a DIY thread at the SPAD forum on how to make MCPs.
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Old 10-21-2006, 11:47 AM
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Default RE: tuned pipes

sometimes the nipple that comes with the pipe for tank pressure is a bottleneck, a quick fix is to remove it, enlarge the hole a bit with an awl and just shove the line into the hole, it'll seal if the hole is sized right, and the metal rolled in from the awl will make it "grip" the line tightly.
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Old 10-21-2006, 01:12 PM
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Default RE: tuned pipes

Hi!
Try using 5% nitro instead of 15% (if you use that...) using a pipe raises trhe compression ratio and as such lower nitro percentages is a must if not a 0,1mm head ...or more is used.
Also try a cooler glowplug. An Enya 3 or OS 8 plug is fine for most sport engines ...but for best performance try using a cooler plug like a Nova Rossi 5 or 6, or a Rossi 6.
Then of course you have to have a good, sleak model to fly really fast, like a Viper or any other Q-500 racer. And very important a good APC prop like a 9x6, 9x6,5 or 9x7. Do not bother with 8" APC props as those are too small for your sport engine.

Regards!
Jan K
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Old 10-21-2006, 08:14 PM
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Default RE: tuned pipes

Remember to richen your low needle it will restrict fuel flow.
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Old 10-22-2006, 06:04 PM
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Default RE: tuned pipes


ORIGINAL: combatpigg

You're wasting your time with a 10x6 on a DD type plane, and going through the tuning process.
You should be tuning with the 9x7 or 8x8 and looking for better returns on your time invested.
I tried to tell him that CP....I don't think anyone is listening. He cannot tune that pipe with that
prop on it....
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Old 10-22-2006, 06:37 PM
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Default RE: tuned pipes

I'm listening to ya! Just took out 3, 9 inch props and will try it. I have not run the engine due to weather conditions (it snowed this moringing[:'(]).
My thoughts were to try the 10 x 6 APC, then try some 9x5, 9x7, 9x7.5 and 9x8 APC's I had laying around. It just seems to me that a 9inch prop on a .46 engine will get PRM, but will the engine last?

I did have to richen up the lowspeed needle to get the idle and transisiton the last time I ran the engine with a 10 x 6 prop.
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Old 10-23-2006, 07:30 AM
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Default RE: tuned pipes

ORIGINAL: lbarnes

WOW, DANGER DANGER information overload

Really, thanks for all the info. My first try with the pipe I destroyed 3 plugs. The engine was just getting hot and could not richen it up. But that was at 9.5" from the plug. After I lengthened the pipe the temps went down, plugs survived and started working on trying to get it tuned.

One thing that bothers me is at open throttle I can open the needle valve as many as 6 turns (almost out of threads) and I cannot get it to blubber. At first I thought my tank was not presurized but I did confirm this by taking the pressure line off the tank at full throttle and placeing it in a glass of water, lots of bubbles.
Larry,

Its a learning experieince isnt it As I noted, when the pipe is set too short, the engine will not run properly and will be hard to needle.

Also, rpm expectations have to be realistic with regard to the engine you are using.

Of note, blowing glow plugs, 96% of the time, is due to one thing - a LEAN mixture setting - and nothing else. A short pipe can drive a mixture lean as the engine attempts (and fails) to stage up on the pipe, but does not have the fuel delivery.

When setting your mixture for flight (with a pipe) always back off at least 500-700 rpm - the engine will need the extra fuel in the air.

BTW... RPMs we are talking about with your .46 size engine and the 9" props are well within its capabilities... it will not shorten the life of the engine or cause a failure. The only real wasy to destroy the engine is to use unsuitable fuel (too little oil) and 'over prop' it and/or run it lean (get it hot).

Bob
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Old 10-23-2006, 02:19 PM
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Default RE: tuned pipes

Thanks Bob,
I do agree that my experience with 2 stroke engines that I was runnig way too lean and getting the plug, head and everything else HOT!.

I have taken some different angles one getting it on the pipe, However my last ones have been put on hold due to SNOW[:'(].

Hope it warms up to try again.

Thanks

Larry
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Old 10-23-2006, 10:15 PM
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Default RE: tuned pipes

Good points made about how to run that engine. A cheap engine needs cheap insurance and I've never regretted adding castor to a fresh gallon of store bought fuel. Guys can talk all day about the negative aspects of running castor, but I've seen power increased in some engines after using castor. I think almost any engine with decent compression and parts that turn without too much slop can be made to run half way decently. I would not throw any money at a Mecoa, but a home made MCP doesn't cost much and they do work.
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Old 10-23-2006, 11:37 PM
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Default RE: tuned pipes

Larry, yes you can expect to nuke plugs with a short header. Some fliers assume that a very short header just brings it on the pipe sooner, which it does but with consequences. You can run the engine rich and tune him to lean but the tuning will be something like walking a balance beam; the tuning will fall off more readily over a few flights. I dont even cut my headers anymore. I just get a pretuned pipe kit from Macs products, they get it close. If you run crank pressure in conjunction with a one way valve (you will need a cline regulator at the carb) you can expect great results. My favorite plug is the McCoy MC59; they take a beating.
Since we are on the subject of pipes, allow me a moment on my soapbox. I enjoy tuned exhaust, the sound of the engine making power is like music for me. I recently observed an incident where a club member spent time tuning his engine in the pits over a 1 hour period. He was called on it after a while, and a confrontation ensued. He didn't see the problem with the extent of it and would have needed help to haul his stuff to a designated runup area. We talked about it later and my response was that if he ran the engine next to my head for days on end, I wouldn't care, but the tuned pipe era is going away. A number of members at our club fly electrics, which I find cool but my observation was that new people to the hobby reject the noise of any two stroke engine. I think most people probably would have tapped him on the shoulder and ask to give it a rest but my point here is the heightened awareness of sound generation. Like all things modern, sound has succumbed to the environmental "footprint" as pc as that sounds.
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Old 10-24-2006, 06:40 PM
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Default RE: tuned pipes

I know that noise issues are getting some attention. I have a .46 size plane with a custom made exhaust due the the cowl area. It is loud when flying overhead, but most flyers dont mind because I am only flying it for about 10 minutes and then shut it down. I try to do my pipe tuning at home instead of the field.

You mentioned pre tuned pipe kit from Macs. I am using Macs products and the header and pipe (according to Macs) need to be cut . The instructions states:

Run you engine with open exhaust (no muffler), record prm. Looking the list of engines, they then tell you how much to cut off your header pipe in my case it was 2 inches off the stock header. Mount the header, rubber sleeve and pipe and record the RPM gain. They state that I should get about a 1500 - 2000 rpm increase.

With the 2 inch cut off the length of the pipe is 12 inches (as the exhaust flows) from glow head to widest part of the pipe. This is right in with the 11.5 inches that was stated on a earlier post.

That is where I started, and burned out 3 plugs and melted my glow driver plug in the process( forgot to take it off). Since I could not make the engine too rich I figures that maybe I cut the header too short. I added back the 2 inch piece I cut off and the engine ran much cooler and easier on the throttle response but just wasent getting it on. I did experience a 1400 rpm increase with this.

However I still could not make the engine run rich. I then assumed that I still had a fuel delivery issue causing the engine to run lean. I then opened the carb and tank pressure nipples to 2.0mm hoping that this would help deliver more fuel to the carb. I have not tried this new combo yet due to snow and cold weather.

Some people have posted that I am wasting my time with a 10 x 6 prop and will not be able to get it on the pipe using that prop on a .46. I will be trying 9 inch props (APC) when I can get a break in the weather.

If the engine still runs hot with the suggested header length I will add back some of the header pipe and maybe just get close.

Larry
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