Timmer01

would a tuned pipe do my fox 46BB any good? what could i expect to gain? and if so, which one? how do you tune a tuned pipe? iv herd of people burning up a engine with a tuned pipe, why would this happen?

w8ye

My Feedback: (16)

It would be just about the same price to buy a more powerful engine

Charley

My Feedback: (2)

It depends on which airplane and what you hope to gain.

CR

Rcpilot

My Feedback: (78)

You can buy tuned pipes and headers from Macs.
http://www.macspro.com/

You can expect to gain anywhere from a few hundred RPM too a few thousand RPM. Just depends on how you tune it.

The size you want is going to be any standard pipe for a .46 engine. They are listed on the Macs site.

You tune a pipe by cutting off the header and essentially moving the pipe closer to the exhaust until it reaches the RPMs you want to run.

You certainly CAN burn up an engine with a pipe. Cutting the header too short and going for max RPMs is one way. Another way is not knowing how to properly adjust the needles and running the engine lean. A tuned pipe is designed to create HP. HP takes fuel.

If you're expecting to bolt it on and fly it--go get a bigger engine. A tuned pipe isn't a simple bolt on item. Typically, you'll tune for a certain prop. Then you're stuck with that prop. If you change the prop, glow plug, fuel or airplane--you'll have to buy a new header and tune again. So, you better already know what prop and fuel combo you plan to run on this particular airframe or it'll be QUITE expensive buying new headers.

Tuned pipe theory is very complicated. I couldn't BEGIN to tell you all that is required for you to have a good understanding of it. I'd suggest you google it and start reading. You need to know how it works before you jump into it.

Basic pipe theory:
Exhaust creates a pulsing sound wave (varies with RPM)
Sound wave is sent down header and into pipe
Sound wave bounces off divergent cone of pipe and reverses direction
Sound wave travels backwards through pipe and header
Sound wave slams into escaping fuel charge from exhaust port
Escaping fuel charge is shoved back into cylinder before piston can close exhaust port

More fuel into combustion chamber = more HP.

You can tune for more torque. Or, you can tune for more HP. You can also tune yourself right into a fire breathing monster that is ruined in about 1/2 gallon of fuel. [X(]

Thats an overly simplified description of how it works. I sorry, but I don't want to type it all out. (not even sure I know it all) I'll probably make a mistake and then get roasted by several other people here over a typo. Best thing to do is google it, or somebody might have a link to tuned pipe theory that they can post here for you.

Good luck.

yallaair

If you go for a quiet tuned pipe, expect from 500-800 RPM increase compared to open exhaust. And a lower noise level compared to a stock muffler.

Charley

My Feedback: (2)

I love this misconception.

CR

Rcpilot

My Feedback: (78)

That type of comment was EXACTLY why I didn't go into all the gory details of tuned pipes.

If you're so smart, how about contributing something to the thread? Tell us why thats a misconception.

badger5964

My Feedback: (6)

Timmer01,

I fully support your effort to mount a tuned pipe on your Fox 46BB. My next project up is a Lanier Shrike 40 and I have a Fox 46BB and a macs header and pipe to mount to it. I would be most curious to see the data around the tuned pipe. David Gierke, (spelling)review of this engine several years ago in a model mag said it was "timed" for a pipe. The Macs products website tells you how to tune a pipe. They also have some charts there that show you typical gain. A Fox 45 is listed as having a 14250 rpm with open face (no muffler) and 15,100 with pipe. The Fox 45 is known to be a mildly timed engine, the 46 is more aggressively timed and should respond better to a tuned pipe.

[link=http:///www.macspro.com/tuning.asp]macs tuning info[/link]

Charley,
what is the conception?

Scott
[link=http://www.fayettevillercclub.com]Fayetteville R/C Club[/link]

rainedave

My Feedback: (1)

Rcpilot, when you refer to tuning the pipe for torque, what do you mean? Do you mean selecting a larger prop and cutting the header to achieve the best length for a lower rpm range? I ask because I'm planning to set up one of my SF .61's with a pipe using an APC 12x8.

Thanks,
David

Rcpilot

My Feedback: (78)

Thats it RainDave.

I've never done it that way, but thats supposed to be how it works. You pick the prop and fuel, then tune to it.

I always used tuned pipes on speed planes and tuned for max RPM. Usually a shorter header with a high pitch prop.

Charley

My Feedback: (2)

A tuned pipe will give you a power gain on any engine. How much and gain depends on the engine and the pipe. What a tuned pipe does is help scavenge the exhaust gases from the cylinder and stop the incoming charge from going out the exhaust port. It doesn't "supercharge" it. The idea that the return pulse shoves gases back into the exhaust port is a myth that many buy in to. For this to happen the flow would have to reverse in the exhaust system at many thousands of RPM. It just doesn't happen.

Don't believe me? Ask Dick Hanson.

Charley

My Feedback: (2)

It all depends on what you're after. Any engine will show a power gain with a tuned exhaust system. Some more than others, depending on exhaust timing. First you have to pick your prop and/or RPM range. Then you have to decide what kind of pipe you want. Some pipes will "tune" (resonate) in a narrow RPM range. Others (broad band pipes) will "Tune" to a wider RPM range. The narrow band pipes will give you more power at the "tuned" RPM. Broad band pipes will give lesser power boost over a broader RPM range and are more flexible in terms of throttle settings.

So, what's your application?

CR

Timmer01

i was thinking about putting it on a tracer. its a pattern plane, how would it do going fast? would it have a problem with flutter, or is pattern flying done at a high speed. i like the looks of the tracer, i want something like that thats fast. this would be my 3rd plane. first is a trainer(eagle 2) then a sig citabria, (i have it, needs a new rudder, got given to me) then the tracer soon. since i have the engine, and its the largest the tracer recommends, and the fox is a stump puller, i thought why not put a tuned pipe and see if i can get a little more rpm out of a 10X7. (speed, i just wana go fast!!)


if ya'll think the tracer is a bad ideal, what should i get ( that LOOKS like a airplane, the Lanier Shrike 40 is fast im sure, but, like i said, i like the looks of the tracer.)


any other questions please ask. thank you all for your input so far, the next rounds on me

Hobbsy

My Feedback: (102)

Timmer, here's what the thing looks like in real life on a Fox .46, I scrounged through my, "I ain't seen it in a long time stuff" and there it was. I even found the Allen wrench I modified to tighten the rear mounting bolt. You screw the rear mounting bolt most of the way in and then slide the header over it then place the front mouning screw.

scott17

There is a really cool FOX brand tuned pipe for the Fox 45 on e-bay right now......Ask me how I know..

Timmer01

where did you get that header? and is that a diesel converson? how does it run like that?

Hobbsy

My Feedback: (102)

I think I bought that header and pipe from Tower years ago. Pipes don't work all that well on Diesels because the exhaust is cool compared to a glow engines exhaust. With a MVVS quiet muffler the .46 conversion turns a Graupner 12x7 in the 9,300 rpm range.

Charley

My Feedback: (2)

That header and pipe look like Macs to me; Tower sold 'em. Doesn't look like you ever used it the pipe, because it's still full length. I have some of them. Also, the wrench looks like the one that Fox put in with the Pylon engines. Ah, history....

CR

DarZeelon

Quote:

ORIGINAL: w8ye

It would be just about the same price to buy a more powerful engine.

Jim,


I don't agree!

It will be MUCH CHEAPER to just get a larger, more powerful engine!


Unless your are competing with your plane in a class where the engine displacement is limited, or that the engine you have comes with a tuned exhaust system as a matter of course (at a price comparable to its normal exhaust system, up to, say $30 more), tuned pipes are not the way to go.

If, say, a .50 engine makes comparable power to a .40 with a tuned-pipe, the .40 engine + the tuned exhaust/pipe will cost $60-150 more than the .50 and be 2-8 ounces heavier...

The exceptions are the mousse can (if you fabricate the header by yourself), or the MVVS tuned silencer (ditto)...

So, what gives?

yallaair

Maybe this is correct when it comes to .40size engines. However, if you look at the MVVS .91, it weights approx. 535 grams without silencer. With a MVVS tuned pipe and header, total weight is 755 grams. With a average muffler weight of 150 grams, there is only a 70 gram weight penalty with the tuned pipe. But for this extra 70 grams, I get an increase of 1000 RPM on APC12,5x12 ( from 9000 RPM open exhaust to 10000RPM with a tuned pipe!). And the lower noise is a great bonus! Conclusion is that if you want a quiet engine and a good power to weight ratio, the you have to get a tuned pipe! That's why F3A pilots use them

Timmer01

uh, im not goin got buy the engine then buy a tuned pipe, i have the engine, how do you all think its cheaper to BUY A ENGINE THAN A TUNED PIPE???? i must be missing something here........

DarZeelon

Tim,


Let's go through the motions here:

The price of Fox engines is [link=http://www.foxmanufacturing.com/index.php?main_page=index&cPath=143&zenid=3d5fce3d501680dac296cb82c660da17]shown here[/link]. I know it is the MSRP that no one sells at, but let's follow it.

The .46 ABC engine costs about $187 and the .61 ABC engine costs about $242. The difference is $55.


Now, let's go to the [link=http://www.macspro.com/]Macs web site[/link].

A 258x header will cost you $29, a 1040 quiet tuned pipe will cost $80 and a 1240 muffed pipe will be $68. Your choice.
This investment of $97, or $109, does not include a coupler, retainer bands and tuned-pipe bracket(s).


Do you think that after investing a lot more in the Fox .46, it will now make the same power as the Fox Eagle IV .61???
Not in your life-time...

If you need the power of a .61, a piped .46 will not do it. Just buy the .61 outright.

-------------------------------

I mentioned the inexpensive solutions; the mousse can, the Tower/Hobbico .46 muffler and the MVVS #3248 tuned silencer, since they cost much less... Providing you can adapt any of them to your engine.

NM2K

My Feedback: (14)

Yes, but ANY two-stroke engine can realize a gain in power with a properly tuned pipe. The size (length) of the pipe depends upon the rpm range in which one intends to run the engine.

Even old baffle piston two-strokes experience a power gain from a tuned pipe. My friend, Syd Clement, Bridgeton, NJ, put this puppy to rest by dazzling everyone with his Bridi Dirty Birdy 40, which was powered by a tuned pipe equipped K&B .40 (old baffle piston version), running an M&H carburetor. This occurred many years ago, right after Schnuerle ported engines became popular and common.

I shouldn't say this, as I'm bidding on one at the moment, but there are two original Fox tuned pipe setups up for auction on the Bay at this very moment that will fit your engine (I've got plenty of stuff, so if I lose to you, so what?). I've owned and used the Fox tuned pipe before and it worked wonders on my large block Fox .45BB.

Instead of adjusting the length of the Fox pipe or header, just substitute larger or smaller props until it "runs right". Don't forget to readjust the fuel mixture each and every time that you make any kind of change. i.e., prop size or glow plug type. Have fun! Oh, and get ready to go through a glow plug every four or five flights - even when everything is matched perfectly. Rossi glow plugs were the only plugs (and OPS) that I found that would stand up to more flights while running a pipe. Also, keep the nitro to 10% or less, if you're having trouble with preignition.


Ed Cregger

NM2K

My Feedback: (14)

Tune the pipe so that the engine is "on the pipe" in the vertical ascent. That is tuning for torque (longer header than normal).


Ed Cregger