Discussion on pipes for 100cc class motors

[branwell]

One of my goals this year is to come to a better understanding of how tune pipes work and what about them defines their performance.

To help with this, I got two 110” EF Yaks and two motors, a BME 116 and a DA100L, and three sets of pipes. See pics.

The black pipe is the ES Composites 55G.
The middle pipe is the KS 1060.
The outside pipe is the MTW RE2.

ES
Weight 4.35oz
Max diameter 50mm
Length 700mm, 800mm inc stinger

KS
Weight 10.44oz
Max diamiter 59mm
Length 690mm, 742mm inc stinger

Re2
Weight 9.45oz
Max diamiter 55mm
Length 690mm, 750mm inc stinger ( not including the extension shown in the pic )


Looking at the pipes....

The divergent cone sections are quite different.
Where the RE2 has a continuous curve, the KS and ES have single angle cones.
Where the RE2 and ES have short cones, the KS is much longer.

The bellies are also very different.
Where the ES and RE2 have long bellies, the KS is short.

The convergent cone sections are also different.
Where the RE2 and KS have convergent cones, the ES had a flat plate.
Unfortunately I have only been able to “feel” the cones with a stick and I cant feel their specific shapes. Only where they start and stop.

The muffler section in the ES is much larger than the muffler section in the other two.


Some pipe basics.... as I understand it.... which is very iffy....

The Divergent cone is mainly responsible for the shape of the power band before the peak.

The Belly, or area between the Divergent and Convergent cones, is primarily responsible for the shape of the peak itself.

The Convergent cone is responsible for the shape of the power band after the peak.

Can we make any assumptions with this info?
While I don’t know much, I know enough to know its not that simple, but here are some guesses that will be interesting to see if they pan out in the real world.

The KS has a longer shallow angle divergent cone.
This should cause it to take more rpm to go from off pipe to on pipe making the transition zone feel less instant., less light switch.
The RE has a continuous curve cone. The reading I’ve done on pipes suggests that this has the effect of making the cone longer, making the transition less dramatic.
Will be interesting to feel these two pipes in an apples to apples comparison.

The ES has a flat reflector plate instead of a convergent cone. This should kill power fast after peak. If one sets the header length so it peaks on uplines, the drop in power after peak in level flight could help keep air speed more constant and noise down with less throttle management.

The KS has a very short belly compared to the other two, so in theory, its peak should be less wide than the other two, but because of its longggg convergent cone and that it has a divergent cone, it might not be as noticeable as one might think.

From the experimenting I’ve already done with the ES pipe, I can say that header length makes a massive difference to power and engine feel. Given this, getting a good feel of the pipes that is not too colored by the header length’s, which are different for each pipe, and also different for each engine, might be difficult if the differences in the pipes performance is not pretty glaring.

Another pipe I would love to try that gets little mention on the online forums is the Macs Quiet Pipe. Several I've spoken to that use it where very impressed.

Branwell

[jfstrama]

Branwell,

Here are a couple of items that I use to teach how tuned pipes work and how to adjust them for different engines / headers.

Pictures are worth a thousand words but animations are even better. This is for nitro trucks / cars but the principles are identical and it goes through a description of what happens when the pipes are out of tune long or short.

http://www.bukupower.com/animatecorrect.html

The second way to learn is to design your own! Here is a sight that follows the standard methods, but materials and other tweaking / testing is what you pay for when buy one (this can be hours worth or years worth, your mileage may vary!).

http://www.mh-aerotools.de/airfoils/javapipe_en.htm

Tuning is part of the challenge of tuned pipes, 3 of them? 3 times the fun!!!

MadDog Joe
Flying MadDog Aviation

[brycesteenburg]

Branwel, When I was racing karts I gathered up approx. 30 different tuned pipe assy's and would run them all till I found the best size,style of pipe, chamber size and design for the track, engine and weather conditions. Once I found the best length of all then would install what I would call a slippy pipe header to main pipe assy and controlled the length of pipe on the run with a push\pull cable. Worked great for sliding tuning\torque range up or down slightly coming out of corners and down the long straights while running on the track. Between tweaking the mixture on the fly I could also do slight adjustments to the pipe on the fly. Went through a few pistons and heads learning but it did work very well. Worked just like a slide trombone slide.The santioning body outlawed slippy pipes since then and then had to pit to change intermediate pipe lengths after that. You might want to set yourself up something like that for your testing purposes. Now that I think about it I wonder if a guy could set up a servo to slip the pipe on the fly with some data acquisition and do the same thing. Mix it to the throttle and even figure out some sort of pipe slip curve to rpm to help low rpm and high rpm. Probably have to tweak the mixture to go along at the same time. Anyhow sounds like you are starting to really focus on this. Thought I would let you know my experience on how I did it when I was doing it. I would send you some pipes and chambers but the stuff I was running was 125cc @ 12,000 to 16,000 rpm curves. They would be way too big and heavy for our airplane apps.

Have fun,
Bryce

[dick hanson]

Bryce hit the nail on the head - you have to have the length right for the conditions
That is just the starting point
The reflector setup can be done in variousways -but volume will play a large part.
The temperature inside the pipe ideally remains constant -or at least predictable
The volume and the pressure will affect the temperature
The material used to make the pipe will also affect temperature CHANGES.
Guess which pipes I like ?

[brycesteenburg]

Dick Hanson, Thanks for the complement. I still enjoy thinking about this stuff. It is interesting.
Bryce

[Paul5992]

	Quote: Originally Posted by dick hanson
	Bryce hit the nail on the head - you have to have the length right for the conditions That is just the starting point The reflector setup can be done in variousways -but volume will play a large part. The temperature inside the pipe ideally remains constant -or at least predictable The volume and the pressure will affect the temperature The material used to make the pipe will also affect temperature CHANGES. Guess which pipes I like ?

Don't leave us hangen. What pipe do you like Dick? I was thinking about pipes, your opinion would be very important for my decision.

[dick hanson]

	Quote: Originally Posted by Paul5992
	Don't leave us hangen. What pipe do you like Dick? I was thinking about pipes, your opinion would be very important for my decision.

The carbon fibre pipes for up to 60 cc per cylinder -my preferrence
they are more temperature stable and some what lighter . So far the ES pipe is easily the best made of any I have seen.
Ed has got them well sorted out now , for small stuf up to this size.
I am out of the large plane market now .

[branwell]

Dick, when you say heat stability, are you talking about heat retention?

Joe and Bryce, thanks for the input.

Branwell

[dick hanson]

Aluminum will tranfer heat very rapidly
carbon fibre is more like an insulator rather than like a conductor
You can easily demonstrate this for your own information, by using a hair dryer
heat one end of any pipe and see how rapidly the heat transfers
Fer Ch---st sake don't play a heat gun on the carbon fibre pipe!
It is possible to burn up a carbon fibre pipe but doing so simply demonstrates a lack of understanding how engine and exhaust systems need cooling.
here are typical installations
- you don't have to heat up the cf pipe and reheat it from extended cooling off periods, in order to be at desired "tuning"
Why ? it has extremely low heat transfer characteristics.
Bythe way a very thin s/s pipe is actually better than aluminum in this respect but of the three the CF also deadens sound better
so the price of the cf which is typically more , does have definite benifits.

[branwell]

Hi Dick,

I must be misunderstanding what you are trying to share.

If I run the CF pipe on my bench at full power for 30 seconds, then let the system idle for 90 seconds, the CF pipe cools enough to be warm to the touch. Under the same conditions, the aluminum pipe ( RE2 ) was still hot enough to burn.
I surmised that the CF pipe, having less than half the mass of the aluminum pipe, cools much faster.

What am I not understanding here?

On sound, the ES is definitely quieter than the RE2s. I haven't compared them to the 1060s yet.

Branwell

[gmorales83]

If I may....I'll butt in with a little material property hooplah:

It makes sense that the carbon pipe feels cooler, its molecular structure is very open (like a cage) which is a poor conductor of heat and thus less heat reaches your hand when you touch it.

Its like placing a stainless steel mesh and a stainless steel plate out in the sun and then placing your hand on it. They may both be the same temperature, but the plate will burn your hand because of the increased contact area.

Obviously the carbon fiber pipe is not a porous mesh, but its molecular structure is much less dense than than that of aluminum....it also acts as an insulator because the carbon-carbon bonds can take in take in more energy (we call it heat) than closely packed aluminum atoms.

[dick hanson]

Contact area example true.
On the pipe- the issue is about cooling the exhaust charge
As example
fill a cf pipe with hot water
fill a aluminum pipe with same temp water and fill a ss pipe with hot water
The aluminum pipe will cool the water the most quickly as it transfers heat from the water to cooler air, far more rapidly than s/s or cf.
restated : the pipe temp will quickly vary with exhaust charge temp
as I noted earlier - you want a pipe which is stable in temp.
aluminum is most commonly used simply because it is cheap, light and easy to fabricate - period-
In looking at your pictures -If I may, I am a bit puzzled at the length of the setup-unless you are piping for really low rpm
also the long teflon sections shown-if unsupported internally will collapse.
What operating rpm are you shooting for ?
I am guessing that with those pipes (look like latest version of Ed'spipes ) the baffle is17" from pipe imlet so 28-17= an 11- 13" header for running " somewhere in/around 7000 "static rpm.- Your engine exhaust timing may be somewhat different than DA/ ZDZ etc., but the resonant length to rpm setup does not change much.

[branwell]

Hi Dick,

Thank you for your response.

....The water test.
At your suggestion, I took an RE2 and the ES and filled them with 107 degree water. Once their bodies had reached 107, I emptied them and refilled with 107 degree water and placed them in a sink.
30 minutes later, the water inside the RE2's measured 98 and the water inside the ES measured 93.

This is the opposite of your results.

Thinking this might be a volume issue, the ES is smaller, I refilled the ES and transfered that water to the RE2. I then refilled the ES again and waited 30 minuted.

Same result, the ES cooled much faster.

Here is a pic of the setup. There is no air blowing in the room and the pipes each have the same amount of surface contact with the sink.

The result I got is opposite what you got. I am wondering how that can be. What aluminum pipe where you testing with?


....Length of Headers.
The ES pipes are the latest generation 55G's and measure 17.75" from the input to the reflector plate.
Ed thought I would need headers in the 11 to 12 inch range given my 6500 static target.

Given this, I started at 15" and cut back. I stopped at 13.?? as the motor was loosing power and running hot.

The next day, using extensions, I started at 15" and increased the length finally getting a peak of 6650 ish at 16.5". I flew the plane a little and ended up adding another .75 to the headers.

Why so long?
The motor I ran the ES pipes on is the BME 116.
Its exhaust port is open for 168 degrees ( the DA100L is 150 )

If I add the pipe length to the header length, and .5 for a gap, and .75 for the length between the exhaust flange and the piston skirt, I get 36.25". If I apply that in the following formula,


N =((Eo x Vs) / (Lt + .5 + .75))

Lt is the tuned length, in inches
Eo is the exhaust-open period, in degrees
Vs is wave speed in feet per second (1675 )
N is crankshaft speed, in RPM

I get a tuned RPM of 7817.

If I adjust the exhaust timing to 150 for the DA100L, I would need 13.64" headers for the same tuning rpm.

And if I compare this to the total tuning length I fly the DA / RE2 combination at, its collates pretty closely.

....Long coupler.
I use long couplers ( no more than an inch gap ) on the bench to make small length adjustments without having to cut the headers. In the plane, I use a .5" gap. Do you think that is okay?

Please remember I am new to pipes. I've read a couple 2 cycle tuning books, played a little on the bench and in the air, but I still have a long way to go before I understand this stuff and really welcome your input.

Thanks,

Branwell

[dick hanson]

I'll keep it short
The water test - I am surprised - I used the water thing to illustrate - I never actually did a water fill test. And likely never will.
but nevertheless - aluminum ALL aluminum is a very good heat conduuctor irrespective of grade of aluminum. CF is an insulator. Warm one end of either material and see how long it takes for other end to heatup
The tuned setup?
I can not answer why you get the results you get.
The higher exhaust timing 165 vs 150=10% longer exhaust period .No big deal. The tuning setup is a "broad band tuning - so if you get a smooth transistion and decent power increase - use it.
When I did my own small paint can setups years back the ZDZ folks said my muffler was too small - later they said - the very long large header changes the volume and likely accounts for my good results .

[Cooper 1]

Im anxious too see your results
I just purchased a BME 116 and a set of ES55G's
I'm wondering what the header length will be for best power at around 6400 to 6700 rpm.