wvr

Hello,

Does anybody nows if the length of the header-pipe is critical for a gas engine with a muffler like KS/PEFA/MTW

Thx
Winfried

cmitch232

My Feedback: (3)

I'm sure you're gonna get a lot of opinions on this one. I run a ZDZ-80 single on a Carden CAP-232 with a KS cannister. With a tunnel built into the fuselage, we had to use the shortest coupler possible so that the exit hole is in front of the wing tube. We wenen't sure how it would work with a header that short. My engine develops tremdous power (7,200 rpm plus) with a mejzlik 26/10 prop. All I can say is that my engine doesn't seem to care.

pacrat

Muffler or Tuned pipe?
I have found that header length on a muffler dosent cause to much efect on the engine,
But it is criticle on a tuned pipe,
I can E-mail you the formula for the tuned pipe calculation if you wish.
Cheers

Geistware

My Feedback: (16)

I plan to use a canister installation on my next plane. I want to move up the the 80-100cc size planes.

wvr

to cmitch232,

which type cannister (KS) did you use for the ZDZ-80?

Thx
Wvr

pe reivers

Winfried,

Give Krumscheid a call. He is a most helpful guy. He just hates to reply e-mails.

For the 58cc engine he has prepared flanges and 25mm headers, as well as a tuned pipe.
Any KS front inlet-front outlet kanister for a 60cc engine will do.

I ordered some (by mail) and got no response yet. He probably waits for me to call to finish off the details.

rmh

The setup for the most power may not appeal -or it may -
as you pipe tune for most hp -you may cause a nasty step in the throttle response.
This will show up on larger props .
It is not a ZDZ problem -it is simply how resonant tuning works - for all around good performance increase - on a tuned setup --- the KS 80 can with front in -rear out -and 12" of header and a Mejzlic 26x10 --is a decent starting point.
IF--the plane is light -a heavier prop load may work just fine - IF you run wide open all th time -you can go even shorter and get more max power but you will soon run into a carb flat spot which you will likely over lean the engine to try and fix.
The engine has to use more fuel to produce more power
Don't buy into any talk of more power on less fuel - that's simply wistful thinking.
The catch here is that low and midrange do not want more fuel but as the resonant tuning kicks in -the engine wants a LOT more fuel - Fuel consumed = power. forget BS talk to the contrary.
So If engine setups are not your cup of tea - keep the tuned setup on the mild side
You may find that a non tuned - good quiet muffler on a very short header is better for YOU.
In this case - a 70/80 JMB can .
the total power is not as high as the tuned setups -but the throttle is easy to adjust and power is still very good.
We run different setups on our 80 singles - for 3D- a JMB muffler - for max power - a tuned pipe.
If you really understand pipe boost and how it requires fuel and pay attention to carb tuning and related prop setups -you can make this 80 perform with or better than most 100's
Not looking for any arguments .

Smokey

My Feedback: (16)

Dick.... I just want to clarify what you said. It is better to use a JMB can for 3D over a tuned pipe? Is the JMB still better than a KS 89 can? This is going on a 35% plane probably weighing 25 lbs. All I plan to do is 3D or crash trying.

Smokey

rmh

Better -simply because it is not sensitive to length.
For learning the "3D" stuff -you need smooth throttle response.
easier to do with non-tuned stuff.
Also - keep prop loads down- that is - let the engine rev-
largest prop-- a 26x10 Mejzlic- also try26x8-keep static rpm up in the 6000 range.
It takes practice to get comfy with a model hanging on the prop all day (zzzzzzzzz)
and the engine is loaded far heavier than when actually flying thru maneuvers at speed.
The heavier the model -- the smaller the prop .
Somewehre between 24x10 and 26x10 , you will fing a combo you like for 3D
On my IMAC plane - I can run the 27x10 stuff - no problems as the engine is unloaded most of the time.

pe reivers

Dick,
An over-all good advise you gave here.
In a MCP or "tub" exhaust, more volume is equivalent to less sensitivvity to setup accuracy over the whole engine's rpm range, unless you want to tune the volume to a specific rpm response. :_) (I love it when I depart on simplicity). With a certain volume on a specific engine, a gain will be noticed over open exhaust measurements. Sometimes the engine porting tune is such, that you <must> use some kind of a tuned system behind it.
This however should not be the case in airplane engines since they drive quite a different load than road racing engines.

Winfried,
In general, if given a choice between the 80cc or a 50cc kanister muffler, go for the larger one, if you can manage it in your model.

rmh

The ZDZ50 (NOT the NG series) is a example of tuned port design.
If you study the intake/exhaust releationship -this is obvious.
When these engines were first released -I found that they ran like gangbusters- simply because I use a header and some kind of can (tuned or non tuned.)
Those who elected a restrictive in cowl setup did not get the design advantages of this engine.
Good power but not the high output it was capable of delivering.
The NG series use a different port/sleeve piston setup which flows in a different manner.
It is more tolerant of the restricted exhaust ( also has lower exhaust timing.)
Overall power on this setup is as good as anything I have seen in this size engine.
On correct tuned setup -it is really a treat.
On these engines (both series ) they respond better with larger cans .
Especially on larger prop loadings.
I see more people here using headers and cans/tuned stuff also.
this also goes for the other brands of engines.
Noise has really become an issue---

Kris^

My Feedback: (1)

I've run canisters on every gas engine I've had in the air for the last 4 years. After the 1st set it was impossible to go back to exhaust diverters. Until recently I had not played around very much trying to tweak and peak an engines output, but had just gone with the recommended setup and left it at that. While playing with the BME 110 Xtreme, though, I found that all the "rules" for making power could be forgotten if you just tweaked a setup and decided to be happy with the end result. My "headers" are exactly 2.5" long on my 110's, but I also feed the exhaust into extremely oversized "75" cc Pefa canisters designed for the 3W150's. This picks up about 200 rpm over "stock" but is still very smooth in the midrange and at idle, but REAL "tuned" length for the BME can only be achieved with a much more "engineered" exhaust design. The "hot" Setup for the 3W106's, as per Gerhard, is a 7" header into the "70cc" canisters meant for the 3W140's.

If you are looking to make only top end power, a true "tuned pipe" is the only way to go. .this works great for Pylon racing, and not much else, because it will kill your midrange throttle and you will have a lightswitch for a throttle .. on or off, and not much between.

Best bet, if you want a good running engine without being "peaky" is to order an oversized canister exhaust for it (by 10-15% of the canisters rating. . they tend to be a bit optimistic, so going larger is a good idea) , and an overly long header, then put the engine on the test stand, and start slicing off an inch of the header at a time till you get your rpm peak. Be sure to adjust the mixture as the exhaust scavenging characteristics change with the different exhaust flow characteristics. The canister style muffler will keep the max power from being "peaky" but you should realize a substantial power boost as the flow characteristics become mildly optimized.

rmh

A big can on a very short header just makes for a nice muffler - non restrictive -
a couple of hundred over an in cowl setup is reasonable -
I use the full length KS tuned pipes on everything from the 50 single-to the 160 ZDZ .
They do get long ---
the over 70 cm to tuning point is pretty common .
pretty much the same setup on the DA150's . The power boost is really excellent and smoooth transitions.
So far the quiet muffler by JMB - with very short headers is about the most fool proof setup I have tried.
No "boost" but much better than the in cowl stuff.
best setup for 3D where you are just "throttling"all the time

DKjens

My Feedback: (50)

Pe, got a question for you. I'm running the mvvs58i in a WildHare 28%Edge540T at the moment. I'm using an approximately 10-12" header into a 2.75" x 16" JMB can, meant for a zdz80rv. I only have 4 litres through the engine an am very happy with all aspects of this engine. I went from a 24x10 to a 22x10 prop on this plane, both Zinger Pro props or the like. The fully fueled weight is 20 lbs. and it has very good vertical performance. I often do uplines and pull outs on much less than full throttle, then when applying full throttle you can hear the prop starting to bark. I would like to get a 2.6m Composite Arf Extra, and it looks like the RTF weight will be in the 24 lbs area. I know you guys have been running this engine over in Europe for some time, and I think somebody is flying it in a 26 lbs plane there. According to your experience, what is the best set up for that engine for 3D (shorter header?) and how does it perform in the tests and planes you've seen? I am looking for low wing loading, precise and honest plane, pull out power, upline snaps, but not gut wrenching water falls.
DKjens

Kris^

My Feedback: (1)

In most cases, I'd agree, Dick. A big muffler, with free-flowing characteristics, will help give you a slight boost over a non-tuned diverter or more restrictive muffler. But, in this case, when setting up the header length, I started at 10" of headers and then gained 600 rpm over the course of shortening the headers down to 2.5". Anything over 6" of header and the power was down dramatically from even "Diverter" rpm figures, showing a lack of tuning from the setup. As the length lessened even further it became necessary to start richening the mixture, to the tune of about 1/2 turn richer, showing that the exhaust side was starting to do it's job and boost power. Similar testing with other canisters of the same theoretical "tuned" length of header and canister showed no boost, giving credence to there being more to it than just a big muffler with short header. The parts all have to work together, otherwise you'll never realize any gains.

rmh

The various cans on the market are not the same internally.
Your short header setup -which you noted worked well , may not work well on a Vtech setup.
big internal differences:
First is the overall length of the header tube-which extends into the can.
Next, the distance from the end of the "header", to the reflector.
Then, the PRESSURE in the expansion section.
This is never addressed in any of the so called text books on pipes I have thumbed thru - rather, they dwell on theoretical wave forms etc..
In hands on testing , we found that changing the final exhaust outlet size, could make big differences in the engine response.
One test setup I made, had a trombone setup for the header tube in the can.
The can moved fore/aft as the header remained constant in length.
The result being that the can volume remained constant ,yet the reflector distance to the header outlet varied.
also---- the final outlet flow to atmosphere, from the contraption , could be regulated.
A pressure gauge,tapped at centre of the can body, showed internal pressure.
Power boost was ALWAYS accompanied with a rise in gauge pressure.
I have a goofy tuned setup , for my 50 -which is simply a header 6" long dumping into the lid end of a pint paint can and the exit being a small dia exit tube running into the bottom end of the can.
this setup does tune -but is very peaky.
It also requires the engine be set "four stroke" rich on the ground.
I get inquires as to proper length for headers -
unless I know the entire setup - engine/can/prop/desired performance - I really don't know - but try to answer on the conservative side.
The Pefas are different cats -compared with KS and KS also has differences in performance in same sizes -such as front in /out and front in /rear out.
The Vtechs are another approach and I found that the smallest setups which really work -are permutations of that setup
They also have a noiser note in the air.
All of these differences in cans/ operating lengths and the power band being addressed , obiously cause confusion.
I get the std question," I don't give a shet why it works, I just want the best setup" and that answer is simply an unknown.
At least ,for me.

pe reivers

I have a nice little program, written by a Belgium music professor. it is available on my wanadoo website http://home.wanadoo.nl/pereivers/helmholtz.exe. I put it there for safekeeping, and this is the first time I see others publish their working along the same lines. Thanks guys.
Using the program it is clear how the pipe length and tub volume influence each other, and the longer pipe makes the setup more peaky (high Q-factor) Thus the shorter pipes make it less sensitive to volume mismatch and wrong pipe diameter, like Kris noted.
Like Dick noted, more power is accompanied by higher internal pressure, because this pressure is the spring behind the spring-mass system that it represents. The pressure, being the spring in the spring-mass system, also inreases resonant rpm, and is governed by the tub volume, stinger pipe length and diameter.

Things are shaping up. Dar Zealon, are you reading this?? I wrote you an e-mail on the principles involved

DKjens,
I do not have that much experience with the engine yet. One on my test stand, but little time to do many experiments. It's winter, and my oil burning heating goes berserk, eating at my spare time trying to fix the 40-year old oil pressure regulator. Add to that my venture to combine two MVVS engines into one 1/12 rc-combat monster (.28+.21)=.25 short stroke), to get me going for the new combat season.
Winfried has an engine as well, so we realy are a small circle of users at the moment. Morris keeps his mouth shut as usual. From Krumscheid I heard, that he has systems ready for the engine. From MVVS I have word that they work their asses off to get more engines ready by spring. I still have two on the shelf from my last order.
MVVS also works on a smaller engine in the 40-50cc range, and a watercooled 58cc for cowled-in applications and scale radiators. Do they bite off more than they can chew?? A very dedicated small team they are.
I plan to put my test engine in an Airworld Extra300 which will be about 22 lbs. My KS orderd stuff did not show up yet, so I make no progress whatsoever.
Feeling unhappy??? who,, me?? No way! [>:]

pe reivers

Dick,

It would be interesting to compare notes on your trombone setup, since in reality, nothing changed when you moved the tub to and fro along the same pipe. Or did pipe length change??

We achieved very good results with a restrictor pipe (closed off header) dumping into the main large volume canister (tub). Only 100 rpm loss as compared to a tuned pipe.
This system prevents the scavenging gas from entering the header in which a high pressure is present at that time. It is very silent as well.

rmh

I know that setup - an English fellow had same setup -in which exhaust had a large plenum at 90 degrees to a restricted outlet from exhaust.
On the sliding can, the change was distance from header outlet to reflector end of the can. I tried a cone, a concave end and a flat plate as end of can.
The can stayed non resonant as long as the header was over a couple of inches from end.
power boost waspossible, when the reflector was aprox 1/2" from end of the 1" dia header.
My guess was that this determined the actual wave length in the header tube (also tried in various lengths) and the pressure in the can, provided the pressure for that wave to "self excite" if you will.
I have a classical training on the clarinet -as well as playing other reeds.
The musical instruments achieve their tones/overtones is a similar method to our tuned pipes.

On the clarinet -- the player sets the initial vibrations into the tube with a vibrating reed.
Then, the various holes in the tube , change overall tube length
Introducing the "octave key", changes the tube length responses.
what was an F ,in the open tube , jumps to a C above c ( f-gabcdefgab-c)
at this frequency, one closes some holes and the frequency jumps into another ,higher set of tones. To make this work, the reed on the mouthpiece which starts the vibes -must also resonate differently. The player learns to redirect the air into the mouthpiece.
On a trombone (slide type) there are a number of positions and depending on how the player forms the pressure into the mouthpiece, these positions of the tube (lengths) produce different frequencies.
On a bugle - the tube length is constant but the operator forms different pressures into the mouthpiece and you get quite a few different tones-each a mathimatical shift in frequency
On a guitar , a string is shortened and OR retensioned to produce a given tone.
On a 5 string banjo with Scruggs pegs, the operator changes string tension on one string whilst varying string length on the 4 parallel strings.
As you know - EVERYTHING is made up from vibrations- these are some of the simple ,audible ones. (string theory)
I knew when I started playing with tuned pipes that there were really no hard and fast rules ,such as the handbooks called out.
There are sooooo many dynamics at play--

flier

My Feedback: (7)

Dick
I was wanting to get your views as to the exhaust setup I plan to use in a 35% WH 330L @ about 27-28 lbs.
ZDZ-80RV with the KS Header seen in this link; http://mikepage10.homestead.com/Mufflers.html
going into a KS-95VS-4 Canister
Turning a Bambula Power Prop 26x10

Mostly IMAC flying with some 3D

I know that you have much more exper. than I with the ZDZ80RV and cans,
So I ask you for your input .

Thanks for any and all help,
Duane

rmh

That setup is very nice .
It will work just fine.
I do most of my 80 and can setups , with the engine rotated to about the 8:00 position.
This allows for a single header bend.
On The WH35%, I did this setup as shown in attached pic.
I would suggest the front IN and rear out can by KS- I think it runs harder - It does have a little more internal area.
If you can swing it - the full length KS80 pipe is even stronger - but in the WH35%- the setup can be too tail heavy.
In this plane - balance is a real point of concern with the 80 engine.
I moved rudder servo forward and stripped and recovered elev and rudder after removing all sheeting and cap stripping them.
For the prop -for 3D stuff - let the engine rev-
Tho the 80 easily spins 27x10 MenzS in low 6000range, it will perform better using a 26x10 Mejzlic and running upwards of 7000 on the ground.
This rpm depends on tuning setup you use.
Do not use a short tuned setup - the engine can get rough in mid range.
The WH35% with this setup can be under 27 lbs -
weight is the enemy of good 3D flying
So-- my suggestion is to exercise every chance to lighten everything aft the wing tube - tailwheel etc., then - if it gets nose heavy, change the landing gear to 2024 T3 in 3/16" thick, 1/2 as wide as original gear.
My plane flew very well with the 80
we shifted to the 100 NG as soon as one was available .
The performance difference is not a bunch over a TUNED PIPE 80 single.
but the weight stays further forward.
The plane shown on the RC Showcase opening page, is this same plane.

It is a very good performer.

flier

My Feedback: (7)

Dick
Thanks for you insight on this matter.
Would you use the KS-95S-4 or the KS-89S-4 ?
One being sized for 100cc the other for 85cc.
Both are front inlet / rear outlet smokers.


Bended outlet 90°
External-Aluminium-muffler
with integrated smoker

Part # 89S-4 95S-4

L. 300cm 280cm
Inlet 30cm 30cm
Outlet 18cm 20cm
Diam. 65cm 75cm
Weight 280g 320g

I was thinking that the 95S-4 would be the better choice,
being shorter (with a larger Diam.) to move the weight forward more.

Would the larger volume be less tricky to tune?

Asking to learn

rmh

I hae not run the slightly larger one -but don't see a problem-unless it won't clear the gear - we used a 60 mm dia can.which is a copy -I think - no longer available I don't see either beig trick to tune - allow for 11-12" for header .
You will have to angle the can slightly - to not hit the wing tube -I think.

flier

My Feedback: (7)

Dick

A grear big THANK YOU for all the info.

Thats a great shot of the header taken in cowl!

If you were to build a 35%WH again, would you use the 80 or go for a 100 twin?

How would you rate the preformance of your WH35% using the 80?

rmh

I would opt for a 100 if I was doing competition.
Flying the one I had - Brian Copfer won the SW IMAC Championship.
The 80 on a tuned setup is a good Sportsman machine but I like more power for Unlimited class stuff.
The 80 is a favorite of mine - I haved used it in a number of models and for my own tastes, I like to have it in a plane under 200 squares and under 25 lbs
Remember tho - We do most of our flying at 4500 ft elevation.