ESE's works engine tuner

[wobbly]

The answer to your question regarding power range in the direct drive kart engine application is surprisingly simple.
Its the perforated rear cone surrounded by a resonant volume, ending in a flat plate end that also just happens to have the stinger in it.
Neels finally nailed down the sim operating mechanism, after alot of email back and forth and hair tearing out.

I discovered the effectiveness of each element in the design many years ago, after doing nothing but build and dyno testing pipes for our classes of the KT100 Yamaha.
This was a solid 6 months of doing nothing else by trial and error.

The mechanism is straight forward, at low rpms the perforated rear cone, and the non resonance of the " muffler " volume, allows most of the advancing wave front
from the diffuser to pass thru almost unhindered.
This wave is then bounced off the end plate, at a much longer tuned length than that of the rear cones.
As rpm increases, the rear volume gradually begins to resonate , and eventually the " holes" almost disappear and the rear cone starts to work in its effective tuned length range.

I tested every single 100cc direct drive pipe available on the planet , as the pipe and header was open in our KT100 classes.
The pipe I finally developed was far superior in every part of the powerband, from around 6000 to 16,000 rpm
It had a fully tapered header, with 3 diffuser cones ( the first being the steepest ) and a two part rear cone , the first one had no perforations.
I hand cut and built around 2000 of those things , winning every class title available for over 10 years.

The Yamaha class is redundant now , so there will be pipes lying around doing nothing under benches - I dont have the .dxf pattern files I eventually drew up, long gone on an old Win 7 hard drive.
I am sure the laser guys will still have the files , but getting a sample should be easy.

Edit - re the intake length , there is no such thing as too short - the 30mm carb on the TM125 KZ has the manifold recessed into the reed block , just to loose 3mm.

[ApolloMotoMoto]

(...)

I discovered the effectiveness of each element in the design many years ago, after doing nothing but build and dyno testing pipes for our classes of the KT100 Yamaha.
This was a solid 6 months of doing nothing else by trial and error.

(...)

I tested every single 100cc direct drive pipe available on the planet , as the pipe and header was open in our KT100 classes.
The pipe I finally developed was far superior in every part of the powerband, from around 6000 to 16,000 rpm
It had a fully tapered header, with 3 diffuser cones ( the first being the steepest ) and a two part rear cone , the first one had no perforations.
I hand cut and built around 2000 of those things , winning every class title available for over 10 years.

The Yamaha class is redundant now , so there will be pipes lying around doing nothing under benches - I dont have the .dxf pattern files I eventually drew up, long gone on an old Win 7 hard drive.
I am sure the laser guys will still have the files , but getting a sample should be easy.

I dont suppose you had a "name designation" for this pipe you came up with so I can search for it?

I just started looking around at KT100 pipes, and well, damn. There are a LOT of them.

I have been thinking about it for a while, but the itch to slap a KT100 pipe on our Motorized Bicycle engines is getting stronger.

At some point in the not-to-distant future I will begin using EngMod2T to develop this package even further. When that time comes I will have a lot of technical questions about how to design a pipe to achieve this effect.

Until that day comes, I would love to try the pipe you came up with

[wobbly]

The pipe was sold world wide thru my Wobblypipes company name , but mostly in NZ.
The name for it became " Wobbly 3 Cone".
You have to be careful as many classes used centrifugal clutches - a very different animal altogether.
I will ask around the kart guys and see if I can find one hiding in a corner.

[crbbt]

I am guessing there too many other approaches available on a GP bike to use a perforated rear cone?

[katinas]

Interesting comparison of flow direction through different A, B and C. Experiments with Vector tester developed by Dr. Jaros in mid 90, from Brno University of Technology. Wobbly often mentioned, that they helped to develop Yamaha GP cylinders.
Flow from very narrow A, boost short circuiting.
Less steeper flow from C makes "saltos" and goes longer way.

[wobbly]

crbbt - the perf rear cone setup is only suitable for direct drive single gear applications. It has a huge power range capability , all generated at the expense of power numbers around peak Hp
Not needed at all in classes with a gearbox.

[diesel pig]

crbbt - the perf rear cone setup is only suitable for direct drive single gear applications. It has a huge power range capability , all generated at the expense of power numbers around peak Hp
Not needed at all in classes with a gearbox.

So you wouldn't do a perf rear cone set up on a engine set up for a Enduro Dirt Bike?

[SwePatrick]

I hate beeing out of control, so let´s take control!
I install a laser height sensor on my Maxxecu controlled Yamaha TZR250 '100whp' engine.

This little device will help me control the engines performance in the important first 60ft on the 1/8 mile.

Why?
The bike´s dryweight is only 68kg´s and with almost 100whp it might rise so fast you can´t control it, electronics are faster in reaction than the human brain

https://youtu.be/-VSn3YosP0k

[wobbly]

Mr Pig , the Enduro engines are easily setup with a " normal " pipe to operate perfectly for that application.
Very hard I would imagine to fit the large diameter long muffler " tube " onto a bike chassis.

[diesel pig]

Mr Pig , the Enduro engines are easily setup with a " normal " pipe to operate perfectly for that application.
Very hard I would imagine to fit the large diameter long muffler " tube " onto a bike chassis.

Fair enough, I was just trying to think of something 2 stroke related that would benefit from a wider rev range. I am sure I read somewhere that 2S enduro bike's benefited more from the induction of exhaust power valves more than 2S MX bikes.

[Pagi]

Interesting comparison of flow direction through different A, B and C. Experiments with Vector tester developed by Dr. Jaros in mid 90, from Brno University of Technology. Wobbly often mentioned, that they helped to develop Yamaha GP cylinders.
Flow from very narrow A, boost short circuiting.
Less steeper flow from C makes "saltos" and goes longer way.

Woobly,

Can you give us your opinion, comments, advice on these drawings?...............

[wobbly]

I have spent literally hundreds of hours studying the flow vector patterns from a Czech CNC flow visualization rig.
And I think I have made the point that the Japanese head race team engineer said to me in 2000 ( where his 250,s blitzed the GP championship ) that he didnt
need a dyno anymore as the flow patterns told him all he needed to know in predicting the power band shape and efficiency.

The first point is that this cylinder has normal stagger , but this testing method is only showing the raw result of flow at BDC with a depression at the Exhaust port.
No account is being taken of the flow reversion happening at TPO, that helps to separate the flow columns in the time domain and thus helping to maintain the individual flow column coherency.
Lastly showing each port individually is helpful but again this neglects the interaction effects of each column with another's.

The first LH ( MOD ) flow column is much more coherent, and would be very efficient at scavenging Exhaust residuals in the area in front of the Exhaust port.
But this positive effect is offset by the large amount of direct short circuiting taking place.
In my opinion this port needs angling backward and upward more thus scavenging higher up the wall area above the Exhaust port - with the inherent advantage of also reducing the short circuiting.

The second ( Middle ) stock column coherence is absolute crap , but this is the only regime with any scavenging of the dome residuals.
This deficiency is somewhat helped by the RH ( MOD ) boost flow in this example. The middle MOD roof should be flatter to help prevent disturbing the Boost scavenging of the cylinder upper and head dome area.

Lastly the boost ( MOD ) roof angle should be angled slightly more upward , as it has some good upper cylinder scavenging, but although the 360* loop will dramatically increase the loop time period, before entering the Exhaust
this flow across the head is " backwards ". Good head scavenging is seen dramatically in engines with a Toroid chamber. The flow attached to the rear wall then turns directly across the chamber,
and this is then masked by the low plugs downward intrusion into its path. This shows as a shadow of dark burnt on oil from the plug, out to the wall above the Exhaust. This negative effect can be ameliorated
by using small 10mm race plugs , and this has been proven to make more power in Snow Ski World Champ engines.

I think that all my comments would point toward this cylinder needs modifying in the axial and radial angles to conform more to that developed by Jan with the RSW/RSA - even aside from the stagger.
But although Jan has made the comment that he didnt see any advantages in using the vector flow visualization method , I think Yamaha , and by extension Bud Askland who's work on Raineys multi champ winning
cylinders for Team Roberts would agree to disagree.

[Pagi]

I have spent literally hundreds of hours studying the flow vector patterns from a Czech CNC flow visualization rig.
And I think I have made the point that the Japanese head race team engineer said to me in 2000 ( where his 250,s blitzed the GP championship ) that he didnt
need a dyno anymore as the flow patterns told him all he needed to know in predicting the power band shape and efficiency.

The first point is that this cylinder has normal stagger , but this testing method is only showing the raw result of flow at BDC with a depression at the Exhaust port.
No account is being taken of the flow reversion happening at TPO, that helps to separate the flow columns in the time domain and thus helping to maintain the individual flow column coherency.
Lastly showing each port individually is helpful but again this neglects the interaction effects of each column with another's.

The first LH ( MOD ) flow column is much more coherent, and would be very efficient at scavenging Exhaust residuals in the area in front of the Exhaust port.
But this positive effect is offset by the large amount of direct short circuiting taking place.
In my opinion this port needs angling backward and upward more thus scavenging higher up the wall area above the Exhaust port - with the inherent advantage of also reducing the short circuiting.

The second ( Middle ) stock column coherence is absolute crap , but this is the only regime with any scavenging of the dome residuals.
This deficiency is somewhat helped by the RH ( MOD ) boost flow in this example. The middle MOD roof should be flatter to help prevent disturbing the Boost scavenging of the cylinder upper and head dome area.

Lastly the boost ( MOD ) roof angle should be angled slightly more upward , as it has some good upper cylinder scavenging, but although the 360* loop will dramatically increase the loop time period, before entering the Exhaust
this flow across the head is " backwards ". Good head scavenging is seen dramatically in engines with a Toroid chamber. The flow attached to the rear wall then turns directly across the chamber,
and this is then masked by the low plugs downward intrusion into its path. This shows as a shadow of dark burnt on oil from the plug, out to the wall above the Exhaust. This negative effect can be ameliorated
by using small 10mm race plugs , and this has been proven to make more power in Snow Ski World Champ engines.

I think that all my comments would point toward this cylinder needs modifying in the axial and radial angles to conform more to that developed by Jan with the RSW/RSA - even aside from the stagger.
But although Jan has made the comment that he didnt see any advantages in using the vector flow visualization method , I think Yamaha , and by extension Bud Askland who's work on Raineys multi champ winning
cylinders for Team Roberts would agree to disagree.

Wobbly, Thank you for all this information.

[TZ350]

.
Two Stroke Stuffing

https://youtu.be/kIcb7x7NytQ?si=sGmQArawZSWfqeqW

Supercharged Nitro 50cc two stroke startup running.

[SwePatrick]

Everone want´s more speed...
So, go the easy way with boost!!
Shuuututututututuuu!!!

A VERY simplified guide: