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FastFred
22nd June 2009, 19:41
where is Thomas?....one monment he is all things amazing, then he is only the guy who makes jigs for balancing....

Am I the only one? that thinks Thomas's ideas like that simple practical jig shows real experience. You talk a lot SS90 but no usefull tools, jigs or fixtures from you!

SS90 You don't add any credibility to yourself buy continuously rubishing Thomas, You talk big but in his quiet way he's actually doing and posting things and with his simple workable ideas, looks like somone who has been there, done that.

I was surprised that you couldn’t tell us which was heavier, the counter balance or reciprocating weight, it seemed a fair enough question. Thomas answered it easily and with pictures.

SS90 your making yourself look a looser with your carping, a disfunctional wannabe!

It's been slim pickings so far, but if you have anything, and can leave game playing and personal attacks out of it, we all would be keen to hear what you have to say.

.

SS90
22nd June 2009, 21:49
Here is a picture from a trip to "Nam" a few years ago, they tell me this shop is better now..... they have shoes.

SS90
22nd June 2009, 21:53
Haha must be the "I can't be bothered with childish bullshit side"

And just was does that entail?

Signing on in different names and destroying peoples threads?

Call them "terminally stupid" etc?

Giving imaginary people credit for other peoples suggestions?

I have been giving out some genuine experience based advise (for no reason other than to improve the level of two stroke buckets , and been treated like crap for it.

But yea, thanks for your mature input there mate.

You sure showed me.

FastFred
22nd June 2009, 22:08
.

SS90 I guess it's "your a looser" then with your carping, you'er just a disfunctional wannabe!.

.

F5 Dave
23rd June 2009, 09:21
Here is a picture from a trip to "Nam" a few years ago, they tell me this shop is better now..... they have shoes.

Over there stealing ideas huh?

F5 Dave
23rd June 2009, 09:26
.

SS90 I guess it's "your a looser" then with your carping, you'er just a disfunctional wannabe!.

.

FFS! "You're a loser" not "Your a loser" Almost get it right later in the sentence but spell it wrong.

When did they stop teaching Grandma at skewl?

SS90
23rd June 2009, 09:48
Over there stealing ideas huh?

Erm ,not quite.

The "workshop" pictured makes reproduction parts (headsets and such like)

They made 100 exhausts for us from a sample.

It wasn't a particularly good exhaust, but it sold well.

The Chrome is surprisingly durable.

They churn out copies by the thousands there (expansion chambers, every thing)

This particular workshop recently purchased water forming equipment and have started to copy some new designs (that are hand made in Europe) and bang out water formed copies for about €110

It's a sore point with quite a few people.

Unfortunatly the mufflers are "jam packed" with "pink bat" material and you need to repack them, but after that it's still a cheap pipe.

SS90
23rd June 2009, 09:51
This is an original.

I think retail is €320

Buckets4Me
23rd June 2009, 17:34
$900 ouch
but there is some good work gone into it
would hate to see how long it would take me to make that :crazy:

F5 Dave
23rd June 2009, 17:44
labour in Europe is always going to be high, obviously they can set up & cut for a run & jig saving huge amounts compared to fitting to a scrooter for the first time under bodywork, but you are buying the development & for a pipe with muffler that is quite reasonable.

Buckets4Me
23rd June 2009, 18:00
ye I know I would hate to try and do that and make money
far to much work as a one off
still a nice looking pipe thow

makes what I paid for my chamber (rg50) look not so bad

speedpro
23rd June 2009, 20:26
This is an original.

I think retail is €320

The original would be a mission but then laser cut patterns, good jig, big box of slip-joints and mounting flanges, and a decent bloke with a TIG, and I can't see more than .5 day putting them together.

I'm no expert in these things but did spend a year or so recently working in a shop that did a lot of sheet metal.

I bought a "power bomb" brand pipe, actually I got it after a mate bent one of my rotary files, for a NSR125 I think. It had a hydro formed tapered head pipe and a mismatched junction to the diffuser section but it worked a treat. It would have cost something around $50-70 I think. Stupidly cheap considering what it takes to make a pipe from scratch.

Yow Ling
23rd June 2009, 20:50
Is this Thomas ?

k14
23rd June 2009, 20:53
Is this Thomas ?
Whoever it is, he looks like a big dick :bash:

Kickaha
23rd June 2009, 20:55
Whoever it is, he looks like a big dick :bash:

He could do with a few less pies

SS90
23rd June 2009, 21:49
The original would be a mission but then laser cut patterns, good jig, big box of slip-joints and mounting flanges, and a decent bloke with a TIG, and I can't see more than .5 day putting them together.

I'm no expert in these things but did spend a year or so recently working in a shop that did a lot of sheet metal.

I bought a "power bomb" brand pipe, actually I got it after a mate bent one of my rotary files, for a NSR125 I think. It had a hydro formed tapered head pipe and a mismatched junction to the diffuser section but it worked a treat. It would have cost something around $50-70 I think. Stupidly cheap considering what it takes to make a pipe from scratch.

About 2 years ago, such pipes where about €600 (Yep $1200 NZ)

Competition from cheap copies dragged that down.

The interesting thing is the money these guys made from such "handmade" copies was invested in (like one "workshop") in water forming equipment.

Now they are still copying, but the quality of the water formed chambers is incredible (and cheap)

The first series of water formed chambers was total crap, but over two years they got it right.

Of course it is supply on demand, but the sad bit is the guys who design the original get little to no money.

There is a recent water formed copy that rivals the best hand made chamber I have seen. and at €110 (landed, at your door) it is hard for the customers to say no.

But it is a copy, there is nothing original about it.

That is the important difference.

The same is true for cylinders (cast iron lined only at this stage, but in a few years, I am sure Nikasil will be able to be produced) as well as Cylinder heads....

All straight copies of the originals.

Buddha#81
23rd June 2009, 22:20
Is this Thomas ?


Nah....he looks like an ugly fook.

SS90
23rd June 2009, 22:25
Here is a water formed copy of the first pic.

The muffler is taken from another pipe design (which actually was taken from the AG Bell book), and the slip joint is taken from a "Falc" exhaust

Just an amalimation of 3 designs, but the actual expansion chamber dimensions are the same as the first pic.

This first hit the scene here about a year ago.

6 months after the original.

Buddha#81
23rd June 2009, 22:31
is this Thomas?

Buckets4Me
24th June 2009, 08:05
Is this Thomas ?

Didn't know Thomas was into 4 stroke dirt bikes
must be multy talented
:woohoo:

next you will tell me he can do scouters to :scooter:

F5 Dave
24th June 2009, 09:26
Ohh can I play?

Here's Thomas, I think.

Note the GP testbike in the foliage

Buckets4Me
24th June 2009, 09:49
Ohh can I play?

Here's Thomas, I think.

Note the GP testbike in the foliage

looks like an early attemp at dirt bike racing

F5 Dave
24th June 2009, 10:00
Yes with a GP100 resplendent in purple with newer technology Stamped Metal exhaust. Note thick Vietnamese foliage & I think that is a Tiger just hidden in the shadows to the right.

Buckets4Me
24th June 2009, 10:16
sorry wrong !!!!!


we got Thomas off the BBC (have to lend him back every now and again as they are still filming)

and I now have a photo for you 132922

Buckets4Me
24th June 2009, 10:22
chased by Ninjas in his early years he learnt how to make Bikes go fast so he could survive (bikes being smaller again than his car)

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F5 Dave
24th June 2009, 10:23
Oh please don't change this into some car thing.




Besides Tigers attack white, you'd never survive in that ghey get up.

Buckets4Me
24th June 2009, 10:36
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aparently you dont survive telling people who you are either

more evidence that Thomas is at least related to the Stig
as taken from Winepeg and refering to Top Gear

The Vietnam special featured the 'Stig's Communist cousin' a red-jumpsuit clad motorcyclist, who set lap times on the presenters' bikes. Previously seen in the series 12 preview montage, the scenes were deleted from the broadcast, but the footage of the 'Communist cousin' was included in the extra materials of the DVD.

Yow Ling
24th June 2009, 18:47
Erm ,not quite.

The "workshop" pictured makes reproduction parts (headsets and such like)

They made 100 exhausts for us from a sample.

It wasn't a particularly good exhaust, but it sold well.

The Chrome is surprisingly durable.

They churn out copies by the thousands there (expansion chambers, every thing)

This particular workshop recently purchased water forming equipment and have started to copy some new designs (that are hand made in Europe) and bang out water formed copies for about €110

It's a sore point with quite a few people.

Unfortunatly the mufflers are "jam packed" with "pink bat" material and you need to repack them, but after that it's still a cheap pipe.

So lets get this right, you exploited the low labour cost in Veitnam to get a pipe copied 100 times, then they had the audacity to use your money to reinvest in their business so they could manufacture to higher standards, how dare they ! Doesnt Lomas get his pipes made in Croatia or some other low cost country.

What about those sneaky bloody Indians, learning how to speak forigen languages then pretending to be bank or power company helpful people.

Get over it, stuff gets copied all the time, in one of your earlier pots you talked about copying a cylinder and improving it, thats just the same as what happens with the pipes. looks like the copy is now superior to the expensive european version, i guess the euro one needs to be improved to stay ahead of the game. Also if the Veitnamese incorporate designs and innovation from Bells book the product is not the same as the original. you need to get over your hatred for Veitnamese, Germans wernt always flavour of the month.

SS90
24th June 2009, 22:10
So lets get this right, you exploited the low labour cost in Veitnam to get a pipe copied 100 times, then they had the audacity to use your money to reinvest in their business so they could manufacture to higher standards, how dare they ! Doesnt Lomas get his pipes made in Croatia or some other low cost country.

What about those sneaky bloody Indians, learning how to speak forigen languages then pretending to be bank or power company helpful people.

Get over it, stuff gets copied all the time, in one of your earlier pots you talked about copying a cylinder and improving it, thats just the same as what happens with the pipes. looks like the copy is now superior to the expensive european version, i guess the euro one needs to be improved to stay ahead of the game. Also if the Veitnamese incorporate designs and innovation from Bells book the product is not the same as the original. you need to get over your hatred for Veitnamese, Germans wernt always flavour of the month.

Interesting point.

The thing I take exception to is not the "Vietnamese" it's more the fact that every time I mention something "Thomas knew all about that" (etc), yet why didn't Thomas do all this before I mentioned it?

It's certainly not "Ego" from my end (other people see it the same way, it's not just my opinion)

I make no bones about starting with other peoples designs and improving them. Its how we all learn.

Straight out copying them (under the same brand name) is pretty crap when it's not big businesses designing them, it's quite often one person, who ends up making no money.

I never mentioned any of this until Teezee gave Thomas the credit for suggesting he took some design cues from an Rs125 cylinder.

I had done that months before.

Don't think that is childish of me to mention it, it's just stating a fact.

I'm not doing this for personal glory, ( I would have simply declared who I was if I wanted personal glory,) I was happier with annonimity.

The idea of me even continue to post was that it seemed the more I wrote, the clearer the concepts became to me (like reaffirming what I had learned)

But it was a bit of a poke in the eye. considering how many hours I had spent at the key board (trying several times to carefully point out where they where going wrong, not in an "I told you so" way)

When Teezee reported that his "high tuned" engine was putting out so much power it was over heating, but turned out to be making the least power (15HP), I found no temptation to ridicule him, only offering him encouragement.

Like I said, the cylinder I developed started out as a totally plagerised item (wrapped in a different looking Aluminium skin)

Now it's not (plagerised), but, using methods and ideas I have written about on this forum (not once did I "google" anything, I learned all from books, coupled with my experience with two stroke race bikes, and some frank words from people in the industry here.)

I quickly learned that it's actually FAR FAR easier to start from scratch (once you know the basics) as far as port layout goes, rather than modifying an exsisting design.

The two big advantages are you can set the correct blowdown time as well as easily make your transfer angles what you want before you fit the new liner, rather than having to make too many compromises.

I wrote months ago what things to pay attention to, not for personal glory, but to help people who wanted to make their two stroke bucket faster.

I see Teezee now advocates around 50% balance factor (previously he was advocating 60%... these are all things I have mentioned, and all things I have learned through experience, none of which are "secrets", but previously he hadn't mentioned.

The first thing I read in the ESE thread that made me decide to post was Teezee decaring "what brings the power" (Ie what has an effect in reality, not just theoeretically), which was a question I had previously asked myself so many times, (I identified with the statement ) and it is only experience that teaches you that.

There seems to be a "giggle factor" that it is scooters I work with, don't forget that it's just an aluminium crankcase with a two stroke cylinder on top, if you make 25 PS with a Japanese crankcase, you can do it with a Vespa crankcase.

Pay no attention to the frame. (They are handle WORSE that you can imagine)

Oh, and much like my job is not just expansion chambers and dyno's (the fun parts), living over here is not all Lederhosen and Bier.......many people here deserve the reputation.....but there are some VERY clever tuners here, and it does have it's advantages.

Buckets4Me
25th June 2009, 06:47
Thomas has never coppied anything you posted

he did get a few ques from you but that was all

Tz350 finally got to a dyno so he had some hard facts thanks SS90 again
he had been a bit lazy


BUT YOU DO HAVE AN EGO problem and a big one from what I seen

and sugesting that people like Viatnemess boys a little to much was not
the done thing

and you did never let us know that answer about crank ballancing :P

but Thomas did :buggerd:

SS90
25th June 2009, 07:10
Interesting,

It's one thing to question something, but good old "Bucketracer" was making an absolute fool of himself, making personal comments that where totally uncalled for.

I was quite happy for people to follow what I was writing (that's why I wrote it)

Just got too much when other people where handed the credit, coupled with childish remarks, day after day.

........And Thomas has never written anything!

That's my point!

Buckets4Me
25th June 2009, 12:16
You seem to have it in for some one that has NEVER said anything nasty about you at all

he did answer a few questions people had and gave good descriptions etc

and when you looked like you didn't have the answers he piped up
(witch was the same time you started getting realy hot under the collar)

I can only put 1 and 2 together and guess that it makes 5

I have found it easier to follow what Bucketracer had to say
and YOu never seem to let up on the attacks so cant Blame him for
giving you shit :argue:

and it is YOU who has let this thread turn into one big JOKE!!!!

so HA HA and HA on you

stop worring what they say and get on with showing us where we can do better

ps I can see why they call this the midnight wanker CLUB with all the shit talk from BOTH SIDES

makes everyone look like a bunch of school boys

pps I would still like to get my hands on that gp machine and rip the engine out :rolleyes: the BLING alone would help me win races :lol:

speedpro
25th June 2009, 20:18
pps I would still like to get my hands on that gp machine and rip the engine out :rolleyes: the BLING alone would help me win races :lol:

I'm pretty sure it doesn't have THAT much bling :laugh:

SS90
25th June 2009, 21:01
You seem to have it in for some one that has NEVER said anything nasty about you at all

he did answer a few questions people had and gave good descriptions etc

and when you looked like you didn't have the answers he piped up
(witch was the same time you started getting realy hot under the collar)

I can only put 1 and 2 together and guess that it makes 5

I have found it easier to follow what Bucketracer had to say
and YOu never seem to let up on the attacks so cant Blame him for
giving you shit :argue:

and it is YOU who has let this thread turn into one big JOKE!!!!

so HA HA and HA on you

stop worring what they say and get on with showing us where we can do better

ps I can see why they call this the midnight wanker CLUB with all the shit talk from BOTH SIDES

makes everyone look like a bunch of school boys

pps I would still like to get my hands on that gp machine and rip the engine out :rolleyes: the BLING alone would help me win races :lol:


Perhaps you would be well served to re-read this thread in it's entirety..... it paints a clear picture of what started from where.

I (and others) fail to see how discussing minimum values for primary compressions (a series of posts that was destroyed by Bucketracer) and blowdown times (none of which had been discussed before on these threads, but are critical in tuning) indicates I have a problem with anyone.

The sad thing is I never was able to finish posting my results.

The people who where taking a serious interest in that are the ones that miss out.

As a result I won't be sharing my findings on this site.

Or for correct blowdown times either.

Everytime I mentioned something "Thomas said" was the answer.

Thomas has said nothing.

One day, "Thomas said" All cranks where 60% balance factor, (I said 52% is condidered correct for a high revving two stroke)

3 days later, Team ESE announce "around 50%"

As far as I am concerned team ESE are responsible for the childishness/ego primping.



I was posting my own findings not referring to websites.

Buckets4Me
25th June 2009, 21:52
One day, "Thomas said" All cranks where 60% balance factor, (I said 52% is condidered correct for a high revving two stroke)

3 days later, Team ESE announce "around 50%"



BULLSHIT :lol:

F5 Dave
26th June 2009, 16:46
. . . .

The sad thing is I never was able to finish posting my results.

The people who where taking a serious interest in that are the ones that miss out.

As a result I won't be sharing my findings on this site.

Or for correct blowdown times either.

. . .

Oh boo hoo. Won't someone think of the children.

Melodrama of your own choice.

- - - -

Post 279 almost sounded stable & reasonable. Who the hell wrote that post?
The above post shows your complete Jekyll & Hyde persona. SS90 Vs Neil.

If you had written like that from the start no one would have thought, Gee that chap is a complete & utter wanker & none of this would have happened. There may have been some challenge to some ideas & healthy discussion, but no outright disrespect on both sides.

But I'm sure your attitude has & continues to get you into fruitless arguments so I don't expect you to learn or modify your behavior one iota.

SS90
26th June 2009, 21:43
Oh boo hoo. Won't someone think of the children.

Melodrama of your own choice.

- - - -

Post 279 almost sounded stable & reasonable. Who the hell wrote that post?
The above post shows your complete Jekyll & Hyde persona. SS90 Vs Neil.

If you had written like that from the start no one would have thought, Gee that chap is a complete & utter wanker & none of this would have happened. There may have been some challenge to some ideas & healthy discussion, but no outright disrespect on both sides.

But I'm sure your attitude has & continues to get you into fruitless arguments so I don't expect you to learn or modify your behavior one iota.

Healthy discussion is fine, constant childish nonsense is another.
Have you even bothered to read every post in this thread, or do you just chose to ignore the antagonism from the ESE "team"

Well, let's just see how the scroll diode thing goes, 1971? I can't imagine why GP teams don't use them today.

It's interesting to read about such history of development, but who uses it today/when did it see production?

Skunk
27th June 2009, 00:00
Well, let's just see how the scroll diode thing goes, 1971? I can't imagine why GP teams don't use them today.
Even I can see why GP teams don't use scroll diodes... Can you SS90? I'll explain it for you if you can't can tell me why they don't. I'll give you a clue - it's not because they don't work.
I can even guess why it's not used in production bikes. Can you?

Get back to me when you've finished your study and I'll mark your answers. There's a good boy.

If you don't like my tone you shouldn't have used it on me.

Skunk
2nd July 2009, 22:01
Still studying the answer huh?

B.Crump
14th July 2009, 20:45
I have two (and I've watched TZ350's thread with interest) - one is a cast iron rotary Kawasaki F6 and the other an alloy rotary Suzuki TF125. At present both are in the barely running stage so a little early to post specs. But I will.

i am trying to get as much as possable out of a tf125 im just doing a top end rebuild with 0.5mm ova size piston i have modafyed a kx125 exorst to fit and cant wait to try it do you know of any other mods i can do? cheers

F5 Dave
14th July 2009, 21:11
You definately ned to polish the head, try stripeing it with striper & then polishing it with sandpaper & worn out paper until it is as shiney as possible, even deep into the fin grooves then tri autosoul polish

koba
14th July 2009, 21:47
i am trying to get as much as possable out of a tf125 im just doing a top end rebuild with 0.5mm ova size piston i have modafyed a kx125 exorst to fit and cant wait to try it do you know of any other mods i can do? cheers

Take it out of the gokart.

SS90
16th July 2009, 07:56
You definately ned to polish the head, try stripeing it with striper & then polishing it with sandpaper & worn out paper until it is as shiney as possible, even deep into the fin grooves then tri autosoul polish

Combine the above technique with a copper combustion chamber (all the rage in high performance two stokes, perhaps even a copper finned base gasket) and exhaust pipe and port specs from a 1970's book, and you got your self a weapon.

Either that, or you could read a book called "the two stroke tuners hand book" By Gordon Jennings.....

It's a really good place to start, many top tuners have recommended it to me, it is well written, and while SOME aspects are dated, if you read it carefully, it is a little "ahead of it's time"

B.Crump
16th July 2009, 18:37
thanx ill try thos things out and see how it goes cheers :)

B.Crump
17th July 2009, 20:14
has any one supercharged a 2 stroke?

koba
17th July 2009, 21:00
Yup, Two stroke diesels have to be supercharged.

Yow Ling
17th July 2009, 21:24
has any one supercharged a 2 stroke?


DKW and NSU had them

Skunk
17th July 2009, 22:31
DKW and NSU had them
Mine's supercharged - it has a chamber.

SS90
20th July 2009, 05:02
Mine's supercharged - it has a chamber.

I'm not too sure that I would subscribe to an expansion chamber being a "supercharger"........

A supercharger is essentially a compressor that forces air into an engine......An expansion chamber doesn't do this.

Are you referring to the expansion chamber "evacuating" the cylinder to below atmospheric pressure, assisting the positive pressure from the crankcase below, thereby increasing the delivery ratio?

Because that's not a supercharger.

HOWEVER.....

This very effect (and correct understanding of which) brings up an important part of expansion chamber design.

There are plenty of computer programmes available that will design a pipe for you, using just port time areas,RPM intended etc.

My experience is that all these programmes that only require a small amount of data (specifically in relation to exhaust port only) return essentially the same expansion chamber..... (dated)

Obviously, the more you spend on the software, the better the expansion chamber you end up with....but you have to "answer the right questions" this software asks......it's quite complicated.

There are alot more factors you must consider when designing an expansion chamber.

That is the difference between an expansion chamber designed in the 70's, and one designed recently.

It was mentioned (F5 Dave) that an old designed cylinder (I would personally make the broader statement of old designed "engine" opposed to just "cylinder"), does not work ideally with a "new" (modern) pipe design.

That is 100% correct, and there are good reasons for it.

Think of it as trying to connect your 1981 Atari to a flat screen, and expecting it to be a PS3

Buckets4Me
20th July 2009, 07:06
A supercharger is essentially a compressor that forces air into an engine......An expansion chamber doesn't do this.

Are you referring to the expansion chamber "evacuating" the cylinder to below atmospheric pressure, assisting the positive pressure from the crankcase below, thereby increasing the delivery ratio?

Because that's not a supercharger.


I thought that the chamber also helped by sucking fresh charge into the chamber then forcing it back into the cyliner using the presure wave from the exaust bouncing of the rear cone of the chamber ???

well I guess I was wrong

bucketracer
20th July 2009, 08:13
I'm not too sure that I would subscribe to an expansion chamber being a "supercharger"........

A supercharger is essentially a compressor that forces air into an engine......An expansion chamber doesn't do this.

Are you referring to the expansion chamber "evacuating" the cylinder to below atmospheric pressure, assisting the positive pressure from the crankcase below, thereby increasing the delivery ratio?

Because that's not a supercharger.




An expansion chamber which has been properly matched to an engine will effectively supercharge it.

This is done by pressing extra mixture back in through the exhaust port with the force of a returning pressure wave in a resonant exhaust system.

How this happens is explained very well by:- http://scooter.wikia.com/wiki/Expansion_Chamber

Pic-1 The positive pressure pulse leaves the exhaust port As the mixture is combusted inside the cylinder, the piston is forced downward and opens the exhaust port. The force of the exhaust pressure leaving the cylinder creates a positive pressure pulse as it moves out into the expansion chamber.

The time between exhaust port opening and and transfer port opening is called "exhaust lead". Exhaust lead allows the high-pressure exhaust gases in the cylinder to blow-down (reducing pressure) before the transfer port opens. If this doesn't happen, exhaust particles may back-flow into the crankcase and contaminate and heat the incoming fuel/air charge, thereby robbing the engine of power.

Pic-2 Negative pressure waves The inertia of the out flowing exhaust particles out into the divergent code creates negative pressure waves and a strong partial vacuum (about minus 7psi) near the still opening exhaust port shortly after the transfer port has opened. In addition to the sucking out tail-end exhaust gases, these suctions cause fresh air/fuel mixture to be sucked through the transfer port into the combustion chamber.

Pic-3 Positive pressure waves The remaining energy in the negative pressure wave continues through the pipe and is reflected off the convergent cone at the rear of the unit and returns to the engines exhaust port. During this point, the negative pressure will actually end up pulling extra fresh gas and air into the header of the expansion chamber.

Pic-4 Supercharging through the exhaust port Finally just as the transfer ports inside the cylinder are closing, the returning positive pressure wave compresses the extra fuel and air mixture back into the cylinder through the exhaust port. The cylinder now contains the extra mixture for the next combustion--effectively supercharging the engine and increasing efficiency and performance.

.

SS90
20th July 2009, 08:34
I thought that the chamber also helped by sucking fresh charge into the chamber then forcing it back into the cyliner using the presure wave from the exaust bouncing of the rear cone of the chamber ???

well I guess I was wrong

Hmmm,

Sort of.

from what you write, I am taking it that you see that the expansion chamber "deliberatly" draws fuel in from the combustion chamber into the chamber, them "pushes it back in" when it is needed.

That's how I interpret your post anyway.

Because the fuel sucked into the chamber is not a deliberate thing at all........ It's incredibly wasteful, and engineers spend millions of dollars trying to stop that very problem.

If it was beneficial, fuel injected two strokes would have been on the market 20 years ago.

The fact is, because the fuel gets into the chamber (and only a percentage manages to get forced back in) is the reason for such poor emissions in the first place.
While it is quite easy to get lost in terminology, in a simplistic form (which is better) you sort of grasp the concept.

But, that's not a supercharger either.

This particular "effect" you can take advantage of, certainly does not "super charge" a two stroke engine.

Essentially, (trying not to "overcomplicate" things) The negative pulse waves (caused by the expansion chambers diffuser, the length and angle of which dictate the amount of pressure),along with the inertia of the exhaust gasses, "excavate" (suck I guess would be the best description) the cylinder (which is obviously something closer to atmospheric) to assist the positive pressure in the crankcase to get the air/fuel mixture into the cylinder.

Basically, the design of the diffuser (if it is designed correctly that is) significantly assists the pressurised crankcase in getting well compressed fuel into the combustion chamber.

Obviously, the exhaust port is open, and fresh good air/fuel mixture makes it's way into the expansion chamber (sometimes called "over scavenging")

As this good air/fuel mixture (importantly, along with the energy is traveling towards the pipe outlet, it must past through the convergent cone, causing a positive wave to return to the cylinder, pushing (some) of the "over scavenged" fuel back into the cylinder.

I too have seen people refer to this as "supercharging", but like I say I don't subscribe to that....... I see it as simply returning "overscavenged" burnable fuel to the cylinder.

It is for this very reason that companies like "Orbital" (just as one example) spend so much money and time developing systems that clear the cylinder of all burned gasses (injecting oxygen from the atmosphere is one way), BEFORE injecting the air/fuel mixture (AFTER the exhaust port is closed............... There by negating the effect of the returning pressure wave............

bucketracer
20th July 2009, 08:46
This particular "effect" you can take advantage of, certainly does not "super charge" a two stroke engine.

the convergent cone, causing a positive wave to return to the cylinder, pushing (some) of the "over scavenged" fuel back into the cylinder.

I too have seen people refer to this as "supercharging", but like I say I don't subscribe to that....... I see it as simply returning "overscavenged" burnable fuel to the cylinder.


However you squeeze extra air or air/fuel mixture into an engine above what it can normally aspirate for its self is supercharging.

You might not call this supercharging but the rest of the world does.

.

SS90
20th July 2009, 08:46
[QUOTE=bucketracer;1129314085].


An expansion chamber which has been properly matched to an engine will effectively supercharge it.

This is done by pressing extra mixture back in through the exhaust port with the force of a returning pressure wave in a resonant exhaust system.

How this happens is explained very well by:- http://scooter.wikia.com/wiki/Expansion_Chamber
QUOTE]
Hmmm,

Well, in my experience, not everything written on a single web page can be considered correct.

You are of course entitled to your opinion.

Like I say above, if it indeed an expansion chamber "super charges", a cylinder, then why has so much effort been expended to negate the need for the over scavenged fuel to be returned to the cylinder? (the "super charge" effect)............... the only reason expansion chambers are designed the way they are is to best compromise on the unique requirements of the intake/exhaust cycle.

Basically, the fuel that is returned to the cylinder (you say "supercharged") via the returning pressure wave is only there in the first place because it simply flows out the open exhaust port..........

With a system like Orbital's designs, they inject the fuel AFTER the exhaust is closed.

The expansion chamber design is somewhat different to what you would have for a carbed bike (though not dramatically, like I first expected)......... because you still want to take SOME advantage of the positive pressure.....but it is at a different time, and for a different duration than "normal"......because there is only compressed air to "escape" out the open exhaust port.

Personally, I don't agree with the writer of that particular "page" when it comes to the description of "supercharging".

I feel it is an important thing to note.

SS90
20th July 2009, 08:48
You might not call this supercharging but the rest of the world does. I guess they are wrong.

.

The "rest of the world" does not consist of a web page by an unknown author.

bucketracer
20th July 2009, 09:03
from what you write, I am taking it that you see that the expansion chamber "deliberatly" draws fuel in from the combustion chamber into the chamber, them "pushes it back in" when it is needed.

That's how I interpret your post anyway.

Because the fuel sucked into the chamber is not a deliberate thing at all........ It's incredibly wasteful, and engineers spend millions of dollars trying to stop that very problem.


Sucking extra air/fuel mixture into the exhaust and then ramming as much of it back as you can is most certainly a deliberat thing, its where the 2-stroke gets its power.

The pity is that it all does not get pushed back and this is where the 2-stroke gets its dirty reputation.

This is where DI Direct fuel Injection helps, as the fuel is injected into the cylinder after the supercharging effect has taken place. With DI no fuel is lost as its injected after the exhaust port has closed.

DI is a big advance, TerraRoot posted something about it on the ESE thread a couple of days ago.

.

bucketracer
20th July 2009, 09:05
The "rest of the world" does not consist of a web page by an unknown author.

Well, in my experience, not everything written on a single web page can be considered correct.

.

You are right about that.

A quick Google will turn up many descriptions of the 2-stroke/expansion chamber supercharging effect.

I do have more respect for opinion that is backed up by references, don't you.

.

SS90
20th July 2009, 09:17
Sucking extra air/fuel mixture into the exhaust and then ramming as much of it back as you can is most certainly a deliberat thing, its where the 2-stroke gets its power.



.

No it is not.

The fact the fuel makes it into the chamber is certainly NOT deliberate.

Why do you think that so much effort has been spend on Scavenge patterns?

The whole "scavenge Pattern" concept is to reduce the amount of fuel that gets out the exhaust port.

That's why a two stroke is called a "schürle loop" (closed loop).........

The whole idea is to keep as much fuel in the cylinder as possible, it looses alot of it's charge density when it travels from the crankcase, to the cylinder, out the exhaust port, into the chamber, then back into the cylinder..........

I don't agree that a two stroke "get's it's power" by returning overscavenged fuel into the cylinder.........

A two stroke that loses less fuel out the exhaust makes more power than one that looses more.

Regardless of how much of that overscavenged fuel is returned to the cylinder.

Like I say, Supercharging is something quite different.

B.Crump
20th July 2009, 09:27
i have put a expantion chamber on my one and iv just done a top end rebuld and it goes very well port matched .i couldnt get that far in to smooth all the surfaces is there a spectial tool i can get to get right in the motor?

but does ant one know if anyone has supercharged a two stroke bike? i kow people have turbo charged two strokes i have a book on it (old one)

bucketracer
20th July 2009, 09:29
No it is not.

The fact the fuel makes it into the chamber is certainly NOT deliberate.



When you quote me, please be accurate. I said air/fuel, you changed it to fuel. air/fuel mixture and fuel is two separate things.

Old School which is where we are now, is to suck air/fuel into the exhaust and ram it back.

New School DI is to suck air only into the exhaust and ram it back and inject the fuel after the exhaust port closes thereby saving fuel and cleaning up the exhaust.

Both still use the resonant forces in the exhaust system to supercharge the motor.

As I said before, however you squeeze extra air or air/fuel mixture into an engine above what it can normally aspirate for its self is supercharging and is most certainly deliberate in a 2-Stroke.

If you don't think so please backup you opinion with some authoritative references.

.

F5 Dave
20th July 2009, 09:38
Kaaden would be turning in his grave. Why don't you continue to use a megaphone pipe if the divergent systems are all important? The reason 2 strokes are particularly dirty is that the pipe is tuned over a very short rev range, the rest of the time there is mondo waste. An efficient variable gearbox bound to a constant speed engine may be a worthwhile improvement.

As said before, even though it isn't mechanically driven & working on the intake; if it is pressurising the engine more than what it could normally aspirate it is by definition supercharging it.

Irrespective to how much effort has gone into 'preventing' it, for a start the Schnurle(sp) loop engine was invented before the chamber, but still served & now serves a purpose. Better purity & less loss esp when pipe is out of tuned range. It delays the mixture in the cylinder so that while more is being sucked in (& rammed in with inertia) then in the blowdown period as much as poss is crammed into the cylinder & in fact what couldn't be contained is then pushed back in at the last mo. (vision of Monty Python's Mr Creosote )

By the same token air intakes pressurise a sealed airbox, that is supercharging. Both albeit to a minor level compared to a blower. & often still showing a negative pressure compared to suction pressure.

SS90
20th July 2009, 09:38
When you quote me, please be accurate. I said air/fuel, you changed it to fuel. air/fuel mixture and fuel is two seperate things.

Old School which is where we are now, is to suck air/fuel into the exhaust and ram it back.

New School DI is to suck air only into the exhaust and ram it back and inject the fuel after the exhaust port closes therby saving fuel and cleaning up the exhaust.

Both still use the resonant forces in the exhaust system to supercharge the motor.

As I said before, however you squeeze extra air or air/fuel mixture into an engine above what it can normally aspirate for its self is supercharging.

A "supercharger" is forced induction.

Ergo, an expansion chamber, cannot "force induce" an engine.

It can, however, increase the delivery ratio.

That is an important difference.

I'm not arguing over semantics here.

An expansion chamber helps to return over scavenged air/fuel into the cylinder.

That's not supercharging.

Maybe you could "Wikipedia" supercharging.

F5 Dave
20th July 2009, 09:41
Now you are quoting the internet. Just because it is most common doesn't mean it is the only way to 'overfill' the cylinder.

SS90
20th July 2009, 09:50
Kaaden would be turning in his grave.

As said before, even though it isn't mechanically driven & working on the intake; if it is pressurising the engine more than what it could normally aspirate it is by definition supercharging it.

Irrespective to how much effort has gone into 'preventing' it, for a start the Schnurle(sp) loop engine was invented before the chamber, but still served & now serves a purpose. Better purity & less loss esp when pipe is out of tuned range. It delays the mixture in the cylinder so that while more is being sucked in (& rammed in with inertia) then in the blowdown period as much as poss is crammed into the cylinder & in fact what couldn't be contained is then pushed back in at the last mo. (vision of Monty Python's Mr Creosote )

By the same token air intakes pressurise a sealed airbox, that is supercharging. Both albeit to a minor level compared to a blower. & often still showing a negative pressure compared to suction pressure.

Again, it is easy to get lost in terminology, but for example, the crankcase (at a certain point) is indeed a pump.

However, when the extraction effect of the chamber comes into play, the crankcase is no longer a pump.

But, when the chamber is not assisting the delivery of air/fuel to the cylinder, the crankcase is a pump.

So, is the crankcase a pump, or not?

I say YES.

(EDIT)
But it is only a pump when the expansion chamber is not providing "extraction" effect.

SOME people say that the expansion chamber "supercharges".

HOW?

The only reason the crankcase delivery ratio increases, is because the negative pressure (vacume) goes through the transfer ports, and is trapped in the cases when the transfers close.

I don't see that as "supercharging"

SS90
20th July 2009, 09:53
Now you are quoting the internet. Just because it is most common doesn't mean it is the only way to 'overfill' the cylinder.

Not quite. I am trying to demonstrate the importance of separating the different phases of a two stroke engine, so we can all understand expansion chamber design.

As you well know, it's not "black magic"

I don't see how increasing the delivery ratio of a two stroke is "supercharging", when you take the crankcase into account.

bucketracer
20th July 2009, 10:36
A "supercharger" is forced induction.

Ergo, an expansion chamber, cannot "force induce" an engine.


Maybe you could "Wikipedia" supercharging.

I am sorry your wrong again. Supercharging is not just forced induction at the inlet. Its forced induction per see.

As I said before, however you squeeze extra air or air/fuel mixture into an engine above what it can normally aspirate for its self is supercharging and is most certainly deliberate in a 2-Stroke.

And from the Oxford Dictionary

supercharger
• noun a device that increases the pressure of the fuel-air mixture in an internal-combustion engine, thereby giving greater efficiency.

http://www.askoxford.com/concise_oed/supercharger?view=uk

The expansion chamber most certainly can supercharge a 2-Stroke.

Please back your opinion with references otherwise its just your opinion.

.

F5 Dave
20th July 2009, 10:40
Yes I see the crankcase as a pump, not a particularly good one. The fact that it can sucked from too (just as Dirty Dorris may overscavenge your wiener as you pop your clogs, - ok now this has R18 rated the thread) doesn't stop it being a pump, in the same way as an engine doesn't stop being an engine if you tow it faster than it can go normally.

But the charging effect is primarily after induction is finished & the transfers are closed.

SS90
20th July 2009, 11:01
Yes I see the crankcase as a pump, not a particularly good one. The fact that it can sucked from too (just as Dirty Dorris may overscavenge your wiener as you pop your clogs, - ok now this has R18 rated the thread) doesn't stop it being a pump, in the same way as an engine doesn't stop being an engine if you tow it faster than it can go normally.

But the charging effect is primarily after induction is finished & the transfers are closed.

Well,
I used the Crankcase pump as an example because a few months ago I remember in the ESE thread you maintained that the crankcase was NOT a pump because of the extraction effect...... that's what I remember anyway, feel free to correct me if I remember that incorrectly!

But, can you clarify how pushing "overscavenged" fuel from the expansion chamber BACK into the cylinder constitues "supercharging"?

I don't see it that way.

Your example of an air box suggests that an air box can be considered "supecharging", so do you consider your Trinity engine "supercharged"?

I don't

Think of it this way.

If there was a true "supercharging" effect from an expansion chamber, then "schnürle loop" engines would be redundant, because you would be able to make more power by abandoning the transfer angles (scavenge patterns) and simply increase the port area's by having them "straight across the bore" (which logically will give you more power)

Yet, you know as well as I do, that to make a good long spread of power, you require the port angles to be designed in such a way that turbulence is created in the combustion chamber (as well as stopping as much fuel/air as possible from heading out the open exhaust port.)

If the expansion chamber supplied any degree of "supercharging" such requirements would be redundant and the level of attention a tuner must pay to scavenge patterns (such as is required now) would be negated, and all the attention would be on increasing the (I believe non-exsistent) "supercharging" effect of the chamber.

As it is, a correct scavenge pattern coupled with the correctly designed exhaust are JUST 2 (of many) CRITICAL things to consider in a two stroke engine design.

Fooman
20th July 2009, 11:12
From my favourite reference for this sort of shitflinging (Bosch Automotive Handbook 3rd Ed - note translated from German, so ignore any verbal niceties)

Supercharging Processes (See attached .pdf file)

Summary - The expansion chamber is not a mechanical supercharger, but it provides a dynamic supercharging effect similar to the tuned intake tube charging effect described in the attached document.

From memory, dynamic supercharging (e.g. using inertia of incoming air into cylinder) gives a max of 105% to 110% volumetric efficiency.

I certainly hope this contributes to the thread! :sherlock:

Cheers,
FM

F5 Dave
20th July 2009, 11:20
Without wading back through as million pages I probably said that a 2 stroke engine is not just a pump. The crankcase clearly is a pump, & a few other things.

Yow Ling
20th July 2009, 11:23
SO what exactly is supercharging? Is it filling the cylinder more than 100% full? If it is then any engine with VE over 100 is supercharged.

Nitrous oxide is not a pump or mechanical but is still supercharging, so if any thing rams more oxygen molecules into the cylinder it would be considered supercharging

F5 Dave
20th July 2009, 11:25
From my favourite reference for this sort of shitflinging

That so reminds me of this;
http://www.youtube.com/watch?v=pgUwpb3I98M
Well smeared FM

F5 Dave
20th July 2009, 11:28
SO what exactly is supercharging? Is it filling the cylinder more than 100% full? If it is then any engine with VE over 100 is supercharged.

Nitrous oxide is not a pump or mechanical but is still supercharging, so if any thing rams more oxygen molecules into the cylinder it would be considered supercharging

Yeah we're getting into semantics. I'd say there is a supercharging effect, but I wouldn't bother to say it was supercharged unless it seriously pressurised, but you could still argue the toss.

Fooman
20th July 2009, 11:28
SO what exactly is supercharging? Is it filling the cylinder more than 100% full? If it is then any engine with VE over 100 is supercharged.

Nitrous oxide is not a pump or mechanical but is still supercharging, so if any thing rams more oxygen molecules into the cylinder it would be considered supercharging

From what I've read, posted above, and can remember from applied thermodynamics course many moons ago, the answer you seek is "Yes".

A supercharger is not the only thing that can supercharge.

Cheers,
FM

Buckets4Me
20th July 2009, 12:24
Tecnicaly I thought supercharging had to compress the air before it got into the engine


ie a turbo shifts more air but dosent compress it :P

a supercharger compressis the air and shifts it

lets all step back and have a group hug before someone hurts someones fealings

NOS is consintrated N2o so more oxogen (much like compressed air)

But as SS90 points out the chamber dosent force more air fuel into the cylinder so cant be called supercharging

and who cares weather it fails on polution or not (we want fast and warmer weather)

F5 Dave
20th July 2009, 12:25
. . .
But as SS90 points out the chamber dosent force more air fuel into the cylinder so cant be called supercharging . . .

um, have you not been reading?

bucketracer
20th July 2009, 12:26
.

So a 2-Stroke "is" Supercharged by its expansion chamber and its wrong to claim it does'nt.

.

bucketracer
20th July 2009, 12:39
The whole "scavenge Pattern" concept is to reduce the amount of fuel that gets out the exhaust port.

That's why a two stroke is called a "schürle loop" (closed loop).........

The whole idea is to keep as much fuel in the cylinder as possible,

Nope wrong about that too.

.

Buckets4Me
20th July 2009, 12:39
.

So a 2-Stroke "is" Supercharged by its expansion chamber and its wrong to claim it does'nt.

.

no it's turboed as it uses exaust gass to superchrge the cylinder :apint:

(younger audience more add revenue turbo not supercharger with refrence to NOS and drifting)

F5 Dave
20th July 2009, 13:12
ok I'm getting seriously bored of this. When are we going to get onto the serious business of whatever it was we were talking about?


. . . Think it was polishing the fins on a go-cart wasn't it:rolleyes:

bucketracer
20th July 2009, 13:21
Combine the above technique with a copper combustion chamber (all the rage in high performance two stokes, perhaps even a copper finned base gasket) a little "ahead of it's time" and exhaust pipe and port specs and you got your self a weapon.

At last, SS90 is right about something.

.

Skunk
20th July 2009, 13:53
:corn::corn::corn::jerry:

Fooman
20th July 2009, 14:24
ie a turbo shifts more air but dosent compress it :P


That's a pump. Which can compress the air, after exit from the pump, if it is pumping into a smaller volume. A turbocharger is a supercharger powered by exhaust gases via a turbine. Doesn't use mechanical power to drive, just waste energy in the exhaust, so increases the efficiency of the engine.

Cheers,
FM

Buckets4Me
20th July 2009, 19:50
That's a pump. Which can compress the air, after exit from the pump, if it is pumping into a smaller volume. A turbocharger is a supercharger powered by exhaust gases via a turbine. Doesn't use mechanical power to drive, just waste energy in the exhaust, so increases the efficiency of the engine.

Cheers,
FM

so supercharging is ANYTHING that pushes more than 100% air charge into the cylinder

:apint:

bucketracer
20th July 2009, 20:29
so supercharging is ANYTHING that pushes more than 100% air charge into the cylinder

:apint:

Yes, thats anything that makes the engine achieve greater than 100% volumetric efficiency.

Any extra air or air/fuel mixture squeezed into an engine above what it can normally aspirate for its self is supercharging.

The expansion chamber most certainly supercharges a 2-Stroke.

.

koba
20th July 2009, 20:32
In all the guff for my MR2 it reffered to the "Inertial supercharging effect" provided by tuned length intakes in the TVIS (http://en.wikipedia.org/wiki/T-VIS) system.
So I guess Toyota must see it that way.
(And Yamaha maybe as the built the engines..?)

Ooky
20th July 2009, 21:11
http://homepage.mac.com/rg500delta/deltaphasetwo/Frames/pipe_design.html

for Rg500 but its alot about pipes :first:

Yow Ling
20th July 2009, 21:24
ok I'm getting seriously bored of this. When are we going to get onto the serious business of whatever it was we were talking about?


. . . Think it was polishing the fins on a go-cart wasn't it:rolleyes:

Yea I thought we were going to talk about NSUs and deeks

TZ350
20th July 2009, 21:53
.


you could read a book called "the two stroke tuners hand book" By Gordon Jennings.....
It's a really good place to start, many top tuners have recommended it to me, it is well written, and while SOME aspects are dated, if you read it carefully, it is a little "ahead of it's time"


If the expansion chamber supplied any degree of "supercharging" such requirements would be redundant and the level of attention a tuner must pay to scavenge patterns (such as is required now) would be negated, and all the attention would be on increasing the (I believe non-exsistent) "supercharging" effect of the chamber.

Jennings talks about the expansion chamber as a lot like having a supercharger. P53 and refers again to the supercharging effect of inertial wave action on P83.

P105 scavenging, P108 for a description of the Loop Scavenging System or Schnerurles Loop. P115 cylinder flow patterns, 117 & 118 residual exhaust gases.

Cylinder scavenging flow patterns are all about preventing short circuiting of the incoming fresh mixture directly out the exhaust and maintaining separation of the spent exhaust gases as the incoming fresh mixture sweeps up and over filling the cylinder and sweeping the old gases before it and eventually expelling them out the exhaust port.

Much effort has gone into refining scavenging flow patterns to minimize the mixing of old and new and thereby minimize the dilution of the incoming fresh mixture. This mixing is a problem whether the motor has a carburetor or is direct injection as dilution of the fresh with exhaust reduces the amount of oxygen in the new mixture.

With a typical scavenging ratio of 80% or so, any improvements in the scavenging flow pattern that maintains separation and reduces dilution means more fresh air/mixture can be trapped in the cylinder by the action of the expansion chamber.

Jennings book is a good place to start with understanding the basics of scavenging flow patterns and their roll in reducing charge dilution and the supercharging effect of the expansion chamber.

It's smart to have a grasp of these basics before tackling the intricacies of 2-Stroke Tuning.

A link to Jennings book can be found on page 80 of the ESE thread.
.

TZ350
20th July 2009, 22:09
As it is, a correct scavenge pattern coupled with the correctly designed exhaust are JUST 2 (of many) CRITICAL things to consider in a two stroke engine design.

Thats true, now the first 2 things have been covered, I would be interested to hear more about some of the other critical things in two stroke engine design.

.

Skunk
20th July 2009, 22:16
There are plenty of computer programmes available that will design a pipe for you, using just port time areas,RPM intended etc.

My experience is that all these programmes that only require a small amount of data (specifically in relation to exhaust port only) return essentially the same expansion chamber..... (dated)

Obviously, the more you spend on the software, the better the expansion chamber you end up with....but you have to "answer the right questions" this software asks......it's quite complicated.

There are a lot more factors you must consider when designing an expansion chamber.

That is the difference between an expansion chamber designed in the 70's, and one designed recently.So instead of telling me it's all dated and wrong how about telling me the modern and correct way.

Or is it so secret (because of the Asians) that no one is allowed to know?

TZ350
20th July 2009, 22:17
http://homepage.mac.com/rg500delta/deltaphasetwo/Frames/pipe_design.html

for Rg500 but its alot about pipes :first:

Thats some very interesting reading there.

.

SS90
21st July 2009, 09:12
.

So a 2-Stroke "is" Supercharged by its expansion chamber and its wrong to claim it does'nt.

.

No it's not.

Sshhhhhhh Bucketracer....the grownups are talking!

SS90
21st July 2009, 09:15
Yes, thats anything that makes the engine achieve greater than 100% volumetric efficiency.

Any extra air or air/fuel mixture squeezed into an engine above what it can normally aspirate for its self is supercharging.

The expansion chamber most certainly supercharges a 2-Stroke.

.

OK, so tell us Bucketracer.......WHAT IS THE VOLUMETRIC EFFICIENCY OF A PERFORMANCE TWO STROKE ENGINE?

SS90
21st July 2009, 09:19
.





Jennings talks about the expansion chamber as a lot like having a supercharger. P53 and refers again to the supercharging effect of inertial wave action on P83.

P105 scavenging, P108 for a description of the Loop Scavenging System or Schnerurles Loop. P115 cylinder flow patterns, 117 & 118 residual exhaust gases.

Cylinder scavenging flow patterns are all about preventing short circuiting of the incoming fresh mixture directly out the exhaust and maintaining separation of the spent exhaust gases as the incoming fresh mixture sweeps up and over filling the cylinder and sweeping the old gases before it and eventually expelling them out the exhaust port.

Much effort has gone into refining scavenging flow patterns to minimize the mixing of old and new and thereby minimize the dilution of the incoming fresh mixture. This mixing is a problem whether the motor has a carburetor or is direct injection as dilution of the fresh with exhaust reduces the amount of oxygen in the new mixture.

With a typical scavenging ratio of 80% or so, any improvements in the scavenging flow pattern that maintains separation and reduces dilution means more fresh air/mixture can be trapped in the cylinder by the action of the expansion chamber.

Jennings book is a good place to start with understanding the basics of scavenging flow patterns and their roll in reducing charge dilution and the supercharging effect of the expansion chamber.

It's smart to have a grasp of these basics before tackling the intricacies of 2-Stroke Tuning.

A link to Jennings book can be found on page 80 of the ESE thread.
.

Teezeetreefiddy "old boy", once again, you have managed to use 1000 words to over complicate things.

I am quite confident that I have more experience with scavenge patterns than you.

In any event.

To summate your post.

Scavenge patterns essentially stop the incoming fresh charge from heading out the open exhaust port.

The end.

F5 Dave
21st July 2009, 09:22
I'd take the 5th B.R. See if you can Winston around without answering the question. That's the SS way.


Change this thread to Political Mimicry.:Pokey:

SS90
21st July 2009, 09:27
From my favourite reference for this sort of shitflinging (Bosch Automotive Handbook 3rd Ed - note translated from German, so ignore any verbal niceties)

Supercharging Processes (See attached .pdf file)

Summary - The expansion chamber is not a mechanical supercharger, but it provides a dynamic supercharging effect similar to the tuned intake tube charging effect described in the attached document.

From memory, dynamic supercharging (e.g. using inertia of incoming air into cylinder) gives a max of 105% to 110% volumetric efficiency.

I certainly hope this contributes to the thread! :sherlock:

Cheers,
FM

In an effort to get some clear information written before the local fools start replying, I have not managed to read your attachment as yet, but how abou this.

Do you know of any material (preferably not web based) that can accurately quote the VE of a performance two stroke?

I maintain that a performance two stroke IS MOST CERTAINLY NOT "SUPERCHARGED".

For the sake of "science" I will agree that you COULD consider there is a slight "SUPERCHARGE" "EFFECT" from an expansion chamber, however, that alone (the effect) does NOT constitute a "supercharged" engine, anymore that an airbox does.

Essentially, an expansion chamber pushes "HALF FUCKED" over heated low density air, fuel, and particle matter back in to the combustion chamber.

How does that constitute "a supercharged engine"?
:doobey:

Skunk
21st July 2009, 09:27
No it's not.

Sshhhhhhh Bucketracer....the grownups are talking!You should shut up too then.


OK, so tell us Bucketracer.......WHAT IS THE VOLUMETRIC EFFICIENCY OF A PERFORMANCE TWO STROKE ENGINE?You're the 'expert' - why don't you tell us?


Teezeetreefiddy "old boy", once again, you have managed to use 1000 words to over complicate things.

Scavenge patterns essentially stop the incoming fresh charge from heading out the open exhaust port.Unlike you who uses 1000 words to say nothing.

By the way - this may be a surprise to you - scavenging isn't perfect otherwise the 'chamber' would be a 'megaphone'. Well, no it wouldn't... There would be no need for anything because scavenging would do it all.

And I still haven't heard an answer on scroll diodes.

Back to school SS90.

Skunk
21st July 2009, 09:31
How does that constitute "a supercharged engine"?
:doobey:
By increasing the volume of air (and fuel in this case) in the combustion chamber, fool. I suggest you do some reading.

SS90
21st July 2009, 09:33
So instead of telling me it's all dated and wrong how about telling me the modern and correct way.

Or is it so secret (because of the Asians) that no one is allowed to know?

I would LIKE to skunk, but I am worried that if I did, given the fact that Teezeetreefiddys engine (apparently) is "overheating" and requires dubious cooling efficiency improvements, (at a "wopping" 15.5 P.S) if I was to tell him how to make more power, it may well cause a Nuclear Holcaust of biblical proportions as it headed down the back straight, causing widespread destruction,and global warming of unprecedented proportions.

I don't want that on my head.

Mind you, he probably still wont win a race.

Skunk
21st July 2009, 09:34
I would LIKE to skunk, but I am worried that if I did, given the fact that Teezeetreefiddys engine (apparently) is "overheating" and requires dubious cooling efficiency improvements, (at a "wopping" 15.5 P.S) if I was to tell him how to make more power, it may well cause a Nuclear Holcaust of biblical proportions as it headed down the back straight, causing widespread destruction,and global warming of unprecedented proportions.

I don't want that on my head.

Mind you, he probably still wont win a race.
Then it's pointless you posting here. Goodbye.

SS90
21st July 2009, 09:35
You should shut up too then.


And I still haven't heard an answer on scroll diodes.

Back to school SS90.

SCROLL DIODES!!!!!!!!!!

Bahahahahhahahaha!

Ask Thomas.......it was his "idea" wasn't it?

SS90
21st July 2009, 09:36
By increasing the volume of air (and fuel in this case) in the combustion chamber, fool. I suggest you do some reading.

Got any proof of that?

Skunk
21st July 2009, 09:39
SCROLL DIODES!!!!!!!!!!

Bahahahahhahahaha!

Ask Thomas.......it was his "idea" wasn't it?
Still no answer though.

Got anymore informationless criticism?

Skunk
21st July 2009, 09:40
Got any proof of that?
Got any proof that every text available on chambers is wrong? That's right - you can't say.

SS90
21st July 2009, 09:40
Still no answer though.

Got anymore informationless criticism?

Come on Skunk.... who's idea was it, yours or Thomas's......???????

SS90
21st July 2009, 09:42
Got any proof that every text available on chambers is wrong? That's right - you can't say.

Bhahahahahhaha!

INTERNET BASED TEXT?????

bwhwhwhahahhahah!

Your complete inability to accept new information is why SOME of you fail to accept that it is possible to make a 125cc air cooled ingine (4 speed) with 30 PS.......

Skunk
21st July 2009, 09:42
Come on Skunk.... who's idea was it, yours or Thomas's......???????
If you did a little reading you'd find out it was a Japanese guy's idea. Mind you, being Asian he must have stolen it from a european.

bucketracer
21st July 2009, 09:45
Scavenge patterns essentially stop the incoming fresh charge from heading out the open exhaust port.

The end.

TZ has allready told us that. Please tell us something new.

.

SS90
21st July 2009, 09:45
If you did a little reading you'd find out it was a Japanese guy's idea. Mind you, being Asian he must have stolen it from a european.

So you are saying that Thomas stole it form you?

Skunk
21st July 2009, 09:47
Bhahahahahhaha!

INTERNET BASED TEXT?????

bwhwhwhahahhahah!

Your complete inability to accept new information is why SOME of you fail to accept that it is possible to make a 125cc air cooled ingine (4 speed) with 30 PS.......
The internet is all I have as YOU haven't given ANY NEW information - just criticized everything anyone posts. Nor have you shown any source of new information. I personally don't see any problem with 30PS 125cc two strokes. I just don't see any INFORMATION on how it can be achieved coming from you.

Oh - I never said 'internet based' either.

SS90
21st July 2009, 09:55
The internet is all I have as YOU haven't given ANY NEW information - just criticized everything anyone posts. Nor have you shown any source of new information. I personally don't see any problem with 30PS 125cc two strokes. I just don't see any INFORMATION on how it can be achieved coming from you.

Oh - I never said 'internet based' either.

Perhaps if you contributed in a mature fashion, I would be more forthcoming with information.

Rather than (incorrectly) "knocking" everything I write, some intelligent comments would invoke a more helpful response.

Don't forget Skunk, I feed myself and keep a roof above my head by tuning two stroke engines.... I must know something....

bucketracer
21st July 2009, 10:03
Rather than (incorrectly) "knocking" everything I write, some intelligent comments would invoke a more helpful response.


Actually there have been many inteligent comments mostly backed with references from books and the internet.

To advance your opinion you will need to explain it in a way that makes sense.

.

SS90
21st July 2009, 10:05
The internet is all I have as YOU haven't given ANY NEW information - just criticized everything anyone posts. Nor have you shown any source of new information. I personally don't see any problem with 30PS 125cc two strokes. I just don't see any INFORMATION on how it can be achieved coming from you.

Oh - I never said 'internet based' either.

Ok Skunk, I have posted this run in the ESE thread, but here is an example of how an expansion chamber DOES NOT "SUPERCHARGE" a cylinder.

The same exhaust,head,primary compression,ignition (and timing) flywheel etc.....

Only the scavenge pattern has been changed (dramatically).........

If a two stroke chamber "supercharged" a cylinder, why would keeping the air/fuel mixture in the cylinder (stopping it heading out the open exhaust port) make such an improvement?

If indeed a two stroke chamber "supercharged" a cylinder, scavenge patterns would be redundant, and we could increase our transfer port area (by simply "squaring" them off on the bore)...... and make power via the "supercharger" exhaust.

This graph shows otherwise.

SS90
21st July 2009, 10:10
Actually there have been many inteligent comments mostly backed with references from books and the internet.

To advance your opinion you will need to explain it in a way that makes sense.

.

Ermmm,

So, do you still think this is a correct statement?

Does a scavenge pattern stop the fuel from escaping out the open exhaust port or not?

Skunk
21st July 2009, 10:14
Ok Skunk, I have posted this run in the ESE thread, but here is an example of how an expansion chamber DOES NOT "SUPERCHARGE" a cylinder.

The same exhaust,head,primary compression,ignition (and timing) flywheel etc.....

Only the scavenge pattern has been changed (dramatically).........

If a two stroke chamber "supercharged" a cylinder, why would keeping the air/fuel mixture in the cylinder (stopping it heading out the open exhaust port) make such an improvement?

If indeed a two stroke chamber "supercharged" a cylinder, scavenge patterns would be redundant, and we could increase our transfer port area (by simply "squaring" them off on the bore)...... and make power via the "supercharger" exhaust.

This graph shows otherwise.
I'm only knocking your knocking.

Nice chart.
What was the chamber?
Was there a chamber?
What did you do to achieve that scavenge effect?
How does that show the chamber was doing absolutely nothing?

I thought Scavenging and chambers had to work together, along with transfer timings etc. Are you saying the chamber is redundant or doing something other than pushing air/fuel mix back into the cylinder? If the scavenging is perfect what is the chamber pushing back? Is it instead holding the air/fuel mix at the port face while the scvenging does it's job? How do you get that fine balance over such a rev range?

That's it. In the past you have NOT explained these things. That's why you get the response you do.

Here's your chance.

SS90
21st July 2009, 10:21
I'm only knocking your knocking.

Nice chart.
What was the chamber?
Was there a chamber?
What did you do to achieve that scavenge effect?
How does that show the chamber was doing absolutely nothing?

That's it. In the past you have NOT explained these things. That's way you get the response you do.

Here's your chance.

What was the chamber? I will sell you one for €500 (incl postage), it will only fit a small frame Vespa (sorry) But it will be hand made in Germany (by a Kiwi)

Was there a chamber? errrr YES.

What did I do to achieve the scavenge effect? Paid attention and accepted advise from people, along with intelligent conversation and constructive critisisim, along with leaning "how and why" other manufacturers did things.

I don't say that the chamber was doing absolutely "nothing", I use this as an example to show that if the chamber was "supercharging" the cylinder, then improvements in the scavenge patterns would have no effect.

TZ350
21st July 2009, 10:30
.




Teezeetreefiddy "old boy",

.



As we are not friends, to continue to miss use my name and your mock familiarity is childish don't you think?

.

Skunk
21st July 2009, 10:33
What was the chamber? I will sell you one for €500 (incl postage), it will only fit a small frame Vespa (sorry) But it will be hand made in Germany (by a Kiwi)

Was there a chamber? errrr YES.

What did I do to achieve the scavenge effect? Paid attention and accepted advise from people, along with intelligent conversation and constructive critisisim, along with leaning "how and why" other manufacturers did things.

I don't say that the chamber was doing absolutely "nothing", I use this as an example to show that if the chamber was "supercharging" the cylinder, then improvements in the scavenge patterns would have no effect.
There you go again! Lots of words and zero usable information. If you want us to listen then you have to be saying something - not a lot of nothing.

Where is the straight out answer to ANY of my questions... oh, right - yes it had a chamber. :rolleyes:
As I said - scavenge and chamber MUST work together. Both do a job.

SS90
21st July 2009, 10:39
There you go again! Lots of words and zero usable information. If you want us to listen then you have to be saying something - not a lot of nothing.

Where is the straight out answer to ANY of my questions... oh, right - yes it had a chamber. :rolleyes:
As I said - scavenge and chamber MUST work together. Both do a job.

Ermmm,

Yes Skunk.

That's what I have been saying, I guess it is a little hard to follow when childish nonsense keeps "popping up"......

However, this particular "series of discussions" is about the (I believe), non exsistant " expansion chamber supercharged" two stroke engine.

No one has convinced me that an expansion chamber "supercharges" a cylinder.

If we all want to improve our knowledge (I do) then we should all look at how things really work.

It's not Magic.

Can you show us anything that an expansion chamber "supercharges" a cylinder (i.e increases the V.E over 100%?)

SS90
21st July 2009, 10:41
.



As we are not friends, to continue to miss use my name and your mock familiarity is childish don't you think?

.

We are not friends?

Since when?

Skunk
21st July 2009, 10:54
Can you show us anything that an expansion chamber "supercharges" a cylinder (i.e increases the V.E over 100%?)

No. I work in the printing industry. You're the expert. Can you show us it doesn't?

If you can, will you? I'm already guessing I know the answer to that one.

Oh, since when is supercharging defined as over 100% VE? I understood supercharging as increasing normal VE.

inlinefour
21st July 2009, 10:58
It would be nice to move this in to the "Mainstream" section of this site, and I hope we can do this shortly, however, "Good things take time", and some co-operation is needed.

Let's all get together and start a "Two stroke tuning" thread that rivals others in the world, as, we are all Kiwi's, and as such have an amazing pedagree (particularly when it comes to high powered racing Two stroke engines (Kim Newcome for example, & the often forgotten B.S.L Team, and it's conceptor, Brian Buckley)...........

Looking at the current NZ bucket racing rules, I see the potential for developing a very special type of engine.

A 125cc, Air cooled Two Stroke, limited only by it's capacity, (and), a 24MM carb............

I am unsure of the rules you can apply when starting a thread, but one I would like to place is that no-one is allowed to

"use words bigger than their I.Q"

What I mean is, lets try to simplify it, so that EVERYONE can contribute

......... many effective solutions have been discovered by in-experienced observers, simply because they applied logic that the rest of us missed , because we where "too involved".........

So.... lets Begin......

Ive not read through this whole thread and I dont intend to, so this is a reply to this quoted post. If there are other bikers etc that shun the 2-stroker in any way, they need a quick lesson in motorcycle history. Almost all high preformance bikes started in one form or another with a 2-stroke engine. I grew up with 2-strokes and had made sure that within my bike collection was several, before the bleeding hearted, possum kissing, tree hugging, politically correct, cry for the environmentilists had them banned in NZ. Which is kind of ironic, because there are plenty of applications where the 2-stroke engine is used/prefferred and Im not talking about bikes. Even one of my RC trucks is powered by a high preformance 2-stroke single that would out drag most bikes, until it hit its top speed. Im not sure about everyone elses experience with tuning high preformance 2-stroke engines, but most of mine didnt need much tuning at all and most issues I ever had was a sign that something had vibrated loose and needed tightening up/resetting again. I say that if 2-strokers are not in the mainstream of this site allready, its probably just a sign of ignorance more than anything else. :Pokey:

SS90
21st July 2009, 11:00
No. I work in the printing industry.

The printing industry?

Figures.

I believe I have put a good case forward that an expansion chamber does NOT "supercharge" a cylinder, while at the same time keeping it simple and uncomplicated.

As yet, no one has shown that an expansion chamber "supercharges a cylinder" (Fooman has indicated that there is a " dynamic supercharging effect"

that does not constitute a "supercharged" cylinder.

Fooman seems to have an exceptional grasp of Physics... (Massy it seems) perhaps he can contribute something that disproves my statement.

SS90
21st July 2009, 11:03
Oh, since when is supercharging defined as over 100% VE? I understood supercharging as increasing normal VE.

Hmmmmm,

So, back to definitions again.

I would consider that if an engine is "supercharged" it has a VE of over 100%.

Skunk
21st July 2009, 11:09
The printing industry?

Figures.

I believe I have put a good case forward that an expansion chamber does NOT "supercharge" a cylinder.An insult and more non information. All you chart shows is the effect of the scavenge working WITH the chamber and AGAINST the chamber.


Hmmmmm,

So, back to definitions again.You're the one defining supercharging as over 100%VE. I only asked if that was the standard as all MY research doesn't show that (being in the printing trade - 'figures' eh?) You being in the trade may have more info but you seem to prefer to insult than share. How does that relate to your post as quoted by inlinefour?

SS90
21st July 2009, 11:23
An insult and more non information. All you chart shows is the effect of the scavenge working WITH the chamber and AGAINST the chamber.

You're the one defining supercharging as over 100%VE. I only asked if that was the standard as all MY research doesn't show that (being in the printing trade - 'figures' eh?) You being in the trade may have more info but you seem to prefer to insult than share. How does that relate to your post as quoted by inlinefour?

Care to share your "research" Skunk?

I would like to read a credible source that shows that "supercharging" is ANYTHING that simply increases VE (be it over 100% or not)

That's quite an interesting point, because we all seem to be stuck on definitions here.

Although, this is getting a little tiresome.......

Can anyone quote a source that defines "supercharging" (and in particular, it's relation to VE)

Anyway, if a Two Stroke chamber really "supercharged" a cylinder, would that not make them ILLEGAL in GP racing?

And, just to make a point,perhaps you should consider yourself when it comes to insults.........

Skunk
21st July 2009, 11:34
Care to share your "research" Skunk?

I would like to read a credible source that shows that "supercharging" is ANYTHING that simply increases VE (be it over 100% or not)

A supercharger is an air compressor used for forced induction of an internal combustion engine. The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally-aspirated engine, which allows more fuel to be provided and more work to be done per cycle, increasing the power output of the engine.

The term supercharging refers to any pump that forces air into an engine, but, in common usage, it refers to pumps that are driven directly by the engine, as opposed to turbochargers that are driven by the pressure of the exhaust gases.

Sorry this is from the Internet. But it got there from a book. And the book was written in a University to teach students. Is that close enough to credible?

As all this from a comment I made to show that air/fuel mix IS pushed back into the cylinder by the chambers pressure wave (why else have one?) and I only used the term supercharge as a colloquial term to explain lots in a few words.

SS90
21st July 2009, 11:43
A supercharger is an air compressor used for forced induction of an internal combustion engine. The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally-aspirated engine, which allows more fuel to be provided and more work to be done per cycle, increasing the power output of the engine.

The term supercharging refers to any pump that forces air into an engine, but, in common usage, it refers to pumps that are driven directly by the engine, as opposed to turbochargers that are driven by the pressure of the exhaust gases.

Sorry this is from the Internet. But it got there from a book. And the book was written in a University to teach students. Is that close enough to credible?

Nope.

Sorry. Skunk.

That is a SUPERCHARGER (a mechanical one)

The terminolgy I am looking for is

"What constitutes something that is "SUPERCHARGED" (and in particular, at what VE percentage constitutes something that has BEEN "supercharged" (in relation to an internal combustion engine.

Not "what is a mechanical superchager"

Sorry for the confusion.

Because if we use that definition, "supercharging" is ANYTHING that forces air into an engine, and CLEARLY an expansion chamber does not do that.

Skunk
21st July 2009, 11:47
Because if we use that definition, "supercharging" is ANYTHING that forces air into an engine, and CLEARLY an expansion chamber does not do that.What does the pressure wave do then?

bucketracer
21st July 2009, 12:26
.

Give it up Skunk. SS90 hasn't got anything, he's just wasting your time.

.

Buckets4Me
21st July 2009, 13:41
I am quite confident that I have more experience with scavenge patterns than you.

In any event.

To summate your post.

Scavenge patterns essentially stop the incoming fresh charge from heading out the open exhaust port.

The end.

then why do we have a chamber and not a straight pipe ??????? like a 4 stroke ????????

Buckets4Me
21st July 2009, 13:50
What does the pressure wave do then?

it stops the scroll diods from working :apint:

Buckets4Me
21st July 2009, 13:51
.

Give it up Skunk. SS90 hasn't got anything, he's just wasting your time.

.

yes BUT he is funny :rolleyes:

I wouldn't mind if he could tell me what the chamber dose as I have been misinformed and would like to be better educated.

I always thought the chamber forced more good air and fuel back into the cylinder but it looks like it's only there for looks or to stop the new charge coming out ?????

Fooman
21st July 2009, 14:20
What we need is something like the attached graph, but normalising the pressures to take into account the dV from piston movement and combustion - any increase in cylinder pressure outside that from compression and combustion would be due to a supercharging effect.

It is an interesting point as to what does supercharging mean - I am very happy with the definition of VE being greater than 100% - more air goes into the cylinder than when at ambient pressure. Ambient is very important - a supercharged cylinder could be running at less that 1 bar absolute, if it is at altitude. But can one consider supercharging to be a simple increase in VE?

A quick scan of an old thermodynamics text (Karlekar, 1983) suggests that for any "real" reciprocating compressor (i.e. a crank/piston/cylinder arrangement with intake and exhaust with residual fluid, heat transfer), the volumetric efficiency can be written as (trying to translate into ASCII):

VE = [ 1 + CF - CF(pH/pL)^(1/n)](vS/v2)

where CF = clearance factors, v = specific volumes, p = pressures, n = polytropic exponent (~ how ideal the fluid is).

Not pretending to understand all that, the upshot of it is that for a certain set of pressure ratios and finite clearance volume, the VE will be less than unity , or less than 100%.

So perhaps supercharging is an increase in VE (and hence availability of extra fuel/air mixture to burn), above the theoretical limit set by the geometry of thermodynamic system under investigation.

I am sure that for a two stroke motor, the above equation will be slightly, or even rather, different, but if it does not contain a term for returning intake air, or even pressure from the expansion chamber, then if there is any effect from the chamber, it could be considered dynamic supercharging, although this would only be if the pipe is on-song as it were.

Cheers,
FM

Skunk
21st July 2009, 15:14
I am sure that for a two stroke motor, the above equation will be slightly, or even rather, different, but if it does not contain a term for returning intake air, or even pressure from the expansion chamber, then if there is any effect from the chamber, it could be considered dynamic supercharging, although this would only be if the pipe is on-song as it were.
Sorry Fooman - SS90 says there is no return from the pipe. :laugh:

And that graph is Gold!

Fooman
21st July 2009, 15:26
Sorry Fooman - SS90 says there is no return from the pipe. :laugh:

And that graph is Gold!

He may be right: There may be no return from the pipe, but what about the exhaust port?

Cheers,
FM

F5 Dave
21st July 2009, 15:50
I hit the unsubscribe button a while back, but stumbled back.

That graph is quite a nice representation. To put it in context one presumes it is a piston port engine with ~ 188 degrees duration & these measurements were presumably taken while running at tuned frequency, maybe 10,000rpm. Look at the steep curve pressure increase just a whisker before ex closing. Doesn't show transfer IO so can't see blowdown, but I assume this is a cooking engine rather than a race one.

Hi IL4, long time since seen you here, hope all is well.

Skunk
21st July 2009, 16:03
He may be right: There may be no return from the pipe, but what about the exhaust port?

Cheers,
FM
Are you saying the return is mainly from the port to flange area and not so much from the header area?
My understanding is the fresh charge will exit the exhaust port by 100 or more mm (generalisation) before being pushed back.
I also understood that scavenging was to clean out the cylinder of old charge as completely as possible (even if it ends up in the pipe).

Am I correct in any part?

F5 Dave
21st July 2009, 16:33
Pipe wrapping has fallen out of favor as it heats the returning charge that is expelled into the header. Well. . . the scavenging aids cylinder filling, the clean separation of gases (or grubby attempt to do so) is where the rest of the engine design comes into play. But this is easier with some vacuum at the appropriate time.

Of course when pipe out of tuned freq the negative & positive waves arrive at just the wrong time to perform disruptive work.

gav
21st July 2009, 17:33
Care to share your "research" Skunk?

I would like to read a credible source that shows that "supercharging" is ANYTHING that simply increases VE (be it over 100% or not)

That's quite an interesting point, because we all seem to be stuck on definitions here.

Although, this is getting a little tiresome.......

Can anyone quote a source that defines "supercharging" (and in particular, it's relation to VE)

Anyway, if a Two Stroke chamber really "supercharged" a cylinder, would that not make them ILLEGAL in GP racing?

And, just to make a point,perhaps you should consider yourself when it comes to insults.........

Heres an example of "supercharging" being referred to in regards to the action of the expansion chamber. 3/4 of the way down the page.
http://www.southernskies.net/page_info/runningtwostrokeengine.html

This pulse is timed to reach the exhaust port after the transfer ports close, but before the exhaust port closes. The returning compression wave pushes the mixture drawn into the header by the negative pressure wave back into the cylinder, thus supercharging (a bigger charge than normal) the engine. The straight section of pipe between the two cones exists to ensure that the positive waves reaches the exhaust port at the correct time:

Sketchy_Racer
21st July 2009, 17:49
Don't forget Skunk, I feed myself and keep a roof above my head by tuning two stroke engines.... I must know something....

Just because you do something for a living doesn't mean your any good at it though does it? Just because someone pushes trolleys for a living doesn't mean that only they know the correct way to push a trolley...

Everything I read from you is either an insult, a critisism or you boosting your own ego about how great you are at two stroke tuning.

You strike me to be one of these people that can read a book, or article about something, pick up what the book is saying and use the technical jargon to make it seem like you know what your on about. You don't seem to be able to think outside the square, nor change a preset view on something even though from an outsider looking in, you have been wrong! (as everyone is at some stage or another)

I've said it before in another thread, but it got me in trouble, so I wont say it again, I will however link you to it just to remind you - http://www.kiwibiker.co.nz/forums/showpost.php?p=1129270905&postcount=242

Rodney007
21st July 2009, 17:55
You strike me to be one of these people that can read a book, or article about something, pick up what the book is saying and use the technical jargon to make it seem like you know what your on about.


this is kiwibiker, its what we do,

bucketracer
21st July 2009, 19:10
I've said it before in another thread, but it got me in trouble, so I wont say it again, I will however link you to it just to remind you - http://www.kiwibiker.co.nz/forums/showpost.php?p=1129270905&postcount=242

You got into trouble for that!!!! I did too, for something similar. Thats interesting, Hmmmm

a bit of topic, but does anyone else remember the character Tod from the film "Wedding Crashers"?

.

Fooman
21st July 2009, 20:08
Are you saying the return is mainly from the port to flange area and not so much from the header area?
My understanding is the fresh charge will exit the exhaust port by 100 or more mm (generalisation) before being pushed back.
I also understood that scavenging was to clean out the cylinder of old charge as completely as possible (even if it ends up in the pipe).

Am I correct in any part?

I was being asininely picky on behalf, etc. I just saw a comment in a paper saying that the fresh charge does not necessarily go into the pipe a reasonable distance - depends on the config of the engine as a whole.

One would think that a 2T motor that minimised or eliminated the charge lost down the pipe, but pushed all the exhaust out would be rather desirable - that doesn't imply a lot of charge going out the pipe is desireable...?

I know less than you about the "art" of two strokes, but know a reasonable amount on thermodynamic cycles and the engineering thereof.

I did some quick reading after I posted this - VE is the wrong expression for 2T engines for precisely your last comment - it is not just how much you can stuff into a cylinder, but how much fresh charge you can put in, after extracting all the old charge. Scavenging efficiency is the term used in 2T terms, due to the combination of intake and exhaust flows. I'll try and track down some papers etc tomorrow - There was a nice 1949 MIT thesis on the web, but that probably didn't take into account any spanny!

Cheers,
FM

bucketracer
21st July 2009, 20:18
.



Essentially, an expansion chamber pushes "HALF FUCKED" over heated low density air, fuel, and particle matter back in to the combustion chamber.
.


SS90 you’re starting to get it, the supercharging thing.

And now there is the loop scavenge systems flow patterns and how they are designed so the incoming mixture push's the exhaust ahead of it while minimizing mixing and there by dilution of the incoming mixture as it enters and fills the cylinder.

A series of pictures on page 2 show how loop scavenging works and the dilution of the incoming mixture by residual exhaust gas and the supercharging effect of the expansion chamber. http://www.fluent.com/solutions/automotive/ex204.pdf

The less dilution of the incoming mixture as it fills the cylinder and then down into the first part of the exhaust port/expansion chamber is the aim of improving scavenging flow patterns.

The better the separation between the fresh mixture and the exhaust gas the less "HALF FUCKED" the new mixture is when the bulk of it that has been drawn into the exhaust tract is energetically pushed back into the combustion chamber.

Scavenging flow patterns and expansion chamber supercharging is all about removing the exhaust gas while minimising the dilution of the incoming mixture ie., scavenging efficiency, and how much fresh charge is squeezed back and then trapped in the cylinder.

.

B.Crump
21st July 2009, 20:23
DKW and NSU had them

what bikes are they? i dont know much about bikes that arnt main streeam

diesel pig
21st July 2009, 21:45
what bikes are they? i dont know much about bikes that arn't main stream

He's talking about motorcycles that were raced in GP's 70 years ago.

SS90
22nd July 2009, 03:12
J

You strike me to be one of these people that can read a book, or article about something, pick up what the book is saying and use the technical jargon to make it seem like you know what your on about. You don't seem to be able to think outside the square, nor change a preset view on something even though from an outsider looking in, you have been wrong! (as everyone is at some stage or another)



Your confusing me with Teezeetreefiddy.

So, what exactly have I been wrong about, given your "expertise" in two stroke tuning.......(nice expansion chamber by the way.........):rolleyes:

Maybe you could list 3 things I have been wrong about.......... (I don't think you can)

SS90
22nd July 2009, 03:24
One would think that a 2T motor that minimised or eliminated the charge lost down the pipe, but pushed all the exhaust out would be rather desirable - that doesn't imply a lot of charge going out the pipe is desireable...?



My experience tells me that is quite correct.

The fact that a (normally aspirated two stroke fitted with a SUITABLE expansion chamber) (in my opinion) simply DOES NOT qualify as a "supercharged" engine, any more than power valves do (because, a power valve improves the VE of an engine.....does that make a power valve assembly a supercharger?....a mechanical one at that!), or perhaps even a Reed valve? That increases VE as well (sort of)

Because IF that was true, then all 2 strokes would be banned in MotoGP!

Would you consider larger valves in a four stroke engine "super chargers"? because larger (or multiple) valves increase the VE of a 4 stroke engine, if so, an engine with mulitple valves, is a "supercharged" engine, and the (bigger or multiple) valves are "mechanical superchargers"



If it could be considered a "supercharged" engine, such efforts to keep the charge inside the cylinder would be negated, and we could increase our power by simply increasing the size of the transfer ports (angles required by scavenge patterns REDUCE the area of the ports)

And, as such, we could simply design expansion chambers that "supercharge" the cylinder (an easy task, if it where true), ignore all the efforts of the last hmmmm....... 50 years and have our transfers pointing straight across the bore.......

Fooman, you seem well schooled,(and appear to be presenting a (thankfully) unbiased position) and I see that you advocate that "supercharged" doesn't mean "how much air you can stuff in", rather "how much FRESH charge you can put in AFTER extracting the old charge"

In my opinion, basically, a Two stoke (currently) has a reletively LOW VE, due to the SUBSTANTUAL LOSSES inherent in ALL (current) two stroke engines, not the least of which is the fact that the (returning) fuel/air/particle matter is as far removed from "fresh charge" as can be.

I'm not saying that this "returning over scavenged" charge is "unusable", but, because if this (as one example) you shouild not consider a two stroke (with expansion chamber) as "supercharged"

That is, because of the LOSSES, (inclusion of particle matter along with charge dilution) a two stroke can not be considered "supercharged".

The FIM seem to see it that way as well!

I don't see the effect of increasing the negative pressure of the cylinder on the intake stroke, combined with returning "over scavenged" charge back into the combustion chamber as "supercharging".

Granted though, it would be correct to say "there is a Dynamic Supercharging effect" (meaning the increased negative pressure in the cylinder caused by the expansion chamber.

But that's not "supercharging"

SS90
22nd July 2009, 03:32
Heres an example of "supercharging" being referred to in regards to the action of the expansion chamber. 3/4 of the way down the page.
http://www.southernskies.net/page_info/runningtwostrokeengine.html

This pulse is timed to reach the exhaust port after the transfer ports close, but before the exhaust port closes. The returning compression wave pushes the mixture drawn into the header by the negative pressure wave back into the cylinder, thus supercharging (a bigger charge than normal) the engine. The straight section of pipe between the two cones exists to ensure that the positive waves reaches the exhaust port at the correct time:

Ok, this is where alot of people get a little lost.


You must be VERY wary of what you read on the net.

I concede that you could consider there is a slight "Dynamic supercharging effect" from an expansion chamber.


However, this "effect" does not constitute a "supercharged engine", anymore than an airbox (or power valve) does.

I feel it is important to note the difference when designing an exhaust that is suitable for a given situation.

If you enter in to the task with the concept that "an expansion chamber "supercharges" a cylinder", then you (in my opinion) are going to neglect important factors in both your engine design as well as your pipe design.

As with "scetchy racers" design, he demonsrarted a lack of knowledge when it came to checking his final calculations, and ended up with a lemon.

(F5Dave pointed out "a few" mistakes in the design)

It's something we all have done, but some experience would have told him that it was "off"


For example, you need ALOT more information to design an expansion chamber than simply exhaust port specs and intended RPM range.

SS90
22nd July 2009, 03:48
.


SS90 you’re starting to get it, the supercharging thing.

And now there is the loop scavenge systems flow patterns and how they are designed so the incoming mixture push's the exhaust ahead of it while minimizing mixing and there by dilution of the incoming mixture as it enters and fills the cylinder.

A series of pictures on page 2 show how loop scavenging works and the dilution of the incoming mixture by residual exhaust gas and the supercharging effect of the expansion chamber. http://www.fluent.com/solutions/automotive/ex204.pdf

The less dilution of the incoming mixture as it fills the cylinder and then down into the first part of the exhaust port/expansion chamber is the aim of improving scavenging flow patterns.

The better the separation between the fresh mixture and the exhaust gas the less "HALF FUCKED" the new mixture is when the bulk of it that has been drawn into the exhaust tract is energetically pushed back into the combustion chamber.

Scavenging flow patterns and expansion chamber supercharging is all about removing the exhaust gas while minimising the dilution of the incoming mixture ie., scavenging efficiency, and how much fresh charge is squeezed back and then trapped in the cylinder.

.

hahahaha,

Your becoming quite the legend in the workshop here Bucketracer, can you PM me your address, my boss want's to send you a Tshirt! (serious!)

SS90
22nd July 2009, 03:53
then why do we have a chamber and not a straight pipe ??????? like a 4 stroke ????????

Erm,

Not all expansion chambers are designed the same.
Look at Kartsport for an example.

Buckets4Me
22nd July 2009, 06:58
Erm,

Not all expansion chambers are designed the same.
Look at Kartsport for an example.


ye but they are nothing like a 4stroke ????
any why is that ???? I'm even more confused with that answer

SS90
22nd July 2009, 07:10
ye but they are nothing like a 4stroke ????
any why is that ???? I'm even more confused with that answer

Really?

Perhaps if you and your mates spent less time frantically trying to prove me wrong (and not actually reading what I write) all this may be easier to follow....... it get more and more disjointed every night I read it.

I wonder if you have less interest in two stroke tuning, and more interest in (trying, though never succeeding) to prove me wrong.

Just for fun, roll back read THE WHOLE thread...... you will see what I mean.

There is a dramatic difference between debate and pointless critisism...

TZ350
22nd July 2009, 07:27
Your confusing me with Teezeetreefiddy.

So, what exactly have I been wrong about, given your "expertise" in two stroke tuning.......(nice expansion chamber by the way.........):rolleyes:



SS90 you are entertaining , but not very informative, no one would confuse my coherent posts complete with pictures diagrams and references with your to date insult filled error prone rambling’s.

That was Sketchys first attempt at a chamber, there was no need to mock him.

Your whole thread seems based around sparing with people and maybe thats your need but my advice is, ignore them and explain your opinions in a coherent way so we may all appreciate them.

Like most of us I have a traditional understanding of the function of the expansion chamber and scavenge patterns. I would have liked to have read about your understanding of them.

I see people have posted links to pictures or other web pages that have demonstrated their point, because it clarified what they were saying, you could do that too, and a few hand drawn sketches would help too.

But you went on and on completely missing the chance to explain your views.

I for one am interested in what you have to say.

.

SS90
22nd July 2009, 07:30
SS90 you are entertaining , but not very informative, no one would confuse my coherent posts complete with pictures diagrams and references with your insult filled error prone rambling’s.

.

I simply give as good as I get Teezee.

The first stones where thrown from your "camp".

gav
22nd July 2009, 07:36
Really?

Perhaps if you and your mates spent less time frantically trying to prove me wrong (and not actually reading what I write) all this may be easier to follow....... it get more and more disjointed every night I read it.

I wonder if you have less interest in two stroke tuning, and more interest in (trying, though never succeeding) to prove me wrong.

Just for fun, roll back read THE WHOLE thread...... you will see what I mean.

There is a dramatic difference between debate and pointless critisism...
Right here we see your enduring fault SS90. Rather than answer a query and try and help someone understand the difference between say a Kart pipe and a bucket pipe, you instead post up nothing of value and suggest he goes back and reads the whole thread. Which if he does still won't answer his query regarding the pipe design he asked you about.

SS90
22nd July 2009, 07:46
Right here we see your enduring fault SS90. Rather than answer a query and try and help someone understand the difference between say a Kart pipe and a bucket pipe, you instead post up nothing of value and suggest he goes back and reads the whole thread. Which if he does still won't answer his query regarding the pipe design he asked you about.

hmm, perhaps due to his constant critical posts, I don't feel the desire to help him.

If, he hadn't behaved in such a way, we would already have discussed that. Instead we AGAIN find our selves at this point.

As usual, they just started immediately trying to disprove my statement (which AGAIN they have failed to do)

Does an expansion chamber "supercharge" a cylinder?

NO.

The more time that is wasted with such nonsense, the longer it takes to get the innformation out.

Logical?

I'm quite happy to have people disagree with me, but, I have posted nothing incorrect.

Can you show me otherwise?

I am GENUINELY interested in seeing what I have posted that is incorrect.

SS90
22nd July 2009, 07:53
SS90 you are entertaining , but not very informative, no one would confuse my coherent posts complete with pictures diagrams and references with your to date insult filled error prone rambling’s.

That was Sketchys first attempt at a chamber, there was no need to mock him.

Your whole thread seems based around sparing with people. My advice is, ignore them and explain your opinions in a coherent way so we may all appreciate them.

I for one am interested in what you have to say.

.

Well, Teezee, perhaps you could "gently encourage" your "entourage" not to make such personal attacks on me, and, have open discussion on such things, rather than "your wrong" (and then not proving me wrong)

secondly. What errors have I made?

please show some examples.

It would be nice if you could back that statement up.
In regards to Sketchy chamber...... I first saw the post, but said NOTHING....... it wasn't until HIS SECOND ABUSIVE POST that I simply "gave it back". Yup, I have made 2 absolute lemons of pipes (it's normal to name a pipe when you design it here..... I called my first one "DAS LIESTUNG DIEB" (the power thief) and I learned from it. So I (had) compassion for him.....he has twice posted abusive comments, what does he expect, chocolates?

Cajun
22nd July 2009, 07:55
Mod Warning

We are getting sick of the complaints about abuse/attacks in this thread etc

If you guys can not keep it clean the whole thread will be moved to pd.

TZ350
22nd July 2009, 07:55
I simply give as good as I get Teezee.

The first stones where thrown from your "camp".

Please.........

.

SS90
22nd July 2009, 08:05
OK Teezee,

Please, direct me to a post of mine this is incorrect.

I think it would be fair since you made the claim.

TZ350
22nd July 2009, 08:05
.
Well, Teezee, perhaps you could "gently encourage" your "entourage" not to make such personal attacks on me,
.


I expect they thought they were giving as good as the got.

The boys did get a tune up about that,

have you felt slighted recently?

Can you give me an example.
.

gav
22nd July 2009, 08:08
hmm, perhaps due to his constant critical posts, I don't feel the desire to help him.

If, he hadn't behaved in such a way, we would already have discussed that. Instead we AGAIN find our selves at this point.

As usual, they just started immediately trying to disprove my statement (which AGAIN they have failed to do)

Does an expansion chamber "supercharge" a cylinder?

NO.

The more time that is wasted with such nonsense, the longer it takes to get the innformation out.

Logical?

I'm quite happy to have people disagree with me, but, I have posted nothing incorrect.

Can you show me otherwise?

I am GENUINELY interested in seeing what I have posted that is incorrect.

Well as far as the Supercharging part I posted the reference where some describe the effect of the pipe as supercharging the cylinder. You asked for where the term supercharging was used to describe the pipes action and I posted it.
But I agree, this term is very misleading and I'm sure most regard supercharging as relating to a mechanical supercharger that forces extra volume into the cylinder driven by a belt or a gear.
But anyway, you have plenty of opportunity to rise above their (whoever they are) actions, but still you find it necessary to play games as well. I thought school holidays were over?

SS90
22nd July 2009, 08:08
Hmmm,
I'm quite thick skinned, so I am able to ignore most of it, but if you are genuinely interested perhaps we could look at sketchy's chamber (the original design) and "reverse engineer" it.

Looking at what each section means.

Maybe that is a good place too start.

SS90
22nd July 2009, 08:14
Well as far as the Supercharging part I posted the reference where some describe the effect of the pipe as supercharging the cylinder. You asked for where the term supercharging was used to describe the pipes action and I posted it.
But I agree, this term is very misleading and I'm sure most regard supercharging as relating to a mechanical supercharger that forces extra volume into the cylinder driven by a belt or a gear.
But anyway, you have plenty of opportunity to rise above their (whoever they are) actions, but still you find it necessary to play games as well. I thought school holidays were over?

Hmm, yea My girlfriend doesn't get why I even bother....I generally do ignore it, but, you know, eventually you get drawn into the shit, it's just human nature.

In regards to the supercharging, yes, I agree, it's a terminology thing.

Fooman suggested "a dynamic super charging effect", and I think that would be the most accurate term.

The fact that the engine is not "supercharged" (it's a very very common mistake) is why you have to pay such careful attention to other factors.

Like f5dave said, a new pipe and an old cylinder (I would expand that to engine rather than just cylinder) don't always work......... high "extraction" designed pipes is one main reason.

Crankcase volumes (correct for the situation) and intake resonance are important factors.

TZ350
22nd July 2009, 08:16
OK Teezee,

Please, direct me to a post of mine this is incorrect.

I think it would be fair since you made the claim.

I think there are a few but keeping it topical, any post where you claim that there is no supercharging effect from the expansion chamber.

A lot of literature says there is.

You will need to do better than a "because I say so approch". A coherent well thought out illustrated explination of your view could change my mind, untill then I have to hold to the conventional wisdom.

In holding to the conventional wisdom, its not for me to prove you wrong. Its for you to explain yourself in a way that allows me to see your right.

.

TZ350
22nd July 2009, 08:20
.



But I agree, this term is very misleading and I'm sure most regard supercharging as relating to a mechanical supercharger that forces extra volume into the cylinder driven by a belt or a gear.
.


Or it could be equally misleading to think supercharging has to be a mechanical device.

.

TZ350
22nd July 2009, 08:28
The fact that the engine is not "supercharged" (it's a very very common mistake) is why you have to pay such careful attention to other factors.
.


You say its a "fact" its not supercharged, thats a strong statment in the face of so many sources saying it is.

As your the lone voice, can you explain why the strong negative pulse then positive pulse that charges the cylinder is not supercharging.

The negative pulse can be 7psi and the positive pulse much the same I expect. This is about the same pressure as delivered by mechanical superchargers fitted to road cars.

Maybe walk us step by step through the whole expansion chamber.

.

SS90
22nd July 2009, 08:33
I think there are a few but keeping it topical, any post where you claim that there is no supercharging effect from the expansion chamber.

A lot of literature says there is.

You will need to do better than a "because I say so approch". A coherent well thought out illustrated explination of your view could change my mind, untill then I have to hold to the conventional wisdom.

In holding to the conventional wisdom, its not for me to prove you wrong. Its for you to explain yourself in a way that allows me to see your right.

.

Teezee,

I have already conceded there is a "supercharging effect" caused by the expansion chamber (actually I have never claimed there wasn't)

However, what I am saying is that " A conventional normally aspirated two stroke engine IS NOT "supercharged"

A "supercharge effect" does not constitute a "supercharged engine" anymore than an air box does.

Do you know of any literature that shows that an expansion chamber "supercharges" a cylinder (not just provides a supercharge effect)

I don't feel I am arguing over semantics.

These are important differences. (supercharge effect, opposed to actually being "supercharged"

Fooman posted above on what is considered "supercharged"

We have already established that simply increasing VE is NOT supercharging (or else power valves would be considered "mechanical superchargers"), or in the case of a 4 stroke, multiple valves (which also increase VE)

So, an expansion chamber will increase the VE of a two stroke engine......(so done by applying a "dynamic supercharger effect")

That doesn't make it "supercharged"

CookMySock
22nd July 2009, 08:41
That doesn't make it "supercharged"It's pretty clear the cylinder has a greater-than-atmo charge in it.

What shall we call it then? Pseudo-supercharged? Supercharged but not quite? *****charged? PosVEcharged?

You should become a patent attorney.

Steve

TZ350
22nd July 2009, 08:44
.

The advantage of a mechanical supercharger is that it delivers over a wide rev range where as a resenant supercharger like an expansion chamber, only works over a limited rev range.

.

SS90
22nd July 2009, 08:52
.

The advantage of a mechanical supercharger is that it delivers over a wide rev range where as a resenant supercharger like an expansion chamber, only works over a limited rev range.

.

Hang on,

But have you got any literature to show that it actually "supercharges" a cylinder?

Supercharging effect yes, does this "supercharge" the cylinder?.......no.

SS90
22nd July 2009, 08:56
It's pretty clear the cylinder has a greater-than-atmo charge in it.



Steve

Greater than atmosphere charge?
Every internal combustion engine has greater than atmosphere charge in it.

Erm, does that make it supercharged?

Fooman posted above what constitutes a supercharged engine.

TZ350
22nd July 2009, 09:10
.
Supercharging effect yes, does this "supercharge" the cylinder?.......no.
.


SS don't lose sight of the fact that the expansion chamber does more than supercharge the cylinder.

.

SS90
22nd July 2009, 09:17
SS don't lose sight of the fact that the expansion chamber does more than supercharge the cylinder.

.

Erm, Yes Teezee I am quite aware of that.

However, I feel it is important to understand how an expansion chamber works "piece by piece" (as it where) so we all can get a better understanding of things.

That's why I post on this site.

bucketracer
22nd July 2009, 09:29
.
Ok Skunk, I have posted this run in the ESE thread, but here is an example of how an expansion chamber DOES NOT "SUPERCHARGE" a cylinder.

The same exhaust,head,primary compression,ignition (and timing) flywheel etc.....

Only the scavenge pattern has been changed (dramatically).........

If a two stroke chamber "supercharged" a cylinder, why would keeping the air/fuel mixture in the cylinder (stopping it heading out the open exhaust port) make such an improvement?

This graph shows otherwise.
.
.

If TZ350 posted this he would have shown us drawings of the before and after pattern and an explination of how the changes better prevents the mixture heading out the exhaust.

Without an explination your graph is just a picture with lines.

.

SS90
22nd July 2009, 09:47
.

If TZ350 posted this he would have shown us drawings of the before and after pattern and an explination of how the changes better prevents the mixture heading out the exhaust.

Without an explination your graph is just a picture with lines.

.

With my heart in my mouth just replying to you Bucketracer (and expecting the usual abuse) I'll give it a shot.

The fact is that Teezee didn't post anything about scavenge patterns, because in the ESE thread, he was unaware of the concept.

Don't take that as an insult, it's just a fact.

I pointed him in the direction of Honda RS125's, (and their scavenge patterns) as a VERY good place too start (however, I would not recommend copying them for a disc valve two stroke, but it is a good place to learn)

Yes, he went to the effort of measuring them, then posting them. Good for him.

I won't simply post designs or important specs that I use, however I will attempt to generate conversation so we can all learn and expand our knowledge, and PERHAPS we can all improve our ideas.

gav
22nd July 2009, 11:16
What was the chamber? I will sell you one for €500 (incl postage), it will only fit a small frame Vespa (sorry) But it will be hand made in Germany (by a Kiwi)

Was there a chamber? errrr YES.

What did I do to achieve the scavenge effect? Paid attention and accepted advise from people, along with intelligent conversation and constructive critisisim, along with leaning "how and why" other manufacturers did things.

I don't say that the chamber was doing absolutely "nothing", I use this as an example to show that if the chamber was "supercharging" the cylinder, then improvements in the scavenge patterns would have no effect.
Have you got a chart to show this same engine being run with a standard exhaust and then a chamber so we can see the difference that the chamber makes (or not :rolleyes: ) to the engine?

Skunk
22nd July 2009, 12:10
Does an expansion chamber "supercharge" a cylinder?

NO.I have already said it was a throw away term to loosely describe one effect of a chamber. I note you have gone to great lengths to say I'm wrong (which in specific terminology I am) but haven't said anything about why it's wrong and clearly explain anything about what is going.
I even asked you directly and you avoid answering.


In regards to the supercharging, yes, I agree, it's a terminology thing.Oh, really?


But have you got any literature to show that it actually "supercharges" a cylinder?Your evidence is?...


I won't simply post designs or important specs that I use, however I will attempt to generate conversation so we can all learn and expand our knowledge, and PERHAPS we can all improve our ideas.Now would be a good time to start. I haven't seen any 'knowledge' from you and we're a few pages into this thread now...

bucketracer
22nd July 2009, 12:12
With my heart in my mouth just replying to you Bucketracer (and expecting the usual abuse) I'll give it a shot.

The fact is that Teezee didn't post anything about scavenge patterns, because in the ESE thread, he was unaware of the concept.


I doubt that he was unaware of the concept, you assume too much.

And from the last few pages can you give me an example of my abuse, I can certainly show you many examples of yours including much childishness.

.

F5 Dave
22nd July 2009, 12:14
Re Sketchy;


. . .
It's something we all have done, but some experience would have told him that it was "off"


For example, you need ALOT more information to design an expansion chamber than simply exhaust port specs and intended RPM range.
I don't think Sketchy claims to have much experience, but he is learning. I certainly didn't know anywhere near as much at 19. & I doubt you did either. His approach has been fairly well researched, methodical & definitely enthusiastic.

None of which changes his observation. Your acidic and argumentative personality totally prevents you from playing well with others. I'm hardly surprised you are getting the flack you are. And I bet it has affected your ability to learn as winning the argument seems the most important thing,


. . . even if you can't convince others that you have won.

bucketracer
22nd July 2009, 12:19
Yes, he went to the effort of measuring them, then posting them. Good for him.

I won't simply post designs or important specs that I use, however I will attempt to generate conversation so we can all learn and expand our knowledge, and PERHAPS we can all improve our ideas.

.

Yes and good for us.

TZ does not post designs or important specs either

but he does explain important concepts very well with drawings Etc so you can design your own.

And he is totaly open with sharing his knowledge and allways acknowledges sources like Thomas yourself and others.

.

Buckets4Me
22nd July 2009, 16:04
I have already conceded there is a "supercharging effect" caused by the expansion chamber (actually I have never claimed there wasn't)

However, what I am saying is that " A conventional normally aspirated two stroke engine IS NOT "supercharged"

A "supercharge effect" does not constitute a "supercharged engine" anymore than an air box does.

These are important differences. (supercharge effect, opposed to actually being "supercharged"


:argue: I'm getting more and more confused

so if you ram more air (and fuel) into an engine you can call it a supercharger affect but not supercharged ????

and also if the chamber dosent ram more air into the engine than it would have had without it then what dose it do ????

:blank: someone answer me come on

NOS is not supercharging the engine watchout TAUPO :banana:
I'm going to beat you all to the first corner :drool:
then I'm going to brake realy hard so you all had better give me lots a room
then I'm going to beat you all up the hill (and brake hard again)
then I'm going to cost down the hill braking hard and early (I'm to scared to realy gass it out there)
and beat you all up the hill again :banana:

gav
22nd July 2009, 17:01
With all that braking going on, maybe time to develop a KERS system for the bucket?

Ooky
22nd July 2009, 18:26
Note havn't read last 3 pages turned in to a cock size comp so i skipped ahead

The exhaust uses the pressure waves created by the gasses exiting from the combustion chamber into the exhaust port. These waves have the caratteristics of reflecting as a negative wave (suction) if they meet an open end of a tube. On the other way if they encounter an closed end of a tube they reflect as a positive wave (stuffing). The waves move indipendently from the movement of the gas in which they travel. In comparsion to the gas flowing in the exhaust, they have a much higher speed. Similar to waves on the water; the water is still but the waves travel with an certain speed.

The main parts of an exhaust are; the header, the diffuser, the belly, the baffle cone, the tailpipe and the silencer. The diffuser is the “open end” of the pipe; it creates the suction wave. The baffle cone is the “closed end” of the pipe; it reflects the pressure wave, which does supercharge the cylinder. The steepness of the cones defines the strenght and duration of the reflected waves. The header and the belly section act as distancers, this way the needed timing of the waves can be tuned.

The next important thing is the tailpipe. The purpose of the tail pipe is to create and maintain the proper pressure and temperature inside the exhaust. It is very important to select the right diameter of the tailpipe; to big will result in poor performance, to small will result in a melted piston.

The silencer, as his name says, is needed to silence the sound. The most common type of silencer used has a perforated tube in the middle with glasswool around. The good side of this kind of silencer is that it efficiently reduces the sound level while creating little obstruction for the escaping gasses.

The phases
(Note; arrows show the gasses and their direction, the arcs show the pressure waves)

http://fpp.hamradio.si/roost/tech/exhaust/exhaust_files/image004.jpg
After the ignition the gasses in the combustion chamber begin to expand and move the piston towards the BDC.

http://fpp.hamradio.si/roost/tech/exhaust/exhaust_files/image006.jpg
The piston uncovers the exhaust port. The burnt gasses begin to escape from the combustion chamber at a high speed, this generates a pressure wave, which begin to travel into the header.

http://fpp.hamradio.si/roost/tech/exhaust/exhaust_files/image008.jpg
At this point the phase of scavenging in the cylinder with fresh mixture begins. The pressure wave reaches the diffuser where it reflects as a suction wave.

http://fpp.hamradio.si/roost/tech/exhaust/exhaust_files/image010.gif
The suction wave has reached the cylinder where it helps to pull out spent gasses and fill the chamber with fresh mixture. A part of the fresh mixture can escape into the exhaust. At this time the rest of the pressure wave that was not reflected as a suction wave reaches the baffle cone, where it reflects as a pressure wave

http://fpp.hamradio.si/roost/tech/exhaust/exhaust_files/image012.jpg
At this point the piston has closed the transfers, but the exhaust port is still open. The pressure wave reflected by the baffle cone reaches the cylinder and stuffs back the fresh mixture escaped into the exhaust. This is the way that a slight supercharge is created in twostroke engines.


Unluckyly the twostroke expansion chamber works only in a limited rpm range. The engine produces the maximum torque when the exhaust pulses enter in resonance with the opening of the cylinder ports. When the rpm are under the resonance of the exhaust, the suction wave reaches the cylinder too early, the transfers aren’t open so the suction wave can’t help suck out spent gasses and fill fresh mixture into the cylinder. On the other end when the rpm are too high the transfers are already closed by the piston moving upwards, so the suction wave is too late.

The rpm at which the pipe will be in resonance depend on the length of it and the temperature of the gasses. With a temperature change also changes the speed at which the waves travel. The higher the temperature, the higher is the speed at which the waves diffund. The higher is the wave speed, the higher are the rpm at which the engine will make power. We can see sometimes at races when the climate is cold, pipes are stripped with insulation that provide the optimal temperature.

Characteristics
http://fpp.hamradio.si/roost/tech/exhaust/exhaust_files/image014.jpg
The geometry of the pipe dictates the “character”. The length dictates the rpm at which the pipe enters in resonance. In a short pipe, in comparsion to a long one, the waves have to travel a shorter distance, this means that a short pipe will enter in resonance with the piston movement at a higher crank rotation speed. In short words; a long pipe will make power at low rpm while an short one will make power at high rpm.

The conicity of the diffuser and baffle cone determinate the length and amplitude of single waves reflected back to the cylinder. The higher the cone angle is, the shorter but with an greater amplitude the reflected wave will be. So an pipe with higher angle of the cones will make higher power, but in a narrower rpm range. Compared to a pipe with lower cone angles, an bike with such pipe will be more “nervous” to ride, the transmittion will be harder to tune up. It is in base to the type of engine and riding that the pipe has to be designed for. On a scooter with an engine with automatic variable transmission, the rpm range needed is narrower than the one for a bike with manualshift transmission, so pipes with higher cone angles can be used.
This graph shows the difference of shape of the power band on pipes with different angle of the cones.

Skunk
22nd July 2009, 18:46
< snippet >The main parts of an exhaust are; the header, the diffuser, the belly, the baffle cone, the tailpipe and the silencer. The diffuser is the “open end” of the pipe; it creates the suction wave. The baffle cone is the “closed end” of the pipe; it reflects the pressure wave, which does supercharge the cylinder. The steepness of the cones defines the strenght and duration of the reflected waves. The header and the belly section act as distancers, this way the needed timing of the waves can be tuned.Very informational post. Thank you.

Original web page is here (http://fpp.hamradio.si/roost/tech/exhaust/)

Buckets4Me
22nd July 2009, 18:49
thanks for that

explains what i thought was happening

and as a side note

when I had my bike up on the dyno
the hotter it got the more HP it made
measured the pipe at around 360 oC at the belly?? middle between cones

19hp not to bad I thought
time to get it back and tune it up a bit as have only played with timing and jetting at the track :rolleyes: :clap:
also I have a few spare pipes to try

and I may just take a streight piece with me to see what difference a chamber and a non chamber make :P

koba
22nd July 2009, 20:00
has any one supercharged a 2 stroke?

Wow! Look at what you started!

Does that deserve a KB reward for 'Most inflammatory innocent question'?

bucketracer
22nd July 2009, 20:02
.
The fact is that Teezee didn't post anything about scavenge patterns, because in the ESE thread, he was unaware of the concept.

.

The fact is that SS90 didn't post anything about other expansion chamber functions, before in the 2-stroke tuning thread, because SS was unaware of them.

Untill TZ350 pointed it out to him. Post 339 and 426

Anything you read on here now from SS90 about how an expansion chamber is more than a supercharger is because of TZ's tip to him.

So SS90, its easy to drop a vague hint and then try and claim all the credit, any one could do it.

.

koba
22nd July 2009, 20:03
Well, Teezee, perhaps you could "gently encourage" your "entourage" not to make such personal attacks on me, and, have open discussion on such things, rather than "your wrong" (and then not proving me wrong)


I'm not part of anyones "entourage" but I still agree with Sketchys naughty post. That judgement of mine is based on your posts, not anyone elses.

Skunk
22nd July 2009, 20:28
I simply give as good as I get Teezee.

The first stones where thrown from your "camp".
I'm in my "camp". Your "informational" posts make me respond like I do. I have only met TZ350 twice so I can hardly be part of his "entourage".

Buckets4Me
22nd July 2009, 20:29
Wow! Look at what you started!

Does that deserve a KB reward for 'Most inflammatory innocent question'?

and can we get one for the person that writes the most words without saying anything usefull ?

Skunk
22nd July 2009, 21:29
Here's something useful: http://www.bimotion.se/Theory/Theory.html

bucketracer
23rd July 2009, 03:40
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Mine's supercharged - it has a chamber.
.




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I'm not too sure that I would subscribe to an expansion chamber being a "supercharger"........

A supercharger is essentially a compressor that forces air into an engine......An expansion chamber doesn't do this.
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.
A "supercharger" is forced induction.

Ergo, an expansion chamber, cannot "force induce" an engine.
.




.
Because if we use that definition, "supercharging" is ANYTHING that forces air into an engine, and CLEARLY an expansion chamber does not do that.
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.
all the attention would be on increasing the (I believe non-exsistent) "supercharging" effect of the chamber.
.





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I have already conceded there is a "supercharging effect" caused by the expansion chamber (actually I have never claimed there wasn't)
.


SS90 you say you never claimed there wasn't a "supercharging effect", well here is a bit of history from the supercharging dance.

And SS90, Skunk didn't claim his expansion chamber was a supercharger either.

So how ever did you manage to make such a drama out of his reference to the "supercharging effect".

You could have just left it at my earlier post.


I am sorry your wrong again. Supercharging is not just forced induction at the inlet. Its forced induction per see.

As I said before, however you squeeze extra air or air/fuel mixture into an engine above what it can normally aspirate for its self is supercharging and is most certainly deliberate in a 2-Stroke.

And from the Oxford Dictionary

supercharger
• noun a device that increases the pressure of the fuel-air mixture in an internal-combustion engine, thereby giving greater efficiency.

http://www.askoxford.com/concise_oed/supercharger?view=uk

The expansion chamber most certainly can supercharge a 2-Stroke.

Please back your opinion with references otherwise its just your opinion.

.
.

So we got past semantics and have established the supercharging effect of the expansion chamber.

Even better would be a mechanical supercharger at the inlet side and direct fuel injection. Then we could have a real fuel efficent supercharged 2-Stroke. I guess with the developments in DI its looking possible.

The problem with early attempts at supercharging 2-Strokes was their thirst as the Schnurle loop scavinging system was unable to stop a lot of the fuel mixture being lost out the exhaust and expansion chambers as we know them, with their plugging effect had not yet been developed.

Early Supercharged DKW http://www.motorbase.com/auctionlot/by-id/1706703174/

Now, thats what I call a "real" supercharged 2-Stroke and I suspect so does SS90 and with some modern thinking and maybe with a turbo as the supercharger you could have a real weapon.
.

TZ350
23rd July 2009, 22:02
.

Bucketracer, I know a sideshow easily distracts SS90 and I could quote him and try and embarrass him too, but if you’re interested in what he has to say, don’t.

SS90

My understanding is that the loop scavenge system was first patented in 1924 by Dr E Schnurle and the original patent drawings clearly show the transfer/scavenge streams flowing in, up, over, and out the exhaust port. Carefully aimed transfer ports create this scavenging flow pattern.

But I am not sure where the term "closed loop" you use comes from.

My understanding is:-

The scavenging flow pattern serves three purposes. 1, to drive the remnants of the exhaust gas from the cylinder. 2, to minimize mixing of the incoming fuel mixture with the outgoing exhaust gas as this mixing dilutes the incoming fresh charge. And 3, preventing as much as possible, short circuiting of the incoming fresh charge directly out the exhaust port.

I think the expansion chamber serves three major functions. 1, on its negative pressure suction pulse, an extraction effect of the exhaust from the cylinder and assisting the transfer of the fresh mixture. This suction pulse can travel from the exhaust port to the carburetor mouth.

2, on its positive pulse there is a slight supercharging effect but its main purpose is a plugging effect that assists the scavenge pattern trap as much fresh charge as possible in the cylinder.

And 3, there is an elevated pressure within the expansion chamber set by the bleed down stinger. This internal working pressure and the slight supercharging effect ensure the final pressure of the fresh mixture trapped within the cylinder as the exhaust port just closes is higher than it would have been.

So we have Scavenge Pattern, Suck to Extract and assist Transfer, Blow to Block, Working Pressure, Slight Supercharging Effect to create higher cylinder pressure.

Brought about by transfer port shapes and angles, port time areas, and expansion chamber tuned length cone lengths and angles, with each playing their own part.

I am not married to these ideas or my understanding of them and am interested in anything you can tell us about the function and subtitles of the various elements that make up the 2-Stroke system.

.

SS90
24th July 2009, 03:16
.






My understanding is:-

The scavenging flow pattern serves three purposes. 1, to drive the remnants of the exhaust gas from the cylinder. 2, to minimize mixing of the incoming fuel mixture with the outgoing exhaust gas as this mixing dilutes the incoming fresh charge. And 3, preventing as much as possible, short circuiting of the incoming fresh charge directly out the exhaust port.

I think the expansion chamber serves three major functions. 1, on its negative pressure suction pulse, an extraction effect of the exhaust from the cylinder and assisting the transfer of the fresh mixture. This suction pulse can travel from the exhaust port to the carburetor mouth.

2, on its positive pulse there is a slight supercharging effect but its main purpose is a plugging effect that assists the scavenge pattern trap as much fresh charge as possible in the cylinder.

And 3, there is an elevated pressure within the expansion chamber set by the bleed down stinger. This internal working pressure and the slight supercharging effect ensure the final pressure of the fresh mixture trapped within the cylinder as the exhaust port just closes is higher than it would have been.

So we have Scavenge Pattern, Suck to Extract and assist Transfer, Blow to Block, Working Pressure, Slight Supercharging Effect to create higher cylinder pressure.

Brought about by transfer port shapes and angles, port time areas, and expansion chamber tuned length cone lengths and angles, with each playing their own part.

I am not married to these ideas or my understanding of them and am interested in anything you can tell us about the function and subtitles of the various elements that make up the 2-Stroke system.

.

I guess, that would about cover the basic aspects.

As you say there is a "Supercharging effect" (not meaning a supercharged cylinder) and yes, it operates as such.

Dr Schnürle (yes, I have read about 2/3rds of his work) described (in the later tests) what would translate as "Turning back flow" when observing the air fuel mixture in relation to the "swirling pattern" formed inside the cylinder, and the fresh charge.

I.E, he noticed that there was a vast improvement in the amount of good air/fuel mixture that stayed in the cylinder, rather then following the exhaust gasses out.

This is why I consider that the EASIEST way to describe the Schnürle loop system is "keeping as much of the air/fuel mixture in the cylinder"

How it actually does that, (the separation of burnt gasses etc) is a little more complicated.

The BEST way to see this is by building a test rig as described by Gordon Jennings.

To actually see (and describe what you are seeing) makes a big difference to your understanding and comprehension of what aspects to pay attention to.

Something else he noted (again, in later work) is that while the system "reduces short circuiting", there is no real way to 100% stop the "short circuiting" completely........ and, the air/fuel mixture that FIRST enters the cylinder is the MOST LIKELY to short circuit.

This is VERY VERY important to understand.

He surmised that if you could perfect the "schnürle loop", (i.e, no short circuiting at all) you would essentially have a "closed loop system" (as far as the fresh air/fuel mixture was concerned.)

This finding was (in my opinion) the most important thing (other than the actual "schnürle loop" it'self).

Bearing in mind, that the original system comprised of only 2 transfers,(and obviously no "expansion chamber" this would indicate (and subsequent recreated tests of my own backed it up) that any improvements on the "schnürle loop" system come from REDUCING THE LIKELYHOOD of "short circuiting" earlier in the cycle.

If you can achieve this, then combined with an expansion chambers ability to return the (now reduced quantity of combustible air/fuel) you are starting to make more power, and as such, your expansion chamber design needs to alter in order to take advantage of this.

This is the primary reason why (like F5dave said) "a new pipe does not really work on an old cylinder design"

In the 40's many many companies (particularly German,but a few French companies where on the ball as well) worked very hard on this very thing (in fact, in 1941 a solution was found) quiet simple, and essentially the "orbital" engines (first designed in the 70's) are simply a development of this concept.

They operate (remember 1941) simply by "sacrificing" externally introduced compressed air early in the cycle, so that, as the FIRST air to enter the cylinder through the transfers is THE MOST LIKELY to "short circuit", this "sacrificial air" heads out the exhaust port, rather than the fresh air/fuel mixture.

This system works really well (you can already get "orbital" equipped engines, which, as I say are simply extensions of this early work.

There are a few examples of these engines here in Europe, and all from the late 30's and early 40's.

It is a little "clumsy" simply "masking" a scavenge pattern fault, but particularly in the case of single transfers, it is the best solution.

Forgoing the complications of such setups, you will notice that no manufacturer has (mass-produced that is, well YET.......next year MAYBE) such an engine.

The reason for this is with further understanding of multiple transfers, it has become clear that you can dramatically reduce the "early short circuiting" (because again, THE AIR FIRST ENTERING THE CYLINDER THROUGH THE TRANSFERS IS THE MOST LIKELY TO SHORTCIRCUIT) with "well designed scavenge patterns" (but, only with multiple transfers), but even with such designs, there still is SUBSTANTUAL short circuiting.

Of course, such designs reduce effective transfer area, but it is an acceptable trade off.

Have a look back at the ESE thread where I mention a concept for your GP125 scavenge patterns (in relation to the likely shortcircuiting from the somewhat strange secondary transfer placement compared to the rear boost port), combined with using the dished piston to your advantange.

That concept comes from my experience with different transfer angles.

Also, much earlier in this thread I used the Quattrini 125 cylinder as an example.

I mentioned that I had spoken to a few customers regarding the (I think) meagre "plug and play" power results (17.1PS) compared to the customers mentioning "it uses alot of fuel" if it was pushinng out 28PS, and "using alot of fuel", then I would not be concerned....but this indicates there is short circuiting (wasted fuel)...... I posted the original port angles, and suggested I would change the boost port angle to remedy this.

What's your opinion on an angle that would improve this Teezee?

Another thing I recommend is to (if you have the resources) test all your initial "concepts" out on an engine with no expansion chamber...... if you can make more power with a cylinder (in regards to keeping more fuel/air mixture in the cylinder) that does not have the advantage of an expansion chamber returning "overscavenged" mixture, you can better gauge your gains.

Introducing the expansion chamber after such tests will only increase your power, and take away confusion over pipe design VS scavenge pattern design.

So, basically, because of the amount of gain (even today there is more to come) you make from more efficient scavenge patterns alone, this is an example of how, despite the "supercharge effect" of an expansion chamber I don't consider a two stroke cylinder to be "supercharged"

If it was, like I say, we would concentrate our efforts on increasing this (I believe non exsistant "supercharger"...even though I agree you could consider there is a "dynamic supercharging EFFECT") rather than keeping the fuel in the cylinder.

I don't feel ANYONE has to agree with me on that, by the way, everyone is entitled to their own opinion,be it experienced or not!
But expansion chamber design is not only influenced by cylinder design alone.

already covered (but not in a comprehendable fashion) has been some aspects of crankcase volumes.

When you have "modern porting" (to coin a phrase) combined with "a modern exhaust", the requirements of your crankcase volumes change dramatically......(as I have previously mentioned)

I have previously referred to Japanese research from the 60's which I pointed out was only applicable in certain situations (chamber and cylinder design for example) there is plenty of information available on what is considered "the new general crankcase volume"

My personal research has only confirmed this to be true. (the last time I posted a picture of a crank I cut, it was 1.4:1, I know go lower, with substantual gains)

I assure you that anything (with a "modern set up") With a primary compression ratio OVER 1.3:1 is only detrimental.

In the case of (for example) Team ESE GP125 (with the old porting/pipe) then closer to 1.5:1 is correct.

I find the correct crankcase volume (for a given situation) is (mostly) dependent on expansion chamber design.

And then, the inverse must be true, in that, Crankcase volume must be a part equation in expansion chamber design (among other factors)

A few years ago, (due to expansion chamber design) I had (I thought) proved to my self that around 1.5:1 was finite, (and, like I had previously posted I always kept them around 1.48:1 however over the last year I have since learned (and proved to myself) that it is omnipotent to build an engine as a complete system, rather than the old "erm, now try this pipe" approach of old.


This is why I stand behind my statement that "a crankcase is more than simply a place to store the air/fuel mixture until it is sucked up the transfers" (sorry Speedpro)

TZ350
24th July 2009, 09:03
This is why I consider that the EASIEST way to describe the Schnürle loop system is "keeping as much of the air/fuel mixture in the cylinder"

How it actually does that, (the separation of burnt gasses etc) is a little more complicated.

The BEST way to see this is by building a test rig as described by Gordon Jennings.

To actually see (and describe what you are seeing) makes a big difference to your understanding and comprehension of what aspects to pay attention to.


Interesting Post, Thanks

For anyone interested in making a flow rig described by Jennings. Page 122 http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner%27s%20Handbook.pdf

.

F5 Dave
24th July 2009, 10:47
Perhaps now your terminology 'short cct' is not what I would use.

The first gas entering the cylinder (esp in single transfer designs) bounces off the rear or head & escapes out the exhaust. I'd tend to call that escaping gas rather than short ccting.

Short ccting I'd say is the gas that come out of the front transfers and turns the corner hugging the cylinder between the trsf & the exhausts (hence short circuit). This tends to happen worst when the transfers are close to the exhaust. A modern setup often has a thin strip where a bridged port encroaches into the transfer clear area. (look at an RGV, RS or whatever).

Now if we consider that a crankcase as a pump, it is a pretty lousy one at low revs, worse with lower primary compression. Add to this the effect of the pipe scavenging being rev dependent; it is easy to imagine a bunch of gas short ccting when the pipe is out of tune and sucking at an out of freq range when the primary pressure is low.

I'd be surprised if the first gases would short cct as they would be spat out when the transfers open with most pressure so would be more likely to complete the loop (& then maybe escape).

But as the case pressure reduced, the velocity would reduce, making a short cct path the one of least resistance esp if the pipe was scavenging on 2nd order.

speedpro
24th July 2009, 19:35
It has to be a whole-of-system approach to be serious from the carb to the stinger and everything in-between. With that in mind I still consider, but have no proof, that a well designed system will see an amount of air/fuel delivered from the crankcase which will exceed the volume of the cylinder. The only place for the excess to go is out the exhaust port into the expansion chamber. With everything working sweet, after the transfers close the reflected wave will jam it back through the ex port into the cylinder increasing the VE of the engine. Therefore the flow of air/fuel into the pipe towards the end of the ex open period is deliberate as it increases the amount of air/fuel in the end that is trapped within the cylinder, once it is returned.

Interesting that SS90 is now acknowledging the place for lower primary compression.

B.Crump
24th July 2009, 19:47
Wow! Look at what you started!

Does that deserve a KB reward for 'Most inflammatory innocent question'?

yea man and its still going i was just hoping somone had done it as in a supercharger like what you find on a car as im having a go at building a supercharger out of a turbo got to gear it up somthing wicked

koba
24th July 2009, 19:55
yea man and its still going i was just hoping somone had done it as in a supercharger like what you find on a car as im having a go at building a supercharger out of a turbo got to gear it up somthing wicked

Cool, I had flirted with the idea of running omthing like this on a 100cc four stroke bucket but it didn't look worth it compared to traditional bucket engines.

SS90
24th July 2009, 20:44
Interesting that SS90 is now acknowledging the place for lower primary compression.

Hang on Speedpro!

Don't forget, very early on, I tried to point out that you have to establish what a certain engines original crankcase volume is before you say it must be lowered.

By that I mean, you may well find an exsisting engine is (for example) 1.3:1 and if you are (unwittingly) using a dated expansion chamber design/ port layout then you infact must INCREASE the primary compression ratio.

It's really important to establish what your original crankcase volume is.
Interestingly enough, I have noticed that the gains when reducing from (as an example) 1.65:1 to 1.48:1 are quite substatual, where as, reducing from 1.48: to 1.3:1 are less noticable, and the scavenge pattern and expansion chamber design needs to be VERY accurately designed to be advantageous.

I (surmise, no hard facts to back it up) that if someone did not have the resources to VERY accurately cut,bend and weld their chamber sections as well as design their scavenge patterns, then a primary compression ratio of 1.4:1 would be a "good compromise", as like F5dave said before, the crankcase will operate as a better (more efficient) pump, substituting losses in other areas.

This (in my opinion) is why "proffesionally" built engines (to essentailly the same specs) always seem to have "Just that little bit more" than other examples.

SS90
24th July 2009, 20:50
Perhaps now your terminology 'short cct' is not what I would use.

The first gas entering the cylinder (esp in single transfer designs) bounces off the rear or head & escapes out the exhaust. I'd tend to call that escaping gas rather than short ccting.

Short ccting I'd say is the gas that come out of the front transfers and turns the corner hugging the cylinder between the trsf & the exhausts (hence short circuit). This tends to happen worst when the transfers are close to the exhaust. A modern setup often has a thin strip where a bridged port encroaches into the transfer clear area. (look at an RGV, RS or whatever).

Now if we consider that a crankcase as a pump, it is a pretty lousy one at low revs, worse with lower primary compression. Add to this the effect of the pipe scavenging being rev dependent; it is easy to imagine a bunch of gas short ccting when the pipe is out of tune and sucking at an out of freq range when the primary pressure is low.

I'd be surprised if the first gases would short cct as they would be spat out when the transfers open with most pressure so would be more likely to complete the loop (& then maybe escape).

But as the case pressure reduced, the velocity would reduce, making a short cct path the one of least resistance esp if the pipe was scavenging on 2nd order.

Yes, as you are aware, this is one of the reasons why correct crankcase volumes are important.

In regards to "short circuiting", when looking at the "loop" system as a whole, I (and others) would consider any mixture that DID NOT become part of the Schnürle loop as "short circuited", although I would concede that it a broad term, particularly when you look at multiple transfer layouts.

But it is true that "The mixture that first enters the cylinder through the transfers is most likely to short circuit", and like I wrote above, the best scavenge patterns are ones that are better at reducing this.

I am of the opinion that "transfer kickers" are quite helpful in this area.

F5 Dave
24th July 2009, 21:33
The main point of the schnurle loop & more so collide stream porting is to delay the fresh gas in the cylinder. What I'd call short cct is probably truly wasted as it is escaping way too early & mixed with the exhaust gasses.

SS90
24th July 2009, 21:45
The main point of the schnurle loop & more so collide stream porting is to delay the fresh gas in the cylinder. What I'd call short cct is probably truly wasted as it is escaping way too early & mixed with the exhaust gasses.

Great! 5 pages and it can be summed up in one short paragraph.

(sigh)

speedpro
24th July 2009, 22:50
Hang on Speedpro!

. . . . you are (unwittingly) using a dated . . . . . .

It's really important to establish what your original crankcase volume is.
. . . . . .
and the scavenge pattern and expansion chamber design needs to be VERY accurately designed to be advantageous.

I (surmise, no hard facts to back it up) that if someone did not have the resources to VERY accurately cut,bend and weld their chamber sections as well as design their scavenge patterns, then a primary compression ratio of 1.4:1 would be a "good compromise", . . . . . .

This (in my opinion) is why "proffesionally" built engines (to essentailly the same specs) always seem to have "Just that little bit more" than other examples.

I don't do anything "unwittingly" on my engines.

I ended up paying Wobbly quite a few $$s to determine optimum engine configuration for the purpose, including measuring crankcase volume, porting and scavenge patterns, squish velocity, and coming up with the laser cut patterns for the pipe. He spent a weekend with new exhaust port software designing the ports. I'd already built the short stroke crank with the long rod as suggested by him. He kept checking what reed valves I could get and what size/type of carb as the layout evolved. About this time he did Nigel's engine. Theoretically mine should make a useful amount more than his. There is nothing dated, unwitting, inaccurate, or compromised about this engine. OK maybe dated, it was done a few years ago now.

SS90
25th July 2009, 04:33
I don't do anything "unwittingly" on my engines.

OK maybe dated, it was done a few years ago now.

Hmm, I doubt being only 2 years old it's "dated", I am sure it's "up to scratch"

With an (obviously) well designed crank, cases,cylinder,head,expansion chamber, why isn't it assembled and raced.... what is missing?

Buckets4Me
25th July 2009, 08:52
Hmm, I doubt being only 2 years old it's "dated", I am sure it's "up to scratch"

With an (obviously) well designed crank, cases,cylinder,head,expansion chamber, why isn't it assembled and raced.... what is missing?

here goes again :gob:

bucketracer
25th July 2009, 10:55
.

why isn't it assembled and raced.... what is missing?

A wise man knows that "DO THE FUCK WHAT YOU WANT HONEY" is not permission to do what we want. :yes:

.

speedpro
25th July 2009, 11:11
You got it. Luckily she-who-now-holds-the-pursestrings has no idea what that motor has cost. The bottom end is together and running with my old barrel on it. Post-blowup it needed a rebore and the old crank was not so good anymore(see avatar). In between getting all the bits more or less sorted there's been a supermarket and 3 or 4 other jobs, 2 house moves Akl-Wgtn-Akl, and all the usual stuff. Having said that I pressure checked the water cooled head last weekend and it has 2 pin holes, so I am making a little progress again. Plan is to get it going in the FZR chassis reasonably soon using the current cases.

B.Crump
26th July 2009, 21:21
Cool, I had flirted with the idea of running omthing like this on a 100cc four stroke bucket but it didn't look worth it compared to traditional bucket engines.


yea im gona try run it low at maby 5 or 7 psi i dont wana melt piston will do a thread on it when i get it going

does anyone know how much psi it can handle? i was told 7 was pushing it on a tf125

F5 Dave
26th July 2009, 21:30
I read about that twin hireabusa liner had the turbo cranked up to 32psi. I would start with that & work up. . . . Unless ya yella.

SP my 100 barrel has a few leaks, but was virtually destroyed by trying to fix them. I'm going to try running it as a temp barrel, but I'll mill some holes in the jacket to get to where it leaks & devon them from the water side & cover the hole up with a plate.

koba
27th July 2009, 07:17
yea im gona try run it low at maby 5 or 7 psi i dont wana melt piston will do a thread on it when i get it going

does anyone know how much psi it can handle? i was told 7 was pushing it on a tf125

Don't bother, its not worth the effort to make it work on a two stroke.
If you really want a fast go-kart put an old 400 or 2 stroke 250 in it.

B.Crump
1st August 2009, 15:13
not major power im after all tho i wont complane if i do im just doing it for fun to see what i can do. a 250cc will be to heavy as the motor is behind the seat it all ready nearly does wheel stands when you change gears .iv got a spair tf125 motor complete im gona do it to that one and see what hapens

bucketracer
15th May 2010, 16:32
………could this work? a 24mm carb feeding into a plenum chamber and the 34mm rotary valve inlet feeding directly from the chamber to the motor. That way the motor sucks full atmospheric pressure through a high flow 34mm bell-mouth and at WOT the restrictive 24mm carb can keep the plenum full.

TeeZee350’s very clever plenum chamber

Starts easy and idles http://www.youtube.com/watch?v=YxiEo8cgopg

A bit of a blurt up the drive http://www.youtube.com/watch?v=p4ef-WUO1Qs

Buckets4Me
15th May 2010, 16:49
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ta da!

Buckets4Me
7th June 2010, 09:02
still waiting to hear what the results of this experiment where

TZ350
8th June 2010, 20:21
.

Buckets4me pulling in his second win for the day and Chambers in third on the notoriously treacherous Mt Welly track when its wet.

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SS90
8th June 2010, 20:24
"B Grade", in the wet?

You must be proud.

Buckets4Me
8th June 2010, 20:35
"B Grade", in the wet?

You must be proud.

yep very. Show us a video of you winning will ya

thats unless you want to start a pissing match again lol

and dont forget that I'm a slow B grade rider and was running better than mid pack at Taupo :)
I am quite happy with the fact that I managed to stay upright that day (even with slicks in the A grade that day)

Buckets4Me
2nd September 2010, 09:48
217440 Thomas
217441 Tim
217442 My bike on the dyno 18.5 H/p at the rear (not bad for a 4 year old engine)

kel
14th September 2010, 21:55
18.5Hp :gob: My FXR puts out a meager 13.2Hp. I've always loved 2 strokes but when I saw the claimed figure of 20Hp for the FXR I thought 4 stroke technology (and extra displacement) had finally eclipsed the 2 stroke bucket so bought the thumper. Lesson learned, have just purchased a KE125 look forward to swaping ideas with you guys as mods develop

TZ350
14th September 2010, 22:45
........have just purchased a KE125 look forward to swaping ideas with you guys as mods develop

HP is not everything in Buckets, drivability and handling are pretty big ticket items too and FXR150's are hard to beat in the drivability and handling department.

I hear the hot setup for a KE125 is to fit a RG400 cylinder, 28mm carb and a good chamber.

F5 Dave
15th September 2010, 09:22
. . I hear the hot setup for a KE125 is to fit a RG400 cylinder, 28mm carb and a good chamber.

Yeah they don't just 'drop on' though.

kel
15th September 2010, 10:49
The Steadman mods from 2 decades ago, no doubt they are still very competitive bikes but there's better material to work with if going for the water cooled 100.
The KE125 wasn’t planned it was one of those bargains that you can’t pass up. TZ I'll be working to older motocross type power delivery so a fat power curve is the aim although I admit the peak power spread of the FXR will be near on impossible to match. My original bucket way back when was a KH100 ported to G31M-A (Centurion) spec, it had a good spread of power and was quick, figure the 125 can be that much better again.

jasonu
15th September 2010, 14:19
Yeah they don't just 'drop on' though.

Sure they do, I built mine on a Sunday afternoon in me garage with a file, a drill and some devcon...

F5 Dave
15th September 2010, 14:22
[insert Tui add];)

TZ350
15th September 2010, 19:29
Sure they do, I built mine on a Sunday afternoon in me garage with a file, a drill and some devcon...

We put ours together with devcon too, can't get the bastard apart again though........:Oops:

TZ350
15th September 2010, 19:48
The Steadman mods from 2 decades ago, no doubt they are still very competitive bikes but there's better material to work with if going for the water cooled 100.

Better material for a water cooled 100, I was going for a sleeved down RGV250 cylinder complete with power valves etc for mine. RGV250 or TZR were these what you had in mind?

Chambers is going the RG400 cylinder way, and we would be very interested in how the Steadman's went about it and how they moded the RG400 cylinders for their engines. We would love to know more about what Pete Sales did with his too, if anyone has any information on them.

jasonu
16th September 2010, 14:10
Better material for a water cooled 100, I was going for a sleeved down RGV250 cylinder complete with power valves etc for mine. RGV250 or TZR were these what you had in mind?

Chambers is going the RG400 cylinder way, and we would be very interested in how the Steadman's went about it and how they moded the RG400 cylinders for their engines. We would love to know more about what Pete Sales did with his too, if anyone has any information on them.

I purchased Ken Steadmans Rat motor, complete with a car (HQ Holden I think) heater coil for a radiator, a few (lot of) years back. The word agricultral comes to mind. However, it did show me it can be done.
Jimmys and Peters motors looked a lot nicer from the outside.
Anyone know what happened to Jimmys bike?

F5 Dave
16th September 2010, 16:00
Nothing 'happened' to it. It's where it's always been ready for him to pull it out & scare a few people. He's a bit scared of doing another collarbone & time is against him (in the sense of finding any) I think.

speedpro
16th September 2010, 20:27
Jim's bike is stored away all ready to go. Being a one-man farm sort of guy he can't afford to damage himself so even if he came out for a play he'd be a bit subdued. Though . . . . . if anyone can remember him riding at the Hamilton track round the polytech(?) he was taking it easy , and still sliding it up to the curb every lap on one corner. That old thing does handle good that's for sure though and the brakes are brilliant.

bucketracer
17th September 2010, 20:44
Some supercharged 50's and others, any guesses which one is supercharged with a Turbocharger............

There is also a supercharged and water cooled British 1936 2-stroke Scott and a supercharged air cooled 1937 DKW racer............

Now would water cooling on the British bike be a more advanced option for a supercharged 2-stroke?.................:)

Gigglebutton
22nd September 2011, 17:45
That is your Google search, internet based assessment …… the difference between the theory and experience is massive.

It’s pretty obvious no one knows it all and someone who won’t research things is bound to keep repeating his old mistakes.


If there are any factory workshop manuals for common modern road bikes of any era or even an exotic one that insists on a Torque Plate during rebuilding/reboring/reconditioning I would truly love to see a quality post about it complete with a PDF scan and/or a link or two.


No, .... a fretted imprint maybe and a very good example of what Bucket has been talking about.

247179 Click the picture to read the text.

SS90 this is the page you quote in your reference, and no doubt it’s the combined real life experience of a lot of people who work in the automotive industry who have analysed many engine failures and determined their cause.

Now tell me, does your page say melted appearance and misaligned (bent) rod as a possible cause just like Bucket has been saying, yes it does.

And do you see any reference to a jammed clip, nope you don't do you.

SS90 I too would like to know if there are any factory manuals that require torque plates and what is your take on that page you quoted, does it say melted appearance, possible misaligned rod and I can’t see where it says jammed clip, can you please point me to it.

bucketracer
1st October 2011, 11:40
That is your Google search, internet based assessment ....... Many is the spotty little kid that comes into a workshop, fresh from his education, that soon realises the difference between the theory and experience is massive.

What you say is true, although not very nice or smart.

I have spent a lot of time with dad in the workshop and I am smart enough to know my limits, so in my posts as well as writing about what I have learnt, I like to research and reference other people with real industry experience and something credible to say, if I get stuck TeeZee or Thomas are always able to point me in the right direction.

247698 247702 247700 247703 TeeZee's Suzuki GP125 Bucket.

I don't require people to believe me and figure that anyone who is inquiring enough to follow the links is also intelligent enough to make their own judgment.

Posts on the internet are like talk anywhere, some people are full of it, others have something worthwhile to say, and by now you should know from personal experience, people can usually figure it out.

koba
2nd October 2011, 12:06
people can usually figure it out.

Sadly it often takes a while, bullshitters generally get quite good at their craft through years of experience.

bucketracer
30th March 2012, 20:20
I have been looking through this old thread again.

crazy man
31st March 2012, 08:11
l might restart on my 2 stroke l started 15 years ago. tf100,water cooled , reed block, short stroked. may stick with the centre hub steering frame don't know yet

bucketracer
31st March 2012, 14:55
It would be very great to see the center hub out there, Buckets is getting a great mixture of bikes, definitely the most interesting RR class.

crazy man
31st March 2012, 15:31
It would be very great to see the center hub out there, Buckets is getting a great mixture of bikes, definitely the most interesting RR class.thats what a like about buckets even f3 was not to bad but rulzs keep changing and puts you of spending alot of time on building somthing that may not be alowed a year or two down the track

jasonu
31st March 2012, 15:47
l might restart on my 2 stroke l started 15 years ago. tf100,water cooled , reed block, short stroked. may stick with the centre hub steering frame don't know yet
Are you the guy from the south pole that ran a center hub steer in the early mid 90's?

crazy man
31st March 2012, 16:01
Are you the guy from the south pole that ran a center hub steer in the early mid 90's?l borrowed one in 2001 and raced it at the gp and is still in the shed lol started making 4 off them but well of finshing. not from the south pole. think this one was build in 1980

speedpro
31st March 2012, 19:07
think this one was build in 1980

In a farmhouse out the back of Ohakea by a bloke named Colin Wheeler. He was later "2 Wheels Engineering" in Palmy North I think. He cast the hub and other bits in a tin heated by a LPG burner of some sort. Very back yard Kiwi sort of thing.

crazy man
31st March 2012, 19:21
In a farmhouse out the back of Ohakea by a bloke named Colin Wheeler. He was later "2 Wheels Engineering" in Palmy North I think. He cast the hub and other bits in a tin heated by a LPG burner of some sort. Very back yard Kiwi sort of thing.l have a good wright up on it somewhere will post it when l find it

crazy man
31st March 2012, 19:54
here is the right up hope you can read it
261012261011

bucketracer
31st March 2012, 19:59
Geee, You havn't been following there have you?

I will write this REALLY SIMPLY.

The "factor" is simply a way of expressing this "counter weight" on the crank
compared to the weight of the piston rods assembly.

i.e the piston/rod assembly weighs this percentage of the crankwebs (counterweights)


Your mostly on the right track but your definition (understanding) of Balance Factor ""i.e the piston/rod assembly weighs this percentage of the crankwebs (counterweights)"" is wrong because you have the counter weight heavier than the reciprocating mass of the piston/rod assembly.

A small but very important difference.

Your definition of Balance Factor should have read, ""the crank webs (counterweights) weigh this percentage of the reciprocating mass of the piston/rod assembly"" as the counter weight is always lighter than the reciprocating mass of the piston/rod assembly.

A 60% Balance Factor means the counterweight weighs 60% of the reciprocating weight of the piston/rod assembly.

You can look it up on the web.

bucketracer
7th August 2012, 21:51
267822

Train Spotting .........

FastFred
8th August 2012, 07:52
Buckets4me pulling in his second win for the day and Chambers in third on the notoriously treacherous Mt Welly track when its wet.

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"B Grade", in the wet? You must be proud.

Anything in the wet at the very slippery Mt Wellington track is quite an achievement, Buckets4me should feel proud.