ESE's works engine tuner [Archive] - Page 29

Frits Overmars

29th March 2012, 22:38

Is this on a public forum(s)? I would be very interested to read more on your combined thoughts on STA's and blowdown if its accessible to an average joe wannabe tuner like me. Its an area that i sometimes feel hazy over, particularly the relationship between exhaust, blowdown and transfers for different applications, and dont want to ask stupid questions just yet so reading your discussions might help clarify a few things.Some of it is on a public forum: http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa . But most of it is not. And I am not even at liberty to reveal the forum's name, let alone publish members' contributions here. But what I can do, is show you some of my own contributions, rather randomly scraped together because A: I cannot spare the time, and B: that forum's search function (like any forum's that I know) is useless. Here goes:
---------------------------------------------------------------------
Time* area:
You start with a port in a cylinder. That port has a certain area.
Put that cylinder on a crankcase containing a crankshaft with a certain stroke and a certain conrod/stroke-ratio.
Turning the crankshaft will give a certain angle*area for the port in the cylinder. So you can say that a port in a cylinder on an engine has a certain angle*area.
Adding rpm will assign a certain time to that angle which gives us a time*area value. So a port in a cylinder on a running engine has a certain time*area.
And finally dividing that TA value by the cylinder capacity, including the combustion volume (which everybody keeps forgetting) will give the specific time*area, which is an indication of how well an engine can breathe and at what rpm it will run out of breath.
By the way, I like to use the multiplication sign * in angle*area and time*area because I feel it clarifies what these expressions stand for.

While we are on the subject of breathing: STA is essential but it is not the only factor. You can have all the STA you want; with a pressure ratio ≤ 1 over a port no mass will start moving in the desired direction.

The third essential factor is inertia. Even with ample STA and a healthy pressure ratio a stationary gas column needs time to get up to speed. The longer and heavier the column, the slower it gets moving.
(when talking about intake ducts you might argue that such a sluggish column will give a useful ramming effect later on, but I would say that this is just an attempt at the end to make up for something that went wrong at the beginning).
Summary: it all comes down to ports and pipes. But you already knew that.
-------------------------------------------------------------------------------
Gordon Jennings certainly did a lot of good with his easy-to-read articles. But he created one misconception that is festering until this day, with his translation of the SAE-papers of Yamaha's Naitoh and Nomura into 'tuner's english'.
He extracted specific time*areas and claimed them to be the optimum values for a two-stroke. On the scavenging side he was as right as makes no difference, but on the exhaust side it was quite another story.
Naitoh and Nomura just stated their findings; Jennings concluded that specific exhaust time*area should be what Yamaha had been using. But Yamaha had by no means found a gasdynamic optimum; they just had gone as far as the quality of their piston rings allowed them to do. And had they thought of using auxiliary exhaust ducts (first seen in their present form in the 1971 Jamathi engine), they would have made a quantum leap.
Another point of criticism is that Jennings emphasized exhaust time*area and almost neglected blowdown time*area.
----------------------------------------------------------------

husaberg

29th March 2012, 23:04

Some of it is on a public forum: http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa . But most of it is not. And I am not even at liberty to reveal the forum's name, let alone publish members' contributions here. But what I can do, is show you some of my own contributions, rather randomly scraped together because A: I cannot spare the time, and B: that forum's search function (like any forum's that I know) is useless. Here goes:
---------------------------------------------------------------------
Time* area:
You start with a port in a cylinder. That port has a certain area.
Put that cylinder on a crankcase containing a crankshaft with a certain stroke and a certain conrod/stroke-ratio.
Turning the crankshaft will give a certain angle*area for the port in the cylinder. So you can say that a port in a cylinder on an engine has a certain angle*area.
Adding rpm will assign a certain time to that angle which gives us a time*area value. So a port in a cylinder on a running engine has a certain time*area.
And finally dividing that TA value by the cylinder capacity, including the combustion volume (which everybody keeps forgetting) will give the specific time*area, which is an indication of how well an engine can breathe and at what rpm it will run out of breath.
By the way, I like to use the multiplication sign * in angle*area and time*area because I feel it clarifies what these expressions stand for.

While we are on the subject of breathing: STA is essential but it is not the only factor. You can have all the STA you want; with a pressure ratio ≤ 1 over a port no mass will start moving in the desired direction.

The third essential factor is inertia. Even with ample STA and a healthy pressure ratio a stationary gas column needs time to get up to speed. The longer and heavier the column, the slower it gets moving.
(when talking about intake ducts you might argue that such a sluggish column will give a useful ramming effect later on, but I would say that this is just an attempt at the end to make up for something that went wrong at the beginning).
Summary: it all comes down to ports and pipes. But you already knew that.
-------------------------------------------------------------------------------
Gordon Jennings certainly did a lot of good with his easy-to-read articles. But he created one misconception that is festering until this day, with his translation of the SAE-papers of Yamaha's Naitoh and Nomura into 'tuner's english'.
He extracted specific time*areas and claimed them to be the optimum values for a two-stroke. On the scavenging side he was as right as makes no difference, but on the exhaust side it was quite another story.
Naitoh and Nomura just stated their findings; Jennings concluded that specific exhaust time*area should be what Yamaha had been using. But Yamaha had by no means found a gasdynamic optimum; they just had gone as far as the quality of their piston rings allowed them to do. And had they thought of using auxiliary exhaust ducts (first seen in their present form in the 1971 Jamathi engine), they would have made a quantum leap.
Another point of criticism is that Jennings emphasized exhaust time*area and almost neglected blowdown time*area.
----------------------------------------------------------------

Thanks Frits

I was only just reading an article the other day and it mentioned the Jamathi winning the Italian Gp in about 69 so.
Jennings was easy to read and he did the reed opened by the pipe bit as well. Which most people seem to disagree with as well.But he did have an easy to follow style.
I do occasionally visit the other thread to see what has been added.

oh never picked up the "including the combustion volume" so thanks.

One last bit (I realise you are busy) is the crankcase volume most texts quote the peak speed at which the peak delivery ratio occurs as being inversely proportional to the square root of the crankcase volume (Ie higher revs need lower volume) yet seemingly the modern thinking doesn't follow this, is it about needing a certain reisivor volume available or just better duct flows and directional control nowdays?

oh yeah the virtual chocolate fish question answer was A BSA B25 Starfire I would also have accepted a Triumph 250 Tr25 Trophy. Or BSA 250 Goldstar SS.
Kickaha i am disappointed.

dinamik2t

29th March 2012, 23:36

Since the conversation came to old books, I would encourage anyone to give a look at Dixon's 2T book puplished in 2005.
I re-read random topics from time to time and have found lots of the stuff Frits or Wob (or even EngMod) "mention" here. It has lots of physics and formulas too, helping to better comprehend how each part functions.

It's rather cheap at an offer here, with free worldwide delivery : http://www.bookdepository.co.uk/High-performance-Two-stroke-Engine-John-Dixon/9781844250455

By the way, have you Frits or Wob read it, to share an opinion on it?

Frits Overmars

30th March 2012, 05:07

I would encourage anyone to give a look at Dixon's 2T book puplished in 2005......have you Frits or Wob read it, to share an opinion on it?I haven't.

Frits Overmars

30th March 2012, 05:17

...is the crankcase volume most texts quote the peak speed at which the peak delivery ratio occurs as being inversely proportional to the square root of the crankcase volume (Ie higher revs need lower volume) yet seemingly the modern thinking doesn't follow this, is it about needing a certain reisivor volume available or just better duct flows and directional control nowdays?Kinda hard to decipher that sentence. Are you sure you cannot write in Dutch, Husa? Anyways, square roots of volumes make me think of Helmholtz resonance. And if memory serves, I posted my 'Helmholtz blues' here not too long ago; you might want to take a look.
Nowadays an engine needs a large crankcase volume (the Aprilia RSA125's is 675 cc at TDC), all the port area you can cram into the cylinder circumference, good ducts for efficient flow and directional control, an exhaust that sucks and blows hard at the appropriate moments, and cooling, cooling, cooling.

Kickaha

30th March 2012, 05:33

Kinda hard to decipher that sentence. Are you sure you cannot write in Dutch, Husa? .
He can hardly write in English:shifty:

dinamik2t

30th March 2012, 06:02

husaberg

30th March 2012, 06:10

He can hardly write in English:shifty:
I can write dropped valves are great fun and ape hangers are only for Harley's. Can you? Warwick:Oops:

Kinda hard to decipher that sentence. Are you sure you cannot write in Dutch, Husa? Anyways, square roots of volumes make me think of Helmholtz resonance. And if memory serves, I posted my 'Helmholtz blues' here not too long ago; you might want to take a look.
Nowadays an engine needs a large crankcase volume (the Aprilia RSA125's is 675 cc at TDC), all the port area you can cram into the cylinder circumference, good ducts for efficient flow and directional control, an exhaust that sucks and blows hard at the appropriate moments, and cooling, cooling, cooling.

The peak speed at which the peak delivery ratio occurs as being inversely proportional to the square root of the crankcase volume (Ie higher revs need lower volume) It is nearly word for word from Robinson.
I think he was an Editor as well.:laugh:

What it was saying was the last bit (Ie higher revs need lower volume)
Out of respect for you and some others i tend to post in Engerishish.:msn-wink:

wobbly

30th March 2012, 08:34

I havnt read that book - so I just ordered it in case there is some small golden piece of info, you never know.

Re Blowdown STA numbers and the effect they have.
Firstly get out of your head completely the lawnmower engines view of the world that the piston dropping increases the pressure in the case, and it is this that forces the flow thru the transfers.
Mr Villiers creations may have operated this way - not any modern 2T.
When the transfers open, there is more pressure above the piston than there is case pressure in the transfer duct.
This gives rise to the alarming notion that when using staggered ports, the one to open first has so much backflow that it takes ages to recover, thus it has inflow last.
The area available in the Ex from the time the port cracks, down to where the transfers open, sets the amount of combustion pressure that is lost down the duct, and thus the amount of
positive pressure ratio across the open transfers ( and for how long this lasts ).
We can have NO FLOW until that positive pressure ratio is reduced to the point where we have more case pressure than cylinder pressure.
There are two ways to do this - lift the case pressure and or lower the cylinder pressure.
In a modern engine the case pressure is only rising very slowly due to the piston dropping, but what we do have is the pipe diffuser action, that started with the high pressure front ripping
out the opening Ex port - then entering the expanding pipes front section.
As the piston approaches BDC the Ex port is starting to suck the chrome off the proverbial towball,dropping the cylinder pressure ratio dramatically, and it is this that forces the bulk flow into the cylinder.
If the blowdown is set correctly for the power needed within the rpm band we want, then the recovery time from the unavoidable transfer backflow at the opening point, is such that we get the correct
amount of inflow to be trapped above the piston, thus creating the conditions for the correct amount of combustion pressure after the spark event.
It is this set of conditions - all revolving around the blowdown pressure,that ultimately creates how much combustion psi is developed - this creates torque, and it is this combined with rpm that creates POWER.

rgvbaz

30th March 2012, 08:44

260684

So, I had some free time and I tried to connect your discution on pressure waves with EngMod p.waveforms.
The above waves come from my test engine, at it's peak BMEP rpm.
In Honda RS, Yam TZ250 pre-loaded engines as well as the (~)RSA engine I have in EngMod, at the encircle point, TFR pressure is still above 1.

I added some letters to indicate points -me thought- of importance. Please correct me when I say something wrong in the following:

A: Ex port opens, flow starts there, pressure rises (why?). cylinder pressure starts dropping (still relatively too high). Tfr pressure irrelevant to Ex/Cyl pressure.
B: Ex pressure tops, flow speed tops. Cylinder pressure still dropping, gases exit. Tfr oscillate and starts rising, due to case/inlet pressure action.
C: Big depression in pipe, Ex pressure drops. Cylinder pressure drop dramaticaly, gases still exiting. Tfr open, pressure still rises.
D: Tfr pressure tops, start falling.
Blanks -lots of- follow.
E:
F:
G-K: Tfr pressure below 1. No flow?
K: Returning pulse from pipe arrives @ ex port, pressure starts rising. momentarily after, cylinder pressure starts rising. Tfr pressure rises a little more (flow?) before closing soon.
L: Ex pressure tops, a few degrees before closure. cylinder pressure rises, piston compressing hard. Tfr (closed) oscillation due to case/inlet action.
M: Ex pressure oscillation due to pipe action. cylinder pressure rises, piston truly compressing.
N:

Not much, but I have no head to combine every part's action into more analysis right know.:(

Hope I had a few right's above..
It would be very interesting to know what happens to TFR pressure and it falls at [C,F]. Also at [G,K] and their impact on flow.
(sorry, I ate a few letters after G - brains are pulverised as I said).

Have you ever read sae paper 2001-01-1853?

Its by Blair I think to sell virtual2T software. It looks at optimising a chainsaw engine using a tuned pipe. There is a good discussion on how to interperate the simulator output in there. Vanniks software can show most of the outputs he uses from the Virtual2T simulator. I found the part about left and right pressure exhaust waves very interesting (the left and right exhaust pressure waves combined give the superposition exhaust pressure; the pressure read by a pressure transduser - they themselves (left and right waves) cannot be measured (well appart from the single shot apperatus at QUB))

The exhaust pressure from your engmod screen shot is the superposition pressure. If you use Post2T you can look at the individual left and right waves and their influence on flow.

Dave.

kiwifruit

30th March 2012, 09:42

Far out, who knew bucket racing was so serious!

richban

30th March 2012, 11:10

Far out, who knew bucket racing was so serious!

Tis the pinnacle buddy.

jasonu

30th March 2012, 15:46

Far out, who knew bucket racing was so serious!

You're havin' a laugh right?

http://www.youtube.com/watch?v=1SK3y1a8TYs

kiwifruit

30th March 2012, 16:01

I like a laugh

husaberg

30th March 2012, 17:22

I like a laugh
Hence your er..."Love" of your bike in your avatar:buggerd:
The bike doesn't look so amused.Possibly because by the looks of it, your really only a 2 stroke guy .:shutup:.

Kickaha

30th March 2012, 18:10

Far out, who knew bucket racing was so serious!

It is the "Premier class" just look at the numbers on the track at Taupo compared to the poofters on Superbikes

kiwifruit

30th March 2012, 18:15

Yeah, it certainly is an exciting class! I look forward to taking part more.

bucketracer

30th March 2012, 20:08

There's been a bit of discussion about crankcase volume and compression. My view, as explained to me by Wobbly, is that the crankcase is just somewhere to store fuel and air before the transfers open and it is sucked out.

Nowadays an engine needs a large crankcase volume (the Aprilia RSA125's is 675 cc at TDC),

So its true, on a well developed race engine, the crankcase is less a pump than a place to store fuel and air before the transfers open and it is sucked out.

husaberg

30th March 2012, 20:18

So its true, on a well developed race engine, the crankcase is less a pump than a place to store fuel and air before the transfers open and it is sucked out.

I just read my origional post that Frits responded to and i see it had a rather crude spelling mistake that may have confused as it would not have translated so well to Dutch the French word "reservoir" pardon my engerish:Oops:This is a neat word to describe what bucket is saying above.

Does that make more sense Frits.
The bit i was quoting from Robinson was referring to when a engine was tuned to a higher rev range than it was original to maintain the original pumping efficiency you reduce the volume by an amount specified (inversely proportional to the square root of the original crankcase volume) to match the new higher rev range.
assuming say you don't want to modify the angles and shapes of the transfers or if you have say downsized or upsized an engine?

however Robinson does a couple of chapters later say
"bearing in mind at higher revs there is less time for the scavenge process to take place,
The choices are"

1)high stream velocity

:High crankcase compression
:Narrow port windows
:Late timing (Long blow down period)

2)Low(er) stream velocity

:earlier timing,larger ports
: Direction(s) of streams become critical.

So i guess he had a ball in both courts as it were. but the 2nd option is the modern approach?or slightly different again?

bucketracer

30th March 2012, 20:51

...before the local fools start replying ....

how about 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".

A 2-Stroke is not supercharged by its expansion chamber?

260774

From an EngMod2T simulation run. Does a "Delivery Ratio" (VE) > 1 indicate supercharging?

Frits Overmars

30th March 2012, 22:30

I just read my origional post that Frits responded to and i see it had a rather crude spelling mistake that may have confused as it would not have translated so well to Dutch....Does that make more sense Frits?It already made (some) sense the first time; as a former technical editor I am used to reading what people try to write instead of what they are actually writing.
And I do not translate anything to and from Dutch; In my mind I stick with the language that is being used.

The bit i was quoting from Robinson was referring to when a engine was tuned to a higher rev range than it was original to maintain the original pumping efficiency you reduce the volume by an amount specified (inversely proportional to the square root of the original crankcase volume) to match the new higher rev range.Crankcase pumping only serves to start the engine; once it is running in the power band you can forget all about pumping efficiency.

...high stream velocity >>> Narrow port windowsWhy don't we then close the port windows completely? That should give us infinite stream velocity, right? Yeah, right.... If you want velocity, you need a pressure differential. But we do not want velocity per sé; we want mass transportation (no, I'm not talking about public transport) so that means ample time.areas.

wobbly

31st March 2012, 09:16

Supercharging by definition is a method to increase the efficiency of an engine by using an external device that creates a higher delivery ratio,than that able to be achieved by the swept volume alone.
This can use energy within the Exhaust gas flow as is done by a Turbocharger.
It can use crank power to drive a pump, that creates more power at the crank than it consumes - a Supercharger.
Or - you can use sonic wave action in a divergent/convergent pipe,that uses that energy to evacuate and then refill the cylinder to a higher level than the swept volume alone could achieve - a Sonic Supercharger.
Next is Chemical Supercharging - where the fuel contains excess oxygen than that contained in the swept volume of air.

speedpro

31st March 2012, 09:17

Yeah, right....

You have Tui billboards over there?

dinamik2t

31st March 2012, 10:54

Thanks for pointing out the paper Dave (rgvbaz) - and Wob and Frits for the replies. I like papers -sae or others- but in my opinion knowledge acquired from such papers isn't cost efficient; at least for a student like myself. There are so many stuff I would like to read and multiplied by 23$ is a lot of money!
I am not saying researchers (hopefully part of the money goes to them) don't worth it, but unless you 're into it professionally (or be a banker's nephew) it's hard to spend all that $$.

I would prefer a more .. libraric system; get permission to study a paper eg for one hour for 2$. If you find it that usefull buy it now or another time.

F5 Dave

31st March 2012, 20:42

. . Firstly get out of your head completely the lawnmower engines view of the world that the piston dropping increases the pressure in the case, and it is this that forces the flow thru the transfers.
Mr Villiers creations may have operated this way - not any modern 2T.
. . . .

Meh, I'm pretty sure my GasGas Trials bike made in '00 works entirely like that. There is a parallel pipe from head to the first muffler section. ok it only puts out about 9hp, but it is surprisingly torquey (hehe I love using that word).

rgvbaz

31st March 2012, 20:43

[QUOTE=dinamik2t;1130292267]260684

G-K: Tfr pressure below 1. No flow?

QUOTE]

No, there will be flow because there is a diffential pressure between the transfer port and the cylinder, even though the transfer pressure is below a pressure ratio of 1. With the transfer pressure ratio being greater than the cylinder, the direction of flow will be into the cylinder.

See pic below. These are from Post2T in the thermo and gasdynamic traces in the plot options tab.

The Ptr (transfer) Pex (exhaust) and Pcyl (cylinder) pressures respectively and Mtr is the mass flow of gas at the transfer port 0 = no flow +ve number = flow into cylinder -ve number = flow back into the transfer port.

261019

Note. the mass flow doesn't reverse exactly when the cylinder pressure becomes greater than the transfer pressure, it is shortly after (I thinks this is to do with the left and right pressure waves)

Frits Overmars

31st March 2012, 22:40

I'm pretty sure my GasGas Trials bike made in '00 works entirely like that. There is a parallel pipe from head to the first muffler section. And I'm pretty sure the length and diameter of that parallel pipe were optimized to the millimeter.
Every duct in an engine plays a gasdynamics role, whether you want it or not, so you better make use of it.

Frits Overmars

31st March 2012, 22:49

.....the mass flow doesn't reverse exactly when the cylinder pressure becomes greater than the transfer pressure, it is shortly after (I thinks this is to do with the left and right pressure waves)I thinks you should think again, rgvbaz. Pressure differential does not equal flow; it equals acceleration. If there is a lot of inertia in the mass flow (a long gas column and / or a high flow velocity) a negative pressure differential will spend a lot of time slowing that flow down to zero before you will see the first sign of flow reversal.

rgvbaz

1st April 2012, 00:03

I thinks you should think again, rgvbaz. Pressure differential does not equal flow; it equals acceleration. If there is a lot of inertia in the mass flow (a long gas column and / or a high flow velocity) a negative pressure differential will spend a lot of time slowing that flow down to zero before you will see the first sign of flow reversal.

I guess I do need to thinks again then, Frits.:sweatdrop What you say makes perfect sence.

I had did have a quick look at the mass flow in the exhaust pipe at a couple of transducer points - it does seem that the sim calculates the mass flow from the differnce in the LH and RH wave, maybe it doesn't consider inertia?

TZ350

1st April 2012, 04:57

The big thing to come out of the last ten pages seems to be that insufficient blow down time area can lead to over heating by having excessive hot exhaust gas entering the transfer ports and over heating the engine.

… a single exhaust port there? I can hardly imagine the blowdown time.area will allow for more than 9000 rpm. That means: any more revs and the hot exhaust gases will blow down into the transfer ducts, heating up the cylinder quite effectively. If that is the case, not even water cooling would give you reliability.

EngMod2T is an excellent design tool. But I use a different approach: my sim calculates the blowdown STA that is required if you want to avoid any exhaust gas entering the transfers.You cannot keep an engine like that thermally sound if you allow any exhaust gas to heat up the cylinder, hence the different starting point in my STA calculations.
Granted, if the engine produces less power, you may get away with some blowdown into the transfer ducts. I merely tried to indicate that you can combat cooling problems by paying attention to the blowdown STA.

In a real engine the exhaust gas defines how much time.area it needs to leave the building. If the transfer ports open before the cylinder pressure has fallen below the scavenging pressure, the exhaust gas will regard those open transfers as yet another set of exhaust ports and it will enter the transfer ducts. That will steal some of the transfer time.area.
Then, when the cylinder pressure has dropped sufficiently, those exhaust gases have to be expelled from the transfer ducts; that steals some more transfer time.area before the real transfer of fresh charge can commence.
So when an engine revs too high for the available blowdown time.area, it is the remaining available transfer time.area that suffers doubly. That is also the reason that power drops rather steeply past its maximum.

The raw numbers as presented in the STA calculations take no account of possible backflow issues with insufficient blowdown.
One thing that cannot be quantified is how much the heating effect of the blowdown reverse flow is able to be dissipated by the cooling fins.Rob says it was fine at 28 Hp.
Only way to see if the engine is now on the limit is to thrash it do death on the dyno, emulating as far as possible the air flow regime with a fan, and see if the power fades dramatically.
A direct drive KT100 will fade 3 Hp in 18 after 4 pulls from 6,000 to 16,000 in 9 secs,change the pipe and loose a couple of that peak Hp and you can run all day with no fade at all, but still see the same 620C on the egt.

I was going to try and format all the separate rod and piston stuff onto one Excel sheet when i get some time and enthusiasm.

http://http://www.samarin.net/?productos
http://www.pvlsverige.se/vrm/index/index22.html
http://www.mxcomposites.com/con_rod.php
http://www.connectingrod.com.tw/ktm.htm
http://www.pro-x.com/downloads/Technical.pdf
http://www.kevinbreedonracing.co.uk/products_conrods.asp
http://www.connectingrod.com.tw/honda.htm
http://www.samarin.nl/webshop/index.php?act=viewCat&catId=32
http://www.tkrj.co.jp/
http://findebookee.com/c/connecting-rod the one is capt

On the original post Husa has now placed a spread sheet with rod dimensions.

Some of it is on a public forum: http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa .

… essential factor is inertia. Even with ample STA and a healthy pressure ratio a stationary gas column needs time to get up to speed. The longer and heavier the column, the slower it gets moving.
(when talking about intake ducts you might argue that such a sluggish column will give a useful ramming effect later on, but I would say that this is just an attempt at the end to make up for something that went wrong at the beginning).
-------------------------------------------------------------------------------
Gordon Jennings certainly did a lot of good with his easy-to-read articles. But he created one misconception that is festering until this day, with his translation of the SAE-papers of Yamaha's Naitoh and Nomura into 'tuner's english'.
He extracted specific time*areas and claimed them to be the optimum values for a two-stroke. On the scavenging side he was as right as makes no difference, but on the exhaust side it was quite another story.
Naitoh and Nomura just stated their findings; Jennings concluded that specific exhaust time*area should be what Yamaha had been using. But Yamaha had by no means found a gasdynamic optimum; they just had gone as far as the quality of their piston rings allowed them to do. And had they thought of using auxiliary exhaust ducts (first seen in their present form in the 1971 Jamathi engine), they would have made a quantum leap.
Another point of criticism is that Jennings emphasized exhaust time*area and almost neglected blowdown time*area.
----------------------------------------------------------------

Nowadays an engine needs a large crankcase volume (the Aprilia RSA125's is 675 cc at TDC), all the port area you can cram into the cylinder circumference, good ducts for efficient flow and directional control, an exhaust that sucks and blows hard at the appropriate moments, and cooling, cooling, cooling.

Re Blowdown STA numbers and the effect they have.
Firstly get out of your head completely the lawn mower engines view of the world that the piston dropping increases the pressure in the case, and it is this that forces the flow thru the transfers.
Mr Villiers creations may have operated this way - not any modern 2T.
When the transfers open, there is more pressure above the piston than there is case pressure in the transfer duct.
This gives rise to the alarming notion that when using staggered ports, the one to open first has so much backflow that it takes ages to recover, thus it has inflow last.
The area available in the Ex from the time the port cracks, down to where the transfers open, sets the amount of combustion pressure that is lost down the duct, and thus the amount of
positive pressure ratio across the open transfers ( and for how long this lasts ).
We can have NO FLOW until that positive pressure ratio is reduced to the point where we have more case pressure than cylinder pressure.
There are two ways to do this - lift the case pressure and or lower the cylinder pressure.
In a modern engine the case pressure is only rising very slowly due to the piston dropping, but what we do have is the pipe diffuser action, that started with the high pressure front ripping
out the opening Ex port - then entering the expanding pipes front section.
As the piston approaches BDC the Ex port is starting to suck the chrome off the proverbial towball,dropping the cylinder pressure ratio dramatically, and it is this that forces the bulk flow into the cylinder.
If the blowdown is set correctly for the power needed within the rpm band we want, then the recovery time from the unavoidable transfer backflow at the opening point, is such that we get the correct
amount of inflow to be trapped above the piston, thus creating the conditions for the correct amount of combustion pressure after the spark event.
It is this set of conditions - all revolving around the blowdown pressure, that ultimately creates how much combustion psi is developed - this creates torque, and it is this combined with rpm that creates POWER.

Crankcase pumping only serves to start the engine; once it is running in the power band you can forget all about pumping efficiency.

Supercharging by definition is a method to increase the efficiency of an engine by using an external device that creates a higher delivery ratio, than that able to be achieved by the swept volume alone.
This can use energy within the Exhaust gas flow as is done by a Turbocharger.
It can use crank power to drive a pump, that creates more power at the crank than it consumes - a Supercharger.
Or - you can use sonic wave action in a divergent/convergent pipe, that uses that energy to evacuate and then refill the cylinder to a higher level than the swept volume alone could achieve - a Sonic Supercharger.
Next is Chemical Supercharging - where the fuel contains excess oxygen than that contained in the swept volume of air.

There are other link/post collections on most other decade pages ......

husaberg

1st April 2012, 06:40

Nowadays an engine needs a large crankcase volume (the Aprilia RSA125's is 675 cc at TDC), all the port area you can cram into the cylinder circumference, good ducts for efficient flow and directional control, an exhaust that sucks and blows hard at the appropriate moments, and cooling, cooling, cooling.

I kind of like this one the best.:soon:

I found the Helmoltz Blues on the pitlane thread and yes the search function was not that great. The KB one is pretty good as long as the keywords are carefully chosen.

This was posted by Kel a fair ways back.Its off the Pitlane thread.

Frits Overmars
Sujet: Re: [GP125] Caractéristiques Aprilia RSA Mer 8 Déc - 13:36
In theory enclosed cranks are good. Jan Thiel did some experiments at Aprilia with a kart engine that had its reed valve at the front: the incoming mixture had to move against the direction of crank rotation. And although the crankcase stretched over the crank webs, reversing the direction of rotation brought another HP. So the crankshaft does have an influence.
But in practice, if you reduce the distances between crankshaft and crankcase walls to less than 1 mm, the viscous friction of the mixture between the surfaces really costs power at high rpm. And if you make the clearances so tight that lubricating oil can no longer reach the big-end and crankshaft bearings, it will also cost engines
Another negative aspect: any volume with a narrow 'entrance' between the crankshaft and crankcase surfaces acts as an hydraulic damper on the Helmholtz-resonance in the crankcase.
Aprilia has avoided this by making the space between the crank webs as wide as the big-end bearing. As a result the crankcase volume of the 125 cc RSA engine at TDC is about 650 cc, so the exhaust pipe really has some volume to breathe from.
So much for the fairy tale of high crankcase compression

Ps twice now you have referred to this and the pitlane forums as being open public.
Does that mean there is a invitation only 2 stroke tuners thread?

wobbly

1st April 2012, 09:33

You are right about the Gas Gas engine spec.That sport has a whole different dialogue of its own to describe the performance of the torque curve needed to jump rocks in a single bound.
The grunt ( small amount not withstanding ) has to be rising and falling at exactly the right time to give amazing control of the rear tyres force on the ground.

Frits Overmars

1st April 2012, 11:23

...twice now you have referred to this and the pitlane forums as being open public. Does that mean there is a invitation only 2 stroke tuners thread?You must have a long-time memory like a goldfish, Husa. Two days ago I wrote:
"Some of it is on a public forum: www.pit-lane.biz/t117p246-gp1...es-aprilia-rsa (http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa) . But most of it is not. And I am not even at liberty to reveal the forum's name".

EDIT: On second thought that may have come out a bit harsh. I did not want to insult either you or the goldfish.

jasonu

1st April 2012, 11:37

You must have a long-time memory like a goldfish, Husa. Two days ago I wrote:
"Some of it is on a public forum: http://www.pit-lane.biz/t117p246-gp1...es-aprilia-rsa (http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa) . But most of it is not. And I am not even at liberty to reveal the forum's name".

EDIT: On second thought that may have come out a bit harsh. I did not intend to insult either you or the goldfish.

Are they chocolate goldfish? I know Husa has a fettish for those...

Grumph

1st April 2012, 12:20

You must have a long-time memory like a goldfish, Husa. Two days ago I wrote:
"Some of it is on a public forum..... But most of it is not. And I am not even at liberty to reveal the forum's name".

EDIT: On second thought that may have come out a bit harsh. I did not want to insult either you or the goldfish.

He lives on the wet west coast Frits - so besides having webbed feet, he can probably breathe underwater too...

Hmm - a secret think tank of two stroke tuners....did they do the study on the long term memory of goldfish ?

husaberg

1st April 2012, 16:21

You must have a long-time memory like a goldfish, Husa. Two days ago I wrote:
"Some of it is on a public forum: www.pit-lane.biz/t117p246-gp1...es-aprilia-rsa (http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa) . But most of it is not. And I am not even at liberty to reveal the forum's name".

EDIT: On second thought that may have come out a bit harsh. I did not want to insult either you or the goldfish.

And who say's the Dutch have no sense of humor?
Ouch my goldfish is indeed a little miffed by the comparison as well, indeed he has crossed you off his Christmas card list .

The first time was this below er 6 months ago at first i thought it was just rhetoric but then your second time? 2 days ago.

I agree with Wobbly (I usually do): there is no money in paper books on two-stroke technology (there is little money in paper books period, unless you happen to write Harry Potter stories). But you'll find a lot of present-day info in forums.
ESE's works engine tuner is a good example, and of the numerous other forums that are 'open to the public' I would recommend www.pit-lane.biz (http://www.pit-lane.biz). It's French-based, but yours truly and Jan Thiel are allowed to write in English (and I post all my photos in Dutch without anyone noticing:shifty:).
A good starting point would be here: http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa.

Reading through the above posts my eye fell on this remark from Wobbly, talking about reeds versus disks:
First of all, thanks for the flowers, Wob (like I just said, I usually agree with mr. Wright:whistle:).
Second: it should read Jan and Frits, not the other way round; Jan did much more than my humble self in making the two-stroke so suppreme that it had to be put down by the Honda-Dorna combination.
Third: I would not say that a Honda reed valve engine kicked Aprilias arse. The Aprilia riders did that all by themselves, stealing points from each other and shooting each other off. Not even Honda-driver Hiroshi Aoyama would dispute that the Aprilias were faster.

now i may have a Carp like memory, but i do remember this.

You are right, Husaberg.
O, and one more thing, TZ350. Fritz is German. I am a Dutchie and I spell my first name with an s :shifty:.

He lives on the wet west coast Frits - so besides having webbed feet, he can probably breathe underwater too...

He also doesn't need irrigate either, goes to the lakes or rivers and Tasman sea often and enjoys watching, while his grass grows all year around without any snow on the ground or nor wester's and the ground has been virtually vibration free for 30 odd years.
He also may get paid a wet weather allowance as well, yet not have to work in the rain .:bleh:
he also lives surrounded by a lush subtropical rainforest that millions of people come here especially to see this unique beautiful scenery every year.
The world class hunting fishing and outdoor recreation all make living on the west coast so frustrating. as well not to mention the overcrowding issues with my closest neighbor a 5 minute walk away.
So yeah us coasters sure are odd creatures:innocent:

Grumph

1st April 2012, 19:12

So yeah us coasters sure are odd creatures:innocent:

Hey, i was nice and didn't mention the extra toes so prevalent amongst coasters...

The West Coast is only temporary anyway - when the alpine fault goes, so does that coastline.

husaberg

1st April 2012, 19:24

Hey, i was nice and didn't mention the extra toes so prevalent amongst coasters...

The West Coast is only temporary anyway - when the alpine fault goes, so does that coastline.

You mean that alpine fault that was created in the southern alps the mountain range that divides the West Coast from the East coast.One of the many faults that run of the two plate boundaries.
Oh those Alpine faults that are equally dispersed between Me and er...... You.
Also is that a volcano beside you there.:msn-wink:

PS that extra toe is bloody handy, I understand it's almost like having an opposable thumb:niceone:

TZ350

1st April 2012, 20:21

Do I see a single exhaust port there? I can hardly imagine the blowdown time.area will allow for more than 9000 rpm. That means: any more revs and the hot exhaust gases will blow down into the transfer ducts, heating up the cylinder quite effectively. If that is the case, not even water cooling would give you reliability.

I can hardly imagine the blowdown time.area will allow for more than 9000 rpm. That means: any more revs and the hot exhaust gases will blow down into the transfer ducts".

My sim calculates the blowdown STA that is required if you want to avoid any exhaust gas entering the transfers.

Your screenshot shows a BMEP of 11.4 bar @ 12,500 rpm. That is, like you say, achievable and believable. The Aprilia RSA also develops its maximum BMEP at about 12,500 rpm, but its value is almost 50% higher.

You cannot keep an engine like that thermally sound if you allow any exhaust gas to heat up the cylinder, hence the different starting point in my STA calculations.

Granted, if the engine produces less power, you may get away with some blowdown into the transfer ducts. I merely tried to indicate that you can combat cooling problems by paying attention to the blowdown STA.

In a real engine the exhaust gas defines how much time.area it needs to leave the building. If the transfer ports open before the cylinder pressure has fallen below the scavenging pressure, the exhaust gas will regard those open transfers as yet another set of exhaust ports and it will enter the transfer ducts. That will steal some of the transfer time.area.

Then, when the cylinder pressure has dropped sufficiently, those exhaust gases have to be expelled from the transfer ducts; that steals some more transfer time.area before the real transfer of fresh charge can commence.

So when an engine revs too high for the available blowdown time.area, it is the remaining available transfer time.area that suffers doubly. That is also the reason that power drops rather steeply past its maximum.

This is very interesting as you can see the steep drop off in the 31hp graph, and at Taupo after looking at the speed trap times and gearing, the bike was running at 13,000rpm up the back and for a good part of the front straight, well in the exhaust gas down the transfers region.

261086

The engine did not seize on full throttle running flat out, but after several down changes, when the throttle had been closed for a bit, maybe the cooling was marginal and when the cooling from the MJ fuel stoped, the engine stoped.

So what to do? an alloy sleeve with large tripple ports, not for power but for better thermal reliability ... :scratch:

F5 Dave

1st April 2012, 20:52

Time to add that injector for closed throttle application. Only problem is it still needs to be fed from the same 24mm aperture.

husaberg

1st April 2012, 21:02

Time to add that injector for closed throttle application. Only problem is it still needs to be fed from the same 24mm aperture.

24-2-4 Engines must be derived from non-competition motorcycles. Motocross, Road Racing,
Enduro and Go Kart motors and transmission parts are not permitted. There shall be no
restriction on the make, type or design of carburettor, ignition, exhaust, piston, cam, valve
springs or cooling system except for class eligibility. All engines must be normally
aspirated except F4 4 stroke engines of less than 100cc capacity, which may be turbo or
supercharged.
F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm
carburettor, F5 4 stroke engines over 53cc are restricted to carburation equivalent to a
single 20mm carburettor.

I have said to TZ for a while that i think not all the air has to flow through the carb. So not sure the rules define this.
It says the carb must be eq to a 24mm. Not that all the air has to go actually through it.

But anyway it has been written that one dodge to lower the risk of ring jamming that may be either thermal or as a result of piston rock is to machine the lands a tiny amount 0.02-0.04mm was mentioned. Yes the amount is tiny and the pistons are not round but i believe it can be effective.

Ocean1

1st April 2012, 21:07

It says the carb must be eq to a 24mm. Not that all the air has to go actually through it.

Wouldn't be the first to develop a persistent and strangely consistent vacuum leak.

Frits Overmars

1st April 2012, 21:36

The engine did not seize on full throttle running flat out, but after several down changes, when the throttle had been closed for a bit, maybe the cooling was marginal and when the cooling from the MJ fuel stoped, the engine stoped.Then don't close the throttle :D.
The old 100 cc kart engines with direct drive were notorious in that respect. They were air-cooled, iron-sleeved and they revved over 20,000 rpm. When you cut the power at those revs, chances were that the con rod would quit; it needed the help of the compression pressure to stop the piston from going through the roof. So you had to brake first and then cut the power.
Common practice was to put a hand against the carb bellmouth and blip the throttle occasionally during braking to get some fuel through the engine. But more than one rider forgot how close the chain was to the carb, and had to remove his right glove with a finger tip still in it...
My solution was to fit a brake light switch to the brake pedal and connect it to the ignition cut-out wire. Then you could keep both hands at the wheel, saving your fingers, and keep the throttle wide open during braking. I would not advise you to copy this 100%, but think about mounting a kill switch and using it....

.....what to do? an alloy sleeve with large tripple ports, not for power but for better thermal reliability ..And if the triple ports would raise the power by coincidence, you wouldn't object too loudly, would you?
But sleeve and thermal reliability are another set of words I would not use in the same sentence. OK, an alloy sleeve is better than a cast iron one, but there will always be a thermal barrier between sleeve and cylinder body. Even with the best shrink fit, oil will creep between the sleeve and the cylinder; that oil will char, and gone is your heat path.
Believe me, I know; you cannot come up with a single mistake I haven't already made decades ago (there is a fancy word for it: experience).
All in all, I guess the triple ports may outweigh the disadvantages of the sleeve. But couldn't you make the ports without using a sleeve?

bucketracer

1st April 2012, 22:09

couldn't you make the ports without using a sleeve?

TeeZee has hand sculptured a set of auxiliary exhaust ports into a cylinder, but with an offset exhaust the effort makes it difficult (impractical) to replicate in any qty, I hear Speedpro has suggested a different approach to him for getting more blow down STA.

Below is TeeZees triple port which will get a proper tryout with Wobs pipe on the dyno after the Easter meet at Kaitoke, the plenum might get a run too. The plastic sleeves are mock-ups made by Chambers, note the modified verniers he uses for measuring the port heights.

husaberg

1st April 2012, 23:06

Then don't close the throttle :D.
The old 100 cc kart engines with direct drive were notorious in that respect. They were air-cooled, iron-sleeved and they revved over 20,000 rpm. When you cut the power at those revs, chances were that the con rod would quit; it needed the help of the compression pressure to stop the piston from going through the roof. So you had to brake first and then cut the power.
Common practice was to put a hand against the carb bellmouth and blip the throttle occasionally during braking to get some fuel through the engine. But more than one rider forgot how close the chain was to the carb, and had to remove his right glove with a finger tip still in it...
My solution was to fit a brake light switch to the brake pedal and connect it to the ignition cut-out wire. Then you could keep both hands at the wheel, saving your fingers, and keep the throttle wide open during braking. I would not advise you to copy this 100%, but think about mounting a kill switch and using it...

I guess that was not with pumper pulse carbs because they would still pump gas on overun. no air though or not enough anyway.
I believe this was the major problem Cagiva had, as the fuel injectors would still pump gas into the cylinders on overrun. when the throttle was opened nothing would happen (BOG City) then it would fire up suddenly again, once the build up of fuel was expelled. High-sides anyone.
As i have said before, i once rode a pumper carbed MB100 that did exactly the same thing.

You GP125 already has the capacity to pump fuel using the pumper set up, has an ignitech, you can rig up a TPS. Wobs shown how to do the truth table. So a wee play and Bobs you mothers Brother. Fuel on over run when the throttle is closed and only when the revs are high. Shit you could probably go it gravity with a solenoid fuel control as long as it was post slide? Not as simple as the Frits solution though.

TZ wasn't there a plan a long time ago tho adapt a RGV cylinder.
If you were to use one of those you could have liquid cooling.
In fact if you went with a late model VJ23 wob suggested you could have auxillary ports and a wide ex port and liquid cooling and a power Valve.
but yes only 100cc but you could then run any carb you would like. Yes the stroke will need a bit of work as well.
Failing that you could always put a NSR250 cylinder one top of that Suzuki Honda made GP bikes to you know they went ok as well. So i am told.

Have just found out that the Suzuki VJ23 cylinder is a T port ( like the older models and also Aprilia RS250) but it has sub ports as well.
This may be an even better choice for sitting on a RG bottom end and sleeving to 50mm.
Anyone got one I can look at.

Posted the Cagiva stuff before but i don't care it suits my POV

jasonu

2nd April 2012, 03:59

So what to do? an alloy sleeve with large tripple ports, not for power but for better thermal reliability ... :scratch:

No, build a water cooled 100cc motor equiped with ANY size carb you want.

Yow Ling

2nd April 2012, 06:05

with your ignitech could you run 2 maps, both identical but one having a revlimit of say 4k, when you brake it changes maps.would sure get you off the brakes on fast corners. You can get cast iron liners nikasiled. Rg150s inject oil into the barrel just beneath the exhaust port and RH main bearing only , petrol goes in raw, not affected by throttle position except in the pump

twotempi

2nd April 2012, 09:07

Grumph

2nd April 2012, 17:31

There is a silicon paste which is used for thermal conductivity with alloy heat-sinks on electronic circuit-boards.

This may have an application between sleeves and the outer cylinder muff during assembly.

I don't think it is petrol soluble either.

Just a thought.

I've used something very similar seating heating elements into dies...given enough heat cycles it turns to dust. Maintenance on the dies consisted of redoing the paste application regularly.

husaberg

2nd April 2012, 21:13

Ian Cramps 500 twin as i have said before the inlets were ugly but he was trying to fit it in a tz250 frame so the exhaust under the seat would not work.
i always did like the overlapping cranks though. As well as the 3 part crankcase which were clever.

This is his Website a few interesting bits and pieces http://www.iancramp.co.uk/journalism.html

2T Institute

3rd April 2012, 01:29

Anything ever come of it?

Frits Overmars

3rd April 2012, 04:34

And now for something completely different: the glorious new Moto3 Grand Prix class that will make us all forget those damn two-strokes.
I proudly present the Honda Moto3 price list: http://www.fim-live.com/fileadmin/alfresco/Honda_Moto3_Engine_Part_list_MR03GP_version_1.pdf
The above document shows the prices for the standard parts. Honda kit parts tend to be 'a bit' more expensive. But let's stick with the standard prices for now.
A standard piston sells for 1644.60 Euro; today that's NZ $ 2660 (and Honda will make you wait 4 months for the privilege).
And did you notice the price of a piston pin? 342.90 Euro ($ 555). Now who said Honda has no sense of humour? :killingme

F5 Dave

3rd April 2012, 10:12

HUmina humina!

Well that's brought the prices down for the punter. I hear these 2 strokes were getting too expensive.

Oh well, the engine parts should last a long time being a 4 stroke:pinch:.

husaberg

3rd April 2012, 16:44

Anything ever come of it?

Missing a few installments but yes. It was finished in time for the rule change that effectively made it ineligible for most of it potential customers:shutup:
http://www.iancramp.co.uk/Images/Crankcase.png

LionHearthttp://www.iancramp.co.uk/design%20&%20development.html
A project undertaken in Japan was the design of a twin-cylinder 2-stroke 500GP engine (the “LionHeart”), the crankcases for which are modelled here by the sponsor’s PA. Completion of the engine unfortunately coincided with the Japanese decision to abandon a national 500cc class and go to Superbike rules instead.
I think this may be installment 4.
I have a few more but missing the last one i had when he went of to Japan to work and finished the engine there.
There is some information a a couple of pictures about it on his website but not much.

Those of you familiar with the Britten V twin will realise the team had a far easier method of constructing the patterns;)

http://www.iancramp.co.uk/Word%20Docs/WRITER'S%20CRAMP/GP%20Engine%20layout.docIf you want small and light, the V2 is the way to go. Or is it? Something which I hadn’t realized until I started designing the Lionheart is that having a narrow engine doesn’t do you any good once you get below a certain width, because the rider’s knees are going to be wider anyway. Even the lankiest rider, with his legs clamped tightly together, is going to measure more than 350mm across the knee area by the time you’ve allowed for a few layers of leather, some padding, and knee-sliders. So why make the engine any slimmer than that? Also, in the racing crouch position, the rider’s elbows will be in front of his knees, and you can’t get your elbows any closer together than your ribs. The width across the elbows will be pretty much the same as the shoulder width, which is quite large these days because of all the body-armour carried in that area.

http://www.iancramp.co.uk/Word%20Docs/WRITER'S%20CRAMP/honda_design.docWhen did Honda start designing their twin-crank 250 engine to replace the double-throw single crank one in their GP bikes? Well, it was just about the time that the first drawings of the LionHeart (with its twin cranks) were printed in FB. Ironic, really, when you consider how dog-slow the 98 works Honda engines were, but I did warn them - I wrote that LionHeart would have been a double-throw crank if I could have afforded it, but it was much easier (ie cheaper) to make two single cranks rather than one double. .......The more I looked into this, the more the deja-vus were hitting me. I am the longest-serving FB scribbler (for my sins), and anoraks out there who keep every issue of the comic going back to the year dot will be able to find a photo of me racing my highly modified, fuel-injected Honda RS125 long before Shinichi Ito was first seen testing the fuel-injected works HRC bike (and before the V-Due was ever thought of). Indeed, I think that I was the first person to race a two-stroke bike with electronic fuel injection ever, and while I admit that it needed a bit of sorting, it was certainly a lot better than the V-Due and could have been better still had I not been limited to spending about 0,1% of the time & money that factories have to sling around.

The other top secret HRC works trick of this time was water injection into the exhaust pipe. This, I admit, wasn’t on my RS125 - but only because I had abandoned it ten years before after a few races with it fitted to the Villiers 210 engine on my kart. I found that this type of injection (designed to increase the width of the power band) worked well on the dyno, where I used water piped from a cistern in the lavatory next door, but on the track I had to carry such a big water tank to make it work that the gains were not worth the weight penalty. HRC also abandoned this system after a couple of races, for pretty much the same reason.........but where did they get the original idea? Could it be that we are entering, not so much the twilight zone, but.........the toilet zone?

wobbly

4th April 2012, 08:06

Before anyone gets all excited, remember that the pipe layout I did was for the single Ex port engine with very high duration needed to get the Blowdown correct.
That pipe wont work with the tripple port cylinder as the timings are way lower duration.

dinamik2t

4th April 2012, 10:30

Wob, now that you mentioned how pipes don't work with different specs..
Is there any way of doing reverse engineering to a pipe design, to acquire the few basic parameters it was built with?
Say, you have a full pipe design with lengths and angles. Eg, tuned length can point out ex duration-maxHP rpm combos?

By the way, I noticed that sometimes -for the particular example of ExDur-MaxHP rpm- even if I rise or lower the timing, max power rpm will stay the same, +-100 rpm. Obviously, not half a degree alterations, but from 190 to 198.
I guess those might be, deliberately made, 'desigh mistakes' in mass production tuned pipes, to accomodate possible tuning alterations?

wobbly

4th April 2012, 11:17

The less clever a pipe design is, its much harder to pin down what the designers intent was, and the less it will be "port specific ".
But with say the 125 Bucket pipe, it was designed right from the get go to run with a 78* Ex port, and will only work correctly with the proper area step at the flange etc as it has
a two stage header and all manner of trickery to try and maintain the spread as well as create good peak numbers.

But there are all sorts of generalities that work, like 200* with 950 will peak at around 10500 with anything from a TZ350 to a Banshee Cheetah.
The RS125 with 196 and 830 will peak around 12000,then the A Kit with 200 and 800 will peak around 12500 but rev hard to 14,000.
But one thing that is a real fly in the ointment is the ignition - the peak prm point and the overev capability of a port timing/pipe length combination is hugely influenced by the timing - and how much of the available heat
energy in the fuel is dumped into the pipe, or the head/piston/water.
Best example is the Italian 125 ICC engines with fixed timing around 14*, these need a pipe some 40mm shorter than the A kit Honda to get revs near 14,000 with identical Ex timing.
The Honda has a digital ignition with a ton of retard and a solenoid powerjet, the ICC has none of this so needs a completely different approach - no free lunch.

husaberg

4th April 2012, 19:26

Like i said missing some installments there should be one or 2 where he gets the cases ready for casting then this lot of two.

TZ350

4th April 2012, 21:47

Dan's take on Cylinders and Pistons http://www.dansmc.com/pistons.htm

261406261407

Dykes Ring

A very good read about piston rings:- http://americanmusclecarsaustralia.com/forum/viewthread.php?tid=2627

husaberg

4th April 2012, 23:45

I was looking at a picture of a NSR and had a thought it looks real large on the ignition side to accommodate the electric start.

http://cdn.bikechatforums.com/files/_bwm_z3qbgk___kgrhgookkiejllmvuycbkyo0_ictg___12.j pghttp://3.bp.blogspot.com/_kJOOykmUBK0/SpcUxh7XNRI/AAAAAAAAAM8/tsvRAQPNW28/s320/100_1067.JPGhttp://2.bp.blogspot.com/_kJOOykmUBK0/SpcUyuB-23I/AAAAAAAAANU/vy0hcOHaBbc/s320/100_1070.JPGhttp://i.ebayimg.com/00/s/MTAyNFg3Njg=/$(KGrHqR,!iQE7DUNlNEwBOz6Hm5m!Q~~60_12.JPGhttp://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=254216&d=1325450926http://img.auctiva.com/imgdata/1/4/5/4/6/0/8/webimg/528143367_o.jpg
So how much more power would it develop with disk valve induction instead of Crankcase reed ho much more is in it if it were say 35 with the reeds.
it would be interesting to have a 6 speed liquid cooled power valved Honda. kind of like this one.
http://www.pvlsverige.se/vrm/verkstad/Honda3.jpghttp://www.pvlsverige.se/vrm/verkstad/Honda1.jpg

Yes it would be good to pull me finger out me bum and stop procrastinating but just wondering.
Those aprillia's seemed to go ok

2T Institute

5th April 2012, 02:48

Husa interesting engine that disc Honda where is that from?

Frits Overmars

5th April 2012, 02:59

I was looking at a picture of a NSR....I suspect this cylinder and head were never meant to be fitted to that engine. Where did you find them? Some 250 cc V-twin?
The head could do with an additional bleed connection. As it is, most of the head and even a part of the cylinder are air bubble cooled...

husaberg

5th April 2012, 07:00

Husa interesting engine that disc Honda where is that from?

http://www.pvlsverige.se/vrm/index/index22.html
look for the pic with the man with spanners in the menu.
Roffe built it amongst others must be long long winters in Sweden.
http://50iniepoca.forumfree.it/?t=43987929&st=75

http://img246.imageshack.us/img246/6482/swedishknockers.jpg
Cause have a look at this as well (already posted for those with longer memories)
http://forum.scooterforum.net/forum/f88/ronkens-honda-mt-project-153286/
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=248221&stc=1&thumb=1&d=1318126518http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=248222&stc=1&thumb=1&d=1318126230http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=248223&stc=1&thumb=1&d=1318126299

I suspect this cylinder and head were never meant to be fitted to that engine. Where did you find them? Some 250 cc V-twin?
The head could do with an additional bleed connection. As it is, most of the head and even a part of the cylinder are air bubble cooled...
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=261416&stc=1&thumb=1&d=1333551562
Yes it is the front cylinder off a NSR250 as the 250 on the cylinder is also a bit of a giveaway as well.
the front cylinders are not coveted as they have the angled plug. The std backyard and HRC mod is to replace them with another rear one and a shorty plug.
Wob sat her on as i guess he had one lying about he has some mods planed for her but i suppose the engine has to be mounted in situ first.

I must admit I thought you may have a go an giving a technical explanation of the outputs Reed Vs Disk Frits above er... and below?

I was looking at a picture of a NSR and had a thought it looks real large on the ignition side to accommodate the electric start.
So how much more power would it develop with disk valve induction instead of Crankcase reed ho much more is in it if it were say 35 with the reeds.
it would be interesting to have a 6 speed liquid cooled power valved Honda. kind of like this one.

added some lionheart as well, as i said previously i am missing a few, plus a few remain lost in Husaberg Manor maybe i will have a proper look sometime.
One has a beautiful 955 Ducati. Is it wrong to covert one , Possibly, but i do anyway.

Frits Overmars

5th April 2012, 22:26

... I thought you may have a go at giving a technical explanation of the outputs Reed Vs Disk Frits above er... and below?A technical explanation? Nah, too much to do today. But since you were kind enough to post that picture of your sex six sisters, I will show some curves of my own.
When Jan Thiel went to Derbi to design the bike we now know as the Aprilia RSA125, he encountered the 125 cc reed valve Derbi ridden by Lorenzo the previous season. Jan played around with the reed valver as well, because he wanted to find out the differences between reed valve and disk valve power. He managed to extract 2 HP more from the reed valver than anyone else had ever done before (never mind the fairy tales of reed valve 125s producing over 50 HP; those Horses must have been Shetland ponies, probably measured at the piston ring).
My graph shows the power curve for the Aprilia RSA, the Aprilia RSW and that best-ever reed valve Derbi. It's not quite in the same league as the rotaries, hmm?

EDIT: Shame on me; I discovered that I posted a wrong graph (and I do not have the correct one at hand here in Holland). Power curve DERBILOR shows the reed valve Derbi as Lorenzo rode it. After Jan finished playing with it, it had 49 HP. Still, the best-ever disk valver produced 10 % more power than the best-ever reed valver.

husaberg

5th April 2012, 22:48

A technical explanation? Nah, too much to do today. But since you were kind enough to post that picture of your sex six sisters, I will show some curves of my own.
When Jan Thiel went to Derbi to design the bike we now know as the Aprilia RSA125, he encountered the 125 cc reed valve Derbi ridden by Lorenzo the previous season. Jan played around with the reed valver as well, because he wanted to find out the differences between reed valve and disk valve power. He managed to extract 2 HP more from the reed valver than anyone else had ever done (never mind the fairy tales of reed valve 125s producing over 50 HP; those Horses must have been Shetland ponies, probably meassured at the piston ring).
My graph shows the power curve for the Aprilia RSA, the Aprilia RSW and that best-ever reed valve Derbi. It's not quite in the same league as the rotaries, hmm?

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=261462&stc=1&thumb=1&d=1333621581

Thanks for that Frits i kind of thought maybe 2 or so but bugger. Wow that is quite significant, far greater difference than i would have expected.
(I am assuming the cylinders were similarly spec'ed though?)
mmmmm.... :shifty:nice to know if Vanessa were say, to make 35hp there could be another 3 or so HP to be gained by using a side sucker. Also one cunning advantage is my home circuit is, all bar one corner, exclusively right handers. So if it were to be placed on the ignition side i would be far more likely to wipe out the er.....water pump than the carb. On my inevitable re-acquaintance with the moss bales;) Oh how they must have missed me. For i rarely missed them.:Oops:

Don't Team ESE have a RG150 engine and a RGV250 cylinder in the parts bin. I see they like disk valves. :scratch:
So I wonder .......if they were to combine all those bits and build a H20 6 speed disk valve 100 cc engine using 90's design rather than a 70's design engine.:whistle:

TZ350

6th April 2012, 09:55

Shit itself on the dyno last night, we think the problem is the exhaust port hammering the piston and trapping the ring. Just got it back together, dynoed up ok :sweatdrop, packing now and off to Kaitoke be there about 7-8 ish tonight. See you all Sat sign in. ... :D TeeZee & Kel

Away 10-45am .....

speedpro

6th April 2012, 11:00

http://www.pvlsverige.se/vrm/verkstad/Honda1.jpg

Yes it would be good to pull me finger out me bum and stop procrastinating but just wondering.
Those aprillia's seemed to go ok

The rear half of those cases looks like an MB100, I'm not kidding. Will post photos later. There is even the little block for the engine number and the hole for the neutral switch.

husaberg

6th April 2012, 11:10

The rear half of those cases looks like an MB100, I'm not kidding. Will post photos later. There is even the little block for the engine number and the hole for the neutral switch.
Er... the cases could look a lot like a Honda mb100 because they are a Honda MB50:yes: well they could be mbx or NS50,nsr50 but pretty sure mb5

Jeebus! that is pretty flash looking stuff!EDIT: So that MB50 cases yeah?
Did you follow the link to the Roffe follow picture of man with tools on the navigation home site man witit looks like he offers it as a kit for the mb5. The building of this particular motor is in another thread i will have a look in my favorites/or bookmarks.
But it was i think in the racing 50's site. here you have to log on to see the pics

Well...For those who wish for some work shop porno...http://www.british50ccracing.com/forum/viewtopic.php?f=25&t=1889&st=0&sk=t&sd=a&start=45

My project at the moment is to tune a Honda MB 50 6 Speed engine.
Components like:
Honda MB casing with rotary inlet Alá VRM
Minarelli AM 6 Crank
Main bearing L-20 on both side.
Derbi special tuned barrel
Thyron Ignition.
Stroke 39mm
Bore 40mm
Changeable combustionchamber.
Mikuni TMX 27mm Carb.
VRM Exhaust

Hello everyone you on this side!http://mt5.se/bilder/5719-slidmatad-honda-mb5-motor-update-med-bilder-text-fran-roffe.html
I intend to write a short description on what you see, so that it does not become mass
awkward expectations and misunderstandings.
It has also expressed wishes about may to see more pictures so I will fix it ahead.
This engine is built on order of a customer that will go fastly straightly forward and we come probably
may to read if it farther forward this summer would I faith.
It is not at me farther so can thus it not become filmtajm from me in all cases.; =)
MVH
Roffe@VRM
http://img144.imageshack.us/img144/1113/vrmhondaslidprojekt.jpghttp://img144.imageshack.us/img144/5044/vrmhondaslidprojekt1.jpghttp://img54.imageshack.us/img54/3223/vrmhondaslidprojekt3.jpg
http://img156.imageshack.us/img156/3888/vrmhondarotaryprojectcrgr7.jpg

The engine is one old Honda MB that I have rebuilt in order to among other things contain one Minarellivev instead.
What one must do is to rebuild lager situations and location of packboxen on right
since the cranks are little individual.
Moreover, one must produce a new small primary drive so drivningen works.

The sets put one up the block in an angle shelf stem to change pinnbultsmönstret and
do the possible to center the cylinder correct against the crank arbor.
Here, you come little pictures on such job so see how it will be done!.

The first picture shows: after to have drilled up orginalhålen for pinnbultarna so gängar I in
aluminum bar stem to do the possible to get another bolt standard.
In this fallen for Derbicyllen that has 56 x 56 mm.

Fräsning centrering arborrning and correct location is rottenly precise.

Is that Roffe that Swede of MB50 disk valve Derbi cylinder fame?
http://translate.google.co.nz/translate?hl=en&sl=sv&u=http://www.pvlsverige.se/vrm/index/index22.html&ei=6RiITqL7LqbkmAXduKwr&sa=X&oi=translate&ct=result&resnum=1&sqi=2&ved=0CCAQ7gEwAA&prev=/search%3Fq%3Dhttp://http//www.pvlsverige.se%26hl%3Den%26biw%3D632%26bih%3D35 0%26prmd%3Dimvns
249742249743249744

F5 Anyone
This left me speechlessIt is a Honda 50 converted to Rotary valve and a LC Derbi top end and Minerili crank.Whats the go with these bearings?
http://translate.google.co.nz/translate?hl=en&sl=sv&u=http://www.pvlsverige.se/vrm/index/index22.html&ei=6RiITqL7LqbkmAXduKwr&sa=X&oi=translate&ct=result&resnum=1&sqi=2&ved=0CCAQ7gEwAA&prev=/search%3Fq%3Dhttp://http//www.pvlsverige.se%26hl%3Den%26biw%3D632%26bih%3D35 0%26prmd%3Dimvns
Go to the bit with the face and the thumbs up.

Yes they looked a little like the bearings Suzuki use in some steering heads But What is the advantage as a main over a std Bearing, less Fiction?
I couldn't figure out the magnetic bit So its (Magneto Bearing) I guess that Google translate got a bit lost in Translation from Swedish.
Had you heard of this Guy Wob?
Your Right there is some neat stuff and info there.He obviously makes great use of his long winters.The MB disk Valve seems available as a kit too. Here is a forum he is on. Best of all he seems to speak English too, by the look of it.
http://50iniepoca.forumfree.it/?t=43987929&st=75
Mike he does a lot of MB stuff like a kokusan ignition just like the real racers, lots of inlets carb kits reeds etc electric pumps etc etc ....
So now Frits.
Does that mean i am no longer the thread Goldfish?Oh bugger i can't throw stones from this glasshouse/bowl. Oh well i will go back to the corner of my bowl then
bugger where is the corner. oh well if i keep swimming around it will be here somewhere. Oh what were we talking about again?

Frits Overmars

6th April 2012, 23:52

Something to think about while the rest of the family occupy themselves with buying, boiling, painting, hiding, searching, finding and eating easter eggs: a couple of recent videos from the Dutch 50 cc scene.
http://www.youtube.com/watch?v=mvV4xbFKs0g&feature=relmfu
http://youtu.be/0odVzSgufjk

2T Institute

7th April 2012, 01:06

Where is rgvbaz he loves his 'trombone' sections :killingme

Looks like it works a treat, which clever Dutchman thought of that Frits? I would have a map 2 for it when warming up in the pits making it go longer with rpm.

Frits Overmars

7th April 2012, 01:34

Looks like it works a treat, which clever Dutchman thought of that Frits? I would have a map 2 for it when warming up in the pits making it go longer with rpmIt was designed and built by Richard Maas http://www.adriaanmeeuwsen.nl/team-pagina.html. Hopefully we will see it in action next monday.
And if I were you, I would make it go shorter with rpm :whistle:.

dinamik2t

7th April 2012, 02:30

:niceone::niceone:
I'm impressed with how it slips all nice and steady!

Frits, may I ask, wouldn't it affect the 1st pressure wave in the diffuser, when fully inserted? -in a way to have a measurable impact on pipe effects I mean

Frits Overmars

7th April 2012, 03:28

....Frits, may I ask, wouldn't it affect the 1st pressure wave in the diffuser, when fully inserted? -in a way to have a measurable impact on pipe effects I meanYou may. It will affect all the waves in the pipe. And it does have a measurable impact on pipe effects :2thumbsup .
But I suspect you are referring to the header intruding into the diffuser. It doesn't. Even in the shortest position everything is smooth inside the pipe.

dinamik2t

7th April 2012, 05:13

Indeed, my question was about the header smoothness and everything around that. You are a master suspector http://dinamik.20.forumer.com/images/smiles/dinamik/yzWkNl1ZbVZZqLSgfoYSN7N7O4k=.gif
And obviously, since the 1st would be affected, the following ones would be affected also.:facepalm:

The header is as long as the displacement I suppose.

The whole innovation of system reminded me of your 24/7 valve somehow. So, I have another question since I may.
I remember you giving directions for an experimental 24/7 at Pitlane. 'One petal should suffice and valve should be placed in a way to direct flow correctly'.

261518

Say we have the above valve. The side with the opening & reed petal should look up towards the cylinder, or down towards the crank?
(I assumed I didn't need a new may permission, sorry)

Frits Overmars

7th April 2012, 05:28

Indeed, my question was about the header smoothness and everything around that. You are a master suspector
261518
Say we have the above valve. The side with the opening & reed petal should look up towards the cylinder, or down towards the crank?
(I assumed I didn't need a new may permission, sorry)You are a master assumer, Dinamik. But I don't see no valve....

dinamik2t

7th April 2012, 05:36

Thanks! It has been my dream since forever.:pinch:
How about now?? It's in gif format.

261519

Frits Overmars

7th April 2012, 06:05

How about now?? It's in gif format.

261519It's fine now.

I remember you giving directions for an experimental 24/7 at Pitlane. 'One petal should suffice and valve should be placed in a way to direct flow correctly'.I don't remember me saying it quite like that. I said something like 'one petal should suffice and once the engine runs in the powerband, that petal should swing out of the way so it will not hinder the flow'. That requires a hinge, like so:

dinamik2t

7th April 2012, 06:13

Yes, ok about the mechanism to open and hold the whole petal steady. I coundn't CAD it, that's why it's not there.
My question is about where the reed side of the valve should 'look'.
Assuming - :shifty: -the large angle side has the reeds, should it be looking at the cylinder or at the crank?
It might seem obvious that reed side should be up, but my question derive from having seen reed valves tilted downards and others upwards.

(I -probably- exaggerated the angles to make my point)

edit:

To help you suspect - :shifty: - me: why should it be the right (or the left) ?

261521

husaberg

7th April 2012, 06:13

You are a master assumer, Dinamik. But I don't see no valve....

Much more of a master-debater myself:innocent: I reckon I am finally getting a handle on it now.

It was designed and built by Richard Maas http://www.adriaanmeeuwsen.nl/team-pagina.html. Hopefully we will see it in action next monday.
And if I were you, I would make it go shorter with rpm :whistle:.
Didn't we discuss this a while back and decide it was worth the effort?
or did i give up to soon?

The 24/7. I was thinking along the lines of electromagnet (bloody stainless steel probably ain't magnetic is it). Or with pneumatics.?
Or

Has anyone ever tried a butterfly style valve in place of the reeds.(much like a carb or throttle body or tz's atac with a light spring.)Obviously needs to be mounted 90 degrees from pic.
http://t3.gstatic.com/images?q=tbn:ANd9GcS1mQid5s_zfrNSU8hQ0TRd__n9XQdjh uhcPknjMIBJkrKsbZk1K6d84_8chttp://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=259892&stc=1&thumb=1&d=1304576332
I know early 2 strokes had tried poppet valves.But never seen a butterfly valve (could be a good reason for this)Might not open?

http://t2.gstatic.com/images?q=tbn:ANd9GcR3N2_aBBHOg8bG5T8iyPP2fReHIz8rP KejL81XK4Jf7UxoL_O0http://t2.gstatic.com/images?q=tbn:ANd9GcQz_5_ASXrckrho7X8qJcE1aIseCWfBk 2Hy8YEbE0FLWotoUrQmSpkLR0vxhttp://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=261544&stc=1&thumb=1&d=1333751174http://www.norham.fr/system/html/vanne-khas-c7fbce01.jpg

The other thought was for a flat style reed plate much like these below
Only with Boyesen like plates rather than the curved stoppers ( to keep the length of the let nice and short) that way it could simply slide out of the way. As it is not meant to make power of the powerband anyway just aid starting and low speed running i don't see why the shape or flow characteristics would be that important.
Failing that a flat plate would also be a lot easier to hinge?

Frits Overmars

7th April 2012, 06:17

Say we have the above valve. The side with the opening & reed petal should look up towards the cylinder, or down towards the crank?For the flow into the transfer ducts it would be best if the petal would look up towards the cylinder. But that is rather irrelevant because any time the petal is 'in function' the engine is running outside the powerband anyway.
I would have the petal look down towards the crank in order to concentrate the flow towards the big end when the petal is operative.

dinamik2t

7th April 2012, 06:20

For the flow into the transfer ducts it would be best if the petal would look up towards the cylinder. But that is rather irrelevant because any time the petal is 'in function' the engine is running outside the powerband anyway.
I would have the petal look down towards the crank in order to concentrate the flow towards the big end when the petal is operative.

I see. Thank you!

-uploaded a better pic above, by the way-

Myron

7th April 2012, 23:25

For the flow into the transfer ducts it would be best if the petal would look up towards the cylinder. But that is rather irrelevant because any time the petal is 'in function' the engine is running outside the powerband anyway.
I would have the petal look down towards the crank in order to concentrate the flow towards the big end when the petal is operative.

Frits, are you saying that when in the powerband, a petal would tend to be open all the time? Or that you could rig it so it would have to be open all the time when in the powerband?
Myron

2T Institute

8th April 2012, 01:06

It was designed and built by Richard Maas http://www.adriaanmeeuwsen.nl/team-pagina.html. Hopefully we will see it in action next monday.
And if I were you, I would make it go shorter with rpm :whistle:.

Yes but in the pits it would go longer with rpm :psst:

Suzuki Gallina team fell into the same trap trying to get a ATAC valve to work after seeing it on a works honda , one day a mechanic wired it up incorrectly and made it close at high rpm , next year all the RGB 500's RM's and RG road bikes had a AEC .

Frits Overmars

8th April 2012, 07:59

Frits, are you saying that when in the powerband, a petal would tend to be open all the time? Or that you could rig it so it would have to be open all the time when in the powerband?I'll rig it so it sways out of the way and stays there as long as the engine runs in the power band.

Frits Overmars

8th April 2012, 08:01

husaberg

8th April 2012, 08:32

More news from Richard Maas.
Only problem so far: the piece of pipe that is fixed to the cylinder, is shrouded by the pipe that slides over it, so it gets very hot. Too hot for the Viton O-ring that is taking care of sealing and low-friction guidance. Any bright ideas, anyone?
Lab seal with piston rings.I know a "boring" answer.:corn:

Ps i am not bright so i used someones else's idea.Mr Woolley (he missed a bit of the two stroke physics though)

Yow Ling

8th April 2012, 08:42

I think Husa is half onto it, make a Labarynth in the sliding part so there will be no contact with the inner, then seperate the guiding function using a couple of rods like he did at the rear mount on the pipe.

Frits Overmars

8th April 2012, 08:43

Lab seal with piston rings.I know a "boring" answer. Ps i am not bright so i used someones else's idea.Using someone else's ideas is a sign of intelligence. But the piston rings are a no-go. The wall thickness of the inner tube is too small; there is no place for ring grooves. So the rings would have to sit in the collar at the front end of the outer pipe and seal inward. That is a trick piston rings do not master... Or do they?

husaberg

8th April 2012, 09:22

Using someone else's ideas is a sign of intelligence. But the piston rings are a no-go. The wall thickness of the inner tube is too small; there is no place for ring grooves. So the rings would have to sit in the collar at the front end of the outer pipe and seal inward. That is a trick piston rings do not master... Or do they?

Can't picture the setup but think i see what you mean.But they could seal both ways. I am trying to think of an application where a bore would travel over a seal or ring can't think of any. Yet (Air pump?) like a pushbike?it would be problematic with the seals trying to tip over.
But it doesn't mater not as it looks like viton is only good for 200 degrees c gee that low what are the Orings in heads made from?

So there are other material that could work to a higher working temp.Not much but at least higher
what about a soft metal o ring.

I have seen plastic rings in a air pump of sorts were they ptfe or tfe.

Anyway attached below.

What sort of materials are in brake caliper seals the ones with carbon disks must have still got kind of hot with the disks glowing red hot and all that.

Gigglebutton

8th April 2012, 09:53

speedpro

8th April 2012, 09:54

Fit a sleeve over the header where the sliding seal is. The sleeve is a few mm larger than the pipe. With a bit of insulation between the header and the sleeve the temperature could be dropped enough for the seal to survive.

teriks

8th April 2012, 09:59

More news from Richard Maas. Did his trombone pipe give the desired results? O yes. At 10,000 rpm it gives 4 HP more than the same engine with a fixed pipe. It runs over 17,000 rpm without the need for a powerjet and with a fixed ignition timing. It is miles better than an engine with an exhaust power valve. And the mapping of pipe length, ignition timing and powerjet pulse width has yet to be carried out. Maybe the powerjet can disappear altogether.
Only problem so far: the piece of pipe that is fixed to the cylinder, is shrouded by the pipe that slides over it, so it gets very hot. Too hot for the Viton O-ring that is taking care of sealing. Any bright ideas, anyone?
The toughest O-ring material I'm aware of is the Trelleborg Sealing Solutions material designation J8325. -Max operating temp. 325°C
At least well above any Viton material, but perhaps not enough. Could be a drop in solution though.

Isolast® is Trelleborg Sealing Solutions proprietary perfluoroelastomer. It combines the elastic properties of fluorocarbon (FKM) with the outstanding chemical resistance and the high temperature stability of PTFE. Isolast® seals can be used for applications in high temperature service up to +325 °C / +615 °F. Isolast® O-Rings are available in metric and inch dimensions to ISO 3601 and AS 568.
Linky: http://www.tss.trelleborg.com/global/en/products_2/orings_2/detailpages_orings/isolast-perfluoroelastomer-o-ring.html

If you get close using this material, perhaps cooling fins on the shrouding part of the pipe as a band aid.

husaberg

8th April 2012, 10:18

Does it need to be sealed where it slides why not just the end and accept or alter the volumes so it to be part of the pipe?
or a bellows type seal over the top like a FWD exuast convoluted pipe.or a convoluted pipe by it self?
another possible seal could be a spring it would create a torturous path and would? allow the sliding .
Automatic rifles ans such like must have i guess some high temp seals or is it all based on fine machined tolerances?

In the catalog i posted it says Peek is good for applications to 600f as well (315c)

Hindsight is rifle piston helped to be sealed by the very gas pressure they use? if the pressure was equalized on either side would that help?
it seems this very gas pressure could pos be made to help move the pipe as well two birds.
http://209.200.109.169/arfcom/gasimpingement.gif

Ps ..er make love not war. Unless it is with the 4 strokes.

Question for Frits
That is real clever with the dutch set up seeming to use either a rotary or elliptical motion in the actuation to it would seem, speed it up.(The variable length)
As you may remember i wanted to use compressed air. You then suggested LPG. which is very cold while under pressure, also Nitrogen is cold also while pressurised:cold:mmm....

Something to think about while the rest of the family occupy themselves with buying, boiling, painting, hiding, searching, finding and eating easter eggs: a couple of recent videos from the Dutch 50 cc scene.
http://www.youtube.com/watch?v=mvV4xbFKs0g&feature=relmfu
http://youtu.be/0odVzSgufjk

Myron

8th April 2012, 10:18

I'll rig it so it sways out of the way and stays there as long as the engine runs in the power band.

Well, the 24/7 inlet idea is novel, certainly very interesting. My bet is that it either is a huge success, or a flop...but anyone could have guessed that. I would put my money on the latter, just because all inlet tuning will be non existant. And if thats the case, there may be a large hp loss. Who knows.
Myron

Ocean1

8th April 2012, 11:38

So the rings would have to sit in the collar at the front end of the outer pipe and seal inward. That is a trick piston rings do not master... Or do they?

Can't imagine why not. They'd be tensioned inwards of course, possibly with porting from upstream to the rear of the groove? Maybe not, what's the pressure diferential?

Stealing more existing ideas for materials would be a good idea, hard chrome surface for the inner tube? Would want to precision grind it in any case...

husaberg

8th April 2012, 11:51

Can't imagine why not. They'd be tensioned inwards of course, possibly with porting from upstream to the rear of the groove? Maybe not, what's the pressure diferential?

Stealing more existing ideas for materials would be a good idea, hard chrome surface for the inner tube? Would want to precision grind it in any case...

I just thought it is rather obvious to i am afraid so forgive me. Assuming it is the temperature causing the sealing issue why not lower the outside temperature of the inner pipe by using a ceramic like coating on the inner wall of the header. That way there would be less transfer of heat to the outside wall.less heat less issue's plus possibly more top end power with a hot pipes as well. if it is the hot exhaust gases causing the problem a metal seal ahead of the rubber seal while not being that effective would certainly at least lower the temp exposure?

QuickSilver are delighted to be able to offer customers the option of Zircotec ‘Thermohold GP’ ceramic coating for exhaust manifolds and components.
Developed by the former engineering division of the UK Atomic Energy Authority (AEA) at Harwell in Oxfordshire, the company now known as Zircotec, was privatised in 1996.
This is not intended as a cosmetic enhancement (though they do look good) it has the potential for a significant contribution to the engine’s thermal efficiency.
The function of the Zircotec coating is to consistently resist the loss of heat energy through the exhaust tube.
This zirconia-based ceramic coating was originally produced as a barrier for the thermal management of coolant pipes to & from reactor cores.
It has now been developed specifically for exhaust systems and is known as ‘Thermohold GP’.
Zirconia has a thermal efficiency of less than 1 watt per metre per kelvin.
By contrast, Alumina has a thermal efficiency of 4 watts per metre per kelvin.
The way the Thermohold coating works is, primarily, by inhibiting radiated heat from the surface of the material.
It forms a physical ceramic barrier so that the heat on the inside of the exhaust remains inside.
In some applications a difference, between the gas on the heated side and the external air, of up to 200°C can be seen.
The fact that the heat is held within the exhaust system, therefore effecting back pressure, can also provide power advantages.
Typical benefits of using Thermohold GP are:
· Significant improvement in heat management within the engine.
· Prevention of local component and chassis damage from radiated heat.
· Reduced thermal expansion of the coated product resulting in lower stress on the mountings and surrounding structure.
· Giving a degree of fire resistance as a lightweight heat shield, the saving in weight over conventional insulation can be considerable.
· Enhanced component appearance.
· Increased power through retaining heat energy within the exhaust and providing greater gas velocity.
This is not a paint or surface treatment, it resembles a traditional enamel coating in its thickness.
It is applied in three stages, surface preparation, metal bond coat, ceramic coating.
Coating thickness: approx 300 - 350µ comprising ~ 100µ metal bond coat and 200-250µ ceramic.
Total weight increase will be 1.6 > 1.7 kg/m2
For Motorsport, an additional important reason for coating is to protect surrounding structures - carbon-fibre parts, if scorched, can delaminate.
It is also important to stop heat ingress into mechanical areas such as gear boxes and oil supply and radiator lines.
Compared to ‘wrapped-round’ glass fibre, it is not only less bulky but it also does away with the need for straps or brackets.
The natural finish colour is white, it can also be finished in grey or black by the application of an additional coating.
Typical Exhaust system applications include:
· Air-cooled engines where heat management is so important.
· Turbo-charged engines where exhaust gas velocity is paramount.
· Motorsport use for all the benefits noted above
· Heat management in a crowded engine bay.
· Emissions-critical engines where consistent engine & exhaust gas temperatures must be maintained over all conditions.
Notes:
In the early 1980s, Toyota researched production of a ceramic engine which could run at a temperature of over 6000 °F (3300 °C). Ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater efficiency. Fuel efficiency of the engine is also higher at high temperature, as shown by Carnot’s theorem. In a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts.

Ocean1

8th April 2012, 14:02

I just thought it is rather obvious to i am afraid so forgive me. Assuming it is the temperature causing the sealing issue why not lower the outside temperature of the inner pipe by using a ceramic like coating on the inner wall of the header. That way there would be less transfer of heat to the outside wall.less heat less issue's plus possibly more top end power with a hot pipes as well. if it is the hot exhaust gases causing the problem a metal seal ahead of the rubber seal while not being that effective would certainly at least lower the temp exposure?

Yup, all true. Ceramic coating inside the thin walled inner tube might be a problem in both applying it and keeping it in place. The ceramic has a different thermal expansion than steel, in my experience it tends to flake off in such situations. In fact if you could keep it in place you could probably make a better case for coating the OD of the inner and running a reinforced carbon ring against that.

Heat? What heat?

husaberg

8th April 2012, 16:00

Yup, all true. Ceramic coating inside the thin walled inner tube might be a problem in both applying it and keeping it in place. The ceramic has a different thermal expansion than steel, in my experience it tends to flake off in such situations. In fact if you could keep it in place you could probably make a better case for coating the OD of the inner and running a reinforced carbon ring against that.

Heat? What heat?

found these seals well the heat and pressure from a shotgun must be substantial
http://www.brownells.com/.aspx/lid=11149/guntechdetail/
diameter appears ballpark.

these alsohttp://www.skf.com/portal/skf_pol/home/products?contentId=692594&lang=en
http://www.sealanddesign.com/category/Temperature-Ranges-of-Elastomers/466.html
http://www.sealanddesign.com/images/content/temp-chart.gif

Ocean1

8th April 2012, 16:42

found these seals well the heat and pressure from a shotgun must be substantial
http://www.brownells.com/.aspx/lid=11149/guntechdetail/
diameter appears ballpark.

these alsohttp://www.skf.com/portal/skf_pol/home/products?contentId=692594&lang=en
http://www.sealanddesign.com/category/Temperature-Ranges-of-Elastomers/466.html

The first is standard hydraulic seal design, quite high drag. Also the moving element is PTFE, not good enough in that environment.

The second is a simple elastomeric ring, they don't say what the material is but one of the silicon family is probably a good choice. Might be the best readilly available material for the trombone application too, although it's not very abrasion resistent. Unless you've got contacts at Boeing or Northrop Grumman, they use some hideously expensive and very proprietorial extreme temp elastomers.

husaberg

8th April 2012, 17:00

The first is standard hydraulic seal design, quite high drag. Also the moving element is PTFE, not good enough in that environment.
Unless you've got contacts at Boeing or Northrop Grumman, they use some hideously expensive and very proprietorial extreme temp elastomers.
Don't ask NASA they are still working on that one even with aviation contacts:eek5:

For Frits
With the RSA being gear driven disk was there ever any consideration given to reversing the rotation to allow for a rudimentary retard function along the lines of a centrifugal advance ignition.
I ask because Bell quotes significant high rev gains from a mildly retarded opening and closing and visa versa (He even showed curves). So it would seem (if bell is right) the timings could be varied it could to allow for a broader output if timed for normal peak at full retard. Just a thought possibly retarded.;)
http://wimlex.no-ip.com/forumpics/wegraceforum/fotoalbum/Retro/Dutch%20TT%20Assen%202008/slides/100_0075.jpg

Ocean1

8th April 2012, 17:32

Don't ask NASA they are still working on that one even with aviation contacts:eek5:

There's a design for a rolling torroidal seal element, (fancy name for rolling “O” ring) I've used before which would minimise silicone's susceptibility to abrasion. Necessitates exposure across the full seal cross section though, and you’d have to allow for that in volume calc’s.
Don’t have my magic crayon here, you have to imagine it.

Frits Overmars

8th April 2012, 21:08

Thanks very much for the input, guys. I will pass your suggestions on to Richard Maas (and try to convince him to register as a Kiwibikers forum member :D).

teriks

9th April 2012, 02:12

<snip>
The second is a simple elastomeric ring, they don't say what the material is but one of the silicon family is probably a good choice. Might be the best readilly available material for the trombone application too, although it's not very abrasion resistent. Unless you've got contacts at Boeing or Northrop Grumman, they use some hideously expensive and very proprietorial extreme temp elastomers.
I have a similar seal between the cylinder and pipe, the experience from those is that silicon offers nothing or very little over viton, or even NBR, in terms of service life.
Now I need no more than, say, 10 minutes service life, so I can get away with using the simple materials and change often.

IMO, The FFKM material I linked earlier should be a much better candidate for this application.

husaberg

9th April 2012, 09:08

Just a thought from RC type engines i know almost nothing about them but i understand many run without piston rings.
could this provide a possible pipes seal solution?

ABC = Aluminum (PISTON), Brass (CYLINDER) Chrome (CHROME PLATED cylinder internally) The compression seal is made by a slightly tapered fit between the piston and cylinder. The brass cylinder has the same expansion rate as the aluminum piston therefore, it maintains a good seal as the engines heats up. Since chrome is substancially harder than the aluminum piston, this is a (semi) bearing surface between the piston & cylinder therefore there's no scuffing or galling, if there's adequate lubrication.

ABN= Aluminum (PISTON) Brass (CYLINDER) Nickle (NICKLE PLATED cylinder internally) The compression seal is identical to the ABC. IE:tapered fit

AAC= Aluminum (PISTON) Aluminum (CYLINDER) Chrome (CHROME PLATED cylinder internally) The compression seal is identical to the ABC. IE:tapered fit
http://tech.flygsw.org/abcvsringed.htm

twotempi

9th April 2012, 10:52

My guess is either carbon ring seals - used in aerospace industries and expensive , or a lower tech arrangement using relatively wide ( say 2mm ) cast iron piston type rings running on a machined surface on the outer sliding component.

Probably would try 3 rings in grooves on the inner component rather than the outer sliding component. There should be enough oil around in the exhaust to lubricate the arrangement.

Would be cheap enough to make to find out if it works OK. Rings can be made by most engine shops . Orientate the ring gaps @ 120 degrees to minimise leakage.

teriks

9th April 2012, 11:16

Just a thought from RC type engines i know almost nothing about them but i understand many run without piston rings.
could this provide a possible pipes seal solution?
Now this is something I'm very familiar with.. but nah, requires stupidly small tolerances.
Unless the FFKM material is up to the task, I'm leaning more towards your inverted piston ring idea.
A good candidate for rings could be brass or bronze, or anything substantially softer than the pipe material.
Without a polymer dampener (O-rings), I'd guess for that kind of arrangement vibration will be limiting part life unless you do something clever...

husaberg

9th April 2012, 12:10

Transitional seals i had never heard of them.
http://www.jetseal.com/images/productimagetransitional.jpg

http://www.jetseal.com/translational.php
The Translational Seal is designed for use in applications where moderate linear motion occurs. Typical applications would be a piston mount application where the seal slides up and down in a bore. When friction and driving forces need to be balanced, the Translational Seal ring provides the best solution for moderate linear motion and minimized leakage rates.

Metallic Translational Seals offer reduced leakage rates in piston applications compared to typical Piston Rings or standard metal O-rings. JETSEAL customizes this seal to accommodate platings and unique mating surfaces in pneumatic and liquid applications

Translational Seals thrive in environments like: high pressures to 60,000 psi. temperatures from 320 F to 1300 F, well in excess of typical O-ring and traditional piston ring operating ranges. pneumatics. gas and liquid applications.

marsheng

9th April 2012, 13:32

TZ350

9th April 2012, 16:02

I bought a complete NSR250 MC16 cheep and was going to use the frame for an F4. Once I got the bike, the motor and all else seems fine. I'm looking for reasons to put it into pre 89 F3 Category. Any with info on these, please contact me with PM as this is a bucket forum (and also all the chaps whose opinions I trust.)

Cheers Wallace.

Hi Wallace, this thread is probably a very good place to find and share any sort of 2-stroke tuning and prep info. NSR250 stuff could be very interesting.

TZ350

9th April 2012, 16:05

Race report from Kaitoke

Sat, was Kels first look at the track and he rode exceptionally well. Hamish who normally runs at the front, was happy to tell us how impressed he was with the Beasts acceleration. He expected to be able to easily swing past it exiting the top corner only to see the Beast pull away down the back straight. If the track had not been so new to Kel there may have been a real race for 1st as it was he finished 3rd, behind Rick and in front of Rich.

So there it was, the Beast flew, with no sign of the heat fade that’s supposed to affect aircooled 2-Strokes and Kel was able to peddle it at the very pointy end in A grade first time out on a new track. As Kel got to know the track better, it all looked good for Sundays points racing. I was feeling confident that we were in with a chance on Sunday.

The next time out Kel just quietly putted around in the two warm up laps, grided up and when the flag dropped the Beast had a heart attack and fell over.

WTF ….. The Beast screams around the track on full song then quits when taken out for an easy trot, what is that all about?????

Come Sunday Kel went out in the first points race on his trusty old FXR and finished 3rd, very impressive effort for a basically std chassis. Kel was well into the second race and chasing Rick, with a bit of exciting passing and re passing, then Kel dropped it trying to get around a back marker and that effectively handed Rick the North Island Series Win.

A Great Weekend racing at one of the best F4 tracks and with the nicest people in Motor Sport, what more could you want, a big thankyou to everybody who was there and those that organised and helped run the meeting, we had a great time, thanks.

TZ350

9th April 2012, 16:12

Kickaha

9th April 2012, 16:34

WTF ….. The Beast screams around the track on full song then quits when taken out for an easy trot, what is that all about?????

Sounds like the standard life expectancy of a two stroke

husaberg

9th April 2012, 16:54

Sounds like the standard life expectancy of a two stroke

Warwick remember people who live in glass houses shouldn't er......throw valves:wait:

For Wallace

http://profile.ak.fbcdn.net/hprofile-ak-snc4/372971_239342649444750_979745294_n.jpg
http://nsr-world.com/
http://www.dreamgate.ne.jp/nsr/indexstuff/jamietitle3.jpg
http://www.dreamgate.ne.jp/nsr/
http://tyga-performance.com/site/images/tygalogo.png
http://www.tygaperformance.com/site/index.php

Did you buy the one at Rangavegas?

Yow Ling

9th April 2012, 17:00

Hey Kickaha, thats not that much different than the bsa barrels and piston you brought round today, at least TZ will be able to get the piston off the rod !

Kickaha

9th April 2012, 17:02

at least TZ will be able to get the piston off the rod !

Already done that, I didn't notice the oil ring end gap when I was at your place, it's about 20mm on both of them and that piston is way more munted than mine

TZ350

9th April 2012, 17:52

WTF ….. The Beast screams around the track on full song then quits when taken out for an easy trot, what is that all about?????

261714

Sounds like the standard life expectancy of a two stroke

......... :bleh:

261718

To be on the safe side we had richened the mixture up (Blue line)

261717

And in case the piston might be to close to the head we tried an extra 0.5mm base gasket (Red Line) but we didn't like that and took it out again.

But it is interesting to see what lifting the barrel only 0.5mm does.

261716

There is no evidence the piston was hitting the head, just a lot of derbis crushed into it. I regret we didn't lift the head for a look after the first race, then we would know for sure, but it was going so well I didn't want to disturbe it.

261719 261720

The original dyno graph and ignition curve.

With a straight line ignition curve the engine made max power around 16 degrees, the advanced portion improved the lower power curve. The ignition curve is 16 degrees at 12,750rpm and retads 10 degrees by 13,500 rpm for max over rev. This curve was carefully developed on the dyno using full throtle runs and took a lot of work and time.

10 degrees retard, on full throttle is that excessive? is it OK to hold it on full throtle in the max retard area at 13-14,000 rpm for longish periods? like holding out to the end of a short straight.

Any way the problems happened at lower rpm and lesser throttle openings when the motor wasn't being driven at race pace.

One small point is that in the area off the pipe, I have found that the engine will not make much if any more power, as shown by the dyno load it will pull, but by adding a heap more timing, it will for sure
operate much , much better on part throttle response, on track.
Here is a 125 kart engine curve that made 50RWHp,and won 3 back to back 125 National titles easily.

This thing would deto like mad on part throttle at 6000 if held there, but on track it would pull out of 1st gear hairpins hard enough to spin the tyres on full throttle from the same rpm, then rev out to 14200.

A TPS and a 3D map would achieve a better result, but I didnt have a RS125 Honda carb at the time.

I am wondering if this could be the problem? and I might need to use a TPS and go the 3D map way, or at least switch between 2 maps depending on rpm and throttle position.

speedpro

9th April 2012, 18:49

The shape of the dents in the crown suggest a bearing problem, bits of cage have been escaping. Has the ring snapped, which I think is unlikely, or has the ring location pin moved allowing it to rotate? The amount chewed away at the front suggests detonation to me but the ring has been jammed down the front of the piston going by the curved mark on the piston so possibly another problem as well.

I don't think you'll be able to sandpaper those marks out and reuse it this time.

TZ350

9th April 2012, 18:59

The shape of the dents in the crown suggest a bearing problem, bits of cage have been escaping.

Has the ring snapped, which I think is unlikely, or has the ring location pin moved allowing it to rotate? The amount chewed away at the front suggests detonation to me

A brg problem, I did not think so, but possible, the mains are phenolic caged, so not from there. I will have a better look at the big end brg tommorow.

A section of ring is missing, clean break, both ring ends that normaly go around the locating pin and the pin itself are still there.

Bert

9th April 2012, 20:34

WTF ….. The Beast screams around the track on full song for a whole lot of laps then quits when taken out for an easy trot around in the two warm up laps for the next race, what is that all about?????

261714

Damage is in the exhaust port area, and thats a steel ring thats cleanly snapped in two....

I wander if things cooled down equally? or rather did something heat up too quick while putting around??
Was the ring gap correct for the temperature range you are working at? I've got a number of KT pistons that look similar due to incorrect ring gap settings; and ring pushing too far out into the exhaust port once things warmed up.
Could it be possible you sucked in something solid? I was amazed at the number of stones and bits sitting in the bottom of my bellypan after each outing.

I don't think you'll be able to sandpaper those marks out and reuse it this time.

Come on; a bit of devcon :innocent:

Yow Ling

9th April 2012, 21:29

Here a bit of history on disk valve engines, yes there is a 2 stroke cosworth in there , near the bottom, the Junkers torpedo engine is pretty interesting too

http://www.douglas-self.com/MUSEUM/POWER/unusualICeng/RotaryValveIC/RotaryValveIC.htm

TZ350

9th April 2012, 21:31

I've got a number of KT pistons that look similar due to incorrect ring gap settings; and ring pushing too far out into the exhaust port once things warmed up.

:scratch: thats possible, when the ring ends but together the ring would bulge out into the ex port.

2T Institute

10th April 2012, 01:38

WTF ….. The Beast screams around the track on full song for a whole lot of laps then quits when taken out for an easy trot around in the two warm up laps for the next race, what is that all about?????

That is the very essence of a highly tuned disc valve engine. There are NO easy trots, your either at 0% throttle and hard on the brakes or 100% throttle, something that long time japper riders have trouble adapting to when they ride Aprilia GP bikes.

breezy

10th April 2012, 02:50

it seems to make sense that at some point in manipulating the tuned lenth of the exhaust that a power gain would be achieived due to the tuning of the exhaust and barrel becoming sycronised to perform at its optimum. fabricating an exhaust to bang on dimentions to suit the barrel porting to give 100% , in the real world , must be nigh on impossible.if nothing the experiment would give a better tl measurement for which to produce an exhaust that gave 4hp more at 10000rpm than the fixed pipe it has been compared with. but it will be very interesting to see if the pipe produced gains throughout the rev range.. excellent innovation hope the fella finds a fix for the sealing problem:yes::yes:

SS90

10th April 2012, 07:57

WTF ….. The Beast screams around the track

Damage is in the exhaust port area, and thats a steel ring thats cleanly snapped in two.

I will dig out the dyno graph and ignition curve.

When you get wide exhaust ports like you now have, excessive ignition retard starts to show up in my experience, it is very well documented that the exhaust side of the piston crown will super heat when the advance is too much,(an unfortunate by product of the very reason retard gives over rev in regards to pipe temp, the "passing the heat onto the pipe" is benificial for over rev,but also unfortunately this "heat" has to go through the exhaust port, and as the piston opens the port, this same flame front super heats both the port and the exhaust side of the piston crown compounded by being air cooled ) this may well be today's problem. The dyno result of the lower compression (giving a very real band width increase, albeit for a wee loss in peak is something I would consider worth investigating, given the last few results, and the fact that you are trying to increase the spread, perhaps some investigation using this "less is more" concept would be worthwhile.

wobbly

10th April 2012, 09:30

The one and only reason you get a destroyed piston like that is DETONATION.
And looking at the Ignition curve you have posted it is immediately obvious why the thing keeps on blowing up.
NO 2T race engine making any sort of power can take anything like the advance numbers you have except in very fast, short burst, transient testing.
If at any time you had held the engine on part throttle at 10,000 rpm in 6th gear on the dyno, then done a roll on test it would have seized instantly.

I have never seen in 30 years of dyno testing any engine making reasonable Hp that would take 22 degrees of advance at peak torque, 12200 , then 20 * at peak Hp, 12400 in this case.
You have the wrong end of the stick completely with the comment about holding the engine in the overev region.
Its safe as houses up there as its BMEP is low ( little dynamic com ) plus there is not much advance, alot of the heat energy is going into the pipe - not the piston and head .

The real issue is exactly as per the comment of mine you posted re that 125 kart engine - the edvance curve it liked when used at full throttle in the mid range,would deto its tits off when held
for any time at those low rpms, be that on part throttle for a fast corner, or slow acceleration due to corner loading.
In a kart, part throttle is very rarely seen in a corner, as they have tons of grip.In a bike you run part throttle in corners most of the time, especially in the area just under the peak torque point
and having 27* of timing at 11,000 is going to kill the thing every time unless jetted well rich.

Using fuel to cool an over advanced engine looses power big time and it is impossible to set up an ideal ignition curve on a rolling road with no instrumentation at all.
With no deto sensing or being able to track EGT plus CHT you have no idea about what is happening with a particular ignition setup at all.

You used the port timing map off the sim I did as well as the head geometry, that put the overall engine efficiency quite a bit higher, but then ignored the combustion file that had an ignition curve tailored to suit the bmep
plus the overriding fact that it is an air-cooled engine.
If you take the sim as I last ran it then do a Turbulent Model with your ignition curve,the TuMax will be thru the roof,and the program will probably scream DETO WARNING at you in the mis range.

The way to go is pointed to by the fact that the RACE box has two curves that can be used in all sorts of ways - one of which is as per Honda RS125 setup, using a shift rum sensor that has allows alot of advance
in gears 1 thru 3, then uses a retarded map in gears 4 thru 6th when the acceleration rate is alot lower.
But really you first need to get a handle on a single map, that can be used in any gear at any TPS without it destroying itself.

These issues have nothing to do with an inherent problem with the 2T engine as some are joking about - I went to the kart nationals over Easter, with over 300 entries, only one siezure of a 2T all weekend that I heard about,
and that was caused by some idiot running so low on fuel it sucked air.

TZ350

10th April 2012, 10:01

richban

10th April 2012, 11:27

With no deto sensing or being able to track EGT plus CHT you have no idea about what is happening with a particular ignition setup at all.

Sort of what I was thinking. Maybe give Andrew a call and see if he can tell you where he got his fancy headphone setup. When I was playing with the igntech on the dyno with FXR it was really easy to hear the detonation with the phones. Might even be easy to make. After playing around at the track trying to jet the FCR I am sold on some actual diagnostics. Was going the wrong way. It wanted leaning not richness. As we are also pushing the limits of an air cooled single I am making a header with a lambda and EGT setup. Blow ups are expensive and really I would rather be racing than swinging a spanner. Maybe marking your throttle with about 10 positions and try loading and listening for det at each poz should give you a good idea of how the carb and ignition are working together. I had a small manifold leak when I was work with the headphones was very obvious something was wrong.

Onwards and upwards mate.

TZ350

10th April 2012, 13:24

The text of an email I received from Neels van Niekerk and posted here with his permission.

261733

Hi Robert

I know it has nothing to do with me but if the engine that broke the ring this past weekend was running the attached export it is no wonder. My experiences with these size exports are the following:

1. Never exceed 41mm for your bore ( *** )
2. Use at least 10mm radius for top corners
3. Use 100mm top edge radius
4. use 12mm radius for bottom corners
5. Use 80mm radius for bottom edge

Exceeding these gave more power but lead to the following:
1. Unexplained seizures
2. Broken rings after cooling off at the end of a race - runs fine and wins race, refuses to restart
3. Pinched rings - from severe hammering of piston top edge
4. Broken ring land at export
5. Ring breaks at low speed - not sure why but I think it just have more time to bulge into the export

If the only way to be competitive is to run such a port:
1. Piston and ring life is max 50km
2. Bore must be perfect
3. Very good (rounded) chamfer of top and bottom edge

I really like reading your ESE thread - gives me good feedback about where to improve my software and it is great to see such an enthusiastic bunch.

Regards
Neels

*** 56mm was the bore size enterd into the simulator.

wobbly

10th April 2012, 14:03

Rob, I thought you have been running that Ex width for a while with no issues ( it was in your original sim file ) - but I have never gone over 72% except in small bore sizes that seem to be able to keep the ring life OK.
Looks like it could now be a combination of too high bmep for the ignition that was OK before, and same with the Ex width, that cant be sustained now its starting to see some serious revs.

Running egt and cht you can watch both rise in unison as the rpm and power rise.
As soon as deto starts the cht will shoot up, the egt will flat line or drop as radicals are formed in combustion.
The best data logging gauge ( and the ONLY reliable egt probes ) are here.

http://www.exhaustgas.com/ProductDetail.asp?ProductID=805&DepartmentID=12&CategoryID=54&MenuID=sub4&BasketID=&RepID=

TZ350

10th April 2012, 14:33

Thanks for the info on the Data Loggers.

Rob, I thought you have been running that Ex width for a while with no issues ( it was in your original sim file ) - but I have never gone over 72% except in small bore sizes that seem to be able to keep the ring life OK.
Looks like it could now be a combination of too high bmep for the ignition that was OK before, and same with the Ex width, that cant be sustained now its starting to see some serious revs.

Yes, well this cylinder has done hours on the dyno with 200 odd dyno pulls and we have been running wide ports on other 72-75 ish cylinders too but whether this cylinder is exactly 73 or 75% I can't remember. I will have to check, and do you measure it on the inside or outside of the side champher, at this width including the champher probably makes a difference to the mechanical reliability too.

True, this particular cylinder has had little real track time, Te Puke practice & 3 races, Taupo 1 practice session and Kaitoke practice and 1 race.

It seems its on the limit mechanicaly and the ignition phlisophy looks the major culprit, or more likely it has more than one problem.

One thing is for sure though, this is only a small blip on the way to developing a reliable mid 30's hp Bucket

TZ350

10th April 2012, 17:37

There has been a lot posted about the piston issue today that makes sense. I will have to work through it bit by bit, I suspect there is more than one problem.

Rob, I thought you have been running that Ex width for a while with no issues ( it was in your original sim file ) - but I have never gone over 72% except in small bore sizes that seem to be able to keep the ring life OK.

261748 261749

I have done a lot of racing miles on this cylinder, The bore is 56.5mm and the exhaust port width is 41.56, so close to 74%. (or 73.55752 for anyone impressed by lots of decimal places).

261750 261747

The cylinder that failed at Kaitoke is also 56.5mm and the exhaust port width is 41.76mm so 74% there too.

It may be the shape and radius of the ports are different enough to be making a real difference.

Wob suggests 72% and Neels 73% so 74% is stepping over the line a bit.

By boring the cylinder to 57.75 I can reduce the ex port to 72% and still be a hair under 130cc.

rgvbaz

10th April 2012, 17:50

Frits mentioned a few pages back about insufficient blowdown causing the fresh charge in the transfers getting heated. Maybe this has a part to play also?

Dave

TZ350

10th April 2012, 18:00

Frits mentioned a few pages back about insufficient blowdown causing the fresh charge in the transfers getting heated. Maybe this has a part to play also? Dave

261753

Hi Dave, yes, I think there are probably several gremlins with their fingers in this pie and I have to look at everything but suspect the biggest gremlin is the ignition curve I used.

The one front center I think, or was it back right.

F5 Dave

10th April 2012, 18:03

. . ., The bore is 56.5mm and the exhaust port width is 41.56, so close to 74%. (or 73.55752 for anyone impressed by lots of decimal places)..
Oohh yes Rob. I'm very impressed by lots of decimal places. . . . Now presumably you measured that size at operating temperature, not machine shop 18deg?:nya:

Bert

10th April 2012, 18:13

Sort of what I was thinking. Maybe give Andrew a call and see if he can tell you where he got his fancy headphone setup. When I was playing with the igntech on the dyno with FXR it was really easy to hear the detonation with the phones. Might even be easy to make. After playing around at the track trying to jet the FCR I am sold on some actual diagnostics. Was going the wrong way. It wanted leaning not richness. As we are also pushing the limits of an air cooled single I am making a header with a lambda and EGT setup. Blow ups are expensive and really I would rather be racing than swinging a spanner. Maybe marking your throttle with about 10 positions and try loading and listening for det at each poz should give you a good idea of how the carb and ignition are working together. I had a small manifold leak when I was work with the headphones was very obvious something was wrong.

Onwards and upwards mate.

DYI Knock sensor. (I think I've posted this up before; but here we go again as it might interest people).

the start

http://www.clubsub.org.nz/forum/index.php?topic=7978.0;wap2

Sensor
http://www.jaycar.co.nz/productView.asp?ID=KC5444&keywords=knock&form=KEYWORD

audio amp
http://www.jaycar.co.nz/productView.asp?ID=KG9032&keywords=kg&form=KEYWORD

Computer software & electronics info:
http://home.netcom.com/~bsundahl/knock/sound/KnockSounds.htm#spectrogram

DYI option
http://www.autospeed.co.nz/cms/A_0353/printArticle.html

interesting calculation for detonation frequency (Khz)
http://www.autospeed.co.nz/cms/article.html?&A=0348
my bike should be around 11.4 kHz...

We use similar technology to record difference size rocks bouncing along river beds (all be it slightly more $$).

Another option is using ones Iphone/other type; and music mixing amp app thingy.
One could plug in a 5volt mic system into the phone rather than a guitar and isolate the key frequencies of det?!?

TZ350

10th April 2012, 18:16

Oohh yes Rob. I'm very impressed by lots of decimal places. . . . Now presumably you measured that size at operating temperature, not machine shop 18deg?:nya:

Being an industry insider, I will have you know, I casually heated the old calipers up in my hand before miss using them ..... so there.

TZ350

10th April 2012, 18:48

husaberg

10th April 2012, 18:52

Thought I had better check the triple port too. This is also a cylinder I have used a lot, before cutting the extra side ports into it.

261755 261754

Using all the best measuring gear money can buy, I found the bore is 56.5mm and I made the port window 41.13 for 72.79646 or 73% in real terms and the shape looks OK too.

Found this Rob
Yes ... I found much the same, the triple port was not much better than the single when they both had to suck through a 24mm carb but when a biger carb was simulated the tripple produced more power up top and significantly more drive down low.

If they are both limited to a 24mm carb and similar power curves, then a good reason for making a tripple port cylinder would be for mechanical reliability with the triples main ex port width at 62% of bore diameter instead of the singles 75%.

TZ350

10th April 2012, 19:08

Yes, well every one knows that blowdown is everything and more is better. So I had adapted an old cylinder I had already ported before to a triple port before I had the EngMod2T software and could see what was likely to happen.

The future could be another triple port cylinder with the std GP exhaust port width or a purpose made sleeve or better yet, cylinder.

In the end, because of the 24mm carb I may not get much more power but I can see that reliability could be greatly improved with a triple port setup. Including the hot exhaust gas down the transfers gremlin.

wobbly

10th April 2012, 19:19

Forget the homemade bullshit, get one of these with the extra wire to ground.
When it sees deto it can ground an Ignitech input and retard the timing automatically.
You get flashing lights and engine protection all in one shot, and cheap as chips - made in Czech so it likes being connected to an Ignitech - same lingo..
Works perfectly - when you get it trimmed correctly it will tell you where to manually pull out timing, then it just operates as a failsafe.

http://www.ebay.com/itm/Knock-gauge-for-detonation-sensor-klopfsensor-NEW-/110818862446?pt=Race_Car_Parts&hash=item19cd51a56e&vxp=mtr#ht_1582wt_1297

TZ350

10th April 2012, 19:23

Just brought one now. thanks.

Frits Overmars

10th April 2012, 21:04

....when the ring ends but together the ring would bulge out into the ex port.When the ring ends but together, the ring becomes a very efficient oil scraper and you will experience the mother of all seizures.

The cylinder that failed at Kaitoke is also 56.5mm and the exhaust port width is 41.76mm so 74% there too.
It may be the shape and radius of the ports are different enough to be making a real difference.Wob suggests 72% and Neels 73% so 74% is stepping over the line a bit.A 74% port width should not cause any ring problems. If it does, it will be because of radii being too small. With good quality piston rings you can get away with 80% port width. But that will not do your power any good; such a width requires huge port radii that will take away much blowdown area at the top corners of the por tas the picture below shows.
70% width is optimal in this respect. And like Neels says, pay attention to the bottom of the port window. Rings have more time to bulge into the port when the piston is on the way down. And you can apply large bottom radii because that will not take away any blowdown area.

bucketracer

10th April 2012, 22:02

A 74% port width should not cause any ring problems. If it does, it will be because of radii being too small.

That cylinder of TeeZee's was one recovered from a previous bad experience when a ring turned and got caught in the ex port. TeeZee is not one to waste anything. It was recovered by razing and enlarging the port to clean up the damage but it looks like that left the top and bottom edges a bit square.

As a prof of concept exercise I guess it has proved its point, low 30's hp Buckets are possible.

Just have to do it again with a better cylinder and ignition curve.

husaberg

10th April 2012, 22:19

When the ring ends but together, the ring becomes a very efficient oil scraper and you will experience the mother of all seizures.
A 74% port width should not cause any ring problems. If it does, it will be because of radii being too small. With good quality piston rings you can get away with 80% port width. But that will not do your power any good; such a width requires huge port radii that will take away much blowdown area at the top corners of the port.
70% width is optimal in this respect. And like Neels says, pay attention to the bottom of the port window. Rings have more time to bulge into the port when the piston is on the way down. And you can apply large bottom radii because that will not take away any blowdown area.

Hello Frits i may have got this a bit confused. With all this talk of exhaust ports i had a bit of a troll around while i was looking into aux exhaust ports and was looking at Kawasaki kips system (i had never actually noticed the aux port were in this system higher than the main port.)Having a aha moment i looked at your down loads of the Aprilia stuff to see the Aprilia system and i noticed this.
The Aprilia aux ports seem to be the same height (or possibly a little lower)as the top of the main port but the power valve seems to only control the height of the main port or does the edges of the blade in fact also control the aux ports entry to the main port. Is that how it works?
I also noticed the cylinder head on one of the 250 twins seem to have what i assume is the water exit at the bottom of the head pointing down.The 125 pics also seem to have the what i assume is the exit on the lower part of the head.(I are assuming of coarse the water flows to the crankcase the cylinder then on to the head. Is that not correct?)

Also did you miss the question a couple of pages back regarding the retarding of the disk valves or was it a silly question?

With the RSA being gear driven disk was there ever any consideration given to reversing the rotation to allow for a rudimentary retard function along the lines of a centrifugal advance ignition.
I ask because Bell quotes significant high rev gains from a mildly retarded opening and closing and visa versa (He even showed curves). So it would seem (if bell is right) the timings could be varied it could to allow for a broader output if timed for normal peak at full retard. Just a thought possibly retarded.;)
Oh with the pipe sealing if dykes rings were to be used inverted and back to front they would possibly take up little space and should also seal.

Frits Overmars

10th April 2012, 23:27

I never worked with the Kawa KMX125 you showed, but the twin cylinder 250 cc KR1S (lovely bike) had the same arrangment. A friend of mine raced one of those in a Dutch stock class against a fleet of 400 cc four cylinder fourstrokes. Being a stock class, there was not much we were allowed to modify in the little Kawa.
Fitting Yamaha TZ250G pistons (lighter, stronger, cheaper(!) and with 1 instead of 2 rings and 1 mm shorter from pin centre to top edge), raising the centre exhaust to the same height as the auxiliaries and milling the cylinder head made it faster than all the foulstrokes.
In the Aprilia cylinders (I assume you are talking about the racers; not the RS250 street bike with Suzuki engine) the blades (there are two of them, one on top of the other) only control the main exhaust port.
In the Aprilia racers there is always a route for air to get out of the cooling system. The coolant flow comes from the crankcase, enters the cylinder under the exhaust duct and exits via the head. In the bottom cylinder of the 250 cc V-twins the air can take the opposite route if need be. The RSA125 has a dedicated air bleed line at the back of the head (see pic).

I did not miss your question regarding the retarding of the disk valves, but I did'n answer it because A: it was not quite clear what you meant; B: it is one of those simple questions where the answer is not simple, and C: I could not spare the time to formulate a civilized reaction to your Bell-quote. Referring to it as Bell-shit as I have done in the past, would not be acceptible in a decent forum like this.

Let me summarize it like this: you can improve the power band by closing the disk early at low revs. But then you should also open it earlier because the transfer phase will be finished earlier at those revs and the rising piston will suck charge back from the cylinder to the crankcase if you do not open the disk as soon as crankcase pressure threatens to drop below atmospheric. So the best solution would be to rotate the whole disk. But what that has to do with reversing the rotation of the rear-driven RSA disk, or any other disk for that matter, is beyond me.

husaberg

10th April 2012, 23:36

I did not miss your question regarding the retarding of the disk valves, but I did'n answer it because A: it was not quite clear what you meant;, B: it is one of those simple questions where the answer is not simple, and C: I could not spare the time to formulate a civilized reaction to your Bell-quote. Referring to it as Bell-shit as I have done in the past, would not be acceptible in a decent forum like this.

Let me summarize it like this: you can improve the power band by closing the disk early at low revs. But then you should also open it earlier because the transfer phase will be finished earlier at those revs and the rising piston will suck charge back from the cylinder to the crankcase if you do not open the disk as soon as crankcase power threatens to drop below atmospheric. So the best solution would be to rotate the whole disk. But what that has to do with reversing the rotation of the rear-driven RSA disk, or any other disk for that matter, is beyond me.

Think of a centrifical advance on an old car or brit bike and quite a few old Japas they have a bob weight to advance the timming with speed
http://www.indiacar.com/doityourself/pictures/p12.jpg
the amount of advance can be controlled by both the strength of the springs and the weight of the bob weights.
If this were added to a disk valve engine . As the whole disk would seemingly need to retard with speed on a disk valve engine.
The rotation of the valve would therefor have to be reversed?
I hope that makes a little more sense?
Or is the Bell curves for the disk timing variations fundamentally wrong?
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=261771&stc=1&thumb=1&d=1333886008

dmcca

10th April 2012, 23:48

Just brought one now. thanks.

So did you get one with the analogue output? If so which option best suits the ignitech?

Frits Overmars

11th April 2012, 00:27

Think of a centrifical advance on an old car or brit bike and quite a few old Japas they have a bob weight to advance the timming with speed
http://www.indiacar.com/doityourself/pictures/p12.jpg
the amount of advance can be controlled by both the strength of the springs and the weight of the bob weights.
If this were added to a disk valve engine . As the whole disk would seemingly need to retard with speed on a disk valve engine.
The rotation of the valve would therefor have to be reversed? I hope that makes a little more sense?Not at all, Husa. How about keeping the direction of valve rotation intact (changing it in the RSA125 would be quite complicated) and mirroring the bob weight arrangement?
Centrifugal disk adjustment has been built before; the idea is not bad (I feel you might need a little comfort :hug:).

teriks

11th April 2012, 08:20

The future could be another triple port cylinder with the std GP exhaust port width or a purpose made sleeve or better yet, cylinder.
On the sleeved air-cooled part..
What if you'd cut the cylinder just above the export, and make an aluminum liner with a few cooling fins on the top part of the bore? -Should improve cooling somewhat.
(Man this Swenglish aint easy.. did that make sense at all?
Will try harder to find a picture somewhere..)
It' not a revolutionary idea at all, there has at least been a few model engines using such a design.

EDIT: Found something that at least give a hint of what I'm trying to describe:
261785 Source: http://lerner-modellbau.com/product_info.php?products_id=127&language=en
261786 Source: http://www.rc-network.de/forum/showthread.php/71801-30-Jahre-F3D-Rennen-in-Melnik
261836 Source: http://fiorimet.home.xs4all.nl/history.htm
You can also see the high temperature O-ring application I mentioned earlier.

wobbly

11th April 2012, 08:32

As I said before the knockgauge that works with the Ignitech has an analogue output to ground.
When it detects deto it grounds an Ignitech input that is programmed to retard.
You can watch the lights and then manually take out timing to stop the deto, but the retard circuit of the knockgauge/Ignitech pulls out the timing
so quickly you may well miss this indication.
So I disable the retard initially to see where the advance curve needs to be changed, then reconnect it.
In this case the gauge is a failsafe.

See the pic above of the RSA - the Bosch deto sensor with 8mm hole is bolted to a head stud - that Thiel character was /is no idiot.

Yow Ling

11th April 2012, 09:08

Bosch Vibration sensors

http://www.bosch.com.au/content/language1/html/4563.htm

Wobbly , what is the difference between 2 pole and 3 pole types?

Are these available anywhere local, I rang a Bosch distributor in Auck, I think they were giving me the 1000 yard stare on the phone

Leed

11th April 2012, 09:24

sorry just read an older posting and had a wee laugh...

"Torque is something you distill from power with the help of a gearbox"

:facepalm:

Power is the application of Torque (force) in a timeframe... so a gearbox simply reduces or magnitfies the force (torque)... Power is quanitified by Torque and Time
Power is a product not a factor... primary school

wobbly

11th April 2012, 09:59

The 3 pole ones have 3 wires so dont know how these would be connected.
Most are 2 wire and are common to most late model cars, Audi, VW ,BMW, Subi etc, the plug is standard injector type.
Easiest is the one with 8mm hole thru the middle, they are rugged as hell, so rarely bust, whip down to wrecker and get one for jack shit with the plug connected.

mike schmidt

11th April 2012, 11:29

We are working on a 175 cc twin (48 x 48) outboard. (Rossi) The performance is not up to where it was when tested in Italy. Is there a diffrence between a 48 mm bore piston and a 54 or 56 mm bore piston in how lean you can go based on plug color? The plugs looked perfect for a 125 or a 250 twin, but I am now thinking you may be able to lean the small bore motor down further.

Any coments?

Thanks

Mike Schmidt

Frits Overmars

11th April 2012, 11:33

sorry just read an older posting and had a wee laugh... "Torque is something you distill from power with the help of a gearbox"I could have written that. In fact, I think I did :msn-wink:.

Power is the application of Torque (force) in a timeframe... so a gearbox simply reduces or magnitfies the force (torque)... Power is quanitified by Torque and Time. Power is a product not a factor... primary schoolPrimary school or kindergarten? Power can be defined as torque*radians per second. Where did you hide the radians?
A more general definition is: power = force*distance per unit time. In short: power=force*velocity. Did you notice there is no torque at all in this definition?

wobbly

11th April 2012, 13:04

I dont know if Rossi's dyno reads high but no one else seems to get the numbers as done in Italy.
Plug colour would not change at all from a 54 down to a 48 bore, but maybe it is possible to run a little hotter on egt.
What are the cht and egt numbers - I recommend reading the egt at the end of the slider, where the pipe begins ,not up at the flange,as with so much overfueling going
on with Methanol the gauge will not read correctly.
You would have to be very careful leaning down as they then deto badly off the turns - I hear Rossi is now using a solenoid powerjet carb to try and fix this.

mike schmidt

11th April 2012, 13:43

Wobly: Thanks. Deep down inside I knew the answer, but was hoping....

We are grasping at straws on the 175 twin. It ran 10+ mph faster in Italy on a bigger boat. There are some very smart guys helping on this one and everyone is confused. Sereal years ago I invested a bunch of $$ in a duel EGT set up that records. I spent even more $$ on pistons that season. With the amount of methanol we dump into these things EGT is tricky at best. The 175 is running 140 F- 150 F CHT. The plugs are something I would consider dead on in our 250.

The owner went all through the fuel system, electrical system, the top end and obtained a known good set of 175 twin pipes. We are putting my older son in it, as he is is very good at giving feed back.

Note: Last year I built a set of cylinders for Rossi to test. Had some good ideas that I really thought would help his cylinders. Lost several H.P. on his dyno. I just came up from the shop where I am fixing them so they look (and hopefully work) like the Aprilla they were copied from. I sure wish that you and Fritz had shared this information a couple of years ago.

Thanks

Mike Schmidt

marsheng

11th April 2012, 14:05

husaberg

11th April 2012, 17:27

Not at all, Husa. How about keeping the direction of valve rotation intact (changing it in the RSA125 would be quite complicated) and mirroring the bob weight arrangement?
Centrifugal disk adjustment has been built before; the idea is not bad (I feel you might need a little comfort :hug:).

Thanks for the hug we all need a hug at times esp my signiture pic, but Frits I am afraid my Italian is worse than woefully non existent (ie its all... er Greek to me)
So to save me the pain of Translate via boobblefish or similar from the text.Did it work ok with any useful gains.I must say even with searches i have never came across anything remotely similar.
oh yeah mirrored bobweights cunning. Also was the curves (Bell) remotely close to what would actually happen?
but i guess no love on the inverted dykes rings for pipe sealing. I did think that would appeal to a Dutchman:yes:

Frits Overmars

11th April 2012, 21:35

Thanks for the hug we all need a hug at times esp my signiture pic, but Frits I am afraid my Italian is worse than woefully non existent (ie its all... er Greek to me). So to save me the pain of Translate via boobblefish or similar from the text.Did it work ok with any useful gains.I must say even with searches i have never came across anything remotely similar.
oh yeah mirrored bobweights cunning. Also was the curves (Bell) remotely close to what would actually happen?
but i guess no love on the inverted dykes rings for pipe sealing. I did think that would appeal to a Dutchman:yes:I have no information re how it worked, Husa. The article says it's great. But then it would, wouldn't it?
I cannot enlarge the Bell curves you posted. And I can't be bothered to dig up my copy of the Bell book either; it is usually a waste of time.
Finally I will have you know that I am not so much into dykes; I am more of a ladies man :love:.

husaberg

11th April 2012, 21:47

I have no information re how it worked, Husa. The article says it's great. But then it would, wouldn't it?
I cannot enlarge the Bell curves you posted. And I can't be bothered to dig up my copy of the Bell book either; it is usually a waste of time.
Finally I will have you know that I am not so much into dykes; I am more of a ladies man :love:.

Bell Curve as i have said before it is a shame there is no modern two stoke book:innocent:
That should work.(the attachment)

Frits Overmars

11th April 2012, 22:14

Bell Curve as i have said before it is a shame there is no modern two stoke book:innocent:
That should work.(the attachment)It did work. And here Bell is right, as far as the effect the altered disk timing would have on the power curve.
But the exhaust pipe decides how the power curve will look and the disk timing is only a minor player in this field.

husaberg

11th April 2012, 22:49

It did work. And here Bell is right, as far as the effect the altered disk timing would have on the power curve.
But the exhaust pipe decides how the power curve will look and the disk timing is only a minor player in this field.
so assuming it could be built reliably what sort of gains in drive-ability could be expected if you don't mind making an assumption 5% 10%( i realise it is a big ask) to hazard an assumption like that. Maybe someone with access to a sim could simulate it? anyone? Say based on a known simulation for a Suzuki gp125?
i guess any increase in spread of power would be more useful on a single speed kart though.

ok posted here as a wide reader base but please no arguments on rules here.put them here
debate is healthy
http://www.lgkstore.it/en/store/product/view/121/1504
to save clogging the thread.
legal or not ps not translated the site is as is. the wording could be construed as ambiguous i guess.Much like the rules.
http://http://www.lgkstore.it/en/store/product/view/121/1504 (http://www.lgkstore.it/en/store/product/view/121/1504)
http://www.lgkstore.it/components/com_jshopping/files/img_products/4926654e3d52235d5d3f77a97c0ac7e5.jpg
20mm with 113mm wheelbase conrod for 125cc (adaptable SGM) (Code: RKD 534 )
http://www.lgkstore.it/components/com_jshopping/files/img_products/33bb58a4f1f86e8e29b86ad902658b87.jpg
Double life - Complete 20mm crank pin high quality
High quality, ground and grappled, this type of axle supports up to 2 revisions
Complete round crack pin washer and lower roller bearing.
Provenance Moto GP
Price: 45.00 EUR

dinamik2t

12th April 2012, 05:29

ie its all... er Greek to me

Arrgh! :spanking:
The only resemblance between greek and italian (= latin -> even english partly came from latin) is the hugeness of the languages!
But latin is a dead language, so Ζητω τα Ελληνικα!

Yow Ling

12th April 2012, 06:06

wobbly

12th April 2012, 08:23

Here is a sim run from GP125 with 36mm carb.The 24mm carb high velocity and area reduction showed little difference with RV changes.
The stock timing for this setup was 140-88 a very normal racing engine duration spec.
I then symmetrically retarded the valve to 158-70.
Then after seeing the result of closing early only with a servo setup on an old BigHorn experiment,I symmetrically reduced the timing 10* each side to 130-70.
The sim showed the basic effects, but cannot show the proven issue that when opening any earlier than 140 the carburation becomes impossibly finicky to tune.
Thus the symmetrical retard I believe would have a small effect on the power spread - hamstrung by the bad carburation in the midrange.
But the symmetrical reduction of both sides of the port would have alot more positive effect, with better throttle response as well as an improvement from the retarded closing point.
This can be achieved with a setup like a pair of scissors oriented vertically, sweeping open and closed symmetrically across the port.

breezy

12th April 2012, 08:36

is it ok to post some of the comments/quotes and information from this site on another forum... i dont want to breach any rules or upset anyone, so thought it best to ask. thanks..

bucketracer

12th April 2012, 10:04

is it ok to post some of the comments/quotes and information from this site on another forum... i dont want to breach any rules or upset anyone, so thought it best to ask. thanks..

Maybe, the better idea is to post your comments with links on the other forum that link back to this thread, that way the source is acknowledged and people can checkout what you say for themselves, its the way TeeZee has been doing it since the beginning on this thread.

koba

12th April 2012, 10:06

Stumbled across this and thought about that pipe sealing issue.

http://www.crossmanufacturing.com/brush_seals.html

I guess they would be no good for with reciprocating motion but the ide is smart and got me thinking...

F5 Dave

12th April 2012, 10:28

so assuming it could be built reliably what sort of gains in drive-ability could be expected if you don't mind making an assumption 5% 10%( i realise it is a big ask) to hazard an assumption like that. Maybe someone with access to a sim could simulate it? anyone? Say based on a known simulation for a Suzuki gp125?
i guess any increase in spread of power would be more useful on a single speed kart though.

ok posted here as a wide reader base but please no arguments on rules here.put them here
to save clogging the thread.
legal or not ps not translated the site is as is. the wording could be construed as ambiguous i guess.Much like the rules.
http://http://www.lgkstore.it/en/store/product/view/121/1504 (http://www.lgkstore.it/en/store/product/view/121/1504)
http://www.lgkstore.it/components/com_jshopping/files/img_products/4926654e3d52235d5d3f77a97c0ac7e5.jpg
20mm with 113mm wheelbase conrod for 125cc (adaptable SGM) (Code: RKD 534 )
http://www.lgkstore.it/components/com_jshopping/files/img_products/33bb58a4f1f86e8e29b86ad902658b87.jpg
Double life - Complete 20mm crank pin high quality
High quality, ground and grappled, this type of axle supports up to 2 revisions
Complete round crack pin washer and lower roller bearing.
Provenance Moto GP
Price: 45.00 EUR
um, its says "Racing Kart"??
if you want a 20mm pin rod & can live with 110mm then RS125/AF1 Aprilia. Totally legal beagle. Someone told me they ran them in 256 Rotaxs as an upgrade (bigger pin etc). & suits 15mm piston pin or 14mm with a 14x19 bearing (which std MB is & you can get wider ones from Samarin).

TZ350

12th April 2012, 10:39

More news from Richard Maas. Did his trombone pipe give the desired results? O yes .... Only problem so far: the piece of pipe that is fixed to the cylinder, is shrouded by the pipe that slides over it, so it gets very hot. Too hot for the Viton O-ring that is taking care of sealing. Any bright ideas, anyone?

These are high pressure gas compressor segmented piston rod packing rings. They work a bit like a piston ring where the gas pressure helps them seal. Unlike a piston ring that expands out, these are squeezed in, the flat faces seal in the housing like the side of a piston ring does, when the gas pressure pushes it against the side of the ring grove.

They are usually used in an indexed stack (you can see the little locating dowels and alignment holes) so the gas does not easily pass through the segment cuts.

These ones are carbon filled Teflon but there are bronze ones and anyway if your making your own you can make them any size and from whatever material you like. To get a hole that's perfectly round and that has some crush on the shaft, you temporarily expand the segments with small keepers before boring them to size.

husaberg

12th April 2012, 17:22

Arrgh! :spanking:
The only resemblance between greek and italian (= latin -> even english partly came from latin) is the hugeness of the languages!
But latin is a dead language, so Ζητω τα Ελληνικα!

I er....was quoting Shakespeare, it was a mare play on words.http://en.wikipedia.org/wiki/Greek_to_me

um, its says "Racing Kart"??
if you want a 20mm pin rod & can live with 110mm then RS125/AF1 Aprilia. Totally legal beagle. Someone told me they ran them in 256 Rotaxs as an upgrade (bigger pin etc). & suits 15mm piston pin or 14mm with a 14x19 bearing (which std MB is & you can get wider ones from Samarin).
gee Dave follow the link of where to debate it would ya, it's in the original text.
ok posted here as a wide reader base but please no arguments on rules here.put them here
debate is healthy
to save clogging the thread.

Oh thanks Frits and Wob for your insights

ac3_snow

12th April 2012, 21:25

Well I had a brilliant weekend in Wellington over easter. My bike ran rather well, I think the issue I was having at high rpm may have been due to a lack luster method of exhaust mounting, a couple of extra springs seems to have worked a treat.

I only got to race in one of the points races on sunday, I managed to stuff it up attempting to ride around the outside of someone, ran out of track and got fixated on the grass. My crash bent the gear selector shaft which pushed the oil seal out of shape. Couldn't find a suitable peice of pipe to bend it back into shape so that was the end of my weekend racing.
However I had the time of my life, Kaitoke is a awesome!! track, AND I didn't suffer any '2 stroke' issues over the weekend, only a 'rider fuck up and crash' issue, which is inherrent with buckets so I am pretty happy.

Pulled my engine apart on tuesday as I wanted to check the bent shaft was the only damage and ensure I got it nice and straight. Also while its apart I am experimenting with the balance factor, trying to smooth out some of the vibration. Trying a balance factor of around 52% instead of he current 55% so have added about 10g of epoxy, will let you know how it affects the vibrations.

Snapped a pic of the marks on top of my piston while I was at it, any comments are much appreciated.

261902261903

koba

12th April 2012, 22:17

I managed to stuff it up attempting to ride around the outside of someone

The favourable camber drops away a lot more than it looks like as you get wide on that corner...

husaberg

14th April 2012, 13:39

Rods and stuff
http://dl.dropbox.com/u/399336/Pictures/Posted/HotRod.pdf
http://www.kingrod.com.tw/products.php?func=p_list&pc_parent=22
http://www.crankshaftparts.com/index.php?route=product/category&path=67_93&limit=100
http://shop.atlanticmotoplex.ca/productdetail.htm?productId=10295201&browse=256115&shopBy=13698&catalogId=2016
http://jjmachineryonline.com/snowmobile/crankshaft-rebuild-kits-and-parts/connecting-rods
http://www.scooter-center.com/scoweb...y2=CAT&lang=en
http://www.bansheedepot.com/products.asp?cat=17

Yow Ling

14th April 2012, 14:58

Rods and stuff
http://dl.dropbox.com/u/399336/Pictu...ted/HotRod.pdf
http://www.kingrod.com.tw/products.p...t&pc_parent=22 Looks like a tkrj rip off?
http://www.crankshaftparts.com/index...7_93&limit=100
http://www.scooter-center.com/scoweb...y2=CAT&lang=en
http://www.bansheedepot.com/products.asp?cat=17

only the last 2 links work

TZ350

14th April 2012, 16:48

P 480 Tec interesting posts from last ten pages ... each decade page 440 ... 450 ... 460 ... 470 ... etc has a collection of posts and links from the last ten pages so its easy to skip through the thread and pick up the tec bits.

And I'm pretty sure the length and diameter of that parallel pipe were optimized to the millimeter.
Every duct in an engine plays a gasdynamics role, whether you want it or not, so you better make use of it.

I thinks you should think again, rgvbaz. Pressure differential does not equal flow; it equals acceleration. If there is a lot of inertia in the mass flow (a long gas column and / or a high flow velocity) a negative pressure differential will spend a lot of time slowing that flow down to zero before you will see the first sign of flow reversal.

This is very interesting as you can see the steep drop off in the 31hp graph, and at Taupo after looking at the speed trap times and gearing, the bike was running at 13,000rpm up the back and for a good part of the front straight, well in the exhaust gas down the transfers region.

261086

The engine did not seize on full throttle running flat out, but after several down changes, when the throttle had been closed for a bit, maybe the cooling was marginal and when the cooling from the MJ fuel stoped, the engine stoped.

So what to do? an alloy sleeve with large tripple ports, not for power but for better thermal reliability ... http://www.kiwibiker.co.nz/forums/images/smilies/scratch.gif

Then don't close the throttle http://www.kiwibiker.co.nz/forums/images/smilies/biggrin.gif.
The old 100 cc kart engines with direct drive were notorious in that respect. They were air-cooled, iron-sleeved and they revved over 20,000 rpm. When you cut the power at those revs, chances were that the con rod would quit; it needed the help of the compression pressure to stop the piston from going through the roof. So you had to brake first and then cut the power.
Common practice was to put a hand against the carb bellmouth and blip the throttle occasionally during braking to get some fuel through the engine. But more than one rider forgot how close the chain was to the carb, and had to remove his right glove with a finger tip still in it...
My solution was to fit a brake light switch to the brake pedal and connect it to the ignition cut-out wire. Then you could keep both hands at the wheel, saving your fingers, and keep the throttle wide open during braking. I would not advise you to copy this 100%, but think about mounting a kill switch and using it....

And if the triple ports would raise the power by coincidence, you wouldn't object too loudly, would you?
But sleeve and thermal reliability are another set of words I would not use in the same sentence. OK, an alloy sleeve is better than a cast iron one, but there will always be a thermal barrier between sleeve and cylinder body. Even with the best shrink fit, oil will creep between the sleeve and the cylinder; that oil will char, and gone is your heat path.
Believe me, I know; you cannot come up with a single mistake I haven't already made decades ago (there is a fancy word for it: experience).
All in all, I guess the triple ports may outweigh the disadvantages of the sleeve. But couldn't you make the ports without using a sleeve?

Something to think about while the rest of the family occupy themselves with buying, boiling, painting, hiding, searching, finding and eating easter eggs: a couple of recent videos from the Dutch 50 cc scene.
http://www.youtube.com/watch?v=mvV4xbFKs0g&feature=relmfu
http://youtu.be/0odVzSgufjk

It was designed and built by Richard Maas http://www.adriaanmeeuwsen.nl/team-pagina.html. Hopefully we will see it in action next monday.
And if I were you, I would make it go shorter with rpm http://www.kiwibiker.co.nz/forums/images/smilies/whistling.gif.

More news from Richard Maas. Did his trombone pipe give the desired results? O yes. At 10,000 rpm it gives 4 HP more than the same engine with a fixed pipe. It runs over 17,000 rpm without the need for a powerjet and with a fixed ignition timing. It is miles better than an engine with an exhaust power valve. And the mapping of pipe length, ignition timing and powerjet pulse width has yet to be carried out. Maybe the powerjet can disappear altogether.
Only problem so far: the piece of pipe that is fixed to the cylinder, is shrouded by the pipe that slides over it, so it gets very hot. Too hot for the Viton O-ring that is taking care of sealing. Any bright ideas, anyone?

WTF ….. The Beast screams around the track on full song for a whole lot of laps then quits when taken out for an easy trot around in the two warm up laps for the next race, what is that all about?????

261714

Damage is in the exhaust port area, and thats a steel ring thats cleanly snapped in two.

I will dig out the dyno graph and ignition curve.

The text of an email I received from Neels van Niekerk and posted here with his permission.

261733

Hi Robert

I know it has nothing to do with me but if the engine that broke the ring this past weekend was running the attached export it is no wonder. My experiences with these size exports are the following:

1. Never exceed 41mm for your bore ( *** )
2. Use at least 10mm radius for top corners
3. Use 100mm top edge radius
4. use 12mm radius for bottom corners
5. Use 80mm radius for bottom edge

Exceeding these gave more power but lead to the following:
1. Unexplained seizures
2. Broken rings after cooling off at the end of a race - runs fine and wins race, refuses to restart
3. Pinched rings - from severe hammering of piston top edge
4. Broken ring land at export
5. Ring breaks at low speed - not sure why but I think it just have more time to bulge into the export

If the only way to be competitive is to run such a port:
1. Piston and ring life is max 50km
2. Bore must be perfect
3. Very good (rounded) chamfer of top and bottom edge

I really like reading your ESE thread - gives me good feedback about where to improve my software and it is great to see such an enthusiastic bunch.

Regards
Neels

*** 56mm was the bore size enterd into the simulator.

One small point is that in the area off the pipe, I have found that the engine will not make much if any more power, as shown by the dyno load it will pull, but by adding a heap more timing, it will for sure
operate much , much better on part throttle response, on track.
Here is a 125 kart engine curve that made 50RWHp,and won 3 back to back 125 National titles easily.

This thing would deto like mad on part throttle at 6000 if held there, but on track it would pull out of 1st gear hairpins hard enough to spin the tyres on full throttle from the same rpm, then rev out to 14200.

A TPS and a 3D map would achieve a better result, but I didnt have a RS125 Honda carb at the time.

I am wondering if this could be the problem? and I might need to use a TPS and go the 3D map way, or at least switch between 2 maps depending on rpm and throttle position.

The one and only reason you get a destroyed piston like that is DETONATION.

And looking at the Ignition curve you have posted it is immediately obvious why the thing keeps on blowing up.

These issues have nothing to do with an inherent problem with the 2T engine.

Thanks Wob, very informative and encouraging ....

get one of these with the extra wire to ground.
When it sees deto it can ground an Ignitech input and retard the timing automatically.
You get flashing lights and engine protection all in one shot, and cheap as chips - made in Czech so it likes being connected to an Ignitech - same lingo..
Works perfectly - when you get it trimmed correctly it will tell you where to manually pull out timing, then it just operates as a failsafe.

http://www.ebay.com/itm/Knock-gauge-for-detonation-sensor-klopfsensor-NEW-/110818862446?pt=Race_Car_Parts&hash=item19cd51a56e&vxp=mtr#ht_1582wt_1297

When the ring ends but together, the ring becomes a very efficient oil scraper and you will experience the mother of all seizures.

A 74% port width should not cause any ring problems. If it does, it will be because of radii being too small. With good quality piston rings you can get away with 80% port width. But that will not do your power any good; such a width requires huge port radii that will take away much blowdown area at the top corners of the por tas the picture below shows.
70% width is optimal in this respect. And like Neels says, pay attention to the bottom of the port window. Rings have more time to bulge into the port when the piston is on the way down. And you can apply large bottom radii because that will not take away any blowdown area.

you can improve the power band by closing the disk early at low revs. But then you should also open it earlier because the transfer phase will be finished earlier at those revs and the rising piston will suck charge back from the cylinder to the crankcase if you do not open the disk as soon as crankcase pressure threatens to drop below atmospheric. So the best solution would be to rotate the whole disk.

TZ350

14th April 2012, 21:16

261994261995261996

Posted because someone asked about them ....

Darcy Pipe specs:- http://homepage.mac.com/rg500delta/deltaphasetwo/linked%20files/pipes/DarcyPipeSpec.txt

Yow Ling

15th April 2012, 16:07

Would be good if we could dream up a way to use these old RZ 250 barrels in buckets 54x54 pv watercooled , reed valve, one of them has a factory boysen port

262021

husaberg

15th April 2012, 17:28

Would be good if we could dream up a way to use these old RZ 250 barrels in buckets 54x54 pv watercooled , reed valve, one of them has a factory boysen port

262021

Strap 4 or better still 5 of them together and make a sidecar engine.
As far as i know there is no rules discriminating against home build 2 strokes in the sidecars.
http://25.media.tumblr.com/tumblr_lk0cjf9OHH1qz5o8qo1_500.jpghttp://flash412pix2.home.comcast.net/Yam-V8-B.JPG

Sorry I can't find a picture of the Bill and Bob speedway one.

Kickaha

15th April 2012, 17:34

Strap 4 or better still 5 of them together and make a sidecar engine.
We could use 10 of them, we're allowed 1300cc two strokes in sidecars, fuck knows where all the exhausts would go though

husaberg

15th April 2012, 18:01

We could use 10 of them, we're allowed 1300cc two strokes in sidecars, fuck knows where all the exhausts would go though
I was meaning the engines but a quick add up reveals he has enough cylinders so he could build 2 of them.TEN cylinder engines.
F the pipes routing problems think of the noise.
They built that v4 Cr500 in CHCH didn't they. So a V10 should be a doddle:innocent:

http://www.youtube.com/watch?v=Ceeyrmn2Pj4&feature=fvw

F5 Dave

15th April 2012, 18:36

Rob, with the RG50 what you've done with the cage is much like an RM or RG250 tending to flat (mine may be slightly flatter) & I filled in the area between the back of the barrel & block with Devcon. I don't think the flow to the rear transfers will achieve much.

TZ350

15th April 2012, 20:44

I don't think the flow to the rear transfers will achieve much.

Yes, not to sure about them myself, I intended modifying the cases to match, sort of a Boyson port thing.

dmcca

15th April 2012, 21:04

Im getting an error message in Engmod2T that i havent seen before... SINGULARITY - INFLOW SUBSONIC

Any ides what it means? It reoccurred at every rpm point throuhgout the sim. Ive emailed Neels but thought id post up here also just to keep the engmod info flowing

husaberg

15th April 2012, 22:17

I came upon this today.

Slippy exhaust pipes
Why they're so difficult to pull, and how to fix it...
There has recently been a thread on the Mailing List in regards to the amount of effort required to "pull" the typical slippy (adjustable) exhaust pipe that is common in many road racing classes.
Well... A bit over 20 years ago, I had the same frustration, and I'll explain what I found, and how I solved the problem.
The image below show's an approximation of a "typical" slippy exhaust pipe. I have not shown the outlet hole in the "can"... (and a number of other things are missing as well), but this will serve the purpose for now. The moveable rear (convergent) cone is shown in its "out" position by the blue lines... and in it's fully "in" position by the green lines. The thick magenta line is a rough representation of the cable which pulls the rear cone/stinger assembly.
http://www.muller.net/mullermachine/docs/exhaust1.gif
OK... here's the problem in a nutshell: The amount of effort required to "pull" the rear cone is directly proportional to the difference in pressure between the front and back sides of the moveable cone. (There's some other minor things like friction, but they're insignificant compared to the pressure differential).
Since the the rear cone (at its big end) does not fit the large center section perfectly, some "pressure" leaks by the outside of the cone into the area behind the cone. If the outer rear cone (the one that supports the stinger) has too much clearance on the stinger (where I wrote "Here's the problem"), then the pressure behind the rear cone can "bleed" into the can (which has lower pressure than the inside of the exhaust pipe). This results in a pressure differential between the front (engine) side of the rear cone, and the back side.
THAT is what you are pulling "against" when you try to pull in your slippy pipe.

Now here's how I fixed the problem...
Years ago, Hartman Engineering made some very nice spun "outer" rear cones especially for slippy pipes. I started with one of those. They were made with a very large hole on the small end. (Oh... the other thing that was really nice about those Hartman cones is that they were very short. This allowed you to get the weld to the center section a long ways away from where the adjustable cone would be sliding.... which made it easier to keep the center section nice and round).
I made an insert for the small end of this cone (shown in red in the drawing below). This "insert" had a bit of a "bell-mouthed" shape to the inside diameter. I did this so that I could run a very tight fit to the stinger, without the stinger "binding" due to any misalignment that might exist. I also took the stinger material (before welding it to the cone) and had it hard-chromed, and then ground the outside diameter. This made it perfectly straight and round, as well as giving me a super fine finish that would resist any sort of galling or seizing. I gave the insert about .005 clearance on the stinger (as I recall).
How did it work?
Too well. At the time I was running Open class. Due to the power, Open engines were notorious for being almost impossible to pull the exhaust pipe for the full race (an hour long at the time). My first time on the track with this pipe was a complete surprise. The very first left-hand sweeper I went through, the rear cone went all the way in by itself, just from cornering force! The pipe was actually far too easy to pull. My solution was to experiment with "vent" holes into the can. With the clearance that I had given the stinger in my "support sleeve"... as well as the fit of the large end of the cone in the center section of the pipe... I ended up running a 3/16" diameter "bleed hole" from the outer rear cone (the short steep one in the drawing below) into the can. This gave just about the perfect "feel" in my case. I could operate the pipe handle with one finger... yet there was enough pressure on the cone to move it back out fairly quickly when I let go of the handle.
http://www.muller.net/mullermachine/docs/exhaust2.gif
You may not care to build your own slippy pipe... and we're seeing less and less classes where slippys are allowed... but hopefully this might help some of you that still run them.
Just remember: the effort required to pull the rear cone is directly related to the pressure differential on the front and back sides of the moveable cone. Anything you can do to prevent leakage around the stinger and into the can will make the pipe easier to operate... up to the point (I discovered) where it's too easy.

TZ350

15th April 2012, 22:42

Thats interesting. After looking at the trombone pipe I was wondering how the very long variable header fitted in with the requirements of keeping the header and diffuser within certain % limits of the pipes tuned length but combined with the slippery it might be possible.

Frits Overmars

16th April 2012, 00:14

There are several options in lengthening a pipe. You can move the end cone, like on the above drawing, or you can lengthen the header, like on the trombone pipe.
The gas pressure generates a force that is proportional to the cross section area of the moving part and proportional to the pressure difference at either side of that area. For a moving end cone this force can be up to 4 times larger than for a sliding header. That is one reason to go for the trombone system rather than the moving cone system.

The second reason: say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.
But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will result in lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum, but that is not feasible.
Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strenght through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

TZ350

16th April 2012, 12:25

... weakening the mixture strength through closing a power jet, has the disadvantage that not all inhaled air is used for combustion.

I thought that closing the power jet after peak power only restored the proper air fuel ratio? And the over rev was extended because the exhaust gas was not being cooled by an over rich mixture.

... It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum ...

I guess that's what happens when water injection changes the temperature of the exhaust gas, water injection looks like it would be a good idea if it was practical and didnt have any down sides.

... say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.

But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will result in lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

I have simulated the Slippery pipe in EngMod2T before and was not that encouraged by the results but your explanation of the Trombone looks interesting and I will try that in EngMod now.

Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length.
... And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strength through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

More good old engineering and design compromises to play with.

But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.

Do I understand this correctly, given sufficient blow down and exhaust STA an exhaust duration of 180 deg would be the optimum at any rpm?

Thanks Frits ..... gives me a bit more to think about.

husaberg

16th April 2012, 20:45

Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strenght through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

Do I understand this correctly, given sufficient blow down and exhaust STA an exhaust duration of 180 deg would be the optimum at any rpm?

Thanks Frits ..... gives me a bit more to think about.

Interesting i was assuming that Frits meant an exhaust valve that varied the effective height of the port?

Follow up question sorry.

In the Aprilia cylinders (I assume you are talking about the racers; not the RS250 street bike with Suzuki engine) the blades (there are two of them, one on top of the other) only control the main exhaust port.

Yes i was meaning the blades on the Aprilia race bike.
What i was meaning was the blades seemed very thick in profile. So i was just wondering if they also controled the exit of the AUX EX ports.
I was also wondering if anyone other than Kawasaki with the KIPS z(The AUX being higher than mainport) had tried this as it would seem if the blade was shaped similar profile to bellow it may be able to control the AUX ports as well so if they they (the AUX EX Ports) were positioned higher than the mainport EX port without seamingly hampering low down power.

http://www.dootalk.com/reports/images/TS_Sep08_05.jpg
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=262129&stc=1&thumb=1&d=1334572289
The profile is a top view looking down.

trevor amos

16th April 2012, 20:58

speedpro

16th April 2012, 21:41

The slippery pipe style of thing made by Peter Steadman had a closed end on the cone and the exhaust outlet was from the side of the centre section. As far as I'm aware he had a push-pull system to move a completely internal rear cone back and forth. He didn't perservere with it but I'm not sure why.

dmcca

16th April 2012, 22:37

Dmcca ,
I have the exactly same problem , thought i`d done something real stupid , not being the smartest computer user on the planet , and have tried to
correct it ? I intended to email Neels to seek advice , however , if you could post his solution i might not have to bother him , again . He must get
exasperated continually rescuing dummies like me !

Gratefull thanks if you are able to help ! Trevor

Ive heard back from Neels and sent him a couple of files he requested... Im sure he'll get back to me whenever he has something. Im thinking its user error as this particular project was causing problems from the beginning just trying to accurately model the exhaust and inlet port... the numbers that i thought should be correct caused other errors before this latest one and i had to keep manipulating them to get the sim to run. Havent had that before on any other project.

and dont worry i feel bad emailing him with issues too, but if you dont ask you'll never learn!

dinamik2t

16th April 2012, 23:11

I believe this problem has to do with "open ends" in the lines that form port shapes.
In an aux exhaust port for example: if I input a radius of 1mm and the vertical and horizontal line cannot be connected with that radius value, then there is a shape where radius line either is above vertical/horizontal lines or too far from them to create a 'closed shape'.
Both cases create a discrepancy, as Dat2t says, that seem to cause the inflown/subsonic error in the simulation process.

The same thing can happen in the combustion chamber CADing and it seems to happen in inlet/exhaust pipe modeling too - but I don't know why there.

As Wob said in the past, since EngMod utilises ports shapes to calculate time-area only, there is not problem to shape a port of the same area with different sizes/radiuses. In reality you can then apply the correct radiuses.

I guess it's something logical since a computer cannot handle everything with human logic. A radius of 3mm has a fixed shape and it cannot connect two orthogonal lines that are not properly coordinated to each other, to be connected with that radius.
As for the pipe modeling, sometimes it helps to re-compose and re-save a model - or re-start the computer.

Frits Overmars

16th April 2012, 23:21

....Yes i was meaning the blades on the Aprilia race bike... I was just wondering if they also controled the exit of the AUX EX ports. I was also wondering if anyone other than Kawasaki with the KIPS had tried thisKawasaki was by no means the only one to control the auxiliaries as well as the main exhaust with a power valve. Jan Thiel and yours truly incorporated it in the 1992 Rumi GP125; Maxter uses it on their KF125 kart engine, KTM has it on their MX-engines and no doubt there will be others.

Frits Overmars

17th April 2012, 01:09

Do I understand this correctly, given sufficient blow down and exhaust STA an exhaust duration of 180 deg would be the optimum at any rpm?The short answer is yes. But why is it that each time you people sit down for five minutes to write a question, I have to sit down for two hours to write an answer?:msn-wink:

When the exhaust port opens, a pressure pulse starts moving through the exhaust pipe. It is reflected at the end cone and it should be back at the cylinder just before the exhaust port closes.
Next a part of this reflected pulse bounces off the partly-closed exhaust port and a residual pulse starts moving down the exhaust pipe. This residual pulse too is reflected by the end cone and starts moving back to the cylinder. Ideally it will arrive at the exhaust port just when the port opens again. Then the cylinder pressure and the pressure of the residual pulse combine their energy and the resulting pulse will be stronger than the pulse from the previous cycle. And the combined pulse from the next cycle will be stronger still, and so on; we have achieved true resonance.

Some may argue that we want a low pressure in the exhaust pipe when the port opens because then the spent gases will experience less resistance while leaving the cylinder. But that is not true. Gas flow depends on a pressure difference ratio. But once that ratio reaches 2, the flow velocity will reach Mach 1, the speed of sound. Raising the pressure difference any further will not raise the flow velocity any further.
The cylinder pressure at exhaust opening can be as high as 7 bar and the pressure of the reflected pulse will be about 2 bar. Thus the pressure ratio is well above 2, so lowering the pressure in the exhaust duct outside the cylinder will not do any good to the flow.

What has the exhaust timing got to do with the 'true resonance' I mentioned above?
The initial pulse starts moving at Exhaust Opening and it has to be back at Exhaust Closing, or a little earlier. This pulse travels with the speed of sound and its journey up and down the exhaust pipe will take t seconds.
The residual pulse starts moving at Exhaust Closing and it has to be back at the next Exhaust Opening. This pulse also travels with the speed of sound and its journey up and down the exhaust pipe will also take t seconds.
So from EO to EC takes t seconds and from EC to EO also takes t seconds. In English: the exhaust port should be open just as long as it should be closed.
Assuming that the crankshaft rotates with a uniform speed, this means that the crank angle during which the exhaust is open must be equal to the crank angle during which the port is closed. So both angles must be 180°.

I developed this line of thought some 40 years ago, but when I first published it in 1978 (in the motorcycle magazine Moto73 of which I was the technical editor) everybody called me crazy. Some people still do, but I got used to it :p.

Above I made a couple of assumptions. The crankshaft does not rotate with a uniform speed, but at high revs the deviation is negligible. In case you really want to know, I did the math for the Aprilia RSA125. At a nominal rpm of 13,000 the minimum rotation speed is 12970 rpm @ 107° after TDC and the maximum value is 13031 rpm @ 356° aTDC. What's more significant: the deviation in crankshaft position from truly uniform rotation is always less than 1°. So that really is negligible.

Second assumption: both the initial pulse and the residual pulse move with the speed of sound. Not true: the pulse pressures in exhaust waves are so high that acoustics rules do not apply any more. We are dealing with gas dynamics here and the stronger a pulse, the faster it moves. Since the residual pulse is weaker than the initial pulse, they move at different speeds. But we will leave this aside for now.

Third assumption: the initial pulse starts moving as soon as the exhaust port starts opening. More or less true, but we are not interested in the first weak appearance of the pulse; we want to know when the pulse reaches its maximum amplitude. And that requires a certain amount of open exhaust port area. It turns out that for our desired theoretical exhaust timing of 180° we will need a geometrical exhaust timing of about 190°, depending on the shape of the port: does it open gradually or does it open over its full width all at once.

The obvious question will be: why has the Aprilia RSA125 a geometrical exhaust timing of about 200°? True, at 190° the maximum torque value would be higher, but the engine would not want to rev because the blowdown time.area would be too small.
The 200° are a compromise: a bit less torque and a bit more revs; as long as the torque decline is smaller than the rpm rise, we gain horsepower.

trevor amos

17th April 2012, 01:46

Hi Frits ,
From our perspective thats an easy one , we don`t know enough to ask long questions , but you know so much , a short answer is`nt
enough , that makes us very lucky indeed !

Regards , Trevor

Frits Overmars

17th April 2012, 01:59

Hi Frits , From our perspective thats an easy one , we don`t know enough to ask long questions , but you know so much , a short answer is`nt enough , that makes us very lucky indeed !Thanks for the flowers, Trevor. I prefer short questions anyway. Well, the next couple of weeks I will go walkabout in Germany, so I may be absent here for a while.

TZ350

17th April 2012, 06:42

Thanks Frits for your answer about the 180 deg port duration.

262139

Here is a simulation of the Trombone effect. Datum is at 14500 and it went -30mm and extended +45mm, for a total slide movement of 75mm. Seems to be more more of an effect at peak power than at the lower revs.

Its a very interesting idea, being able to extend the power peak like that .... now what could I do with that :scratch:

Frits Overmars

17th April 2012, 07:07

.....Here is a simulation of the Trombone effect. Datum is at 14500 and it went -30mm and extended +45mm, for a total slide movement of 75mm. Seems to be more more of an effect at peak power than at the lower revs.That Dutch trombone pipe moved from +70 mm length to -20 mm length, so its effect was concentrated on the lower revs (although raising max.rpm from 14,500 to over 17,000 rpm was a welcome bonus).

husaberg

17th April 2012, 07:29

The short answer is yes. But why is it that each time you people sit down for five minutes to write a question, :msn-wink:

“The important thing is to not stop questioning. Curiosity has its own reason for existing.”

“Only the one who does not question is safe from making a mistake.”

“Wisdom is not a product of schooling but of the lifelong attempt to acquire it.”

wobbly

17th April 2012, 08:01

The tech term for what Frits is describing is Superposition of the Ex pulse.
This is easily described in a sim, where a residual pressure ratio is seen sitting at the Ex port when it is opening.
The "new " pulse is added to this residual, and a very large pressure ratio exits down the duct to the header.
The larger the initial ratio, the larger the amplitude of the wave in the diffuser - this creates a deeper depression around BDC, and it is this that initiates the biggest mass flow
from the transfers.
The lower Ex timings of 190 and below create larger residual pressure ratios,over a wider band, and thus these work with a good pipe design to use "resonance" to increase band width and also peak power.
Big problem though is this whole concept is at odds with maximising blowdown to allow good peak power and more importantly, overev power.

The sim shows RGV100 making serious power with the superposition pulse going down the duct - off the scale.

Re the trombone pipe results you did sims for TeeZee.
Look carefully when you say it seems to affect the top end "more ".
At 9000 the lowest reading is 13 Hp, the highest reading is 17 Hp, thats an increase of 4 Hp, thats 31% more power in the bottom end, that then allows the thing to rev to 17,000.
Seems a not bad result.

Re the powerjet temp result you mentioned.
The effect of the solenoid powerjet is as you described - this I only discovered recently with a datalogger that I could set the sample rate of the EGT high enough to read the temps quick enough - along
with some exposed junction probes.
I was testing a RS125 on the dyno and it was making NO power past 12500, looking at the data you could see the egt drop from 640 C to 580 in around 400 rpm.
After fixing the fact some idiot had left out the rpm plug in the loom, the solenoid now switched on at 12200, and the temp stabilised at 650 past 12500 and the thing than reved out to 13500 +.
So the powerjet switching isnt making the mixture "lean"as such, it is simply maintaining the correct mixture, and thus the temp in the pipe.