ESE's works engine tuner

[ken seeber]

Want more transfer port area? Just raise them so they are as high as the EO. No (not really) back flow cos they are timed with matching holes in the piston skirt and cyl wall to prevent flow to the crankcase. Obviously it will exhibit exh (combusted) flow into the passage and also obviously it could be done in conjunction with lower “conventional” timed transfers. The idea was shown to me by a dude called Arthur around 20 + years. 10 ms on EngMod might show that it be of any value, but there it is.

334737334738

[lodgernz]

I'd appreciate some more advice about exhaust ducts please.

My 50 has an exhaust port window area of about 500mm2. The exhaust duct is only about 40mm long. If I extend the duct to twice the bore, i.e. 78mm, and steadily reduce the CSA of the duct so that the outer end is 90% of the port area (assuming I can even achieve this), then the total volume of the duct would only be about 38cc. Does this sound too small for a 50?

I realise it's impossible to predict the volume of the washed-through mixture, but I'd like to know if this sounds to be in the ball-park or not.

[Pursang]

Not sure if I understand the question, as I can't imagine why anyone would want to do this.

If you take a conventional two stroke, but move the exhaust ports up to near the top of cylinder, then when exhaust ports close just before TDC most of the mixture will have been pushed into the exhaust pipe. Compression would be very low, so very easy to kick over, if it fires expect flame exiting the exhaust pipe. Power would be very low.

Well that's what I think, anyone else have any thoughts on this?

Even a 3mm by-pass hole someway between EPC & TDC will dramatically reduce the static compression. Common mod on 350 Bultaco Alpinas, Way back when.
Little detectable power loss under normal operating conditions.

[Pursang]

Want more transfer port area? Just raise them so they are as high as the EO. No (not really) back flow cos they are timed with matching holes in the piston skirt and cyl wall to prevent flow to the crankcase. Obviously it will exhibit exh (combusted) flow into the passage and also obviously it could be done in conjunction with lower “conventional” timed transfers. The idea was shown to me by a dude called Arthur around 20 + years. 10 ms on EngMod might show that it be of any value, but there it is.

334737334738

Read a report , years ago, of a 1950's racer who got to ride, race & win on Walsh Bantams. He towed one home, after a meeting, with the exhaust pipe removed. He and his mate spent a lot of time looking up the exhaust duct (they weren't game to pull the head off). The piston skirt was 'Full of Holes'. He tried to reproduce the same with his own Bantam. It ran, but was Very peaky and pretty powerless. He suspected it was probably "free porting" out the exhaust. The Walsh Bantams, on the other hand, were capable of running with contemporary 500cc racing 4 strokes.

https://s3.amazonaws.com/WEBPOSTS/KIWI+ESE/f026c4.jpg
My Favorite vintage racing pic.

cheers, Daryl.

[Frits Overmars]

Does anyone have any experience with the Aprilia Ditech SR50 scooters? I'd like to use the fuel injection system on it but don't know if I can modify it to workAprilia has a lot of experience with their DiTech system, namely that it shouldn't have been put on the market so soon. There were so many problems that it almost did Aprilia in. In fact it did, because it rendered Aprilia insolvent (it coincided with a helmet-law for scooter riders that was introduced around the same time, which caused a collapse of the Italian scooter market, and with the acquision by Aprilia of the old Guzzi works that turned out to be almost worthless).
Aprilia was then swallowed up by its biggest creditor, Piaggio, snapping it from the jaws of also-interested Ducati, which incidentally was taken over shortly afterwards by Audi. We are still awaiting all-wheel-drive Ducatis.
OK, back to the business at hand:
the Ditech system may be suitable, but it'll take a lot of work, sweat and tears. And in any case it will be reluctant to rev because of the inertia of the air-valve.
334749 334750 334751 334752


What to expect with the Sub/Auxiliary Exhaust Ports opening at TDC (approximately 3mm on a 76mm stroke)? Main Exhaust open at TDC (1mm-2mm on a 76mm stroke) ?
If you take a conventional two stroke, but move the exhaust ports up to near the top of cylinder, then when exhaust ports close just before TDC most of the mixture will have been pushed into the exhaust pipe. Compression would be very low, so very easy to kick over, if it fires expect flame exiting the exhaust pipe. Power would be very low.Tjbw, DoldGuy is not talking about very high exhaust ports but about ports with very low bottoms that are opened near TDC by the underside of the piston skirt.


My 50 has an exhaust port window area of about 500mm2. The exhaust duct is only about 40mm long. If I extend the duct to twice the bore, i.e. 78mm, and steadily reduce the CSA of the duct so that the outer end is 90% of the port area (assuming I can even achieve this), then the total volume of the duct would only be about 38cc. Does this sound too small for a 50? I realise it's impossible to predict the volume of the washed-through mixture, but I'd like to know if this sounds to be in the ball-park or not.Ball-park :niceone:.
If you can persuade your exhaust pipe to shove 38cc of washed-through fresh mixture back into the cylinder before the exhaust closes, you'll have a winner.
Of course even the washed-through mixure will not be 100% pure, but a long, narrow exhaust duct helps in this respect; it will provide for a small-area contact plane between the spent and the fresh gases. But while mixing is limited, the long, narrow tract offers an unfavourable ratio between duct volume and duct wall surface, thus increasing the heat transfer from the walls to the mixture.

[peewee]

frits i think you confused me for tjbw. but i do have alittle experience with exh ports opening under the piston at tdc. some old ktm were like that and i happen to have one of them engineering marvels :lol:. whether it was a bungled design or ktm was aware and just didnt care, im not sure. im not even sure how big of a deal it is. maybe at tdc the crakcase and pipe pressures are near the same so no mingling of fresh mix and exh gas takes place, i just dont know. since i dont know, i used different piston to keep exh ports closed at tdc

[Niels Abildgaard]

the old Guzzi works that turned out to be almost worthless).
Aprilia was then swallowed up by its biggest creditor, Piaggio, snapping it from the jaws of also-interested Ducati, which incidentally was taken over shortly afterwards by Audi.


Can we have the story why V2 Guzzis were worthless and V2 Ducatis are not?

[jonny quest]

Frits, the little I understand of the ditech 2001, it has a cam ground on the crank which times, and actuates an air pump. This air pump provides pressurized air to an already fuel pressurized direct injection system. It has a throttle body and tps, which just allows air into motor via case reed. Direct high pressure air and fuel is injected into cylinder head.

Is it water temp, baro pressure controlled also?

Apparently they run safely with a non original pipe and bumped up to 70cc.

[Muhr]

Is adjusting a little in the crankcase and a reflection I had regarding C transfers case meeting. Below I have two different options, have someone tested this or have any thoughts on it. (on side fed rotary valv)

Regards Muhr

[breezy]

Read a report , years ago, of a 1950's racer who got to ride, race & win on Walsh Bantams. He towed one home, after a meeting, with the exhaust pipe removed. He and his mate spent a lot of time looking up the exhaust duct (they weren't game to pull the head off). The piston skirt was 'Full of Holes'. He tried to reproduce the same with his own Bantam. It ran, but was Very peaky and pretty powerless. He suspected it was probably "free porting" out the exhaust. The Walsh Bantams, on the other hand, were capable of running with contemporary 500cc racing 4 strokes.

https://s3.amazonaws.com/WEBPOSTS/KIWI+ESE/f026c4.jpg
My Favorite vintage racing pic.

cheers, Daryl.

i wonder if maybe the holes were for extra lubrication ... i have plenty of experience with piston siezure in cast barrels!!! any extra lubrication is a very welcome.

[peewee]

how much nitro will a dirtbike tolerate :eek:. the answer is easy. atleast 20% but how much more I just don't know . theres only one way to find out though. with just two or three more months of winter left I been getting ready for the riding season again. already I lowered the com ratio down to 12.5 and did some more carb work. ill make a new alumi fuel tank and ditch the fuel pump for a gravity system I think

[Flettner]

how much nitro will a dirtbike tolerate :eek:. the answer is easy. atleast 20% but how much more I just don't know . theres only one way to find out though. with just two or three more months of winter left I been getting ready for the riding season again. already I lowered the com ratio down to 12.5 and did some more carb work. ill make a new alumi fuel tank and ditch the fuel pump for a gravity system I think

If some is good then more must be better!

[peewee]

yes indeed. i probly wont go back to straight methanol. what i wish i had a fancy ign that could be programmed in the field or programed at home to hold a bunch maps in storage then test all of them .

[Frits Overmars]

frits i think you confused me for tjbw.Yes I did. Sorry about that Peewee.


the acquision by Aprilia of the old Guzzi works that turned out to be almost worthless
Can we have the story why V2 Guzzis were worthless and V2 Ducatis are not?No you can't, because that is not what I said Niels. I mentioned the almost worthless Guzzi works. Aprilia had hoped to be able to produce some of their models in the old Guzzi factory in Mandello, but the production facilities there turned out to be too old-fashioned to be of much value.
You might think, as did I, that it would have been easy enough to go over there and take a look at the available equipment before signing a contract, but apparently other factors played a role. Whenever money is wasted, there are always some people taking advantage of the situation. In Italy it has become an art...
Jan Thiel could tell us a story or two about Piovaticci, Minarelli, Garelli, Fantic, Sanvenero, Gilera, Rumi, and indeed Aprilia, and I witnessed more than one manager driving his Ferrari or Lamborghini away from the mess he left behind.

[mx2stroker]

Hello folks, I believe some here can help me to find who sell Rotary Valve parts to Aprilia GP 125 engine ?

Like the disc, intake manifold, Rotary Shaft Assembly etc.

Gold if someone could give me a tip.

Regards: Andy

http://www.bilddump.se/bilder/20180114125744-178.174.166.211.jpg

[Michael Moore]

Walsh land speed racer Bantam

http://bikeweb.com/files/images/WalshBantamLSR.jpg

[breezy]

Frits/wobby, if it were possible to maintain a higher pressure in the transfer ports on the 2 stroke engine greater than or equal to the pressure in the cylinder after combustion as the piston descends and the exhaust opens, would this not allow us to place transfer port widows into the cylinder at the same hight as the exhaust port or even higher?

[Magnus676]

Hey guys,I've got a question regarding exhaust length for a drag bike.
I think a drag bike will work better with a shorter pipe in general.
My reasoning for this,is that a drag bike is only running for 1-2 min total,so the temperature will be lower than a road race bike.
Do any of you guys have build a pipe for a drag engine?
PS: Do you guys know a decent shop that does dynamic balancing?I want to balance my crank,but I want the shop to be in Europe if possible.

[Muhr]

Hey guys,I've got a question regarding exhaust length for a drag bike.
I think a drag bike will work better with a shorter pipe in general.
My reasoning for this,is that a drag bike is only running for 1-2 min total,so the temperature will be lower than a road race bike.
Do any of you guys have build a pipe for a drag engine?
PS: Do you guys know a decent shop that does dynamic balancing?I want to balance my crank,but I want the shop to be in Europe if possible.

Build a pipe for the EGT and RPM as you wish, try to use as thin sheet as you can and protect the header from the wind. Frits has posted a great crib sheet name FOS he has done.
Why dynamic balancing?

[F5 Dave]

Surely for dynamic balancing to be of benefit then all the parameters need to be considered. So it should be done fully assembled, running, and mounted in the frame it will be used in.

I think we can see where I'm going with this. . .

[RomeuPT]

A chunk of SS in the port might be a good thing.....or a disaster.
SS has thermal conductivity around half of steel and perhaps a 10th of cast alum.

Maybe it will absorb less heat during the exhaust flow and transfer less to the 'flow through' charge. (Win/Win):woohoo:

Or....It might just heat up and up and transfer huge quantities of heat to the new charge (Lose/Deto/Lose):bash:
Far too many factors to consider just at the moment.

The reference to the vacuum flask is for a purpose.
There are 3 factors to be combined for a Thermos to work, miss out on any one and all you have is a bottle.:drinkup:

Shiny surface to reflect heat transfer by radiation. (Like Wobbly's piston crowns).
Vacuum (or air) gaps to prevent transfer by convection. (or bubbles in foam or some ceramics)
Long, thin, pathways and materials to reduce conduction, (SS better than steel and alum. not as good as glass & some ceramics)

Do some experiments and report what happens. Might be the next 'Big Thing' in 2T technology. :corn:

Cheers, Daryl.

334782334783

Bike is off for the winter, no conclusion yet, before the spignot had been in thin mildsteel welded to the exhaust

[Niels Abildgaard]

Yes I did. Sorry about that Peewee.

No you can't, because that is not what I said Niels. I mentioned the almost worthless Guzzi works. Aprilia had hoped to be able to produce some of their models in the old Guzzi factory in Mandello, but the production facilities there turned out to be too old-fashioned to be of much value.
You might think, as did I, that it would have been easy enough to go over there and take a look at the available equipment before signing a contract, but apparently other factors played a role. Whenever money is wasted, there are always some people taking advantage of the situation. In Italy it has become an art...
Jan Thiel could tell us a story or two about Piovaticci, Minarelli, Garelli, Fantic, Sanvenero, Gilera, Rumi, and indeed Aprilia, and I witnessed more than one manager driving his Ferrari or Lamborghini away from the mess he left behind.

This sounds much more like my favourite industrial horror bedtime reading.

Italy is a real nice place.

If Jan Thiel put the stories on paper I buy first copy.Signed eventually.

[Frits Overmars]

Frits/wobby, if it were possible to maintain a higher pressure in the transfer ports on the 2 stroke engine greater than or equal to the pressure in the cylinder after combustion as the piston descends and the exhaust opens, would this not allow us to place transfer port widows into the cylinder at the same hight as the exhaust port or even higher?Yes it would Breezy. I'd just like to know how you are going to achieve that kind of scavenging pressure, since the cylinder pressure at exhaust opening can be rather high: more than 11 bar in an Aprilia RSA.


This sounds much more like my favourite industrial horror bedtime reading. Italy is a real nice place. If Jan Thiel put the stories on paper I buy first copy.Signed eventually.Italy really is a nice place; I always love to go there. Lovely weather, good food, nice people, lots of small motorsport-minded enterprises willing to perform short-term jobs. And you'll find 'grey economy' anywhere; at least in Italy it's not so hush-hush and more openly accepted, so you can make use of it if you feel the need.

An example of the way things work in Italy: some non-Italian acquaintances of mine were taking part in an Italian race series. The officials there drove them crazy; regulations, if available in English at all, were translated badly, and often refered to other regulations that of course were not at hand. I advised them to not even try and argue with those officials, but instead have lunch with their superior and make sure everybody saw it. Somehow, the day after, all problems were gone...

As for Jan Thiel writing a book: it's not going to happen. We used to think about it; we would have done it together and my background as a technical editor would have come in handy, but for it to be profitable we would have to do it both in English and Italian or Spanish, which would have been just too much of a hassle.
Instead, Jan is now contributing to a couple of forums and if you were to collect all his posts, you'd have quite a book already.

[FastFred]

Surely for dynamic balancing to be of benefit then all the parameters need to be considered. So it should be done fully assembled, running, and mounted in the frame it will be used in.

Yep, plus one. Time consuming but that is the only real way to achieve the best results.

[TZ350]

Team ESE start off guessing at a suitable balance factor.
Then we try it in the bike and refine it by adding or taking a bit off the flywheels each time the engine is apart until we have something that shakes acceptably.
Dynamic balancing will only give you a carefully prepared crank based on a best guess for a BF which may work out to be right but will probably be wrong and need refining.

[Muhr]

I can understand that you want to dynamically balance a crankshaft with cast surfaces. but balancing a fully machined crankshaft? I'm having a hard time understand what new information might pop up just because you start spinning it, with a counterweight that has a geometry that does not resemble anything you will put on the pin.
but I might have missed something :wacko:

As Dave said if you can balance it in the engine it would be another thing.

[lodgernz]

Ball-park :niceone:.
If you can persuade your exhaust pipe to shove 38cc of washed-through fresh mixture back into the cylinder before the exhaust closes, you'll have a winner.
Of course even the washed-through mixure will not be 100% pure, but a long, narrow exhaust duct helps in this respect; it will provide for a small-area contact plane between the spent and the fresh gases. But while mixing is limited, the long, narrow tract offers an unfavourable ratio between duct volume and duct wall surface, thus increasing the heat transfer from the walls to the mixture.

Thanks again Frits. I plan to water-cool as much of the extension as possible, so that might help.

However, your reply makes me wonder if I really need that much volume in the exhaust duct.
I'm using Wobbly's suggested duct length of ca 2 x bore. Do you know if this is based on some factor other than duct volume?

[lodgernz]

I've been so far unable to find any good info on small end bearings, so I hope someone here can give me some advice.

In my 97cc engine I plan to use a piston that has a 14mm pin, with a rod that has a 17mm eye. This requires a bearing with 1.5mm needles, which I have been able to source, with silver cage.
Ignoring for the moment the inadequacy of the rod, is there any reason that needles this small might have a problem at 14,000RPM?

[Pursang]

334782334783

Bike is off for the winter, no conclusion yet, before the spigot had been in thin mild steel welded to the exhaust

More information, (from a fire engineering not automotive site).

https://s3.amazonaws.com/WEBPOSTS/KIWI+ESE/WFVicta/ss+%26+temp.JPG

At the sort of temps we are working with in the exhaust duct, the thermal conductivity of S/S and carbon steel approach each other.
Still leaves S/S the (temporary) advantage of a shiny, radiation (heat) reflective surface.

At lower temperatures a significant difference, suggesting S/S expansion chambers are more likely to retain heat in the body.

Eagerly awaiting the results of Wobbly's tests with ceramic matrix, thermal coatings.

Cheers, Daryl

[TZ350]

I've been so far unable to find any good info on small end bearings, so I hope someone here can give me some advice. 1.5mm needles, is there any reason that needles this small might have a problem at 14,000RPM?

As a comparison. What diameter are the needles in those high reeving 50's that have 10 and 12mm LE pins, could they have needle bearings with needles as small as 1.5mm Dia?

[nine-thirtysix]

Do you guys think it is possible for a experienced welder to weld the exhaust duct without dimensional damage of the plated bore?

I consider to let weld the duct of my CR125 cylinder. The duct has a average length of 50mm and on the floor I would like to fill it up up to 12mm away from the bore.

I was thinking about putting a aluminium mandrel in it but may be the heat transfer is not good enough....


Gesendet von meinem GT-N5100 mit Tapatalk

[Frits Overmars]

Do you guys think it is possible for a experienced welder to weld the exhaust duct without dimensional damage of the plated bore? I consider to let weld the duct of my CR125 cylinder. The duct has a average length of 50mm and on the floor I would like to fill it up up to 12mm away from the bore. I was thinking about putting a aluminium mandrel in it but may be the heat transfer is not good enough.I agree about the heat transfer of a mandrel. As for the welding, personally I would not risk a good cylinder without prior proof that the welder is capable of doing it.

[SwePatrick]

Weld near cylinderbore, i don´t dare do it, :(

But is there material enough to mill a slot and insert a billet piece of aluminium and lock it tight with some fasteners from underside?
Then when in place, shape it as you want.

[jonny quest]

TZ350, do you have a fuel pressure regulator on your EFI system? What pressure do you run, and what is the pressure swing?

[peewee]

Do you guys think it is possible for a experienced welder to weld the exhaust duct without dimensional damage of the plated bore?

I consider to let weld the duct of my CR125 cylinder. The duct has a average length of 50mm and on the floor I would like to fill it up up to 12mm away from the bore.

I was thinking about putting a aluminium mandrel in it but may be the heat transfer is not good enough....


Gesendet von meinem GT-N5100 mit Tapatalk

im just a pretend welder on Saturday and sometimes sunday :laugh: but even if you use large heat sinks on the top and bottom deck and something in the bore, I have a lot of doubts whether you can maintain the exact dimensions of the pre-welded bore. of course I have been wrong thousands of times before however. you can try it, worst case is youll get some distortion (probly the little dividers between transfer windows and possibly the skirt near the bottom) and just strip the plating and over bore it slightly, then replate slightly thicker to get back to original bore size

also I wonder if the weld heat will cause some other problem with the plating ?

[lodgernz]

As a comparison. What diameter are the needles in those high reeving 50's that have 10 and 12mm LE pins, could they have needle bearings with needles as small as 1.5mm Dia?

My 50 and the 80 from which my 97 is developed, both had 12mm gudgeon pins in the same 17mm rod eye, so needles of 2.5mm diameter. No problems revving to 14,000.

I'm just wondering if the smaller contact area of the 1.5mm needles will increase the pressure on the eye and the pin, like stiletto heels do on a carpet compared with flats.
I'll certainly be doing checks after every meeting for a while.

[Grumph]

My 50 and the 80 from which my 97 is developed, both had 12mm gudgeon pins in the same 17mm rod eye, so needles of 2.5mm diameter. No problems revving to 14,000.

I'm just wondering if the smaller contact area of the 1.5mm needles will increase the pressure on the eye and the pin, like stiletto heels do on a carpet compared with flats.
I'll certainly be doing checks after every meeting for a while.

I'd think they'd be OK. When you consider the angular swing of the rod versus the circumference of each roller, the 2.5mm rollers don't do as many revs in that swing. The 1.5mm rollers may actually cover a longer area - and should change direction easier too.

But I'm prepared to be shot down....

[lodgernz]

I'd think they'd be OK. When you consider the angular swing of the rod versus the circumference of each roller, the 2.5mm rollers don't do as many revs in that swing. The 1.5mm rollers may actually cover a longer area - and should change direction easier too.

But I'm prepared to be shot down....

Thanks Grumph. I wouldn't shoot you down, but I'll post here when it's proven one way or the other.

[Grumph]

Thanks Grumph. I wouldn't shoot you down, but I'll post here when it's proven one way or the other.

I've since refreshed my memory and Irving quotes INA using 1.5mm rollers in both big ends and small ends back in the 60's. He says no problem using 10 plus...
Smaller and lighter is said to be a plus for small ends.

[lodgernz]

I've since refreshed my memory and Irving quotes INA using 1.5mm rollers in both big ends and small ends back in the 60's. He says no problem using 10 plus...
Smaller and lighter is said to be a plus for small ends.

All good. Thanks again.

[Michael Moore]

This info from NTN and INA on crankshaft needle bearings may be of use:

http://www.ntnglobal.com/en/products/catalog/pdf/2300E_03.pdf

https://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/tpi/downloads_8/tpi94_de_en.pdf

[TZ350]

TZ350, do you have a fuel pressure regulator on your EFI system? What pressure do you run, and what is the pressure swing?

Yes, a bypass pressure regulator. 3.5bar and no noticeable pressure change from idling to full load. The fuel pump provides more than enough volume of fuel and the surplus passes back to the tank.

[Yow Ling]

My 50 and the 80 from which my 97 is developed, both had 12mm gudgeon pins in the same 17mm rod eye, so needles of 2.5mm diameter. No problems revving to 14,000.

I'm just wondering if the smaller contact area of the 1.5mm needles will increase the pressure on the eye and the pin, like stiletto heels do on a carpet compared with flats.
I'll certainly be doing checks after every meeting for a while.

Hi Lodger, what piston do you run in your 80? Is it a GE3G cylinder?

[lodgernz]

Hi Lodger, what piston do you run in your 80? Is it a GE3G cylinder?

Hi Mike. No, it's a GJ1G (CRM80 I think), bored out to 53mm with a KT100S kart piston. Stroked as well.

[lodgernz]

This info from NTN and INA on crankshaft needle bearings may be of use:

http://www.ntnglobal.com/en/products/catalog/pdf/2300E_03.pdf

https://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/tpi/downloads_8/tpi94_de_en.pdf

Nice! Useful data. Thanks Michael.

[Yow Ling]

Hi Mike. No, it's a GJ1G (CRM80 I think), bored out to 53mm with a KT100S kart piston. Stroked as well.
Ahh thanks KT100 was on my list, there are lots of stock pistons that didnt look great for 14,000. I have a nsr50 and a GE3G to put together

[speedpro]

I think one problem with using KT100 pistons is the process where a piston which is only a very small amount larger is fitted after a hone, and then the next one and the next one and so on. The bore changes shape slightly each time it's used and the hone simply changes the surface texture. I think it would be worthwhile to have the bore ground in a cylindrical grinder every 2nd piston to maintain it's cylindrical shape and remove any taper that may develop. I quite like the look of the Burris pistons but don't know that they are actually any better. They can certainly extend the life of a cylinder due to the increased clearance required versus say a Yamaha piston. there might be some slight difference in the shape of the crown requiring a different head.

[lodgernz]

I think one problem with using KT100 pistons is the process where a piston which is only a very small amount larger is fitted after a hone, and then the next one and the next one and so on. The bore changes shape slightly each time it's used and the hone simply changes the surface texture. I think it would be worthwhile to have the bore ground in a cylindrical grinder every 2nd piston to maintain it's cylindrical shape and remove any taper that may develop. I quite like the look of the Burris pistons but don't know that they are actually any better. They can certainly extend the life of a cylinder due to the increased clearance required versus say a Yamaha piston. there might be some slight difference in the shape of the crown requiring a different head.

Thanks Mike, duly noted. This has been a simple overbore to match the supplied piston, so that shouldn't be an issue this time. I'll bear it in mind for future replacements though.
I make my own head inserts to match whatever piston I'm using, so that also shouldn't be a problem.

[lodgernz]

Ahh thanks KT100 was on my list, there are lots of stock pistons that didnt look great for 14,000. I have a nsr50 and a GE3G to put together

Lucky you! Great engines.

[shnaggs]

Yes, a bypass pressure regulator. 3.5bar and no noticeable pressure change from idling to full load. The fuel pump provides more than enough volume of fuel and the surplus passes back to the tank.

If you are running a regulated return system what if you plumb the top side of the regulator (boost reference) to the pipe??? This is how a lot of turbo 4T adjust the fueling as boost rises and falls...maybe it would work the same with the pipe on the 2T. As pipe pressure rises, so would fuel pressure and hence more fuel. If the pipe collapses then pressure would also, so the fuel pressure would drop as a result.

[Yow Ling]

If you are running a regulated return system what if you plumb the top side of the regulator (boost reference) to the pipe??? This is how a lot of turbo 4T adjust the fueling as boost rises and falls...maybe it would work the same with the pipe on the 2T. As pipe pressure rises, so would fuel pressure and hence more fuel. If the pipe collapses then pressure would also, so the fuel pressure would drop as a result.
I think the purpose of the manifold pressure referenced regulator is not to supply more or less fuel but to keep it constant, if you have 3.5 bar of fuel pressure and 1 bar or boost the rail pressure has to increase to 4.5 bar to counter the 1 bar on the nozzle, and likewise if you have vacuum in the manifold the rail pressure decreases to maintain a constant pressure at the nozzle, this means the computer does not have to account for these changes electronicly

[jbiplane]

More information, (from a fire engineering not automotive site).

Eagerly awaiting the results of Wobbly's tests with ceramic matrix, thermal coatings.

What would be best gasket material - cylinder to header? BTW chainsaws use thermal screen beetween muffler and cylinder.
Possible as well cover header by simple basalt tape
https://www.amazon.com/Titanium-Basalt-Exhaust-Header-Fiber/dp/B0022QOY0C

Question. For simple muffler and 2-stroke. What is optimal stinger diameter for simple lightweight exhaust systems?
Or what optimal back pressure in muffler?
Saw one interesting idea http://www.dragonfly75.com/motorbike/stingersizing.html

[paul gane]

Can anyone help me with an ignition timing map for a TZ250 5F7

[wobbly]

The cylinder to do the Exhaust Port thermal barrier coating test has been at HPC for over week ,and they now say it wont be done till mid next week.
I to am hanging out for the result, and will have it on the dyno the same day it arrives.
The deto sensor will tell immediately if it goes into destruction mode or not.

Re stinger size and pressure.I have measured several engines and found that 2.5psi at full noise seemed to be a constant.
But the process is a bit counter intuitive in that less pressure in the pipe ( ie a big stinger ) renders the pipe less "efficient " at low rpm.
Thus when the return wave comes back to the piston face too early at lower speeds this reduced pressure also reduces the power loss due to the wrongly timed stuffing process.
Increasing the pressure ( a smaller stinger ) makes better power higher up.
This is used in the Jetski world to good effectby having a oversize stinger, and using a rpm controlled solenoid, water is than dumped into it to increase the back pressure at higher engine speeds.
PWM valve control makes it even better.
Easy way to size a stinger ( or nozzle settup ) is to look at the Mach number in the restriction using EngMod, 0.8 Mach works best every time.

[Haufen]

The cylinder to do the Exhaust Port thermal barrier coating test has been at HPC for over week ,and they now say it wont be done till mid next week.
I to am hanging out for the result, and will have it on the dyno the same day it arrives.
The deto sensor will tell immediately if it goes into destruction mode or not.

I suppose a pre-test with flange and part of the header wrapped might give a hint on the result of the coated exhaust port. I would expect the effect to be the similar but not as large as with the coated port.

[TZ350]

If you are running a regulated return system what if you plumb the top side of the regulator (boost reference) to the pipe??? This is how a lot of turbo 4T adjust the fueling as boost rises and falls...maybe it would work the same with the pipe on the 2T. As pipe pressure rises, so would fuel pressure and hence more fuel. If the pipe collapses then pressure would also, so the fuel pressure would drop as a result.

Yes I once thought so too.

I have tried measuring the pressure in the expansion chamber and header at different points.
It turns out that the average pressure at the measuring point falls when the motor is on song and making real power.
Makes sense when you think that more power means more suck and that the suck side of the outgoing wave is stronger than the reflected return wave. From my measurements I found the average to be lower than the outside ambient air pressure.

Unlike a pressurized vessel like say a spray-paint can, an expansion chamber is not filled with a uniformly consistent pressure but has dynamic patches of high and low pressure throughout at the same time.

And as you get on the power and the strength of the suction pulse increases and the average pressure at any point decreases.

In an active expansion chamber there are two different pressure scenarios going on at the same time, "Average" pipe pressure and "Dynamic" pressure at any singular point.

Unless you have a way of timing the sampling at any point chosen point in time it is just random whether you are seeing a high or low patch.

Currently I am trying to read a cylinder pressure pulse just before exhaust port opening as a way of determining if the motor has fired or not. The timing of the pulse and pressure will hopefully be more consistent.

[Yow Ling]

Can anyone help me with an ignition timing map for a TZ250 5F7

Stock 5F7 is 1.1mm BTDC

[2T Institute]

I think one problem with using KT100 pistons is the process where a piston which is only a very small amount larger is fitted after a hone, and then the next one and the next one and so on. The bore changes shape slightly each time it's used and the hone simply changes the surface texture. I think it would be worthwhile to have the bore ground in a cylindrical grinder every 2nd piston to maintain it's cylindrical shape and remove any taper that may develop. I quite like the look of the Burris pistons but don't know that they are actually any better. They can certainly extend the life of a cylinder due to the increased clearance required versus say a Yamaha piston. there might be some slight difference in the shape of the crown requiring a different head.

Erm no not by a long shot. Concentricity was maintained by a quality Sunnen hone, an air cooled cylinder should have a taper. He's a bit crook now but erstwhile forum member Ken Seeber manufactured pistons in a 0.01mm step. Kept old KT100 S and J engines for years and years. Piston to bore clearance can be adjusted to circuit and weather conditions.

[paul gane]

Stock 5F7 is 1.1mm BTDC

Thank you for the reply. Realy looking for graph of advance and retard details.
Can't find any official info from Yamaha.
I understood that these were the first to have a retard curve on a production racing motorcycle...

[DoldGuy]

Currently I am trying to read a cylinder pressure pulse just before exhaust port opening as a way of determining if the motor has fired or not. The timing of the pulse and pressure will hopefully be more consistent.[/QUOTE]


TZ,

I know NOTHING about injection on two strokes (but have tried to follow/understand your venture) and curious of the pressure location just before exhaust opening. Would there be greater differintial just after TDC to determine combustion did/did not occur?

Doldguy

[TZ350]

TZ, I know NOTHING about injection on two strokes (but have tried to follow/understand your venture) and curious of the pressure location just before exhaust opening. Would there be greater differential just after TDC to determine combustion did/did not occur? Doldguy

Thanks for taking an interest in my EFI project. I am not sure I know much about 2T injection either but I am finding it a fun and challenging learning curve.

I agree, just after TDC would give a pretty identifiable pulse and was where I wanted to go at first. After thinking about the 1,000-2,000 psi combustion pressure and taking advice about the damage that detonation would quickly inflict on the pressure sensor I went with Clint's (from www.tfxengine.com (http://www.tfxengine.com/)) suggestion to look at making a pressure tap 10 or so degrees before exhaust port opening. I figured that would be about 100-200 psi and a much lower gas temperature, so much easier to work with.

Actually drilling a small hole for the pressure tap proved challenging. On the NSR cylinder there is not much useful material for drilling holes through that bridges the gap between the cylinder and the water jacket. It was a real challenge to drill a 0.75mm through hole without breaking out into fresh air.

Tonight I ran the bike up and put my finger over the pressure sensor hole in the cylinder. At idle there was plenty of hot gas coming out but as I revved the engine up the volume and temperature of expelled gas significantly reduced. Wasn't expecting that but it is in line with the reduced signal I have seen from the pressure sensors I have tried.

Again it looks to be all about "Time". The response time of the sensor and the the time it takes to expel enough gas to fill all the cavities and start applying pressure to the sensor. As the revvs go up there is less and less time so the signal gets smaller and smaller.

[EssexNick]

TZ. I've also been following your progress with great interest. It seems to me, (and what do I know?), you will always struggle to find a pressure sensor that responds fast enough. Now if you only want to determine whether or not combustion has taken place, would it be possible to use a contact microphone on the outside of the head and just use electronics to differentiate between the sounds of combustion and non-combustion?

[TZ350]

Yes it might have to be where I look next.

[husaberg]

Yes it might have to be where I look next.
Another place to look assuming you cant get the mic or sensor to work would be piston acceleration



During a normal combustion event, the piston speed is lowest at top dead center on the compression stroke, and is the highest with the piston moving downwards during the power stroke. The average engine speed for a single engine revolution would lie in between the lowest and the highest instantaneous values. The difference between the lowest and highest engine speeds is significant enough that any deviation from the values expected during normal combustion can be used to detect a misfire event. If misfire occurs, the crank speed during the power stroke will be significantly lower as there is no downward force being applied on the piston head from combustion of the air fuel mixture. the variation of instantaneous engine speed with crank angle for normal combustion and misfire conditions.

334822
https://www.pi-innovo.com/misfire-detection-with-openecu/

http://www.freepatentsonline.com/6885932.html

[Frits Overmars]

Tonight I ran the bike up and put my finger over the pressure sensor hole in the cylinder. At idle there was plenty of hot gas coming out but as I revved the engine up the volume and temperature of expelled gas significantly reduced. Wasn't expecting that but it is in line with the reduced signal I have seen from the pressure sensors I have tried.
Again it looks to be all about "Time". The response time of the sensor and the time it takes to expel enough gas to fill all the cavities and start applying pressure to the sensor. As the revs go up there is less and less time so the signal gets smaller and smaller.You nailed it TeeZee. Sure, the sensor may be responsible, but even the fastest sensor can only register the delta_pressure/delta_time-variation in the system consisting of engine cylinder, connecting bore and volume in front of the sensor, the worst situation being a long, narrow connecting bore and a large volume in front of the sensor.

It's a bit comparable to an exhaust duct, where the return pulse from the exhaust pipe has to raise the pressure in the duct before it can do any good for the cylinder.

Assuming the sensor itself is up to the job, the bottlebeck in your case will be the 0,75 mm connecting bore. And since that is already borderline, you might concentrate on shortening it if possible, and reducing the cavity volume to absolutely zero.

[jbiplane]

It's a bit comparable to an exhaust duct, where the return pulse from the exhaust pipe has to raise the pressure in the duct before it can do any good for the cylinder.

Is there any idea how make optimal Ligth weight exhaust.
Says for 66 bore 40mm stroke 2 cylinder engine to have good performance at 6800-7200 rpm.
Exhaust temperature 600C. Exhaust duration 190. Crancase compression 1,6

Proposed shapes are
http://www.reaa.ru/yabbfiles/Attachments/Concept2.jpg
http://www.reaa.ru/yabbfiles/Attachments/Enduro_001.jpg
http://www.reaa.ru/yabbfiles/Attachments/Screw_001.jpg
http://www.reaa.ru/yabbfiles/Attachments/C1_001.jpg

Classical variant of 2 scooter muffler could be bulky (and they designed for 9000 rpm)
http://www.reaa.ru/yabbfiles/Attachments/294_2_rez.jpg

[Frits Overmars]

Another place to look assuming you cant get the mic or sensor to work would be piston acceleration

During a normal combustion event, the piston speed is lowest at top dead center on the compression stroke, and is the highest with the piston moving downwards during the power stroke. The average engine speed for a single engine revolution would lie in between the lowest and the highest instantaneous values. The difference between the lowest and highest engine speeds is significant enough that any deviation from the values expected during normal combustion can be used to detect a misfire event. If misfire occurs, the crank speed during the power stroke will be significantly lower as there is no downward force being applied on the piston head from combustion of the air fuel mixture. https://www.pi-innovo.com/misfire-detection-with-openecu/
http://www.freepatentsonline.com/6885932.htmlMy evil mind can't help noticing "the piston speed is lowest at top dead center on the compression stroke". Lovely. I'd add that the piston speed is zero at TDC,
and not just on the compression stroke but at every TDC.
Next, they juggle with the term engine speed. One moment it stands for piston speed, the next moment it's crankshaft rpm, which is quite a different animal.
Ultimately, it comes down to the fluctuations in crankshaft rpm because that's the only thing that can be measured with the encoder they are using. It has to be reliably connected to the crankshaft and it has to be an expensive encoder too, because those 'significant' fluctuations are maybe 1 percent of the nominal crankshaft rpm. Moreover, the cited papers discuss a four-stroke engine. The rpm fluctuations in a two-stroke engine are maybe half of what they are in a four-stroke, which makes it even more difficult to distinguish misfiring.
Compare that to measuring cylinder pressures: the pressure ratio between a firing and a non-firing engine just before exhaust opening can be 500 %.
That's a hell of a lot easier to detect.

Last but not least, if you insist on installing an expensive encoder and measuring the crankshaft speed, what exactly are you seeing? Fluctuations caused by cylinder pressure? Or fluctuations because of a slipping/grabbing clutch? Or a whipping chain? Or because of momentarily contact loss between wheel and road? Just listen to the rising and falling engine rpm on any Isle of Man-video.

[TerraRoot]

TZ, can i point out that DI would solve your part throttle problems? while TBI/port injection solves DI's "not enough time to inject all the go juice at revs" problem

combine the two systems and drop trying to detect misfires as they happen?

[Frits Overmars]

TZ, can i point out that DI would solve your part throttle problems? while TBI/port injection solves DI's "not enough time to inject all the go juice at revs" problem.
combine the two systems and drop trying to detect misfires as they happen?It's not just about misfires, Terraroot. It's mainly about coming on the throttle (or should I say on the pipe?) after a throttled-down deliberate non-firing period.

[TerraRoot]

non-firing, much better word.
what i was getting at, i'm equating the response trouble TZ is having with >
carb:
fourstrokes on part throttle, each non-fire the vaccum is less so less fuel, engine recovers.
FI:
fourstrokes on part throttle, each non-fire the FI-ECU does not know about drowns the engine with fuel making each non fire worse until engine speed drops and ECU notices.

Solve the fourstroking, solve the throttle response. Every DI two-stroke i've heard has a great solid smooth idle/part throttle.

[Yow Ling]

if you monitor the spark waveform it may be different for a ignition event compared to a non ignition event

http://papers.sae.org/950003/

http://www.autoserviceprofessional.com/article/92689/Waveform-diagnostics-Ignition-diagnostics-you-will-actually-use?Page=3

http://www.powerguru.org/advances-in-ignition-systems/

[breezy]

[QUOTE=Frits Overmars;1131080908]Yes it would Breezy. I'd just like to know how you are going to achieve that kind of scavenging pressure, since the cylinder pressure at exhaust opening can be rather high: more than 11 bar in an Aprilia RSA.


Frits thanks for reply,

yes 160psi... mmmm. maybe some yet undisclosed phenomenon could be used to achieve this:laugh: Frits in your years of experience have you ever encountered any strange gas dynamics in a 2 stroke engine which fly against the laws which you have believed to be right ?

[Frits Overmars]

yes 160psi... mmmm. maybe some yet undisclosed phenomenon could be used to achieve this :laugh:. Frits in your years of experience have you ever encountered any strange gas dynamics in a 2 stroke engine which fly against the laws which you have believed to be right ?Many strange encounters of the 2-stroke kind, but in hindsight there are no unexplainable events, just insufficient knowledge. We're working at it; it's an ongoing process :p

[husaberg]

My evil mind can't help noticing "the piston speed is lowest at top dead center on the compression stroke". Lovely. I'd add that the piston speed is zero at TDC,
and not just on the compression stroke but at every TDC.
Next, they juggle with the term engine speed. One moment it stands for piston speed, the next moment it's crankshaft rpm, which is quite a different animal.
Ultimately, it comes down to the fluctuations in crankshaft rpm because that's the only thing that can be measured with the encoder they are using. It has to be reliably connected to the crankshaft and it has to be an expensive encoder too, because those 'significant' fluctuations are maybe 1 percent of the nominal crankshaft rpm. Moreover, the cited papers discuss a four-stroke engine. The rpm fluctuations in a two-stroke engine are maybe half of what they are in a four-stroke, which makes it even more difficult to distinguish misfiring.
Compare that to measuring cylinder pressures: the pressure ratio between a firing and a non-firing engine just before exhaust opening can be 500 %.
That's a hell of a lot easier to detect.

Last but not least, if you insist on installing an expensive encoder and measuring the crankshaft speed, what exactly are you seeing? Fluctuations caused by cylinder pressure? Or fluctuations because of a slipping/grabbing clutch? Or a whipping chain? Or because of momentarily contact loss between wheel and road? Just listen to the rising and falling engine rpm on any Isle of Man-video.
I noticed that with the clusmy wording that was only aimed at the foul strokes but i resisted the urge to alter the wording but even with a 2 stroke assuming its half the difference
Its still pretty intesting how much the speed (well acceleration) alters during a misfire event.
Yes of course i agree pressure is a more direct measure and is a far better way but ony if it actually can be made to work.
Which at this point it is not.
There was another one thrown up that foul stroke use which was using a seperate ignition system firing a spark plug in the exhaust pipe and then measuring the ionization current through that plug.
Which differs if it ignites an actual unburnt mixture..



I should get some points for not putting that one forward.................. even though it might actually serve dual purpose,

three if you count blowing up the pipe.

(which is much the same as an antilag set up on a rally turbo) ,
The encoder... is that from the other patent i posted? not sure how they measure and compare the aceleration?

but from the first link of the system
the misfire looks pretty clear cut.... well using their own data anyway?
334843<strike></strike>

[TZ350]

Click through to the original post to see all the pictures and build details.


Building another Suzuki GP100 NSR 110 hybrid using a standard NSR250 cylinder and using a GP125 rotary valve cover and carb but otherwise keeping the GP100 bottom end pretty stock.

334837334838

The whole motivation for this engine is to have a smaller diameter inlet tract. So I am leaving the original 24mm inlet tract un touched. Previously I would have made this as large as I could get away with.

334839

Got a chance to try the new GP100 with its standard NSR cylinder tonight.

334840

About 25.6 rwhp for the Suzuki GP100 bottom end fitted with a standard NSR MC21 cylinder.

(A Honda MC21 NSR250 is rated at 45hp @ 9k rpm)

My EFI motor with all the bells and whistles, all singing and dancing fully modified bottom end with a really big inlet rotary valve from a Kawasaki KE175, and with the same standard NSR cylinder only made 28 rwhp. So it takes a lot of work on the inlet and bottom end to get another 2.5 hp.

[TZ350]

Back to the EFI 2T project.


TZ, can i point out that DI would solve your part throttle problems? while TBI/port injection solves DI's "not enough time to inject all the go juice at revs" problem. combine the two systems and drop trying to detect misfires as they happen?

More complicated than my Ecotrons system can handle, but a very good idea and if I find myself developing my own ECU and EFI program it could very well be the approach I take. Thanks.


You nailed it TeeZee. Assuming the sensor itself is up to the job, the bottleneck in your case will be the 0,75 mm connecting bore. And since that is already borderline, you might concentrate on shortening it if possible, and reducing the cavity volume to absolutely zero.

I have even tried filling the cavity volume with water in the hope that there would be faster transmission of pressure through an un compressible medium. I haven't totally given up on the pressure sensor idea but ......

A short 0.75mm through hole and a $1000 USD 5mm diameter high speed piezo pressure sensor are used by the professionals, but that sort of gear is a bit out of Jo public's and my reach. I was hoping to find a way to do it with something simpler and more affordable for us home hobby tuners.

Ocean1 first suggested it to me in a PM then Yowling and Husaberg posted about it. Measuring ionization at the plug to determine the potential quality of the combustion mixture and to be able to see the difference between a firing and non firing event. I have followed the links posted by Husa and Yowling and it looks doable but then, so did measuring residual combustion pressure..... :laugh:

334845

Measuring Ionization at the plug .... sounds like its worth a look.

http://www.aces.edu/~parmega/efi/temp/DIY-Ion-Sensing.pdf

[Jannem]

318365

The narrow part of the exhaust window is the original RG50 port and the wider part above the dam is 85% of the bore width.

Without the dam we could have something that looks like the RSA exhaust port.

Looking at the old posts... TZ, how did the 85% turn out IRL. Thinking rings, although I appreciate small bore is likely more forgiving.

[emess]

Frits

your beautiful MB40 cylinder and drawings of your FOS concept engine do not have a radius on the top of the exhaust port to improve flow on as on the Aprilia cylinders.

With shallow exhaust ports like the top of the MB40 T and the exhaust ports of your FOS concept engine do you consider port area more important than improved flow with the radius ?

Any news on the 50cc FOS engine you mentioned some time ago ?

Mick

[TZ350]

Looking at the old posts... TZ, how did the 85% turn out IRL. Thinking rings, although I appreciate small bore is likely more forgiving.

The ring survived but the tuning was all wrong. I think we over cooked the STA for the rpm. All we learnt from the exercise is that you can go quite wide on a 50. Much wider than a 125's 72% but 85% was getting a bit much.

[Frits Overmars]

Frits, your beautiful MB40 cylinder and drawings of your FOS concept engine do not have a radius on the top of the exhaust port to improve flow on as on the Aprilia cylinders. With shallow exhaust ports like the top of the MB40 T and the exhaust ports of your FOS concept engine do you consider port area more important than improved flow with the radius?The Aprilia, developing its maximum power at a piston speed of 23,6 m/s, needed all the blowdown flow it could get. Huge auxiliary exhausts alone were not enough;
the main exhaust port had to be given a timing of no less than 202°, which is clearly too much for optimum resonance, but which was necessary in order to strike a compromise with sufficient blowdown time.area.
The MB40 engine has no piston ring, so the single exhaust port could be made as wide as we wanted, shown in the picture below. With 192° exhaust timing, which is fine for resonance, we could achieve sufficient blowdown time.area without having to wrestle for the last bit of flow coefficient.
It's more or less the same story with the FOS cylinder. It does have a piston ring, but it also has exhaust ports at both sides of the cylinder, again with 192° timing, and with more than enough blowdown time.area.
I must admit that I'd like to try radiused top edges, but that would raise the timing too much for my liking, or I would need new 'castings' (they're not really castings since the FOS cylinders were made via Selective Laser Melting).
334849

[wobbly]

The Exhaust port radius was I believe necessitated by the introduction ( by the ever loved " Great Leader " ) of a new pipe design
that had no top end power.
Jan and his R&D team had to work very hard to retrieve the lost power,and in the end gained better mid as well.
I cant remember if it was Jan or Frits that commented they would have liked to have tried a non radiused port in combination with a better pipe
as this may have proved to have been " better ".

[katinas]

An interesting project and one sentence from the text: "I attributed the lost power to an overly large exhaust port (lazy port) in the cast cylinders…"

http://www.highwaymanbikes.com/the-highwayman-f37-a-fully-custom-purpose-build-vintage-road-racer/

http://www.alloyavenue.com/vb/showthread.php?11802-Air-cooled-2-cycle-motorcycle-racing-cylinder/page7

[nitro2tfx]

You nailed it TeeZee. Sure, the sensor may be responsible, but even the fastest sensor can only register the delta_pressure/delta_time-variation in the system consisting of engine cylinder, connecting bore and volume in front of the sensor, the worst situation being a long, narrow connecting bore and a large volume in front of the sensor.

It's a bit comparable to an exhaust duct, where the return pulse from the exhaust pipe has to raise the pressure in the duct before it can do any good for the cylinder.

Assuming the sensor itself is up to the job, the bottlebeck in your case will be the 0,75 mm connecting bore. And since that is already borderline, you might concentrate on shortening it if possible, and reducing the cavity volume to absolutely zero.

Our own sensors will take the pressure and temperature and are plenty fast enough (accurate readings per crank angle degree) for TZ350's project, but they aren't cheap enough lol. With ours there is essentially no volume between the 0.75mm tube and the sensor. If TZ350 did that with his sensor, I suspect the temperature would kill it. Doubtful if it could be mounted with a near zero volume though because of the size of his sensor. A case where size does matter and smaller is better lol.

Agreed, maybe there could be some significant reduction in volume though, if the sensor was mounted in a less aesthetically pleasing location. However, no matter how small the volume, his sensor has to be able to keep up, which it may or may not be able to do.

[jamathi]

The Exhaust port radius was I believe necessitated by the introduction ( by the ever loved " Great Leader " ) of a new pipe design
that had no top end power.
Jan and his R&D team had to work very hard to retrieve the lost power,and in the end gained better mid as well.
I cant remember if it was Jan or Frits that commented they would have liked to have tried a non radiused port in combination with a better pipe
as this may have proved to have been " better ".

I still think the small radius was better...
After the 'great leader' had left we tested all 6 of his last exhaust designs.
Each pipe cleaned, and with its individually best carburation.
There was almost NO difference.....
All cylinders had the now STD big radius!
There was not a single unradiused cylinder left....

[jamathi]

I still think the small radius was better...
After the 'great leader' had left we tested all 6 of his last exhaust designs.
Each pipe cleaned, and with its individually best carburation.
There was almost NO difference.....
All cylinders had the now STD big radius!
There was not a single unradiused cylinder left....

One question to Frits:

Has a FOS cylinder ever been run actually?
50 or 125cc?
I an still curious after 10 years.

The somewhat similar 'Foekema system' was a complete disaster.....
Even worse than the RYGER.

[Frits Overmars]

One question to Frits: Has a FOS cylinder ever been run actually? 50 or 125cc? I an still curious after 10 years.
The somewhat similar 'Foekema system' was a complete disaster.....Even worse than the RYGER.Curiosity keeps you young; you're welcome Jan :msn-wink:.
A number of people have built engines with the FOS scavenging system, the best-known being Neil Hintz and Ken Seeber, both present on this forum.
Neil also incorporated another idea, variable port timing, and Ken has such an engine running on the dyno. He reports that it is extremely eager to rev :D.
https://www.youtube.com/watch?v=2p0dyPu7Gcs&feature=youtu.be

[jbiplane]

Curiosity keeps you young; you're welcome Jan :msn-wink:.
A number of people have built engines with the FOS scavenging system

Hi Frits&Niels. What do you thinking of this kind of completelly symmetric tuning pipe for FOS use (shown by red)? An initial test on opposite engine gives some positive results. I make it by superposition of 2 classical pipes. Each cone play as expantion as reflexion role for each other.
http://www.reaa.ru/yabbfiles/Attachments/mirrowed_pipe.jpg

[Frits Overmars]

Hi Frits&Niels. What do you thinking of this kind of completelly symmetric tuning pipe for FOS use (shown by red)? An initial test on opposite engine gives some positive results. I make it by superposition of 2 classical pipes. Each cone play as expantion as reflexion role for each other.Well, that's funny Valery. A couple of years ago I posted a similar drawing; not as sophisticated as yours, but showing the same principle. I tried in vain to find it back, so here it is once more; maybe you'll have more luck than me tracing it back. The nice thing is that this type of exhaust system can work with 180°-firing as well as with 360°-firing cylinders.
334853

[emess]

The Aprilia, developing its maximum power at a piston speed of 23,6 m/s, needed all the blowdown flow it could get. Huge auxiliary exhausts alone were not enough;
the main exhaust port had to be given a timing of no less than 202°, which is clearly too much for optimum resonance, but which was necessary in order to strike a compromise with sufficient blowdown time.area.
The MB40 engine has no piston ring, so the single exhaust port could be made as wide as we wanted, shown in the picture below. With 192° exhaust timing, which is fine for resonance, we could achieve sufficient blowdown time.area without having to wrestle for the last bit of flow coefficient.
It's more or less the same story with the FOS cylinder. It does have a piston ring, but it also has exhaust ports at both sides of the cylinder, again with 192° timing, and with more than enough blowdown time.area.
I must admit that I'd like to try radiused top edges, but that would raise the timing too much for my liking, or I would need new 'castings' (they're not really castings since the FOS cylinders were made via Selective Laser Melting).
334849

Many thanks for all the replies Frits, Wobbly and Jan.

The question came from having an exhaust port with little metal to remove in the duct so the minimum area is about 10mm from the port.

Maybe Wobbly's 0.8 Mach in Engmod is the best guide to the area problem.

Would be interesting how Jan approached making a cylinder work with another design pipe.

Mick

[breezy]

Evening... well it is here... i think this reed block is off a mini moto.....does anyone know where i could get some thing smaller than this off the shelf?334854

maybe with only one petal... this reed block is approx 50 x 60 mm.. thanks.

[speedpro]

Honda MB100 reed blocks are single sided. With a carbon petal and the bridge removed they are still good for at least 19.9hp and that was with poor porting and a substandard pipe

[husaberg]

Evening... well it is here... i think this reed block is off a mini moto.....does anyone know where i could get some thing smaller than this off the shelf?334854

maybe with only one petal... this reed block is approx 50 x 60 mm.. thanks.

DLE 20
334855


Arrow Motorized Cycles
334856
Also some chainsaws have very small reed valves.

[lucf]

One question to Frits:

Has a FOS cylinder ever been run actually?
50 or 125cc?
I an still curious after 10 years.

The somewhat similar 'Foekema system' was a complete disaster.....
Even worse than the RYGER.

The whole story after exact 10 years:
FST-twostroke-design https://www.facebook.com/notes/luc-foekema/fst-twostroke-design/4080202582494
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131082527#post1131082527

[wobbly]

Haha, the link doesnt work - sadly,like a Ryger.

[Yow Ling]

Link works fine

[husaberg]

Works better than Jacinda's birth control anyway

[jbiplane]

Well, that's funny Valery. A couple of years ago I posted a similar drawing; not as sophisticated as yours, but showing the same principle. I tried in vain to find it back, so here it is once more; maybe you'll have more luck than me tracing it back. The nice thing is that this type of exhaust system can work with 180°-firing as well as with 360°-firing cylinders.
334853

Thanks Frits. My objective is to make 2 cylinder paramotor engines (to reduce vibration on human being back) and exhaust system very important for.
Before implement is nice to know if idea is in general good, but I dont know simple and robust method to design system like this. My friend make some
calculations in Fluent, but it complicate, time consuming and non evident.

https://www.youtube.com/watch?v=1awpBQ_2N5w

[jamathi]

Curiosity keeps you young; you're welcome Jan :msn-wink:.
A number of people have built engines with the FOS scavenging system, the best-known being Neil Hintz and Ken Seeber, both present on this forum.
Neil also incorporated another idea, variable port timing, and Ken has such an engine running on the dyno. He reports that it is extremely eager to rev :D.
https://www.youtube.com/watch?v=2p0dyPu7Gcs&feature=youtu.be

I am happy to hear that Frits!!

[breezy]

thanks for messages/ replies on the reed valves,:drinknsin:drinknsin

[breezy]

[QUOTE=TZ350;1131081218]Thanks for taking an interest in my EFI project. I am not sure I know much about 2T injection either but I am finding it a fun and challenging learning curve.



Tonight I ran the bike up and put my finger over the pressure sensor hole in the cylinder. At idle there was plenty of hot gas coming out but as I revved the engine up the volume and temperature of expelled gas significantly reduced.

The temperature drop... can this be explained?:sherlock: would it be different if it misfired?

[lucf]

The link is public on Facebook but in case it doesn't work, here is a part of this note which contains much replies from all over the world, incl. Jan Thiel, Frits Overmars and Ken Seeber.

FST a new twostroke design
Foekema Symmetric Twostroke


Forword
The first FST text was published on 19 january 2008. 3 month later on 16 March 2008 at 20.00hr the first FST engine was started in my home and my wife Hetty did make the movie on YouTube. One day later Jan Thiel called me to congratulate me, that was close before he went to Thailand.

first start of the engine March 16, 2008 https://www.youtube.com/watch?v=jtTc7sk8WS8

Now, more than 10 years later it is still not successful, yes it runs, but not in the way it should do. Partly due to the speed defined by the mixing of fresh and burnt gases, the fresh gases thus go too far directly into the exhausts. Therefore the temperature of the exhaust stays to low and so the speed can not increase further. It is therefore far from optimal cylinder filling and so it can have no power. Yes this was directly be heard during the first start and it was with adjustment, what I initially thought, not to get out. The solution must be sought in the process. The scavenging is also expected as very critical and needs to be improved in some way. And may be some day it will run, with new idees it is not impossible, I'm still working on it.

What do we know at this moment
1. In the 20s of the last century there were already engines with this system,
2. In the 50s there were Russian coxmotortjes model for this system,
3. In 1986 a patent for granted in England, but without a sequel,
4. Rotax has tested it expanded in 1989, without success
5. Frits Overmars has published his idee more than a month after my FST, and still he only has a printed cylinders. While he wrote in his publication: " Luc it is all about who has the first running engine "
6. He called it FOS, but should have called it VDS, because he got the idea from Cees van Dongen in 1969, that's why it took 30 years like he wrote.
7. Ken Seeber 29 July, 2013 wrote he had the idea in 1984, but not 100% TA, read below

And what about those engines in the 20's of mr Dolf. That answer is quit simple, those engines are not 100% TA and had no expansion exhaustpipes and therefore only runs in low engine speed with very low power. My prototype that runs after 2 months, had much more speed, but not enough, what it should be. Even without proper exhaust pipes like those Russian glowplug motors it can run for sure. However, in both cases, with much less port surface, with less engine speed and so very low power is available, what the real reason was to start this project.

What actions now?
Seen together it seems that it is never going to work. Does it still feel like there's still time to stabbing? From Frits I have not heard that he is going to stop it, much hurry he did not seem te have, after what is now known. Does it still make sense for me? No and Yes, No, because I do not have the impression that I could do it better than Rotax. Yes because I do have the engine, the cylinder and the exhaust pipes, so why not try something else? I am now 70 and still do not feel to be too old to learn. I'm looking for new idees to solve the current problems. Read below how it all started.


First publication of this new 2 stroke process
website: http://www.geocities.ws/lucfoekema/FSTsystemNL.html


Original text of January 19, 2008

FST a new twostroke scavenging system. About 2 years ago I got the idea to change the way of scavenging of the twostroke engine. The current way of scavenging exist almost from the beginnng of the 2-stroke history and never changed, unless the many other systems which had been founded. But thinking to get more power you automaticly come to new ideas. So to me it came about two years ago, and that is the Foekema Symmetric Twostroke (FST).

It was not my intention to announce this new idea before making and testing it, but I was supprised when reading the magazine of Kickstart of january this year. Frits Overmars also got a new idea, which he called the FOS system. When reading, I thought: "I'm not sure, but it could be the same". Lucky for me he didn't explain the system, otherwise he would be the first. May be it is different, than we will have 2 new systems at almost the same time. The idea is not very difficult, but realising ideas like this is not that easy, because it has to be made very precisely.
Many things in two-stroke tuning has been made since the beginning of the two stroke. That is why I thought that someone else already did the same in the past. Till sofare I didn't want to spend time for this because there are many more important things to do when you wanted to be the fastest 50cc sprinter in the world on the 150 meter and the 1/4 mile.

The only thing I did was an announcement on the Kreidler.nl site, but without an explenation. Also I did tell it to some friends. But because in the current circumstances, I can't wait to explain my new system. That's why I like to introduce you the "Foekema Symmetric Two-stroke" (FST)
Who would be the first realising the idea in a working prototype is another question. Althought this system should produce more power than the current way, it still is the question, if in practice this will be prooven.

FST scavenging
Symmetric is one part to explain the system, but most important is the 100% Time Area. The whole scavenging will proceed in a symmetric way. After burning the gasses, when the piston goes down, the 4 exhaustducts opens first at the same time and the burned gasses leaves the cylinder. These ducts are fully symmetric around in the cylinder, so the gasses can flow into the 4 exhaustpipes very fast. After that, all symmetric transfers opens also at the same time and fresh gasses flows from all directions right over the piston to the center of the cylinder. This result in a flow of the gasses in the direction of the chamber, while pressing the last burned gasses to the edge of the cylinder. In the chamber the fresh gasses will turn around in the direction of the four exhaust ducts, behind the burned gasses.
So two rows of fully symmetric and 100% Time Area ports. The upper 4 ports are exhausts, the lower row are transfers. Which results in much maximum Time Area capacity, which is 100%. There is no more room left for ducts.

Advantage of FST scavenging
The big advantage is that the whole scavenging will proceed much faster than in the current two-stroke way, because of the maximum TA capacity. That is why a much higher rpm is reacheable with the same or even a lower duration of exhausts and transfers.
Beside this there is another great advantage the symmetric scavenging keeps the temperature in the cylinder completely the same all arround. In the current way there are always risks that one side of the cylinder is more hot than the other side.

There is much more to read and to see if you follow the link, which is public, in Dutch and English
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131082527#post1131082527
https://www.facebook.com/notes/luc-foekema/fst-spoeling/4085704360035
or here website, which is not up to date, because I don't have access anymore: http://www.geocities.ws/lucfoekema/FSTsystemNL.html

[SwePatrick]

The whole story after exact 10 years:
FST-twostroke-design https://www.facebook.com/notes/luc-foekema/fst-twostroke-design/4080202582494

I can´t actually see how you could solve the problem, the column of air is far different from ordinary twostrokes.
As the column rises in the center of bore the it will be pulled down into exhaust both due to pipe suction and also by itself.
When column hits the combustionchamber and start heading downwards again near cylinderwalls it will actually decrease incoming column(because it 'rubs' against eachother) in speed hard and thereby it will be chaos and it all ends up in the exhaust with or witout suction from pipe.
Maybe it could be a little bit better if aiming all transfers the same way all around to build a swirl upwards in cylinder.

In my eyes, not worth spending money on.

[Haufen]

The link is public on Facebook but in case it doesn't work, here is a part of this note which contains much replies from all over the world, incl. Jan Thiel, Frits Overmars and Ken Seeber.

FST a new twostroke design
Foekema Symmetric Twostroke


Thanks for posting the information here. And thumbs up for your effort in daring to try the unknown in building and testing something new.

So, ten years later, could you show us some dyno graphs of the engine from testing? And a comparison between this engine and one with a conventional layout?
What were your findings? And how do you rate the potential of such an engine after your first hand experience? Which are the critical areas from your point of view?

In the best case, you might get some new input from the discussion here, in the worst case, you would have passed on your experience.

[lucf]

The link is public on Facebook but in case it doesn't work, here is a part of this note which contains much replies from all over the world, incl. Jan Thiel, Frits Overmars and Ken Seeber.

FST a new twostroke design
Foekema Symmetric Twostroke


Forword
The first FST text was published on 19 january 2008. 3 month later on 16 March 2008 at 20.00hr the first FST engine was started in my home and my wife Hetty did make the movie on YouTube. One day later Jan Thiel called me to congratulate me, that was close before he went to Thailand.

first start of the engine March 16, 2008 https://www.youtube.com/watch?v=jtTc7sk8WS8

Now, more than 10 years later it is still not successful, yes it runs, but not in the way it should do. Partly due to the speed defined by the mixing of fresh and burnt gases, the fresh gases thus go too far directly into the exhausts. Therefore the temperature of the exhaust stays to low and so the speed can not increase further. It is therefore far from optimal cylinder filling and so it can have no power. Yes this was directly be heard during the first start and it was with adjustment, what I initially thought, not to get out. The solution must be sought in the process. The scavenging is also expected as very critical and needs to be improved in some way. And may be some day it will run, with new idees it is not impossible, I'm still working on it.

What do we know at this moment
1. In the 20s of the last century there were already engines with this system,
2. In the 50s there were Russian coxmotortjes model for this system,
3. In 1986 a patent for granted in England, but without a sequel,
4. Rotax has tested it expanded in 1989, without success
5. Frits Overmars has published his idee more than a month after my FST, and still he only has a printed cylinders. While he wrote in his publication: " Luc it is all about who has the first running engine "
6. He called it FOS, but should have called it DOS, because he got the idea from Cees van Dongen in 1969, that's why it took 30 years like he wrote.
7. Ken Seeber 29 July, 2013 wrote he had the idea in 1984, but not 100% TA, read below

And what about those engines in the 20's. That answer is quit simple, those engines are not 100% TA and had no expansion exhaustpipes and therefore only runs in low engine speed with very low power. My prototype that runs after 3 months, had much more speed, but not enough, what it should be. Even without proper exhaust pipes like those Russian glowplug motors it can run for sure. However, in both cases, with much less port surface and therefore also with less engine speed and so very low power is available. What for me was the real reason to start this project.

What actions now?
Seen together it seems that it is never going to work. Does it still feel like there's still time to stabbing? From Frits I have not heard that he is going to stop it, much hurry he did not seem te have, after what is now known. Does it still make sense for me? No and Yes, No, because I do not have the impression that I could do it better than Rotax. Yes because I do have the engine, the cylinder and the exhaust pipes, so why not try something else? I am now 70 and still do not feel to be too old to learn. I'm looking for new idees to solve the current problems. Read below how it all started.


First publication of this new 2 stroke process
website: http://www.geocities.ws/lucfoekema/FSTsystemNL.html


Original text of January 19, 2008

FST a new twostroke scavenging system. About 2 years ago I got the idea to change the way of scavenging of the twostroke engine. The current way of scavenging exist almost from the beginnng of the 2-stroke history and never changed, unless the many other systems which had been founded. But thinking to get more power you automaticly come to new ideas. So to me it came about two years ago, and that is the Foekema Symmetric Twostroke (FST).

It was not my intention to announce this new idea before making and testing it, but I was supprised when reading the magazine of Kickstart of january this year. Frits Overmars also got a new idea, which he called the FOS system. When reading, I thought: "I'm not sure, but it could be the same". Lucky for me he didn't explain the system, otherwise he would be the first. May be it is different, than we will have 2 new systems at almost the same time. The idea is not very difficult, but realising ideas like this is not that easy, because it has to be made very precisely.
Many things in two-stroke tuning has been made since the beginning of the two stroke. That is why I thought that someone else already did the same in the past. Till sofare I didn't want to spend time for this because there are many more important things to do when you wanted to be the fastest 50cc sprinter in the world on the 150 meter and the 1/4 mile.

The only thing I did was an announcement on the Kreidler.nl site, but without an explenation. Also I did tell it to some friends. But because in the current circumstances, I can't wait to explain my new system. That's why I like to introduce you the "Foekema Symmetric Two-stroke" (FST)
Who would be the first realising the idea in a working prototype is another question. Althought this system should produce more power than the current way, it still is the question, if in practice this will be prooven.

FST scavenging
Symmetric is one part to explain the system, but most important is the 100% Time Area. The whole scavenging will proceed in a symmetric way. After burning the gasses, when the piston goes down, the 4 exhaustducts opens first at the same time and the burned gasses leaves the cylinder. These ducts are fully symmetric around in the cylinder, so the gasses can flow into the 4 exhaustpipes very fast. After that, all symmetric transfers opens also at the same time and fresh gasses flows from all directions right over the piston to the center of the cylinder. This result in a flow of the gasses in the direction of the chamber, while pressing the last burned gasses to the edge of the cylinder. In the chamber the fresh gasses will turn around in the direction of the four exhaust ducts, behind the burned gasses.
So two rows of fully symmetric and 100% Time Area ports. The upper 4 ports are exhausts, the lower row are transfers. Which results in much maximum Time Area capacity, which is 100%. There is no more room left for ducts.

Advantage of FST scavenging
The big advantage is that the whole scavenging will proceed much faster than in the current two-stroke way, because of the maximum TA capacity. That is why a much higher rpm is reacheable with the same or even a lower duration of exhausts and transfers.
Beside this there is another great advantage the symmetric scavenging keeps the temperature in the cylinder completely the same all arround. In the current way there are always risks that one side of the cylinder is more hot than the other side.

There is much more to read and to see if you follow the link, which is public, in Dutch and English
https://www.facebook.com/notes/luc-foekema/fst-spoeling/4085704360035
or here website, which is not up to date, because I don't have access anymore: http://www.geocities.ws/lucfoekema/FSTsystemNL.html

The reason to post this is:
1. That the whole story should be known and not some details.
2. I did not work on the system for many years, but this doesn't mean that it stays that way.
3. I got hundreds of ideas from all over the world how to do, but I never saw one which was bright enough to try.


.https://www.facebook.com/luc.foekema/media_set?set=a.1084500731820.11700.1805454134&type=3https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5847 1;image

[Muhr]

The temperature drop... can this be explained?:sherlock: would it be different if it misfired?


I suppose pipe length to the sensor is devastating for reaction time!?
something more that came to mind was Bernoulli's principle :dodge:


The faster air moves the lower pressure it has (Bernoulli's principle). So when you blow faster, your stream of air is lower pressure than the surrounding air. Thus the surrounding air fills in the stream. The surrounding air is probably cooler than the exhaust gas.

Just want to clarify that the cooling effect occurs when you release into the atmosphere.

[Haufen]

The reason to post this is:
1. That the whole story should be known and not some details.
2. I did not work on the system for many years, but this doesn't mean that it stays that way.
3. I got hundreds of ideas from all over the world how to do, but I never saw one which was bright enough to try.

1. that is always the best way.
2. I understand, I've got projects like this, too. Most people have, I think.
3. So you would like to discuss and get fresh ideas?

[Pursang]

Re stinger size and pressure.I have measured several engines and found that 2.5psi at full noise seemed to be a constant.
But the process is a bit counter intuitive in that less pressure in the pipe ( ie a big stinger ) renders the pipe less "efficient " at low rpm.
Thus when the return wave comes back to the piston face too early at lower speeds this reduced pressure also reduces the power loss due to the wrongly timed stuffing process.
Increasing the pressure ( a smaller stinger ) makes better power higher up.
This is used in the Jetski world to good effectby having a oversize stinger, and using a rpm controlled solenoid, water is than dumped into it to increase the back pressure at higher engine speeds.
PWM valve control makes it even better.
Easy way to size a stinger ( or nozzle settup ) is to look at the Mach number in the restriction using EngMod, 0.8 Mach works best every time.

What about an undersized stinger/nozzle and a blow-off valve regulating pipe bleed pressure to maintain (say)2.5 psi at all engine speeds?
Often thought about it, never found any reference, anywhere. More bottom end and over-rev without ignition retard.

Cheers, Daryl.

[breezy]

The faster air moves the lower pressure it has (Bernoulli's principle).

Just want to clarify that the cooling effect occurs when you release into the atmosphere.

ok thanks.... just seems weird... as your sampling the gases in the cylinder at a higher rpm, with the heat increasing with more fuel combusting and yet the stream of gas at that sensor hole sending out cooler air just before the exhaust port opens. i would have expected to burn my finger :crazy:

[lohring]

The FOS system still seems promising. I've run a lot of simulations on EngMod and still get more power with it than Aprilia style porting in a 26 cc disk valve engine. However, EngMod's scavenging model may not give the correct scavenging efficiency. One slightly off topic question: Can you plate a laser sintered cylinder?

Lohring Miller

[SwePatrick]

Does even programs calculate how aircolumn is movin in cylinder?

I think they are only calculating areas vs areas, and how 'much' it flows' etc etc.

The column is very complicated to calculate.

[FastFred]

Thanks Lucf for posting the information here. And thumbs up for your effort in daring to try the unknown in building and testing something new.

Plus One for that, very interesting project.

[wobbly]

Pursang - you have it arse about face.You dont want 2.5 psi at low rpm , less is better.
So a small stinger would need a blow off that dumped pressure at low rpm, then closed off to raise the pressure as speed went up.

And as for anyone asking Luc to produce a dyno graph of his FOS setup, that is like asking Jesus for a sign that he is planning on coming back.

[lucf]

And as for anyone asking Luc to produce a dyno graph of his FOS setup, that is like asking Jesus for a sign that he is planning on coming back.


It seems to me that you have to read it over again !

.

[Grumph]

It seems to me that you have to read it over again !

.

I tend to agree. This system must be looked at quite separately from the Ryger debacle. You've been very frank about what you've seen as the failings of this layout - and at this point I think it is probably a blind alley. But if someone does not at least shine a light up these alleys we'll never know if they're worth pursuing.

From where I'm sitting it looks like both the Bradshaw/Ryger and the FOS type systems have basic faults with scavenging. Pressure pulse or enhanced velocity scavenging seems to clear the cylinder unevenly (Bradshaw's published results). The FOS system with it's multiple exhausts would seem to evacuate the cylinder too well, leading to probable charge loss.
Neither system would seem to develop the rising column of fresh charge shaped to drive out the residual exhaust gases as has been pointed out by SwePatrick.

[lucf]

Maybe it could be a little bit better if aiming all transfers the same way all around to build a swirl upwards in cylinder.



That was 10 years ago the first thing I did, but at that time no result !
This doesn't mean it was a bad idea.

[wobbly]

Must have missed something, but I am still searching high and low for a real dyno printout of a FST, or a Ryger for that matter.

[Pursang]

Pursang - you have it arse about face. I get that a lot. :facepalm:


You don't want 2.5 psi at low rpm , less is better.

Low Pressure = Low Density / Low Temp > Slow SoS + Weaker pulse
High Pressure = High Density / High Temp > Faster SoS + Stronger Pulse

So the Low pressure & slower SoS is to make the pipe seem longer?
The waves travel faster than the gasses, I was thinking that a stronger return pulse might be useful at the the lower end of the band.


So a small stinger would need a blow off that dumped pressure at low rpm, then closed off to raise the pressure as speed went up.

If Bleed diameter is 'too small' at high speed, then mass flow through the engine will be restricted and so will peak power output.

Cheers, Daryl.

[TZ350]

What about an undersized stinger/nozzle and a blow-off valve regulating pipe bleed pressure to maintain (say)2.5 psi at all engine speeds?
Often thought about it, never found any reference, anywhere. More bottom end and over-rev without ignition retard. Cheers, Daryl.

I have tried it, an expansion chamber pressure bleed, see the posts below for pictures and dyno graph.


I have been having trouble with detonation in over rev and I hope to cure it by bleeding some of the pipe pressure off.


The mid chamber bleed. Tried it open and closed, Red open, Blue closed. The big surprise was how quiet it was when open, hardly any more noise at all, certainly wouldn't need any sort of muffler.

[jamathi]

Must have missed something, but I am still searching high and low for a real dyno printout of a FST, or a Ryger for that matter.

Yes Wobbly, and I think we will never see one.....

Did you already test the ceramic coated exhaust duct?

[Pursang]

I have tried it, an expansion chamber pressure bleed, see the posts below for pictures and dyno graph.

Thanks TZee & Wobbly,

So much good info buried in this thread.

I definitely need to adjust my thought process, but there is potential for broadening power bands with pressure bleed management.

Cheers, Daryl.

[TZ350]

.
Just had to give the Piezo thing another go before giving up and going down the ion sensing rout.

334868

9mm Piezo disk glued to a plastic button with a really short connecting hose to absolutely minimize the dead space in the system.

334867

And wouldn't you know, it worked. Gives an identifiable signal all the way to 12,000+ rpm.

<div style="position:relative;height:0;padding-bottom:75.0%"><iframe src="https://www.youtube.com/embed/PyAhPmUNW1k?ecver=2" width="480" height="360" frameborder="0" allow="autoplay; encrypted-media" style="position:absolute;width:100%;height:100%;left:0" allowfullscreen></iframe></div>

Blipping it up in the shed. Motor a little rich in the mid range. But there is an identifiable signal all the way up to 12,000 rpm. And the signal drops off during over run as you would expect and comes back under acceleration again.

[Jannem]

I get that a lot. :facepalm:



Low Pressure = Low Density / Low Temp > Slow SoS + Weaker pulse
High Pressure = High Density / High Temp > Faster SoS + Stronger Pulse

So the Low pressure & slower SoS is to make the pipe seem longer?
The waves travel faster than the gasses, I was thinking that a stronger return pulse might be useful at the the lower end of the band.



If Bleed diameter is 'too small' at high speed, then mass flow through the engine will be restricted and so will peak power output.

Cheers, Daryl.

If I get this right, the smaller bleed could would work at the low rpm, if the pipe was tuned to that range. In practise, the pipe is tuned to high rpm, and bigger bleed helps low because it reduces the detrimental effect of the out of tune return wave.

[lucf]

Must have missed something, but I am still searching high and low for a real dyno printout of a FST, or a Ryger for that matter.


It's about what I have to tell about the FST system after 10 years and nothing else.
If you read it well, you will ask relevant questions, otherwise you have to read it over again and again, till you understand what I did write.
Only relevant question will be answered.


The reason to post this is:
1. That the whole story should be known and not only some details.
2. I did not work on the system for many years, but this doesn't mean that it stays that way.
3. I got hundreds of ideas from all over the world how to do, but I never saw one which was bright enough to try.





FST a new twostroke design
Foekema Symmetric Twostroke

Forword
The first FST text was published on 19 january 2008. 3 month later on 16 March 2008 at 20.00hr the first FST engine was started in my home and my wife Hetty did make the movie on YouTube. One day later Jan Thiel called me to congratulate me, that was close before he went to Thailand.

first start of the engine March 16, 2008 https://www.youtube.com/watch?v=jtTc7sk8WS8

Now, more than 10 years later it is still not successful, yes it runs, but not in the way it should do. Partly due to the speed defined by the mixing of fresh and burnt gases, the fresh gases thus go too far directly into the exhausts. Therefore the temperature of the exhaust stays to low and so the speed can not increase further. It is therefore far from optimal cylinder filling and so it can have no power. Yes this was directly be heard during the first start and it was with adjustment, what I initially thought, not to get out. The solution must be sought in the process. The scavenging is also expected as very critical and needs to be improved in some way. And may be some day it will run, with new idees it is not impossible, I'm still working on it.

What do we know at this moment
1. In the 20s of the last century there were already engines with this system,
2. In the 50s there were Russian coxmotortjes model for this system,
3. In 1986 a patent for granted in England, but without a sequel,
4. Rotax has tested it expanded in 1989, without success
5. Frits Overmars has published his idee more than a month after my FST, and still he only has a printed cylinders. While he wrote in his publication: " Luc it is all about who has the first running engine "
6. He called it FOS, but should have called it DOS, because he got the idea from Cees van Dongen in 1969, that's why it took 30 years like he wrote.
7. Ken Seeber 29 July, 2013 wrote he had the idea in 1984, but not 100% TA, read below

And what about those engines in the 20's. That answer is quit simple, those engines are not 100% TA and had no expansion exhaustpipes and therefore only runs in low engine speed with very low power. My prototype that runs after 3 months, had much more speed, but not enough, what it should be. Even without proper exhaust pipes like those Russian glowplug motors it can run for sure. However, in both cases, with much less port surface and therefore also with less engine speed and so very low power is available. What for me was the real reason to start this project.

What actions now?
Seen together it seems that it is never going to work. Does it still feel like there's still time to stabbing? From Frits I have not heard that he is going to stop it, much hurry he did not seem te have, after what is now known. Does it still make sense for me? No and Yes, No, because I do not have the impression that I could do it better than Rotax. Yes because I do have the engine, the cylinder and the exhaust pipes, so why not try something else? I am now 70 and still do not feel to be too old to learn. I'm looking for new idees to solve the current problems. Read below how it all started.


First publication of this new 2 stroke process
website: http://www.geocities.ws/lucfoekema/FSTsystemNL.html


Original text of January 19, 2008

FST a new twostroke scavenging system. About 2 years ago I got the idea to change the way of scavenging of the twostroke engine. The current way of scavenging exist almost from the beginnng of the 2-stroke history and never changed, unless the many other systems which had been founded. But thinking to get more power you automaticly come to new ideas. So to me it came about two years ago, and that is the Foekema Symmetric Twostroke (FST).

It was not my intention to announce this new idea before making and testing it, but I was supprised when reading the magazine of Kickstart of january this year. Frits Overmars also got a new idea, which he called the FOS system. When reading, I thought: "I'm not sure, but it could be the same". Lucky for me he didn't explain the system, otherwise he would be the first. May be it is different, than we will have 2 new systems at almost the same time. The idea is not very difficult, but realising ideas like this is not that easy, because it has to be made very precisely.
Many things in two-stroke tuning has been made since the beginning of the two stroke. That is why I thought that someone else already did the same in the past. Till sofare I didn't want to spend time for this because there are many more important things to do when you wanted to be the fastest 50cc sprinter in the world on the 150 meter and the 1/4 mile.

The only thing I did was an announcement on the Kreidler.nl site, but without an explenation. Also I did tell it to some friends. But because in the current circumstances, I can't wait to explain my new system. That's why I like to introduce you the "Foekema Symmetric Two-stroke" (FST)
Who would be the first realising the idea in a working prototype is another question. Althought this system should produce more power than the current way, it still is the question, if in practice this will be prooven.

FST scavenging
Symmetric is one part to explain the system, but most important is the 100% Time Area. The whole scavenging will proceed in a symmetric way. After burning the gasses, when the piston goes down, the 4 exhaustducts opens first at the same time and the burned gasses leaves the cylinder. These ducts are fully symmetric around in the cylinder, so the gasses can flow into the 4 exhaustpipes very fast. After that, all symmetric transfers opens also at the same time and fresh gasses flows from all directions right over the piston to the center of the cylinder. This result in a flow of the gasses in the direction of the chamber, while pressing the last burned gasses to the edge of the cylinder. In the chamber the fresh gasses will turn around in the direction of the four exhaust ducts, behind the burned gasses.
So two rows of fully symmetric and 100% Time Area ports. The upper 4 ports are exhausts, the lower row are transfers. Which results in much maximum Time Area capacity, which is 100%. There is no more room left for ducts.

Advantage of FST scavenging
The big advantage is that the whole scavenging will proceed much faster than in the current two-stroke way, because of the maximum TA capacity. That is why a much higher rpm is reacheable with the same or even a lower duration of exhausts and transfers.
Beside this there is another great advantage the symmetric scavenging keeps the temperature in the cylinder completely the same all arround. In the current way there are always risks that one side of the cylinder is more hot than the other side.

There is much more to read and to see if you follow the link, which is public, in Dutch and English
https://www.facebook.com/notes/luc-foekema/fst-spoeling/4085704360035
or here website, which is not up to date, because I don't have access anymore: http://www.geocities.ws/lucfoekema/FSTsystemNL.html



.https://www.facebook.com/luc.foekema/media_set?set=a.1084500731820.11700.1805454134&type=3https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5847 1;image[/QUOTE]

[F5 Dave]

Oh Jebus, show us a sign.
Like a finger wavering nervously over a clutch lever.

[Pursang]

If I get this right, the smaller bleed could would work at the low rpm, if the pipe was tuned to that range. In practice, the pipe is tuned to high rpm, and bigger bleed helps low because it reduces the detrimental effect of the out of tune return wave.

This is a definite possibility, like everything in 2T there are compromises & multiple solutions. The basic thrust of the ESE thread is for peak power outputs for racing, confirmed by Sims & Dyno & Race Results. There are other applications.

Cheers, Daryl.

[Frits Overmars]

I tend to agree. This system must be looked at quite separately from the Ryger debacle. You've been very frank about what you've seen as the failings of this layout - and at this point I think it is probably a blind alley. But if someone does not at least shine a light up these alleys we'll never know if they're worth pursuing. From where I'm sitting it looks like both the Bradshaw/Ryger and the FOS type systems have basic faults with scavenging. Pressure pulse or enhanced velocity scavenging seems to clear the cylinder unevenly (Bradshaw's published results). The FOS system with it's multiple exhausts would seem to evacuate the cylinder too well, leading to probable charge loss. Neither system would seem to develop the rising column of fresh charge shaped to drive out the residual exhaust gases as has been pointed out by SwePatrick.Grumph, you are entitled to your opinion, but it seems to me that it is based solely on Lucs allegations. I wasn't going to dignify his stories with a reaction, but I cannot allow him to put people on a false tract with his alternative facts. There are too many perversions of the facts, both historically and technically, to go into all of them.
I would have thought he already demonstrated his level of civilisation and credibility before on this forum. You don't need to take my word for it; you can check with respectable people like Jan Thiel, Wobbly Wayne Wright, Neil Hintz, Ken Seeber.

[lucf]

Grumph, you are entitled to your opinion, but it seems to me that it is based solely on Lucs allegations. I wasn't going to honour his stories with a reaction, but I cannot allow him to put people on a false tract either with his alternative facts. I would have thought he's already demonstrated his level of civilisation and credibility before on this forum and others. There are just too many perversions of the facts, both historically and technically, to go into all of them. You don't need to take my word for it; you can check with respectable people like Jan Thiel, Wobbly Wayne Wright, Neil Hintz and Ken Seeber.

We call it in Dutch: "al is de leugen nog zo snel de waarheid achterhaald hem wel"
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131082527#post1131082527

[SwePatrick]

Luc!

Why does your dynoprintout from Rygerengine have the same graphics layout as your simulation program? (just different colours)

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Is it because the dynoprintout of the infamous Ryger is just a desktop/computer product?
Or is your dyno connected to your simulationprogram?

[lucf]

Luc!

Why does your dynoprintout from Rygerengine have the same graphics layout as your simulation program? (just different colours)


Because I take over the original registrated data to an Excel file, so no simulation at all.
The original data I used, are also published in the past, but it looks like nobody wanted to see this.
The only simulation program I use since 2001 is Mota and I know all disadvantages.
For real situations you still can use it, but for experimentations it's almost useless.
Real calculations I do since about 1998 in my own developped software, which is not for sale.
Ryger is impossible to simulate in Mota, I didn't even try it.

[Grumph]

Grumph, you are entitled to your opinion, but it seems to me that it is based solely on Lucs allegations. I wasn't going to honour his stories with a reaction, but I cannot allow him to put people on a false tract with his alternative facts. There are too many perversions of the facts, both historically and technically, to go into all of them.
I would have thought he already demonstrated his level of civilisation and credibility before on this forum. You don't need to take my word for it; you can check with respectable people like Jan Thiel, Wobbly Wayne Wright, Neil Hintz, Ken Seeber.

I've met Wobbly and Neil, Frits. I'm assuming that you've met Luc - proximity at least. Where someone is posting in a second language it's often difficult to establish intent from the content of a post. I looked at the FOS type system information and was prepared to give Luc the benefit of the doubt on that one.
Certainly he's been much more informative there than in any of the Ryger posts. I'm aware that there are a lot of unresolved issues, I can't do anything about them.
I'll shut up therefore on anything concerning Luc.

[FastFred]

Luc! Why does your dynoprintout from Rygerengine have the same graphics layout as your simulation program? (just different colours)

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Because I take over the original registrated data to an Excel file

I understand you can do that with EngMod2T too, create a file from a dynograph then import it into EngMod for graphical comparison of a real dyno run with EngMod's simulated runs.

[lucf]

Grumph, you are entitled to your opinion, but it seems to me that it is based solely on Lucs allegations. I wasn't going to honour his stories with a reaction, but I cannot allow him to put people on a false tract with his alternative facts. There are too many perversions of the facts, both historically and technically, to go into all of them.
I would have thought he already demonstrated his level of civilisation and credibility before on this forum. You don't need to take my word for it; you can check with respectable people like Jan Thiel, Wobbly Wayne Wright, Neil Hintz, Ken Seeber.

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131082527#post1131082527

[TZ350]

Please Locf, dont spoil the dinner party by getting in a huff.

This is the place to post pictures and explanations about ones work, talking is one thing but reveling ones recipes and the failures and successes are what we meet here for.

You don't need to tell us how good a cook you are, if your baking is good and your recipe makes sense and is understandable people will love you for it.

[wobbly]

Jan, I hope to have the cylinder with the coated duct in my hands tomorrow.
I will dyno this immediately and publish an actual dyno curve of the before and after result.
But I wont import the data into Excel ( where its easy to manipulate ) i will simply publish the real data.

I have said this before and I will say it again,anything Luc has to say on here is a complete waste of his and our time.
No one believes, no one cares - bugger off Luc and dont come back until we see a REAL dyno result that in some way goes toward
the original Ryger proclamation of 70 Hp - 30,000 rpm.

Frits gave us all some real hope that the system was a new,viable, 2T advancement.
All we have had since he pulled the plug on his involvement ( wonder why ), is a pile of nonsense and self justification that hasn't even come close to being accepted here.

[Muhr]

At last I've got all measurements of the ports in place! It's amazing how much time you need to get all angles and area in place.:wacko: Thank you Frits for the amazing library of pictures and drawings you posted on the RSA and RSW over the years.:2thumbsup

[Haufen]

The FOS system still seems promising. I've run a lot of simulations on EngMod and still get more power with it than Aprilia style porting in a 26 cc disk valve engine. However, EngMod's scavenging model may not give the correct scavenging efficiency. One slightly off topic question: Can you plate a laser sintered cylinder?

Lohring Miller

Yes, you can plate a laser sintered cylinder if you can plate the aluminium it is made of. From memory, the material which almost every company offering this service has on their portfolio can be plated. For a 26cc cylinder this might have even become affordable in the meantime (what you have to pay is mostly linear to the weight of the part).

As I've never seen any real world dyno graph of a "symmetric 2-stroke", be it FST, FOS, Rotax, Ken or Neils engine or any other (please let me know if I missed something), would you show us the comparison from the simulation?

[Carel H]

Also maintained contacts with the Internal affairs and Justice, concerning procedures, production and distribution of passports and other security documents.
All people who are qualify for Security work are screened for this.



We call it in Dutch: "al is de leugen nog zo snel de waarheid achterhaald (=achterhaalt) hem wel"

I presume such a job description would at least require the ability and the will to write proper, legal Dutch, not?
Stop digging your hole, you're deep enough.

[nitro2tfx]

.
Just had to give the Piezo thing another go before giving up and going down the ion sensing rout.

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9mm Piezo disk glued to a plastic button with a really short connecting hose to absolutely minimize the dead space in the system.

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And wouldn't you know, it worked. Gives an identifiable signal all the way to 12,000+ rpm.

:woohoo: Sometimes that last kick at the can does the trick.

[Flettner]

Ok, serous question, in the olden days some manufactures (CZ) ran twin exhaust ports. I imagine to help cool the center bridge on the twin exhaust ports.
Looking at a modern bridged port, the gas flow out near the edge of the port can't be that good.
If a modern take on the old twin port, each port angling away from each other (say 30 degrees) would that not help increase ultimate gas flow on blow down?
More cooled (water cooled, right up to the bridge) exhaust port surface available to help cool the over flow charge.
Would two chambers be better pumping action than one larger one? I realise there is only so much energy available from the exhaust gas (you can't get something from nothing) but maybe two smaller chambers may be better?
Building a new cylinder and can't make up my mind on what exhaust configuration.

[mr bucketracer]

I've met Wobbly and Neil, Frits. I'm assuming that you've met Luc - proximity at least. Where someone is posting in a second language it's often difficult to establish intent from the content of a post. I looked at the FOS type system information and was prepared to give Luc the benefit of the doubt on that one.
Certainly he's been much more informative there than in any of the Ryger posts. I'm aware that there are a lot of unresolved issues, I can't do anything about them.
I'll shut up therefore on anything concerning Luc.don't let the Nazi's get to you

[TZ350]

How this thread continues to get my pictures upside down I have no idea..... :facepalm:

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Parts for the 9mm Piezo electric sensor.

Basically its a Piezo disk sitting in a recess in the plastic button and held in place by being covered with silicon glue.

The face of the disk is not glued, only the back is covered in glue. Replacing the disk is very straight forward, just scrape the old one off and glue a new one on. The disks are cheap as chips.

To get a coherent signal and eliminate some noise I am going to try a small bridge rectifier.

The 0.7V forward voltage drop across the rectifier should block a lot of low level ripple and leave me with a decently shaped pulse to work with. Well we will see how that goes. Here is hoping .... :D

[husaberg]

.
Just had to give the Piezo thing another go before giving up and going down the ion sensing rout.



9mm Piezo disk glued to a plastic button with a really short connecting hose to absolutely minimize the dead space in the system.


And wouldn't you know, it worked. Gives an identifiable signal all the way to 12,000+ rpm.

Blipping it up in the shed. Motor a little rich in the mid range. But there is an identifiable signal all the way up to 12,000 rpm. And the signal drops off during over run as you would expect and comes back under acceleration again.
Do you have access to a data logger a tinytalk or similar (i guess you use tinytalks for work?)
there are pretty cheap ie sub $100 bluetooth voltage loggers about now.
I think it would be a good idea to log some laps with one just to see if it gives a consistant result and then you can set a base line for the signals.

[SwePatrick]

Because I take over the original registrated data to an Excel file, so no simulation at all.
The original data I used, are also published in the past, but it looks like nobody wanted to see this.
The only simulation program I use since 2001 is Mota and I know all disadvantages.
For real situations you still can use it, but for experimentations it's almost useless.
Real calculations I do since about 1998 in my own developped software, which is not for sale.
Ryger is impossible to simulate in Mota, I didn't even try it.

And by doing this you will never get any respect, people will believe that it is all humbug.
third party dynoprintout is the key =)

[TZ350]

To get a coherent signal and eliminate some noise I am going to try a small bridge rectifier.

Well that didn't work very well, only the most determined spikes got through. Maybe try again and amplify the original signal before running it through a bridge with the amp clipping the bigger signals to a max of 5 Volts for the Aduino digital input.


Do you have access to a data logger a tinytalk or similar (i guess you use tinytalks for work?)
there are pretty cheap ie sub $100 bluetooth voltage loggers about now.

I think it would be a good idea to log some laps with one just to see if it gives a consistent result and then you can set a baseline for the signals.

A small data logger, great idea. We use 4-20's at work, I will have to see if I can find a Voltage logger. Probable not ready for it yet as I don't have a decent signal, but it certainly makes sense. The loggers we use, typically multi channel and certified and run $2000+ so some pointers where to source something more affordable would be great.

[EssexNick]

If the volt drop across one diode is about 0.6V, then surely the drop through a bridge must be 1.2v? Maybe this is why you're not getting enough signal.
Edit: The more I think about it, a bridge rectifier will just turn the signal into a not very smooth DC output. Try just using a single diode in line.

[TZ350]

If the volt drop across one diode is about 0.6V, then surely the drop through a bridge must be 1.2v? Maybe this is why you're not getting enough signal.

Edit: The more I think about it, a bridge rectifier will just turn the signal into a not very smooth DC output. Try just using a single diode in line.

Yes I think you are right. 1.2 1.4 volt drop and maybe the half wave may work better, I will try it.

[Frits Overmars]

Can you plate a laser sintered cylinder?
Yes, you can plate a laser sintered cylinder if you can plate the aluminium it is made of. From memory, the material which almost every company offering this service has on their portfolio can be plated.If you want to make sure, check with the laser sintering company and with the plating company.
When I had my cylinders lasered, experience with the process was still limited, so I sent some test samples to the plater before going all the way.
We used AlSi12 powder.
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[lohring]

Yes, you can plate a laser sintered cylinder if you can plate the aluminium it is made of. From memory, the material which almost every company offering this service has on their portfolio can be plated. For a 26cc cylinder this might have even become affordable in the meantime (what you have to pay is mostly linear to the weight of the part).

As I've never seen any real world dyno graph of a "symmetric 2-stroke", be it FST, FOS, Rotax, Ken or Neils engine or any other (please let me know if I missed something), would you show us the comparison from the simulation?

I'm working on the real designs now for a better comparison. Learning Fusion 360 so I can build a more exact model of the engines to simulate is taking a long time. My day job keeps getting in the way as well. I'll post a couple of designs as well as the simulations when I get them finished.

Lohring Miller

[tjbw]

Yes I think you are right. 1.2 1.4 volt drop and maybe the half wave may work better, I will try it.

Did you try a low pass filter?

It can be as simple as a resistor in series with a capacitor in parallel.

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-8/low-pass-filters/

Also, you could encapsulate the complete assembly, to reduce any spurious accoustic coupling?

[Jannem]

Perhaps this in a noob question...

Normally the blowdown time area is a struggle, but say if you have an engine designed for lower rpm, with proper pipe and transfer STA, is there such a thing as too much blowdown assuming exhaust duration is also optimal? Or does ex duration move also down enough to keep blowdown always at the limit?
If there indeed can be too much blowdown, then what are the symptoms?

[Frits Overmars]

Normally the blowdown time area is a struggle, but say if you have an engine designed for lower rpm, with proper pipe and transfer STA, is there such a thing as too much blowdown assuming exhaust duration is also optimal? Or does ex duration move also down enough to keep blowdown always at the limit?
If there indeed can be too much blowdown, then what are the symptoms?If you want a two-stroke with a four-stroke character (and four-stroke-like power) you can reduce the exhaust timing until the blowdown time.area is just sufficient.
If you want a serious two-stroke, you need to take advantage of exhaust pulse superposition and that more or less nails the optimum exhaust timing around 190°.
For a low rpm engine this means that you will only need a narrow single exhaust port. If the port is wider than necessary, you will suffer increased loss of fresh mixture,
resulting in power loss, high specific fuel consumption and dirty exhaust gases.

[Jannem]

And if you used 190* exhaust open, wide and low height port opening, you’d have less mixture loss, but also narrower tuned range, because of shorter pulse?

When the blowdown is “right “ for specific rpm, how much of the time area is sonic choked?

[wobbly]

No - due to the strong superposition effect the power band is way wider than normal with a port down at 190*.
When the blowdown is " correct " the outflow from the increasing piston port area is sonic until almost TPO.
Look at this outflow Mach trace of a KZ10C that has theoretical blowdown just sufficient for over 50Hp at 13500 ( crank )
It makes exactly that,in the sim and in reality.
The residual blowdown pressure above the transfers is what enables port stagger to influence the scavenging regime in the way it does.
With more pressure above the first opening transfer port, than there is below it from the case - there will be instantaneous backflow, until that pressure delta subsides.

[dutchpower]

What you think about this Wobbly

[Jannem]

Trying to comprehend what I'm seeing in the graph:

Blowdown angle is 30 degrees and goes subsonic 8 degrees before TPO, so that means ~27% of the blowdown angle just before TPO is subsonic and somewhat bigger % of time, as it happens after 90deg crank angle? Looks small in the graph, but seems bigger looking at the numbers.

Is that second 0.8 mach peak in ex.port velocity at 218 degrees from diffuser rarefication combined with intake side pressure pulse (+superposition from previous cycle)?

The quick change of direction to .6 mach right after is the end cone reflection (+superposition from previous cycle)?

[lucf]

Grumph, you are entitled to your opinion, but it seems to me that it is based solely on Lucs allegations. I wasn't going to honour his stories with a reaction, but I cannot allow him to put people on a false tract with his alternative facts. There are too many perversions of the facts, both historically and technically, to go into all of them.
I would have thought he already demonstrated his level of civilisation and credibility before on this forum. You don't need to take my word for it; you can check with respectable people like Jan Thiel, Wobbly Wayne Wright, Neil Hintz, Ken Seeber.


Reply after publishing the FST on Facebook April 19, 2013


Van mijn vader had ik gehoord dat hij dit systeem in 1969 uitgedacht had,
hij kon alleen geen goede gieterij vinden die een cilinder kon gieten zonder gietgallen.
Cilinders lekten constant water.
Hij is vanwege tijdsgebrek er weer mee gestopt en heeft het idee uitgelegd aan Frits Overmars.
Die zou er daarna, met modelbouwmotortjes succes mee gehad hebben.

William van Dongen

[flyonly]

Can someone tell me if its as simple as unplugging my alternator to have a total loss system for racing or are there other things I need to consider?

[jasonu]

Reply after publishing the FST on Facebook April 19, 2013


Van mijn vader had ik gehoord dat hij dit systeem in 1969 uitgedacht had,
hij kon alleen geen goede gieterij vinden die een cilinder kon gieten zonder gietgallen.
Cilinders lekten constant water.
Hij is vanwege tijdsgebrek er weer mee gestopt en heeft het idee uitgelegd aan Frits Overmars.
Die zou er daarna, met modelbouwmotortjes succes mee gehad hebben.

William van Dongen

From my father I had heard that he had invented this system in 1969,
he just could not find a good foundry that could pour a cylinder without casting holes.
Cylinders were constantly leaking water.
He stopped because of lack of time and explained the idea to Frits Overmars.
He would then have had success with model construction engines.

[wobbly]

Your graph Dutchpower is from the actual Exhaust port face.
It is much more enlightening to place the transducer at the duct exit, before the transition to the header.
If this hits 0.8 Mach then you know the exit area is correct.
The STA number for the port takes into account the effects of choked flow as the piston open area enlarges.
While you are at it look at the Mach at the stinger entry, again 0.8 Mach is a good place to be starting with that.

Re total loss - many times a CDI system like an Ignitech will perform alot better if the charging system is connected.
This is due to the voltage being around 14V and the DC DC converter transforms this increase from the lower 12V a battery produces , to
a much higher voltage at the plug.

[Pursang]

If you want a serious two-stroke, you need to take advantage of exhaust pulse superposition and that more or less nails the optimum exhaust timing around 190°.
For a low rpm engine this means that you will only need a narrow single exhaust port. If the port is wider than necessary, you will suffer increased loss of fresh mixture,
resulting in power loss, high specific fuel consumption and dirty exhaust gases.

So, a power valve system that brings in and out the auxiliary ports would/could/should be better than one that adjusts the port height and ex. duration.

cheers, Daryl.

[Jannem]

No - due to the strong superposition effect the power band is way wider than normal with a port down at 190*.


If you have properly designed time areas for 13krpm, the blowdown will be "too much" at 10krpm, but the properly designed system still has the widest powerband, meaning relatively little loss of fresh charge. Is this because the T-ports designed for 13k are somewhat lazy below, so the excess BD wont hurt that much?

[dutchpower]

Your graph Dutchpower is from the actual Exhaust port face.
It is much more enlightening to place the transducer at the duct exit, before the transition to the header.
If this hits 0.8 Mach then you know the exit area is correct.
The STA number for the port takes into account the effects of choked flow as the piston open area enlarges.
While you are at it look at the Mach at the stinger entry, again 0.8 Mach is a good place to be starting with that.


Thank you Wobble

[Jannem]

Is that sharp peak on top of the curves an indication of slightly small nozzle area? Or high blowdown area at the top of the ex. port at cylinder surface?

[TZ350]

Did you try a low pass filter? It can be as simple as a resistor in series with a capacitor in parallel.

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-8/low-pass-filters/

Thanks for the suggestions, the ideas will come in handy.

I have had a bit of success tonight. Used a $12.90 kitset amp from Jaycar as a front end before the bridge rectifier. It worked a treat and gave a very consistent signal.

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I used the 0.5W champ amp to amplify the signal from the Piezo disk then passed the output through the bridge rectifier. Very crisp, sharp and consistent signal up to 12,000 rpm.

The Champ amp is based on the LM386 Op amp. With no real load on the output, the output signal was quite high. I need a 5 Volt digital signal for the Arduino input so over the next few nights I will see if I can trade some height for signal width that the Arduino can easily see.

Anyway, very pleased, it feels like progress...... :niceone:

[Jannem]

So, a power valve system that brings in and out the auxiliary ports would/could/should be better than one that adjusts the port height and ex. duration.

cheers, Daryl.
I suppose it depends if your triple port becomes bd limited at some point or not.

[Frits Overmars]

Van mijn vader had ik gehoord dat hij dit systeem in 1969 uitgedacht had,
hij kon alleen geen goede gieterij vinden die een cilinder kon gieten zonder gietgallen.
Cilinders lekten constant water.
Hij is vanwege tijdsgebrek er weer mee gestopt en heeft het idee uitgelegd aan Frits Overmars.
Die zou er daarna, met modelbouwmotortjes succes mee gehad hebben.

William van Dongen
From my father I had heard that he had invented this system in 1969,
he just could not find a good foundry that could pour a cylinder without casting holes.
Cylinders were constantly leaking water.
He stopped because of lack of time and explained the idea to Frits Overmars.
He would then have had success with model construction engines.Jasonu, your translation is 100% correct. But the original Dutch text is not. Here is what happened:
Around 1995 I discussed my FOS scavenging system with Cees van Dongen (great character, saddly missed). Cees used to cast his own cylinders, based on the Mahle-Kreidler racing cylinders. Cees then showed me an experimental cylinder in which he had added a small transfer port under the exhaust. This was the only difference. Contrary to Lucs suggestions there were no circumferential exhausts, no symmetric transfer ports, no central scavenging column, in short: no resemblance to my system.
The casting of this prototype was too porous to be properly tested, as William van Dongen confirms, and Cees let me have the cylinder as a souvenir.
The picture below with the yellow transfer port shows an impression. When I get back to Holland, I can take a picture of the original cylinder and post it.

@ William van Dongen: if this cylinder has a sentimental value to you, just let me know and I'll let you have it.

@TZ350: sorry to clutter up your thread. I didn't start this conversation and there is no other place for me to rectify what was being said here.
Now I wonder if Luc has the balls to rectify what he wrote about the Van Dongen-cylinder in this forum and in the other places where he posted the same text.
By the way, that's the way the whole thing started. At the end of 2007 and the beginning of 2008 I presented my scavenging idea in a racing newsletter and in a Dutch motorcycle magazine, accompanied by drawings and a picture of a cylinder that had clearly been running.
Luc, whom I had never heard of before, promptly launched a me-too reaction all over the internet. He even claimed to have been the first with a running engine, because he posted a video while I had better things to do.
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[TZ350]

Cees used to cast his own cylinders, based on the Mahle-Kreidler racing cylinders. Cees then showed me an experimental cylinder in which he had added a small transfer port under the exhaust. This was the only difference.

The casting of this prototype was too porous to be properly tested, as William van Dongen confirms, and Cees let me have the cylinder as a souvenir. The picture below with the yellow transfer port shows an impression.

That was a very interesting bit of back history about the FOS concept.

When we had trouble with virtual leaks in prototype cast vacuum boxes we would vacuum impregnate them with resin. I wonder if that could be a temporary solution for a porous cylinder. It could easily be done to a raw casting before machining as the resin completely penetrates all the casting porosity's.

[Frits Overmars]

So, a power valve system that brings in and out the auxiliary ports would/could/should be better than one that adjusts the port height and ex. duration.That would still leave you with a combination of exhaust timing and pipe dimensions, meant for a higher rpm. If you really want to broaden the power band, you can:
A: Lower the timing of all exhaust ports. This will lose you the benefit of wave superposition, but strong waves at the wrong time are undesirable anyway,
or
B: use a trombone pipe. Then you can use your suggestion of bringing the auxiliary ports in and out, in order to adapt the blowdown time.area to the rpm, and still keep the main port at its optimum timing of 190°, because with the longer pipe that will work fine at lower revs, and you'll even keep the superposition advantage.

[lucf]

Jasonu, your translation is 100% correct. But the original Dutch text is not. Here is what happened:
Around 1995 I discussed my FOS scavenging system with Cees van Dongen (great character, saddly missed). Cees used to cast his own cylinders, based on the Mahle-Kreidler racing cylinders. Cees then showed me an experimental cylinder in which he had added a small transfer port under the exhaust. This was the only difference. Contrary to Lucs suggestions there were no circumferential exhausts, no symmetric transfer ports, no central cavenging column, in short: no resemblance to my system.
The casting of this prototype was too porous to be properly tested, as William van Dongen confirms, and Cees let me have the cylinder as a souvenir.
The picture below with the yellow transfer port shows an impression. When I get back to Holland, I can take a picture of the original cylinder and post it.

@ William van Dongen: if this cylinder has a sentimental value to you, just let me know and I'll let you have it.

@TZ350: sorry to clutter up your thread. I didn't start this conversation and there is no other place for me to rectify what was being said here.
Now I wonder if Luc has the balls to rectify what he wrote about the Van Dongen-cylinder in this forum and in the other places where he posted the same text.
By the way, that's the way the whole thing started. At the end of 2007 and the beginning of 2008 I presented my scavenging idea in a racing newsletter and in a Dutch motorcycle magazine, accompanied by drawings and a picture of a cylinder that had clearly been running.
Luc, whom I had never heard of before, promptly launched a me-too reaction all over the internet. He even claimed to have been the first with a running engine, because he posted a video while I had better things to do.
334894

Well if you are right, which should be confermed by William van Dongen, I don't have any problem to correct what's wrong.
But you write 1995 while it happend in 1969

And still one point more, you didn't published your system before I did on Jan 19th 2008, so you have to correct your description too.
In my FST publication the exact description has been published as realy happend, including the prints of your text in the those Dutch motorcycle magazine, so everyone can see what is the real sequence.

This is were you find the first publication on January 19, 2008
http://www.geocities.ws/lucfoekema/FSTsystemNL.html
and here first forum http://www.kreidler.nl/forum/viewtopic.php?f=5&t=25485

This was your first reaction on jan 21, 2008 to my publication and read wel, because more than one thing doesn't stroke with the text you write above.

In a column that appeared last year in the journal KicXstart, I described how ever the idea arose of a new flushing system for two-stroke engines, the FOS-scavening.

Recently commented Mr Luc Foekema that he probably had the same thought as me.Thats possible. I walk for thirty years with that idea around and I'm not the only one who occasionally logical thinking.
I would not even be surprised if the same principle eighty years ago even once conceived. I know how it feels when your own ideas popping up somewhere else.
That has happened several times myself. What do you do? Nothing. It's just sad, but I never wake located. I thought most: "You see? I was right."
And everyone who comes in the same situation may think of me the same.Mr. Foekema is honest enough to mention that the idea to him about two years ago has risen.
For me that is a while ago, but that does not matter. Ideas count only when they are realized.

So I would say: "Do your best, Luc. Shows how well the system is that you and I have independently invented.
I hope my engine runs first. But if you're too quick for me, I hope that yours runs fast. Success ".

Frits Overmars

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131082527#post1131082527
https://www.facebook.com/notes/luc-foekema/fst-twostroke-design/4080202582494

[Frits Overmars]

Don't worry TZ350, I'm not going to bite :D.

[F5 Dave]

Luc you really are poisonous. Have a look at your life. But take your fucked up agendas somewhere else.

[katinas]

If you want to make sure, check with the laser sintering company and with the plating company.
When I had my cylinders lasered, experience with the process was still limited, so I sent some test samples to the plater before going all the way.
We used AlSi12 powder.
334883 334884


Interesting, whether was a small pits after machining and what resistance to cracking?


Last year, after second Rygerised engine broke because of too small piston ring end gap ( someone call when I prepare to adjust the gap ……), decide revert to original, because short summer time and want familirised with 1cylinder std. engine. Tried to test as much as possible until the end of the year. Not to extract max hp, but to understand the engine's response to various changes.

So forest was in the 2T smell at the second half of the year. Two times stopped near the cars with the raised hood and ladies in panic for possible engine fire. After explain what a matter, they agree that smell of racing two stroke oil much nicer than cigaretts.

Limited myself only on not to change Ex and Trans bandwidth. On cylinders only intake and bottom part was drastically changed ( boyesen ports, intake to transfers and flow through bottom Ex duct directly to A Trans). This is old boyesen type cylinder with maybe 30 hp limits, but if someone still interested I'll be happy to answer.

Maybe this is very old answered question. This particular oversquare engine (57x50,6 mm. rod 109 mm) never work well after 10500 rpm with 50 percentage ( 8,35mm ) squash band. Whatever did nothing changes: gap from 0.7 to 1,2 mm., different combustion shape, different compression different timing and combination all of that . 9 different heads. Bottom and mid good.

All changed with 5 mm squash band. Revs nice from 10500 to 13000 rpm in every combination with diff. compression and shape. Of course mid weaker ( not much from 5000-7000 )

Maybe with different rod length / stroke ratio and piston dia. some correction needed to 50 percentage.

Now return to Rygerised engine again with different flow (later put skech). Just finished piston. And other good thing is that my friend buy dyno, but he lives 300km from my home so I cant test whatever I want.

Nuoširdžiai dėkojui jums Fritsai

[wobbly]

Frits wont bite because he is a gentleman.
Im not so I will bite,again.
Luc FUCK OFF - no one believes and no one cares.
This forum is here for people to help each other by adding small snippets of helpful 2T knowledge with each post.
All you have done is blatant self promotion,and self aggrandizement.
If you carry on I am absolutely sure we ( as a group ) could ask the moderator of this excellent thread to have you locked out.


Edit - Dutchpower, just be sure that when you look at the entry to the stinger that the Ex transducer position is set to the correct length.
This is not important if its just a straight tube, but if its a nozzle then you need to set the transducer to that nozzle position.
ie if the length is set at 80mm than both ExMach(1) and ExMach(2) will be at this length down each of Pipe 1 and Pipe 2 ( 2 being the stinger )

[katinas]

Luc


I did not meet with Frits personally, but I never read any bad words from this intelligent and intellectual soul.
Personally for me, Frits and Jan made miracle when reveal so much covered small GP secrets. And if from my young days I have the opportunity meet these people they would be like second fathers.

[JanBros]

Wobbly :

Luc is amazing, he makes the best engines. EVER. Yes it's true.
He is the hardest working dutchman and he want's to make Luc great again, after that horrible Ryger-president (or is it spelled precedent ?) yes it 's true. He is the best, everybody loves him.
and the Mexicans will pay for his FST :yes:

[wobbly]

LOL, thats the first time ever I have felt the need to use that phrase.
Absolute gold, even Lozza would be hard pressed to have put it better,period.

[TZ350]

This forum is here for people to help each other by adding small snippets of helpful 2T knowledge with each post.

..................... Totally True .... :drinknsin

[WilDun]

.
This forum is here for people to help each other by adding small snippets of helpful 2T knowledge with each post.




..................... Totally True .... :drinknsin

I don't usually participate here (no engines to participate with, but do read it all out of interest)
Several have tried to change it all by promoting themselves without understanding what the thread is all about. They only take notice of others or their endeavours when they disagree with them.
:niceone:

[dutchpower]

Edit - Dutchpower, just be sure that when you look at the entry to the stinger that the Ex transducer position is set to the correct length.
This is not important if its just a straight tube, but if its a nozzle then you need to set the transducer to that nozzle position.
ie if the length is set at 80mm than both ExMach(1) and ExMach(2) will be at this length down each of Pipe 1 and Pipe 2 ( 2 being the stinger )

Thanks Wobble ( end cone dia. is 16 mm and stinger 18 mm )

But what you think of the grafiek

[husaberg]

But what you think of the grafiek
http://gifon007.eu/wp-content/uploads/2016/11/Giraffe-Lick-Camera-Funny-Gif-Video.gif:innocent:

[wobbly]

The Mach graphic shows that the duct exit diameter is pretty much spot on - try a little bigger and see what happens to the Mach and the subsequent power level.
Some engines ( lower bmep ) like a tighter exit.
But I think the stinger exit is a little small.
Neels code has some difficulty correctly modelling real steps like you have, with a small cone end dumping into a larger stinger.
Is this modeled as a definite defined step input ?
Try changing the setup to a proper nozzle, and look at the Mach within the nozzle length.

[dutchpower]

The Mach graphic shows that the duct exit diameter is pretty much spot on - try a little bigger and see what happens to the Mach and the subsequent power level.
Some engines ( lower bmep ) like a tighter exit.
But I think the stinger exit is a little small.
Neels code has some difficulty correctly modelling real steps like you have, with a small cone end dumping into a larger stinger.
Is this modeled as a definite defined step input ?
Try changing the setup to a proper nozzle, and look at the Mach within the nozzle length.

Bigger exit duct give less power

Oke will try nozzle
16 mm is not so smal for a 50 cc !!!

[Frits Overmars]

Everybody, thank you so much for your kind words and moral support :hug:
334906
Now let's get back to business :D.

[Pursang]

..................... Totally True .... :drinknsin..........https://www.kiwibiker.co.nz/forums/images/icons/icon14.png

[JanBros]

LOL, thats the first time ever I have felt the need to use that phrase.
Absolute gold, even Lozza would be hard pressed to have put it better,period.

glad I could finaly return you a favor for all your shared knowledge :not::drinknsin

[lucf]

FOS is not the idea of Frits Overmars


Van mijn vader had ik gehoord dat hij dit systeem in 1969 uitgedacht had,
hij kon alleen geen goede gieterij vinden die een cilinder kon gieten zonder gietgallen
Cilinders lekten constant water.
Hij is vanwege tijdsgebrek er weer mee gestopt en heeft het idee uitgelegd aan Frits Overmars.
Die zou er daarna, met modelbouwmotortjes succes mee gehad hebben.
William van Dongen

Reaction Frits

Around 1995 I discussed my FOS scavenging system with Cees van Dongen (great character, saddly missed).
Cees used to cast his own cylinders, based on the Mahle-Kreidler racing cylinders. Cees then showed me an experimental cylinder in which he had added a small transfer port under the exhaust.
This was the only difference. Contrary to Lucs suggestions there were no circumferential exhausts, no symmetric transfer ports, no central scavenging column, in short: no resemblance to my system.
The casting of this prototype was too porous to be properly tested, as William van Dongen confirms, and Cees let me have the cylinder as a souvenir.
The picture below with the yellow transfer port shows an impression. When I get back to Holland, I can take a picture of the original cylinder and post it.
Now I wonder if Luc has the balls to rectify what he wrote about the Van Dongen-cylinder in this forum and in the other places where he posted the same text.

@ William van Dongen: if this cylinder has a sentimental value to you, just let me know and I'll let you have it.

Here is the answer from William van Dongen

Het gaat toch juist om het idee van een spoelpoort onder de uitlaatpoort ?
Mijn vader kon het verder niet testen en uitwerken.
Ik wil die cilinder wel hebben ! Mijn adres is Waalpad 7, 2652DH Berkel en Rodenrijs
Ergens moet het idee beginnen, daarna ga je het uitwerken.
Zonder dat idee met die cilinder, was hij waarschijnlijk niet op idee gekomen.
Als je een spoelpoort onder de uitlaatpoort plaatst is de volgende stap toch automatisch dat je ze rondom wil gaan plaatsen ?
William van Dongen

I know Cees van Dongen and his father from the past, I realy don't believe they only talked about one transfer under one exhaustduct.
When Frits published in dec 2007 how the idea came up, he did not even mention the name of Cees van Dongen, so how could anyone believe, that he is telling the truth now.

And second Frits lies about the sequence of his publications which you can see below.
So that's one more reason I don't believe he is honest in his latest reply.
When he had been honest from the start, I would give him the benefit of the doubt, but now I can't.
And why should that be different in other cases???


This is a passage from the text of FOS publication March 2008

Ideas only count when they are realized. That's why I would say, "Do your best, Luc.
Show how good the system is that you and I have thought independently of each other.

I hope my bike runs first. But if you are too quick for me, I hope that yours is running fast


And after 10 years Frits writes

By the way, that's the way the whole thing started.
At the end of 2007 and the beginning of 2008 I presented my scavenging idea in a racing newsletter and in a Dutch motorcycle magazine, accompanied by drawings and a picture of a cylinder that had clearly been running.
Luc, whom I had never heard of before, promptly launched a me-too reaction all over the internet.

He even claimed to have been the first with a running engine, because he posted a video while I had better things to do.




The first FST text was published on 19 january 2008.
2 month later on 16 March 2008 at 20.00hr the first FST engine was started in my home and my wife did make the movie on YouTube.
One day later Jan Thiel called me to congratulate me, that was close before he went to Thailand.
https://www.youtube.com/watch?gl=NL&hl=nl&v=jtTc7sk8WS8



Publication dec 2007 How the idea came up. No explanation how it works, No pictures of a cylinder, Nothing about Cees van Dongen!

https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 1;image
https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 3;image


Feb 21, 2008, two days after my publication on Jan 19, 2008
First picture of FOS only the underside of a cilinder, which he let publish by Martijn Stehouwer (nickname snel), No descriprion how it works.
http://www.kreidler.nl/forum/viewtopic.php?f=5&t=25485&start=25

https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 5;image


March 2008 First publication of the "FOS"systeem. Still no running engine with expansion pipes !
And even after 10 years no running "FOS" engine with expansion pipes !


https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 7;image
https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 9;image


I don't care who you believe but these are facts which nobody can ignore !

And there is more, he also lies about Ryger.
In an Italian magazine you can read that the Ryger idea came from Frits Overmars.
While he came to Ryger in 2014 to see how it worked.
He never added anything to the Ryger idea.
And I know because I have been involved in the project since 2008.
Here the original text:
l motore ollandese Ryger 125 revo deriva da un idea cviluppata da una decina d'anni da Frits Overmars, il primera sinistra nella foto.
Photo will follow later

My question is "are these the only few things he lies about ?"



.

[koenich]

I don't care who you believe
Obviously you do quite a lot :facepalm: Same as with the Ryger - mucho blabla to convince people of your amazing achievings. you have to be a great guy to hang out with...


16 mm is not so smal for a 50 cc !!!
I'm using 15 mm on my 50cc. Diameters below that value killed overrev, the engine was hard to jet and build up heat like crazy. So far I'm not sure if the increased backpressure is needed.

[F5 Dave]

Luc. You said you were leaving quite some time back. Please honour that commitment.

This isn't the thread to pollute with screes of, whatever it is argument it is that you think you're having.

Seriously. Piss off.

[dutchpower]

I'm using 15 mm on my 50cc. Diameters below that value killed overrev, the engine was hard to jet and build up heat like crazy. So far I'm not sure if the increased backpressure is needed.

0.646 kw more changing stinger

[mr bucketracer]

Here is the answer from William van Dongen



I know Cees van Dongen and his father from the past, I realy don't believe they only talked about one transfer under one exhaustduct.
When Frits published in dec 2017 how the idea came up, he did not even mention the name of Cees van Dongen, so how could anyone believe, that he is speaking the truth now.

And second he also lie about the sequence of his publications which you can see below.
So that's one more reason I don't believe he is honest in his latest reply.


This is a passage from his text of his publication March 2008

[/I][/B] And this he wrote now



Publication dec 2007 How the idea came up. No explanation how it works, No pictures of a cylinder, Nothing about Cees van Dongen!

https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 1;image
https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 3;image


Feb 21, 2008, two days after my publication on Jan 19, 2008 First publication of only the underside of a cilinder, which he let publish by Martijn Stehouwer (nickname snel), No descriprion how it works.
http://www.kreidler.nl/forum/viewtopic.php?f=5&t=25485&start=25
https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 5;image


March 2008 First publication of the "FOS"systeem

https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 7;image
https://www.deraceheldenvanweleer.nl/index.php?action=dlattach;topic=1987.0;attach=5851 9;image


I don't care who you believe but these are facts which nobody can ignore !this is all good stuff , thanks for sharing

[Muhr]

At last I've got all measurements of the ports in place! It's amazing how much time you need to get all angles and area in place.:wacko: Thank you Frits for the amazing library of pictures and drawings you posted on the RSA and RSW over the years.:2thumbsup

Does anyone have any tips or experience regarding the design such as wall thickness or the like?:wait:

[WilDun]

this is all good stuff , thanks for sharing

Mr B, - mate you could have said that easily with one line, we didn't need to have the whole bloody scenario all over again, once was enough!
I say put it all to rest and lets get on with the thread as it should be, it was going well! :yes:

Now go and answer MUHR's question!

[Muhr]

Obviously you do quite a lot :facepalm: Same as with the Ryger - mucho blabla to convince people of your amazing achievings. you have to be a great guy to hang out with...


I'm using 15 mm on my 50cc. Diameters below that value killed overrev, the engine was hard to jet and build up heat like crazy. So far I'm not sure if the increased backpressure is needed.

This is 14,7mm:facepalm:

[dutchpower]

This is 14,7mm:facepalm:

Yes smaller as 16 mm is worse

[chrisc]

This is 14,7mm:facepalm:

KTM SX? :blip:

[Muhr]

KTM SX? :blip:


No that piston i from a Malossi :yes:

[jonny quest]

Scooter friends. I have a 2001 Aprilia Ditech Morini. I'm looking for a big bore cylinder that has ability to go 50mm. 47mm is max off the shelf 70cc kit. I know I'll have to bore cases for bigger than 47mm.

Problem is I'll need a cylinder that a Ditech head will fit. Do you know of any cylinder that I could use?

[F5 Dave]

Mr B, - mate you could have said that easily with one line, we didn't need to have the whole bloody scenario all over again, once was enough!
I say put it all to rest and lets get on with the thread as it should be, it was going well! :yes:

Now go and answer MUHR's question!

Scott is just stirring, feeding the Troll its called. he doesn't care.

[mr bucketracer]

Scott is just stirring, feeding the Troll its called. he doesn't care.no , i like what he made , face it you all did , what the hell went wrong ?he never bought the rygar into this thread , you lot did , so what if it never made what it intended , face it he got it going , runs not to bad , with more work you never know , i thinkl shame on the lot of you the way you lot be carrying on . treat others the way you like to be treated !

[chrisc]

No that piston i from a Malossi :yes:

Thought that cylinder in the background was a KTM. Looks a lot like the (slow) engine project 50SX of mine.

[Fabio15]

Scooter friends. I have a 2001 Aprilia Ditech Morini. I'm looking for a big bore cylinder that has ability to go 50mm. 47mm is max off the shelf 70cc kit. I know I'll have to bore cases for bigger than 47mm.

Problem is I'll need a cylinder that a Ditech head will fit. Do you know of any cylinder that I could use?

To my knowledge there has never been a 100% bolt on solution for this. One could assume a non-ditech morini big bore kit of same vintage would be a good start.

I would scrap the morini and fit a minarelli or piaggii carb engine

[SwePatrick]

Does anyone have any tips or experience regarding the design such as wall thickness or the like?:wait:

It´s always good to have metal to grind in, that´s my advice =) (experience tells me that one is never happy with the porting)
One thing i would try is some coolingfins on exhaustduct to increase heat dispertion into the surrounding water.

rgds.

[Muhr]

It´s always good to have metal to grind in, that´s my advice =) (experience tells me that one is never happy with the porting)
One thing i would try is some coolingfins on exhaustduct to increase heat dispertion into the surrounding water.

rgds.

I tested to do a little different variants to the exhaust side but was questioning if the risk of film boiling was too big? is that something you have experience with?

[Muhr]

Thought that cylinder in the background was a KTM. Looks a lot like the (slow) engine project 50SX of mine.

You're right, a real sniper! Did not even notice it myself, but it's another project:niceone:

[lucf]

no , i like what he made , face it you all did , what the hell went wrong ?he never bought the rygar into this thread , you lot did , so what if it never made what it intended , face it he got it going , runs not to bad , with more work you never know , i thinkl shame on the lot of you the way you lot be carrying on . treat others the way you like to be treated !


Thanks mr Bucketracer, and for everyone to know Ryger has not finnished at all, it just has to start !
And I'm glad that there are still people who realy can read and not only bla..bla.. bla.... without reading well !

[SwePatrick]

I tested to do a little different variants to the exhaust side but was questioning if the risk of film boiling was too big? is that something you have experience with?

I don´t think it will boil as you run water quite low in temp if running on petrol, say 40-50 degree celcius maximum.
If having good circulation it will let eventual steam rise upwards and into radiator.
But, if you pressurise the coolingsystem with ~1bar you raise the boiling point to about 120-125c

With that said, boiling isn´t dangerous, it´s the shockwaves steam produces.

in other words, no problems ;)

[Muhr]

I don´t think it will boil as you run water quite low in temp if running on petrol, say 40-50 degree celcius maximum.
If having good circulation it will let eventual steam rise upwards and into radiator.
But, if you pressurise the coolingsystem with ~1bar you raise the boiling point to about 120-125c

With that said, boiling isn´t dangerous, it´s the shockwaves steam produces.

in other words, no problems ;)

I'm sorry but I think we're talking about different things I'm talking about film boiling the stage after nucleate boiling

[shnaggs]

Muhr, are you drawing this cylinder in Fusion 360? It looks like it from the pictures. I use Fusion 360 and have been trying to figure out how one goes about drawing a cylinder with all the passages the way you want them in that program. I'm not proficient (obviously) in CAD drawing, but its neat to see what you have done.

[SwePatrick]

I'm sorry but I think we're talking about different things I'm talking about film boiling the stage after nucleate boiling

You lost me... :(

[SwePatrick]

No..
I googled it.
It was just that i was writing about.
If you have this concern, how does car manufacturers solve this problen in the heads with far more heat in exhaust than a twostroke?

Think about it for a while ;)

[Larry Wiechman]

If you have this concern, how does car manufacturers solve this problen in the heads with far more heat in exhaust than a twostroke?



The modern trend is narrow coolant passages that promote high coolant velocity.

[Michael Moore]

I use Fusion 360 and have been trying to figure out how one goes about drawing a cylinder with all the passages the way you want them in that program.

I've not used Fusion 360 (I have Rhino and Alibre) but you might try modeling each passage individually then doing a Boolean subtraction from a large solid with each one. Remember to look for axes of symmetry that will let you draw a feature and then mirror it across the axis, reducing the amount you have to create.

cheers,
Michael

[SwePatrick]

The modern trend is narrow coolant passages that promote high coolant velocity.

And to get engine up to work temp as fast as possible to minimize pollution.

[diesel62]

Well that didn't work very well, only the most determined spikes got through. Maybe try again and amplify the original signal before running it through a bridge with the amp clipping the bigger signals to a max of 5 Volts for the Aduino digital input.



A small data logger, great idea. We use 4-20's at work, I will have to see if I can find a Voltage logger. Probable not ready for it yet as I don't have a decent signal, but it certainly makes sense. The loggers we use, typically multi channel and certified and run $2000+ so some pointers where to source something more affordable would be great.Hi these might be interesting to keep an eye on. https://www.pokitmeter.com/
Especially if you are mobile

Sent from my SM-P555 using Tapatalk

[TZ350]

Hi these might be interesting to keep an eye on. https://www.pokitmeter.com/

Thanks, they look great.

[diesel62]

Thanks, they look great.I have one ordered. Will let you know cheers

Sent from my SM-P555 using Tapatalk

[shnaggs]

I've not used Fusion 360 (I have Rhino and Alibre) but you might try modeling each passage individually then doing a Boolean subtraction from a large solid with each one. Remember to look for axes of symmetry that will let you draw a feature and then mirror it across the axis, reducing the amount you have to create.

cheers,
Michael


Thanks Michael,

I am pretty much a noob with this stuff, so bare with me. How would one go about actually modelling, say the A port of the RSA? I can do pretty easy stuff like, draw a shape as an entry to the port and then the same for the exit, and then create a loft to follow a spline curve, but that doesn't give me enough detail. would you just draw the cross section of the port ever few mm lets say, and then just loft that?

Thanks

[F5 Dave]

And to get engine up to work temp as fast as possible to minimize pollution.

To reduce the boundary layers to minimum. Water flow will shear through the middle path of least resistance. Drag as much away from the hot bit means less boundary insulation.

[Bert]

Well that didn't work very well, only the most determined spikes got through. Maybe try again and amplify the original signal before running it through a bridge with the amp clipping the bigger signals to a max of 5 Volts for the Aduino digital input.



A small data logger, great idea. We use 4-20's at work, I will have to see if I can find a Voltage logger. Probable not ready for it yet as I don't have a decent signal, but it certainly makes sense. The loggers we use, typically multi channel and certified and run $2000+ so some pointers where to source something more affordable would be great.

Give me a call on Monday afternoon Rob.
I’ll have a chat to our chief electronics engineer. We were playing with similar tech a few years (geophones); and constructed a cool amp system and high sampling rate data logger (there is likely to be some of the original dev boards in the workshop). From what you have descriped so far, I think these could be easily modded to suit you needs.

[TZ350]

Ok ... Thanks.

[Muhr]

No..
I googled it.
It was just that i was writing about.
If you have this concern, how does car manufacturers solve this problen in the heads with far more heat in exhaust than a twostroke?

Think about it for a while ;)

I will try to clarify what I'm aiming for.
If we think that the water rises from the crankcase quite close to the cylinder wall, then the flow of water will take the easiest way to the cylinder head, which means you will get a slightly reduced flow agents the exhaust flange. If I add cooling fins or do some small cavities between the bolt patterns of the flange then I wondered if the even more reduced flow along with the increased specific surface could cause it to start locally film boiling.
which would lead to a deterioration of cooling effect in that area.
And would mean less heat transported from the heat source and then a theoretically lower water temperature but less cooling at load peaks.

I am not saying that I am right but that was my question.


If you have this concern, how does car manufacturers solve this problen in the heads with far more heat in exhaust than a twostroke?
They think of such things I suppose

[Muhr]

Muhr, are you drawing this cylinder in Fusion 360? It looks like it from the pictures. I use Fusion 360 and have been trying to figure out how one goes about drawing a cylinder with all the passages the way you want them in that program. I'm not proficient (obviously) in CAD drawing, but its neat to see what you have done.

yes it's 360! However, my experience is very limited when I only used the program for 2 weeks. I have used other programs, so I'm not a total beginner.
I started myself with sketchup to get an understanding of the methodology. It's not as overwhelming at first and has many good exercise videos you can do. (and it free):2thumbsup

[Michael Moore]

I can do pretty easy stuff like, draw a shape as an entry to the port and then the same for the exit, and then create a loft to follow a spline curve, but that doesn't give me enough detail. would you just draw the cross section of the port ever few mm lets say, and then just loft that?

You are probably about where I am. If beginning and ending shapes lofted following a guide curve doesn't get you where you want to go then I guess you'd have to have some shapes in-between to loft to. And much of that will probably depend on the capabilities of your CAD software, whether you can loft with more than one guide curve etc.

Can you do a prismatic extrusion of the basic shape of the port in one direction and then use the outline of how you'd like things to look in a different axis to trim that, and then take that shape and fillet edges?

My guess is that whatever you can model is probably not exactly what you want, so you get close, cast and port it until you like it, pull a Vinamold or similar flexible casting from the port and then 3D scan the molding and then clean up the scan and work from that for the next iteration of the model.

cheers,
Michael

[Jannem]

So, revoking my foil hat project of trying a supersonic nozzle in the exaust.

It's been proven over and over by guys way beyond my level that a properly developed engine will make max. power when velocities are at .8mach, so why bother?

I don't have an access to engmod, but I recall from posts of others that sim may show benefits beyond .8, but that is where the reality sets in. I'm speculating this would be a product of non uniform velocity distribution in the nozzle, which is evident in a cfd picture posted here before. .8 mach may well be locally choked already.
Whether going above mach1 would give anything is also questionable from multitude of viewpoints, but #1 question is the inevitable mass flow limitation at nozzle choke. As it seems from the sims presented here, a highly tuned engine at full song may still have approximately 30% of it's blowdown port time area subsonic, so maybe there could be something.

To get an idea if this is an immediate failure or if there really could be something to be gained, I designed a nozzle, which should surely make the test engine visibly blowdown limited by the nozzle, but also go supersonic before that. Comparing that against the non-limited duct back-to-back ought to show if its just a brick wall situation, with power diving already at lower revs. The brick wall ought to be there when the port is sonic choked, but the interesting bit is before that.

As I don't own a lathe, I DIY'd a simple way to get area changes I wanted. The side benefit is to be able to test for the impact of uneven velocity distribution by 90deg rotation of the nozzle. For subsonic part of the cycle the horizontal orientation ought to be better, for supersonic, I have no idea.
As there are so many areas where possible claims of gains could be shot down by scratching the surface of my testing implementation, I wont be making any. And of course, if results show loss of power everywhere, then things are more straight forward.

So, here's the nozzle in the fitting phase with sliced pipe and the, not so beautiful, finished form.

[SwePatrick]

I will try to clarify what I'm aiming for.
If we think that the water rises from the crankcase quite close to the cylinder wall, then the flow of water will take the easiest way to the cylinder head, which means you will get a slightly reduced flow agents the exhaust flange. If I add cooling fins or do some small cavities between the bolt patterns of the flange then I wondered if the even more reduced flow along with the increased specific surface could cause it to start locally film boiling.
which would lead to a deterioration of cooling effect in that area.
And would mean less heat transported from the heat source and then a theoretically lower water temperature but less cooling at load peaks.

I am not saying that I am right but that was my question.


They think of such things I suppose

I actually think you are overthinking or overdeveloping, just make sure no air can be trapped and you´re good to go.
That´s what i have done in several carengines that i have tuned to about 1000hp, they have never shown any heatproblems even though materialthickness in heads were very thin after my portjob.
And they run closer to boiling and a lot hotter exhaustgasses, sometimes above 1000c, never been any problems.
But if air is trapped somewhere i have seen engineblocks crack due to steam shockwaves in those airpockets.

You also need to design waterpassages so the water flows evenly around every path.
This is often done with the headgasket.

If i look into my kawasaki cylinder, water inlet and outlet are on the same side of the barrel and head, rear against the carb.
Water goes into cylinder above the reedcase, then flows to the front, turns upwards through headgasket and flows rearwards in head to the outlet.
In gasket one can see it´s the same tech as in an car engine gasket.
It restricts flow at rear to control flow so it heads forwards in cylinder.
but,, it has holes in the rear to vent out airbubbles it there are any, just as in an carengine ;)

So, lead flow to every path with some finesse, and you´re good.

No need to think of boundarylayer etc etc boiling.
To minimize that if you are afraid of it you can add some additive in your coolant to lower surfacetension, the water becomes 'wetter'.
It actually works fine with soap ;)
But just a couple of drops if you don´t like suds ;)

[lohring]

I've not used Fusion 360 (I have Rhino and Alibre) but you might try modeling each passage individually then doing a Boolean subtraction from a large solid with each one. Remember to look for axes of symmetry that will let you draw a feature and then mirror it across the axis, reducing the amount you have to create.

cheers,
Michael
I'm also learning Fusion 360 to draw 2 stroke passages. What I've learned so far:

Don't use surface models (Patch) unless a solid model won't work.
If you use surfaces for passages you will need to use the split body command and then remove the piece you split off. Do that as the very last step.

Model the passages with solid lofts for both the inside and outside parts.
Use the combine feature as a cut to hollow out the part. Remember to turn off the parts you aren't working on.

Lofts like center lines. I can only suggest trial and error to see what lofts will work. Sharp bends will need more sketches to get through the curve, but the best passages I've designed only use a beginning and end sketch connected by a center line with the right curve.

Lohring Miller

[Muhr]

I actually think you are overthinking or overdeveloping, just make sure no air can be trapped and you´re good to go.
That´s what i have done in several carengines that i have tuned to about 1000hp, they have never shown any heatproblems even though materialthickness in heads were very thin after my portjob.
And they run closer to boiling and a lot hotter exhaustgasses, sometimes above 1000c, never been any problems.
But if air is trapped somewhere i have seen engineblocks crack due to steam shockwaves in those airpockets.

You also need to design waterpassages so the water flows evenly around every path.
This is often done with the headgasket.

If i look into my kawasaki cylinder, water inlet and outlet are on the same side of the barrel and head, rear against the carb.
Water goes into cylinder above the reedcase, then flows to the front, turns upwards through headgasket and flows rearwards in head to the outlet.
In gasket one can see it´s the same tech as in an car engine gasket.
It restricts flow at rear to control flow so it heads forwards in cylinder.
but,, it has holes in the rear to vent out airbubbles it there are any, just as in an carengine ;)

So, lead flow to every path with some finesse, and you´re good.

No need to think of boundarylayer etc etc boiling.
To minimize that if you are afraid of it you can add some additive in your coolant to lower surfacetension, the water becomes 'wetter'.
It actually works fine with soap ;)
But just a couple of drops if you don´t like suds ;)

I took the opportunity to ventilate the issue to a close friend who is one of the people in charge of engine block at Volvo and he estimated that about 70% of the total development time, is flow optimising on cooling to prevent film boiling.

I think you have a lot to learn the automotive industry!:niceone:

http://publications.lib.chalmers.se/records/fulltext/207401/207401.pdf

[TZ350]

cooling to prevent film boiling.

When I was doing a lot of engine reconditioning work we used to get engines with wet liners that had pin holes right through them.

The culprit seemed to be localized cavitation, a bubble would form on the liner surface then collapse. This happened often enough in the same place that the resulting water hammer against the liner would eventually eroded a hole through it.

I thought it was localized boiling but it is apparently a result of cylinder wall flexing.

https://www.cumminsfiltration.com/sites/default/files/pdf_archive/pdfs/product_lit/asia_pacific_brochures/3300963A.pdf

http://www.emestlab.com/lab/Portals/0/Papers/KOKA001.pdf

A blurb that might be interesting about Evans water-less coolants, no local boiling.

http://www.evanscoolants-uae.com/technical/no-water-no-problems/72

[Haufen]

Does anyone have any tips or experience regarding the design such as wall thickness or the like?:wait:

I guess so. A bit more information on your cylinder would be helpful. Displacement? Bore? Performance / BMEP you aim at? From the pictures, it looks about right.
Personally, when designing a new cylinder, I'd never start with the final exhaust port timing right away as it can easily be too much already to start with. Adjusting in small steps on the dyno makes it much easier to hit the sweet spot. And you can learn a lot from it.


I will try to clarify what I'm aiming for.
If we think that the water rises from the crankcase quite close to the cylinder wall, then the flow of water will take the easiest way to the cylinder head, which means you will get a slightly reduced flow agents the exhaust flange. If I add cooling fins or do some small cavities between the bolt patterns of the flange then I wondered if the even more reduced flow along with the increased specific surface could cause it to start locally film boiling.
which would lead to a deterioration of cooling effect in that area.
And would mean less heat transported from the heat source and then a theoretically lower water temperature but less cooling at load peaks.

I am not saying that I am right but that was my question.


They think of such things I suppose


Nowadays, gasoline car engines often come with a cooled exhaust gas passage. This not only speeds up engine warm up, it also allows them to keep exhaust gas temperatures low enough to run lambda 1 within a wider area in the engine map. Of course, this needs some serious simulation work before it can hit the market.

334941

Nevertheless, comparing car engines with two-stroke engines in regards of boiling risk is comparing apples with oranges. On car engines, the coolant enters the engine with 90°C and exits with an average temperature of 110°C or so, whereas on a two-stroke you enter with 40°C and if you exit with 60°C that would already be quite much. So the delta temperature between average temperature of the coolant and the temperature needed for local film boiling is much much larger on the two-stroke, hence this problem is much less likely to occur. If you just take care that there are no areas of dead flow and install a cooling system which allows you to run at two-stroke ideal (low) coolant temperarures, you should be fine.

On the other hand, as you are designing your cylinder yourself, you can already implement a nice coolant flow path through your cylinder which keeps every area nicely cooled and has no dead areas. On the RSA, part of this is achieved through coolant openings of varying sizes in the cylinder head in order to direct the bulk flow where you want it to go. And there are tiny holes to allow for venting of bubbles in the direct (mostly blocked) part (as described by SwePatrick).

[Muhr]

I guess so. A bit more information on your cylinder would be helpful. Displacement? Bore? Performance / BMEP you aim at? From the pictures, it looks about right.
Personally, when designing a new cylinder, I'd never start with the final exhaust port timing right away as it can easily be too much already to start with. Adjusting in small steps on the dyno makes it much easier to hit the sweet spot. And you can learn a lot from it.

Thank you! Who does not want a hand on his shoulder:yes:
it is a 40 borr/stroke
50,265cc
BMEP 205.7 psi

i am 15% under calculated area on exhaust .

[Muhr]

On the other hand, as you are designing your cylinder yourself, you can already implement a nice coolant flow path through your cylinder which keeps every area nicely cooled and has no dead areas. On the RSA, part of this is achieved through coolant openings of varying sizes in the cylinder head in order to direct the bulk flow where you want it to go

Yes, that was a bit so I thought, why not do well when you can.
I will not be able to make full sim on the flow before the summer just static

[Muhr]

I'm also learning Fusion 360 to draw 2 stroke passages. What I've learned so far:

Don't use surface models (Patch) unless a solid model won't work.
If you use surfaces for passages you will need to use the split body command and then remove the piece you split off. Do that as the very last step.

Model the passages with solid lofts for both the inside and outside parts.
Use the combine feature as a cut to hollow out the part. Remember to turn off the parts you aren't working on.

Lofts like center lines. I can only suggest trial and error to see what lofts will work. Sharp bends will need more sketches to get through the curve, but the best passages I've designed only use a beginning and end sketch connected by a center line with the right curve.

Lohring Miller

Loft i great for exhaust design! you may need to do some 3D sketching witch can be a bit tricky. For transfer ports i recommend using revolving! get a straight over and underside with the correct angles whit loft can be a nightmare.
expect a lot of error 40:sweatdrop

[Frits Overmars]

engmod.. may show benefits beyond .8 .... I'm speculating this would be a product of non uniform velocity distribution in the nozzle.... .8 mach may well be locally choked already.Correct.


#1 question is the inevitable mass flow limitation at nozzle choke.It's my pleasure to get that # 1 question out of the way then: there is no mass flow limitation. When the ratio between upstream pressure and downstream pressure reaches a value of about 2, flow velocity will reach Mach 1. Lowering the downstream pressure any further will not raise the flow velocity any further.
Raising the upstream pressure won't raise the flow velocity any further either, but it will increase the density of the flowing medium, so even when the flow velocity remains the same, increasing the upstream pressure will increase the mass flow.
The picture with the nice colours below shows how at the beginning of exhaust port opening, the flow tries to cling to the exhaust duct ceiling, using it as a nozzle. The exhaust duct floor is too far away to help create a full nozzle, but that temporary half-nozzle at the ceiling is worth thinking about. How can we encourage that?
That's why I'm in favour of a radiused top edge on the exhaust port and a radiused piston top edge. It may not prevent a whole lot of energy loss, but every bit helps.
334948 334947

[190mech]

" That's why I'm in favour of a radiused top edge on the exhaust port and a radiused piston top edge. It may not prevent a whole lot of energy loss, but every bit helps."

Frits,Would not a radius on the piston edge create a void in the squish area promoting detonation?Would a custom combustion chamber need to be made to match the piston edge at the exhaust side?I'm sure we'll need to maintain a sharp edge on the piston dome at the transfer ducts to promote piston cooling also..

[katinas]

" That's why I'm in favour of a radiused top edge on the exhaust port and a radiused piston top edge. It may not prevent a whole lot of energy loss, but every bit helps."

I'm sure we'll need to maintain a sharp edge on the piston dome at the transfer ducts to promote piston cooling also..

and maybe sharp edges on the piston dome and on transfers windows help to resist little, when exhaust gas enter to transfers.

[Frits Overmars]

Would a custom combustion chamber need to be made to match the piston edge...Obviously. But that is true for all piston shapes. And as the piston edge is radiused all-around, matching the combustion chamber to it is a piece of cake.


I'm sure we'll need to maintain a sharp edge on the piston dome at the transfer ducts to promote piston cooling also..How do you figure that? A radiused piston timing edge at the transfer ports greatly promotes flow attachement to the piston dome, which does wonders for both the flow coefficient and the piston cooling.
334949


and maybe sharp edge on the piston dome and on transfers windows help to resist little, when exhaust gas enter to transfers.Flow from the cylinder into the transfers must of course be discouraged, so the top edges on the transfer windows must indeed be sharp. But a radiused piston top edge has very little influence on flow in that unwanted direction.
The nozzle effect that we hoped to achieve at exhaust opening, does not play a role at transfer opening because, even if the blowdown time.area has been insufficient and the cylinder pressure is still higher than the pressure in the transfer ducts, the pressure ratio will be subcritical, so the flow will be subsonic.
The benefits of a radiused piston top edge for better transfer flow into the cylinder and better piston cooling are far more important.

[Jannem]

It's my pleasure to get that # 1 question out of the way then: there is no mass flow limitation.

:facepalm::yes: One down.



The picture with the nice colours below shows how at the beginning of exhaust port opening, the flow tries to cling to the exhaust duct ceiling, using it as a nozzle. The exhaust duct floor is too far away to help create a full nozzle, but that temporary half-nozzle at the ceiling is worth thinking about. How can we encourage that?
That's why I'm in favour of a radiused top edge on the exhaust port and a radiused piston top edge. It may not prevent a whole lot of energy loss, but every bit helps.
334948
That makes me want to try another, perhaps a bit oddball porting idea in addition to the radius.

[Frits Overmars]

That makes me want to try another, perhaps a bit oddball porting idea in addition to the radius.Keep 'm coming Jannem :D.
334950

[lohring]

Loft i great for exhaust design! you may need to do some 3D sketching witch can be a bit tricky. For transfer ports i recommend using revolving! get a straight over and underside with the correct angles whit loft can be a nightmare.
expect a lot of error 40:sweatdrop

That's a really great hint. Thanks, I'll try it on the Aprilia clone cylinder that's my next Fusion 360 project.

Lohring Miller

[Muhr]

I got mail from som members about if it passable to by a cylinder. The short answer is no, the long answer is that I make these cylinders to an engine I have drawn and will not fit any other engine. If it turns out that the cylinder works well and there will be a cylinder over, then we'll look at it. This is supposed to be a hobby project.:yes:

i got a question if te bolt pattern is the same as SX i attached a picture


When I was doing a lot of engine reconditioning work we used to get engines with wet liners that had pin holes right through them.

The culprit seemed to be localized cavitation, a bubble would form on the liner surface then collapse. This happened often enough in the same place that the resulting water hammer against the liner would eventually eroded a hole through it.

I thought it was localized boiling but it is apparently a result of cylinder wall flexing.


Interesting reading!

[Greg85]

Hey guys!

I found some nsr500 engine pics! http://www.geocities.jp/noda_keni/h/00nsr500/00nsr500.htm

hello would anyone have any pictures or info on the reed valve honda nsr 500gp thanks

[Muciek]

On honda nsr forum there are threads with 500 v2 , guys were restoring them to track condition. There were pictures of reeds cylinders ect , but for the 4 cyl I don't think theres much more than You could find here in Husaberg galleries.

[JanBros]

Wobbly, some pipe questions if I may :


End of header is always 31 to 33% and end of diffuser is always 62 to 68%.
a 2 stage header with something like 3.5/5.5* for 2/3 - 1/3 lengths from the piston

your header angles seem more steep than any other, is this beacause your spigot/exhaust duct is longer than simply bolting the exhaust directly to the cylinder and that it takes away length from the 31 to 33% header length, so the angles need to be steeper to arrive at the correct diameter and the end of the header ?

and do you have any suggestions about percentages for diffuser lengths when using a 3-stage diffuser with the steepest stage in the middle ? for the Aprilia tubo 102 it seems to be +/- 25/58/17%


Three angle rear cones were a legacy design that Jan was forced to use, as Frits explained.
But it is a long time issue for me that so often a sim will be strongly telling me that the system works well ( and it annoys Neels as well I know ) but in reality I have never been able to get more power on the dyno
than a 14* straight tailcone - believe me I have waisted so much time on this, and have given up.

when "always" using a 14° rear cone, do you adjust the total length of the pipe somewhere to get it back in line with the needed length, or do you simply "calculate" the total length, and then just stick a 14° cone at the back for all the reasons you mentionned before ?

[lodgernz]

How do you figure that? A radiused piston timing edge at the transfer ports greatly promotes flow attachement to the piston dome, which does wonders for both the flow coefficient and the piston cooling.
334949

A radiused piston edge makes port opening determination more difficult. The 45º wire trick won't work. I suppose it could be done with 80º wire if the radius was an accurate 20º to the piston face.
Any better ideas?

[wobbly]

The 3.5/5.5 header angles came into being simply because so many engines liked that combination.
But be wary of monkey see monkey do.
The end result is always project specific, as I have just completed my TM KZ10D pipe and that ended up with 25% header and 2.1/3.1*.
This was due to a large step up from the cylinder exit to the header entry, and it made more power with a steeper first diffuser section and the less steep headers..
Just to confuse the issue even more - this is the first application where the 3 angle rear cone has made a significant gain over the existing ( two angle ).
The C model had 29.73 and 31.64 ( about 50/50 length ) the 3 cone has 28.61- 30.95-33.29 and this made a heap of overev power, plus a little more going up
to the same peak number ( where the engine drops back to after a gearchange ).
But going back,the steeper header angles work well on " most " high performance engines, just not the kart engine that is really only used between 10500 and 14500 all day.

[JanBros]

tnx, allthough part of my question was 3-stage diffuser, not the baffle.

[wobbly]

The Aprilia pipes were not that clever, in that Jan had a devil of a time making them work.
This isnt the correct way to do things, ie make a compromised pipe, then be as clever as all hell with the porting to make that pipe work.
If you reverse the % you quoted, to something like 17/59/24% then the steepest diffuser section can become the last, and this is superior in every way for
a very high specific output engine at very high rpm.

[nitro2tfx]

When the ratio between upstream pressure and downstream pressure reaches a value of about 2, flow velocity will reach Mach 1. Lowering the downstream pressure any further will not raise the flow velocity any further.

There is one little extra tidbit that goes with this, that isn't well known. As mentioned when the pressure ratio between the upstream and downstream reaches about 2 the flow velocity reaches Mach 1 and as such the flow velocity can't go any greater by lowering the downstream pressure, and it is generally assumed from that, that the massflow can't go any higher by lowering the downstream pressure.

Seems logical of course, BUT it is only true for certain shapes such as a nice bell mouth entrance etc. When less favorable shapes are used, an orifice being one example (but certainly not the only example), the massflow can be increased by lowering the downstream pressure below the critical Mach 1 ratio. Mach 1 is never exceeded, but the unfavorable flowpath of the unfavorable shape, improves as the pressure is lowered further, causing the massflow to increase. Most flow paths in an engine are not as bad as an orifice, but not as good as a bell mouth either, so there is some wiggle room here and there regarding the massflow vs. upstream to downstream pressure ratio.

[philou]

A normal exhaust pipe to this form :

http://www.kirikoo.net/images/7philou-20180129-081749.jpg

some exhaust pipe have this shape :

http://www.kirikoo.net/images/7philou-20180129-081834.jpg

Does the shape affect the operation of the exhaust pipe ?

[Jannem]

A normal exhaust pipe to this form :

http://www.kirikoo.net/images/7philou-20180129-081749.jpg

some exhaust pipe have this shape :

http://www.kirikoo.net/images/7philou-20180129-081834.jpg

Does the shape affect the operation of the exhaust pipe ?

The lower one certainly is worse from the pressure recovery viewpoint. Flow is going to hug the header short side and head towards stinger, leading to more separation in the one-sided more abrupt diffuser part.
From the wave tuning perspective, I doubt there's much difference. If you consider the actual through flow can be squeezed out from the stinger, the difference in flow efficiency may be mainly theoretical.

So, whether it makes a difference in the real world, I'll leave the experts with practical experience to comment