ESE's works engine tuner

[Frits Overmars]

I see a clear similarity between your engine with its central carburettor and two rotary inlet discs, and the East German Trabant.
I wonder which of the two came first.

[katinas]

This engine was definitely a copy of Konig, perhaps pre war technology. Konig stop produce this engine in 1963 in West Germany, Bихрь started in 1966.
Just last week I saw working Trabant engine on an small wing plane and helped to adapt scooter 28 mm carb. With propeller engine revs to 3900 rpm.

The best and most racing-oriented Soviet two-stroke mass-produced engine, was the outboard Privet ( Hello) 350. Two cylinder 62x58mm, two disc valve, steel piston rings, separate cylinders ( at factory tried chrome or nicasil ) small end roller bearing . When the fist time see this engine, cant believed how race look all things was (photo with red flywheel and scheme)
Engine was produced from 1973 to 1982. Before mass production, five years engine was tested in boat race from 1969.

[Condyn]

Hi, new to the forum and if IÂ’m posting in the wrong thread, off with my head I guess.

I have a question about pipe design. IÂ’ve designed and built about a dozen pipes at this point and am starting to get a grasp on things. I recently had an idea... From what IÂ’ve gathered raising the compression ratio will make a given pipe act longer due to more of the energy being taken by the engine and the speed of sound travels slower through a colder gas.
I’ll be using this engine/pipes for 660 foot (in the fortnighthunderweight system or whatever Frits calls it, that we use in the states) drag racing on frozen lakes, with a cvt drive. Ice is readily available, and no ignition retards are allowed for pipe heating. I’m using very large D-max FOS based pipes and “everyone” seems to think they will take ages to build heat. I know they work well at sucking what’s left on higher compression engines, but “everyone’s” concerns got me thinking about doing things a little differently.


My question is:
Since itÂ’s a short drag run and ignition retard devices arenÂ’t allowed, what are your thoughts about icing down the pipes to a baseline temp before each pass and dropping the speed of sound (effectively shortening the pipe) until I make peak power at the same rpm as if I were preheating the pipe? I usually like testing things in real life instead of standing around munching on regular Cheetos, whilst thinking about trying the flamin hot version when I become brave enough. Is this a pipe dream (pun not intended) or could it work?

[Frits Overmars]

]From what IÂ’ve gathered raising the compression ratio will make a given pipe act longer due to more of the energy being taken by the engine and the speed of sound travels slower through a colder gas.
I’ll be using this engine/pipes for 660 foot (in the fortnighthunderweight system or whatever Frits calls it, that we use in the states) drag racing on frozen lakes, with a cvt drive. Ice is readily available, and no ignition retards are allowed for pipe heating. I’m using very large D-max FOS based pipes and “everyone” seems to think they will take ages to build heat. I know they work well at sucking what’s left on higher compression engines, but “everyone’s” concerns got me thinking about doing things a little differently.
My question is:
Since itÂ’s a short drag run and ignition retard devices arenÂ’t allowed, what are your thoughts about icing down the pipes to a baseline temp before each pass and dropping the speed of sound (effectively shortening the pipe) until I make peak power at the same rpm as if I were preheating the pipe?.... Is this a pipe dream (pun not intended) or could it work?

Hi Condyn, icing down the pipes to a baseline temp before each pass and dropping the speed of sound would effectively lengthen, not shorten the pipe.
What would it bring? During your run the pipe temp would rise and the pipe would behave as if it was tromboning from long to short, shifting the complete power curve from low to high revs. But a pipe that wasn't pre-iced would do that too, only with higher initial and final temperatures.
Please note that the colder a pipe, the more energy it will steal from the exhaust gases inside, which is not desirable.

I have heard people say before that fat pipes will take ages to build heat. That is true for two reasons. First, there simply is more steel to be heated (which could be a reason for using stainless or titanium sheet that have lower specific heats).
The second reason is more interesting: fat pipes have a bigger volume to wall surface ratio, which means that less of the exhaust gas comes into contact with the pipe walls. And that's fine: the pipe will not heat up so quickly, but it will also steal less heat from the gas, so while the pipe may be colder, the gas will be hotter. At the end of the day it may be colder because of the larger expansion factor in the fat diffuser, but this awards us with more suction.
Finally, I wonder: with a good clutch and CVT setup you will always want maximum power at the same revs, from start to finish, so you don't really want the pipe temperature to climb during a run, do you?
PS: never say a good pun was not intended. If people get the impression that you're brilliant, don't take that away from them

[Vannik]

For those interested in turbocharging a 2T:

https://www.snowmobile.com/trails/po...e-engine-65385

It seems Polaris has filed for 9 patents.

[Condyn]

Edited due to double post, sorry ��

[Condyn]

Hi Condyn, icing down the pipes to a baseline temp before each pass and dropping the speed of sound would effectively lengthen, not shorten the pipe.
What would it bring? During your run the pipe temp would rise and the pipe would behave as if it was tromboning from long to short, shifting the complete power curve from low to high revs. But a pipe that wasn't pre-iced would do that too, only with higher initial and final temperatures.
Please note that the colder a pipe, the more energy it will steal from the exhaust gases inside, which is not desirable.

I have heard people say before that fat pipes will take ages to build heat. That is true for two reasons. First, there simply is more steel to be heated (which could be a reason for using stainless or titanium sheet that have lower specific heats).
The second reason is more interesting: fat pipes have a bigger volume to wall surface ratio, which means that less of the exhaust gas comes into contact with the pipe walls. And that's fine: the pipe will not heat up so quickly, but it will also steal less heat from the gas, so while the pipe may be colder, the gas will be hotter. At the end of the day it may be colder because of the larger expansion factor in the fat diffuser, but this awards us with more suction.
Finally, I wonder: with a good clutch and CVT setup you will always want maximum power at the same revs, from start to finish, so you don't really want the pipe temperature to climb during a run, do you?
PS: never say a good pun was not intended. If people get the impression that you're brilliant, don't take that away from them

Thank you for the insight Frits. When I said drop the speed of sound, I meant in the design process with anticipation of icing down the pipes. Since the sound travels slower through a slow gas, we would need to shorten the TL to compensate for the temp drop right? But you say the cold pipe will rob energy, and that makes sense. Maybe I should stick to conventional methods. As for the CVT, we run a primary and a secondary clutch that operate on Low ratio/high ratio curves. Shift speed is set to say 9,000 rpm and belt engagement is
say 6,000 rpm. Once we are at shiftout speed the goal is to maintain this speed as a straight shift. This transition takes time, so if done properly, I am curious if the tromboning effect could be beneficial as the pipe heats.

[Frits Overmars]

Thank you for the insight Frits. When I said drop the speed of sound, I meant in the design process with anticipation of icing down the pipes. Since the sound travels slower through a slow gas, we would need to shorten the TL to compensate for the temp drop right? But you say the cold pipe will rob energy, and that makes sense. Maybe I should stick to conventional methods. As for the CVT, we run a primary and a secondary clutch that operate on Low ratio/high ratio curves. Shift speed is set to say 9,000 rpm and belt engagement is say 6,000 rpm. Once we are at shiftout speed the goal is to maintain this speed as a straight shift. This transition takes time, so if done properly, I am curious if the tromboning effect could be beneficial as the pipe heats.

I see what you meant by shortening the tuned length in the design proces.
Why are the engagements revs of the belt and the clutch so far apart, with the second rpm at 150% of the first rpm? Such a wide spread is asking a lot of the engine.
Surely a decent CVT can do better than that?
I would ask you to enlighten me with a sketch of your transmission layout but as you're new here, I'm afraid that you have not yet acquired the privilege to post pictures;
that seems to take some time on this forum.

[polcat88]

I will give it a shot Frits. The video shows the conventional snowmobile clutching setup being driven by an electric motor for demonstration purposes. In a snowmobile, the secondary clutch drives a jackshaft connected to a chaincase on the opposite end. In Condyn's example the drive clutch would engage the belt at 6000 RPM. In drag racing, this engine's RPM would be held around 5600 to 5800 RPM while staged and waiting for the light to change. When the light changes and full throttle is applied, if the clutches are tuned correctly, the engine RPM will flash very quickly to the desired power peak of 9000 RPM and hold that RPM for the complete length of the run, be it 500, 660 or 1320 feet.

[wobbly]

Two points re pipe design and CVT.
Firstly is that " fat " pipes are only effective on porting layouts that have good transfer duct geometry , and good radial port geometry.
If the ducts are not " teacup " and the most important A port front wall is not pointing back to just in front of the boost port , then the efficient diffuser section easily overcomes
the transfer stream coherency , giving huge short circuiting directly out the Exhaust duct.
This makes the jetting appear rich , but in actuality the mixture within the cylinder may be burning at near optimum temperature.Lean this scenario down at your peril.
A good example being a TZ350 that will simply refuse to make more power with anything past 110mm belly diameter

Secondly , the clutching setup.
As Frits alluded to , the clutching setup seems at odds with keeping the engine at peak power continuously.
My experience with CVT is nill , but for many years we raced KT100 Yamaha with centrifical clutches and specially designed pipes to make alot of power over a narrow range.
In this scenario the fastest setup was to have the clutch springs and weights " just lockup ", and allow the engine to sit at peak torque rpm under full load.
Then from this start point , the gearing was selected to give peak speed just as it dropped over peak Hp.
The clutch lockup rpm was critical to within 100rpm and was typically 10400 rpm , and the pipe was over the top at just past 14,000.

[Condyn]

I see what you meant by shortening the tuned length in the design proces.
Why are the engagements revs of the belt and the clutch so far apart, with the second rpm at 150% of the first rpm? Such a wide spread is asking a lot of the engine.
Surely a decent CVT can do better than that?
I would ask you to enlighten me with a sketch of your transmission layout but as you're new here, I'm afraid that you have not yet acquired the privilege to post pictures;
that seems to take some time on this forum.

I hope my photo attachments work. I am still learning how to use this highly resourceful forum. The engine does reach shift speed or (peak power rpm) relatively quick, so I somewhat amend my original statement. However, there is a period where the engine speed climbs in low ratio ratio before this occurs.

[Frits Overmars]

I will give it a shot Frits. The video shows the conventional snowmobile clutching setup being driven by an electric motor for demonstration purposes. In a snowmobile, the secondary clutch drives a jackshaft connected to a chaincase on the opposite end. In Condyn's example the drive clutch would engage the belt at 6000 RPM. In drag racing, this engine's RPM would be held around 5600 to 5800 RPM while staged and waiting for the light to change. When the light changes and full throttle is applied, if the clutches are tuned correctly, the engine RPM will flash very quickly to the desired power peak of 9000 RPM and hold that RPM for the complete length of the run, be it 500, 660 or 1320 feet.

Thanks Polcat. The CVT systems I am familiar with, have only one clutch, and I could not imagine a system with a primary and a secondary clutch.
Your video made it all clear: there still is only one clutch, and a crude one at that: nothing more than the primary pulley sheaves pinching the belt.
The secondary clutch is not a clutch at all; it's just another pulley, pinching the belt via an axial spring and a torque ramp. The torque ramp has the effect of reducing its pinching force when torque is reduced, which results in the CVT "shifting up" and reducing engine rpm when you go off the throttle, just what the average user expects.

I used to advise scooter tuners to fit a stronger spring and omit the torque ramp for racing, so engine rpm remains constant all the time and throttle response is more direct.
It worked fine, but it took some getting used to: scooter riders tend to open the throttle quite early on corner exit, to compensate for the fact that it will take a few tenths of a second for the CVT to "shift down" and start feeding power to the tire. With my mod they tended to open the throttle a few tenths of a second too early .


The video below shows a 125cc scooter (not mine) bantering a fleet of 1000cc superbikes with proper throttle response out of corners. Granted, it's hardly a superbike track, but it will make you understand why I would have applied CVT to GP-bikes ages ago, but for the rule that they are not allowed to have more than six gears.
https://www.youtube.com/watch?v=EFjakgypqSs

[Condyn]

Two points re pipe design and CVT.
Firstly is that " fat " pipes are only effective on porting layouts that have good transfer duct geometry , and good radial port geometry.
If the ducts are not " teacup " and the most important A port front wall is not pointing back to just in front of the boost port , then the efficient diffuser section easily overcomes
the transfer stream coherency , giving huge short circuiting directly out the Exhaust duct.
This makes the jetting appear rich , but in actuality the mixture within the cylinder may be burning at near optimum temperature.Lean this scenario down at your peril.
A good example being a TZ350 that will simply refuse to make more power with anything past 110mm belly diameter

Secondly , the clutching setup.
As Frits alluded to , the clutching setup seems at odds with keeping the engine at peak power continuously.
My experience with CVT is nill , but for many years we raced KT100 Yamaha with centrifical clutches and specially designed pipes to make alot of power over a narrow range.
In this scenario the fastest setup was to have the clutch springs and weights " just lockup ", and allow the engine to sit at peak torque rpm under full load.
Then from this start point , the gearing was selected to give peak speed just as it dropped over peak Hp.
The clutch lockup rpm was critical to within 100rpm and was typically 10400 rpm , and the pipe was over the top at just past 14,000.

Thank you for your time wobbly. Firstly I want to acknowledge that fact that I know what the FOS pipe design was targeted for. I know it is not a one size fits all design template. This pipe has a 150mm belly diameter, and since it’s a parallel twin engine with tight bore spacing you can guess what the transfer ducts look like. As for the false positive rich condition, I thank you for making that aware as I would not have picked that up quick. These engines run a large single exhaust port and no rear boost port. Another issue that comes to mind is the exhaust duration is 200°. With a large diffuser pulling on the transfer stream with a high duration exhaust port, what’s being trapped? I am starting to see the picture... since the pipes are already built, I think it’s only fair to test them anyway. Although probably not ideal, could I just scale the diameters down and give that a go? I really should give ENGmod2t a go. The cvt design is similar to what you talk about. It is held on its power peak shift speed almost the entire run, besides the point where the engine speed is accelerating in low ratio after engagement. I included a photo of the fat pipes built. The team I donated them to for testing insisted the baffle and stinger be the same diameter. I also included some attachments in my comment back to Frits on the cvt. Thank you again for your time.

[Frits Overmars]

The engine does reach shift speed or (peak power rpm) relatively quick, so I somewhat amend my original statement. However, there is a period where the engine speed climbs in low ratio ratio before this occurs.

Condyn, I see that the "clutch" starts closing between 5000 and 6000 rpm. Seeing the way the CVT is set up, we may assume that maximum power is produced at 9000 rpm. Then the torque dip at 2/3 of max. power will be around 6000 rpm, right where the clutch closes, and by the looks of it your engine has no exhaust power valves, so the sled has to build up speed from zero to around 20 mph, starting with nearly zero power. That will take forever! Not the best way to start a drag race...
Why not lighten the centrifugal weights on the clutch a bit, so it bites later? It may reduce belt life, but it will also reduce your 0-to-660 ft time, won't it?

[jonny quest]

It's not just the mass of the weights in the primary clutch. They are swinging weights with a ramp design. The placement of the mass in the weights along with the ramp profile are huge tuning tools. Not to mention roller diameter and roller orientation to the weights.

Traction is a problem, and the reason you can't just engage clutch at 9000 rpm and go. It needs the highest engagement possible without breaking traction.