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Thread: ESE's works engine tuner

  1. #33946
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    20th June 2020 - 07:10
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    Quote Originally Posted by Frits Overmars View Post
    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. 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 feet time, won't it?
    Attachment 346217
    If we engage later we spin. A good racer examines the track multiple times throughout the day and determines where his clutch should come in. As noted by Jonny Quest there is a multitude of tuning variables that come into play with the cvt that we use. Ice is brittle so we dont just hook up and go all the time. I have changed engagement speed several times throughout a day as the top layer of ice deteriorates. Note the ice roost in photo. Many of these engines are well over 200hp
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  2. #33947
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    Quote Originally Posted by Condyn View Post
    Ice is brittle so we dont just hook up and go all the time. I have changed engagement speed several times throughout a day as the top layer of ice deteriorates.
    That is where I went wrong. I have some experience with ice speedway (I helped design the chassis in the picture below left) and their grip coefficient is phenomenal:
    over twice the grip of a MotoGP bike, as is demonstrated by their lean angles.
    I assumed that you would have the same amount of grip on your sled. But you seem to use tracks without spikes, or at least without the vicious toothpicks of the bikes.
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  3. #33948
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    8th February 2007 - 20:42
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    The 200* Ex Duration is common for many twins with a single pipe.This allows the single pipe to work much more effectively.
    But swapping to twin pipes I would urge you to have a go at re arranging the port layout to reduce the Ex height.
    This worked very well in SeaDoo World Champ class engines when swapping to big twin pipes , but the transfers needed a heap of grinding to get a match to the diffuser efficiency.
    Maybe the high port works in your favour though, stopping the big rush of torque from spinning up the drive too quickly ( early ) and loosing traction.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  4. #33949
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    5th April 2013 - 13:09
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    Snowmobiles do use ice picks, but the traction is just not the same as a motorcycle.

    I believe a wheel drives spikes into ice. A snowmobile track flexes and because ice gets so chewed up the rubber track is sitting on ice and prevents full bite of picks, where a motorcycle is solely riding on picks

    Quote Originally Posted by Frits Overmars View Post
    That is where I went wrong. I have some experience with ice speedway (I helped design the chassis in the picture below left) and their grip coefficient is phenomenal:
    over twice the grip of a MotoGP bike, as is demonstrated by their lean angles.
    I assumed that you would have the same amount of grip on your sled. But you seem to use tracks without spikes, or at least without the vicious toothpicks of the bikes.
    Click image for larger version. 

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  5. #33950
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    25th March 2004 - 17:22
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    Golly its a whole new world this icey stuff. I was going to ask if you can tap the back door, so to speak, and connect a boost port. But I think there will be some crazy reasons I can't fathom.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  6. #33951
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    2nd March 2013 - 15:04
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  7. #33952
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    Quote Originally Posted by Frits Overmars View Post
    I have some experience with ice speedway (I helped design the chassis in the picture below left) and their grip coefficient is phenomenal:
    over twice the grip of a MotoGP bike, as is demonstrated by their lean angles.
    Frits, what a lubrication system is used these days on the speedway engines (Jawa , GM). Stihl 4-mix use total loss oil scheme on 4t.
    https://www.youtube.com/watch?v=NhprB_OOrLQ

    I finally found that the Aaen engine was designed for speedway
    https://cybermotorcycle.com/archives...bikes/aaen.htm
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  8. #33953
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    26th April 2013 - 21:55
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    Quote Originally Posted by katinas View Post
    Frits, what a lubrication system is used these days on the speedway engines (Jawa , GM). Stihl 4-mix use total loss oil scheme on 4t.
    https://www.youtube.com/watch?v=NhprB_OOrLQ

    I finally found that the Aaen engine was designed for speedway
    https://cybermotorcycle.com/archives...bikes/aaen.htm
    AAEN : http://www.aaenperformance.com/V4_racing_engine.asp

    I see that back then in 1967 he was using forced lubrication (very clever ) and disc valve induction (extremely clever).

    Now they use piston controlled intake, no disc valve and not even a reed valve... And no forced lubrication anymore.

    But they do have something special : a crankcase design like Jean Bertrand Bruneau was using in his JBB 250 http://www.pit-lane.biz/t117p560-gp1...-part-1-locked

  9. #33954
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    20th June 2020 - 07:10
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    Quote Originally Posted by katinas View Post
    Frits, what a lubrication system is used these days on the speedway engines (Jawa , GM). Stihl 4-mix use total loss oil scheme on 4t.
    https://www.youtube.com/watch?v=NhprB_OOrLQ

    I finally found that the Aaen engine was designed for speedway
    https://cybermotorcycle.com/archives...bikes/aaen.htm
    Olav Aaen is probably best known for his development in the very CVTs that was mentioned just a few posts back. He is still in the shop after all these years.
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  10. #33955
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    Quote Originally Posted by katinas View Post
    Frits, what a lubrication system is used these days on the speedway engines (Jawa , GM).
    Katinas, I do not know anything about speedway engines, other than that they contain cylinder heads full of valves. They are called four-strokes.
    For the ice speedway bike that I mentioned, I limited myself to the chassis. The Jawa frames, below left, with their flat front fork angle and without rear suspension, which were commonly used at the time, reminded me of Harley-Davidson choppers. But because of the incredibly high grip coefficient of the spiked tires, I thought we should go to the other extreme: a very stiff three-dimensional frame with a steep front fork angle, a twist-resistant upside-down front fork, the center of gravity shifted as far forward as possible, and a very progressive rear suspension. I'll be the first to admit that my contribution consisted mainly of talking; the only 'real' work I did was designing the suspension system.
    The rider was Tjitte Bootsma, a Dutchman who ranked just below the world top, but with this frame he suddenly placed himself in the world top ten. Subsequently, the top riders also wanted to buy such a chassis and Tjitte was willing to meet their request, so that the entire world top now rides on similar frames and Tjitte himself was pushed out of the top ten again .

    https://www.facebook.com/pg/Tibo-Motorparts-Tjitte-Bootsma-frames-471857229540070/posts/
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    To be honest, I did take a look at the engine as well. These 500cc four-stroke singles can offer a fair amount of engine braking when you close the throttle, which is just as well, because Ice speedway bikes have no brakes at all. But I thought I could do better. The braking on these engines is done during the compression stroke. But even without combustion, the piston is pushed down again by the cylinder pressure during the following expansion stroke, so the nett power absorbtion is not all that great.
    But if we lift the exhaust valve a little, say one millimeter, the compression pressure still provides braking, but around TDC this pressure leaks away and will not push the piston down anymore after TDC, almost doubling the total amount of engine braking.
    I used a Honda throttle grip with two bowden cables: the usual cable that opens the throttle, and a second cable that was there to pull the carburetor shut. But I did not attach that second cable to the carb, but to an exhaust valve lifter. So if you close the throttle, the carb is closed and you have normal engine braking. But if you force that throttle grip a bit further past 'normal closed', the exhaust valve is fractionally opened and engine braking is about doubled.
    If worked beautifully, but it was considered too dangerous to use it in a field of bikes with killer spikes, who could not brake like that.

  11. #33956
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    2nd March 2013 - 15:04
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    Quote Originally Posted by Frits Overmars View Post
    NFIG]346247[/ATTACH]

    To be honest, I did take a look at the engine as well. These 500cc four-stroke singles can offer a fair amount of engine braking when you close the throttle, which is just as well, because Ice speedway bikes have no brakes at all. But I thought I could do better. The braking on these engines is done during the compression stroke. But even without combustion, the piston is pushed down again by the cylinder pressure during the following expansion stroke, so the nett power absorbtion is not all that great.
    But if we lift the exhaust valve a little, say one millimeter, the compression pressure still provides braking, but around TDC this pressure leaks away and will not push the piston down anymore after TDC, almost doubling the total amount of engine braking.
    I used a Honda throttle grip with two bowden cables: the usual cable that opens the throttle, and a second cable that was there to pull the carburetor shut. But I did not attach that second cable to the carb, but to an exhaust valve lifter. So if you close the throttle, the carb is closed and you have normal engine braking. But if you force that throttle grip a bit further past 'normal closed', the exhaust valve is fractionally opened and engine braking is about doubled.
    If worked beautifully, but it was considered too dangerous to use it in a field of bikes with killer spikes, who could not brake like that.
    2-stroke trials bikes back in the old days usually employed a decompressor for massive engine braking. Same theory.

  12. #33957
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    20th June 2020 - 07:10
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    Back again for another question. I do the majority of my experimenting with limited port geometry, tight bore spacing twin cylinder engines. Many only have 4 transfer ports with elevator style ducts. Also used is a large single exhaust port.
    I was doing a little poking around on old posts within this thread, and stumbled across an interesting topic about how the first transfer to open flows last because of the flow reversal effect, due to higher cylinder to case pressure differential.

    This leads me to my question.
    What prevents us from opening the B ports a couple degrees before the A ports to promote flow through the As first in a situation like this? Would this allow for better loop scavenging and less short circuiting? Or do we just rely on the proper angles and axial flow to keep things in check?

  13. #33958
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    8th February 2007 - 20:42
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    Your situation is an odd one , thus will need an odd solution I am betting.
    4 transfer ports is super wierd , is this a reed engine , or more likely a piston port.
    I know that in the old screamer 100cc rotary valve kart engines they used a 3 port layout , with the boost port way higher - and this proved to be the best solution given the powerband required.
    In a 4 port scenario , just maybe it would operate somewhat like the usual 5 ports - depends alot on the relative size / area of the A and B ports.
    For a wider powerband ( and no PV ) normal stagger is used ie A port opens first.
    For max power ( and with a PV ) reverse stagger ie B & C are highest , as this gives you the max transfer STA for the same timings - in both scenarios the Blowdown STA wont change.
    This cant be modelled in 1 dimensional simulation , so grinding and dyno tests are the only option.
    Maybe a good CFD analysis would give you the right direction to go , but hey , I would happily sacrifice a cylinder to find out what doesnt work - done it plenty of times before.
    But I would bet the house on the fact that opening all 4 together , wont be the best solution.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  14. #33959
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    3rd May 2017 - 04:03
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    Inline crankshaft

    Any idea how make simple and robust connection of 2 existing crankshafts to inline layout with minimal rework of original parts?
    https://www.rrd-preparation.com/en/v...linder-2t.html

  15. #33960
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    7th October 2015 - 07:49
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    Quote Originally Posted by Frits Overmars View Post
    a very stiff three-dimensional frame with a steep front fork angle, a twist-resistant upside-down front fork, the center of gravity shifted as far forward as possible, and a very progressive rear suspension. I'll be the first to admit that my contribution consisted mainly of talking; the only 'real' work I did was designing the suspension system.

    Thank you Frits, very interesting story and sudden evolution.
    Steeper fork geometry really helps to go faster through the first part of the corner, but at full lean angle, with shorter front wheel twisting shoulder, its harder to hold tight line and the rear shock greatly helps to stay on the way, as front fork angle not changed too much through the corner.

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