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Thread: ESE's works engine tuner

  1. #34486
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    Quote Originally Posted by wobbly View Post
    SwePatrick - that is a dangerous asumption as the Aprilia would break the RV drive shaft when certain numbskull riders would try to use the engine braking ( breaking ) like a 4T and
    change down gears , instantly hitting 14500 rpm. The inertial loads from spinning up even a carbon disc are considerable.

    My take on the drive setup would be a seperate small enclosed space with a seal on each end of the cross shaft.
    That way the you would have a minimal oil bath needed for the bevel and the LH bearing behind the balance disc only ( the balance disc does not need oil splash at all )

    Myself and Jeff Henise are looking at the same scenario for a 500 parallel twin with two RV across the front , needing individual discs as it runs 90* firing.
    Ofcourse you need to take in calculations using a bit beefier then normal.
    I thought everyone was smart enough to compensate for that

    If it is possible to get it to work on big v8 engines(brass gear on distributor), i would think its possible to get it to work on a small shaft with a carbondisc in the other end.
    You seen a distributor and its huge rotor?
    Quite big inertia in those(even thou its plastic), and i have never seen any gear suddenly break due to tireshaking(high intense shaking in whole driveline, huge clatter in gears), they get worn by mileage as everything is anyway.

    Seems to be the interwebs these days, to blow up a small problem to a huge one.

  2. #34487
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    18th April 2017 - 23:08
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    Quote Originally Posted by wobbly View Post

    My take on the drive setup would be a seperate small enclosed space with a seal on each end of the cross shaft.
    That way the you would have a minimal oil bath needed for the bevel and the LH bearing behind the balance disc only ( the balance disc does not need oil splash at all )

    Myself and Jeff Henise are looking at the same scenario for a 500 parallel twin with two RV across the front , needing individual discs as it runs 90* firing.
    Thanks wob
    I can only agree that it is the most straightforward approach.
    Hope to hear more about the 500 project! Sounds very interesting.

    Quote Originally Posted by ken seeber View Post
    Muhr,
    Without a full understanding of the design, I would think that the shaft bearings and gears could all be lubricated using the transmission oil. This would necessitate some careful design of angled channels and drillings to ensure the oil gets around. If you had the one (& only) seal behind the bearing adjacent to the disc valve, this bearing would have to be lubricated. Not sure on the overall angling of the unit, but possibly a drilling from the B port crankcase passage might be sufficient to create some flow. Maybe there is enough oil (from the mixture) migrating to the centre of the disc to get into the bearing.

    Some nice features in the design.
    Thanks Ken
    Yes it would have been neat to be able to get this part can maintenance itself from the already existing lubrication. Made a sketch of using balance shaft gear as a pump, maybe a little too optimistic ..

    Quote Originally Posted by SwePatrick View Post
    Ofcourse you need to take in calculations using a bit beefier then normal.
    I thought everyone was smart enough to compensate for that

    If it is possible to get it to work on big v8 engines(brass gear on distributor),

    Seems to be the interwebs these days, to blow up a small problem to a huge one.
    Questions one should ask yourself are how fast it spins and how fast it changes speed

    https://en.wikipedia.org/wiki/Jerk_(physics)
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    No amount of experimentation can ever prove me right; a single experiment can prove me wrong.

  3. #34488
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    Quote Originally Posted by Flettner View Post
    are you not better off just running two crankshaft disc valves, one either side.
    That is what Jan Thiel would prefer now, based on his experience with the rear-disc-valve RSA.

    Quote Originally Posted by wax View Post
    Reading back through the posts I came upon a part where you were talking about y-manifolds and how it can supercharge the other cylinder as the exhaust gases come out the port. This was only at 200 degrees of exhaust or above. Do you think this is much better than the 190 degree superposition on the same exhaust system
    Exhaust wave superposition occurs when an exhaust port opens, not when it closes, so superposition does not directly enhance the reflected pulse from an expansion chamber; it enhances the primary pulse that is entering the expansion chamber. And yes, this enhanced primary pulse will lead to a stronger reflected pulse. In a good engine this reflected pulse may have an amplitude of about 2,5 bar.

    Now let's look at Y-manifolds and how we can use the exhaust pulse that exits the exhaust port of one cylinder to directly supercharge the neighbour cylinder.
    I call this phenomenon cross-charging, and it requires that the primary pulse out of a cylinder that opens its exhaust port, arrives at the other cylinder before this closes its exhaust port. This obviously requires an exhaust timing of over 180, and because the pulse has to travel via the Y-manifold, we have to allow for some travel time as well. Finally, we want to give the pulse sufficient time to inflict its maximum amplitude on the second cylinder. All in all, the required exhaust timing for effective cross-charging will be in the region of 220.

    An exhaust port this high will reduce the working stroke of the piston to just 70. Is that bad? For this working stroke: yes. But just look at what we get in return.
    The opening pressure of an exhaust port with a normal 202 timing (normal for an Aprilia RSA, that is) will be just below 12 bar. But the opening pressure of an exhaust port with a 220 timing will be close to 20 bar! Now that is some supercharging, compared to the 2,5 bar of a reflected pipe pulse.

    The icing on the cake would be a rotary drum in the Y-manifold, momentarily closing the manifold exit when an exhaust port opens, so that the total pulse energy exiting that exhaust port has nowhere to go but to the other exhaust port.

    Detail questions: how short should the manifold be? Not too short, because it should be able to hold all the mixture that will subsequently be shoved into the neighbour cylinder.
    What about intercooling? There wil be hardly any place for an intercooler, and supercharging a cylinder with high-pressure hot mixture is begging for detonation, so maybe we should scavenge with pure air instead of mixture. And that would require direct injection. Diesel and HCCI come to mind...

  4. #34489
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    30th April 2011 - 04:57
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    quote.
    "An exhaust port this high will reduce the working stroke of the piston to just 70. Is that bad? For this working stroke: yes. But just look at what we get in return.
    The opening pressure of an exhaust port with a normal 202 timing (normal for an Aprilia RSA, that is) will be just below 12 bar. But the opening pressure of an exhaust port with a 220 timing will be close to 20 bar! Now that is some supercharging, compared to the 2,5 bar of a reflected pipe pulse."



    wow thats an interesting fact... 20 bar!.... heat causing detonation being the downside....when maybe used as a plugging source.

  5. #34490
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    Quote Originally Posted by Frits Overmars View Post
    That is what Jan Thiel would prefer now, based on his experience with the rear-disc-valve RSA.

    Exhaust wave superposition occurs when an exhaust port opens, not when it closes, so superposition does not directly enhance the reflected pulse from an expansion chamber; it enhances the primary pulse that is entering the expansion chamber. And yes, this enhanced primary pulse will lead to a stronger reflected pulse. In a good engine this reflected pulse may have an amplitude of about 2,5 bar.

    Now let's look at Y-manifolds and how we can use the exhaust pulse that exits the exhaust port of one cylinder to directly supercharge the neighbour cylinder.
    I call this phenomenon cross-charging, and it requires that the primary pulse out of a cylinder that opens its exhaust port, arrives at the other cylinder before this closes its exhaust port. This obviously requires an exhaust timing of over 180, and because the pulse has to travel via the Y-manifold, we have to allow for some travel time as well. Finally, we want to give the pulse sufficient time to inflict its maximum amplitude on the second cylinder. All in all, the required exhaust timing for effective cross-charging will be in the region of 220.

    An exhaust port this high will reduce the working stroke of the piston to just 70. Is that bad? For this working stroke: yes. But just look at what we get in return.
    The opening pressure of an exhaust port with a normal 202 timing (normal for an Aprilia RSA, that is) will be just below 12 bar. But the opening pressure of an exhaust port with a 220 timing will be close to 20 bar! Now that is some supercharging, compared to the 2,5 bar of a reflected pipe pulse.

    The icing on the cake would be a rotary drum in the Y-manifold, momentarily closing the manifold exit when an exhaust port opens, so that the total pulse energy exiting that exhaust port has nowhere to go but to the other exhaust port.

    Detail questions: how short should the manifold be? Not too short, because it should be able to hold all the mixture that will subsequently be shoved into the neighbour cylinder.
    What about intercooling? There wil be hardly any place for an intercooler, and supercharging a cylinder with high-pressure hot mixture is begging for detonation, so maybe we should scavenge with pure air instead of mixture. And that would require direct injection. Diesel and HCCI come to mind...
    Wow thats an awesome answer thank you.
    I have never even considered going that high with an exhaust port. I have a few cylinders I can try this with. I will do this and see what happens. Im guessing I will have a heap of blow down time

  6. #34491
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    8th February 2007 - 20:42
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    What would be considered " normal " in a twin cylinder with a single pipe ( as simply by using a single you are by defenition creating low bmep )
    the Ex timing will be down at 190 duration.
    Crank this up to 202 and the cross charging effect adds more power than it looses due to a reduction in power "stroke ".
    Rather than go even higher ( been there done that , moved on ) the next trick is to cut the piston skirts such that there is about 3mm of exposed port at TDC.
    This creates havoc with the jetting , but using pumper carbs , they can be tuned way wierd and fix that issue.
    In my experements with World Champ open jetski title engines , the "bottom open " port is capable of more power than the other option of going REAL high on the Ex duration.
    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.

  7. #34492
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    Quote Originally Posted by wobbly View Post
    What would be considered " normal " in a twin cylinder with a single pipe ( as simply by using a single you are by defenition creating low bmep )
    the Ex timing will be down at 190 duration.
    Crank this up to 202 and the cross charging effect adds more power than it looses due to a reduction in power "stroke ".
    Rather than go even higher ( been there done that , moved on ) the next trick is to cut the piston skirts such that there is about 3mm of exposed port at TDC.
    This creates havoc with the jetting , but using pumper carbs , they can be tuned way wierd and fix that issue.
    In my experements with World Champ open jetski title engines , the "bottom open " port is capable of more power than the other option of going REAL high on the Ex duration.
    Thanks Wobbly I also read where you wrote that. Im interested to try that and to see how it effects the ski. It seems all wrong but I am not about to second guess you on this one Wobbly. i would love to do a twin pipe engine on the ski I am building but it just seems to be so hard to get these stay together in these hulls.

  8. #34493
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    Quote Originally Posted by wobbly View Post
    What would be considered " normal " in a twin cylinder with a single pipe ( as simply by using a single you are by defenition creating low bmep )
    the Ex timing will be down at 190 duration.
    Crank this up to 202 and the cross charging effect adds more power than it looses due to a reduction in power "stroke ".
    Rather than go even higher ( been there done that , moved on ) the next trick is to cut the piston skirts such that there is about 3mm of exposed port at TDC.
    This creates havoc with the jetting , but using pumper carbs , they can be tuned way wierd and fix that issue.
    In my experements with World Champ open jetski title engines , the "bottom open " port is capable of more power than the other option of going REAL high on the Ex duration.
    Does the flow come from the crank case or go back into it . It would seem that the pressure in the exhaust is higher than the pressure in the crank case and thus flows into the crankcase, please help me with this one

  9. #34494
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    The pressure traces show that in a single cylinder at TDC the reeds are already starting to close , as the case pressure has already started to rise above atmospheric.
    Thus I make the asumption that the big negative pressure ratio around BDC of the other 180* out of phase cylinder , also arrives at the open bottom port , sucks like the old chrome off a towball joke
    and delays the case pressure rise .

    Therefore this big negative pressure ratio sucking on the partially open port holds the reeds open longer - giving rise to an increase in Delivery Ratio.
    Of all the inherent variables such as Scavenging and Trapping Efficiency , the simple act of filling the case with more A/F mixture with a " cheat " like this has a big effect on the Delivery Ratio - the hardest
    I believe to influence dramatically by what we consider normal tuning.
    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.

  10. #34495
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  11. #34496
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    Quote Originally Posted by wobbly View Post
    The pressure traces show that in a single cylinder at TDC the reeds are already starting to close , as the case pressure has already started to rise above atmospheric.
    Thus I make the asumption that the big negative pressure ratio around BDC of the other 180* out of phase cylinder , also arrives at the open bottom port , sucks like the old chrome off a towball joke
    and delays the case pressure rise .

    Therefore this big negative pressure ratio sucking on the partially open port holds the reeds open longer - giving rise to an increase in Delivery Ratio.
    Of all the inherent variables such as Scavenging and Trapping Efficiency , the simple act of filling the case with more A/F mixture with a " cheat " like this has a big effect on the Delivery Ratio - the hardest
    I believe to influence dramatically by what we consider normal tuning.
    Thanks
    yeah it kinda makes sense. im interested to know if you found it by accident or you actually decided to try it. Its a cool thing anyway. I cant imagine its good for economy but then I dont care lol . Greta hates me

  12. #34497
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    Quote Originally Posted by wobbly View Post
    Making the reed cavity exit area into the case , smaller and smaller has been a trend over the last several years.
    Do you happen to have a rule of thumb regarding this? For example xy% of the effective reed petal opening area or something like this?
    I am thinking about adding the possibility to fit stuffers of variable sizes to my next project or the one after that.

    Is it really beneficial to make the exit into the case this small (Vortex DJT)?
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  13. #34498
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    Would be an exhaust of the latest aprilia rsa.
    It seems improbable to me

    Click image for larger version. 

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  14. #34499
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    Quote Originally Posted by philou View Post
    Would be an exhaust of the latest aprilia rsa.
    It seems improbable to me
    Click image for larger version. 

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    You're right Philou. Below you'll find the Aprilia RSA pipe, codename Tubo102, once more.
    The pipe in your above drawing is probably an early Rotax pipe, maybe model VSK150 or thereabouts, from before 1990, or a derivative thereof.
    The partly visible logo on the right of your drawing belongs to Gazzaniga, an Italian producer of underwear who ran a 125cc GP racing team around 1990 with my friend Dolph van der Woude as designer/constructor. Dolph can probably tell us more about your drawing if he happens to drop in.
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  15. #34500
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    Some of the pipes done at Rotax in the early days of the 256 and 128 had some quite different designs, alot of which I had never seen before.
    Yes I think that is VSK 150 - I always wondered what VSK represented , or who actually did the new designs at Rotax back then.
    This pipe if I remember correctly we used as a basis at JL, when trying to get the same power out of fully blown manufacture , except the first thing I changed was to a single rear cone.
    We were sick of making the 180* U turn for the front pipe on the Tandem twin for Superkarts .
    Making that part front U part blown worked, but we could never get equal power by doing the rest .Hand made cones were always better.
    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.

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