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Thread: Rule change submissions close 1 March 2016 - be in to win.

  1. #301
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    [Q
    Maybe if you 125cc 2t guys aimed a bit lower HP wise your motors would be a bit less stressed, would make a bit less heat and might last long enough to do a bit of winning.

    you only need to check out Rick Fords TF125 to prove that sentence correct, it's won F4 Auckland Championship and the North Island Championship with not much more than 20BHP, oh and Avalon lapped an entire north island field on a 25bhp GP125. You do not need 30bhp to win a series you need a GOOD RIDER on a RELIABLE bike which HANDLES well, you sure as hell will not win series on a rocket ship that spends 1/2 the rounds in bits.

  2. #302
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    Quote Originally Posted by cotswold View Post
    [Q
    Maybe if you 125cc 2t guys aimed a bit lower HP wise your motors would be a bit less stressed, would make a bit less heat and might last long enough to do a bit of winning.

    you only need to check out Rick Fords TF125 to prove that sentence correct, it's won F4 Auckland Championship and the North Island Championship with not much more than 20BHP, oh and Avalon lapped an entire north island field on a 25bhp GP125. You do not need 30bhp to win a series you need a GOOD RIDER on a RELIABLE bike which HANDLES well, you sure as hell will not win series on a rocket ship that spends 1/2 the rounds in bits.
    More to the point the nikasil peeled off twice... third time was a squish error on a used and reused gasket. Point I was making is that I am happy with 24mm carb or its 452mm squared derivative, if TZ changes that to bring it in line with a rule that works, all good.

    My objection is that the rule change for the water coolers has got out of sync with the rest, and will create a class biased towards bought in motors. Mark my words, wait and see...

  3. #303
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    Quote Originally Posted by seymour14 View Post
    Well I propose that Water-cooled 2ts go back to 104cc, the tried and true capacity, and we all go on our merry way...

    Crisis and arms race averted, Doomsday Clock gets put back to 11am.
    This would suit me the best as I already have a 104cc crank for my 2T water cooler and would be my personally favored option.

    My next personally favored option would be to give the 125 2T's the same 10% over bore allowance that the 100's have been allowed because a group wanted to use over sized pistons without having to go to the trouble of de stroking to stay within the 100cc capacity limit. Then there are the 4T's, and that should be re visited too.

    Quote Originally Posted by jasonu View Post
    by your admission will change the way you go about building a 125cc 2T air cooled motor.
    Still have the thermal limit issue with a air cooled 125 2T whatever way you go carburetor wise.

    Quote Originally Posted by jasonu View Post
    What you are proposing is more than a 'tidy up'. Getting rid of the 24mm carb rule is a significant change.
    True, but there is starting to be a ground swell for change, mostly tidying the rules up, bringing them all into one place and revisiting the capacity limits to allow a broader range of choice.

    Before submission cut off is a good time to talk about it and by starting this thread I have tried to get the conversation out of the back rooms and going publicly so you me and everyone else can have our say.

  4. #304
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    Quote Originally Posted by seymour14 View Post
    More to the point the nikasil peeled off twice... third time was a squish error on a used and reused gasket. Point I was making is that I am happy with 24mm carb or its 452mm squared derivative, if TZ changes that to bring it in line with a rule that works, all good.

    My objection is that the rule change for the water coolers has got out of sync with the rest, and will create a class biased towards bought in motors. Mark my words, wait and see...
    I'm with you on the 110 thing, hell the winningest bike is an 80cc so go figure

  5. #305
    Quote Originally Posted by speedpro View Post
    I see this as a way of allowing the "restriction" to be located seperate from the carburetor. The adantages are obvious. For example a "restrictor" could be placed at the inlet of an airbox which in turn feeds a large carb mounted on the engine with obvious advantages of packaging and throttle control.
    1. Really easy to make the rule say "The restriction must be down stream of any throttling device". Once you say that it gets very hard to make power without a lot of work and big sacrifices to response. See attached photo for a 450cc single cylinder intake flowing through a 20mm restrictor that is placed down-stream of the throttle and still making 50ish HP. But seriosly hard to tune, annoying to package and as I would never put it anywhere near a bike.


    2. I don't think the rule should be gotten rid of all thogether. At the very least it is making the 125 Air-Cooleds harder to make and run, which is another way of creating a bit of parity.

    3. DO NOT MAKE AN AREA BASED MEASUREMENT. Oh please god don't do it. Why? Because there is no tool that we keep in our toolboxes that directly measures area. If you can't measure it directly, it is not enforcable, and the problem hasnt been fixed at all. All it would take is one guy to turn up say, a spiral shaped restrictor, and the rule is buggered.

    A downstream (of the throttle plate) restrictor with a maximum chordal measurment of 24mm is very, very easy to enforce. It will go something like this:

    Guy One: "Guy two is cheating, his restrictor is too big"

    Official: "Guy two, where is your restrictor?"

    Guy 2: "Right here, infact, my restrictor is part of the outlet of my 24mm carb. Let me take it off so you can measure it"

    Offiial: "Okay, let me get out my standard set of calipers...... Hey! I can measure more than 24mm with both of the internal jaws on my calipers inside the bore of your restrictor. You are cheating"

    Guy 2: "Oh damn. I thought I was legal. Good thing I am only racing C grade. I will go fix it now"

    Guy 1: "Official, Thanks for securing my chances of taking 8th place in C grade this year. I am glad the rules are so easy to enforce."
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  6. #306
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    All good points in your post ....

    Interesting racers, and at Mt Wellington too.

    Would love to see more photos of them and the engine setup.

    Quote Originally Posted by Moooools View Post
    1. Really easy to make the rule say "The restriction must be down stream of any throttling device". Once you say that it gets very hard to make power without a lot of work and big sacrifices to response. See attached photo for a 450cc single cylinder intake flowing through a 20mm restrictor that is placed down-stream of the throttle and still making 50ish HP."
    Out of interest, what are the chances of a larger diameter restrictor effectively throttling a smaller motor.

    20mm dia restrictor + 450cc = 50ish hp.

    24mm dia restrictor + 125cc = ????? hp. what do you recon, and would the compromised air cooling become a limiting factor before the throttle restriction does?

  7. #307
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    Quote Originally Posted by TZ350 View Post
    Out of interest, what are the chances of a larger diameter restrictor effectively throttling a smaller motor.

    20mm dia restrictor + 450cc = 50ish hp.

    24mm dia restrictor + 125cc = ????? hp. what do you recon, and would the compromised air cooling become a limiting factor before the throttle restriction does?
    Interesting discussion. And it would be very telling to have a knowledgeable reply to TZ's question. A bit of a decider really.
    Factual Facts are based on real Fact and Universal Truths. Alternative Facts by definition are not based on Truth.

  8. #308
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    Quote Originally Posted by cotswold View Post
    I'm with you on the 110 thing, hell the winningest bike is an 80cc so go figure
    Currently the winningest bike is Rick's 125. I'm still waiting for a doomsday 110cc 2T to be built, or even a "non-doomsday" 110cc 2T. A perfectly legal 80cc bike is doing well in Auckland. Perfectly legal because the owner saya so and there has not been a protest and subsequent ruling.

  9. #309
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    Quote Originally Posted by seymour14 View Post

    My objection is that the rule change for the water coolers has got out of sync with the rest, and will create a class biased towards bought in motors. Mark my words, wait and see...
    Quote Originally Posted by cotswold View Post
    I'm with you on the 110 thing, hell the winningest bike is an 80cc so go figure
    Don't forget a water cooled 2t from 104cc to 110cc IS SUBJECT TO THE SAME 24mm carb rule as the 125 2t aircooled motors.

  10. #310
    Quote Originally Posted by TZ350 View Post
    All good points in your post ....

    Interesting racers, and at Mt Wellington too.

    Would love to see more photos of them and the engine setup.



    Out of interest, what are the chances of a larger diameter restrictor effectively throttling a smaller motor.

    20mm dia restrictor + 450cc = 50ish hp.

    24mm dia restrictor + 125cc = ????? hp. what do you recon, and would the compromised air cooling become a limiting factor before the throttle restriction does?
    A 20mm restrictor can theoretically flow heaps more than 50hp. With a 30% thermal efficiency in the engine, some napkin math is saying more like 90hp is possible. (Anecdotally I know this to be a bit conservative). However, even though the engine only needs 60hp of air, the air does not flow continuously through the restrictor, and instead pulses once every second cycle as the inlet valves open. This restricts the maximum power output of the engine, and the intake plenum is there to smooth out these pulses. (You would know all of this Rob, but just here for completeness). Multi-cylinder engines reduce the pulsing a great deal, and some 4cylinder 600cc engines are producing 80HP+ through the 20mm restrictor.
    I have heard accounts of some 450cc single cylinder engines being restricted down to about 18hp by the 20mm restrictor when not using any plenum at all. (But still with a nice converging/diverging restrictor). These are usually teams that have run out of time to make a plenum however so maybe not entirely indicative of the absolute limits of performance with this arrangement.

    A 24mm restrictor has 44% more area and so by the same math will flow 130HP+ as continuous choked flow. The two strokes engines used in buckets are smaller capacity, higher revving, small displacement, and pull twice as often as a four stroke (being two stroke). I would therefore expect much less pulsing through the restrictor, and so a higher HP limit. At the very minimum with a nice restrictor I would say 40hp is possible. I wouldn't be surprised if it was more at all.

    Some napkin math I did the other day estimating the amount of air required to cool an air cooled engine making 40hp is over 1.5m3/s. Like...a lot. So yes I would say that that limit comes first currently.

    HOWEVER - Just because cooling limit comes before intake air limit, it does not mean that the rule has no effect the class. Careful consideration of restrictor design, carb selection, tuning and engineering outside of the normal scope of two stroke building is required to make it all 'click'. This requirement takes development time away from other aspects of the engine, which helps to keep development speed in line with other engine configurations. As such I think the rule is working, and should only be modified for clarity and ability to be applied to EFI.

  11. #311
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    Quote Originally Posted by Moooools View Post
    A 24mm restrictor has 44% more area and so by the same math will flow 130HP+ as continuous choked flow. The two strokes engines used in buckets are smaller capacity, higher revving, small displacement, and pull twice as often as a four stroke (being two stroke). I would therefore expect much less pulsing through the restrictor, and so a higher HP limit. At the very minimum with a nice restrictor I would say 40hp is possible. I wouldn't be surprised if it was more at all.

    Some napkin math I did the other day estimating the amount of air required to cool an air cooled engine making 40hp is over 1.5m3/s. Like...a lot. So yes I would say that that limit comes first currently.

    HOWEVER - Just because cooling limit comes before thermal efficiency limit, it does not mean that the rule does not affect the bike. Careful consideration of restrictor design, carb selection, tuning and engineering outside of the normal scope of two stroke building is required to make it all 'click'. This requirement takes development time away from other aspects of the engine, which helps to keep development speed in line with other engine configurations. As such I think the rule is working, and should only be modified for clarity and ability to be applied to EFI.
    Thanks for that, very interesting to see some numbers.

  12. #312
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    Quote Originally Posted by Moooools View Post
    A 24mm restrictor has 44% more area and so by the same math will flow 130HP+ as continuous choked flow.
    Ya for science, I guess nobody is seriously expecting 130+hp from a 125cc 2T but it sort of shows the folly of a 24mm carb restriction.
    Factual Facts are based on real Fact and Universal Truths. Alternative Facts by definition are not based on Truth.

  13. #313
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    Quote Originally Posted by TZ350 View Post
    So ""no restriction on make or design of carburettor"" no restriction on make, that is me, as I am the maker or design, my own design of high flow venturi insert carburettors. I make these from other manufactures carburettor bodies. So total, totally legal, they also make the 24 thing ineffective as a restriction. Also there is the dawning of the 2T EFI throttle body thing becoming a reality.

    With MNZ's hopelessly confused clarification. I wanted to see if we could formulate a better way of defining "equivalent to a single 24mm carb" without changing the original thrust of the rule, which was basically, all air through an equivalent 24mm hole.

    I am not fussed, keep the rule, change the rule or level the playing field carburetor wise by doing away with the rule.

    In hindsight and experience I think it has always been an ineffective rule. But the only way I will lose anything is if the 24mm rule is dropped. The rules may be simpler but I will have lost all of the perceived benefit I may have gained from my hard work.

    That is the real rub.
    Quote Originally Posted by TZ350 View Post
    There is no "need" unless you want to start tiding up the rules. 1st of March, two weeks time is the dead line for this year, that's the "need".
    Quote Originally Posted by seymour14 View Post
    Someone needs to fill me in with history. Have the air cooled 2ts been successful in the past? Or more to the point, too successful?

    If not, the suspicion is they may do well on big tracks, but as Regan says, you roll the dice on the smaller ones. Thermal conductivity plays a big part, but whether the rule changes or not, it will be fun to play around with more and see what can be achieved within whatever rules apply to it. Our dyno runs look promising with a 24mm carb, but reality says that the bike still needs to finish a race...

    As to water-cooled 2ts, they are already proven successful, it would be sad to make them the only bikes worth while having (buying). I would be proposing to the whole team to buy up 110cc engines if the rules stay as they are.

    My recollection of the intent of the rule (that allowed 125 2T's to be introduced) was two pronged restriction air cooling and 24mm throat.
    I needs to be remembered at the time and as it is still now hardly any 100cc 2 strokes were actually water cooled.
    Even Speedpros 30HP is partially air-cooled likely even achieved the 30hp without the water cooled head. (Mike can confirm)

    If the MNZ considered it farcical why did they include the 110cc with the same 24mm restriction.



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  14. #314
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    Quote Originally Posted by husaberg View Post
    If the MNZ considered it farcical why did they include the 110cc with the same 24mm restriction.
    Don't think they included it, its in a different part of the MOM's, nobody reminded them so they just forgot to take it out or adjust it for 110.
    Factual Facts are based on real Fact and Universal Truths. Alternative Facts by definition are not based on Truth.

  15. #315
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    Quote Originally Posted by FastFred View Post
    Don't think they included it, its in a different part of the MOM's so they just forgot to take it out or adjust it for 110.
    Are they really that useless? Even I find that hard to fathom. Has anyone got the original ruling and submission?

    IMO the fact that the restricted 125 2ts are producing around exactly the same hp as the unrestricted 100cc 2ts proves to me the current restriction rule work.



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