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

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

    Quote Originally Posted by goose8 View Post
    It is an over size rule so the motor would have to start out as a 100cc or 150cc ?, just building a 110cc or a 158cc is against the rules is it not? After talking to a couple of people at the track yesterday ,they had similar feelings any thoughts on this.
    Quote Originally Posted by TZ350 View Post
    I agree building an engine to max oversize straight off is a grey area that probably needs addressing along with other issues like, what size is a 24mm carb equivalent really? and there are some who would like totally open fuel rules like they had in the original Bucket racing days.
    Naturally my interest is the 24mm carb equivalent rule and how it should be measured and should it be updated to specifically include EFI or done away with all together.

    Rule change submissions close 1st March.

    Input on the 24mm rule or any Bucket racing rule for that matter that interests others would be welcome.

  2. #2
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    Quote Originally Posted by Yow Ling View Post
    The measurement should be square mm, which is what the "equivalent" alludes to equivalent of 24mm carburettor is 452mm2, I like the idea of it being measured within the carb body. Actually a definition of a carb is also important, in this age of efi
    To me a "total inlet orifice area of 452mm2" looks a better definition than "24mm carb equivalent".

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    Quote Originally Posted by TZ350 View Post
    To me a "total inlet orifice area of 452mm2" looks a better definition than "24mm carb equivalent".
    With a rider that "for the purposes of measurement, carburettor air bleed jets and orifices are to be ignored"

    Just trying to avoid arguments when someone's carb measures up exactly and a bright cunt says "what about the air bleeds?"

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    Quote Originally Posted by Grumph View Post
    a bright cunt ?"
    Not sure that will be a problem...

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    Quote Originally Posted by TZ350 View Post
    To me a "total inlet orifice area of 452mm2" looks a better definition than "24mm carb equivalent".
    measured at the position of the original carburettor
    My neighbours diary says I have boundary issues

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    Quote Originally Posted by Yow Ling View Post
    measured at the position of the original carburettor
    Oh god NO...

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    Quote Originally Posted by Grumph View Post
    Oh god NO...
    Actually just get rid of the rule, if you just go with the 450mm2 restrictor thing you may as well not have a rule if there is a plenum between the restrictor and the 36mm butterfly, then that will allow open carbs on 110cc watercooled , 2 problems solved in one go
    My neighbours diary says I have boundary issues

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    My suggestion

    Two stroke air-cooled engines may be used to a maximum size including rebores of 130.5cc.
    Providing that, at some point in the inlet tract(s) between atmosphere and crankcase or barrel, the inlet tract(s) shall not exceed an area of 452mm2.
    For the purposes of measurement, carburettor air bleed jets and orifices shall be ignored.
    The point for measurement shall maintain the restricted diameter for a minimum length in the tract(s) of at least 2.0mm.

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    Regarding the 24mm carb sizing. I would think that it has been ok with the current rules as is, I would of thought if there was a problem; or is a problem, someone would of put a protest in. (I know it's not in the Sprint of buckets to protest, but I know first hand it happens for much less) maybe it's a good chance to clarify, more of interest is the efi sizing... but an efi 2 stoke bucket, that's crazy talk.

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    I like Grumph's wording but I also think there is no need for a change.

    We all know what's required or allowed. There has been no huge leap in technology which has resulted in the rule, or the intent, becoming a mockery. The only fly in the ointment is FI but if you got real picky the rule actually restricts F4 2Ts over 104cc to carburetion - no FI allowed.

    The rule says - "F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburetor" - cut & pasted from the MOMS.

    Of course the clever dicks will go on about how it doesn't say anywhere that FI is NOT allowed and they would be right. However the rule is very clear in that having a carburetor is a restriction. The FI aspect hasn't become a reality on the track yet. Certainly not to the point of being regularly competitive.

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    Carburation is the act of mixing fuel and air so that rule as it stands does include injection.
    If you want it to refer to carburettors only then at least a comma after carburation is required and preferably more for clarification.

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    Quote Originally Posted by TALLIS View Post
    Regarding the 24mm carb sizing. I would think that it has been ok with the current rules as is, I would of thought if there was a problem; or is a problem, someone would of put a protest in. (I know it's not in the Sprint of buckets to protest, but I know first hand it happens for much less) maybe it's a good chance to clarify, more of interest is the efi sizing... but an efi 2 stoke bucket, that's crazy talk.
    I agree in principle, but MNZ were 'kind' enough to go on record with a definition which does not accord with how the rule has been interpreted for decades...

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    Quote Originally Posted by TALLIS View Post
    ... but an efi 2 stoke bucket, that's crazy talk.
    Certainly nearly driven me crazy learning what to do ......

    But tackling new chalanges is the Bucket way.

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    EFI 2T, three injectors, Throttle body with TPS and dyno chart with runs at different throttle openings.

    I have found the trick is to use split injection for high and low power and the smallest low power injector possible because that gives the widest range of tunability for closed or trailing throttle under 30% TP (throttle position).

    The low power runs on the graph show that I have not got the nearly closed throttle fuelling anywhere good enough to be useful on the track yet.

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    100% TP = 27hp
    50% TP = 24hp
    40% TP = 20hp
    30% TP = 12hp
    (TP = throttle position)

    From 60% to a 100% TP typically (for any engine) there is not a great change in power, 25 - 27hp, a 2 hp change and consequent fuel demand in this case. The tricky fueling problems are all in the area between 0 to 40% TP, which is a 20hp change or ten times the variation in fuel demand as 60 to 100% TP on my EFI engine.

    So you need a primary injector that can be turned right down to next to nothing and ramped right up to 50% of the total fuel demand. The secondary big injector, actually the two side injectors fired together as a pair in my case need to be larger but their on time does not vary nearly as much as the single smaller injector needs too.

    Hopefully get the new bike finished soon so I can get back onto developing the EFI thing.

    So there we have it, a 2T EFI Bucket wannabe.

  14. #14
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    Quote Originally Posted by Yow Ling View Post
    Actually just get rid of the rule,
    Personally I agree.

    Quote Originally Posted by speedpro View Post
    I like Grumph's wording but I also think there is no need for a change.
    I agree about Grumph's wording and maybe no change is required if the rule sort of covers EFI.

    Quote Originally Posted by Grumph View Post
    Carburation is the act of mixing fuel and air so that rule as it stands does include injection.

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    Quote Originally Posted by Yow Ling View Post
    Actually just get rid of the rule, if you just go with the 450mm2 restrictor thing you may as well not have a rule if there is a plenum between the restrictor and the 36mm butterfly, then that will allow open carbs on 110cc watercooled , 2 problems solved in one go
    I thought there was no carb restriction on 110cc water cooled 2T.

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