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Last Post 07 Oct 2014 07:04 AM by  JimmyNX
X-Prepared Engine/Weight Ruling
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JimmyNX
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02 Aug 2014 12:16 PM

    Hello everyone, 

    I am toying around with the idea of switching from EP to XP with my Datsun 510. During this process the obvious engine choice is the Nissan SR platform. Of course the most common is the SR20. 

    By my understanding of the 2014 solo rulebook, the minimum weight calculation is as follows:

    1. Four-stroke cycle and two-stroke cycle, naturally aspirated, internal combustion engines will be classified on the basis of actual piston displacement.

    All weights are calculated based on displacement as listed per Appendix A, 9.a. 
    Example: Weight for a RWD car w/ 1796 cc Turbo engine behind the driver is: 

    1200 + [(1.796 x 1.4) x (200 + 20)] = 1753 lbs.


    Now,  My question is the following. 

    Per my interpretation of this SCCA rule, the Nissan SR20 has a stock displacement of 1998cc’s. 

    Taking the literal interpretation of the rule, 1998 cc’s is NOT 2,000 cc’s or greater. 

    Therefore, the minimum weight calculation for a RWD powered SR20 vehicle in XP would be as such: 

    1200 + [(1.998 x 1.4) x (200)] = 1759.44 lbs.

    To clarify, the car has no abs, T/C, is front engined, and no active/reactive suspension.

    My reason for bringing this up is that with the previous statement an SR20 long block is eligible for the following weight formula, since it is calculated for Actual piston displacement. 

    Can anyone confirm my interpretation of the rules? And if someone says nay, whats stopping me from building a small 1.9L SR frankenmotor? How close to 2000 cc’s can one get without tipping over the scales by this ruling? 

     

    Thanks


    racingfool
    Basic Member
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    Posts:177


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    02 Aug 2014 06:20 PM
    2000cc is not a magic number in XP.

    You can run any size engine you want.
    JimmyNX
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    Posts:15


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    02 Aug 2014 07:29 PM
    Thanks.

    I realize this. What I am after is not getting tagged with an extra 200 lbs of minimum weight via the rules.

    I'm asking if by the rules a 1998cc engine will be categorized in the 1L weight penalty rather than the 2L weight penalty of an extra 200 lbs
    racingfool
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    Posts:177


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    02 Aug 2014 08:03 PM
    That's not how it works.

    1200 + [(2.000 x 1.4) x (200)] = 1760 lbs.

    Doesn't just jump 200 lbs for each liter.



    fzust
    Basic Member
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    Posts:169


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    02 Aug 2014 10:56 PM
    Racingfool is correct. Additionally, since you are 1759.44 you can round down to 1759!
    JimmyNX
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    Posts:15


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    03 Aug 2014 08:23 PM

    Sorry guys, I see where you are coming from but I do not agree with what you are saying. Please see page 217 of the 2014 Solo rules PDF or the following excerpt below:

     

    9. Minimum Weights

    a. Engine Classifications
    1. Four-stroke cycle and two-stroke cycle, naturally aspirated, internal
    combustion engines will be classified on the basis of actual
    piston displacement.

    2. Turbocharged or supercharged versions of all engines will be classified
    on a basis of 1.4 times the actual displacement.

    3. Rotary Engines (Wankel): These units will be classified on the
    basis of a piston displacement equivalent to twice the volume determined
    by the difference between the maximum and minimum
    capacity of the working chamber, times the number of rotors.
    b. Minimum Weight Calculations

     

    All listed weights are without driver. All weights are calculated based
    on displacement as listed per Appendix A, 9.a. 

    Example: Weight for a
    RWD car w/ 1796 cc Turbo engine behind the driver is 1200 + [(1.796
    x 1.4) x (200 + 20)] = 1753 lbs.

    Engine displacement less than 4.0L
    FWD.............................................. 1200 lbs. + 150 lbs. per liter
    RWD.............................................. 1200 lbs. + 200 lbs. per liter
    AWD.............................................. 1200 lbs. + 250 lbs. per liter

     

    As you can see and going back to my question, there is indeed a 200lb addition for EVERY liter of displacement for an engine under 4L regardless of natural aspiration or forced induction. The only difference is the 1/1 ratio for N/A and 1/1.4 ratio for forced induction.

    This goes back to my question - What is considered 2,000cc's? I will argue that the 1998cc's of the stock Nissan SR20 displacement is not a full 2L of displacement. Flame suit on. 

    P.S - The ( 200 + 20 ) tacked in the rulebooks supplied example is based on an engine under 2L of displacement with the engine located behind the driver, an additional 20lb "tax". 

    racingfool
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    Posts:177


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    04 Aug 2014 02:29 AM
    One liter motor gets 200 added. Two liters gets 400.
    1.5 liters gets 300. 1.998 liters gets 399.6.

    Your engine displacement is multiplied times 200.

    The 200 in your calculation here is the 200 we're talking about. That's all your car would need to weigh.

    Don't believe me? Fine. But fzust above has an insane XP car and has won many times in it and knows his stuff.


    1200 + [(1.998 x 1.4) x (200)] = 1759.44 lbs.
    FritzSpeed
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    Posts:44


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    04 Aug 2014 09:54 AM
    Just to further clarify, consider an actual displacement of 2001cc:

    (1200 + ((2.001 x 1.4) x 200)) = 1760.28
    or
    .200 lbs per cc up to 4.0L
    fzust
    Basic Member
    Basic Member
    Posts:169


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    04 Aug 2014 08:31 PM

    Fritz, The car in the example in the rules is mine. The reason for the break at 4.0L is to provide a weight break to the bigger motor cars. Your car would calculate as you put in the previous post at 1760.28 or 1760lbs. If you add ABS +50 for 1810. etc. I hope that helps.

    JimmyNX
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    Posts:15


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    07 Oct 2014 07:04 AM
    Thanks guys. I apologize for my misunderstandings of the rules on that. Who know - I may be seriously thinking about XP just to have a fun car rather than a non-competitive car after the EP/GP/DP Shuffle the board just pulled. Who wants to run against Miata's?
    You are not authorized to post a reply.


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