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Roundel Magazine's Checca story.

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  • #16
    Assuming the numbers were correct, e.g. 260 lb-ft @ 5400
    = 354 Nm torque, a constant and flat torque out to
    7500 rpm would give ca. 360 hp. allowing for a
    15% drop in torque (sloping down 15%), we would
    see around 315 hp at 7200 rpm and 330ish at 7500 rpm.

    Assuming the 260 lb-ft is correct, the power numbers
    are merely a result of maintaining nearly flat torque.
    This is not seen on stock S14 or 284/276 cammed
    2.5l S14, but it IS POSSIBLE. Motorsport cammed engines,
    timed correctly, also display almost flat torque albeit
    sloping down somewhat.

    I dont believe you can get 260 lb-ft with motorsport cams
    on 98 ROZ (93 AKI) gas with a 2.5l build up. Remember
    that is what the motorsport engines had to be able to
    race on.

    To achieve that torque, I believe one must go to
    very high cylinder combustion pressures. Partly
    thru very high compression ratio, necessitating
    110 octane race gas, ignition timing nailed for
    that C.R. and taking advantage of the fact it is a
    NEW MOTOR, AND (more easily) increase in displacement.
    Cams shouldnt have to be extreme duration, more likely
    maxing out lift despite longevity. If it had the steepness
    of a motorsport cam with even higher lift, that could do the
    trick. Your normal run of the mill schricks dont have that.
    FWIW, the dolate car used motorsport 324/304 cams
    but in a 2.8l displacement engine to make 400+ hp.
    It uses a special crank and modifications to the engine block.
    If increased in displacement is not used, I see only the
    first 2 points as the primary vehicle to realize the
    high cylincer pressures required to produce so much torque
    at low rpm. I didnt go thru the numbers, but we can
    guestimate the mean effective cylinder pressure developed
    to make that kind of power at the respective rpm -- and then
    compare it to other motors of similar caliber -- such motors
    would be e.g. hill climb engines, F3 engines, motorsport
    engines and so on. All with fairly radical intakes I might add.

    The motorsport engines used lower octane gas
    but also revved higher to also produce either 340 or 365
    hp (and higher). Revs are not really a problem, but a 9000+
    rpm engine will work better with a different gearbox. Stock
    US gearbox or CR gearbox are really inadequate for that.
    Therefore, there is a valid reasoning in trying to maintain
    a wide bandwidth to take advantage of the gearbox you have,
    assuming you cant change it.

    As far as my car compared to Rons, I dont believe there
    is a comparison. My car is atleast 150+ kg heavier than
    his. If his engine develops torque even remotely close
    to the way my engine develops torque, there is no contest.
    My car is still just a "street" car, not a race car. Rons car
    is a race car. So we should not mix apples and oranges
    My car still develops enough torque, that you certainly dont
    notice excess weight as bad as you would in a stock S14,
    nor does it particularly care about lots of drag due to rear
    spoiler flap. But, if you are measureing in tenths of a second,
    it definately can be measured in just pure acceleration run.
    Not to mention the substantial handling and grip advantage
    of reduced weight (including braking!)

    If Ron has achieved all this, he has done a very
    fine job!

    There are a few other interesting cars in CCA racing,
    so perhaps in a few months time the results will give
    a picture we can interpret .



    • #17
      Excellent stuff - thanks for the further explanations and ideas John.
      Scottish Cecotto