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Originally Posted by BAN SUVS
I've been trying to calculate based on this equation:
Displacement + [(multipiler 1 * displacement) - displacement] + [(multipiler 2 * displacement) - displacement] and so on. Basically, adding together each multiplier instead of multiplying what you already multiplied. Right?
So a Miata is 1.8 * 1.25 for dohc/4 valve = 2.25 L. Adding a turbo to that will be 2.25 + (1.75 * 1.8 - 1.  = 3.60. Or am I not following the rules? |
That sounds *way* too complicated. I believe the multipliers are to be applied all at once. The idea is that if you've got DOHC and a turbo, they're going to make each other more helpful. i.e. adding a turbo should result in 75% more power no matter what you started with.
Take your miata example:
1.8L (base)
* 1.25 (4 valve, DOHC)
= 2.25L -> TT-5
Now add a turbo:
1.8L (base)
* 1.25 (4 valve, DOHC)
* 1.75 (other turbo)
= 4.94L -> TT-3
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Originally Posted by BAN SUVS
Also, Scott you potentially could reduce your class under my interpretation by using 2.0 as your "base" displacement, since you technically still have a WRX motor (block architecture, heads) and add the 1.50 "motor swap" factor in for the EJ257.
I'm thinking very little analysis was done for applying these rules as they were written.  |
I think the "motor swap" multiplier is really designed to properly class cars that have complete swaps. Basically, if you take a little car like a Sprite or something and drop a small block chevy motor in it, you're going to have awesome power-to-weight. The "engine swap" multiplier factors in that most motor swaps result in far more power than the original car was intended to have.
In the case of my "swap", I really haven't swapped my motor. All I've done is effectively increased my base displacement. Hell, 90% of the parts on that motor *are* from the original, the only thing that's new is the short block. Which is why I'm planning on not applying the "engine swap" multiplier but bumping my base displacment and considering my car a TT-3 car, which is appropriate assuming all the tuned STi's are also TT-3. It's the same as if I pulled the 2.0L short block, and had it bored/stroked to 2.5L.