Keith@FP said:
Keep in mind that they are allowed some modifications. SM isn't a stock class, it's a spec class. Free exhausts, timing and intake do allow for some power to be found and for the powerband to be moved to a more appropriate level for racing. You wouldn't necessarily want to drive one of these motors on the street.
Plus the careful tuning of course. I've heard the 1990 motors are the ones that do best, thanks to a more aggressive cam.
Keith
Come on, Keith! A 1.6 Miata with an intake, an exhaust and advanced timing not being a car you'd want to drive on the street? Your car has a lot more work done than that!
Yeah, these motors get a lot of little things done and may not be the longest lasting motors, but they behave just like a stock Miata motor, except with about 20hp more. They are not very peaky or "race like".
When I said "stock" motor, I meant that the motor itself is supposed to be stock. Yeah, they can put an intake and an exhaust (with stock manifold), but every part of the long block itself has to be within the dimensions specified by Mazda for that part.
The trick in Showroom stock and in SM, and the reason why these 1.6 motors are making so much power is in what Mazda DOES NOT give dimensions or specs for in the manual. Like, for example, the factory manual does not give any specs for how things look like inside the flow meter. Only a procedure for verifying that it works. Same thing for the differential. They give specs for the ring and pinion, etc., but not for dimension of the internal parts inside the diff.
These motors also get build based on what the tech inspectors can measure and detect and what they can't, if you know what I mean. There is a lot of "parts bin blueprinting", but there's also quite a bit of plain old machining that can't be detected too. In the end, you end up with a 1.6 motor that is supposed to put less than 100hp to the wheels and you end up with more than 110 hp to the wheels (some with a LOT more than that) and still are "stock" motors in that their components meet the dimensions given by Mazda for each part.