,
That hyper rev-happy launch in the video was the result of a super-touchy throttle, not (only) inept driving. A twist of the wrist on a Suzuki handlebar, it turns out, moves quite a bit less throttle than a stab of the foot on a Mazda gas pedal. The problem and the solution lie in the throttle cam, above. The closer the cable is to the throttle shaft's axis of rotation, the less cable it will take to move the throttle, and the touchier the throttle will be. To get the throttle action more in synch with the Miata's gas pedal, we need to move the cable farther out.
The big, gold bracket on the right holds the Hayabusa throttle cable, and the smaller cam thingy (with the phillips screw head as a pivot) is an idle kick-up cam for cold starts. We're not using any of that any more, since the Miata throttle cable comes form the other side. That means we might be able to use the little idle kick-up roller on top of the throttle cam to get the cable where we need it.
To make that happen, though, I had to remove the roller. Since this was too delicate a part to attack with a drill, I simply filed the head of the rivet holding the roller in place until it was flush with the surface (You can see from the different angle of the file marks that the rivet is already free to rotate here.)
With it filed down, I could carefully pry it out, while preventing the throttle cam from bending.
Next, I ran a 5mm x 1.0 tap through the existing hole,
And threaded in a 5mm screw, along with some assorted spacers and a flange-head jam nut. The spacers and nut create a nice valley to encourage the throttle cable to drop into the groove.
Just eyeballing it, the throttle cable pulls about 50% farther from the shaft with this mod.
So, the engine is back in the car now, the throttle response is more reasonable, the engine starts itself (yes, that video was real), and the engine isn't hitting anything obvious just yet. It's seriously time to hit the dyno!
Oh, but wait… We've changed all kinds of intake and exhaust tuning on this thing, and with a speed-density fuel system, that means we better do some tuning. And since we've changed the primary pairing on the header, we need to do cylinder-by-cylinder tuning. Oh noes! What will we do?
Easy. First we're gonna install an AEM 4-channel wideband controller, kinda like this:
Then we're gonna have Neel Vasaveda from Apex Speed Technology throw his crazy tuning skillz all over our shit, 'cause for him, this Hayabusa-powered car thing is nothing new. He said he's gonna use some piggyback thing called a Bazzaz. Seriously, we thought he sneezed. Piggybacks work really well on bike engines, it turns out, since there is no closed-loop mode and no self-learning to undo your piggyback tune. The Bazzaz has all the individual cylinder trimming power we need at a very reasonable price, so we're sold.
More on this in like a week, I swear.
All the Miatabusa you can handle:
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