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Saturday, October 4, 2008

broken throttle shaft

After catching up on business most of the week I finally got around to investigating the throttle shaft failure. Turns out the missing screw heads had been AWOL for a while. I see now that they were what killed the original 1.6 back in January. So I had a spare TB shaft brazed to the plate and screws. The welder put a bit too much heat into the shaft (all one side) and warped it. As a result it was binding. The return spring would bring it back closed but that kind of thing could potentially turn into a stuck throttle. Applied some careful thumps to the shaft in two planes to bring it back straight so it snapped shut like the other healthy 1.8 TB's I have in the shop.

After looking at it more, a billet 4340 shaft with a lower profile and graded set screws would be a nice modification. Much better fatigue life, better airflow and no errant screw heads to attack the pistons.

Having rushed through prep last week, I have a
bunch of stuff I need to do before the next event at SOW
(Streets of Willow).

Putting an ETX9 motorcycle battery in. 7.4lbs! I'm going to try to fit it onto the subframe next to the starter. Get rid of the heavy cable running into the trunk, lower the CG & PMI, move mass from outside of the wheelbase to within it.

TheAutokonexion hood, like all Miata hoods was distorting at high speed and creating a gap to the fenders. On the drag strip of 18 Saturday I saw over a 1" gap at about 120mph! Wilson Steele, a composite engineer and Speedventures regular, suggested I bond the outer skin to the support structure underneath. As it is, it's only attached at the perimeter of the hood so the outer skin very flexible.

Engine stuff to do list before dyno next week:
1. Fab sealed airbox under RF headlight cover
2. Fit Setrab #119 oil cooler, Mocal thermostatic sandwich plate & -10 lines under RF corner
3. Install Savington's Coil on Plug set up, re-gap to about .050
4. Switch from 10-30 redline break in oil to 0-20W Amsoil
5. Siphon out the remainining 4 gal. of 100 octane Sunoco in the tank (dyno on 91 pump gas)

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