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)

First blog post..

I'm going to try to post some sorta record of all the little projects I'm doing, reports from the track, progress on the track car and hopefully not to many boring personal details.

At the moment, I just got back from Church's dyno, it's 9:00pm and I haven't had lunch yet. A typical day. The very light experimental clutch combination I tried didn't hold. Slipping at 70kpa so we never got the MegaSquirt PnP map completed. It's on the 91 Miata trackday project car. Just swapped in a 1.8 motor that is a stock 02 bottom end with a mild ported, polished, .015 shaved BP4W head. Even at like 40% throttle it was making 115lbs/ft so that's encouraging.

Anyway, the plan is to pack up and roll out Thursday evening for Sppedventures at Buttonwillow Fri-Sun. Can't do that with a slipping clutch so I called clutchnet while at the dyno in Wilmington at about 4pm. They made me a clutch on the spot and I dragged the trailer all the way to South El Monte to get it. I would like to say now that I am damned glad I don't have to drive in that poo every day. What's the Mercedes ad? "Around here, you have to love what you drive". Yah, otherwise you would become depressed I guess. I saw many of them wearing bleak expressions behind the wheel today. None of them driving Mercedes though so maybe there is something to that. I was towing a racecar so I was toting my anti-depression medicine within arms reach. After running the gauntlet safely, arriving in the splendid somewhat smoggy squalor that is So El Monte, I grabbed the clutch. Clutched the disc? Mission accomplished, sun going down, nearly finished race car on the trailer sitting with an expression that said " I know you really don;t want to go back to shop and install that disc tonight but I tell you what, start me up right now and I'll make a couple of really glorius trips into the sweet spot on my engine's VE for you. Right now, you don't even have to take it off the trailer". I obliged, and so did the little red car.

GPS located the nearest Starbucks for some octane booster. Sign read "Sorry but we are closing this location September 28th". Wow, I almost care. Uncharateristically, the coffee was fresh and blooming with nuance and flavor. I had the strangest that its was like last hurrah for that little store. OK, so I think too much.

So I'm going to fuel up at El Pollo and attempt to get the disc in tonight. Sleep is over rated.