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-   -   No more broken throttle shafts (https://www.miataturbo.net/engine-performance-56/no-more-broken-throttle-shafts-66090/)

Gee Emm 09-22-2017 07:25 AM

So, the racecar has just broken another TB, well it might have been broken for some time, who knows, I only noticed it when looking at something else. This time (again) broken at the cable-side screw and the screw has gone ... who knows where. Either through the lot, or it has lodged in some corner of the IM.

What is the likelihood of that happening, is it worth taking the IM apart to see? I am thinking the answer is 'yes', given the possible consequences downstream of the IM.

Pending something from 949 down the track, it looks like a Skunk2 TB is in my future. Beyond loctiting screws, are there any other pre-installation jobs that should be done to the current versions? Any real-world advantage to the billet version over the cheapie?

All thoughts and advice appreciated.

ElyasWolff 09-22-2017 12:52 PM

https://www.miataturbo.net/engine-pe...ock-off-94579/
If this one is truly the same it would be a no brainier.

MartinezA92 09-24-2017 01:17 AM

I vaguely remember reading that JB weld on the shaft was a possible solution. Take that with multiple very large grains of salt.
EDIT: lol the reason i vaguely remember that is because i talked about it with hustler 5 years ago in this very thread. oops.

engineered2win 09-24-2017 10:15 AM


Originally Posted by Gee Emm (Post 1441146)
So, the racecar has just broken another TB, well it might have been broken for some time, who knows, I only noticed it when looking at something else. This time (again) broken at the cable-side screw and the screw has gone ... who knows where. Either through the lot, or it has lodged in some corner of the IM.

What is the likelihood of that happening, is it worth taking the IM apart to see? I am thinking the answer is 'yes', given the possible consequences downstream of the IM.

Pending something from 949 down the track, it looks like a Skunk2 TB is in my future. Beyond loctiting screws, are there any other pre-installation jobs that should be done to the current versions? Any real-world advantage to the billet version over the cheapie?

All thoughts and advice appreciated.

You also need to drill another hole for the throttle return spring so that it fully closes the throttle blade. Otherwise there's almost no preload between about 5* and 0*, so you can have hunting idle and other problems due to the throttle blade not fully closing and staying closed.

Gee Emm 09-25-2017 05:47 AM

Thanks. I saw that advice, and wondered if it still applied.

I am watching the thread on the cheapies, but there is nothing there that makes me want to jump on one of those.

LukeG 09-26-2017 05:18 PM


Originally Posted by engineered2win (Post 1441555)
You also need to drill another hole for the throttle return spring so that it fully closes the throttle blade. Otherwise there's almost no preload between about 5* and 0*, so you can have hunting idle and other problems due to the throttle blade not fully closing and staying closed.

Confirmed. I had to drill a new hole on the brand new throttle body that I purchased recently.

Gee Emm 10-12-2017 06:08 PM

All good, need another bottle of locktite after that!

As well as the locktiting and relocating the return spring, I had to shorten the screw that lives in the countersunk recess in the adapter place for the IAC, by a mm or two. I needed a washer, but all the ones I had were too wide for the recess, so it was just simpler to grind down the screw.

I also pulled the plugs before starting it, to see what might have happened inside the chamber. Fortunately no sign of anything untoward, so it seems the screw must have passed through without leaving any calling cards. Phew! Bullet dodged!

Then, on the tow home from the dyno, some fricken tradie didn't tie down his ladders, and the top one got blown off the van, fortunately bouncing in the lane beside me! Another bullet dodged!


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