Slyp_Dawg
Slyp_Dawg HalfDork
5/28/15 3:04 a.m.

The stock engine mounts on my Miata are pretty well shot (115k miles, the last 10k under my right foot, I'd say they've been tortured enough), and while i like the idea behind the SuperMiata motor mounts that 949racing sells, I'm a little turned off by the definite increase in NVH that even the softest bushing durometer option would bring. I'm definitely not above taking an idea and running with it (for personal use only of course, Emilio makes great stuff and I love the 949racing wheels so I don't want to step on his toes too much), except using rubber leaf spring bushings instead of poly bushings, to get a bit more vibration isolation without giving up the major advantages of the SuperMiata units. Other than making installation a bit of a pain, is there any reason not to rotate the bushings 90deg on the x axis (perpendicular to the driveshaft) and ~45deg on the z axis (parallel to the driveshaft, basically making them parallel to the subframe)? It seems like that would all but eliminate side-side movement of the engine even with squishy OEM-replacement leaf spring bushings, while still providing some vibration isolation. Thoughs? I do realize that it will make installation a bit of a pain, but i can live with that, since I doubt that pulling the engine will be a common occurrence. I can live with some increased NVH, but not to the extent of feeling like I have delrin motor mounts installed. In lieu of leaf spring bushings, would there be any other commonly available bushings that would likely perform well in this environment?

EDIT: for anyone who isn't familiar with the engine mounts that sparked this idea, here's where I got it from: SuperMiata Competition Motor Mounts

GameboyRMH
GameboyRMH MegaDork
5/28/15 9:37 a.m.

I think you're making too much work for yourself, did you consider urethane-filling some stock mounts? That gives you all kinds of hardness options too. I used 3M window-weld super-fast urethane when I did mine and it worked well, they're good and stiff and they're still very civilized for the street.

Filled mounts will also last much longer than stock, while putting more stress on your stock mounts by forcing them to bind (that's what you're proposing) will make them wear out faster.

Poly bushing mounts typically make the car feel like a paint shaker at low revs.

GameboyRMH
GameboyRMH MegaDork
5/28/15 9:40 a.m.

Behold:

http://www.miataturbo.net/suspension-brakes-drivetrain-49/diy-urethane-motor-mounts-39335/

Swank Force One
Swank Force One MegaDork
5/28/15 9:52 a.m.

Problem is that nothing, and i mean NOTHING that is built like a stock mount, will hold up. Not even poly.

The stock mount design is flawed.

Slyp_Dawg
Slyp_Dawg HalfDork
5/28/15 12:26 p.m.

The stock mounts are basically a rubber square with a stud on each side, so as the engine rocks back and forth, the stock mounts get sheared and torn apart. The Mazdaspeed mounts are simply a stiffer version of the stock mounts, but they don't improve upon the standard design at all

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