Ok, so reading a bunch of posts about how putting an aftermarket front motor mount seems to improve shifting, I thought about getting one. After sitting in an Evo X that had one installed, I changed my mind. The vibration was unbearable. I can take a lumpy idle and low frequency vibration but this was the massage chair, high frequency type that you feel through the seat. After getting out of the car, my legs were still tingling.

So then I remember reading about how people made a DIY motor mount by filling the mount with polyurethane. A lot suggested the 3M Window Weld that you can pick up at a hardware or auto supply store. The 3M Window Weld has a durometer of 55-60A. Which is much less than the 90A that most aftermarket mounts are made of. Well worried that even this polyurethane was too hard, I thought of using silicone. The same you use in your bathroom.

So I pulled the front motor mount off and I was surprised at how flexible it was. It took very little effort to get it to move a millimeter or so. No wonder, shifting in the Evo was such a chore. I filled the mount with silicon and baked it in a toaster oven (180F) to speed up the cure. Full cure is about 24hrs. Even after a few hours in the oven, the stiffness of the motor mount was greatly improved. I had my doubts this would even do anything but I installed it in the car anyways.

Started the car up and no extra vibration at all - NONE! Then I warmed up the car and the shifting didn't seem much better. I proceded to bang out a full throttle 1st-3rd pull and wow, not a single misshift and no grinding. Prior to this I had plenty of 1st-2nd or 2nd-3rd misshift or grinds.

So after driving on this for about a week and a half, I've yet to have a misshift and I've only had one grind. The car shifts so much better now. My only worry is that the silicon won't last that long. I don't mind since it's easy to remove and I can try something a bit more durable like the 3M Window Weld later.

Stock mount



Filled both sides with silicon



Not pretty but who cares.

 

BTW, I forgot to add that I degreased and cleaned the part before injecting the silicone.

 

Window Weld FTW!

 

I used window weld on one of my Mr2 mounts, actually worked well, its like the perfect durometer for that.

 

Yeah, well after this experiment worked so well, I'm tempted to cut the silicone out and redo it with Window Weld. I'm just worried about the vibration. I've never experienced anything like this. I've had other cars with aftermarket motor mounts and they vibrated more at idle but it was somewhat bearable. I have a feeling that the stiffness of the chassis is the culprit.

 

I took my AMS 90A Race front motor out last night and WOW is the car more comfortable to drive. I have a set of Boomba front and rear mounts that I'd planned on installing with my front sway (both require dropping the subframe) but now I'm having second thoughts. And I think you're right about the stiff chassis, it's amazing the difference in noise and vibration between the stock and solid bushings.

 

I have read that some Porsche's use hydraulic motor mounts...I wonder what the benefits to that are and how much that would cost?

 

omg, you're not serious, you can't expect that to last??? There are differently rated mounts, AMS, powerflex etc etc, my powerflex isn't harsh at all, little bit of vubration, but it feels like the car's alive!!

 

Too bad nobody makes a softer one. Does the AMS mount vibrate bad?

 

I made a set of window weld mounts for my old 2004 ralliart. I checked them about 2 moths before I traded it in earlier this year. They were still in great shape. You solidify the compound before you install it. You're supposed to bake them in the oven at about 200deg over night before reinstalling (or something like that... cant remember the details).

The Ralliart's mounts were very different, though. Totally hollow. The Evo stock mounts just leave a bit of room.

You might be able to get a big washer that'll fit around the mount bolt to help keep it in place if you're worried about it coming lose after time. Either way, nice compromise

 

That sounds like a good idea with the washer. I'll pull the mount this weekend to see how it looks but this morning, it still shifted well. I don't expect the silicone to last very long. It's durometer rating is around 25-30A. If someone made a mount with a durometer of about 50A, I'd own one right now. But since no one does, I'm making one that gives me better shifting without much compromise.

 

the AMS mounts are a durometer of 70A for the street mounts, and 90A for race mounts.

 

wow this stuff actually works aye. hmm i would still want to go with a race version from ams. very informativethough

 

Version 2.

I pulled out the motor mount to check how the silicone was holding up and it was still in good shape. I would still get movement when I applied force to the center ring but it's easily about half of what it was before. I decided to pick up some 3M window weld and stiffen up the mount some more. I cut away half of the silicone and applied the window weld to the lower half of the mount. After 6hrs of curing in the oven at 200F, I pulled it out. I let it cure overnight and checked the stiffness. It's quite a bit stiffer than before. I'd rate the stiffness like this.

Stock - I'm able to move it about 4 mm by hand in one direction!
Stock w/ silicone - It's cut down to about 2 mm.
Stock w/ 1/2 silicone and 1/2 window weld - Down to about 3/4 mm.

I reinstalled the motor mount and started the car up. No additional vibration through the seat and a little bit more vibration through the steering wheel and the dash as well. This is about perfect for me. The problem with the full silicone version was that I could still feel some engine movement during hard shifting. So the goal was to stiffen up the mount as much as possible to where the vibration was bearable. I've yet to take it for a test drive because I want it to cure some more. The cure time is about 7 days. I placed a bead of window weld in the oven next to the mount for the same 6 hrs. I cut that open and it was solid but I know how that goes. Solid still doesn't necessarily equal a fully cured part.

BTW, be careful on the curing temperature if you attempt this. Most rubber materials I deal with at work will change properties (or melt) at around 300-350F.

Window Weld FTW!

 

powerflex one is softer.........