Motor mounts

CigarJohnny · #1 02-17-2005, 02:26 PM

I'd like to stiffen up the motor mounts on my SVX. I just checked subaruparts.com and they run $158 +shipping...EACH! I checked for the other models and they offer the STI engine mounts (stiffer and IMO more desirable) for only $57 each. I had heard rumor that they can be modified for SVX use. Has anyone here done this? Does anyone have a diagram showing the engine mounts and mounting points? subieparts does not have a diagram for engine mounts. Pictures of the SVX mount that I can compare to the STI mounts would definitely be a plus. TIA!

Johnny

mbtoloczko · #2 02-17-2005, 02:38 PM

I've got the STi Group N motor mounts. An adaptor plate needs to be fabricated from 1/4" steel. I't may not be possible to install the mounts without dropping the tranny. I've got some film pictures of the mount in place. I can scan those in soon.

If you are looking to reduce driveline bounce, your best bet is to look first to the rear subframe mounts. I believe that most of the driveline bounce is due to the huge amount of freeplay in those mounts.

SVXRide · #3 02-17-2005, 02:42 PM

Quote:

Originally posted by mbtoloczko
I've got the STi Group N motor mounts. An adaptor plate needs to be fabricated from 1/4" steel. I't may not be possible to install the mounts without dropping the tranny. I've got some film pictures of the mount in place. I can scan those in soon.

If you are looking to reduce driveline bounce, your best bet is to look first to the rear subframe mounts. I believe that most of the driveline bounce is due to the huge amount of freeplay in those mounts.

Mychailo,
What are your thoughts as to what could/would happen if the freeplay in the rear subframe mounts was eliminated?
-Bill

mbtoloczko · #4 02-17-2005, 03:12 PM

Hi Bill,

In terms of the driveline, the free play in the rear subframe mounts affects the position of the rear diff. With the huge amount of free play in the subframe mounts, the rear diff can almost freely rotate around the same axis as the prop shaft by a good 15 degrees. In low gears, 15 degrees of rotation equals a significant amount of windup, and with the engine solidly connected to the tranny (manual tranny), the windup leads to lots of bounce back and forth off the rubber subframe mounts mounts unless you are very smooth with the throttle pedal.

In terms of suspension action, the freeplay in the subframe mounts has very little effect. It only affects the position of the inboard lateral links. The position can move up and down, but it would have a minor effect on suspension geometry.

SVXRide · #5 02-17-2005, 03:30 PM

Mychailo,
Thanks for the response. So, if one still had the 4HEAT, then they'd be better off looking to improve on the trans mount?
-Bill

oab_au · #6 02-17-2005, 03:45 PM

I was just thinking about that as I read Johnnys report of his trip home in Hucks car.
As the SVX was never designed for a clutch, the mountings will lack the torsional stiffness that the clutch will impose on it. As Mychallo has said, the rear diff is a spot that has a lot of movement, to cause wind-up, and resualtant shudder.

Replaceing the mounts with something stiffer, is desirable, but expensive. I have fixed problems like this in the past by fitting a torsional link, that runs from the top of the diff, across to the frame, pivoted at both ends. This will prevent the diffs rotation, while allowing its normal soft mounting.

Worth a try?

Harvey.

mbtoloczko · #7 02-17-2005, 04:58 PM

Quote:

Originally posted by SVXRide
Mychailo,
Thanks for the response. So, if one still had the 4HEAT, then they'd be better off looking to improve on the trans mount?
-Bill

No one makes a stiffer mount for the 4heat, so your best bet would be to buy some urethane filler and fill in the gaps in the stock tranny mount. Maybe even weld in some travel limiters like what is used with the Group N motor mounts. Then put some STi Group N mounts on the motor.

mbtoloczko · #8 02-17-2005, 05:29 PM

Quote:

Originally posted by oab_au

Replaceing the mounts with something stiffer, is desirable, but expensive. I have fixed problems like this in the past by fitting a torsional link, that runs from the top of the diff, across to the frame, pivoted at both ends. This will prevent the diffs rotation, while allowing its normal soft mounting.

Worth a try?

Harvey.

There's actually a bunch of free space that the OEM bushing doesn't fill up. A couple of the WRX guys over at NASIOC and Subafreak have had pretty good success by just filling up the free space with some rubber or flexible plastic washers. That removes a good amount of the free play.

CigarJohnny · #9 02-17-2005, 07:45 PM

Quote:

Originally posted by oab_au
I was just thinking about that as I read Johnnys report of his trip home in Hucks car.
As the SVX was never designed for a clutch, the mountings will lack the torsional stiffness that the clutch will impose on it. As Mychallo has said, the rear diff is a spot that has a lot of movement, to cause wind-up, and resualtant shudder.

Replaceing the mounts with something stiffer, is desirable, but expensive. I have fixed problems like this in the past by fitting a torsional link, that runs from the top of the diff, across to the frame, pivoted at both ends. This will prevent the diffs rotation, while allowing its normal soft mounting.

Worth a try?

Harvey.

Harvey, for some reason I am having a hard time picturing this. Is it possible for you to sketch a diagram and scan it for me? It sounds interesting. Thanks for the input!

Johnny

CigarJohnny · #10 02-18-2005, 04:45 AM

Quote:

Originally posted by mbtoloczko

There's actually a bunch of free space that the OEM bushing doesn't fill up. A couple of the WRX guys over at NASIOC and Subafreak have had pretty good success by just filling up the free space with some rubber or flexible plastic washers. That removes a good amount of the free play.

I was thinking of pulling the mounts and filling them with that 3M window sealer. I could have sworn I read here that someone else did the same to their engine mounts... for some reason I'm thinking it was Ron Mummert but I can't find the thread I read it in.

Also want to do it to the tranny mount, which I hear does a fantastic job of stiffening that as well (did find the thread for that one). How hard is it to pull the mounts? I know you have to lift the engine a little from underneath. Do you need to yank the exhaust as well?

Johnny

mbtoloczko · #11 02-18-2005, 08:52 AM

You can fill the OEM tranny mount with window sealer, but the engine mounts are completely filled already. If you are going to switch to the Group N engine mounts, it will be easiest to do when you replace the tranny.

If you want something easy to do in the mean time that will make a difference with driveline bounce (probably not shudder though), get some hard rubber washers and fill in the free space in the rear subframe mounts. Two of the mounts are very easy to reach and do not require removing anything except the two bolts holding the subframe in place. The other two mounts are much more difficult to reach.

In your thread about picking up Huck's 5MT, you mentioned the shudder issue with the clutch. I've got a similar issue (brought on by my own carelessness), except it only happens when the car is cold. Even with the Group N motor and tranny mounts, my car also feels like the engine is going to jump right out of the hood if I let the shudder get carried away (which I don't do anymore).

svxsubaru1 · #12 02-18-2005, 11:00 AM

Quote:

Originally posted by CigarJohnny
I was thinking of pulling the mounts and filling them with that 3M window sealer. I could have sworn I read here that someone else did the same to their engine mounts... for some reason I'm thinking it was Ron Mummert but I can't find the thread I read it in.

Also want to do it to the tranny mount, which I hear does a fantastic job of stiffening that as well (did find the thread for that one). How hard is it to pull the mounts? I know you have to lift the engine a little from underneath. Do you need to yank the exhaust as well?

Johnny

I posted the topic of filling the trannie mount with window filler, and it has had a noticable improvement in divability for the manule. Iam also going to put soem ploy rear subframe bushings on the SVX soon.

huck369 · #13 02-18-2005, 11:23 AM

Johnny,
Your SVX has a standard 95 Impreza Tranny mount, so you can probably buy a STi tranny mount that is a direct bolt on.

Then making the adapter plate for a set of STi motort mounts for the motor should make it all tight.

Bxsvx · #14 02-19-2005, 11:48 AM

where can we get the adaptor plate? That Idea sounds really good of putting the sti mounts.

mbtoloczko · #15 02-19-2005, 02:59 PM

Quote:

Originally posted by Bxsvx
where can we get the adaptor plate? That Idea sounds really good of putting the sti mounts.

There is no off-the-shelf adaptor plate. Someone has to custom fab it.