lets discuss motor mounts
 

with some people getting much more than oem h/p out of their engines now and more and more people tracking their cars and the fact that some models have some miles/time on them--motor mounts are a thing that needs some attention?
Observing a lot of track video( our grp the Ga Rx8 club has maybe 25K track miles on all the members cars!) it is easy to see the gearshift moving a good bit and people report missing shifts while braking hard or in a double apex corner etc it is evident we are getting excess driveline movement.

The rx8 has oil filled motor mounts. It has 3 oil filled chambers.They are rather soft but do a great job in helping the car to be smooth.
It is a 2 piece mount
1- arm that comes off the engine and then
#2 fuild filled mount on the chassis. A single 14mm bolt attaches the engine to the mount.
The shape of the mount roughly speaking is like a fat stubby christmas tree(source pic yourself). The bolt that goes into the mount only reaches a little over an inch. It screws into the metal part on top of the fluid fill mount . Now I am thinking this is part of the problem.
This part of the mount , the recepticle of the motor mount bolt ( you have to dissect the motor mount to see this) is a small upside down christmas tree or arrow shaped piece of metal -its not very big and it doesnt penetrate far into the mount itself. Now on mount compression it probably works pretty good as the bigger part of this bolt holder is absorbing the pressure ---BUT on rebound i think it is a weak design. For example have a friend move your engine by hand and watch the motor mount move--you may be surprised at the amount it does move with so little pressure.

I am also thinking that doing a homemade polyurethane mount out of it may not work as well as it has on some other cars. I think this because the shape of the metal part that the bolt screws into will be a weak point and over time it may fail. I do not know this for sure, it is only speculation. I just dont trust that small piece of metal.
I recently did a cable tie down on the drivers side and it did fix 80% of the movement i was having--but I know this is not the best solution. But it does work for now.
I wonder if there is any way we can make the universal mount from Energy Suspisions work?

Thoughts---ideas??
olddragger

hmm, never really thought about it. the only other option i remember seeing was the solid mounts that Mazsport made. those were mostly to make room for their turbo kits though. come to find out they made the car ride "rougher."

ive always wondered about the mounts

I personally don't think they're necessary unless you're subjecting the car to quite a bit of stress i.e. track driving ALOT.

I ran Semi-solid mounts on my Miata and that car was NVH king! It would rattle your damn fillings out of your teeth.

agreed that you done want it to be too stiff and get all that nvh. But, yes as you said we do track a lot and we are bumping up hp/tq that reveals much more movement.
I call energy suspenions today and they do not have any plans to make a mount and will not make a custom one for less than $100,00. They said they would put you up in a hotel while it was under development for that price. Love those guys!
They suggested to cable them down( i have)
olddragger

guess there is not much interest about motor mounts?
OD

^^^
I was going to refill mine with 60A and call it a day...barring any issue past that. I haven't heard of the aluminum brackets breaking from anyone, have you?

Denny, can you show a pic of where you installed the cable tie down? I'd like to try this soon and go from there. I really would like new mounts and will be watching this thread to see what you come with.

Nic

Nic---PM sent
my cables just looped over the motor mount arm(from engine) ran through each side of the chassis mount via the 2 sides that are bolted to the chassis. I used fairly small steel cable and you only want it snug--not racheted down tight--you dont want to compress the mount any. I did the drivers side only as the cable will only handle rebound. It has worked pretty good but a more permanate fix is in the works. See next post.
Denny

update all on the motor mount analysis.
1-I have 2 mounts coming from mazmart that will be here Monday/Tuesday.
2-Energy suspenions sells there own brand of polyurethane in a 60, 80 or 90 sard A hardness
3- i think there may be a problem with the aluminum insert (where the bolt goes) that is in the mount. It is shapped like an upside down christmas tree and it doesnt prenetrate very far --maybe 1 1/2 inches. It may not be resilant enough for controlling rebound
I am working to modify that.
4- there is also a little ledge on the underside of the mount that I may be able to do something with.

I am shooting for the easiest, most cost affective way of improving these mounts that will also be streetable with very little if any nvh.
olddragger

Got your pm Denny, thanks for keeping me in the loop.

There is interest but I have no input. All I have done so far is replace them.

I am highly interested in this. I have some problems shifting at higher rpm's pretty often, and a few guys around here have as well. Even having the trans rebuilt only to have the same issues due to motor mounts. I personally don't care what the cost is if I can get a pretty solid mount with only a small nvh penalty, I want something better rather than just replacing oem mounts again. Keeps us updated please.

od... this is spoolinmazda from the other sites....

would you consider through bolting the engine mount and use a colar as a pass through the mount? then use the other side of the mount to anchor it?

Im not too engine/mechanicaly literate since im still learning but, mazda told me my engine mount broke and they need to order in a new part, luckily im under warrenty. What i would like to know is what effect does this broken mount have on my car or shifting or w/e, since i have been driving with it broken for some time and my part doesnt come in for another week or so.

Edit* They might have said my "Engine Mounting Bracket" broke, is that the same thing? or different?

Yep going to through bolt it I think but not out to the other side--i have already cut the tip off of that christmas tree thing(extra junk i had around in Fred Sanfords backyard) and that can be done pretty easily without destroying the threads. So longer bolt with an achor in the poly is the plan at this point.
I want to use a bolt there insead of a stud because if the time comes that I ever need to take it off it would be easier? But plans are subseptable to change. Soon as I get the mounts in I will start posting pics/plans. Hell, I may take one off my car this w/e to play with --aint but a 5 minute job..

Darlight--broken motormounts cause all kinds of problems keeping the engine and drivetrain in proper alignment--if you driver her easy --you may not have a problem. But I would not do any hard acceleration or braking.
OD

Crap... Thats not good. Ive been redlinning and going up and down highway ramps... I guess i should take it easy a while, but its just so hard cause this car is so fun to drive.

hang on --but i may have discovered a very easy fix--need to field test first.
OD

oooh.

How's the field test going?

it is delayed as i am placing my big pulley on and i had to order some fuel ijector grommets Car will be running tuesday night and i will update weds/thursday. I am encourged however and if the easy fix doesnt pan out Plan B will. Extral motor mounts should be here today or tomorrow from Mazmart.
olddragger

Ok 1st days tests are encouraging. Has an oh so very slight vibration at idle but unless you expect it you wouldnt notice.
I have a feeling some may want a different option and thats cool , but this one is so easy and cheap. FInal results by the w/e and more detailed analysis.
I am thinking(still researching/testing that we are not having traditional motor movement. It is moving but not like you may think.
The rebound strengh of these mounts is very, very weak. The compression strengh is so-so.
What MAY be happening is, rather than one side of the engine going down as the other side is coming up in the same porportion, the compression side is NOT going down the same distance as the rebound side is going up. So rather than the classical torque movement per se, you have some torque movement (compression on the passenger side) and also more driver side engine lift. Does that make sense?
comments suggestions/discussions all welcome--i could be totally wrong.
By this w/e with pics.
olddragger

A couple of things:

1) The two motor mounts (on opposite sides of the engine) work in opposite directions when the motor is doing its thing.
When accelerating, the right-side mount compresses and the left-side mount stretches.
In decel, the right-side mount stretches and the left-side mount compresses.
You need to look at which of those movements you are actually trying to affect when taking the decision to increase the resiliency of the mounts.
Do you want to reduce compression AND expansion or only one?

2) The mounts also have a range restricting tab that is located on the inboard side of each mount. This limiter is riding in a "slot" in each of the two motor mount engine mounting brackets and reduces the total excursion of the mounts.
Because of the relative "softness" of the mount surrounds, most engines end up near maximum compression all the time when the motor is at rest because of gravity.
This means that on accel, the left-side mount is already near its maximum restriction and the right-side mount has the greatest excursion. On decel it is the opposite.

3) The "third" motor mount is the PPF. Since it is rigidly attached to the tail-shaft of the transmission, any torsional movement of the motor gets translated down the PPF to the diff and its associated mounting hardware and bushings, which are relatively soft.

4) Because of the proximity to the exhaust manifold, the right-side mount get disproportionately hot and loses quite a bit of resiliency as the durometer hardness of the rubber decreases. It also fatigues earlier because of this.

So, the problems you are trying to address are not really about rigidity, but range of motion and pre-load.
Since we are only concerned with NVH at low-load and range of motion at high-load, you can begin to see that the "solution" is not best addressed with increased durometer hardness of the motor mount's rubber compound.

thanks for the input MM and I agree. What you have said is exactly what I am attempting to address with the mounts. So far so good . I am looking at stabilizing the total movement while not causing excess nvh.
i have not done anything with the PPF although as you have said there is improvement that can be done here. I wonder if the 09 ppf and diff brace will fit our cars?

I will post by Sunday pics and results I have seen. WIfe's birthday takes priority.
OD

Speedsource told me they quit running solid mounts because the aluminum brackets between the engine and the motor mount were breaking as a result