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

um, maybe i'm missing the point...

but what about those engine torque dampening rods the FD guys use? would that help at all???

yep team--nothing solid in this.
the engine damper set up is a band aid and expensive.
olddragger

there will probably be 2 options on the mount----
1- the simple and easy that gives more support
2- the poly type.
You need to remember also that these are "break a way" mounts in the event of a collision. Thats an important feature not to be ignored.
olddragger

+1 MM
That was fun readin' I would agree that there is a lot more to this than simply stiffening the mounts but when done right I think this car could benefit a lot from this type of upgrade.

i have found some interesting stuff.
1- the engine mount under stress can actually bend some and develop an outward slant. may not be enough to worry about) just note that you may want to check yours.
2- the metal receptacle for the mm bolt (about 1 1/4 to one and half inch long) is mounted into the upper part(duh) and that top part of the mount is solid rubber.. It is soft, slightly compresses using just my hands. The 1st top metal ring of the mm is where it stops.
3- what surprised me was after you clean the mount out of all the oil and plastic stuff it seems that it is just as firm as was before. If there IS a difference its very slight. WTH? I dont get that.
4-- The mount will clean out very well leaving a nice smooth cavity for any polyurethane. if you want to do a poly fill you will still have that top part of solid rubber--this could be a good thing.

Now--- I have been riding around with inserts of 60a harness rubber. inserted between the two spaces of the mm and the mm arm Those little ledges we have talked about. This did limit the amount of compression and rebound experienced. For a NA car this should work. Simple rubber inserts. Pictures tomorrow.
I was still getting some movement, but not nearly as much. Both on acceleration and braking.
It did have a very very slight idle vibration but you would have to expect it to notice it.
I would suggest taking the load off of the mount--loosening the mm bolt a little then place the inserts--the top one will have to be thinner than the bottom one.
This should not overstress the mm arm as the inserts do have some give to them.
How easy is that!:)

For us guys that are FI and are dealing with more torque and horses, i dont think the above will be enough. So I have cleaned out one of my mounts and ordered the poly from energy suspensions. I am more encouraged in using the poly because of the solid rubber part that remains. The part that anchors the bolt receptacle.
Keeping this will maintain the collision break a way feature (you never know--crazy drivers out there:)) and it should be of help for any nvh issues. I think both mounts need to be done?
Drive train stability( accel and braking)l on track--i need them both!
I have a few pics i will post tomorrow to illustrate.
Any comments, suggestions ideas welcomed---money too---meh!
rotor on dudes
olddragger

I only mentioned it as supporting on-topic info relative to the subject

so noted ---appreciate it Team.

Ok ---here are the results I have seen on my car. Now please keep in mind that i have over 300 hp to the wheels and over 200 of tQ.
My engine was moving a bit--good 2 inches. My mm's are good. Some of my friends cars (NA) was actually moving MORE. I have posted track vids showing how much the gearshift movement is occurring on track. I do not know the condition of their mm but i do know they are anal about their cars.

!st thing I did was to cable the drivers side mount with a small braided cable looped over the mm arm and then through the arms of the mm itself. That actually worked pretty good but for track you would have to cable both as this method only effects the rebound or the upward movement. Not really practical for the street --but in a pitch --yep it works.
With this method I was only getting approx less than 1 inch of total movement and no real noticeable nvh. Sudden acceleration response actually improved---this was obviously felt.

2nd-- see the pic below that show the ledges on the mm arm and mm itself. That is an oem design to limit the maxium amount of movement by the mounts. SO being the back yard monkey mechanic that I am--i thought of placing hard rubber inserts into those spaces to further restrict movement. This work very well for me. I would still get approx 1 inch of movement--sudden low gear acceleration was still more responsive (more snap:) ) and very little nvh. My rubber inserts was approx 60-70 sard A hardness. You would have to make your own for this and just use a little adhesive to further secure them. The one in the picture was not premently mounted --just placed there to show ya. It can be made to fit much better.
FOR A NA CAR THIS SHOULD WORK. Very inexpensive to do and it doesnt take long to do it. Just make sure your mm's are good and then add the inserts. TaDa!

Now for us FI guys---we always need more. My earlier post is where I am going. I think the poly plus the solid rubber up top will produce a good strong mount. One thing I am going to watch for is --how much is that solid rubber piece actually giving. It may be too much? Dont know yet.
With the poly it should make a big difference on compression only. I dont think it will affect the rebound and therefore both mm will need to be done?

To clarify a earlier post in which i was thinking the mm with the internals and oil removed seemed as hard as the intact one? Its not. It is about 30% less stiff judging by the weight added(weight lifting plates) to both before movement was noticed. On rebound it doesnt make any difference. I hung a MM then tied wgts onto it until i saw it start to stretch. No difference noticed between the two.

here are some pics to illustrate
the 1st picture just shows the size off the metal insert that goes into the mount, this is what the bolt goes in. notice the shape and lenght.
https://www.rx8club.com/attachment.p...1&d=1248618672
https://www.rx8club.com/attachment.p...1&d=1248618672

hope some can use this info.
olddraggeri

revo tune in .jp has a motor mount solution out. don't know what it is supposed to cure.

http://revo-tune.jp/info/data/upimages/n90301.jpg

Interesteing read OD, i often have shifting problems that are not transmission related and my PPF is torqued to spec and perfectly aligned.
Need to find some poly here and a couple of motor mounts to drill out!

A question: what does nvh stand for?

Giorgio

noise, vibration and harshness. reminds me of an ex wife

I dont understand how that would really work--must do something

OD

I translated the info from their site, here it is. Maybe someone can understand it...some of it is lost in translation.

Suspension
semi rigid engine mount color

Conformity model : RX-8 (SE3P)
product code : RSE3-SREMC
price including tax : 18,900 Yen

As for the engine mount of RX-8 when travel distance advances with oil enclosure system, there is 0 element that installation position goes down.In addition there is a clearance beforehand in the genuine mount, and between the color there is a roll G to catch when the engine tilts, it is the structure which for the first time becomes rigid.
In order to insert the clearance part, the mount color which is installed is this commodity.
If the mark is squeezed to only race/lace and sport travelling, rigidity conversion is effective, but in the car case reason, 4 sea tar sports the comfort it cannot make sacrifice.Because of that semi the material and form in order to make rigid were tested and the engine mount color became the product of [jiyurakon] make.
Wobble of the engine mission and the like with the accelerator on off of the engine is held down and shift change becomes easy to do.
While leaving the change of engine position in the midst of travelling in minimum, you hold down the vibration and road noise to the utmost.
It becomes protection of [enjinmaunto].
It is minor front and back installing possible.
Commodity price is 2 (one unit).

I also found on their site that this engine mount mod works on an exchange process. You must send them your mounts in exchange for the modded ones. It's about $400 USD plus shipping costs.

how can you do that if you cant read japanese etc? 8)

I cans read Japanese, that's how silly. :p

Thanks OD

@I8U, for what i understood those are not complete reinforced motormounts but just collars to help distribute the load and weight over a larger\harder surface. I don't personally like them.
For the price that OD mentioned some posts above i would be more than happy to send some motor mounts to Energy Suspensions though :)

$100, 000!!!!!!!! Hell, I will make any mount you want for that! Out of titianium!

Update---i have filled my reamed out MM (used a 2 inch hole cut drill and then a long screwdriver) with the poly and now have it drying under a heat lamp at home. Its less than 36 hrs now but it does seem to be drying pretty fast.
If this works out and yall dont want to do your own, then I will be willing to do one on exchange basis for you ---how much should the charge be? I could ship it out the same day I receive yours--overnight it etc. I have an extra one here that i can have on standby.
Or you could buy a used mount --, OR check with a dealership as they throw the old ones away when they put the new ones in.
olddragger

Ok wait, we use the commas for the cents and not for the thousands here!
Anyway how much do motor mounts weigh? Shipping could kill overseas guys like me, poly is pretty cheap in comparison!
When are you installing it? i have like 2 or 3 spare motor mounts hanging around i might to that before september.

prob install this w/e.
OD

Great! Def. looking forward to reading the results!

What you do with Jeff should remain private between two adults.....

Lol--eek:
olddragger

poly mount is on and so far so good.
OD

Hey OD,
let me know if you want to test if those motor mounts are Pizza proof ;)
Did you end up using energy suspensions' 60A poly?

yes-- and let it dry for a few days just to be sure. So far so good. Still some movement but not much. No noticeable nvh, sudden accel has a better snap to it and the break a way safety feature is intact.
I will be at Road atlanta for a nasa w/e on 8/8 for the REAL test.
I may do the drivers side also--just to see if i notice any difference.
olddragger

Mumble mumble... i will do both of them just to keep the thing balanced. Wonder if this reduced play will help decreasing PPF stress as well. Imho this, and some extra bracing and our transmission could last a bit longer.