Engine Mounts: Compare and contrast
 

I've heard and read a bit of information on the differences of engine mounts. (Commonly referred to as "motor mounts".) - But I've not found enough information or even product reviews to differentiate between all of them. If anything... I am more confused.

There are MANY different styles of mounts and mounting materials. Solid billet aluminum, solid delrin, polyurethane, "competition", hockey pucks, stock mounts, industrial vibration absorbers (John Huijben), et cetera.

I'm seeking information on the advantages, the disadvantages, most vibration, least vibration (vibration reduction), recommendations for street use, recommendations for track use, best quality, and the longevity of each mount.

Now, I understand not everyone has experience with each and every type of engine mount available... But some of you know what the hell you're talking about when it comes to these kinds of things. Feel free to post great bushing sets to complement specific engine and transmission mounts.


Looking forward to hearing from all with personal experience and great knowledge!

As I understand it, the motor and drive train vibrates by virtue of the rotating parts, which are probably not perfectly balanced (just within a defined spec). The mounts, isolate this vibration, to a degree that is inversely proportional to the hardness of the material.

So, at a given RPM the motor is going to vibrate some amount, we'll call it 10 (technically its a frequency in hertz, but that's not really important). The stock mounts reduce that to 2 (made up number, I'm illustrating a point, not the actual math), so you really don't feel the vibrations through the chassis. This makes for a comfortable ride.

Solid metal, might reduce the 10 to a 9, so you are likely to feel the vibrations through the chassis. Various other materials, like plastics and different grades of rubber will be somewhere between 2 and 9.

Now, if you take a 10 vibration, and reduce it to a 2 using the mounts and the chassis, what happens to the energy of other 8 "vibrations"? Well, the motor moves about and disperses that energy into other things that it is connected to. Which means stresses are going into the bell housing, things are getting misaligned (slightly) adding wear and tear and other undesirable effects.

So as with suspension and many other vehicle systems, its a trade off. You can make the engine long lived and high performance by having stiff motor mounts, but the ride might not be comfortable. It all depends on your application.

The "average" person isn't likely to be racing there car and will likely want a smoother, more comfortable ride. Since they are not at 9k rpm for the life of the motor, its probably ok. the bad effects are minimal.

A racer probably doesn't care about comfort and wants max power/reliability at 9k rpm, so they will likely want the stiffest motor mounts they can afford/are allowed by the rules sanctioning them

im not reading this post, but i will say that AWR mounts are by far the best i could imagine.

you are right in that the engines vibrations/motions, do indeed have to go some where, however to say that the engine will live longer because its on stiffer mounts is a little out there.

also its physics, so the chassis can transmit vibrations to the engine too.

the stock mounts are soft, so you don't feel the engine, however they break on stock cars, so people want to look for something stronger... with rubber this means stiffer.

personally i like the vert mounts, they are stiffer than the coupe mounts, but don't add much vibration.

the competition mounts add a noticeable amount of vibration. fine in a race car

i did ride in a solid mount car, and that was too much too, although if it was some high hp race car, then it would have been fine

Yeah, reading what wrote again, living longer is a relative thing. There are many variables contributing to engine longevity and I probably should have left it out.

Hey I have competition mounts and the vibration, I feel or hear in the cabin is little to none. Solid mounts is another story definitely race car.

Hybrid

I've always wondered how well hockey pucks stand up as motor mounts...

Mazdacomp mounts if you want something stiffer but still drive the car on the street.(barely more vibration than stock)
Poly/HDPE for competition/very little street(will vibrate and cause rattles)
Delrin/Solid Competition only (constant noise/vibration)


I imagine hockey pucks are quite stiff, like a high density poly mount.

This is less of a "Hey these mounts are bad ass"... And more of an informative thread. Those AWR mounts are interesting. Any experience with them?... Or are you just saying that they're awesome? Has anyone shelled out the $199 for them??


gtouch made some for his car. He's not yet driven on them...

gtouch: Build Thread

http://desmond.imageshack.us/Himg171...jpg&res=medium

It's been my experience that good ideas are written down and archived so that others can learn and build onto these ideas.

Try google.

Search for books on vehicle dynamics and engine vibration dampening. Carroll Smith wrote some good ones.

I figured this thread might be a "good idea".

I'm looking more for personal experience and comparisons, rather than technical data. Not that my experience with a particular mount would be the same as another's experience... But I'm seeing how many stray from the stock mounts, and are willing to share.

If the stock mount broke, replace it with another stock mount. Everything has a service life. 20+ years of absorbing vibrations, heat, and possibly oil will wear them out. There's nothing to upgrade or downgrade. The mounts are there to meet certain design goals. If you want a louder cabin, go stiffer. There is no performance to gain in a stock car. If the engine is making so much torque it's ripping brand new mounts...that's an entirely different problem.

So which is it, did your stock mount break on your stock engine or are you dropping the clutch at redline on slicks? Maybe both?

Neither, sir.

This was started as an informative thread for EVERYONE. This thread is not for my own personal gain. I respect you as an RX7 Club veteran, but your statements do not fit the criteria... Please, keep to yourself if you have nothing to offer to the community. This is a particular topic that is not commonly covered.

Now, let us proceed...

I got a set of polyurethane mounts for my car. The ride quality isnt really that bad, I dont even notice it anymore. I did however get polyurethane tranny mounts as well and I get a lot of noise in cabin from the shifter because of them, but its nots that bad. The sound/vibration from the motor mounts only really kick in big when you start of super slow in 1st gear and thats only for a couple seconds. The old rubber stock ones caused the engine to move quite a bit. The polyurethane ones gave my car better response when I step on the gas, I really like it. I'd recommend polyurethane, you'll get used to the ride real quick especially after they've broken in. However you could go without the tranny ones if you'd like for an even better ride quality.

As for solid mounts, they'll give you even better response, but they'll vibrate like crazy. Theres no dampening whatsoever, its just a solid piece of metal contact from the engine to the chassis. I wouldnt recommend it for a daily driver, only for track application.

That's a "my bad".

My experience: Found a broken engine mount and squishy, saggy trans mounts on my daily driver. I bought MMR engine and trans mounts to "upgrade". The vibrations were so bad that at high rpms the dash idiot light surround trim would vibrate out of place. Not a classy move with company in the car.

The other issue is compliance. All that energy wants to go somewhere and the rubber which isolates the drivetrain adds compliance which takes away stress from more critical areas like the transmission gears, differential gears, and driveshaft u-joints. The soft rubber is the weakest link for good reasons: safety and reliability. The rubber absorbs the stress that the rest of the "metal on metal" contact points can't. Soon after installing the MMR mounts the driveshaft cracked at the rear u-joint.

I assume you've gotten rid of the MMR mounts since then? That doesn't seem like a very good time. If you've replaced them... What did you replace them with?

i run solids in my street car

it really doesn't vibrate much unless you lug it at a low speed in a high gear example 35mph in 4th or 5th gear

Stock rubber mounts.

I'm happy with the competition mounts I'm using. Vibration increased very slightly (of course I was used to the stiffer vert mounts), and the engine barely moves. Anything stiffer? No thanks.

buy himni mounts!

Stock vert engine mounts are different than stock coupe mounts?

I should be able to give some input concerning the RE-Speed delrin mounts after my car gets back on the road tomorrow. I just dropped them in but haven't even started the car with them yet.

^^^This.

I have the entire MMR drive train set (engine mounts/ trans mounts/ rear diff mounts) and it rides very smooth with almost no noticeable vibrations except in the aforementioned circumstances.

I had tired stock mounts and the vibrations were actually worse, the trans used to miss 3rd gear under load constantly, I thought the synchros were bad....nope. Just too much drive train movement.

As far as causing damage or significant vibrations, you should look into the condition of the other parts of your car. Also, there is a reason the solid mounts for the drive train are sold as a set, if you only have solid engine and trans mounts and the diff is swaying all about where do you think the stress will go?

I have solid aluminum engine mounts, and as mentioned before, it only vibrates a small amount at low rpms / heavy load.

I had a car with poly engine mounts, and its vibration was far worse than my Rx7 with solid aluminum mounts. I'd think that polyurethane mounts would have minimal (and I mean MINIMAL) flex, which would probably be worth losing the vibration over. But like I said, the vibration from the solid aluminum mounts is hardly noticeable.

i haven't seen anyone with a rat-fink picture in years lol

Yep. Different part number. It was apparently one of the modifications made to compensate for the lack of a roof. http://www.mazdatrix.com/mounts.htm

Different part numbers but what's really different?

They are stiffer...

From my experience, with modified cars in general, I've been noticing more and more that polyurethane doesn't have good longevity.
I would either get new rubber bushings or go with delrin or solid

I've also read this in a few different threads.


I've been interested in the polyurethane mounts, but I've not heard much about them. So far, it seems like stock rubber mounts have the best of both worlds... Durability without too much vibration.

Why would Mazda make the vert engine mounts stiffer?

When I bought my mounts I did some research and found that the factory mount material absorbs both compression and tension. Though it looks like a puck with a bolt going through it like the rest; both bolts are bonded to their own plates in the center of the mount material, with rubber between them so it can compress and expand to absorb, well, both compression and tension.

most of the "puck" style mounts that you get now, including the ones I purchased, are basically a puck of poly/steel/rubber/derlin absorbing compression forces while the bolt running through it absorbs tension, which under certain circumstances gives vibration/load a solid path to the subframe.

There have been comments of the bolt breaking though I've yet to have any experience with this in terms of my car or others, nor have I seen pictures of this.

(sorry since this is an informative thread I thought I'd shed some light as to how they work comparatively.)

As to the AWR mounts; yes they're 200 bucks.
AWR offers the only aftermarket mount(not stock/mazda comp) where all of the forces are absorbed by the polyurethane bushing versus the both the mount/bolt. And since their mount has more engineering around the problem than what is essentially a hockey puck with a hole drilled through it has, they charge more for their solution to the problem.



That being said: I have a set of Level Zero Motorsport's 95 Durometer Hardness Polyurethane Engine and Transmission mounts; now that they've broken in they are pretty comfortable, they transmit a little vibration, nothing really bad, still really stiff. I am happy with my purchase, I'm in my twenties, and my car is a daily driven turbo convertible.

I made mine, they are out of A2 tool steel.

PROS:

SOLID AS FUCK
FREE! (just cut out of some round stock laying around)

CONS:
HEAVY AS FUCK

I made delrin mounts in my machine shop class. When I went to go buy hardware, the people at the hardware store recommended grade 5 bolts because they don't snap. They'll bend before they snap. Those guys do a lot of top speed cars in the salt flats

Because the whole chassis was radically modified to make it stiffer. There is an extra front subframe brace behind the oil pan, the firewall is stronger, the a-pillars are stronger, the floor pan is thicker, the area behind the seats is reinforced, the frame rails are thicker, the top has a built-in roll bar, there is a built-in rear strut bar in the form of the wall separating the trunk and passenger area, and the sway bars were larger than in the NA coupes.

My guess is that they went with stiffer engine mounts to help keep the drivetrain weight from shifting during hard cornering.

J9FD3S mentioned the difference above, and I've read it in a few places. I think there is a thread or two that Icemark may have posted in.

^What he said...

i went from stock/torque brace to AWR to solid on a cosmo swap. the awr have a sleeve of polyurethane, enough to tone down the vibrations, but not enough for it to flex. its brilliant. welds are great, great metal, zinc coating. totally worth it. im late, im late!

Yes. Sotck vert mounts (FB67-39-040A) are a different part number than coupe mounts (FB01-39-040A). Stock N/A and T-2 coupe mounts are the same. I will take RR88's word for it that the vert mounts are stiffer than the coupe mounts (ditto for trans mounts).

The AWR's look VERY appealing... And fancy!

They're really worth the $199.99 ??

http://www.protegegarage.com/img/p/766-1530-large.jpg

Reviving an old thread but I couldn't find any recent information in the past year.

I went along and ordered from Himni Racing. I ordered the FC Polyurethane 2A Street Motor and PolyurethaneTranny Mounts. I was a tad hesitant with the mixed reviews due to communication and delivery issues others had explained. I emailed them regarding their inventory and they responded to my email within 24hrs. The parts got delivered quickly. A few other emails were a little slower but that mainly due to the COVID-19 short staffing. Products look sturdy and well made. Based on personal preference the only thing I'm not crazy about were the the allen head bolts for the motor. Something I can easily switch out.

Himni Racing 2A Polyurethane Motor Mounts
Himni Racing Polyurethane Transmission Mounts
https://cimg3.ibsrv.net/gimg/www.rx7...fb4101e14.jpeg