Engine Mounts: Compare and contrast
02-23-12, 04:41 PM
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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!
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!
02-23-12, 05:33 PM
#2
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
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
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02-23-12, 06:28 PM
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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
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
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
02-23-12, 08:42 PM
#8
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.
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.
02-23-12, 08:43 PM
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02-23-12, 08:58 PM
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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.
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.
02-23-12, 11:16 PM
#12
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?
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?
02-24-12, 01:41 AM
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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?
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?
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...
02-24-12, 02:35 AM
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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.
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.
Last edited by rumblz; 02-24-12 at 02:38 AM.
02-24-12, 06:37 AM
#15
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.
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.
02-24-12, 09:05 PM
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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?
02-26-12, 12:04 PM
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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.
02-26-12, 01:22 PM
#23
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?
02-26-12, 03:26 PM
#24
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 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.