Polyurethane vs. Stock Engine Mounts – A detailed comparison

This one was definitely long overdue. This video is actually the spawn of my most successful video How to make DIY polyurethane engine mounts. A lot of people asked these two things in the comments.

  1. How have my DIY polyurethane engine mounts held up?
  2. How do my DIY polyurethane engine mounts compare to the stock ones?

It actually took me quite some time to answer these questions but here it is:

Now there’s several reasons why I couldn’t answer these questions sooner. First is I didn’t have any stock engine mounts. I destroyed mine while I was making my DIY polyurethane ones. Second reason is that I actually wanted to give my polyurethane engine mounts some time to see how they perform and hold up.

How did they hold up?

I had these  on my car for about 10 months and 1000 miles. Yeah, I know, I should drive my car more. But for that period of time they actually held up really well. As you can see in the video there is zero cracks or faults and everything is just as the day I installed them. I have to say that I am really proud of these guys, what they done and how they worked for a total cost of $ 25 is pretty amazing.

How do my DIY polyurethane mounts compare to the stock ones?

This was a little bit harder to answer and I wanted to offer an actual visual comparison where viewers will be able to see for themselves instead of relying on my description or something else that is entirely subjective. So here’s  what I did: I kept my poly mounts on the car, recorded vibration, noise and engine movement and then took a test drive and a few timed 0-60 runs. I then came back to the garage, took the mounts off, installed the stock mounts, recorded vibration, noise and engine movement and then took another test drive and a few timed 0-60 runs. I recorded vibration using a bowl and some water, which worked surprisingly well, while an audio software called audacity handled the noise recording.

Vibration: Polyurethane engine mounts definitely vibrate a lot more than stock engine mounts. This is for me the most noticeable difference and to be honest the biggest downside of the polyurethane engine mounts. The vibration gets extremely tedious in city driving conditions and the noises of the rattling plastics that come and go as you rev through the rpm range will become irrelevant only once you start driving very aggressively and completely focus on going fast.

Noise: I have a loud exhaust so the maximum noise recorded remained the same, but there was still a difference between the polyurethane and stock engine mounts to be noted, and that is the way that the sound of your engine and exhaust is transferred to the cabin. The sound of your engine and exhaust will actually sound nicer and crisper inside your cabin with the stock engine mounts on. This is probably to do with some complex physics related to sound travel that are beyond my comprehension, but that fact remains that with the polyurethane engine mounts the sound resonates differently and in my opinion is not as nice. You can hear the difference in the video and decide for yourself

Engine movement: This one is a no brainer. The engine is almost rock solid with the polyurethane engine mounts, and moves noticeably more with the stock ones. This is the thing that influences the way the power delivery feels to you as the driver.

Driving impressions

The differences in terms of vibration, noise and engine movement are obvious to everyone. But the differences felt when driving cannot be quantified and are best understood when experiencing it for yourself. With the polyurethane engine mounts your car and engine will definitely feel more agile and responsive. One of the situations where this is very obvious is when you floor the throttle from low rpm, you can feel that the engine instantly starts giving it its all, and you feel the power delivery start through the entire car, as the vibrations are now transferred almost everywhere. This is actually a very nice feeling. It’s especially enjoyable to drive enthusiastically on a twisty road and experience the power delivery come and go. Mashing the throttle becomes even more fun, since your car really feels more like a race car now.

More horsepower and torque?

If you browse around the forums a bit you will notice that some people actually claim stiffer engine mounts will increase the amount of horsepower and torque transferred to the wheels. This, of course, is absolute nonsense. You could install solid engine mounts made out of diamonds and your horsepower figure will remain absolutely the same. The only thing you are changing is  the way the car behaves, i.e. the feeling of the power delivery. You cannot increase hp and torque with stiffer engine mounts, the only thing you can do is shorten the time it takes for that hp and torque to be transferred to the wheels. My 0-60 times with the polyurethane and stock engine mounts also support this point, as there was no significant difference between acceleration times with polyurethane and stock engine mounts.

Conclusion

Whether or not polyurethane engine mounts are a good or bad choice all comes down to the application of your car.

If you are installing them on a car that will spend the vast majority of its time on public roads polyurethane engine mounts are honestly a stupid idea. Why? Because polyurethane engine mounts come with very noticeable disadvantages and advantages. Driving mostly on the streets means that you will mostly be harnessing their disadvantages, and experiencing the benefits not as often as you should.

On the other hand if you are building a car that will see a lot, or at least significant track usage polyurethane engine mounts are a great idea. You will get to harness the benefits, while the downsides, vibration, noise, and overall harshness (NVH) are going to be side-effects of little relevance.

 

 

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