Purchased a set of Delrin engine and trans mounts awhile back from Level Zero Motorsports. Haven't installed them yet. Curious to see if anyone can provide feedback regarding NVH when compared to other mounts, particularly stock Mazda, Mazda Comp, and Poly.

As it is my daily driver, I need something that isn't going to break my spine. When I purchased them I was not knowledgeable about the material, and was under the impression Delrin was a rubber substitute. There was a quote somewhere that said they do not cause increased NVH, but holding them in my hand I find that hard to believe. They feel too solid to me, so before I installed them I wanted to see what others thought.

 

You will definitely see a significant increase of NVH over the stock rubber mounts. Now whether this is unacceptable to you, that is for you to judge. There is a lot less vibration with the rotary compared to a piston engine so if you've ever driven a piston engine with hard mounts it won't be quite that bad. But you will feel vibrations and hear noises that you've never felt/heard before. These can come and go with vehicle and engine speed.

Personally, I don't find hard mounts on the engine and transmission to be intolerable. But would never use them on say the rear subframe or differential for example. Having driven those cars, the amount of transmission to the body gives the vehicle a feeling of wanting to fall apart over every bump.

 

I went with their Poly mounts and really like them. They give a little more nvh than the worn out rubber ones that were on there but not enough to be intolerable. Once they had some time to wear in most of the time they are barely noticeable, I occasionally get a good vibration at steady throttle around 3500 but a shift and it goes away. The delrin will be slightly stiffer than the ones I have but I dont see them being anything you wont be able to deal with.

 

I have Level Zeros billet aluminum engine and trans mounts and don't find them intolerable with all poly bushings but my fc isn't daily driven. poly mounts would be ideal for a daily driver that you want a little better handling in my eyes.

 

In thinking then that I will swap in the Delrin transmission mounts, but buy poly mounts for the engine. That way the main source of vibration (engine) will be mostly absorbed, and I will have the Delrin mounts to negate some of the driveline flex. If I find the Delrin is too stiff, it isn't a big deal to get matching poly transmission mounts, and if I want something stiffer for the engine somewhere along the way, I can always take out the polys and put in the Delrin.

Thanks guys, this has been very helpful. Once I get the mounts swapped in I will report back with results regard the impact as a daily driver, and I'll see what my family and friends think (as I am more concerned about their comfort than mine). It will be interesting to see how much NVH people notice without being informed any alterations were made to the mounting.

 

As a heads up, you will get NVH with poly engine mounts. I have Himni poly mounts and anything under 2500 RPM causes vibration. Not a lot, but enough that you will start searching for every loose bolt or clip that rattles. Then again, I also HATE interior noise. When my new motor is done I'll be switching to stock mazda comp mounts and a torque damper or Xcessive Manufacturing's redesigned mounts.

 

I'd stick with a matching set tbh. Wouldn't it be ideal for the engine and trans, which are connected to each other, to have the same amount of allowable vibration/play at each end? I can only imagine having the engine on softer poly mounts with the trans on a solid mount causing significantly worse vibrations and possibly advanced wear on the mounts. If the engine moves on said poly mounts the trans mounts would have to eat that movement by flexing the chassis since the trans mounts don't have the same give.

 

Hadn't considered that. Okay, Ill give the Delrin a try all around and see what happens.

 

Installed the Delrin transmission mounts last night, here are my first impressions. Drove to school this morning, as well as doing a few pulls on a back road last night up to about 150 km/h.

For comparison, I will describe my previous setup. I have stock Mazda engine and transmission mounts. The engine mounts look pretty worn, and the transmission mounts were just as bad. The center bushing on my cross-member was rotted away and the sleeve had punched itself out. This was probably the reason that I had massive drive-line flex. Body has 370 000 km. Engine has about 20 000 km. Transmission, clutch, and diff of unknown mileage.

For my new setup, I grabbed my spare cross-member and Y-piece from the transmission in my shed. The center bushing was just as bad, and fell apart. I removed it by burning out the remaining sticky rubber, and sanding it clean with coarse sandpaper until it was shiny inside. Called Mazda to purchase a new one and was informed that the cross-member and bushing are sold as a unit. Considering I have one Rx7 and two transmissions, I don't particularly want a third cross-member, so my father and I poured Urethane into the center after creating a mold. 60A I believe. It worked perfectly. Transmission mounts are (as mentioned above) Level Zero Motorsports Delrin mounts. Installation was pretty straightforward, although awkward due to the position of the bolts. It took my father and I two hours or so, with the transmission supported by a jack and the car over our oil change pit.

The following is basically anecdotal until I can put in the engine mounts as well, as my stock Mazda mounts don't look so good.

With the new setup the drive-line flex is basically gone. It's like I have brand new synchros, as my transmission no longer grinds (I didn't think that the mounts would fix that, but they did).

Noise: There is a slight gear whine noise in neutral that was noticeable, but only until the car warms up. Probably a bearing. During drive, there is a slight humming noise produced, but nothing too drastic. My shift **** rattles slightly, which I had not noticed before.

Vibration: Vibration is slightly more noticeable (although given the state of my previous mounts, it is not surprising that it was shaking a lot. There is a slight but noticeable resonance starting at about 3000 RPM and continuing to about 4500 RPM, after which it seems smooth again.

Hardness: Hardness is very slightly increased. Not too noticeable. I assume this will increase when the engine mounts are changed.

Overall I really like the change. The real test will be when I drive my mother or my friends around, and see if they notice or care about the difference. Will report back after changing engine mounts.

 

Be careful driving with only the trans mounts in, having the 2 different mount materials can break things as they vibrate at different frequencies.

 

Ended up changing out engine and transmission mounts to Level Zero Motorsports Poly Mounts. Got tired after a week with the delrin, as the vibration increased and increased as the rubber engine mounts continued to decay. I quickly realized that delrin mounts all around would be intolerable.

In case someone finds this thread in the future when in a similar situation, just go with the Polys if you intend to daily it. More vibration than rubber, but still well within tolerability.

 

I went full aluminum in my FB.

It's stiff. Like rattles everything in the entire car, not enjoyable for street driving.

Would recommend poly any day over the solids.