Subjective Motor Mount Impressions

[WBVenom]

I wrote this up as a response in a for sale post, and thought I would post it in a more visible location as a reference for posterity's sake:

I have used the following motor mounts with the following results (and my subjective opinion in parentheses). Both cars have lightweight single-mass flywheels with sprung-hub clutches, so vibration induced by the flywheel/clutch assembly is likely worse than stock.

OE BMW E46 Non-M Motor Mounts:
BMW E46 323Ci: Very low (acceptable) NVH at low RPM. Very low (acceptable) NVH at high RPM. Poor motor control.
BMW E46 M3: N/A (have not tried)

OE BMW E46 M3 Motor Mounts:
BMW E46 323Ci: Low (acceptable) NVH at low RPM. Low (acceptable) NVH at high RPM. Moderate motor control.
BMW E46 M3: Low (acceptable) NVH at low RPM. Low (acceptable) NVH at high RPM. Moderate motor control.

RevShift Polyurethane 80A Motor Mounts:
BMW E46 323Ci: Low (acceptable) NVH at low RPM. Low-moderate (acceptable) NVH at high RPM. Good motor control.
BMW E46 M3: Low (acceptable) NVH at low RPM. Moderate (unacceptable) NVH at high RPM. Good motor control.

Turner Motorsports Polyurethane 70A Motor Mounts:
BMW E46 323Ci: N/A (have not tried)
BMW E46 M3: Moderate (unacceptable) NVH at low RPM (idle only). Low (acceptable) NVH at high RPM. Excellent motor control.

Note the inversion of the Turner Motorsports Polyurethane 70A motor mounts' relationship between NVH and RPM. They only induce some noticeable vibration at idle. Amazingly, at all other RPM all the way up to redline, they are smooth as butter. No other mount behaves this way. Potentially accomplished by their statically-preloaded poly within the aluminum housing. Every other mount I have tried results in higher NVH with higher RPM, typically peaking at various resonant frequencies throughout the range. Turner has really pulled off a miracle here and somehow made a mount that is smooth throughout the entire range, except at idle, where it is a bit too much vibration for my liking. I really wanted to keep them in due to the buttery smooth operation throughout the RPM range, but the vibration at idle was just a bit too much for me. Admittedly I do like vibration to be nonexistent at idle. If you were to increase idle RPM, it would likely solve this issue. They are a perfect weekend-only / track day car motor mount.

Note also that in my experience, transmission mount type has a larger impact on cabin NVH than motor mounts do. OE BMW motor mounts with even soft ECS 70A poly trans mounts result in too much cabin vibration for me. The only trans mounts I will run are OE BMW, Rogue Engineering (rubber), or UUC's NLA gen 1 (rubber, not poly).

[Obioban]

Eh, everything is subjective. I've never met a non OE motor mount I didn't find unacceptably NHV filled.

[WBVenom]

Agreed. I am currently running OE BMW M3 motor mounts in both cars. I would likely run OE BMW Gruppe N if they were not NLA, based on davidinnyc's endorsement.

The captured and preloaded poly design of the Turner Motorsports 70A motor mounts above is noteworthy, however, as they really are smooth as butter above idle all the way to redline, while accomplishing excellent motor control. Pictured below. That is aluminum you see in black, with the preloaded blue poly peaking out from between the outer and inner portions: