so here we go, from the man himself.
It was good to speak to you this morning. The parts are on the loaded dock ready to go. The com mounts have an orange colour code and nylock nuts on the bottom
I have cobbled together a couple of graphs which help (I hope) explain the way the engine mounts perform.
All engine mounts have a resonance condition, just like a road spring. The amount of resonance (magnification of vibration) depends on the damping. The graphs show different damping conditions. The more damping the lower the resonance amplitude but worse vibration isolation at higher engine speeds. Polyurethane is typically around .8 damping ratio and natural rubber (our mounts) are around .2. This gives significantly better engine vibration isolation performance for the same mount stiffness.
The Fast Road graph indicates the engine running range is in the "isolation" part of the graph where all engine vibration is isolated to some extent. The Competition" graph shows the resonance frequency falls in the running range of an engine but below the normal operating range for a race engine on the track. The extent to which this resonance if felt, and it tolerable depends on the balance and firing smoothness of the engine and tolerance of the driver!
We measure vibration when developing a mount system and work to OEM guidlines for vibration isolation performace.
I hope this helps.
Regrds
Phil B
ok heres some graphs
Anyone thats an engineer want to jump into this data a little deeper and chime in, please do.....
Re the tranny mounts, stock that is ;-)
I have just seen the post on the Z forum.
Regarding the transmission mount I would like to add the following.
The "wasted" design is an optimum shape for a bobbin type mount. It reduces the stresses adjacent to the edge of the bonded part and makes it less prone to pealing away. I don't think I have seen a single OEM mount failure that has not been down to some other factor such as oil contamination.
It also is relatively stiff for its size and the shape helps to distribute the stresses over the bond area. There is not enough space available to put a different design solution in there that is any better, we have spent hours looking at it.
The only way to improve it, by improve I mean reduce movement and make it fail safe, is to change the mount arrangement altogether and replacing the crossmember as well. BMW have done a great engineering job of the aluminium crossmember and it is super light but if we stiffen up the gearbox end it will have to take more fore-aft loads which means making it stronger so it may add some weight. It is something we want to look at but the E46 cross member that we have been working on has taught us that the characteristics are critical, especially for a road car. Its not just a case of throwing something in that's stiffer and hoping for the best.
It would be great to do a complete system
Now..... just to confirm the Fast road are 4x stiffer than stock the comp, are 8x stiffer than stock!!!! Thats serious!! lol!!! OF note is also that the only area thats of concern is the resonance that happens at around idle on the fast road this has been tuned by using a stiffest rubber possible before the resonance occurs, on the comp this resonance happens right at the idle rev range, so it MAY , repeat MAY..... make idle feel like a diesel Truck, but equally, they arent sure.... they may with the inherant balance of the straight 6 config be OK, im a hardcore typa guy and i will give you honest feedback on these....
unless their are absolutely unlivable i will most likely leave the comp ones in for the added stiffness and control of the motor, anyone with an FI s54 knows that the motor moves around abit, with the tight clearance of the s/c intake, i can just, and i mean just see an abrasion mark where it "brushes" the underside of the hood, this will only happen at the track when everything is red hot, so the added control for my engine is essential :-)
This is a lot of data for you all to take in so, discuss i guess!!