Performance mounts for 4Kq

[JShadzi at aol.com]

Comments inserted..

>For this kind of damage to occur the car would have to be in rally type
>conditions, I don't buy it for a second that this is caused just by solid
>subframe mounts.  Those only get a work out in cornering, and with stock
>rubber control arms you still have some sort of vibration and shock
>suppression/dampening.

The two instances I referred too were cars that were being race prepped before any sort of roll cage or seam welding had occured, and both cars used delrin a-arm bushings too.  Driving on the street is much more punishing than most track driving, I don't have any experience with this issue on Rally cars, good or bad.  Again, I stated that it was correlated, I don't think either one of us actually has the time or equipment to determine the true mode of failure.

>With the solid snub nose, you basically move the pivot point for engine
>movement up front (natuarally it is about the driveshaft or motor mounts).
>This increases the movement in the engine and tranny mounts (especially
>those due to the distance from the pivot point) probably causing them to
>fail prematurely.  For the whole set up to work properly you have to make
>every mount solid or at least two more.  The solution to this would be a
>solid tranny mounts (or at least way stiffer than they are).

Your analysis is incorrect, there is no shortening of the motor mount life, the I5 natrually rotates around the driveshaft, the snub mount is situated a little above this point, the motor still rotates around the snub mount, you just don't get the side-to-side jiggling caused by the stock setup as it oscillates due to soft dampening.

>As for the bearing support, I have seen someone struggle for weeks to get it
>to work without vibration, it's almost impossible.
>Again, making one thing solid while having the tranny and rear diff on soft
>bushings means that the driveshaft will never be aligned and perfectly
>straight due to engine and rear diff movement, it works on race cars because
>everything is solid and the propshaft is always straight...

Yes, the Delrin mount requries a very well balanced driveshaft and a firm mounting system.  Again, tranny moutns can be firmed up greatly either with Audi Sport units or the epoxy puddy I mentioned earlier.  Of course, the more stiffening that occurse, the more vibration is transferred in NVH.

>Anyhoo... I think these are great parts however there are certiain designs
>that have to be accompanied by other mods to work properly.
>Just consider the impact of the design.  The good and the bad and the
>ugly.... ;)

Agreed that a chassis is a system that needs to be balanced, and it also depends on the builder's goal for the car, whether comfort, performance, race, etc.

Javad