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New Vorshlag BMW Motor Mount Design

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  • New Vorshlag BMW Motor Mount Design

    2013 Product Update - Vorshlag Competition Motor Mount for BMW E36/46/E92 M3

    Vorshlag designs and builds a line of modular, bolt-thru, competition style motor and transmission mounts for various BMW chassis with BMW motors, which we introduced back in 2006. These are meant to replace the soft rubber and/or hydraulic filled "luxury" driveline mounts that the factory uses in these sports/luxury cars. The relatively tall and heavy straight-6 engines used in most BMWs can lean significantly when driven hard, which can make the body-mounted shifters miss-align and if you are particularly unlucky... money shift. It is an age old problem with these cars when raced, and almost every BMW racer has either had this happen or knows a friend who has mechanically over-revved an engine due to a "downshift instead of an upshift".



    We make the mounts modular so that different durometer polyurethane and sometimes even Nylon bushing inserts could be interchanged, to change the transmitted NVH or to upgrade the car, if it went from a street to a race car. There is also a line of Vorshlag Competition Transmission Mounts, made with a similar bolt-thru design. We tweaked the various transmission mount insert materials to work in concert with our motor mount bushings, which rarely had the same durometer in the front mounted motor and rear mounted transmission mounts - due to leverage differences in those locations. These work well in the various 6 cylinder powered BMWs, but the 4 cylinder cars can see a bit more vibration due to the higher inherent vibration tendencies with fewer cylinders.

    Why Use Competition Style Mounts?

    The difference in throttle response (from less "torque wrap up" in the driveline bushings) from these mounts compared to the OEM rubber is dramatic, and the feedback from customers has been almost 100% positive. Some users noticed an increase in perceived vibration more than others, normally due to lightened flywheel or other driveline changes. Shift feel is dramatically improved, and missed shifts from body-to-driveline misalignment are a thing of the past.



    Our original motor mount design was built around the wording of "alternate driveline mount" rules written for several SCCA racing classes. This had to do with a "percentage of metal content" requirement. We took the effort to make our mounts compliant to these rules when others did not, and various SCCA racers appreciated that. Vorshlag testers and employees installed both poly and Nylon mounts in our own BMWs, that we daily drove and raced for many years, often 6+ months before a product was released for production. We tested these mounts and abused them and improved them, long before they made it to end customers.


    Vorshlag cars testing E36/E46 competition motor mounts. Both saw street miles as well as competition in SCCA Auto-x and NASA Time Trial

    We have had very few issues over the years, but the most common issue is that the center stud could break, typically right at the top of the assembly. We traced most of those failures to installation issues or problems that could arise during transmission service. The normal clutch job on a BMW involves unbolting the transmission crossmember and lowering the driveline down at the rear, then unbolting the bellhousing bolts and removing the transmission, leaving the engine to sag on the mounts. With the OEM motor mounts you could do this, but with our more rigid bolt-thru design this would put extreme tilting stress on the stud. If the motor mount nuts were loosened before service there wasn't an issue. Another common mistake was massive over-torquing of the stud when used with the polyurethane bushing insert, which compresses as the top nut is tightened. This could cause the stud to stretch and even yield. We didn't see this with the Nylon insert, as that material is so rigid and stiff that it won't compress, so some users don't keep cranking down on the top nut and pre-loading the main stud.



    We have sold thousands of these mounts over the past seven years, with a very small failure rate. But of course everything made for a race car is a compromise. This design was a compromise to meet the SCCA rule wording. It is better at some things compared to the OEM mount/bushing, and worse at others. We made this motor mount to firm up the OEM hydraulic/rubber design, which it did very well, but it could add some NVH, and if installed improperly or abused during transmission service, the stud could be overstressed. We always wanted to use a little more metal in the design, and a shorter main stud, but the SCCA rules constraint made that impossible. Most of our customers understood this, and since this part was made for racing use, the potential drawbacks were within reason.

    Updated product entries:

    Good news is that for 2013 the SCCA changed the wording of the driveline and bushing rules, completely removing the metal percentage requirement and just giving it a "must weigh as much or more than stock" limit. This allowed us to improve the design and still remain legal for all of these classes that use this new rule wording - nicely done, SCCA. In spring 2013 we updated the design to add significantly more metal to the base assembly, which shortened the length of the stud and lengthened the center post. It also supports the bushing insert along more of its length, which is helpful as the motor mounts are canted at an angle in the engine bay and see some side loading.


    Vorshlag Nylon Competition Mounts installed on an E36 M3. Note that all OEM heat shields can be re-used

    The updated Vorshlag motor mount's aluminum center section is now 1.2" longer, which makes the entire assembly stronger. The new main stud is also shorter and should see less bending stress if the mount is loose, or when the motor is tilted on the axis of this stud, etc. Can it still break? Of course - somebody will always find a way to break anything. Care should still be taken with the top nut torquing and during transmission service. See our product entry page for installation tips with the polyurethane inserts.



    Again, the original design was constrained around a certain set of rules that many of our customers had to build around, so it was a compromise that required some more attention during service. That rule set has changed, and we made a design update to take advantage of this rule update. It is now "less compromised by rule compliance", and stronger than before.

    Easy To Upgrade


    Vorshlag E36/46/E92 M3 Competition Motor Mount Upgrade Kit, for existing owners of the 2006-2012 design

    Several racers have heard about the new design and asked for an upgrade path. We now offer the updated base + stud assembly as an upgrade kit for the previous generation Vorshlag mounts. All of our E36/46 motor mounts built from May 2013 onward use this updated base design.


    With the parts from the above link you can convert your Vorshlag Competition Motor Mounts from the 2006-12 design to the 2013 specification. This upgrade kit includes the pair of updated aluminum bases, all new hardware, and the upper and lower main studs plus the locating pin pre-installed. Swap in the existing bushing insert and upper motor mount plate and you're good to go.

    Thanks,
    Terry Fair - www.vorshlag.com
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev
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