The little 1.6-liter engine in the NA6 Miata moves too much. This engine movement, combined with soft factory differential bushings, contributes to a lot of drivetrain movement.
During race conditions, drivetrain movement moves the shifter, making miss shifts a lot easier. At best, the 2-3 upshift lands you in 5th and outside of the power band. At worst, the 5-4 downshift grabs 2nd gear, and the engine over-revs. Causing potential damage in what is affectionately termed a ‘money shift’.
Needless to say, neither of these behaviors is desirable in a race car.
AWR Engine Mounts
These mounts contain a polyurethane bushing in 4 hardnesses. Measured in durometer hardness, the mounts scale from extra soft to hard.
- Extra Soft (62)
- Soft (70)
- Medium (88)
- Hard (95)
In my application, a racecar, I chose the 88 durometer polyurethane bushing to minimize engine movement as much as possible without going to an effectively solid mount at the 95 durometer hardness. Also note that the extra soft is stiffer than stock and will transmit more vibration into the chassis of a street car.
Tools Required
- 3/8″ ratchet
- 3/8″ extension
- 14mm, 17mm, amd 19mm socket
- 19mm wrench
- hydraulic jack
- jack stands
Process
Step 1: Park the car on level ground and place the car on jack stands.
Step 2: Place the hydraulic jack under the engine pan and raise the jack to where it is just touching the pan. The jack will be used to stabilize and manipulate the engine once the factory engine mounts are loosened and removed.
Note: You do not want an unprotected hydraulic jack placing pressure directly on the metal oil pan. I used a piece of wood I had laying around to sandwich between the jack and the pan. This also spreads the load across the oil pan.
Step 3: Loosen the 14mm nuts holding the engine mounts to the front subframe. An impact wrench and extension will make quick work of overtightened mounts.
Step 4: Remove the 3 x 17mm bolts that hold the upper engine mount brackets to the engine block. The bolts will be reused, the brackets will not.
Step 5: At this point, all bolts and nuts that connect the engine mounts to the subframe and the engine block are removed. Raise the engine a few inches and snake the factory engine mounts out of the engine bay.
Step 6: The center bolt on the AWR engine mounts should remain loose until new mounts are installed to the block and the weight of the engine is resting on them. However, it can take a little finesse to get everything to line up during assembly. I recommend loosely installing the 17mm bolt that is towards the rear of engine block on both of the new mounts. Then slowly lower the engine to line up the lower stud with the subframe. By loosely installing only one of the 17mm bolts, you will have a little more play to line up the lower stud. Once everything is lined up and the engine is partially lowered, install and tighten all of the 17mm bolts into the engine block.
Step 7: Lower the engine completely and tighten the new 14mm nut with washer to the subframe.
Step 8: With the block side and subframe side fully tightened and the engines weight fully on the subframe, tighten the 19mm engine mount bushing bolt.
Impressions
I won’t officially test the AWR engine mounts until my next race at NOLA Motorsports Park. However, I can no longer wiggle the engine side to side a quarter inch as I could with the factory mounts. I will report back to confirm, but these mounts will drastically reduce driveline movement and properly rattle my teeth while racing.
Weights and Measures
One final note. As I am focusing on lightness before power, I will include weights where appropriate in these write-ups. I knew it would be small, but the AWR engine mounts came in 1lb 4.4ounces (1.275 lbs.) heavier each. So, I have a net gain of 2.5 lbs. after installing these. Not the direction I like to move but the tradeoff will be well worth the weight gain.
