Engine Mounts Filled With Polyurethane

Not many solutions seem to be out there for the RX-8 in terms of alternative engine mounts. The original 2004 to 2005 version was flawed in design as they didn't last long, forcing owners to replace them somewhere between every 30,000 to 50,000 miles. In 2006, the engine mounts were revised to be much more efficient and longer lasting.
This DIY goes over how to take your engine mounts and turn them into some very nice and stiff engine mounts that you won't have to ever replace. We used Dave's engine mounts on his RX-8, which is the 2004 version, not the upgraded version. Be sure to check out this thread on RX-8 club with a nice writeup from Team RX8.

Tools & Materials

• Wooden Ruler
• Paint Thinner
• Drill and a 1/4" - 3/8" diameter drill bit
• Sharp Knife (that you don't care about getting fluid on)
• Oil Catcher
• Clothing to wear that you don't care about staining permanently
• Blow Dryer
• Canned Air
• Polyurethane base and activator (I purchased mine from McMaster-Carr and it's item #8644k11)

Process

A couple of quick notes. This write-up assumes you already have the engine mounts removed from the car. Be sure to double check them for any cracks or leaks, because doing this to a damaged mount is not advisable. Also, the polyurethane takes 48 hours to cure, so be sure to do this when you won't need to use your car for a few days.

1. Start by turning the mount upside down and removing the top rubber cover of the mount with the knife
2. After you have removed the cover, be sure to empty out as much of the fluid as possible. The fluid smells and will stain your clothes pretty good, so be careful!
3. At the center hole, you will notice a rubbery layer. Carefully cut that out with the knife, trying not to puncture all the way down and through the entire mount
4. Skip this step if you have 2004-2005 engine mounts - The upgraded engine mounts have no circular opening, so you will need to drill in the center carefully and make your own circular opening in the center
5. Once you have cut out and removed the rubber layer, you should see a honeycomb-like design inside the mount. Those pouches are what will be filled with polyurethane
6. Now drill 6-8 holes around the middle hole in the engine mount with your drill. You will feel as you are drilling down, the drill going through 3 layers. The moment you feel the 3rd layer, pull back so you do not accidentally drill through the mount.
7. Once you have made your holes, check them to be sure you drilled all the way through the hard brown layers and down to the black rubber surface. Use the canned air to clean out any excess shavings left by the drill
8. Now fill the mount with your paint thinner and clean it out as much as possible. You can use water as a first pass, or go straight to the paint thinner, whatever you feel comfortable with
9. Once it looks like all of the fluid has been cleaned out, use your blow dryer, on high setting, to dry out the inside of the mount. I held my mount upside down for about 5 minutes with the blow dryer pressed against it
10. Once the mount is completely dry inside, prop both mounts on a flat surface, with support to ensure they don't accidentally get tipped over. Remember, these mounts will be sitting wherever you place them, for 48 hours
11. Take your polyurethane base can and mix in ALL of the activator for 5 minutes. BE SURE TO DO THIS OUTSIDE as the warning says. I also thought their wooden stick was too small to stir, so I liked using a long wooden ruler instead
12. Once you have mixed everything, begin by very slowly pouring it into the center of the engine mount. Pace the pouring slowly so that everything can settle nicely and the air can escape. Switch from mount to mount if need be as well
13. After some time, you'll start to notice the polyurethane rise up from the center and the side holes. Keep filling slowly until you have a nice, flat, even surface at the top of the mount
14. Once you're done pouring, you can take the ruler and run it slowly across the top of the mount so that you can ensure it's flat. Be sure to clean up any mess around the mount because it is bound to happen!
15. After clean up, let it sit for 48 hours before placing back into your car!

Outcome

I noticed a huge difference right away when I drove my car, but then again, my passenger engine mount was collapsed previously. The throttle response was greatly increased to the point that it feels like the car is drive-by-cable. Less slop in the shifter as well I noticed, but definitely an interesting feeling being able to feel the power go to the rear tires more. Overall, it feels as though I had gotten a brand new engine put into my car, so I'm overly pleased with the results. I highly recommend this to everyone. It's very very affordable, a fun project, and easy to do with some patience! With the end result being that you will then have engine mounts that will never collapse, how could you say no? Happy Motoring!

STX VS. BSP & RMC 2nd Points Event

Today was the 2nd points event for Renegade Miata! Dave is looking to get that 1st place jacket at the end of the year from SCCA just as bad as I am, so he decided to come out for some extra seat time. We decided to switch it up a little bit this event however. Thanks to Rob (chairman of the Renegade Miata Club), he allowed Dave and I to do a test in the morning. We were going to switch cars and compare the differences in our two cars with their current build, and how well we could adapt to them. This would be a great opportunity to focus on being smooth on the course while being in another RX-8 that is setup differently. In the afternoon, we then would switch back to our own cars and see if we could beat our times in the morning! This would really allow us to critique our own cars, as well as each others and consider making changes if need be. This is the first, in hopefully many more to come, "BSP VS. STX Battle"!

Photo by Ed Savage - NoWin Photography

I decided that I will be running the rest of Renegade Miata on street tires so that my Hoosiers can stay as top notch as possible, (and to be fair for this test/battle). There are not too many differences between Dave's RX-8 and my own RX-8. The biggest differences would have to be that I have the BHR midpipe, flywheel, 4.777 rear end, very different spring rates (730 lb. and 450 lb. versus 503 lb. and 337 lb.), and 255/35 Dunlop Star Specs as opposed to 265/35 Yokohama Advan AD-08. The course was very tricky and had a very interesting rhythm to it, emphasizing heavily on being consistently smooth.

Photo by Ed Savage - NoWin Photography

The battle in the morning was interesting to say the least, where as I was enjoying Dave's car and putting down quick times, making only minor adjustments, and Dave was fighting with my car to keep it stable and put the power down when exiting the turns. I helped Dave by adjusting the shocks and playing with tire pressures, getting it down to full soft in the rear, 12 clicks from stiff in the front, and 29 PSI in the front with 30 PSI in the rear. A very different setup compared to when I run R compounds. Next event I think I may actually benefit with the rear swaybar removed, so I will try that out and see how it goes.

My fastest run in the morning was a 1'21 clean, with Dave getting a 1'19 very dirty, and then a 1'22 as his fastest. In the afternoon when we switched back, I was much more at home, and so was Dave. I was able to get down to a 1'20 clean, but with a fastest of 1'19 dirty. Dave was right behind me with a 1'20. I think we both could've gone faster if we had more practice in our own cars in the morning, but I was happy with the overall test and am looking forward to the next SCCA NER race. As always, results for Renegade Miata are located here. Thanks Dave for the test, I had a lot of fun and am looking forward to our next swap or comparison battle. Below are our fastest runs in the morning and afternoon. Until then, I will be filling my motor mounts with polyurethane because it felt AMAZING in Dave's RX-8, so stay tuned!