Toward the end of my last track session for 2018 I noticed a significant change in exhaust tone. I thought the larger second position OEM cat had finally failed, but it turns out it was the first smaller cat ahead of it. If you see a break like this, you should also check your motor mounts. Chances are one or more of your mounts is broken or weak, causing excessive movement of the engine. This additional rocking of the engine finds the weakest point in the exhaust and causes either the flex joint or this joint to fail.
This turns out to also be the most common cause of emissions test failures for this car. The joint fails causing a leak and then the second O2 sensor throws a code. If you’re looking at a used car to buy, check out the area circled in red below:
MINI placed the electric power steering pump and steering rack very close to the header. If the pump ever over-heats it turns itself off. If this happens on the track (which it has to me) it can be very unsettling as the steering instantly becomes VERY heavy. So before installing the header, I decided to wrap it with DEI header wrap. This video shows how to do it.
Your MINI motor mounts will fail. It’s a matter of “when” not “if.” The stock rubber bushings age and harden over time especially if you track your car. The stock bushings were designed to reduce vibration not for performance.
We already replaced the top motor mount on this car, but ended up sticking with the stock mount since we were still daily driving the car at the time and the racing mount was just too harsh for the daily commute. Now that this is a dedicated track car, we’re going to replace the bushings with racing mounts as they wear out. The first one to go is the lower mount.
When it comes to replacing the stock mount you have a couple of options. You could just go with OEM which runs about $140 for the mount. Go aftermarket for $40-$60. And then just add a polyurethane insert for about $33. We decided to try the semi-solid mount from Torque Solution. Made of billet aluminum and 70 Durometer polyurethane. It should significantly reduce engine movement without transmitting too much engine vibration to the chassis. Installation is very simple and should take less than 30 minutes.
Safely jack the front of your car high enough that you can get a wrench on the mounting bolts. You don’t necessarily have to jack the engine, but we wanted to make sure there wasn’t any pressure on the mount when we unbolted the bracket from the engine.
First remove the center bolt of the large bushing with a 16mm socket, and then remove the other 16 mm bolt that runs through the bracket on the small end. Remove the four 13 mm bolts that hold the bracket to the oil pan.
Installation is the reverse of removal. Tighten the four 13 mm bolts to the oil pan and torque to 28 lb-ft. Hand tighten the two 16 mm bolts and lower the engine if you jacked it for removal before torquing to 78 lb-ft.
It’s been over seven years since I had John Behe tune the MINI, so I took it back to the Dyno at RPR Performance to see how it’s doing. This car has just bolt-on mods: 15% SC reduction pulley, JCW injectors, cold air intake, and exhaust. We’re currently running MSD wires and coil pack, with Brisk Racing Plugs that are one-step cooler than stock. The intercooler diverter has been modified to try to improve charge cooling. And that’s it.
I’ve had the car dyno’d a few times. When I purchased it in 2011 when it was still stock with 48k miles. After the tune I got when the SC reduction pulley was installed a few months later at about 55k miles, and then in October 2018 just to see how it was holding up now that I’m approaching 100k miles.
The data is interesting for a couple of reasons. There is a drop in HP above 6000 RPM and it starts to run rich until about 6600 RPM then seems to come back to the expected values. Don’t know if there was something funky with this pull, or if perhaps there’s an air leak on high boost.
I plotted the data against previous runs. I had to extrapolate some values since I only had data on 250 RPM intervals, but it’s generally good. The comparison is stock; MTH tune (on my prior MINI); the original tune on this car; and then today. Overall it’s holding up pretty well.
I like to use the MTH comparison for people who are thinking about a canned tune. MTH isn’t around any more, but this was an inexpensive tune you could get over the internet. You just told the tuner the mods you had and they sent you back a tune. Pretty good bank for the buck, but you see the real gains in a custom tune when you look at low end torque.
It’s a little hard to read in the chart, but the orange lines are the most recent dyno results (solid line is HP; dashed line is torque). Yellow is the custom tune. Green is stock and blue is MTH.
During the off-season I’ll go over the engine and look for the leak. (I can hear it at high RPM.) It’s not throwing any codes so it’s either ahead of the MAP sensor, or after the Cat (or both). It’s about time to replace vacuum hoses anyway.
One more BMWCCA DE, one more soggy weekend. All three events this year were wet at some point this year. The Shenandoah circuit is usually a very fun circuit, but I got caught out on the wrong tires. My worn Falkens were no match for the amount of water on the track and became rock hard once the temperature dropped. Still a bad day at the track is better than most days at work.