MINI revisits the Dyno

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.