So I noticed that I am getting some blow by out the exhausts only when I am really standing on the pedal. It is leaving little flecks of oil on the barn doors due to the turbulent air circulating behind the car at speed. The catch can should solve this problem, but in the mean time I ordered a hand full of AirTabs and installed them last night. It took a little while to measure off the placement, blue tape the measured areas, prep the surface, etc before attaching them.

If you are not familiar with these, they are basically air diffusers used for a number of commercial and consumer applications to disrupt the air flow and streamline the air leaving the back of the trailer, car, truck, RV and aircraft just to name a few things. It's supposed to improve MPG but the way I drive I could care less about that aspect.

So I cleaned the rear of the car last night when I got done. Got up this AM and drove in to the office at 4:30AM. Not a lot of traffic at that hour so I was able to romp on it many times over my 15 mile drive, as well as rapid lane changes. When I got to work I was surprised to find not a single fleck of oil on the barn doors, back window, etc.

It maybe be too early to make this claim, but I will say it anyhow. When you are dealing with small engines, and light cars, it doesn't take much to make a noticeable difference when it comes to acceleration, braking, MPG, handling, etc. The slightest change can make a noteworthy difference. At slower speeds nothing felt different, but at 45+ the rear end didn't feel as frisky as it did before. Not sure how to describe it exactly. This is on a 2011 JCW R55 that's had several mods done above being a factory JCW car. She drives great and is plenty quick. Even with the medium compound tires, she fights for traction all the way through second gear. But the rear end has always felt a little loose. Kind of akin to having worn bushing etc. I have inspected every aspect of the rear suspension components and nothing is worn or out of line.

Today the rear end felt tighter and more inline with the car as I weaved in and out of empty lanes in the wee early hours. I don't have access to a wind tunnel to visibly see what's going on with the air flow now. I have ran traditional diffusers under the back rear of many track cars, and big GT style wings on the rear of some of those same cars so I know what one feels like with proper air flow at the rear of the car.

If the air flow is stuck behind the car, and blowing up the back, hence the flecks of blow by oil, then this can cause the rear end to be light and loose even at moderate speeds. Again, I point out the over all weight of only 2800 pounds. So if the airflow over the roof is now flowing away from the vehicle and not just circulating around and back towards the car, then this would result in more downforce and wouldn't create lightening of the rear with more turbulent discharge of the air flow at the rear of the car. I will know more as I drive it with the AirTabs installed. AirTabs are very inexpensive (less than $3 per unit), and if my experience is accurate then this should be beneficial to many of you out there dealing with possibly lighter rear ends (you most likely don't even know until the airflow is directed properly) and blow by on rear body panels of your Mini. I will post more of my findings here on this thread as well as on my Instagram page (black_label_tools) as time passes and I can conduct more tests. This is just my first instinct and experience driving with them for the first time today. Have a great weekend and Mini on!

 

Nice. I can see those being effective in reducing the air hole behind the car. You might also be able to help airflow under the car by adding some under the leading edge of the front bumper.

 

Been thinking of doing this since my first R55 - thank you for posting this! My current R55/JCW has the dealer installed JCW rear wing and I wonder if you have any thoughts on their effectiveness if I mount AirTabs on the wing (top, bottom, both?)? Seems to me that they would offer some benefits. However, the wing without AirTabs should already offer some of the same benefits. My JCW has 75,000 miles, with two oil catch cans. I don't get any blow by on the barn doors, and the dirt accumulation is not as bad as my previous R55 S, which did not have a wing. My non-scientific estimation is that the dirt accumulation on my JCW with the dealer installed wing is about 20% less than my R55 S without a wing.

Also, I've considered mounting AirTabs below the rear bumper. My approach would be to add a flat panel under the spare tire area to prevent airflow into the rear bumper cavity, and extend the flat panel slightly behind the car, with AirTabs mounted on the bottom side.

As njaremka mentioned, I've also considered mounting some AirTabs up front. I've thought about mounting them on the trailing edge of my GP2 belly pan and on the trailing edge of my JCW underbody panels - just ahead of the rear suspension.

Please keep us posted on your findings! Any thoughts would be welcome. Again, thanks for sharing!