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Crossing the Line: MINI gets a Rollbar
This past weekend brought another arctic blast to the Mid-Atlantic region and the first driving event of the year. We learned a couple of interesting lessons driving in sub-freezing temperatures on the track:
- According to the National Weather Service, the wind-chill of 7 degrees F at 109 MPH (the max speed of their calculator) is -29.
- Seat heaters are wonderful things and you don’t want to stick your hand outside if you don’t have to.
- Even with road surface temperatures near 20 degrees, summer tires will get warm enough to grip (they aren’t supposed to work under 40 degrees) and will actually reach temperatures near 100 degrees.
- The Roots-type Supercharger really likes the higher density air that comes with extremely low temperatures.
The biggest disadvantage to having a driving event in this type of weather is the preparation that’s always required for the first event of the year, especially if you have a garage with questionable heat. During the few days of above freezing temperatures, we did manage to install new brake calipers and rotors; flush the brake system; reinstall the cold air intake and prep the interior for the roll-bar install.
The big news for this year is the installation of the SneedSpeed roll-bar. Finally crossing the line from street-car to dedicated track-car, the rear seats have come out for the last time and the roll-bar was welded in.
The finished job looks great. We’ll have to do a better job of fitting the required padding once things warm up again and the padding becomes more pliable, but it was good enough for this weekend.
The interior trim required only a small amount if trimming on the bottom edge where the side meets the roll hoop where it welds to the chassis. Removing the side pockets from trim panels reduced the total amount of trimming that was required. All that is left now is to re-carpet the plywood panel that sits where the seat-bottoms were.
MINI Suspension Compliance
Passengers in the GeorgeCo MINI often complain that they are just but one pothole away from losing a filling. With the stiffer lowering springs and beefy swaybars fore and aft, the effective spring rate was probably in the neighborhood of 450 lbs. By way of comparison, the stock spring rate is somewhere around 200-220 lbs. A stiffly sprung car is great for a smooth racetrack, but can be torture on the street. Having spent a few days at the track in the Porsche with a completely stock suspension, I have come to the conclusion that the MINI doesn’t need to be so stiff. (Remember the early posts about this car when I said I wasn’t going to turn it into a track car. Well, wrong…)
After some additional critical reflection I thought I could achieve 3 objectives by designing a suspension with more compliance: 1.) Improve the ride as measured by the right-seat passenger dyno; 2.) Keep the modifications that correct the glaring deficiencies of the geometry (under-steer and lack of front camber); and 3.) Be cost-neutral. It turns out, there was an unexpected bonus as well: reducing un-sprung weight.
First a recap. Starting with a Stock 2006 Cooper S:
Make the following modifications: Bavarian Autosport Performance Lowering Springs (2″+ drop); Bilstein Sport Struts/Shocks; Eibach adjustable camber plates; JCW Sport Brake Kit; Madness Lower Brace; Powerflex Control Arm Bushings; H&R 27mm Front Swaybar; Alta adjustable endlinks front and rear; Alta 22mm 3-way adjustable swaybar; and HR Sport Camber Arms. The result:
Slammed, stiff, and neutral. No hint of under-steer. Even front tire wear. About 3.5 inches of ground clearance (problematic). Harsh under rapid compression of suspension (pothole). Wonderful at the track. Not so much fun on the freeway. All of the modifications except the front swaybar are quite conventional. The stiff front swaybar really transforms the way the car turns-in under heavy braking, but at a cost. If the front end isn’t loaded, steering became somewhat vague. Definitely not to everyone’s taste.
I decided to keep the bits I liked, sell off the rest, and use the money to buy anything that I didn’t reuse from stock. Gone were the BavAuto springs, replaced by H&R Sport Springs. I Swapped the front swaybar back for stock and got a screaming deal on a 19mm rear bar to better balance the front. I Sold the adjustable endlinks since they aren’t needed with the H&R Springs (the drop is only 1.25 to 1.5 inches so the links don’t really need to be shortened.) Gone was the Madness bar. JCW brakes were replaced by stock along with new stock rotors. I kept the Powerflex bushings and Bilstein struts, but swapped the Eibach adjustable plates for Ireland Engineering fixed camber plates. What I lost in adjustability I more than made up for in comfort. I broke even on cost and shed 26.5 lbs in weight (21 lbs unsprung) and all but 1.5 from the front.) Ride height is somewhere between the two extremes:
So if you superimpose them over each other, you get:
More Comp Tire Goodness
It’s been a busy year since we first bought this car. Our goal was to find a low mileage ’06 Cooper S that could eventually be modified for club racing. Keeping in mind that the cost difference between an R53 Cooper S and JCW is about $5,000, we wanted to make this car better than a JCW model, without completely sacrificing creature comfort as a daily driver until we were ready to gut the interior and install a cage. I think we’ve brought it right to that edge: It’s stiff, but not jarring. And it’s fast.
Given that the majority of R53 Cooper S cars were sold with sunroofs, finding the right car proved harder than you would have thought. We found a 45,000 mile car, with heated Punch Leather seats, a factory limited slip differential, and fog-lights — no other options or packages. This August we replaced the clutch, ball joints and rear main seal just to baseline the car, but it really was in terrific condition. The boxes above contain the last phase of our initial sorting: getting power to the road through light-weight wheels and grippy tires, in this case Nitto NT-01 R-comps which we’ll scrub-in at a test-and-tune autocross event in Frederick and then we should be ready for the track coming up in two weeks.
To recap, here’s what we’ve done to date:
Handling — We added an H&R 27 mm front roll-bar with Alta adjustable end-links and Powerflex control arm bushings. Previously we installed an Alta 22mm adjustable rear sway-bar (now set to the stiffest setting to compensate for the bigger front bar) and adjustable end links. Suspension consists of Bilstein Sport shocks and struts over Bavarian Autosport Performance Springs. We have Powerflex shock bushings in the rear and Eibach adjustable camber plates in the front. Suspension settings are 1.7 degrees negative camber in the front, 1.5 degrees negative camber in the back. (That’s the most negative camber we can get in the front without binding the springs.) Front toe is neutral, slight toe-in for the rear to increase straight-line stability. In the rear we also have H-Sport adjustable control arms to compensate for lowering and to beef-up what’s normally a weak link in the MINI stock suspension. To increase chassis stiffness, we have a strut-tower brace in the rear, Madness Lower Stress Bar in the front, and MINI OEM Cabrio cross braces. To improve braking, we added JCW brakes up front, stainless steel brake lines all around, and brass bushings to the rear brakes.
Power — MINIs have the aerodynamics of bricks so power improvement isn’t ever about top-end as much as it is about mid-range torque. We have a Madness 15 percent reduction pulley, Screamin Demon Coil, MSD plug wires and NGK Iridium plugs. On the intake side, we are using an ALTA intake and intake hose along with an ALTA intercooler diverter. On the exhaust side, we’re using a Scorpion stainless steel free-flow exhaust. The Scorpion exhaust is lighter weight than stock and has a nice deep tone without droning. Behe performance provided the custom tune to take advantage of all the changes. Currently, this car dynos at about 198 whp. We could increase it to get above 200 by increasing the rev limit setting, but frankly we’re more interested in power from 4500 to 6000 RPMs than we are watching pieces blow through the cylinder walls at 7200 RPM. We want this lump to last 200K miles or longer.
Information Management — We’ve brought over the FES-Auto shift-light from our previous R53 and added a new telemetry system this year. We’ve outfitted the car with a PLX devices wireless network adapter that feeds telemetry data to an iPhone. Now we can log data as well as add telemetry data to in-car videos.
Cost total: Excluding the clutch and ball-joints which were just routine maintenance items, we’re just $300 shy of our $5K budget. That’s pretty good considering all of the changes we’ve made so far.
More Control
I’ve been taking advantage of the unusually mild November weather to catch up on some maintenance issues on my cars. It started when I noticed a nasty screech sound from the MINI clutch on the way home from work one day. It had been a while since the MINI (now with over 135K miles/over 5K on the track) had been thoroughly checked out. Sure enough the clutch is slipping.
Once you know you have to drop the engine to replace the clutch, you start to think of all of the other things you might as well do while it’s all apart. I noticed steering wasn’t as precise as before (2nd set of control arm bushing shot); and I haven’t yet replaced the belt tensioner (3rd belt due to be replaced.) I started to source parts, and then realized I’d have to drive the Stealth to work while the MINI is in the shop. I ended up getting a Spec Stage II clutch and lightened aluminum flywheel along with some Powerflex bushings.
The Stealth E30 burned through a front wheel bearing on my last track day and also showed signs of control arm ball joint failure (I hate when that happens.) New bearings, new wheel studs, new control arms, new control arm bushings, and an alignment later, the Stealth is back on the road. I was able to do the control arm replacement and bushings, but the rest I had to take to York Auto.
I’m trying something a bit different with this set of control arm bushings. I used offset bushings from an E36 M3. The offset location ads a bit more track, camber and caster to the geometry. With the current setup of Bavauto springs and Bilstein shocks, I’m getting 2.5 degrees negative camber in the front (without adjustable camber plates) and 2.6 negative degrees in the back.
Imagine a World without Wumps
Tim installed the new Bimmerworld driveline today. What a difference. Imagine having a driveline that actually flexes instead of just eating guibos and center bearings. Power comes on smoothly without the background fear that it’s all going to self destruct. It also helps that he cleaned out the throttle body. With that task, phase two of this project draws to a close. Phase one was just about getting it registered and titled. Phase two was getting it baselined and ready for the track. Phase three is about making it faster and improving handling. Phase four, if I ever get there, is about completing the build-out for Spec E-30. But for now, it’s about making a better STX autocrosser.
