Lapping Jefferson Extension

I had the MINI at Summit Point this past weekend on the extended Jefferson circuit and it ran great. I really like the new Bilsteins. Very predictable weight transfer, good grip, and nice ride-height. Currently riding about 40mm lower than stock in the back and 50mm lower than stock in the front. Could go another 10mm lower but don’t see the need currently.  (Interestingly, the current height is 20mm lower than H&R Sport Springs on Konis.) The car isn’t slammed and the tires aren’t rubbing, but it is fairly low. I did have to not use the 5mm spacers I normally run on the street to avoid rubbing the rear arches (the wheels are 17 x7 with offset 37.)

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Here’s a lap I filmed behind a student.

New Wheel Studs

I finally got a couple of days this past week where the temperature in the garage was above 45 degrees so I started to prep the MINI for the upcoming track season. No major changes are planned this year, just routine maintenance items. First up is to inspect the brake calipers and change the wheel studs. For the brakes, I’m checking the condition of the brake lines, cleaning the calipers and carriers, inspecting the piston dust boots, and torquing all of the bolts to spec. Track pads will come later. [And since someone will ask, the rotors at the top of the post are not cracked. That’s just discoloration from the brake pads contacting the rotor when the parking brake is engaged.]

Because my car is outside most of the time, I like to replace the wheel studs every other year. This has been an especially harsh winter so they are really very corroded. The process is not difficult, but getting good leverage in a tiny garage without a lift can be a challenge. Here’s the method that works for me.

New Wheel Studs

Remove the caliper, carrier, and rotor. Remember support the caliper by something other than just the brake-line (like a hanger or box.) If you’re removing old wheel studs, you’re going to need some leverage to overcome the sheer force needed to get them moving. Wheel studs don’t need to be tightened to high torque levels, but by using Loctite, they can be a pain to remove. I find that I can usually remove them using the double-nut method if I heat the hub first with a torch. You don’t need to get it red hot, but if you heat the area around the stud first, then block the hub from spinning, you can usually get the stud to start moving with a quick hammer blow on the wrench against the top nut. (If I had a lift and was working at shoulder height I might even get it to move just by pulling on it, but I’m working on jack-stands and sitting on the floor.) There are a couple of ways to approach the double-nut job. The right way is to thread the first nut upside down, then put a spacer washer on the stud, and thread the top nut the right way. If you plan to use these nuts on your wheels, this method will protect the cones. If you’re using nuts you plan to get rid of (like me), just thread them together. Put a little red Loctite on each stud and torque 16-20 ft lbs (using double nut method again.)

I’m using Apex Studs and they put together a little video explaining the process.

DAS Sport Rollbar Install DIY Porsche 996

Before we started carrying the Agency Power Rollbar for Porsche 996/997, I used to have a DAS Sport Rollbar in my car. Here are some tips for installing it in a 996/997 Coupe. The instructions published on the DAS Sport Website are pretty straight forward and with practice, the rollbar can be installed in about 45 minutes by yourself, though it’s always easier with a helper.

To begin, make sure you have enough room to maneuver with both doors wide open. You’ll need at least six feet free to maneuver on the passenger side. You don’t have to remove both seats, but it certainly is easier if you do, especially with fixed back seats. At a minimum, remove the passenger seat completely and remove the seat-bolts from the driver’s seat and move it as far forward as possible. If you car has seat-mounted airbags, as long as you do not turn the key with the airbags disconnected, you don’t have to worry about resetting the airbag warning light so make sure you don’t have to move the car once you start to work on this project. You will also be removing the carpet covering the ECU and strut mounts behind the rear seats. Consider if you want to carpet it or modify your current carpeting before you begin. It’s very difficult to try to put carpet back there once the bar is installed. You should also decide if you want to remove the rear seats or just leave them folded. You save a little weight by removing them, but with them folded you actually have more practical storage space in the back as you can use the folded seat as a shelf and stow small items on the seat below relatively out-of-sight from outside of the car. Using heavy beach towels, cover the center console, door plates and seat backs. The bar is very cumbersome to move around and you do not want to scratch your interior.

Carpet

Start by preparing to remove the seat-belt mounting bolts in the rear foot-well. Take time to note or photograph the way the seat-belt fits, especially the half twist that is necessary to get it to line up correctly. Check that you have the correct foot plate for each side and install the eye-bolts but do not tighten them. You will need to finish installing and tightening the upper bolts of the rollbar before tightening the eye-bolts. My carpet was cut — it is not required for this to fit properly and not recommended unless you plan to remove your carpet soon and don’t want to have to remove the rollbar.

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Remove the six nuts from the rear strut mounts. Note the angle of the mounting brackets on the rear section and turn it upside down. Carefully feed it into the car and rest it in the rear foot-well. Have someone help you flip it on to the rear strut mounting bolts. You will have to work it into position around the seatback stops and trim. Get all six openings into position and loosely tighten only the rear nuts to ensure it does not fall forward. Loosely tighten the remaining four nuts as well.

Installed

Orient the main rollbar as it will fit inside the car. Working from the passenger side, tip it so the bar is to the back and the foot is toward the front of the car, and work it in from the passenger side and around/over the driver’s seat before standing it up in the rear foot-well. It is cumbersome to move so consider wrapping the ends in shop towels to help prevent damaging your interior. Work the connectors to the rear section first and feed the bolts from inside to outside and tighten loosely. Put the foot into the driver’s side base and fit the bolt through from inside to outside. You will find one side will line up perfectly and the other will require some encouragement — this is normal. Encourage the other side to fit with a small rubber hammer and/or a very long flat-nose screw driver and fit the second bolt. Tighten both lower bolts loosely. If everything is linedPadding up, tighten from rear to front, starting with the rear strut mounts and torque to spec. The last bolts to tighten will be the eye-bolts. Use a screw driver and a vice-grip to turn them, but do not over tighten.

Consider using bar padding on the main hoop starting at door sill height. Check your view with the rearview mirror before you buy padding. You may want to get the mini padding type that won’t extend down so far into your field of view. You may have to remove the cover on the seat-belt height adjuster slider on the B pillar if you still use the stock belts.

MINI Brake Duct DIY

For the most part, stock MINI brakes and even the beefier JCW calipers do a decent job of dissipating heat at the track. I generally advise students to run a higher temperature fluid and to get some better brake pads like Hawk HP Plus or Carbotech XP-10 and they should be good for most 20-25 minute HPDE sessions. But for those days when you want to run longer or the ambient temperature is already approaching 100 degrees, you may need some additional cooling. That’s when this DIY will pay off.

The basic idea is pretty simple: The air in front of the bumper is a high pressure area. The area behind the wheel in the wheel well is a low pressure area. Create a path between the two and air will flow through and aid cooling. It won’t be as dramatic as dedicated ducting pointed directly at the hub, but it also isn’t as troublesome for the 99 percent of the time that your aren’t at the track. Expect to spend $10 to $75 and a couple of hours of your time. You’ll need a three inch hole saw, some zip-ties, and some tubing. You’ll loose the use of your foglights (if you have them) but you can put them back in the winter.

Duct opening

You might have luck just holding the tubing behind the bumper cover with compression, but I ended up fashioning a make-shift duct out of an old set of fog light covers (MINI part numbers 51711481435 and 51711481436) which are about $19 each. Just cut the center out and add a screen to keep out debris. Attach about a foot of tubing to the other end and pick where you want to cut the wheel liner.

Duct in wheel well

If you’re trying to stay really low tech, use dryer vent tubing and gutter guard, otherwise invest in a three foot section of silicon brake duct tubing and some wire mesh (I’ve tried both, silicon tubing is easier to work with.)

Duct tied off

Attach the tubing to the wheel liner with zip ties. Wire mesh comes in handy here too. when you’re all finished, you can hardly tell anything has changed. Good for a 50 degree drop in caliper temps at Summit Point in August.

Finished duct

Coilover Suspension & the Tyranny of Choice

“Logic suggests that having options allows people to select precisely what makes them happiest. But, as studies show, abundant choice often makes for misery.” Psychologist Barry Schwartz didn’t know it at the time, but he was talking about Coilover Suspensions when he wrote those words in Scientific American back in 2004. Like Robbin Williams shopping for Coffee in the movie “Moscow on the Hudson”, the choice of coilovers can be overwhelming. With height adjustable, 2-way, 3-way, remote reservoir, club-sport, electronic dampening control — the choices are daunting. If you have no prior experience with coilovers, this post offers a framework for better decision-making before you invest in an expensive coilover system that you don’t like.

Maybe it’s not the car. Maybe it’s you. Unless and until you can clearly articulate what you don’t like about your old suspension and the characteristics you seek in the new one, just purchasing a set of coilovers isn’t the answer.

How did you end up with your current suspension? If you’re driving a sporty German car (and if you’ve found this blog, you probably are), then your suspension went through a development process more or less something like this: Given your car’s intended purpose (sporty weekend get-away; grocery getter; executive tourer, etc.) intelligent chassis and suspension engineers tuned it for German roads. Average in-town speeds (30 MPH) are generally lower than the U.S., and highway (autobahn) speeds are much higher. The car has to be able to stop from its top speed without brake fade repeatedly; it must pass the moose-test and most importantly for our analysis, was designed assuming that the roads are smooth and generally free of potholes. In other words, their roads are not American roads. So to prepare that same car for the American market, they did three things: They raised the ride-height; they assumed the passenger load is heaver; and they softened the suspension to increase compliance on our bad roads. (OK, I made up the second part, but I suspect it to be true none-the-less.)

When you come to a fork in the road, take it. To figure out where you’re going, start your analysis by describing what you like about your current set-up on the highway. Does it pass the “spouse test” (no complaints from the significant other on long trips)? Do you have confidence for making sudden, unexpected high-speed maneuvers (on the road, not with the spouse)? Does it absorb the seams and road irregularities? How about when only one wheel or one side of the car hits a pothole, does it absorb the impact or is it jarring? Does your car have the “sport” suspension from the manufacturer? Is it the U.S. specific suspension (as opposed to Euro or “Rest of the World” [ROW] suspension in Porsche terms)? How does it perform at the track? How does it compare to other similar cars that have modified the stock suspension? What did you like/dislike about other people’s choices?

Let’s assume the answers to the questions above are: U.S. “Sport” suspension, good on the bumps, and passes the spouse test. (Typical for most BMW/MINI sport suspension owners and Porsche drivers with the M030 sport suspension.) Will you be happy with just buying lowering springs and reusing the stock struts? The answer is (generally) no, not in the long term. By not changing the shock to match the shorter spring, you will loose compliance. You will find yourself more often on the bump-stops, and generally with a harsher ride. Many sporty drivers say they can live with the trade-off. Most spouses do not. This is usually the path that got someone thinking about coilovers in the first place: they tried performance lowering (sport) springs, and now they think they need coilovers.

Remember the speed assumptions mentioned earlier? They’re critical to suspension design. High-frequency motion occurs as your suspension reacts to irregularities on the road surface such as bumps, pot-holes, seams, etc. The car is basically in a static state on the springs, but the individual wheels need to react to the road quickly. That bump and recovery is a high-frequency event. As the suspension takes a set for a corner (weigh transfers forward under braking, then to the outside under cornering); that’s a low-frequency event. The spring and shock work together to get the right amount of body roll for good weight transfer, but not too much lean causing a loss of control. The delta between the valving that is required to deal with those two types of events is what gives each shock its unique characteristics.

Now go back to the speed and road surface assumptions above. If we’re assuming high-speed, smooth surface autobahn driving, for a given weight of car, we’ll choose a stiffer spring and shock combination. Because of the speeds involved, the weight transfer rate will be higher than for the same car in the U.S., but because the road surface is assumed to be better, you don’t have to worry about the effect of road surface irregularities as much under compression. Since in-town speed limits are also lower, when that same stiffer suspension encounters a road-seam or bump at a speed lower than in the U.S., it doesn’t transmit as much harshness to the cabin. The overall result is a lower, stiffer suspension. Many drivers seeking a more performance oriented ride are satisfied by merely finding the European (or ROW) version of their current suspension and making the swap (we did exactly that on our Porsche 996). It has the benefits that come from purchasing OEM parts as you don’t have to worry if it will all work together as a system, and it generally doesn’t hurt resale value when you go to sell the car. For many though, that’s still not enough change for track duty.

Why do you think you want a coilover suspension anyway? Do you want to be able to adjust the height; adjust compression; adjust rebound; or adjust all three things? Do you want to run springs with a smaller diameter for other reasons such as increasing negative camber in the front? The majority of coilover buyers buy them to be able to adjust the height of their cars. (On some new cars like the new BMW M3/M4, consider getting Height Adjustment Spring Systems to get height adjustability with stock shocks/struts.) Most customers who are interested in coilovers tell us three things: For the most part, they’re satisfied with the ride quality of their current suspension when cruising on the highway, but they’re willing to sacrifice a bit of comfort for better performance; they don’t like the space between a car’s tire and the wheel well (called the “Dead Cat Hole”); and they want to improve performance at the track. So let’s break those down one at a time and consider the implications for suspension options.

Highway Cruising/Occasional Track Use. If you’re generally satisfied with the ride quality, but you just want a sportier suspension, then consider coilovers that only offer height adjustment. To help you choose which one to get, start by finding out the spring rates of your current suspension. Many stock suspensions use progressive spring rates which makes this task difficult, but not impossible to do. (A progressive spring becomes stiffer the further compressed it becomes. Springs with consistent spring rates are considered linear.) A typical 3000 lb. sporty car with McPherson Strut suspension design might have springs in the 400 to 450 foot-pound per inch range. Higher if a heavier car, lower if a lighter car. If you’re happy with your current spring rate, then find a coilover with a similar rate. Just by switching from progressive to linear springs you will notice a difference in the ride. If possible, try riding in a car with a higher rate and see if you can tell the difference (especially on the track.) For a dual use (street/track) car, consider going with a spring rate that’s 50 pounds higher than your stock suspension, then fine-tune the ride with adjustable swaybars (more on that below). In this instance, if you are not interested in learning more about suspension tuning, then the right height-adjustable coilover can help you avoid the Tyranny of Choice by not having to worry about other changes in geometry that come with lowering your car and choosing dampening settings. Just set the ride height to be about where it was stock and enjoy the ride. If you want to change the ride-height, then press on.

Dead Cat Hole. Start with a baseline by measuring the ride height as the distance from the center of the wheel to the bottom edge of the fender directly over the wheel center. (This assumes stock size tires.) This is easier to measure than trying to figure out chassis height from the ground. We recommend you take two measurements as a baseline as you try to figure all of this out: Measure the wheel center to fender height for all four wheels, then measure the height from the ground to your four jack points. Compare the heights front to rear to assess Rake. Rake is defined as “the angle between the vehicle and the horizontal axis of the ground. If the back is higher than the front, you have positive rake. If the front is higher than the back, you have negative rake.” Generally, positive rake is seen as advantageous for weight transfer under braking. Measured in this fashion, most vehicles will have between three-fourths and a full inch of positive rake. It is important to maintain rake when lowering the car.

Take our 2006 MINI Cooper S test mule as an example. We were running H&R Sport Springs over Bilstein Sport Struts with SPC Adjustable Camber Plates in the front, and Hotchkis Adjustable Camber Arms in the rear. This is one of our favorite combinations for a first generation MINI owner who wants a bit of lowering and a sportier ride without switching to coilovers. We had a wheel center to arch height of 13 inches all around with 5 inches of ground clearance at the front jack point and 6 inches in the rear. But we also always felt the dampers didn’t quite match the spring-rate leading to occasional harshness, especially for high-frequency compressions on the highway (though we really like them on the track). Also, the H&R springs are not stacked straight so when adjusted to add negative camber, they tend to bind against the strut tower. As a result, we generally could get only 1.9 degrees of negative camber in the front. Since the next step up in performance was to switch to a true coilover, we decided to give the Speedtech Coilovers a try.

The recommended height from the spring seat to the pinch-bolt on the front suspension is being between 7.5 and 8.3, and in the rear between the spring seat and lower strut mounting bolt it is between 7.3 and 8.3 inches. That range for the front, however, assumes you are using the stock mounting plates. The SPC Camber plates we were using make the entire strut assembly height 1/2 an inch shorter than when using stock plates (which we initially forgot) so you have to take that into consideration when trying to figure out where to start. We thought that the top end of the range (8.3 inches) was likely close to where we were starting with the H&R springs so we initially set both ends at 7.75 inches from spring perch to measuring point respectively.

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That guess was pretty good for the rear so we left it there and adjusted camber to negative 1.75 degrees with 1/8 inch of total toe in. (Alignment for high-speed driving is a whole other topic to cover some day.) The front was too low because we didn’t compensate for the lowering effect of the camber plates. The final setting ended up being 8.125 inches from the spring perch to pinch-bolt. We set the alignment to 2.2 degrees of negative camber with zero toe. We can probably get a little more negative camber out of the set-up, but will wait and see how the tires wear once we get more time with this set-up at the track. These settings resulted in 4.5 inches of ground clearance at the front jack point and 5.5 inches in the rear, and 12.5 inches center to arch in the front and 12.75 inches center to arch in the rear. When we get an alignment again in the spring, we’ll probably bring the rear down another quarter of an inch to reduce the rake a little bringing the rear recommendation down to 7.5 inches.

When you lower the car you need to be concerned with other changes that also occur to the suspension geometry. Generally there is an increase in negative camber that comes with lowering. Some increase is usually considered good thing for front-end traction, but can be a bad thing if it leads to premature tirewear in the rear. Most coilover users will also want to pick-up adjustable camber plates for the front (many are included in the coilover design, check with the manufacturer) and camber arms or links for the rear. For cars that see track use, tire choice also affects camber needs with some tires working best with lots of negative camber.

How low can you go? Assuming you are not limited by the angle of your driveway or height of any speedbumps, you can test your new coilover limits by disconnecting any sway bars and installing the strut with bumpstop and no spring. Your coilover manufacturer should tell you the dimensions of your springs when at maximum compression. Install your road wheel and use a floor jack to raise the wheel carrier until the strut is fully compressed (against the bumpstop) or the tire begins to bind with the well liner. Using the dimension of your spring at maximum compression, measure down that distance from the spring cap to the barrel of the strut. Mark that spot and put a second mark 1/2 inch above it (closer to the spring cap). This second mark is the lower limit of where you can safely position the threaded spring-seat lock-ring on the strut barrel. The half inch change to the measured height was there to correct for camber correction later in your alignment. (Remember, this is the limit of how low you could go, not how low you should go. We generally do not recommend lowering MINIs beyond 4 inches as measured at the jack point.) For this MINI application, we’re already pretty close to the limit in the rear, but the front could go quite a bit lower.  It just wouldn’t be very practical.

Track Performance. The ST Suspension for MINI is essentially the same as the KW v1, but at a lower price point. The coilovers are height adjustable, but the dampening is fixed. We played with Koni adjustable dampers before and realized we never adjusted them. We always felt we got more out of adjusting the sway-bars than the struts — which either says something about the geometry of the MINI or our ability as suspension engineers (or lack thereof.) We wanted a suspension that was fairly compliant; offered a positive feel on turn-in; and wasn’t harsh for the high-way trip to the track. And we think we nailed it with this one.

rearsuspslice

We run a 22mm adjustable rear swaybar. Thicker swaybars effectively increase the spring rate relative to body roll, but not when both wheels across the axle move in unison such as when you hit a seam on the highway. On max performance summer tires with the bar on full stiffness, we had just a little too much throttle-lift over-steer for my taste (and skill), but set on the middle setting, it was just about perfect. (Because we were running a new configuration of the track, we couldn’t compare lap-times to previous weekends, but could tell we were hanging better with some of the faster runners than usual.) We can now fine-tune the suspension by playing with sway-bar settings and tire pressures, and worry about dampening rates. Once we figure out how to maximize this set-up, then it’s time to start thinking about two- and three-way adjustable coilover systems.

We’d like to hear from you. What was your experience with your first coilover system?

Want more?
Learn more about understanding shocks here.
Learn about the MINI suspension here.

How to use Video and Telemetry to Improve Driving Performance of HPDE Students

Part 1: Camera Placement

Video can be a valuable tool if it is used appropriately. Search the internet and you will quickly find many videos of your favorite track — some more useful than others. The good ones can help you learn the line before you drive the track for the first time. Others are intended merely to show the world that you drove on the track. If that’s all you want out of video, then stop reading, this article isn’t for you. This article is about learning from your videos. So let’s build up to it, starting with camera placement and then talk about data analysis.

Before you place a camera on your car, think about what you want to get out of it and what restrictions there might be that limit your options. Do you just want to show your friends the track? Do you want to learn the line? Do you want to see how close your wheels really are to the apex on certain corners? Do you want to record what happens in front of you? Or do you want to see your inputs as you drive around the track? Those decisions will help guide camera placement.

Compare the views from the two videos below. The first one is mounted inside on the front windshield (old, non-HD camera) and the second (iPod 4G) is positioned behind the driver. Driving through some fluid, understeer quickly becomes oversteer (and oversteer again). How did the driver? You cannot tell from this view.

In this second video, we see the driver quickly catch the over-steer and accelerate out of the corner, showing the importance of quick hands.

Camera Position and Live Timing. Most High Performance Driver Education (HPDE) events run by car clubs have rules against live timing. You will need to position any recording or timing device in the car in such a way that it does not give live feedback to the driver. For external cameras, many clubs restrict the use of suction mounts, requiring a hard mount. Check with your club before you buy. Even if suction mounts are allowed, be sure it can withstand the wind and vibration of being driven at speed. Position the camera so it does not impede the driver’s vision and locate it in a place that it is visible to the driver directly or in a mirror. Never consider externally mounting a camera you aren’t willing to sacrifice to the Goddess of Speed. Low positions such on tow hooks are visually interesting, but not very helpful for learning. Better is mounting on the roof along the center-line of the vehicle, above the interior mirror with a view of the front hood and fenders. This will show car placement on the track and traffic directly ahead. This placement creates a video that is a good tool to show general car placement, learn a track, and to film following a car directly in front of you. Because it does not capture driver inputs, it is not our preferred placement. If your camera is light and small enough (Replay XD 1080 Mini for example) consider using a suction mount to place it on the windshield inside of the car and tether it to the mount for the passenger visor. For cars without rollbars, this is often your best option. It offers a similar view as on the roof and the camera is protected from the elements. It can easily be controlled by the instructor from the passenger seat. We’ll start out on the Summit Point Main Circuit.

summit_main_1

Windshield Mounted View. Positioned behind the interior mirror, this is the view you get of the track. This view is useful for general track orientation. But you really can’t learn that much about the driver’s inputs from it. [Note: I’m using an old camera that is not HD. The new cameras integrate with the data overlay much better.]

Same Lap with Data Overlay.
By adding telemetry data from Harry’s LapTimer and data from PLXdevices Kiwi 2, now we start to get a feel for use of throttle, corner speed, lateral forces, and gear selection.

Same Lap with Camera Behind Driver. In this video, we’re using an iPhone 5S in an Optrix XD5 Case mounted to our rollbar. By mounting the camera behind the driver, now we start to get a feel for driver input. Is the driver struggling to maintain position because the seats are not supportive. Is the driver looking into the corners? How are the driver’s hands on the wheel? If you don’t have a rollbar or harness bar, you can get a similar view using a head-rest mount such as the CruiseCam Mount.

Same Lap with Picture in Picture Finally we can put it all together and see both the driver and the road ahead. Harry’s LapTimer (HLT) has the ability to control certain secondary cameras via Bluetooth, such as a second iPhone, an iPod G4, or GoPro Hero3. In this case, we imported and synced the video from our Replay XD camera within the HLT application

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That second camera could be showing a view back toward the driver from the front, it could be showing feet on the pedals, or it could be a reference lap to compare one lap (or driver) to another. You are really only limited by your imagination (and equipment).

Part 2: Apex and Entry Speed Analysis

In Part 1, we discussed camera placement and capturing data. In this post we’ll explore what we can learn from the data we’ve captured. The track this time is the Shenandoah Circuit at Summit Point Motorsports Park. This is a challenging 2.2 mile, 22 corner road-course used primarily for driver’s education events that features a dimensional replica of the Nürburgring-Nordschleife’s banked Karussell turn complete with 20 degrees of banking (but without the Graffiti).

shenandoah

The configuration in use this day omitted the three chicanes and used the short Range Straight between turns 9 and 11. (I’ve driven more than 40 days on this course and I’ve never seen cars use the chicanes.) It is not a very high-speed course and the walls do seem very close at times, but I really enjoy it, especially in the MINI. This lap at 2:06.75 is about average for me on this weekend. The fastest of the weekend was a 2:04.67. (My best ever in this car was a 2:01.78 but that was on R-comp tires; I was on street tires this weekend.)

Video was captured on a Replay XD MINI 1080 mounted on my rollbar; data was provided by a PLX Devices Kiwi WIFI; positioning was provided by a Dual AV XGPS; and timing came from Harry’s Laptimer (HLT) on my iPhone. The video was edited in Quicktime and later added to the HLT dataset on my iPad.

In this post, we’re going to focus on an examination of cornering speeds. This post isn’t about outright best lap times, rather improving driver smoothness and carrying as much speed as possible through the corners. Lap time is just one of many ways to measure performance. Using data from HLT that was exported to Google Earth, we can plot cornering speeds and lateral G-forces over the track-map. We’ll compare the two laps of this weekend to the reference lap of 2:01 (fastest lap last year in R-comp tires in this car). The color bars are supposed to represent the direction and intensity of the G-forces: Green is 0.4 – 1.0 G; Yellow is 1.0 – 1.25 G and Red is greater than 1.25 G. Our goal for the weekend was to see how close we could come to this level of performance using street tires.

Shenandoah G Forces

The best lap of the weekend on street tires was a 2:04.67. (The spikes in the data show how much less composed the car was on street tires at these speeds than on the R-comps the previous year.)

Shenandoah G Forces 2

Here’s the lap we’re trying to analyze, 2:06.75. Let’s try to find where we’re losing almost two seconds. Lower apex speeds mean lower exit speeds, leading to lower top speed at the end of the next straight. We know that we can’t expect the same level of grip from these street tires that we got with the R-Comps, so let’s look where we might make up some speed. Shenandoah G Forces 3

We can then overlay the 2:06 lap on the 2:04 lap to help see where we’re losing time. The data suggests our theoretical best time is closer to 1:59, even on street tires. In HLT, the image is dynamic so you can drag your finger around the course and see the plots in the data, you can get a similar result using the HLT data export and looking at your laps in Google Earth. Shenandoah G Forces 4

  • Start with Point A, The Loop. Both the reference lap and the 2:06 lap show an apex speed of 42 MPH which is interesting considering that the reference lap was on R-comps. This shows that there’s a lot of grip on corner entry because of the crown on the road. Use it to your advantage. (This was actually the one spot where the 2:06 lap was better than the 2:04 lap indicating I could have done better than 2:04 had I carried more speed into the corner.)
  • At Point B, the Stone House Straight, I carried a lot more speed into the Hook on the 2:04 lap. As the weekend progressed I gained confidence in braking later, resulting in the same apex speed, but the line exiting Turn 8 was much better in the 2:04 lap, resulting in higher apex speed at Turn 11 (Point C).
  • That extra speed carried all the way to the entry of the Karussel, Point D. Through the Karussel and into the Karussel Esses, however, I actually had better speed on the 2:06 lap since I had a better exit from the banking. (You can see the slight movement to the inside of the Karuessel on the exit where I lost speed heading up the hill — red spike in the wrong direction).

So what’s the take-away from this analysis? I can brake a little later and carry more speed into the apex of the Loop (A). Likewise, I can carry a bit more speed and brake later into the Hook (B), concentrating on getting a good launch out of Turn 9 (avoiding the curb on the inside) to carry more speed into Turn 11, carrying more speed at the exit (C) which will result in more speed at the end of the Bridge Straight leading to the entry of the Karussel (D). In other words: Brake later, brake less. Words to live by.

Part 3: Traction, G-loading, and Getting the Power Down

For the final installment in this series, we’re going to look at what the data is telling us about how hard we’re trying. To minimize time on the track, the drive should spend as much time at full throttle as possible; brake as little as is necessary to turn; and be trying to get back to full throttle as soon as possible. There is no coasting involved, yet we all know we coast from time to time. Now with data acquisition, we can start to see where we are doing it, or more appropriately, where we’re trying to put the power down but it isn’t working. For this analysis, we’re going to look at the third track at Summit Point, the newly expanded Jefferson Circuit. (For a detailed analysis of the new Jefferson Circuit, click here.)

New Jeff

As we mentioned in the post analyzing this track, the color on the path of the car shows acceleration (green) or deceleration (red). Note that deceleration might just be lifting as in between 2 and 3 or the apex of 4 or 8. Green speed readings on the track show max speed before deceleration and red shows apex speed. The bars in each corner show relative lateral G load. Green bars are .4 to .8 Gs. Yellow bars are .8 to 1.1 Gs. But there are a couple of other charts in Harry’s Laptimer that inform us about traction events. First, here’s what that lap looks like:

When we look at the overall picture of traction on this course, we see our max performance summer tires are performing pretty well. We are pulling a maximum lateral load of 1.22 Gs in the tightest corner, Turn 7. The first chart shows our overall traction circle which is a little better than expected for a street tire.
Traction Circle

The second chart shows the maximum lateral loads on the corners. It’s also showing us the areas of the track that are unsettling the car. This is similar to the Speed chart that shows where we’re having trouble putting the power down.
jeff plot 2

When we start looking at the Speed Chart we start to see areas where we’re having trouble making a clean transition back to full throttle at the apex of certain corners. When the peaks of the lines look like Vs, then it’s a smooth transition. Where you see Ws, then there’s a problem.
jeff plot 3

Compare the areas with the arrow to the circle and the square areas. The arrow shows the apex of Turn 1 and a very clean transition from deceleration to acceleration. The orange squares show the effect of the rough road surface before the apex to Turn 6. Not much I can do about that. But take a look at the green circles. This is the trick Turn 7. It’s a decreasing radius corner where the entry is a bit off-camber, there’s very little grip at the apex and a tricky transition immediately into Turn 8. I’m not making that transition very smoothly and am not able to steadily accelerate through that corner. There’s a corner I can work on. Here’s another way to use the tool:

Jeff plot 1

This chart is showing a comparison of two laps. The faster reference lap is in orange. The lap being studied is in gray. Until Turn 7 this lap was ahead of the reference lap. You can see the difference in speed at point A and the difference in time at Point B. But I over-cooked Turn 7 and by the time I was in the braking zone for Turn 11, was already behind. By the time I got to the end of the back straight (Point D), I had to lift and let another car pass. This just goes to reinforce the old adage of “slow in, fast out.” By being “fast in, slow out” of Turn 7, the rest of the lap was compromised.

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Track Analysis: Summit Point, Jefferson Circuit Extension


Last weekend I had the chance to drive and instruct on the extended Jefferson Circuit at Summit Point. Below is my analysis of the changes and a description of my line around the track. This works for me in a FWD MINI on summer street tires. Your results may vary. No wagering. (In-car video by ReplayXD.)

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The extension (turns 4 – 9) adds about a half a mile to the old track and doubles the number of corners. I think most old-timers would have preferred if they had just renumbered the new section as corners 4a to 4g instead of renumbering all of the corners, but we’ll use the new numbering scheme. The old track could be run in both directions. The new layout only works in a counter-clockwise direction (though you can still use the old course in the other direction.)

Google Earth hasn’t yet uploaded a new image of the circuit so the plot shows the path through open fields, but it is actually paved, just not well (more on that in a minute.) How to read this chart: Turn numbers are in circles. The color on the path of the car shows acceleration (green) or deceleration (red). Note that deceleration might just be lifting as in between 2 and 3 or the apex of 4 or 8. Green speed readings on the track show max speed before deceleration and red shows apex speed. The bars in each corner show relative lateral G load. Green bars are .4 to .8 Gs. Yellow bars are .8 to 1.1 Gs. Notice the lateral load where the new track rejoins the old track and in the middle of the back straight. There the car is going straight and the lateral load is from the unevenness of the surface. You see some of that on the front straight from 14 to 1 as you drive across the crown to set up for turn 1. Red arrows show apex visuals. If you already know the old Jeff, then jump down to Turn 4.

T1 entryWhen you enter the track from pit-out, stay to the right all of the way to the apex of turn 1, otherwise, when at speed cross-over from right to left on the front straight and look down the track to the flagger’s bucket. RWD cars set up to the left for turn-in. The road is crowned so FWD will want to be more in the middle of the left half of the track or you’ll never get over the crown to the apex.

T1The apex is very late and almost at the end of the curbing. You can ride the middle part of the curbing, but stay off of the end as it will unsettle the car. Stay to the right upon exit and let the car settle before turning-in to turn 2.

T2Turn 2 and 3 should flow. If you’re early for 2, you’ll also be early for 3 so wait to turn in and make 2 a very late apex. Lift or tap the brakes to turn-in to 3.

T3Turn 3 is one of the few corners where you can ride up on the curbs without unsettling the car. Apex is very late and carry as much speed as you can. Don’t worry about track position on track-out as the entry to the next corner is rough and you’ll probably have to lift anyway to get back to the apex.

T4Turn 4 is also a late apex. Ride the rumble strips and try to straighten 4 and 5 as much as possible.

T5The exit to turn 5 is the roughest spot on the track. Point the car straight after the apex and brake in a straight line. Wait for the second bump before turning-in to turn 6.

T6Set the car about a car-width from the curbing and late-apex turn 6 at the top of the hill. Open the wheel and let the car track out to set up for turn 7.

T7Turn 7 is the most difficult corner on the track. You must be patient, especially when your tires are cold. It is a decreasing radius corner. Look for the path of the patch. Set your entry squarely in the middle of the patch and then pinch-off the apex. Trail-braking helps. If you don’t sufficiently load the front-end, expect to under-steer through the apex and off the other side of the track. Track out to mid-track.

T8Treat turns 8 and 9 as one double-apex corner. Do not track too far out in the middle as the pavement drop off is pretty severe.

T9Ride the curbing on curves 8, 9, and 10.

T10Late apex 10 but get on the power early to increase the length of the straight. The point where the new track joins the old is quite bumpy so stay away from the track edge.

T11Stay 3 feed from the edge in the braking zone to 11 to avoid more bumps. Turn 11 will really hook up when done right. Release the brakes as soon as the car starts to turn-in and power through the exit using the full track width. Cross over from right to left to set up 12.

T13EntryStaying as far left as possible, turn in for 12 as soon as 12 and 13 line up and straight-line 12.

T13Stay off of the curbing on 12 as it will really unsettle the car. Downshift and brake for 13 in a straight line. Some people are able to carry enough speed to brake once through 13 to set up turn 14. In the FWD MINI I have to release the brakes in 13 to get the car to rotate and can actually accelerate a little up the hill before turning-in for 14.

T14 EntryRWD set up 14 by going as deep as possible for the entry. FWD don’t go too deep or you won’t be able to cross the crown to get back to the apex of 14.

T14
The apex of 14 is very late. Stay off of the curbing. If you are tracking out to the edge of the track before the pit-in lane, then your apex was early. Cross over from right to left and do it all again.

Larger photos here.

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:

  1. According to the National Weather Service, the wind-chill of 7 degrees F at 109 MPH (the max speed of their calculator) is -29.
  2. Seat heaters are wonderful things and you don’t want to stick your hand outside if you don’t have to.
  3. 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.
  4. The Roots-type Supercharger really likes the higher density air that comes with extremely low temperatures.

MINI at SP

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.

Front Straight

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.

new bar

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.

installed

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.

finished

Codes P1688 and P0107, WTF? Replacing Broken R53 MINI Crank Damper

I decided to take the MINI to work this morning to see if everything was back in order after recently replacing the motor mount. The engine seemed to be running a little rough, but I just figured the new motor mount was a little more firm than the old one. I got off the highway after one exit due to traffic and I got the dreaded CEL (Check Engine Light.) I hate that light. It might as well say, “Yo. Something’s wrong. I know what it is, but I’m not going to tell you. Here’s a hint: It’s under the hood….” And the car went into limp mode. Fortunately I still had my code scanner which told me it was code P1688. That’s handy. What does that mean? Ugh. I just turned around and headed home. I’d have to reset the ECU every 5 minutes, but it is a pretty hilly route so I could do lots of coasting. So what is P1688 you ask? Not what it seems.

P1688 is the code for “Electronic Throttle Control Monitor Level 2/3 Mass Air Flow Calculation”. Which would indicate a problem with the throttle body, but I also had code P0107 last week at the track which is “Manifold Absolute Pressure/Barometric Pressure Circuit Low Input”. With those two together, the car is saying that for a given amount of throttle, there just doesn’t seem to be enough boost going on. And on the R53 MINIs that usually means the crank pulley (or more accurately, harmonic balancer) is shot.

The stock part is about $200, but since this car gets lots of track time, better to upgrade to a more robust model. ATI Performance makes a Super Damper for about $350. As the old damper started to disintegrate, it took a good amount of the old belt with it. The old belt has had one rib sliced off. These two belts should be the same width.
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Once you get the right front up on a jack-stand, remove the wheel and fender liner, and use a belt tensioner tool to remove the belt.
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You can’t tell if the damper has gone bad by viewing it from the front, but when you look at it from the side, you’ll see a gap developing as the belt pulley separates from the damper.
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ATI includes basic instructions with the new super damper. Here are some tips to make it easier on you. (Use at your own risk.)

You can use a universal pulley removal tool if you’re careful. You will need to buy 3 M6 bolts that are long enough to work with your tool. Be sure to get the hardest bolts you can (10.9). First step is to remove the center bolt. Use some penetrating oil before you start. You may get lucky and be able to remove it just by putting the car in 6th gear and having someone stomp on the brakes. But for me, the crank still turned. I ended up using a brace to stop the crank from rotating. In this case, it’s a tool for removing a fan from an E30. Go figure.
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Now the real fun begins. If your tool did not include an appropriately sized center pin, then put the bolt back in and tighten, leaving about a half inch of threads showing. Attach your pulley removal tool. Have a helper hold the bolt with a wrench as the pulley tool will be pushing against the bolt and it will try to screw back in. When the bolt makes contact with the damper, you have to back it out some more and adjust everything and go again. Make sure the M6 bolts are not twisting. You should be able to compare the location of the damper to the other pulleys on the front of the engine to judge if you’re making progress. I ended up having to replace the bolt with a longer one to get the last quarter of inch of travel needed to remove the damper.
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Once it came off, you can see how badly damaged it really was. (Hint: this is supposed to be one piece, not two.)
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With the damper removed, you can see where it scored the engine as it oscillated. I’m surprised that didn’t make more noise….
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Update: Having had to do this again two more times here are two helpful tips: 1.) Replace the crank shaft seal before you put on a new damper.  See this post about that. And 2.) from that same post, heat the new damper in the oven before you install it.  Yes, greatly simplifies the process.

Installation is the revers of removal. No, not really. From the ATI instructions: Inspect the crank for any burrs or nicks. Blow out the threaded hole to free it of debris (and clean the engine before you start since you can’t really get to it once installed.)
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Start the new super damper by hand. Heat it with a heat gun or hair dryer if it doesn’t start easily. Use the supplied long bolt and washer to grab enough threads to pull it on most of the way. Continue until it bottoms out, then remove the bolt.
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Use a new OEM bolt to finish installation. Apply blue loctite and torque to 85 lbs. Reinstall the belt, taking care to route it correctly.
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Carefully release the belt tension using tensioner tool. Start the engine to check if everything is OK and the belt alignment is straight. Then reinstall the fender liner and wheel. Torque wheel to 87 ft lbs.

Early Spring Track Days

In between early Spring snow squalls, GeorgeCo found some time to go to the track with the local Audi club. They needed someone to instruct on the skid pad, and GeorgeCo always needs more track time. Win-win.

With temperatures in the 40s and the GeorgeCo Porsche still wearing all-season Conti tires, we weren’t out to set any lap records. This was all about shaking the cobwebs and making sure the car is running well. The track temperature was very similar to the last day at the track last November. The work to clean our the radiators resulted in lower operating temperatures by about 10 degrees. Oil pressure was consistent, and the car is handling well, even if the suspension is a bit tired.

I’m still working on the ideal camera placement. I like having the camera between the front seats like in the MINI, but in the Porsche, that’s not an option. I tried it mounted to the windshield but that’s too far forward and between the rear seats, but the lens is too wide.

On the skid pad, I attached the camera to a cone and tried putting it on the passenger window. The telematics system doesn’t know what to do with the loss of traction. The revs and the gear indicator go nuts in the video.