Andy Hollis on Data and Suspension Tuning

Long-time readers of this blog will know that we’re huge fans of using data (especially video) to improve driving performance. A recent talk given by Andy Hollis at the SCCA Motorsports Expo reminded us that data comes in many shapes and sizes; and that it often involves zip-ties.

Andy started his presentation with the rhetorical question, “What is Data?” He asserted that data is the digital representation of a car’s performance across a set of constraints, either recorded or perceived. Your “butt-dyno” just isn’t calibrated fast enough for the rate of inputs per second of a car at speed. The advantage of data over “feel” is objectivity.

For example, do you sense that your suspension is bottoming out in a given corner? Put a zip-tie around the strut shaft where it meets the tube and see how far it moves. If it moves as far as the photo below, then it is bottoming out.

ziptie

Want to know how much body-roll you have?  Someone is always taking pictures at autocross or track events, so find a good high-resolution image of your car head-on and measure the angle? A good amount is probably in the two to four degree range.  More and you get too much weight transfer to be efficient, too little and you’re losing grip.  If the angle looks good, what is the loaded tire doing? Do you have enough negative camber?  How about air pressure?  This photos shows body-roll of about three degrees, but the loaded front tire is deforming suggesting more negative camber is needed.

Roll Angle

Data will show some surprising results, such as all other things being equal, a narrower car will be faster through a slalom (think old vs. new Miata). In Andy’s experience, tire compound is more important than width.  And testing requires a different mindset than competition.  You need to be consistent and remember your objectives when testing so you can isolate and focus on the aspect that you are testing.

For suspension tuning, he starts on the skid pad.  Time is the most important factor, not feel.  Use zip ties to see if bottoming out.  Look at tire temperatures front/rear and side to side. To get good data run in 3rd gear.  He uses a 100 foot radius skidpad.  For alignment changes, work on the end of the car that lets go first. For a front heavy car, a thicker front bar can help it push less (again counter intuitive.) Rake is important, but consider dynamic toe effect when changing rake after changing ride height. Once you have steady state on round skid pad, then go to oval skid pad and introduce the pitch variable.  If too extreme, go back to round skidpad and adjust. Next add braking/acceleration on the oval skid pad.  If the rear steps out, it could be a brake bias issue.  If you can’t adjust bias, then go back to suspension. Next he moves on to the slalom and takes acceleration of out if to just work on the transitions.  This requires a constant speed through the slalom. For autocross, a little toe out in the front can help (not recommended for the track.) For an underpowered car with over-steer a little toe out in the rear can actually help, but can also make for an interesting ride in a straight line over bumps. The B Spec cars in PWC are running as much as a half an inch toe out [which is nuts.] In the end you may have to compromise, but consider where you spend most of your time on course.  If you’re running autocross in a small parking lot with many tight turns, you may make changes that are different if most of your time is spent in long sweepers.  The same goes for the track.

Elliott Forbes Robinson on Racing

Elliott Forbes RobinsonElliott Forbes Robinson gave an interesting keynote at the SCCA Motorsport Expo last Saturday talking about what he’s learned during his 37 year career in racing. Following along with Randy Pobst’s theme of fear, he noted that if you’re feeling the adrenaline rush while driving, then you’re probably doing it wrong. It should feel awesome, yes; but not exciting. Exciting is often bad and can lead to surprises. And surprises are often bad as well: wheels falling off, fluid on the apex, no brakes, throttle stuck. It’s not that good driver’s don’t make mistakes, it’s more about how they recover. Like good actors who miss a line in a play, the observer may not notice. For a good driver that mistake could be too fast corner entry, or going off course — just without drama. But it is more a matter of style. He always tries to turn in early (something I hear attributed to Mike Skeen once too.) By turning in early, he’s able to make constant adjustments, but more importantly, he can get on the throttle at the right place, every time. He hardly ever trail-brakes and thinks of braking as the least important aspect of the corner. He tries to get all of his braking done in a straight line. As a result he consistently gets better gas mileage while maintaining competitive lap times.

2 Quart Extension Kit

Hardening Your M96 Engine

I had a nice long chat with Charles Navarro of LN Engineering at the SCCA Motorsports Expo in Charlotte, North Carolina last weekend.  He’s half of the team behind the IMS Solution for M96 engines — the other half being Jake Raby of Flat Six Innovations. I wanted to talk to Charles about preventive measures for the driver who occasionally tracks their 996.  As the Mark I 996s start to depreciate below $15K, they start to become attractive track toys, but given that a decent rebuilt motor is also $15K, nobody really wants to think of their Porsche as an engine with a disposable wrapper.

Assume for the moment that you have a 2000 996 with manual transmission and 84,000 miles on the odometer.  Your clutch and rear main seal were replaced at 67,000 miles, and engine oil analysis shows no signs of abnormal wear.  Your car doesn’t make any funny noises at start up or idle.  There’s no smoke.  You get decent gas mileage, and the car pulls very well (i.e., my car.) If you’re an engineer type, you might describe its operational condition as “nominal.” Most 996 owners seem to suffer under a state of perpetual performance anxiety, just waiting for the lump to implode.  I’ve tried to remain outside that camp, but just like wearing suspenders with a belt, it can never hurt to take extra precautions. 

So besides the IMS Bearing Retrofit which is well documented, what other preventive measures would Charles recommend?

  • Air Oil Separator (AOS): Unless you plan to track your car often, no need to replace proactively. Just check the vacuum at the crankcase. If you are going to see lots of track time, then upgrade to the Motorsports AOS.
  • Thermostat & Water Pump: If tracking often, then consider getting a lower temperature thermostat and proactively replace your water pump.  Use only genuine Porsche parts and do not use pumps with metal blades as they destroy the housing when they fail.
  • Chain Guides: Use your Durametric cable and software to look at cam timing deviation for signs of chain guide wear. Don’t replace unless the timing is off or you see excessive wear (bits of plastic) when you drop the sump cover.
  • Ticking Noises: If hot, then probably lifter.  If cold, then probably cylinder. If cylinder, then the wear may be at the bottom of the stroke and you won’t see it with a borescope coming in from the cylinder head.
  • Oil: Don’t use Mobil 1.  Use Driven DT-40.  If using other synthetic, make sure it has a high level of zinc for metal longevity.  Even if zinc looks good, watch calcium which is a measure of detergent.  High levels of calcium may clean away the beneficial zinc.
  • Oil Starvation.  Since I already have the improved oil baffle, he recommends getting the Two Quart Sump Extension. Since you’re going to replace the IMS bearing, no need to continue to use the IMS Guardian with the low hanging MCD Sensor.  Switch back to a regular magnetic drain plug.

How big of a problem is the IMS failure in 996/997 model 911s? We didn’t discuss it at the show, but most estimates range from 1% to 8% of the cars delivered, with the average for all years of this engine being 4.5% (it doesn’t effect GT2/GT3 models). Sure the failure can be catastrophic, but if you think of the IMS Bearing as just another wear item, it really isn’t that daunting.  Replacement will cost less than a clutch and should be changed again in 75,000 miles.  If you plan to keep your car forever, then go for the permanent solution (aka, the IMS Solution) which is more expensive, but only done once, otherwise, get the bearing retrofit and move on with your life.

Source: http://imsretrofit.com/wp-content/uploads/2013/11/Porsche_Class_Action_Lawsuit_Failure_Percentages_Exhibit1383012197.gif accessed 2/24/15.

Source: http://imsretrofit.com/wp-content/uploads/2013/11/Porsche_Class_Action_Lawsuit_Failure_Percentages_Exhibit1383012197.gif accessed 2/24/15.

Fear: Fight, Flight, or Freeze

Randy Pobst at MSX ExpoRandy Pobst was the keynote speaker at the first day of the annual SCCA Motorsports Expo in Charlotte, North Carolina last week. His speaking topic was fear, but his message was really about vision. We know instinctively that fear causes the fight, flight, or freeze response. Randy noted that rational fear helps control risk.  It can help us perceive scary cars or situations on the track and it nags us to check fluid levels, lug nuts, and safety equipment.  But he also observed that fear hurts driving performance as well.  When we get the white-knuckle grip on the wheel, our pumped-up forearms are incapable of subtle movements. Instinctively we realize the car isn’t handling right, but the tight grip doesn’t give any feel for what the car is really doing. Fear also adds to the physical and mental workload associated with driving, and can cause a loss of focus, causing the driver to miss flags, gauge warnings, or objects in mirrors.  He cautioned that mirror fear also causes mistakes and sets one up for easy intimidation by the competition. That in turn causes timidity, getting run-over, stagnation, missed opportunities, and no improvement.

The biggest impact of fear, Randy noted, was that it makes us look at what we fear — the vision connection.  It makes us look where we fear we’re going, not where we want to be going.  He calls it Mother Nature’s revenge for the industrial revolution: all of our instincts are wrong.  You go where you look and your hands just work it out. (So, by Randy’s own admission, you should still be looking at the apex when you hit the wall.) If you aren’t looking where you want to go, you’ll feed in the power at the wrong time/wrong amount.  It seems intuitive, but if you aren’t going where you want to go, why do you want to go there faster?  Yet you’ll often hear drivers back on the gas in a spin. Look not at what you fear — sound advice.

So how do you alleviate fears?  You can extinct fears by creating new memories. Always be learning, whether that’s attending driver’s schools, seeking coaching or mentorship, or reading.  Randy recommends “Going Faster” by Carl Lopez — the Skippy Bible.  But most importantly is to ask for help “especially if you’re bad…” Randy is a huge fan of the skid pad and getting a stable car set-up.  Remember, under-steer is frustrating; fear is over-steer.  Most importantly, have fun.  Thinking about fun reduces fear.

Installed slice of rollbar

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.

Rearshelfuncovered

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 rollbar

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 lined 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.

Padding

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.

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