The Truth About Cars » braking http://www.thetruthaboutcars.com The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Wed, 01 Oct 2014 16:21:26 +0000 en-US hourly 1 http://wordpress.org/?v=3.9.2 The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars no The Truth About Cars editors@ttac.com editors@ttac.com (The Truth About Cars) 2006-2009 The Truth About Cars The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars » braking http://www.thetruthaboutcars.com/wp-content/themes/ttac-theme/images/logo.gif http://www.thetruthaboutcars.com Piston Slap: The Fuel Hating Tranny http://www.thetruthaboutcars.com/2013/02/piston-slap-the-fuel-hating-tranny/ http://www.thetruthaboutcars.com/2013/02/piston-slap-the-fuel-hating-tranny/#comments Wed, 20 Feb 2013 12:56:48 +0000 http://www.thetruthaboutcars.com/?p=478193 Eric writes: My question is for Sanjeev Mehta. I purchased a 2010 4 cylinder automatic Toyota Camry LE new and have been using it as my daily driver since. My commute is almost all city driving, so I noticed a quirk about the car right away. During deceleration, the transmission seems to starve the engine […]

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Eric writes:

My question is for Sanjeev Mehta. I purchased a 2010 4 cylinder automatic Toyota Camry LE new and have been using it as my daily driver since. My commute is almost all city driving, so I noticed a quirk about the car right away.

During deceleration, the transmission seems to starve the engine almost to stalling, followed by a downshift and repeated until a stop is reached. This makes for a very jerky process for people like me that like to lightly brake for longer distances before stopping. I asked the dealership about it, they told me it was normal and it will go away after ”learning” my driving habits. Two years later, it still is around. From cruising the web and Edmunds, it seems all of the Camrys with the 6 speed auto suffer from this problem. My question is, why does this happen, why on earth would Toyota put this in their cars, and why has every professional review I’ve read of the car not highlight this problem? Is there anything I can do to alleviate this persistent problem? I had the dealership apply a TSB Toyota released for this issue a year ago, but it has not helped at all.

Sanjeev answers:

Do other TTAC writers have the same common/uncommon name mix up problem too?  What say you, Jake Baruth, Stephan Lang and Derrick Kriendler? But, I know, I know…not everything is about me. So let’s do this thang.

After a bit of Googling, perhaps your dealer applied T-SB-0287-10:

“To improve the shifting performance and smoothness during acceleration, the Engine Control Module (ECM, SAE term: Powertrain Control Module/PCM) and Transaxle Control Module (TCM) calibration has been revised.”

But this link points to something more relevant, and interesting. Many (all?) electronically fuel injected vehicles cut fuel to the engine when “extended braking” in this manner.  They’ve done it since the dawn of EEC-IV fuel injection on my super-precious Ford Fox bodies, that’s for sure.  But ye olde Foxes (5.0V8, 4-speed auto) don’t bog very much at all as they slow down to idle. So what’s the problem?

When you slow down through 6 forward gears, the motor bogs down far more often than older vehicles with only 3 or 4 cogs to swap.  When you combine this EFI program with the lack of low-end torque in modern engines (relative to the low revving engines from yesteryear) and the torque converter’s stall speed (and the computer programming added to it) you have a recipe for a boggy, clumsy downshift. In these “extended braking” situations, that is.

Simply(?) put, there are computer programs designed for maximum fuel efficiency, too many downshifting gears, computer controlled spinning fans (torque converter) and a relative lack of balls in rev-happy modern engines to ensure smooth downshifting. You’re gonna have to live with it.

Or change the way you brake.  Or get a Lincoln Town Car stick shift.

 

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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Trackday Diaries: the long night, street habits on the track. http://www.thetruthaboutcars.com/2010/07/trackday-diaries-the-long-night-street-habits-on-the-track/ http://www.thetruthaboutcars.com/2010/07/trackday-diaries-the-long-night-street-habits-on-the-track/#comments Thu, 15 Jul 2010 16:22:13 +0000 http://www.thetruthaboutcars.com/?p=360926 If you want to spend fifty days a year on-track, or even twenty, every dollar must be watched. A decent hotel can run eighty bucks or so, including tax, near most East Coast venues. Two hotel nights an event, ten events a year, will run you sixteen hundred bucks minimum. A few years ago I […]

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If you want to spend fifty days a year on-track, or even twenty, every dollar must be watched. A decent hotel can run eighty bucks or so, including tax, near most East Coast venues. Two hotel nights an event, ten events a year, will run you sixteen hundred bucks minimum. A few years ago I came up with a way to save at least eight hundred of those dollars: drive to the East Coast the night before. Playing a bit of “pickup ball”, to be coarse, can save the other eight hundred. It’s also possible to sleep in bathtubs for free if you have generous friends at the event, so pack a pillow and thick blanket along with your torque wrench and HANS device.

Sunday night passes into Monday morning and I am on the road at 12:30AM to cover the 371 miles to Summit Point’s Main Course. There’s less traffic at night anyway, making it easier to read Wikipedia whenever I have 3G signal. I’ll pick a topic and wander through. From 2AM to 5AM or so I’m reading about the late Michael Bloomfield and the story of the “Super Session” record with Al Kooper and Stephen Stills. A few reviews, a variety of technical diatribes about the ’58-’60 Gibson Les Paul. The maple top is glued to the mahogany body, which stresses the maple under most conditions of heat and humidity, causing the guitar to resonate a bit more. Fascinating stuff. Yes, I read and drive. You’re not allowed to do it in press cars, but I hold the title for the Boxster and therefore if I want to spend the whole trip playing a Martin Backpacker on my lap I’ll damn well do it. If you want me to devote my full attention to the road, raise the speed limit to 195 and give me a plastic trophy for arriving at my destination before everyone else.

The last seventy or so miles takes place on a variety of two-lane roads. Now the morning trucks are out. Passing traffic in the Boxster avec trailer is tricky business but it must be done. Finally I’ve arrived and can get set up. Ugh. My latest set of $25 front tires is an inch too tall. They’re 40-series instead of 35-series. Makes a difference. I travel with a prybar for these occasions. I use the prybar to bend the spring mount on the shocks so the wheels will turn and head out.

Summit Main is an old-school track. It’s killed racers, and it’s even killed an HPDE participant as recently as 2007 or thereabouts. I encourage students to treat it with respect. The question I ask them is: “Where is your nose pointed when you are accelerating out of the corner?” Too often, the true answer is “at a wall” instead of “down the track”. If you are pointed at the open track or a nice safe runoff spot when something bad happens, you are likely to still be doing trackdays next year, rather than waiting for the orderlies to come change your diaper and move your arms to a different position for you.

Turn Four is one of my very most favorite places in the world. I’ve borrowed these photos from the Alfa Club.

What you cannot see is that it is seriously downhill and off-camber. Spec Miatas don’t need to lift for it, but they are also usually a bit iffy about full-throttle on the way out. This is what you see at the exit:

The tires on the left are calling your name as you head down the hill full-throttle. I drive this section with full commitment. It’s hard to beat the Boxster through this section; even the well-driven Ariel Atom ahead of me in one session swells a bit in the windshield as we dive to the inside of the 180-degree Turn Five. Once we reach the front straight he blasts off like a tube-frame Space Shuttle.

I have good students this weekend; a fellow in a 993 Carrera and someone with what amounts to a NASA GTS3-class BMW M3. Both of them suffer from what I think of as “street habits.” The first big street habit has to do with brake pressure. Imagine you are coming off the freeway toward the stop sign at the bottom of the ramp. How do you slow the car? Obviously, you start with light pressure on the brakes and build as you come closer to the stop sign. Your maximum pressure on the pedal probably happens right before you stop. That’s a street habit. All novice and intermediate drivers do it on the track as well.

What we should be doing is to quickly apply the maximum possible brake force at the brake marker and hold that pressure until we’ve arrived at the proper corner entry speed. Most people have never done this in their lives; maybe once, when a deer jumped out in front of them and stood there waiting for impact. On a racetrack we do it every corner, every time. If you brake too early… well, it didn’t kill you, did it?

Another street habit is unconsciously maximizing g-force in a corner. Imagine that you are at the Tail of the Dragon with all the jerkoffs in their S2000s and the neon rolling GSX-CHICANES. You’ll take each turn in a manner designed to press you into the seat with all the g-force possible, which means going in a little too fast, riding the outside of the corner, and not accelerating until you’re way past the exit. Your brain feels that cornering force and says, “Awesome! We’re really booking along, dude!” Meanwhile, I’ve slowed down more than you did, turned more than you did, and I’ve accelerated out of the corner while you’re marking time.

Both of my students acquire a lot of speed during their eight sessions and pass a lot of their session-mates. This becomes addictive so they start to get a little crazy when cars appear up the road ahead of them. They want to push harder, and the old subconscious tells them they need to go faster in the corners. Without really meaning to, they start turning in early without braking as much. That’s too fast so they correct by turning the steering wheel more, which slows the car. It feels very fast, but now the Corvette ahead of us is getting smaller, not larger. When in doubt, relax and drive your line.

By the end of the first day, I’ve been awake for 22 hours in solid heat, six of which I spent on a racetrack, and I’m totally ready to sleep in a bathtub. Good times! Tomorrow we’ll talk about two more street habits, and how tire heat affects the speed at which you’ll hit a tire wall.

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