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da_joint
post Oct 19 2005, 11:22 AM
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Cine stie vre-un link catre o pagina interesanta rugam sa posteze ptr. a putea vedea si ceilalti.


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florin83
post Oct 19 2005, 11:30 AM
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Da_joint, oricum la noi nu sunt valabile..

n-am vazut filmele, am dat cu presupusu smile.gif
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florin83
post Oct 19 2005, 11:36 AM
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nu pot din motive tehnice (limita max la download e 1mb sad.gif prin tel)
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da_joint
post Oct 19 2005, 11:40 AM
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Heel and Toe Downshift
By Brent Romans

If you have heard of the term "heel-and-toe" downshift before, but you've never known what it means, you've come to the right place. It is the mission of this article to make you a heel-and-toe master, a proverbial Jackie Chan of downshifts. Hi-yah!

A heel-and-toe downshift refers to a specific technique used to downshift a manual transmission car. It might seem bizarre to the general populace, but racecar drivers use it all the time. Once mastered, the heel-and-toe downshift offers the benefits of reduced vehicle wear-and-tear, better driver control and faster lap times on a racetrack.

The heel-and-toe downshift is a rather complex action involving both of the driver's feet, the driver's right hand, all three vehicle pedals and the gear shift lever. The purpose of the heel-and-toe is to smoothly match engine speed to wheel speed. Here is a generalization of how a normal person downshifts a manual transmission car.

Let's say Frank is driving his '01 Volkswagen Passat around town. He is approaching a right-hand corner while in fourth gear at 50 mph. He is going too fast to make it around the corner safely, so he starts braking until he drops the Passat's speed to about 25 mph. Frank sees on the tachometer that his engine revs are dropping too low, so he pushes in the clutch as he goes around the corner. As Frank thinks about accelerating, he realizes that the Passat is still in fourth gear, which isn't suitable for strong acceleration at such slow speeds. So he moves the shifter from fourth to second gear, lets out the clutch and motors away.

The problem with Frank's technique is that when he lets out the clutch, it is not going to be a smooth shift. The Passat is going to buck a little. Why? Because when Frank goes around the corner with the clutch pushed in, the engine revs drop to idle speed. When he releases the clutch, the mechanical locking effect between the engine and the front wheels (the wheels powered by a Passat) forces the engine revs to match the rotational speed of the rear wheels. In this case, 25 mph in second gear would mean the engine has to be at roughly 2,600 rpm. When Frank lets out the clutch after moving the shifter to second gear, his car's engine must instantly go from idle to 2,600 rpm. This sudden change causes the car to buck, as well as causing undue wear-and-tear on the clutch, transmission and engine mounts.

The simple solution for Frank would be to give the car some throttle before he lets out the clutch. Specifically, he should raise the engine speed to 2,600 rpm. This way, the engine speed is equalized to the wheel speed for second gear, making the shift much smoother. For racecar drivers, however, this technique is too slow and also means that when the car is going around the corner, the clutch is pushed in, a serious no-no in a racecar.

The racer's answer is the heel-and-toe downshift. The technique combines braking and downshifting at the same time. Using our example again, if Frank used a heel-and-toe downshift, he would have downshifted while he was braking for the corner. This way, he would have had power while he was going around the corner and he could have quickly applied more throttle once he exited the corner. These are critical elements to a racecar driver, but they can also be useful to any driver on the street.

Here is a step-by-step guide on how to heel-and-toe downshift. It will explain how to shift from fourth gear to third gear, though the technique will work for any downshift.


Begin braking for the corner with your right foot. The location of the pedals and the size of your foot will dictate where you position your foot on the pedal, but most likely it should be canted a little to the right, closer to the throttle pedal.


Push in the clutch with your left foot.


This is the hard part. With your right foot still applying pressure to the brakes, roll the outside edge of your foot outward and downward to touch the throttle pedal. The pedal design on some cars makes this easier to do than on others. Use the outside of your right foot to blip the throttle. Blipping the throttle means temporarily raising the engine rpms to match the wheel speed. The exact amount of revs needed is dependent on a variety of factors, but it is usually between 1,000 rpm to 2,000 rpm more than the current engine rpm for a one-gear downshift.


Move the shifter to third gear.


Release the clutch with your left foot.
As you can see, "heel-and-toe" is a misnomer. It actually involves the ball of your foot and the side of your foot. We'll be the first to tell you that heel-and-toe downshifts aren't easy. We've found that a good way to practice is to just sit in your car in your garage and pretend you are doing a heel-and-toe downshift with the engine off. Keep repeating the steps until you are familiar with the process. Once you are ready, try it out for real. Most likely, your early attempts will be botched. Keep trying, though. Practice each step slowly and then work your way to making them all one, fluid motion. Skilled drivers can execute a heel-and-toe downshift in less than one second.

The trickiest part is getting the correct amount of rpms to match the new gear. If you blip the throttle too much, the engine has too much speed compared to the wheels and is forced to drop down to the wheel speed when you let out the clutch. If you don't blip the throttle enough, the engine rpms are forced to rise up. Either way, you know you didn't do it right as the car will jerk a little.

You'll also know it when you did it right. A proper heel-and-toe downshift is so smooth and so satisfying that, once done correctly, you'll find yourself using the technique all the time. The great thing is that you don't have to be a racecar driver or be on a racetrack to use it. Additionally, using the heel-and-toe downshift technique on the street can improve safety. In certain emergency situations, you might be required to brake heavily and then accelerate quickly. By heel-and-toe downshifting, your car will be in the best gear to achieve maximum acceleration.

So, let's recap. It's fun to do. It improves driving safety. It reduces the amount of powertrain wear on your car. Other than the amount of time it takes to learn, there is no downside. What more could you want?


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da_joint
post Oct 19 2005, 11:41 AM
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QUOTE (florin83)
Da_joint, oricum la noi nu sunt valabile..

n-am vazut filmele, am dat cu presupusu smile.gif

Asta crezi tu.... :


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florin83
post Oct 19 2005, 11:50 AM
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pai asa si e.. nu o sa intrii cu aceiasi viteza intr-o curba cu un rwd,fwd si awd, nu o sa accelerezi in curba la fel, etc...
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da_joint
post Oct 19 2005, 12:06 PM
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am zis eu asta?
Logic ca difera....


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florin83
post Oct 19 2005, 01:31 PM
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QUOTE (florin83)
Da_joint, oricum la noi nu sunt valabile..


QUOTE (da_joint)
Asta crezi tu.... :


ce intelegi din asta? tongue.gif
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SUPERBEC
post Oct 19 2005, 05:39 PM
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avand in vedere ca nu ma duc la CNR si nici macar la VTM prefer sa fac frana de motor violenta si sa nu folosesc deloc heal&toe tongue.gif
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SUPERBEC
post Oct 19 2005, 06:05 PM
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pe asfalt nu te invarti, doar iti scartie un pic spatele biggrin.gif si in curba pleaca in drift un pic , e super tare biggrin.gif
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Zom
post Oct 19 2005, 07:51 PM
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am incercat, dar oricat m-as stradui, nu imi ajunge talpala ambele pedale, oricat as roti sau invarti piciorul sad.gif mi-ar trebui o talpa dubla ca latime. as putea sa imi fac niste talpici pe care sa le fixez pe incaltari atunci cand urc in masina. altfel...nu am nici o sansa sad.gif(
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SUPERBEC
post Oct 19 2005, 09:16 PM
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cum sa nu ajunga, calci frana cu calcaiul si acceleratia cu degetu mare biggrin.gif

acum chiar crezi ca ai nevoie sa faci asa ceva?

oricum la raliu se foloseste din cu totul alt motiv frana varf calcai... ca sa se mentina presiunea in turbo tongue.gif


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Zom
post Oct 19 2005, 09:49 PM
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QUOTE (SUPERBEC)
cum sa nu ajunga, calci frana cu calcaiul si acceleratia cu degetu mare biggrin.gif

acum chiar crezi ca ai nevoie sa faci asa ceva?

oricum la raliu se foloseste din cu totul alt motiv frana varf calcai... ca sa se mentina presiunea in turbo tongue.gif



mai, nu am zis ca nu am inteles cum se face. am zis ca imi este imposibil avand in vedere dimensiunile talpii/pedalelor mele si dispozitia pedalelor in cauza. in mod sigur la matiz nu as fi avut probleme. nici macar la e90, la care le-am mai calcat pe amandoua (n.b. pedalele) by mistake.
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316i
post Oct 19 2005, 11:26 PM
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mai simplu e sa bagi dintr-a 3-a a 2-a. Ca din a 2-a in a 1-a intra mai greu.
E senzatie si cand intri in curba de 90 de grade cu a 3-a la 2000rpm si la intrarea in curba dai a 2-a+blana. :unibrow:
Dar intrebarea mea este: prin frana de motor violenta, care piese sunt cele mai supuse uzurii? Ma refer la motor.


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Luk
post Oct 28 2005, 07:13 AM
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eu am avut o experienta simpla, pe cand aveam ursuletz: am intrat prea tare intr-o curba, pe jos era ceva noroi amestecat cu apa sia mi-a "fugit" spatele. Am luat piciorul de pe acceleratie si am virat invers, iar masina s-a asezat cuminte la loc si apoi am accelerat din nou. No problem there.
Faza am patit-o si alta data, atunci am derapat un pic mai spectaculos, am ajuns aproape de-a latul soselei, iar ala care era parcat pe interior cand m-a vazut a incremenit. Dar si de data asta am reusit aceeasi manevra si m-am redresat. Ce sa spun, senzatia e super, mie mi-a placut la nebunie, chiar daca nu am facut-o intentionat. biggrin.gif


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mgrx
post Oct 28 2005, 05:11 PM
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In Piatza Victoriei, cind vii dinspre Romana si faci dreapta imediat dupa palat, ca sa iesi inspre Paris / Dorobanti, etc, e o curba super, cu garduletz, care se ia (curba, nu gardu) destul de incet. E super cind e ud pe jos, arunci un pic fundul, doar din acceleratie, si te uiti apoi la gardienii inmarmuriti smile.gif)

Chiar daca intri prea tare, sansele sunt sa iesi de pe drum pe spatiul verde, evident, dupa ce saluti mai intii garduletzul smile.gif

E super. Cind aveam ursu zi de zi in drum spre serviciu chinuiam rotile in curba aia. Cu caruta de cinci nici nu mi-a trecut prin cap sa incerc.

Alta "Tehnica" am experimentat la iesirea de pe DN1 inspre Pacea, sau ma rog, un drum paralel cu ala... Am zis sa "pilotez" si eu un pic ursu si m-am trezit ca era nisip pe jos. Ma duceam fix intr-un copac, dar nu stiu ce naiba am facut si am evitat copacul smile.gif

Intr-un final, ursu saracu... a ajuns intr-o duba, prin bulgaria, cam cu 80km/h... Dar proprietarul nu a avut nici o zgirietura. Solida rau masina.
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