In film of an alleged Ferrari blazing through Paris, we have an exciting film indeed. Assuming the film is accurate, can anybody explain the gear shifting in the film? When the driver comes to a point were slowing down is necessary, we hear an apparent (sp?) gear-by-gear downshifting.
My Toyota owner’s manual says to downshift and let the engine slow me down when I’m going downhill. Is downshifting & letting the back-pressure (??) from the engine slow the car an acceptable practice for one who wants the transmission to last?
You don’t downshift to slow down. You downshift so you can accelerate out of the curve. That film is pretty old by the way. I think it was filmed in the seventies. I remember seeing it a long time ago.
He’s downshifting not as a means to slow the car. He’s doing it so once he gets off the brakes he’ll be in the right gear (matching his now slower speed) to accelerate out of the turn.
Going downhill you can have the car in a lower gear to use the engine compression to maintain a safe speed. Going down long hills using the brakes to keep your speed down can overheat them and cause them to fail. That’s a bit different than downshifting to slow yourself coming to a stop light, etc. Yes it’ll save wear and tear on the brakes, but it’ll increase wear and tear on your clutch and engine. Brakes are cheaper.
The bigger danger is to the engine if you do it incorrectly. The compression of the engine is generally enough to keep the car at an acceptable speed while, say, going down a hill. However, if you are driving at 90 mph and and downshift into second gear, you will likely blow the engine due to sudden, extreme RPM’s well above the redline. That is where the downshifting gear by gear comes into play. Each gear down is close enough to the one above it that downshifting speeds up the RPM’s up but not dangerously. You can shift down one by one and slow down using that technique.
As to why you would want to do that, I don’t know. They say that it means that you are always in control and using an appropriate gear in case you want to accelerate again at any time. They say it saves brakes as well. It tends to be more of a European thing. Someone with an expensive sports car probably loves to drive it and that gives them something to do.
Clutches are a lot more expensive than brake pads.
When you need to slow down, you should engage the clutch, put the car in neutral, and take your foot off the clutch. Then simply brake as if you were in an automatic. If you need to re-engage the engine after you have let it drop to idle, you can ‘blip’ the throttle to bring the engine RPM up to where it will be when the clutch is disengaged, to keep clutch wear down.
When you’re at a light, don’t keep the car in gear with your foot holding the clutch down. Put the car in neutral and release the clutch while you’re waiting.
ISTR that the car in that film was actually travelling at only about 40mph. The engine noises must be dubbed.
Anyway, it has always seemed to me better to put the strain on the brake pads, which are expected to wear out and hence cheap and easy to replace, rather than the transmission, gaskets etc., which are anything but. Engine-braking is good for moderating your speed, and something you immediately miss when you drive an automatic, but when you seriously want to slow down you’re better off using the brakes.
Downshifting via engine braking allows more control, espeically in slick conditions (provided that you don’t slamshift), and it prevents brake fade (the tendancy of brakes to become less effective as the pads and rotor/drum heats up). It does put more load on the engine, but for an engine that is well-maintained and in good repair it shouldn’t cause undue wear on bearings or pistons provided you don’t rev it up near the redline while doing this. The biggest problem (on a manual transmission) is actually clutch wear; since you’re shifting under load the clutch sees more torque than usual and will wear faster. On an automatic you’re going to get some transmission heating, but again, unless you’re carrying a heavy load or running the engine high it shouldn’t be a problem, although it probably will lead to more wear on transmission components.
A perfectly-executed* downshift places no wear on the clutch. Of course, it’s impossible to perfectly execute a downshift, but you can get pretty close if you’re good.
Even with a perfect driver, during everyday driving downshifting to slow down on level ground is rather pointless - unless you’re driving a diesel, the engine braking effect is fairly minimal. Only when you’re going down a hill does it become useful.
If you’re coming up on a stop sign or something (i.e. need to stop completely), there’s no reason to downshift to slow down. Just put your foot on the brakes, and disengage the clutch when the RPMS drop too low.
However, if you’re slowing down and not stopping completely (i.e. going from an 80 mph open highway to a 40 mph work zone, turning a sharp corner, etc.), you should downshift in order to keep the engine in the optimal RPM range. Downshifting sequentially can help here if you’re worried about over-revving the engine.
I’m amazed at how many people seem to be ignorant of that last paragraph.
Now, downshifting during racing is another story: every bit of braking helps, and so downshifting in order to take advantage of engine braking is crucial. Since engine braking is stronger at high RPM, you want to keep the RPM as close to the redline as you can when slowing down, which means downshifting one gear at a time.
And, as Shagnasty said, it’s fun, even when you’re not racing.
meaning rev-matched, though not necessarily double-clutched
Incidentally, that film is called Rendezvous and was made by French director Claude Lelouche, who may or may not have been driving the car. There’s been tons of speculation and rumors about the driver, and what car may have been used.
Some Physics students calculated his speeds and they estimated that at one point he reached 136 mph.info here.
Sorry, Sam, but I have to completely disagree with the advice above. At no time when the car is in motion should you have the transmission in neutral except (with a manual) as a transition to shifting into another gear. Driving around with the transmission in neutral means that the only control over the vehicle you have is via what sailors call “steerage weigh”, i.e. the residual inertial motion of your car. If you suddenly have a need to move out of the way or dodge a vehicle you may not have sufficient momentum to complete the maneuver.
What you should do when slowing down at a normal (flat) stop without using engine braking is to let the engine slow to near-idle RPM in the current gear, then engage the clutch and shift into second, holding the clutch in until you come to a stop, using the brakes when necessary. This allows the driver to immediately engage the engine by releasing the clutch but avoids lugging or loading the engine and transmission unnecessarily. Whether you then place the car in neutral, or place it in first and hold in the clutch is up to the driver; I frequently do the former on stoplights, but my motorcycle class advised the latter.
With regard to clutch wear versus brake wear: as a fairly aggressive driver (and one that drives in the mountains not infrequently) I use engine braking all the time, far more often than is really required. Despite that, I’m on my third set of pads (and second set of rotors, though that was most likely a bad service problem than standard w. & t.) but still with the original clutch at ~190k. I do tend to match engine revs and feather the clutch before shifting, which no doubt reduces engine and clutch wear, but with correct shifting technique clutch wear shouldn’t be a major maintanence issue; most premature clutch replacement seems to be due to drivers either shifting improperly or resting their foot on the clutch petal while the the car is moving (thus allowing clutch slippage).
Okay, I’m going to misspell “brake.” I apologize in advance.
'78 is what I’m reading. And as I said, assuming it is real…
Okay, I run through the gears as I slow down to be in the gear I want should the gas pedal become the thing to push; however, I keep the clutch in. In this video, the gears are clearly being engaged. Is engaging the gears but still using the brake a better way to do this?
Don’t tempt me. The car comes with a new racing clutch when I destroy the factory clutch. Because I lucked into an expert witness job in court, I may have a windfall to get an improved suspension kit. (Sweet.) I’m eager for a clutch I can abuse. ::whistles innocently::
Okay, this theme is confusing me. Every time “my car” and “brakes” have appeared in the same sentence, I’ve ended up having to borrow money from family to pay my rent because break jobs are so effin’ expensive. Where are you guys getting your brakes done?
I’m not suggesting coasting in neutral from cruise. I guess I wasn’t very clear. I put in the clutch, apply the brake, slow down, and then as I’m coming to a stop at a light I’ll just pop the car into neutral and brake to a halt. I do this mainly because it keeps me in the habit of getting my foot off the clutch. If I don’t, often I’ll find myself sitting at the light in first gear with the clutch depressed, and there’s no need for that.
I used to downshift all the time, and double-clutch when I could when shifting gears. It just gets to be too much work, and downshifting is harder on the drivetrain than just braking to a stop. If I’m driving aggressively, however, I’ll downshift all the time to keep the car under positive acceleration and in the right RPM range for the acceleration I’m about to do coming out of a corner. I guess it all depends on the conditions and what you’re doing. In regulat stop-and-go traffic, just use the brakes.
Here’s the movie, if you want to see it. I was holding my breath just watching it. My God. He almost clipped a pedestrian at one point. I lost count of how many red lights he ran. That was nuts. Awesome, but nuts.
There can be a bigger danger to the driver if not done correctly.
Old farm truck.
Fairly steep curvy downhill run, ending up in the river if you couldn’t stay on the road.
Had heard of and aquainted with the principle of double-clutching but had never practiced or done it previously.
Started down hill at road speed without realizing so at first.
In a few fast and furious moments I executed the exercise twice from third to second, then second to first, ending safely at the foot if the hill at the ferry stop sign!
It is my understanding that double clutching reduces wear and tear on the clutch.
To answer the OP, the driver in the film is not downshifting to slow the car. What he is doing, at least some of the time, is heel-toe braking, which I describe in detail in post #17 of this thread. However, most of the time he seems to be blipping the throttle repeatedly (which the OP took for downshifting) when he should only have to do it once at each turn. I don’t quite understand why, unless a) the Ferrari’s idle is set too low, and engine might conk out if he let the revs drop too far (unlikely, I think) or b) it’s a nervous habit, or c) he thinks it sounds cool (which it sort of does).
I have a few doubts about the film, especially the soundtrack. It seems to me that there’s tire squeal in quite a few places where there shouldn’t be.
Now that that’s out of the way, on the subject of downshifting to slow the car, Click and Clack (in Cecil’s article) had it right: brakes are for slowing the car, and the transmission and clutch are for transferring power from the engine to the wheels. Period.
No matter how cool it makes you feel, using the engine to slow the car is pointless and stupid, EXCEPT for the long downhill situation your manual talks about. If you were heading down a mountain and had your foot on the brake (even lightly) for a several minutes nonstop, you could boil the brake fluid or wear the brake pads down to the metal. That would be a Bad Thing. So in that situation you should use a lower gear to maintain a safe speed without using the brakes.
Sorry, but I have to call bullshit on this. In my many years of watching racing, in the dozens of books I’ve read on racing, and in the 6+ years I’ve been driving on race tracks myself (see the other thread), I’ve never heard anyone who knew anything about racing say anything even close to this. Race cars have really good brakes, and race drivers NEVER use the engine to slow the car.
Now, many race cars (e.g. most open-wheel cars) have sequential gearboxes, like motorcycles, which means that when they go from a high-speed straight into a slow corner the driver has to drop through several gears to get to the right one for the corner. But he’s doing that with the clutch in, and not engaging and disengaging the clutch with every gear. That would only increase lap times and wear on the car, neither of which he wants.
The television coverage for the V8 Supercar series in Australia is quite good. They normally have a camera in a couple of cars pointed at the drivers feet. The drivers certainly engage each gear as they downshift and brake into a corner.
There is at least one V8 driver (Greg Murphy) who uses his left foot on the brakes and doesn’t bother with the clutch at all while downshifting, obviously the gear is engaged with each shift, and he is one of the faster drivers.
I think he is downshifting one gear at a time, hence the several blips of the throttle (eg. he goes from 4th to 3rd and then to 2nd instead of going directly from 4th to 2nd).
Also keep in mind that this Ferrari has probably a non-synchronised gearbox, so heel-and-toe is the only way to downshift.
Meh. In these days of hydraulically-linked clutches, it doesn’t really matter (unless you’re prone to slipping off the clutch petal accidentially). Nonetheless, the point is taken; engine braking is unnecessary and at least to some extent counterproductive in terms of w. & t. for normal traffic conditions.
I vote for Option C (although I think it sounds more obnoxious than cool). It is an impressive, Frankenheimer-influenced film, though. I love those low-angle POV shots, though he needs a few four wheel drifts to get the proper effect.
I don’t follow car racing but what I’ve seen of WRC and Grand Prix-style racing indicates that engine braking is used extensively; one reason (I suspect) is that it prevents the parasitic loss of acceleration-on-demand that you can do with engine braking by having the transmission continuously engaged. This is a real issue when dealing with rapid maneuvers, although this bears as much relationship to normal driving as lion-taming does to owning a housecat.
Cecil has it right; the people who do it do so primarily for fun; the excitement, however transitory, of driving a car to its (percieved) limits of ability. And when you want to put an Audi S8 into a four wheel drift (and whom among us does not do so on a daily basis) the ability to use engine braking to dynamic stability is crucial.
Okay…it makes the trip to the druggists far more exciting than it ought be. If Og had meant us all to drive Tercels, he wouldn’t have invented the WRX STi.
I was taught that at a stop light one should engage the clutch and keep the car in gear. The reason for this is that if one is rear-ended, one will stall out rather than be pushed into the intersection.
