Is engine breaking a sin??

[Adam]

Hey guys,

Sorry! This topic should have been spelled "engine braking"

I've read in the past that downshifting and using the gears to help brake the car is bad for things in general.

I'm not at all worried about any shortening it may have on the lifespan of the drivetrain, but I'm curious to know what the rest of the members think.

I know that nearly all of us do it... What are your thoughts about it?

AC

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Adam Chaplin - 1976 911S Coupe

[This message has been edited by Adam Chaplin (edited 06-07-2001).]

[campbellcj]

In terms of smooth performance driving, most folks consider it preferable to do at least most of your slowing-down with the brakes, prior to downshifting. Even with proper heel-and-toe rev matching, the downshift upsets the car by sudden weight transfer and decreasing rear traction.

Now if you're talking about going down a long, steep grade and trying to limit your speed, then by all means select a lower gear to 'engine brake' as opposed to riding your brakes for 15 miles and potentially cooking the pads and boiling the fluid!

[pwd72s]

Engine braking is GREAT! Keep it up! You may experience the thrill of a 5-2 shift some day, and your mechanic will love you for it!

[Jack Olsen]

Calling it 'engine breaking' might be more correct than you know -- or at least 'transaxle breaking.'

It depends on what you mean, I guess, but if you mean downshifting to rapidly slow the car, then I would say it's bad. The gears in a transaxle are all designed to propel the car forward, not to decellerate. The 915 is such a problematic link in the Porsche drivetrain chain that I don't think you want to do any high intensity braking with it at all.

If you mean slowing down for a turn, under normal street driving conditions, and going through the gears more gradually (essentially matching revs at progressively lower speeds), then I don't imagine it will do as much damage. Chris is probably right about long inclines -- better to let the engine provide some inertial drag than to cook your brakes. But it's got to be a long incline -- Porsche brakes are pretty resilient.

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Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

[This message has been edited by JackOlsen (edited 06-07-2001).]

[Adam]

I have to say that I only use the gears to brake at slow-ish city speeds. I don't ever use the car for track work and I certainly don't go howling around corners with the poor thing dragging in 2nd @ 5k rpm.

Normal city driving, tho, and I love blipping the throttle and double-clutching down to the next gear as I approach a set of traffic lights. As I said, I'm sure we all do it, some, just more than others.

AC

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Adam Chaplin - 1976 911S Coupe

[pbs911]

Let's see. . . brake pads $50.00. Valve job and potential pistons and cylinders $5,000.00. I think I'll brake with the brakes and keep revs on teh downshift within the comfort of a smooth heel to toe.
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Paul
78SC Targa

[Clark Griswald]

I used to like to do this because it made me feel like I was driving the car hard. I liked to hear it rev. Then I learned that it is a poor driving technique that is not used in performance driving.

at its worst you are wearing the clutch, stressing the drivetrain, or locking the rear end.

Do you like to rev the engine and dump the clutch at stoplights too? That has about the same effect on the drivetrain.

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Chuck Moreland - '86 Cab, '77 Targa, Family Truckster

[Wayne 962]

For going down hills, it's perfectly fine - even preferred! For coming to a rapid stop, anything that jerks the drivetrain around is bad. In fact, I have never heard of anyone using the engine to brake except for long stretches of hills. It would be hard on the drivetrain to do so...

-Wayne

[Adam]

Guys,

Despite the nature of my post, I don't actually drive like this.

I take it that people have a generally dark view on this style of driving. Generally, my car doesn't go beyond 4,000rpm.

Just curious as to others' position...

AC



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Adam Chaplin - 1976 911S Coupe

[Matt Holcomb]

Adam,

I'm going to confess to the board, something that you already know -- I'm a self-confessed engine-braker that loves the third to second downshift, although the rear tires have never chirped! And yes, I do know better!

However most of the time, if I know I'm to turn, I let the engine stay in the 4-5,500rpm bracket by keeping it in second.

Guys, is this just as bad as downshifting from third to second at high revs? I mean, it's just about keeping the engine within a band...

[Rufblackbird]

Downshifting? What's that?

I'm a firm believer in using my brakes to slow down. Absolutely NO chance of missing a shift...like from 5th to 2nd!

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Jeff
1976 911S

[Olivier 3.0]

hum,hum... I don't understand the point...
Your car is designed to slow down by braking AND downshifting...
The only thing you have to do to facilitate this downshifting is what you call "heel to toe", in order to synchronize your gearbox and the engine, to avoid mass transfert and microblocking...
You know that in France, we do not like automatic cars (about 5% of the cars) and are used to manual shifting... So, we don't wonder about this kind of issue... maybe the difference is there.

Adam, you don't go beyond 4000 RPM; how can you do? I only appreciate my car beyond this limit :-)! and those cars are made for it...

cheers

[cds72911]

Obvoiusly not a popular reply, but in racing it is a "technique".

In rally racing, at least, it is a perfectly acceptable way to bleed off speed before entering a corner, so that you are in the correct gear to accelerate out of it. Perhaps not the smartest thing to do in a 915 gearbox Porsche, but it is a valid driving technique.

Charlie

[KTL]

As long as you match revs closely, I don't think it really harms the engine. That is, not anymore than autocrossing. Downshifting and bringing up the revs to 4500 is not really much different than approaching a corner at high revs, lifting and braking before you get back in the throttle to take the corner. I'm sure there's a little more wear on the engine. Like Jack said, the motor's purpose is to accelerate the car.

If you can do it smoothly, the result is much more effective than downshifting after braking. I find it easier to match revs at higher rpms than lower rpms. I tend to overrev and lunge the car a little when trying to match down low. That's definitely not good for the drivetrain.


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Kevin
87 Carrera coupe

[Planter91C2]

i agree with olivier, downshifting while slowing down is correct. don't automatic transmissions downshift themselves. i don't think the original poster meant to ask if an abusive or harsh downshift is good. you just want to slightly mimic the action of an automatic, of course shifting a little later

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Daryl 964 Targa

[9XI]

I don't get this thread. Say you're on a freeway, cruising in fifth at 70 mph. You approach the offramp and brake (or shift into fourth and off throttle for a bit) down to 50 to go through the turn marked 35 . BEFORE the turn you shift into 3rd matching engine speed.

The extra revs allow you to balance the car with your right foot throughout the turn. You exit the corner on the throttle in the right gear.

How else would you do it? I am not being sarcastic, but would you exit the turn and then try to shift down (very awkward)? Would you shift during the corner (bad idea!)? Given the choices, shifting before the corner is the appropriate move, isn't it?

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1969 911S Targa
1999 Eurovan Camper

[KTL]

Shifting before the corner is the only way to go for spirited driving. If you don't change down before the turn, you'll either be out of the power band or upset the balance of the car because you lifted off the throttle to downshift during the turn. As all know, in most cars the lift to shift is not that big of a deal. If you're entering a higher speed turn in your 911 and do the lift to shift upon turning, you may be in for a little crazy ride.

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Kevin
87 Carrera coupe

[Pillow]

Lets say you are going to a stop light/sign form 60-0. I let the engine slow the car in 5th and then place the car in neutral (let off the clutch unless you like to buy throw-out bearings) and drift/brake into the stop. Maybe a little enigne braking here but not much.

Going into a turn I usually do a 5 to 3 and then if need be a 3 to 2 (I do not like to go 5 to 2). Using the brakes before the shift and a little afterwards and then le the engine brake if it need be... Then hammer it though the turn! No lifting or shifting during a sharp turn otherwise it could get hairy.

Engine braking is not a bad thing unless you are hammering the poor girl to redline in your downshifts. Smooooooth baby, smooth. Also never "row" your gears down when coming to a stop or know you need less gearing in advance.

AC man, the Porsche LIVES above 4 grand!!! Go ahead and listen to her sing a little this weekend



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Adrian Pillow
1979 911 SC
1966 VW Microbus
PCA - Peachstate Region

[Rufblackbird]

Hmm...didn't know we were talking about downshifting on the track. On the track, well, it's a must, and you must do it gently, like others have said. If I was going off an offramp and needed to slow down I'd shift into neutral, slow a bit down with the brakes, hit the turn at a moderate speed, and once I get out I shift into whatever gear is suitable for the speed that I'm going. I guess I'm not THAT spirited of a driver?

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Jeff
1976 911S

[sander]

I think we're all mixing up 4 crucial factors here:
a) straight line braking
b) braking and turning
c) driving on the street
d) driving on the track

When someone says "engine-braking" I generally think of what the original post was probably referring to - using the transmission to help slow the car down in a straight line, on or off the track. I think that's usually a bad idea unless you really like to abuse your p-car (or long downhills, as Wayne mentioned.)

But when you heel/toe, the purpose isn't so much to slow the car down, as it is to match the revs so you're in the proper gear for the apex and track out points (again, as previously mentioned.) So I don't think Heel/Toe is the "performance technique" equivalent of engine-braking. When you do it right, you shouldn't even feel the downshift.

I think I'm just repeating what's already been said. Just trying to make the distinctions clear...

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'71 911E with Webers
Golden Gate Region PCA
http://www.geocities.com/edrecinto/