Debate: downshifting vs. braking
- Thread starter shaitsta
- Start date
I usually downshift... it just depends on what gear Im in on how many times I downshift. If Im in 6th.. then I downshift to 5th... apply some brake.. then to 3rd and apply even more brake. Very rarely do I downshift into 2nd. Only time I do is when Im stopping but the light turns green and I can go or theres no traffic.
6
60181
same here....I put her in Nuetral and coast and then use the brakes, as I approach the light or stopped/slowed cars, I'll prese the clutch and select my gear in prep for continuing on...tyically 2nd or 3rd depending on speed of course. brakes are best for stopping IMO.
not me.....brakes are a lot easier to modulate when slowing vs engine braking....if you hit a slick spot, the engine rpms will cause slippage on the wheels. even if you're consistently smooth and safe, there will eventually be one time where you're not or the road is too icy. whatever works though.
Silver Ecstasy
Member
- :
- 11 MS3 Sport
It's a manual car, you're going to use the clutch regardless.
If you need to use the clutch to slow the car down by downshifting, while using the brakes, then do what you gotta do. Even auto transmissions downshift while you're slowing down. And the side effect felt is you can feel the lower gears being engaged as you press the brake. So I try to mimic it in a similar fashion to make the car work seamlessly with brakes and trans. When I had my GTO, it even mentioned that you should NOT ONLY use the brakes to slow the car down but the trans as well. Otherwise the brakes would prematurely overheat and lead to failure from the weight of the vehicle and the strain of putting the brakes to work too constantly.
Especially with it getting icier and snowier, it's not practical or possible to rev match and downshift a heavy distance between i'm going to actually turn. With traffic and whatnot, it doesn't always work out.
So what i'll do is, use the brakes to slow the car down, and downshift through a gear or two using the clutch to engage those lower gears. Then either downshift if needed during the slow/easy turn, or try to take the turn through the gear i'm in.
I typically use 6th gear a lot while i'm cruising. When I am approaching my normal right hander, i'll downshift+rev match (or double clutch it) from 6th to 4th, then once more to 3rd and use 3rd throughout the turn. With the weather getting nastier, I try to slow down more so and creep through that normal right hander in 3rd with very low power (rpms are sorta low in that gear during that turn). Or if I think the conditions will allow, i'll downshift into 2nd as i'm entering the turn if I know I need the power.
If you need to use the clutch to slow the car down by downshifting, while using the brakes, then do what you gotta do. Even auto transmissions downshift while you're slowing down. And the side effect felt is you can feel the lower gears being engaged as you press the brake. So I try to mimic it in a similar fashion to make the car work seamlessly with brakes and trans. When I had my GTO, it even mentioned that you should NOT ONLY use the brakes to slow the car down but the trans as well. Otherwise the brakes would prematurely overheat and lead to failure from the weight of the vehicle and the strain of putting the brakes to work too constantly.
Especially with it getting icier and snowier, it's not practical or possible to rev match and downshift a heavy distance between i'm going to actually turn. With traffic and whatnot, it doesn't always work out.
So what i'll do is, use the brakes to slow the car down, and downshift through a gear or two using the clutch to engage those lower gears. Then either downshift if needed during the slow/easy turn, or try to take the turn through the gear i'm in.
I typically use 6th gear a lot while i'm cruising. When I am approaching my normal right hander, i'll downshift+rev match (or double clutch it) from 6th to 4th, then once more to 3rd and use 3rd throughout the turn. With the weather getting nastier, I try to slow down more so and creep through that normal right hander in 3rd with very low power (rpms are sorta low in that gear during that turn). Or if I think the conditions will allow, i'll downshift into 2nd as i'm entering the turn if I know I need the power.
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happy and angry
Member
I am about to drop some SCIENCE on your ass. Actually, on this entire thread, because some of the stuff being said here is a bit off (and I've been away from the forums for a while and sort of want to bust out SCIENCE).
In a manual, when you step off the throttle, the vehicle stays in gear and the fuel injectors shut off. No fuel is dumped into the cylinder on the compression stroke of the motor. The vehicle will slow down via engine or compression braking. Momentum drives you forward, some limited mechanical resistance (read: friction) helps slow you down, but the biggest force drawing energy out of the system (for all intents and purposes, let's think of the system as engine, transmission and drive wheels, connected and in gear) is the compression stroke of the motor.
In neutral, you simply have mechanical friction slowing down your car. In gear, you have compression helping out. Because the engine is still being turned by the momentum of the vehicle moving forward, the intake and compression cycles are still happening, but without any combustion. Air is pulled in, compressed, blown out, rinse and repeat. On a 2.0L 4 cyl motor with a 10:1 compression ratio (for example), you're taking 0.5 liters of air and compressing it down to 1/10th the size in each cylinder every two engine rotations, and that takes energy. Quite a lot, really, because you're turning the motor thousands of times a minute (at higher RPM's engine braking happens faster because the motor turns faster and compresses air at a faster rate). Compressing air takes a lot of energy, and this is the primary source of you slowing down when in gear and off throttle.
Now, is bad for the car? No. No it's not. Why would it be? Your drivetrain is designed to accelerate (from a stop, no less) a 3,100 pound vehicle up to 60 mph in about 6 seconds, and you think it can't take a similar (but much smaller) stress slowing down from 60 to (near) 0 in probably 20 or 25? Please. If you're rev-matching your shifts properly, you are doing no more stress to the drivetrain than normal opperation of the vehicle, no more stress than lightly applying the brakes when in gear. No one gets all worked up about stepping on the brakes in 6th on the highway and staying in gear, upset about the stress they are putting on their transmission. Why would they? Plus, the new smart automatics like in the Evo and the GT-R blip throttle and downshift for you as you slow down, or even as you coast, if your speed drops enough to trigger a downshift. Hell, even new smart manuals like in the new 350Z have a feature that rev-matches your downshifts for you, whether or not you are accelerating or slowing down.
What IS bad for the car is downshifting stupidly. Engine braking is NOT when you down shift by slowly easing out on the clutch, riding the friction point and using clutch wear to bleed momentum energy from the system and thus slow down. This wears the clutch and is dumb and bad and wrong, and anyone on here that does this should stop immediately.
If you're going to downshift, rev-match. An example: Let's say you're in 4th gear doing 60 km/h and want to go into 3rd to slow down. In 4th gear you are cruising at 2000 rpm. In 3rd at 60 km/h you know you're going to be at 3000 rpm. Clutch in. Spike the throttle until the engine is turning 3000 rpm (it doesn't take much gas, either). Clutch out. Don't even need to do it slowly, just smoothly, if you hit the rpm right. It'll just go smoothly into gear with nary a jerk or hesitation. From there, let off the gas, and let the engine brake for you.
Advantages of engine braking: you use less (read: zero) fuel when slowing down, where as when you clutch in idle throttle takes over to keep the engine turning. You are in gear and can accelerate out of a situation/react to things on the road faster, if you need to. You can better control speed in traffic situations.
I can't heel-toe this car because the gas pedal is too far back from the level of the brake pedal and my legs are too long, so when I'm slowing down (and you usually know when you're going to have to slow down far in advance) I anticipate having to slow down and downshift. I coast if I can, brake if I can't, and come of the brakes to spike the throttle to downshift before getting back on the brakes. The ride stays really smooth, no jerk going into the next gear and I'm smooth on/smooth off the brakes. I can do entire offramps without braking, I deal with rush hour highway traffic with very little use of the brakes, I downshift for going downhill to regulate speed, etc etc etc. I'm always in the right gear, and rarely actually have to use the brakes in my car except when coming to a complete stop.
tiagotiago
Member
- :
- 2008.5 Mazdaspeed 3
I'll use my brakes in 95% of the situations while doing heel-toe downshifts, I'll only do a bit of engine braking/coasting if I'm coming up to a red light I'm certain will change; that way I'll be in the right gear when the lights go green, and more importantly I probably never touched the brakes, so I didn't loose as much momentum and won't have to accelerate as hard.
I'm guessing engine braking from high speeds was probably a workaround done to keep from cooking the brakes in mountain roads in which brakes would be abused. It would make sense to do that in cars with marginal brakes but I don't see that happening in the ms3, tough if I was in a mountain road and the pedal started to go soft, I'd probably engine break a bit to let the brakes cool down.
In a racetrack, in slippery conditions, or just trying to be as absolutely smooth as possible, you can't just downshift take the clutch out and let the engine break, it upsets the car's attitude too much, so you need gentle applications of the brakes while rev-matching to keep the car nice, stable and predictable.
I'm guessing engine braking from high speeds was probably a workaround done to keep from cooking the brakes in mountain roads in which brakes would be abused. It would make sense to do that in cars with marginal brakes but I don't see that happening in the ms3, tough if I was in a mountain road and the pedal started to go soft, I'd probably engine break a bit to let the brakes cool down.
In a racetrack, in slippery conditions, or just trying to be as absolutely smooth as possible, you can't just downshift take the clutch out and let the engine break, it upsets the car's attitude too much, so you need gentle applications of the brakes while rev-matching to keep the car nice, stable and predictable.
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happy and angry
Member
What? No. It is not a "workaround" for anything, it is how the internal combustion engine works with a transmission. It is not a goal, it is simply a product of how cars work.
No it doesn't. No more than brakes do, anyway. Less, really, because there isn't a lot of "braking" force being generated through compression braking. Hell, on a racetrack people engine brake all the time. You brake in gear or hold gears to regulate speed all the time through corners, and if you are in gear and not on the throttle (this means even when actually using the brakes), engine braking is happening. And on slippery roads, you are not avoiding being in gear because engine braking "upsets the car's attitude", you are doing it to limit the resistive forces on the free turning of your wheels so you can maintain the ability to steer.
In my post above I mention what engine braking isn't and it sounds like that's what you are talking about, but no one who drives a manual car should ever, ever be doing that to their clutch. You wouldn't be doing that, would you? Surely not.
That's what my pappy taught me. Downshift at the right time, but use the brakes what they're there for. Heel/Toe for the advanced class.
happy and angry
Member
I've tried, but I'm not very smooth with it. When I try to rotate the outside edge of my foot towards the throttle pedal I end up pushing in on the brake pedal more and it makes for a jerky ride. I'm rarely in a situation where I need to trail brake and downshift heading into a corner, and there is always enough space for me to anticipate downshifting in traffic so it's not much of a problem for me. If I start tracking the car more I might cut an inch or two of travel out of the brake pedal and re-weld it back together with the two pedals more level so I can have finer toe control on the brake.
Not so much science as sound engineering (speaking as an engineer)
AMEN.
mazdaspeedster3
Member
- :
- Mazdaspeed3. 2008
This is a no brainer and is probably already posted on this thread. Down shifting saves gas as it cuts fuel to the motor. Also, and probably the most important is it is safer to be in gear than not. There are a lot more movements to put the car in gear and go to get out of the way of an accident. If you use the engine and brakes in sequence you will always be prepared for the unknown and save gas... Win-Win!
Good tip, thank you. With size 12-13 shoes, I do have heel/toe troubles.
tiagotiago
Member
- :
- 2008.5 Mazdaspeed 3
I agree with your first post in this thread and I agree with that statement, nobody should do that to their cars, but ideally nobody should do a lot of s*** that they happen to do in the real world. Ideally all countries would have licence training and exams like the ones they have in Finland, and roads built like the autobahn, but in reality you have people in 3rd world countries that climb into a pile of junk they call a car and try to learn on the fly how to drive on pothole laden roads, possibly after having a few drinks and without bothering to go get a licence. The real world is so very far away from the ideal...
happy and angry
Member
Well now you know better, and you can take this knowledge out into the real world and apply it to your driving and stop riding out on the clutch when you downshift.