how can downshift increase speed?

Question

ive heard in a standard car you can downshift inorder to increase speed. i understand how in a lower speed you can accelerate fast, but if you downshift for example from 5th to 4th gear, wont the car slow down and defeat the purpose of accelerating. i need help understanding

Answer 1

If you downshift and hit the gas, it'll increase speed - otherwise it slows the car down (the motor speeds up, though as it tries to compensate for the higher gear ratio)

Answer 2

Imagine that you want to quickly speed up but you are already in a high gear. If you downshift a gear, it will be easier to speed up when you step on the gas. Just like when riding a bicycle...it is easier to start off in a lower gear, then upshift to a higher gear so that you aren't peddling super fast and going nowhere. And once you are cruising if you want to speed up, you can shift down a bit and it is easier on your legs to speed up.

Acceleration has to do with the torque of the motor matching the proper gear. Ever try to start off in third or fourth gear? Almost impossible because the torque is not matching . But once the car gets moving, it is easy to get into third or fourth and still accelerate.

Have you ever driven an automatic and while going 30 or 40 or maybe even 70 then floor the gas? You'll notice that the transmission automatically downshifts...it's the same thing that you want to do when driving a stickshift.

Answer 3

It's all to do with acceleration. Use the analogy of a bicycle with gears, In a high gear, if you need to accelerate you have to push really hard on the peddles and an increase in speed comes slowly. But if you shift to a lower gear the effort required to increase speed is less, however you will be peddling faster. So it's a trade-off between a higher speed against greater engine (or crank) revolutions.

Answer 4

ok if you cruising at 60 mph, in 5th gear, your RPM could be around 2300 RPM. When you downshift to 4th at same speed (you have changed the engine RPM to wheel RPM ratio) the engine is now at 3700RPM. The engine can now accelerate quicker because the engine is in a passing gear.

Think of a mountain bike, your legs are the 'engine' and the gearbox is the transmission. The lower gears help you accelerate and/or climb. TRY THIS: Put the bike in 6th gear (or whatever is the highest) and try to accelerate from a standstill. Now put that same bike in 1st gear, it is easy to pedal because the engine (your legs) can spin faster than the wheel. (ie 3:1 ratio) Of course the ratio is an example and can vary by deferent bikes.

Answer 5

Downshifting in and of itself will not increase your overall speed. It will increase the speed of the engine (RPM's). This in turn can put the engine speed in a range where more horsepower is generated thereby increasing your ability to accelerate faster. This is easy to check out. While going highway speed (or a little under, I wouldn't want to advocate speeding.....=p ) and the transmission in 4th or 5th gear do a roll on acceleration. i.e. just mash the pedal down. Compare that with dropping the gear down 1 or 2 and mashing on the pedal, you will accelerate quicker.

Answer 6

downshifting dosent increase speed per se, it just allows your engine to run at higher RPM's...

At 55 in 5th gear, you can downshift to 4th (or 3rd with a fast car) and stomp on the gas at the same time - this will give you a much faster acceleration rate than if you stayed in 5th and just floored it that way.

My advice is to go out and try it both ways right now so you can appreciate the difference. :)

Answer 7

Two things: you understand that the torque is greater at the lower gear and thus you can accelerate more. Second, the wheels of the car will make fewer revolutions per single revolution of the engine when you downshift and thus you will have to upshift eventually to maintain the increased speed.

Answer 8

actually The speed will decrease as you down shift, but accelleration will increase. If you were going 50 mph in 5th gear. You come up on a car. if you stomped the pedal it would slowly increase speed, by downshifting to 4th, the rpms will increase and the ratio will let quicker accleration occur..

Answer 9

Picture yourself driving up a hill, changing back through the gears to maintain, or even increase speed, also true for exit speeds out of corners, being in the gear with the best rev range for quick acceleration from that speed, will see you back at top speed the quickest...

Answer 10

Maximum horsepower is attained at fairly high RPM. Downshifting allows the engine to run at the higher speed, and deliver the extra power. Drive a car over hills on cruise control, and notice the thing downshifting when going up a hill.