Is the goal of shifting to maximize horsepower or torque? Everyone seems to disagree...

You only get maximum horsepower and torque in ratios close to 1:1, although some of it depends on the powerband. Lower ratios increase torque at the cost of speed and higher ones increase speed at the cost of torque. Not that hard to wrap your head around

it depends on how and why you're shifting.
shifting up on the highway keeps the revs low to have maximum fuel efficiency. shifting down gives better acceleration for overtaking.
on a racetrack? shift up because you're redlining it and want to go faster. shift down because you're slowing down and want to keep revs high.

But for any given ground speed, to maximize acceleration, torque (not horsepower) should be maximized?

You can't have HP without torque. More torque will get you up to speed faster, but that also gives you more HP as a result.

If you want to read a lot of technical stuff this could be of value possibly
epi-eng.com/piston_engine_technology/power_and_torque.htm

If you have a shit final drive your tranny gearing aint going to mean shit. If you trying to go fast you'd want a final drive below 4, if you want hella torque without any speed you'll want above 4

A High ratio final drive will have better acceleration, better towing and generally more torque available, but will have horrible MPGS and a lowered final speed.

A low ratio final drive will Have better MPGS a Higher Final speed, and may even be easier to live with for day to day driving.

>1st: 3.30:1
>2nd: 1.94:1
>3rd: 1.31:1
>4th: 1.03:1
>5th: 0.84:1
>Final: 3.65:1

This is my car How is final drive calculated?

This is true but if you want maximum torque you need more and shorter gears which means more shifting and time losses.

with the differential.

Both should be maximised idiot

Your final drive is a bit more torque, and acceleration oriented. Also deoends how much power your car is making. Shitty powered cars usually have higher ratios to compensate for the low torque.

How does that happen?

Final Drive is the ratio of your ring and pinion that comes out the transaxle in the case of FWD and the Differential in Some RWD cars.

Or a CVT

Your final drive is 3.65 to 1. This is a decent ratio, but a little more top speed/ fuel economy -oriented than you'd want for a track or drag car.

This game is a good one for learning to understand gear ratios and the relationship between hp/torque/powerband OP you should try it out

The goal of shifting is to allow your engine to operate in multiple different parts of its powerband at the same speed. Lower gears allow you to have more power available at the same speed, while higher gears allow you to go faster and get better fuel economy at the same speed.

Here's a related question: are CVTs universally hated by car enthusiasts because of an inherent flaw, or is it just that they are usually tuned to prioritize fuel economy over acceleration and sportiness.

But CVTs arent fun

Well they arent fun because they are like automatics and yes most of them are tuned for economy

In any gear you choose at redline you will get max hp and torque. Gears are designed at ratios where they seamlessly mesh when you shift so you dont have to rev up extravagantly high for the next gear to turn at normal speeds

Most of the ones on the market break easily, they're tuned for economy, they're also tuned to "fake shift" becuase idiots think something's wrong if they're not shifting, which in turn makes wears them out faster, and the belts are expensive to replace.

The only exception to this are E-Cvt's on hybrids, which are basically electric motors that are both used as motors and transmissions.

>In any gear you choose at redline you will get max hp and torque

Wrong, for most engines.

Example:
Say your engine redlines at 6500rpm, and makes near-peak torque between 3500 and 5500rpm. Since acceleration is determined by wheel torque, which is a function of engine torque, transmission ratio, and final drive, you want to keep your engine RPM between 3500rpm and 5500rpm when accelerating. Upshifting too early would put your engine below 3500rpm, dropping it out of its powerband and causing you to not accelerate as quickly. Upshifting too late will allow your engine to climb out of its powerband by exceeding 5500rpm, causing torque, and as a result acceleration, to drop off.

For best acceleration, you want to upshift at a point that will keep your engine in its powerband. In my example, you'd want to upshift as soon as the new gear would put you above 3500rpm.

Of course, this all assumes you're going for performance. If you want fuel economy, you want to be in the highest gear possible, and go as slow as you can without lugging your engine.

Redline is almost never where peak power occurs, and usually results in a shift that places you above the bottom of your torque curve, meaning you could have shifted earlier and accelerated harder.

You're essentially right but I would add that many performance vehicles have it redlined to where when you hit redline, and then shift into the next gear, that you'll fall perfectly where your power band is.

>implying any Veeky Forumstist can afford a real performance vehicle
Your $500 craigslist dorifto missile is not a performance vehicle, it's tuned for economy.

>Lets project my poverty on others.

Sport bikes are not tuned for economy its just a side effect of small displacement and being light as fuck.

Similarly my 540i falls back into the powerband when on the throttle.

NORMIE GET OUT

FOR MAXIMUM ACCELERATION

SHIFT AT A POINT WHERE THE NEXT GEAR IS STILL WELL WITHIN YOUR POWER BAND, BUT NOT REDLINING YOUR ENGINE

ANYTHING ANYONE ELSE SAYS IS FUCKING WRONG

First Gear Ratio (:1): 3.38
Second Gear Ratio (:1): 1.76
Third Gear Ratio (:1): 1.18
Fourth Gear Ratio (:1): 0.89
Fifth Gear Ratio (:1): 0.66
Reverse Ratio (:1): 3.17
Final Drive Axle Ratio (:1): 4.05

They're autotragics, they're unreliable and put in cars that are usually driven by women

>Five speed with double overdrive

Ja pierdole

While it is true you would have max acceleration at max torque, you still have to consider the extra leverage the lower gear gets you. So reving up to redline would still be faster since you would get more wheel torque between 5500 and 6500 compared to 3500-5500 in the next gear

To maximize acceleration, both torque and horsepower should be maximized, but at different times. Torque should be maximized at the bottom of the gear (lower RPMs) as you build momentum towards the top of the gear, you rely less on torque, that's when maximizing horsepower becomes prevalent. Then you run it to the top of the rev range, up shift and start the process over again

how dou you explain this with physics?

It's a 9-5

You can't, because it's wrong.

You get maximum engine acceleration at maximum torque. You get maximum power at (you guessed it) maximum horsepower.

The "pull" you feel is the torque curve. The maximum speed you can maintain is the horsepower.

Horsepower is just the more universal number, since it's a better benchmark as it combines torque and rpm numbers.

What is best for the car and the engine? I shift whenever the gear lever "feels" like it.

The goal of shifting is to do whatever I want. Some bitch boy trying to pass me I shift up and laugh at him. Some bitch going too slow I shift down and vroom vroom on that bitch

So acceleration is based on torque, and max speed is based on horsepower?

acceleration is based on wheel torque, not engine torque

this is really hard to explain without just showing the math, but here is an analogy I made:

Imagine a father and his boy both driving posts into the ground for a fence. The father can swing twice as hard as the boy, but twice as slow since he is old and slow. The boy is hitting the post twice as fast, but half as hard as his dad. The boy and his dad both finish at the same time. You could say that the boy and his dad both have the same horsepower as they can both do the same amount of work in the same amount of time, however the dad has more torque.

since wheel torque is just engine torque multiplied by the gearing, the acceleration felt in a single gear mirrors the torque curve. HOWEVER, the total amount of acceleration per gear is best represented as horsepower

notice how the red graph in my pic has less peak torque than the black graph ( the numbers in the bottom left ) but in the torque-per-gear graph, the red graph has more wheel torque

cont.

FUG wrong pic

the reason the red graph has more wheel torque, is because of the higher final drive ratio

shifting about half way through the rev range. Doesn't stress the engine. I hear if you have rotaries that you need to spin them at 7k often to remove carbon though

Thanks, I understand almost all of that. I still don't 100% understand why HP best represents total acceleration per gear though.

I am not too great at explaining things, sorry.

this dude has a good explanation (fuck engineering explained)
youtube.com/watch?v=X7KWtf4wqN4

horsepower is a function of rpm
rpm changes as you shift gears

>Horsepower doesn't change as you switch gears
>what is gear based boost