The company car I get to use has an automatic transmission that drives me mad.
Its shift points are always right above the speeds I usually drive at.
It shifts into third at 40 km/h which is too fast for a speed limit of 30.
It shifts into fourth at 60 which is too fast for a speed limit of 50.
And it shifts into fifth at 80 which is too fast for a speed limit of 70.
So you’re constantly driving with too high rpm’s, burning more fuel and making more noise than you’d have to.
It has a “manual mode” where you can shift by moving the stick up or down. But it doesn’t actually do anything. If you shift at a different point than the automatic would, you just get a “shift denied” message on the dash, even though the rpm’s wouldn’t even get close to being too low.
And when you push the gas pedal just a bit more than half, it shifts down and the engine roars, but it doesn’t actually achieve much cause the car doesn’t have much power.
Internal combustion engines are most fuel-efficient at low rpm’s (<1500) and full throttle, and that’s impossible to do with this transmission. So it only gets 34mpg (7l/100km), and it’s a Diesel hatchback. My old manual car also had a 34mpg rating, but the way I drive I could get 47 (5l/100km), and it had a gasoline engine.
What’s the torque band? Driving a diesel, it’s really high compression and torque is applied low in the rpm range. Gasoline is a lot lower compression and might be twice the rpm to get the most torque. Outside of that torque band and your using more fuel for less movement.
Every engine is the most efficient at max torque, which for a typical car’s gasoline engine would be around 4500 rpm.
But that “efficiency” means fuel burnt per unit of power. At max torque, the engine makes much more power than you need for normal driving, burning more fuel than necessary.
As a rule of thumb, you get the best real-world fuel economy at full throttle just above the low rpm limit where the engine would run “jerky”.
That’s at 1000-1500rpm for a passenger car’s gasoline engine.
At that rev range, you may only get 40 horsepower out of an engine rated for 100 at max torque, but that’s enough. You only need around 10 to maintain your speed against wind resistance, and you don’t actually lose any time accelerating slowly cause you’re gonna be at the next red light soon, anyway.
For reference, when I’m accelerating from a stop to highway speeds, I’ll shift to 2nd gear as soon as I’ve moved one car length, 3rd at 30km/h, 4th at 40, 5th at 50, flooring the throttle the entire time I’m not shifting. Then I’ll stay in 5th unless I’m forced to brake below ~45 again. Up or down a hill I’ll go one gear lower.
In my Diesel van, I regularly drive 40 in 5th gear.
I can’t make you take my word for it, but this is what I learned in a work-sponsored course for fuel efficient driving, and it got me much better fuel economy than the manufacturer’s claim for any car I drove in the past 20 years.
My current car with a stick is able to squeeze 34 MPG highway, 3 over the rated 31. However, the CVT version is rated for 38 highway in the same conditions.
It’s been a while since I regularly used a car, but I remember the automatics my father had having some sort of logic that shifted up when driving at a constant speed, than back down when wanting to accelerate.
Now those where fancy pants Systems (I think they called them 7G-Tronic), but this was also over 10 years ago, and such logic doesn’t strike me as overly complicated, so I’m surprised there’s current cars with static shift speeds.
The company car I get to use has an automatic transmission that drives me mad.
Its shift points are always right above the speeds I usually drive at.
It shifts into third at 40 km/h which is too fast for a speed limit of 30.
It shifts into fourth at 60 which is too fast for a speed limit of 50.
And it shifts into fifth at 80 which is too fast for a speed limit of 70.
So you’re constantly driving with too high rpm’s, burning more fuel and making more noise than you’d have to.
It has a “manual mode” where you can shift by moving the stick up or down. But it doesn’t actually do anything. If you shift at a different point than the automatic would, you just get a “shift denied” message on the dash, even though the rpm’s wouldn’t even get close to being too low.
And when you push the gas pedal just a bit more than half, it shifts down and the engine roars, but it doesn’t actually achieve much cause the car doesn’t have much power.
Internal combustion engines are most fuel-efficient at low rpm’s (<1500) and full throttle, and that’s impossible to do with this transmission. So it only gets 34mpg (7l/100km), and it’s a Diesel hatchback. My old manual car also had a 34mpg rating, but the way I drive I could get 47 (5l/100km), and it had a gasoline engine.
What’s the torque band? Driving a diesel, it’s really high compression and torque is applied low in the rpm range. Gasoline is a lot lower compression and might be twice the rpm to get the most torque. Outside of that torque band and your using more fuel for less movement.
Every engine is the most efficient at max torque, which for a typical car’s gasoline engine would be around 4500 rpm.
But that “efficiency” means fuel burnt per unit of power. At max torque, the engine makes much more power than you need for normal driving, burning more fuel than necessary.
As a rule of thumb, you get the best real-world fuel economy at full throttle just above the low rpm limit where the engine would run “jerky”.
That’s at 1000-1500rpm for a passenger car’s gasoline engine.
At that rev range, you may only get 40 horsepower out of an engine rated for 100 at max torque, but that’s enough. You only need around 10 to maintain your speed against wind resistance, and you don’t actually lose any time accelerating slowly cause you’re gonna be at the next red light soon, anyway.
For reference, when I’m accelerating from a stop to highway speeds, I’ll shift to 2nd gear as soon as I’ve moved one car length, 3rd at 30km/h, 4th at 40, 5th at 50, flooring the throttle the entire time I’m not shifting. Then I’ll stay in 5th unless I’m forced to brake below ~45 again. Up or down a hill I’ll go one gear lower.
In my Diesel van, I regularly drive 40 in 5th gear.
I can’t make you take my word for it, but this is what I learned in a work-sponsored course for fuel efficient driving, and it got me much better fuel economy than the manufacturer’s claim for any car I drove in the past 20 years.
My current car with a stick is able to squeeze 34 MPG highway, 3 over the rated 31. However, the CVT version is rated for 38 highway in the same conditions.
It’s been a while since I regularly used a car, but I remember the automatics my father had having some sort of logic that shifted up when driving at a constant speed, than back down when wanting to accelerate.
Now those where fancy pants Systems (I think they called them 7G-Tronic), but this was also over 10 years ago, and such logic doesn’t strike me as overly complicated, so I’m surprised there’s current cars with static shift speeds.