And manual transmission cars kinda, though the energy is still wasted of course
Not saying it's smart but when predictably decelerating on the highway I sometimes shift gears by rev matching and changing without even touching the clutch, for the fun of it.
I’d wager bordering on 100% of my clutch use is when coming to a complete stop.
Hence Quattroportes eating clutches like nobody’s business while the harder-ridden higher-power Ferraris don’t.
As such downshifting would not wear clutches much.
And anecdotally I’ve never suffered from or heard of engine braking causing clutch issues.
Idk how the Ferraris are different. They're lighter at least. Think they also have a different version of the "Superfast" software.
Anyway... I do engine-brake it. The real brakes appreciate not having to stop that limo by themselves.
I've never driven an automatic Ferrari or paddle shifted Ferrari to compare, but the QP that I drove (Ferrari V-8, I think that it even said Ferrari on the valve covers maybe) didn't have anything outstanding about the transmission that I remember. I thought it was a regular hydraulic automatic with a torque converter, so they really did tune it nicely. The robotic Toyotas I could feel. Maybe had they not tuned it so nicely it might have lasted longer?
Also, I have never ever had to replace a clutch, and I drive my cars way past 100k miles.
If your comment wasn't meant to imply that engine braking wears the clutch more than normal gearing, if you just want to avoid gear changes as much as possible, disregard this comment. (Although... I'm not sure that that's a valid worry, modern clutches last a LONG time when used properly)
You don't make it slip when shifting gear.
It wears the clutch but clutch wear is massively dominated by starts from a stop or other cases where you actively slip it any noteworthy amount so just rowing the gears up and down doesn't do much.
You can do it in an automatic, you just have to force it to select a lower gear using the gear number options (1, 2, 3, 4) or using the tiptronic mode. The lower gear means the engine will displace more air in the same amount of time, increasing the rate it pulls energy from the wheels.
People think you can't do it in automatics because they try very hard to keep engine RPM low where the effect is diminished.
If you release the compressed air without pushing the cylinder down you would lose that energy, but you would need a extra device to do so (by lifting a valve at the right time). This option does exist for large vehicles like trucks as a compression release engine brake [0], but this isn't something you'd have on a family car.
In a petrol engine you always want the same ratio of petrol to air in the mix that is taken into a cylinder. As you want to vary the amount of fuel, and therefore power developed, you have to be able to therefore limit the amount of air that is sucked in. Otherwise the engine would always run at full power.
There is a mechanical restrictor called a throttle plate that lives inside the throttle body that restricts how much air the cylinder can pull in (and therefore how much fuel is injected to get the same fuel/air mix). This is controlled by the throttle. When you are coasting, this plate is in its most closed position. This creates significant resistance on the intake stroke, and is where the majority of energy is lost during engine braking. This is also known as a pumping loss.
Diesels always intake the same amount of air, so they can compress it enough to autoignite the fuel. They vary the amount of fuel injected to the same volume of air. This means no throttle body or plate, so unless an extra exhaust restrictor has been added there is minimal engine braking on a diesel engine.
[0] https://en.wikipedia.org/wiki/Compression_release_engine_bra...
Though the ECU would be doing the AFR management on modern EFI engines as the injectors aren't vacuum operated like Carburetors were. You should be able to cut fuel injection when coasting in a modern engine, can't run lean if there's no fuel at all. Not sure if carbs could do the same.
More modern engines have electronically controlled throttle plates, and this is definitely somewhere you could do something clever like you suggest - cutting fuel flow but also maximising airflow when there is zero throttle input.
I assume engine braking is generally considered a beneficial thing by manufacturers, but it could be fun to be able to customise the amount. Or do something like have the braking come on gently at first then harder. Maybe even try and have a linear or flat response curve vs. engine rpm.
You can do this by letting go of gas pedal slowly. I have "current amount of fuel used" info in my car (liters/100km), it shows pretty clearly, that when going fast and slowly letting go of gas, amount of fuels slowly goes to 0. If I let go of gas fast, the engine is intelligent enough to not close throttle as fast as possible, still probably takes 1 second.
> More modern engines have electronically controlled throttle plates, and this is definitely somewhere you could do something clever like you suggest - cutting fuel flow but also maximising airflow when there is zero throttle input.
They cut fuel flow and close throttle plate almost completely but still allow some small amount of air, in order to actually do engine braking. If you need to coast, you can apply clutch in manual. Don't know that much about automatic, but from what I've driven, they use "lift gas" as a "engine braking" signal, so probably they can't really coast that good.
Funny because the cars build dates are only 2 years apart, 2005 and 2007, and they're both K20 engines but the engines handle so different.
The OEMs try real hard to prevent this because the amounts of emissions byproducts that aren't water or C02 they're allowed to produce are on the order of single digit grams per multiple miles (you can mentally file it as "about the baseline air quality in urban areas" though the rules are hugely more complex than that) so these edge cases matter.
Some recentish motorbikes have an option to customise the amount of engine brake, I suppose cars could have something similar, too.
You don't want to do this. Much of the engine braking effect is from pulling the intake air charge past the mostly closed throttle plate. On a car with a wide open throttle plate [even with no fuel], the engine is acting more like a spring than a damper. On the intake stroke, it will pull an intake air charge past the small restriction of the open intake valve(s), then compress it on the compression stroke, then release that compressed energy on the "power" stroke, then exhaust it past the small restriction of the open exhaust valves. Pushing air past the valves will cost energy, but it's not much.
This is why diesel trucks' engine braking works differently. (Diesels don't have a throttle plate.) They can open the exhaust valves to prevent the energy recovery in the "power" stroke to create a higher net braking force. Jake Brake: https://en.wikipedia.org/wiki/Compression_release_engine_bra...
It's basically like an air compressor that just keeps running despite hitting max pressure and every pump just goes out the blow off valve.
Toyota Sienna 2015 - the braking effect is unfortunately minor.
Using the numbered gear options will enable clutches/bands that provide more engine braking.
For example, if I brake somewhat hard from 130 km/h to 90, it will downshift from 6th to 5th. When riding normally, it would stay in 6th down to around 50.
Even with paddles, there's a delay, or it briefly goes neutral, or it doesn't rev-match well. Or you can't double/triple-downshift, which is worse when you have 8-12 gears. Allegedly wears them down faster too, which idk but would not be surprised if it were true given how unhappy it feels.
It’s just trivially easy with electric thanks to regen braking.
Though with modern cars getting heavier if you have a small ICE these days you have almost no engine brake which makes some cases more difficult (unless it’s a mild hybrid with an electric kers like some of the small engined fords). SUVs tend to have giant engines and pretty high rolling resistance, which I’d think would somewhat compensated for their higher inertia.
It’s all about learning your car’s behaviour and planning for it.