It's funny, I just got a new car (manual, of course) and it has "rev-matching" so when you shift down a gear it automatically heel-toes (basically a throttle blip) which means there's not much engine braking going on during downshifts.

Granted when driving quickly and dropping a cog or two to overtake a slow moving vehicle it's great. Slowing down for traffic? Not so good.

Took some getting used to changing down gear and not feeling the car slow.

EDIT: To clarify the folks downvoting me here's and example of how it works:

1) You're in 6th gear doing 60mph. 2) You come up to a tractor doing 25mph. 3) You brake and slow, as you do you compound change from 6th gear down to 3rd. 4) As you place the car into 3rd the ECU gives the engine some extra throttle and match the speed of the gearbox. You can physically see the revs rise BEFORE you release the clutch. 5) You release the clutch and don't feel any transmission shunt or immediate engine braking.

This reduces wear and makes it smoother.

For more detail watch this YouTube video: https://www.youtube.com/watch?v=FnXLZg_O1rk

What you're describing is not engine braking, it's really clutch braking. Engine braking is what happens when the clutch is fully engaged and the compression of the engine slows the vehicle down.

Downshifting to second so the engine is at 5000rpms and letting it gradually slow the car down is engine braking, and this is good. Putting the gear selector in second and slowly releasing the clutch (with no throttle/rev-matching) to slow down the car is clutch braking and its bad (which is why cars automatically rev-match now).

Are you sure it actually blips the throttle and it's not just the synchromesh gear in the gearbox? There's no need to blip with a synchronized gearbox, which has been the standard in road vehicles since the 1930s or so.

Even if it does blip, you can still utilize engine breaking but you have to shift early and sometimes skip gears.

Not sure why I got downvoted here.

It actually blips the throttle. It's not the syncho, trust me.

http://www.minif56.com/forum/353-mini-cooper-f56-forum/7010-...

It's not the first car to have it either, and there is actually PLENTY of reasons why you'd need to blip or heel-toe when driving even in a car with a synco'd gearbox.

https://www.youtube.com/watch?v=FnXLZg_O1rk https://www.youtube.com/watch?v=p4n9tMdISBg

Yeah, it's not completely out of question that it would blip the throttle, but it's not a very common feature either.

I drive an old piece of shit car with a very worn out synchromesh gear (it's a conical brass ring with grooves for friction - that wear out) so it's a bit smoother to blip the throttle a little when downshifting to the smallest gears. I don't heel-toe or left foot brake on the road (I'm proficient in both from simulator and performance driving), I just use my right foot to give a little gas. I rarely need to brake and downshift at the same time unless I'm in heavy traffic, I mostly rely on engine braking controlling speed.

Outside of performance driving or old worn out cars like mine, there's no real need to rev match on normal road cars.

How does the clutch in your car work? In an unsynchronized gearbox, you'd double declutch and blip when the clutch is up and gear is neutral (to rev match gears inside the gearbox). Is this thing just to match the engine and gearbox input shaft speed? Not gears inside the box? Or does it do something similar to double declutch w/ heel-toe?

I know how car without a synchro works, the first car I ever drove was a 1950's Land Rover.

Watch the video, it works exactly how Engineering Explained describes, he even explains the benefits.

Downshifting more environmentally friendly?

Because burning more gas is better than heating up break pads?

Reference?

Downshifting to slow down uses zero fuel. Modern cars cut fuel completely when coasting is detected based on throttle position and whether gear is engaged among other sensors. This is only used a lot in manuals since the torque converter causes freewheeling at lower rpms. It's known as deceleration fuel cut and it's standard in OEM and aftermarket engine controllers.

Typically the engine "restarts" when rpm drops to a bit above idle speed but as mentioned it doesn't happen as much in automatics because of the freewheeling. In automatics it only occurs when deceleration starts at high rpm or the clutch within the torque converter is locked during steady highway driving. I assume shifting into "low" may enable deceleration fuel cut in more situations assuming the driver may be using it to slow down, but I have no evidence of that usage

No reference, but engine braking means you don't need to send petrol to the engine (since the engine is being driven by the car's momentum), so there should be no fuel usage. When the car is stopped, then it will use more petrol (to keep the engine from stalling). Assuming all things are equal, then when you brake with your foot brake, the energy that gets turned into heat in the brake pads could have instead been turned into energy that keeps the engine spinning (and so it doesn't need to come from petrol).

Basic understanding of an injected engine and power conservation should be enough here.

When you're downshifting you're braking with your engine. This means two things:

1. Less fuel is burned. The injectors are closed while the engine is braking.

2. Momentum, not fuel, is used to drive the alternator, AC etc.

If you instead were to brake the car, it would need to use fuel just to keep the engine running. In the same way as it would if you were idling parked. Even more fuel is needed to combat the resistance from your AC and alternator.

Engine braking in most petrol cars is an efficient tactic due to DFCO[0] - less efficient than coasting in neutral, but you're not as in control of the car when not in gear, so the combination of both being in control and getting a "free" slowing effect (especially when judging upcoming traffic, as opposed to coming to a complete halt) can be better than just mashing the middle pedal.

[0] Deceleration fuel cut off

If you're slowing down to traffic light, it's more efficient than coasting in neutral. You've to slow down anyway and slowing down with engine braking is 0.0l/km. While coasting still burns some fuel.

In addition to that, some newer cars charge battery when engine braking. Which is effectively saving fuel later.

Uses engine compression to bleed off kinetic energy (no additional fuel use). Not more environmentally friendly, but saves on brake wear.

Semis utilize this mode of braking heavily: https://en.wikipedia.org/wiki/Compression_release_engine_bra...

Actually, it uses a tiny bit less fuel, since it doesn't have to idle.

Was taught to do it in drivers ed, which features environmental driving here. The point is not to aggressively downshift, but to let go of the gas and then downshift when the RPMs are lower. You still want to keep the RPMs relatively low. This is preferred to a situation where you would keep your speed and use the brakes at a later point in time. I should probably not have called it downshifting.

I had assumed engine-braking will heat up the engine more and use more oil and increase general wear on the engine and reduce it's service life. New brake pads seem cheaper and more environmentally sound than having the engine serviced/replaced and burning more oil...

You can downshift and use the motor for breaking. When doing that, you don't burn any fuel at all, as the kinetic energy of the car will help keep the motor turning. You have the same effect in automatic transmissions when letting go of the gas pedal.

Downshifting doesn't really slow you down if you have one of those new 3 cylinder gas engines, for their lack of a throttle valve.