Jeff The Pianist

Hi everyone,

I just heard from my brother, who works for Toyota, that the fuel injectors of modern car engines today stop sparying gas while the car is coming to a stop. For example, exiting on a freeway off ramp when the speed is pretty high and the RPM is around 2000. This could save you couple seconds of gas!

I've never heard of this before, and he asked me if my TSX has this type of feature. I have no idea if TSX has it or not, I doubt we do.

This feature is also similar to the newer BMWs (1 series?) where the engine completely stops while the car is idling. I guess in this case, it wouldn't be called idling anymore.

JTso

iTrader: (2)

No, the fuel injectors don't stop when the car comes to a stop so the engine can idle. However, the injectors stop or the pulse width greatly reduced when you "decelerate" like going downhill or getting off the freeway without pressing the gas pedal. It's been like this for years.

rb1

It seems like they could shut off completely as long as the engine speed is above idle, at least in theory.

ATsxMan8305

Hook up a pressure gauge to the fuel line to find the answer

JTso

iTrader: (2)

That wouldn't work as the fuel rail is pressurized when the main relay is energized. However, you can back-probe the ECU and verify the injector signals, or perform a data logging with a scan tool.

visuelz

If I'm not mistaken, the fuel injectors are parts that shoot fuel into the combustion chamber. If we turn those off, then there would be nothing to burn and that would lead to the engine turning off?

poltergeist

With the throttle closed on decel. the PCM shuts down the fuel injectors (under certain parameters) for fuel economy/emissions. Engine is "running" because the crankshaft is being turned by the driveline. Engine compression is contributing to slowing the veh.

loulinjai

I believe only some hybrid systems totally shut off the motor while regenerative braking, at least as of today.

jlukja

I had this question a few years ago and my research yielded the same conclusion.

JTso

iTrader: (2)

Here is something to back it up as well.

ATsxMan8305

Thanks JTso, and this makes sense to me b/c it allows the engine to idle (and thus, the fuel injectors will inject fuel) for under 1,000 RPM

dereksmalls

That's some interesting information. So that means I don't have to worry about wasting additional fuel when engine braking. I always wondered if I would be burning more fuel with the engine spinning at 4k while going down a hill, even if the a/f was lean. Now there's really no reason to ride the brakes!

alucardx

interesting

rb1

This means engine braking is even more efficient. If you push the clutch in and use the regular brake, then the engine will drop to idle speed and the injectors will come back on.

Coasting = great mpg...

TodaSi

Coasting in neutral = very good mpg
Coasting in gear = great mpg

In neutral engine will idle consuming fuel, if you coast in gear, no gas will be used until rpms fall to about 1000 rpms.

jlukja

coasting in gear = engine braking
coasting in neutral = only tire and air friction braking.

ck123

tsx does, when i let my foot off the gas pedal for a few seconds, the rpms drop to around 1000 rpms

Jeff The Pianist

Thanks for all of the replies and comments!!