When you let off the gas or during engine breaking do the fuel injectors completely stop injecting fuel? Heated discussion I need proof. Thanks

 

wouldent it stall then???.............

 

They supply only the amount of fuel required to keep the engine from stalling. This amount varies depending on the conditions (engine RPM, etc) but it is minimal.

This means you can coast at 6,000rpm down a hill in 2nd gear and get amazing gas mileage. I've actually done it with the car's real-time MPG indicator onscreen to prove to passengers that downshifting to slow down does not waste gas.

 

unless you have AT... which has that crazy "rev matching" thing which actually (from what I believe) injects fuel to match the downshifted RPM

 

That doesn't make sense to me. Once it has revmatched and engaged the gear (assuming you are off the gas), it is coasting just as a manual would.

There's no difference other than torque converter slop.

The revmatching is accomplished by controlling the throttle position to bring the car to the appropriate revs for a smoother downshift. I do the same thing with my foot on my 6mt.

My point is that at very high RPM you can easily demonstrate that the fuel injectors are not putting a lot of fuel in... just by coasting in a low gear and somewhat high speed.

 

the injectors FULLY Shut off when above ~1500 rpms.

you can confirm this with a scan tool that shows IDC (Injector Duty cycle) or with a wide band 02 sensor.

 

so if u coast down a really long hill will your car burn up?

 

Why would it burn up? I'm confused.

With the injectors off it is not supplying any fuel... so the car is turning the engine which basically means you will slow down.

Thanks above for the 1500 rpm info.. I knew it would depend on the RPMs but didn't know the details. Obviously at lower RPM we're concerned the engine might stall so it needs some minimal fuel.

 

also confused. why would it burn up?

The only thing i could think you mean is seize up. By lack of oil..
-NO. Everything works normally. The engine is still spinning due to the stored energy in the car which turns the wheels which are connected to the engine, thus spinning the engine. The engine then spins the oil pump and alternator and so forth.