I’ve heard people say that fuel injection automatically turns off when you let the car coast in gear, but if I completely let off the accelerator in first gear, the car will only slow down to 3-5mph (depending on the car) and will then stay at that speed indefinitely like a lil’ cruise control, suggesting that the car was always injecting fuel at engine idle ratio?
I understand this kind of question has been asked before, but as this element doesn’t check out, I don’t believe it has actually been completely answered.
In: Engineering
It’s called over-run fuel cut. When you take your foot off the accelerator, you’ll notice the rpms don’t drop at all (in a manual) or only drop a bit (automatic). This is because the vehicle is now turning the engine as it is still moving. In this situation, fuel is not required, so once throttle position reaches zero, the engine load goes below a certain threshold, and the rpms are above a certain number, the computer cuts fuel. As soon as any of those criteria are no longer true, fuel comes back. You can’t feel this in most cars because the thresholds are minimal, and engine load is next to nothing.
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