2014 Chevrolet Corvette Stingray Long-Term Road Test


2014 Chevrolet Corvette: Engine Braking and Rev Hanging

November 21, 2013

2014 Chevrolet Corvette

When you lift off the throttle in our long-term 2014 Chevrolet Corvette, not a whole lot happens. The engine essentially freewheels for what seems like a few seconds. Then, finally, you get the engine braking you were expecting, and hoping for.

This "rev hanging" phenomenon is an undesirable byproduct of the engine calibrator's attempt to clean up the emissions of the Corvette's 6.2-liter engine. Basically, by keeping the throttle open during the overrun (you lift off the pedal, the injectors are switched off), the throttle stays open to allow fresh air into the cylinders to help oxidize unburned hydrocarbons. While it is effective at this scrubbing task, it also scrubs engine braking. Bew.

The C7 isn't the only car to exhibit this trait, but that doesn't make it any better. Usually what happens is that the automaker gets enough customer complaints that it issues an ECU reflash with revised throttle mapping to reduce the rev hanging. Or they make a running ECU program change along the way. I expect GM will follow a similar pattern with this car.

For kicks, on the complete opposite end of the overrun-engine-braking spectrum, the car that's hyper-willing to jump into full engine braking at the slightest hint of a throttle lift is the Ferrari 458 Italia. It's almost disconcerting. And now you know.

Jason Kavanagh, Engineering Editor

Comments

  • duck87 duck87 Posts:

    Rev-Hang is the most annoying thing in a sports car. You guys complained about it in the Civic Si you had as well. You might need an aftermarket calibration to get that response you are looking for.

  • homer281 homer281 Posts:

    With all the various settings and adjustments on the Vette there isn't any "sport mode" or something that will adjust this? I understand it's for emissions but don't emissions tests not usually test sport/race modes?

  • juwu juwu Posts:

    my sister's 2007 sti does this also. it's disconcerting. feels like the car is still accelerating with my foot off the throttle. at the track i had to let off the pedal a second or two before my actual braking point.

  • stovt001_ stovt001_ Posts:

    My NC Miata also jumps into full engine braking at the slightest hint of throttle lift. The engine braking in that car is rather strong too. Just flicking the cruise control speed toggle once to scrub 2 mph from the set speed induces a head-jolting deceleration.

  • noburgers noburgers Posts:

    @stovt001 Miatas tend to have cruising RPMs almost twice that of the Vette, so it might be a symptom of engine speed. I agree with the others that in a sports car the lag would annoy me during spirited driving, and that I would think sport setting w

  • greenpony greenpony Posts:

    What I find interesting about the ST Focus is that the revs hang too, but they drop a few hundred rpm first so they're almost right where they need to be for the next higher gear. I'd wager that the rev hanging in this Corvette would be more tolerable if GM had calibrated the motor similarly.

  • mfennell mfennell Posts:

    I'm not completely satisfied with the explanation. How long could it possibly take for the cylinders to "clear" with the injectors shut off? At 2000 rpm, the engine is spinning 33 times/second. That's 16+ full cycles per second. That, and there's plenty of friction to slow the assembly down throttle plate opened or closed. Shut an engine down (one with a mechanical throttle) the second you floor it and see how long the revs hang... They must be ramping the injectors down, maybe to reduce NOx (?).

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