Tested: speed vs. MPG, 2008 Corvette Z06 (505 hp)
 

http://ecomodder.com/imgs/2008-corvette-z06.jpg

One of the guys I sail against regularly in our local sailing races (24 foot Shark fleet) has a 2008 Corvette Z06 with the 6-speed manual transmission.

After last night's race (we won! :)), I brought up the subject of fuel economy, and he gave me his version of the occasionally heard story that Corvettes get surprisingly good fuel economy - given their power - when driven reasonably.

We know that the car's "secret" is its massive torque paired with very tall gearing and relatively good aerodynamics (Cd of 0.28, CdA of 6.27 for a '92 Vette - source), which allow it to loaf down the blacktop in top gear even at fairly low speeds. Sometimes they even win mileage competitions: http://ecomodder.com/forum/showthrea...thon-5508.html

Just for kicks, we're going to go out and get data to do a "speed vs. MPG" graph in the next few days.

Watch this thread!

[EDIT, Sept 11: added EPA ratings...]

For reference, the car's EPA fuel economy ratings are: 15 mpg (US) city / 24 mpg (US) highway / 18 mpg (US) combined

Source: Model 1 Vehicle Characteristics

[EDIT, August 28: added graph below, plus methodology ...]

http://ecomodder.com/imgs/graph-speed-mpg-corvette.gif

Weather conditions:

August 27, 2009
Sunny, 18C
Wind E 7 km/h
Pressure 102.2 kpa
Humidity 48%

Raw numbers:

Speed km/h ... E (mpg US) ... W (mpg US) ... Avg mpg

50 ... 28.4 ... 29.0 ... 28.7
60 ... 35.9 ... 37.0 ... 36.5
70 ... 35.6 ... 35.6 ... 35.6
80 ... 33.4 ... 33.4 ... 33.4
90 ... 31.8 ... 32.1 ... 32.0
100 ... 30.6 ... 29.3 ... 30.0
110 ... 28.1 ... 27.5 ... 27.8
120 ... 25.9 ... 25.6 ... 25.8

Methodology:

Air conditioning was off, windows were up, and fresh air was on fan setting 2.

Speed was set once per pair of bi-directional runs with cruise control, cancelled with the brake between runs. Car was brought up to speed & leveled off before passing a "start" marker (road sign) where the ScanGauge was reset. (Note: other than entering engine size, ScanGauge was not calibrated to this car, speed & fuel use offsets were left at zero). Reading was taken after passing a "finish" marker and cruise was cancelled.

Route:

2 lane highway, straight, dry & level (follows river edge). The road runs SSW/NNE and can be found here: 1000 Islands Parkway - Google Maps

Traffic conditions:

There was rarely traffic ahead in my lane, and no closer than 5 seconds when present. Some traffic was present in the oncoming lane.

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See also:

• http://ecomodder.com/forum/showthrea...atic-6710.html

• Tested: speed vs. MPG in top gear (1998 Geo Metro / Pontiac Firefly)

• http://ecomodder.com/forum/showthrea...nomy-7552.html

So... that car has roughly 10x the horsepower of the Flea and 20x more than the ForkenSwift ... This should be interesting.

True! I'm just going to guess, but I think despite having ~10x the Flea's peak power, it may post numbers that are in the range of 50% of the Flea's original speed vs. mpg graph, at least at lower speeds.

Does this engine have cylinder deactivation?

Looks like Pulse & Glide will work great at just about all "normal" speeds...

Good question - I'm not sure. I'll find out of course.

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NiHaoMike - we'll see about Pulse & Glide...

It's easy to make a high consumption car win in economy trials where the % better than official figures wins, in fact the less economical the car is normally, the easier it is to win, just drive economically and switch off at every opportunity. It's the switching off that really pays the dividend.

Note the overall economy is only 30mpg (imp)
averaging 30.96 mpg over the trip's two-day, 411-mile route. That mark represents an improvement of 61.26-percent over the Z06's official European combined mileage figures and is a new record for the MPG Marathon

Point taken, dieselman. Scoring method is a regular bone of contention in mileage competitions.

I have a 93 Trans Am with 6-speed that also gets very good highway mileage (high 20's). It's not how much power you have, it's how much you USE!!!

And if you think high 20s is good mileage, you're living in a different world :-) On an open highway with nothing much in the way of mountains to climb (say Hwy 50 from Carson City to the Toiyabes), I'll do 80+ mpg round trips - and that's including maybe 20-30 miles of dirt to get to the trailhead.