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 mpgMethodology: Air conditioning was off, windows were up, and fresh air was on fan setting 2.Route: 2 lane highway, straight, dry & level (follows river edge). The road runs SSW/NNE and can be found here: 1000 Islands Parkway - Google MapsTraffic 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.--- See also: |
So... that car has roughly 10x the horsepower of the Flea and 20x more than the ForkenSwift ... This should be interesting.
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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.
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Does this engine have cylinder deactivation?
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Looks like Pulse & Glide will work great at just about all "normal" speeds...
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Good question - I'm not sure. I'll find out of course.
--- NiHaoMike - we'll see about Pulse & Glide... |
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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.
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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!!!
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I suppose "very good highway mileage" is a relative thing, eh?
Depends where you're coming from. |
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coming up
Cool! Looking forward to it.Thanks!
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I just got rid of my 87 Volvo 740 Turbo wagon .40 Cd. On a good day with no AC 26.5-27.0 mpg at 65 mph. You drove it at 70 mph with the AC on 23-24 mpg was normal. After lowering, removing the roof rack, swapping out the automatic for a manual transmission and bumping up the rear gears to 3.31 for better gas mileage I could pull 29 mpg at 65 mph. I could pull 30-31 mpg at 55 mph. It was Clunkered on Aug 3rd for a 2010 Prius. I'm sorry 40 mpg city today is the 30 mpg highway of 15 years ago. |
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Heading out now to get the data...
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http://ecomodder.com/imgs/2008-corvette-geo.jpg
Nothing super surprising to report. I'll post the full details & chart later, but here are the highlights:
More to come... |
I've heard at 55 mph some owners (no AC) are getting in the low thirties.
Which just shows what really can be accomplished when the car companies are really trying. Imagine telling a Corvette engineer in 1970 that a 2009 Corvette would pull high twenties low thirties in fuel mileage, 0 to 60 mph in only 3.6 seconds, hit 100 in 7.9 seconds, and 150 in 17.5 seconds and still be able to hit 200 mph. :) |
Did P&G help, hurt, or have no effect?
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I have a pretty good recollection of road trip mileage on my cars. All thrashed to 7 mph above the speed limit before I hypermiled.
1959 Buick Electra (364 cu in) - 12 mpg 1963 Rambler American 220 - 25 mpg 1970 Datsun pickup - 25 mpg 1977 IH Scout II 4X4 (302 cu in) - 11 mpg 1976 Datsun B210 - 36 mpg 1983 Nissan Sentra wagon - 35-45 mpg 1987 AMC GTA - 36 mpg 1987 Chevy Astro (4.3 L) - 15-17 mpg (22 mpg @ 55 mph) 1996 Nissan Sentra SE-R - 36 mpg 2002 Nissan Sentra SE-R - 26 mpg (43 mpg hypermiling) 2006 Scion xB - 32 mpg (45-59 mpg hypermiling) |
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I've updated Post 1 at the top of this thread with this graph of the results, plus methodology & raw numbers.
http://ecomodder.com/imgs/graph-speed-mpg-corvette.gif |
Interesting: I just looked up the Corvette Z06's fuel EPA economy rating:
Model 1 Vehicle Characteristics It's 15 mpg (US) city / 24 mpg (US) highway / 18 mpg (US) combined No wonder the British guy was able to win his competition on % over the government rating. Extend the graph, and this car "meets" its EPA highway rating at 130+ km/h / 80+ mph! (Steady state, level road, etc.) That's astounding. In stock form, my car's "EPA highway" speed was below 100 km/h / 60 mph. |
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Thanks for posting this, MetroMPG. :thumbup:
That speed vs. MPG graph pretty much mirrors my experience with my Mustang. Most performance car enthusiasts ass-u-me performance cars have a "sweet spot" around 75 MPH. That just ain't so with modern (efficient) fuel injection systems. In my experience, the best FE is at the lowest speed in your top gear. In my case, about 35-40 MPH. And it's interesting that most people can't believe that a performance car can get fuel "economy". According to EPA's 2008 estimates, I should be getting 17 City/ 25 Highway/ 20 Combined with my Mustang. The worst I've ever gotten was .02 MPG under EPA Highway. (24.98) And that was because I ran it in the garage to charge the battery (at ZERO MPG) during the Winter. According to ecomodder.com's criteria, I've never not been a hypermiler with my Mustang. :) I'm getting better fuel economy with my Mustang than a lot of people get with their 4-cylinder Camrys and Altimas. :thumbup: A major part of it is the "nut behind the wheel" and route planning. As they say, YMMV. :) |
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My relative lack of experience with big displacement, high torque engines (with the single exception of my first car - in which I never paid attention to fuel consumption) had me doubting common sense. Not any more! (PS - my Firefly is a "performance car" of a different kind - high efficiency is high performance! I don't like that "fast" = the only kind of "performance".) |
But wait. You said the ScanGauge wasn't calibrated to the corvette. Doesn't that mean that those MPG figures you posted don't mean anything? Without calibration don't the scanguauge readings simply show the relationship between mileage and speed, and not actual MPG? I don't have or use a scanguage so maybe I just don't understand how it interacts with the car.
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The ScanGauge readings weren't verified against filling the gas tank of the Vette - that's what I mean by uncalibrated. So yes, there's the possibility the MPG figures aren't exact... but it's unlikely they're out by more than a few percent.
My experience with the SG (comparing with "zero offsets" to filling the tank in several vehicles) is that it's not usually far off for "normal" driving, like the kind done for this test. Quote:
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In my experience, the Scangauge tends to be slightly optimistic, but only by a small margin, like 3%. Whatever the offset is, it's a percentage and not a constant value. The curve on the chart will not change with calibration, just the scale on the Y axis would change. The most efficient speed will still be 30 kph / 37 mph, it just might be 36 instead of 36.5 mpg.
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Someone asked did it have cylinder de-activation earlier, I don't think it does. Are the Vett's still fiberglass?
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I believe the standard ones are, but the Z06 is carbon fiber.
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...anybody remember the Oldsmoble "Turnpike" cruisers? |
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I get 1080 and 1215, but it's close.
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I think this data vindicates my approach of low RPM = max MPG, even for gasoline engines. The Z06 with its LS7 engine has such mammoth torque as to allow operation at vividly low RPMs. The same principle works for a high-revving Honda engine, just the cutoff for lugging occurs at a higher RPM.
As you can see from this, the Tremec 6060 transmission used in the Z06 has a 0.63:1 top overdrive ratio, but a 0.5:1 ratio could be had if MPG were to be emphasized. Tremec TR-6060 transmission - Wikipedia, the free encyclopedia BTW, I am seriously looking at getting the Challenger version to replace the ZF6-650 in my truck. That with a couple of aero tweaks might get me over 30 MPG in my mixed-driving circuit. It has an optimal ratio spread and its 600 ft-lb rating is A-OK for my Powerstroke which has been dyno-tested to deliver 560 ft-lb max torque. Having a 1.54:1 overall reduction should give spectacular results. Too bad the GM 4.5 liter diesel is dead. Given the LS7 in this test is operating way below its peak volumetric efficiency, it is incurring huge pumping losses for not much power. The diesel suffers no such loss. It would be interesting to see what a 4.5 could have done if fed the 70 cetane Fischer-Tropsch fuel the Audi & Peugeot prototype racers use. |
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