What drivetrain would you put in for 30 mpg?

[Clone TIE Pilot]

C4 vettes with moon hubcaps might have a .29 Cd but actual 2002 vettes don't (maybe a small scale plastic model of one did without mirrors or scoops or hood gaps):

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At speed its almost as high as my jacked up miata. C4 were the most aero. The C5 were styled, the c6's went back to Aero, the C7's were styled, with all of the aero in downforce.

Stock C6 ZO6's (505Hp) (aero) run about the same as C7 Z06's (650HP) (styled, with downforce) in the standing mile and are only about 6 Mph faster than Stock, '94 405Hp ZR1's...with nearly 250 more Hp.

If a stock C4 had a stock C7 Z06 motor, it would be at least 10mph faster in the standing mile than a C7 Z06, weighing the same.

Chevy won't post a Cd number for the C7, but it has to be well over .4

A1000lb heavier Hellcat Charger will run away from a C7 Z06 above 120 mph. 57 more Hp isn't why.

The .29 rating is on a list of cds which includes the cd of Monte Carlos and Regals. Looking around elsewhere online, the cd rating of 02 vettes ranges from .29 to .31 which is better than a G body. Of course sedans can have better cd than sports cars which sometimes sacrifice increased drag for more downforce for improved traction. Also, like with accounting, measurement numbers and ratios can be fudged with to reach a desired outcome. Either way, g bodies have a lot of room for improvement concerning air drag.

 

[pontiacgp]

the Corvette is designed for alot of downforce to help it stick the road in corners. The Formula 1 cars with their downforce weigh as much as a Greyhound Bus going down the staights. The drag coefficient on a stock G body is all due to resistance with virtually no downforce.

 

[UNGN]

The .29 rating is on a list of cds which includes the cd of Monte Carlos and Regals. Looking around elsewhere online, the cd rating of 02 vettes ranges from .29 to .31 which is better than a G body.

I have said it many times : anyone can make a table and post it on the internet. That doesn't make it true.

My original post about Corvettes was about C7 Z06's, not "2002 Corvettes" That is a straw man you were beating up.

C7 Z06's have a ton of drag... literally. Don't you wonder why C7 Z06 guys don't brag about how fast they are? That makes them unique among Corvette owners. Even owners say the 650Hp C7's are "6 mph slower" that the 505Hp C6 Z06's and even have a slower top speed than 405 Hp C4 ZR1's... with 250 more Hp. When someone posts a video of a C7 going over 180, they (actual C7 Z06 Owners, not internet trolls or kids in the parents basement) all call BS on the guy and say it was a hill or had a tailwind.

To visualize downforce's effect on drag, mount a sheet of plywood on the roof of a car at a 45 degree angle. For every pound of downforce that is created, a pound of drag is added.

 

[pontiacgp]

On our sportsman and pro later model circle track cars for time trials we would tape up the openings for the brake ducts and the rad in order to get more downforce which improved the lap times. With very little fuel for less weight but with everything taped off there was more drag but the improved cornering overcame that. We had size restrictions on the rear spoiler which is needed for cornering but it adds to the drag going down the straight. Every car will have drag and you want to make sure that the drag you have is beneficial to the handling of the car. UNGN may not know this but the sheet of plywood on the roof of a G body was a rule at an annual race I believe at Daytona. They had to put the huge spoiler on the roof of the G body to slow the cars down on the longs straights or they would be too fast for the corners and the void behind the flat back window would lift the back end making the car uncontrollable

 

[vanrah]

Greetings; Kinda back on subject. If I was going to built a high mileage automobile & it was to be GM based parts, consider this combo. Cost & assembly, low maintenance. I'd start with a 302 inch 4" bore 3" stroke, small 2" rod journals, aluminum heads with small runner (around 185 cc's) intake ports, the lightest flat top pistons you can afford with shortened pins, at least 10.5 to 1 compression, roller cam around 220* @ .050" duration max, intake to match 1000-5500 RPM & a 500 CFM AFB (ok Edelbrock) carb or the smallest QJet (my preference). A 700R-4, 1500 RPM stall, Aluminum shaft, 2.73 gear & every weight saving suggestion that comes your way. And keep the front tires under 215's & the rears 225's or less. You will be money ahead not counting the hours & head aches saved. Plus if ya ever want to sell it it will look right. Ole Bob.
Ps: Don't forget every Aero advantage that comes your way including a belly pan.

 

[pontiacgp]

why not just get the Uber app and not worry about mpg....😎

 

[Clone TIE Pilot]

I have said it many times : anyone can make a table and post it on the internet. That doesn't make it true.

My original post about Corvettes was about C7 Z06's, not "2002 Corvettes" That is a straw man you were beating up.

C7 Z06's have a ton of drag... literally. Don't you wonder why C7 Z06 guys don't brag about how fast they are? That makes them unique among Corvette owners. Even owners say the 650Hp C7's are "6 mph slower" that the 505Hp C6 Z06's and even have a slower top speed than 405 Hp C4 ZR1's... with 250 more Hp. When someone posts a video of a C7 going over 180, they (actual C7 Z06 Owners, not internet trolls or kids in the parents basement) all call BS on the guy and say it was a hill or had a tailwind.

To visualize downforce's effect on drag, mount a sheet of plywood on the roof of a car at a 45 degree angle. For every pound of downforce that is created, a pound of drag is added.

The cd figure I quoted is for 2002 Z06s, and the quote cd of .31 to .29 is fairly constant among the net on different sites for that model year as is the Regal cd figures of .45 to .38, sounds like bullet calipers lol. I wasn't trying to attack you and claiming I did with a strawman argument is in fact a strawman in itself.

Getting a bit on track, my main point was that getting more mpgs is more than just the powertrain. Reducing weight and drag reduces power consumption and can save a good bit of gas. If you want to build a hypermiler g body, start with a aerocoupe.

 

[UNGN]

The cd figure I quoted is for 2002 Z06s, and the quote cd of .31 to .29 is fairly constant among the net on different sites for that model year as is the Regal cd figures of .45 to .38, sounds like bullet calipers lol. I wasn't trying to attack you and claiming I did with a strawman argument is in fact a strawman in itself.

I didn't think you were attacking anybody. My point still is a 2002 Z06 Corvette drag coefficient doesn't have anything to do with a C7 Z06's drag.

Here is a good article on wind tunnel testing of C1 thru C6 Corvettes. It pretty much confirms everything I've witness about corvettes doing 15 or so mile and 1/2 mile events over the years

From the article: "Because it has a greater frontal area, the C5 Z06 actually has slightly more drag than a C4 Corvette. Much of this apparently comes from the Z06's redesigned nose. It contributed to more aero lift on the front end versus the standard model, while the Z06 had considerably less lift at the rear end."

The C4 Corvette in the test was a widebody ZR1 and not a std C4, which would have even less drag than a C5 Z06. I'm sure in the future someone will similarly test a C7 Z06 and the new ZR1 and the owners won't be shocked when it shows more than total drag than any previous corvette.

 

[DRIVEN]

This subject comes up pretty regularly even thought the question gets phrased a bit differently. If you want to get max MPG all you have to do is look to the manufacturers. Obviously aerodynamics and weight savings are a given. Does a Prius have big wide tires? Nope. Small skinny ones. The OEs also design engines for torque and use transmissions that try to keep that engine at max torque no matter what the speed (6,7,8 speeds, CVT). They also have countless small touches like alternator clutches, electric power steering, adaptive AC, etc.

What would I put in a Gbody for max MPG? Something with a long stroke and small bore with high compression that was cammed for low rpm torque. Something in the neighborhood of 175-250 cid would probably get the job done. Ideally an aftermarket EFI with closed loop capability and timing control. I'd use a lockup 3spd auto and whatever rear gears calculated to match cam specs at cruise speed. Pizza cutter tires not only have low rolling resistance, they're cheap to buy. I might then turn my attention to aerodynamics. I wouldn't expect it to be fun to drive.

 

[Z48LT1]

Has anyone suggested an L99 yet - 4.3L version of an LT1 from a '94-'96 Caprice? It's got the reverse coolant flow that allowed the LT! to run 87 octane and 10:1 compression ratio. There is (was) a thriving cottage industry of tuners who reprogrammed the PCMs for higher performance; they could easily turn their attention, if they haven't already, to improving economy. Intakes and exhausts have plenty of cfm capacity but could undoubtedly respond to clever modifications to optimize flow. Other geniuses might be able to do clever things with selective cylinder shutdown. Back in the day, Impala and Caprice owners were alleging they were getting 25mpg on the highway. Making the all-out compromises for high mileage performance (skinny tires, high gearing, low viscosity lubricants, etc) should make 30 mpg a reasonable goal.

If this repeats someone else's suggestions, apologies.

Cheers - Gary

Edit: T56 and 2:56. It even rhymes. Sort of.🙂