rai

I've seen this stated in a number of threads, that a vette gets excellent mileage you know 30mpg all day long. What a marvel for such a big so-called thirsty V8.

Laugh, puny I4 can't get mileage like a vette.

It's not just this I'd like to discuss, but the whole Mileage v HP equation.

To me it's simple, in general the more HP you make the more fuel you will use.

Here's a link -->>CLICK

jist of the link a 1000 HP engine MUST burn 5-liters of gas/minute in order to make that 1000 hp. Same goes for any engine. A 500-hp Z06 engine should burn 2.5L/min and a 240hp S2000 engine burn half that. When producing max HP.

Now that's not to say all engines are the same efficency, but in general. If you make the power you have to pay for it.

SO why are Vettes getting 30mpg + on the highway? Well it's quite simple, they are not useing 400hp to push along at a constant speed. May only be useing 100hp. Same with a S2000. Constant speed does not require that much HP. Gearing and drag coefficent as well as engine losses all add up to get your "constant highway mileage".

Also in 6th gear the Z06 is just slightly quicker than a S2000. 30-70mph acceleration around 2 sec quicker than a S2000.

Take it all together. S2000 in 6th gear probably gets 30mpg same with Z06. Both are moving same mass (within a few hundred pounds) both accelerate within 2 seconds of each other. Both proably are making 100hp at constant 60mph.

But most people aren't driving 200 miles at constant 65mph. Most people are driving in the real world. Stop and go, 0-60 blasts, 15 miles here 12 miles there. etc..

So what we should be looking at is does a Vette get anywhere near what an average S2000 gets? I'd say probably not. If they are driven like I drive, with red-line shifts. Now if you drive a Vette as slow as a S2000 you'd probably get similar mileage. But you'd be driving the vette slow, so it's not like you're getting 12s in the 1/4 and also getting 20s MPG.

I just looked at a few tests, Z06 average test 17mpg, C6 average test 15mpg etc.. I'd bet your typical vette is getting in the high teens and your typical S2000 is getting in the low 20s.

I know its not the same car as a Vette, it's a lot heavier. But a CTS-V has a 400hp vette engine. Is listed at city 16mpg/highway 25mpg. R&T long-term update over 5000 miles is getting 14mpg.

I'm not complaining, or putting down a Vette or a CTS-V or saying a V8 is a pig. I just am trying to point out, there's no such thing as a free lunch.

steve c

You don't have to drive the Z06 like a raped ape to achieve quick performance, thus, even in town you might manage to get better fuel economy and be faster.

The EPA rating for the Z06 is 18/28 vs 20/25 for the S2000.

Plain and simple, the Z06 gets better fuel economy than the S2000. You can create all the special circumstances and anecdotal evidence you want (I for instance don't see much over 15 in my S2000) -- but the EPA numbers don't lie.

rai

I would say the EPA numbers do not reflect real world driving. I never get EPA numbers in any of my cars unless it's constant highway miles.

Also you may know the vette has a CAGS (or what ever it's called) that "tricks" the EPA. If you drive part throtle and shift low in the rev range like below 3000 rpm (?) you can't go from 1-2 gear GM forces you to shift to 4th (ie fuel saving mode). This is done (I think) specifically to escape any gas guzziler tax. A M3 has to pay a gas guzziler tax b/c it shifts normally and it doesn't have 2 or 3 overdrive gears like a vette.

Also any vette owner worth his salt will dis-able the CAGS a $2 fix I'm told, or drive it aggressive enough so the CAGS don't force a 1-4 shift.

JettaGT

i wish my car had enough torque for a skip shift... my pathetic excuse for an engine gets about 26 consistant with about 29 on the high way and thats using all 115 hp

PLYRS 3

steven, how?

based on your own quote, no, it doesn't - absolutely.

harryb92

During trip from NY to DC, vette gave us whopping 31 mpg crusing around 70~75 mph!! Quite amazing iin my opinion.

CrazyPhuD

Really???????....then perhaps you can explain why there are bills in congress to mandate change in the EPA testing methods. Perhaps you can explains why the EPA numbers for Hybrids almost never reflect real world results. Perhaps you can explain why the EPA itself is expected to create a new fuel economy standard?

http://www.mercurynews.com/mld/mercurynews...ve/11118730.htm

Not weighing in on Vetts/S2k just saying the EPA numbers rarely reflect the real world....

steve c

The means the EPA uses for measuring fuel economy is more accurate than you or I can ever reproduce.

More than 2 bucks, less than 20. GM dealers are known to throw out warranties if they catch you. You are projecting how you would drive the car onto other people. Once you get used to it, you never really notice it.

There is no trick. The car simply has enough torque that shifting from first to fourth is not an issue.

18/28 = 46/2 = 23 overall
20/25 = 45/2 = 22.5 overall

Again, we can look for loopholes and trick circumstances all day, but the reality is GM made a car capable of runnin 11's stock and getting nearly 30MPG on the highway. Meanwhile our S2000's are lucky to run 13's and get poorer fuel economy. So what. Is the size of your Johnson wrapped up in what mileage you get?

PLYRS 3

only b/c i love yanking your chain ........

but seriously, steven...you're just one big walking contradiction.

steve c

Which bills?

We are not talking about hybrids here.

? You are making some rather broad brush statements with no real data to back them up.

Below is how the EPA claims to test for fuel economy. My money is on them to produce accurate and reproducable results, not me or anyone else driving around town ...

How are Vehicles Tested?
Vehicles are driven over identical driving patterns by professional drivers in controlled laboratory conditions on a dynamometer, which is like a treadmill for cars. The conditions that occur during driving, such as wind drag and inertia are accounted for on the dynamometer. There are two types of tests that are conducted: city and highway tests.

The city test is approximately 11 miles long and simulates a stop and go trip with an average speed of about 20 miles per hour (mph). The trip lasts 31 minutes and has 23 stops. About 18 percent of the time is spent idling (as in waiting for traffic lights). A short freeway driving segment is included in the test. The engine is initially started after being parked overnight.

The highway simulates a 10 mile trip with an average speed of 48 mph. The vehicle is started "hot" and there is very little idling and no stops.

How Are the Label Estimates Calculated?
Fuel economy estimates are calculated from the emissions generated during the tests using a carbon balance equation. We know how much carbon is in the fuel, so by precisely measuring the carbon compounds expelled in the exhaust we can calculate the fuel economy.

After the vehicles have been tested, the results are adjusted downward to account for conditions that occur on the road that can affect fuel economy which don't occur during laboratory testing, such as cold temperature, aggressive driving, excessive use of power-hungry accessories, among others. The city is adjusted downward by 10 percent, and the highway by 22 percent.
The equation for calculating the city or highway average fuel economy, given in miles per gallon (mpg), is:

FEave = (total sales / [(sales1/FE1)+ (sales2/FE2) + ...+ (salesn/FEn)]

The calculation for combined fuel economy weights the city at 55 percent and the highway at 45 percent using the following equation:

FEcomb = 1 / (( .55 / city FE) + (.45 / hwy FE))