Fuel econemy question
in [Technical]
|
Prev: Suggestions from your experience organizing metric & englishc...
Next: anyone have an old Trico catalog?
From: E. Meyer on 6 Jul 2010 11:57 On 7/5/10 10:42 PM, in article ib95361v126e4f9msaaovpehaaa7o2i9eh(a)4ax.com, "Jesse" <sumin(a)telus.net> wrote: > I had a discussion with a pal about comparing vehicle fuel economy. > Would a 6 Cylinder at 65 MPH showing 2200 RPM use less fuel than a 4 > cylinder showing 2600 RPM at 65 MPH? The simple part of the calculation is the six cylinder will fire its sparkplugs (and therefore burn gas) 13,200 times in a minute and the 4 cylinder will spark 10,400 times. So, IF they are both injecting the same amount of gas into each cylinder, then the 4 cylinder should use less gas. The missing piece here is that the amount of gas being injected is not specified for either engine, so you can't solve the problem analytically, even if you have them running in a controlled environment (e.g. Windtunnel) without more information.
From: C. E. White on 6 Jul 2010 15:22 "Jesse" <sumin(a)telus.net> wrote in message news:ib95361v126e4f9msaaovpehaaa7o2i9eh(a)4ax.com... >I had a discussion with a pal about comparing vehicle fuel economy. > Would a 6 Cylinder at 65 MPH showing 2200 RPM use less fuel than a 4 > cylinder showing 2600 RPM at 65 MPH? There are way to many variables to properly answer this questions. Do the engines have the same displacement? What sort of valve train? Compression ratio? Why are you running the four faster? Bearing sizes, ring type/tension, intake tract efficiency, exhaust design, etc. all effect the results. Maybe you should ask if all things are equal, would a x size 6 cylinder consume more fuel than the same size four cylinder at a given speed. Even that is uncertain, although I would expect the four cylinder to do slightly better (if in truth all things were equal, including gearing). Ed
From: chuckcar on 6 Jul 2010 17:24 "C. E. White" <cewhite3(a)mindspring.com> wrote in news:i0vvoa$298$1(a)news.eternal-september.org: > > "Jesse" <sumin(a)telus.net> wrote in message > news:ib95361v126e4f9msaaovpehaaa7o2i9eh(a)4ax.com... >>I had a discussion with a pal about comparing vehicle fuel economy. >> Would a 6 Cylinder at 65 MPH showing 2200 RPM use less fuel than a 4 >> cylinder showing 2600 RPM at 65 MPH? > > There are way to many variables to properly answer this questions. > > Do the engines have the same displacement? > What sort of valve train? > Compression ratio? > Why are you running the four faster? And not in a ratio 6/4 either begging questions of the power and ratios on the vehicles. However the bottom line in fuel economy is the feet on the other side of the firewall. -- (setq (chuck nil) car(chuck) )
From: Jesse on 7 Jul 2010 16:05 On Tue, 6 Jul 2010 12:14:52 +0000 (UTC), Tegger <invalid(a)invalid.inv> wrote: >Jesse <sumin(a)telus.net> wrote in news:ib95361v126e4f9msaaovpehaaa7o2i9eh@ >4ax.com: > >> I had a discussion with a pal about comparing vehicle fuel economy. >> Would a 6 Cylinder at 65 MPH showing 2200 RPM use less fuel than a 4 >> cylinder showing 2600 RPM at 65 MPH? >> > > >I think the question is impossible to answer as a generic thing; there are >too many variables. > >What are the characteristics of each engine and each car? How much power is >being created by each engine, and where in their rev-range? How heavy is >each car? How much wind-resistance has each car? How much throttle-opening >is required to maintain speed in each car? Perhaps I should clarift my situation. The discussion followed an attempt to select a car for my daughter, she prefers good milage. I drove both cars on the same road, at the same speed and observed at 65 MPH the 4 cyl at 2700 rpm and the 6 cyl at 2200 rpm. The question was which car should get the best fuel economy at these conditions. Neither myfriend or I know.
From: jim on 7 Jul 2010 16:22
Jesse wrote: > > On Tue, 6 Jul 2010 12:14:52 +0000 (UTC), Tegger <invalid(a)invalid.inv> > wrote: > > >Jesse <sumin(a)telus.net> wrote in news:ib95361v126e4f9msaaovpehaaa7o2i9eh@ > >4ax.com: > > > >> I had a discussion with a pal about comparing vehicle fuel economy. > >> Would a 6 Cylinder at 65 MPH showing 2200 RPM use less fuel than a 4 > >> cylinder showing 2600 RPM at 65 MPH? > >> > > > > > >I think the question is impossible to answer as a generic thing; there are > >too many variables. > > > >What are the characteristics of each engine and each car? How much power is > >being created by each engine, and where in their rev-range? How heavy is > >each car? How much wind-resistance has each car? How much throttle-opening > >is required to maintain speed in each car? > > Perhaps I should clarift my situation. The discussion followed an > attempt to select a car for my daughter, she prefers good milage. I > drove both cars on the same road, at the same speed and observed at 65 > MPH the 4 cyl at 2700 rpm and the 6 cyl at 2200 rpm. The question was > which car should get the best fuel economy at these conditions. > Neither myfriend or I know. ` ` The federal fuel economy numbers will probably be more accurate way to compare the two cars than asking strangers to guess based on the number of cylinders and RPM. -jim |