Better gas mileage at higher rpms, true or not?
04-30-2005, 02:54 AM
#26
Anatomy of a corner...
Originally Posted by MX6_2_RX8
Has everybody lost their minds? What does peak horsepower have to do with peak efficiency? Peak horsepower means that it can burn the MOST fuel and turn it into power. Frictional losses & heat losses go up with RPM. When fuel is ignited it does two main things, it makes the car move and it makes waste heat that needs to be dissipated by the radiator. For arguments sake lets say you are going 80mph in 3rd at 8000 RPM vs going 80mph in 6th at about 4000rpm. The speed is the same so the energy needed to move the car is the same. BUT at 8000 RPM you are heating up the combustion chamber twice as many times! There are of course dozens of other factors but that is probably one of the biggest. You could make the same argument with friction. The owner’s manual recommends shift points for cruising that are around 2700 RPM. I’d probably start looking for peak efficiency there.
Car salesmen don’t always know what they are talking about, plain and simple. I would also be careful about believing everything you read on this forum.
edit.. Forgot to mention the extra heat going out the exhaust. Duh.
Car salesmen don’t always know what they are talking about, plain and simple. I would also be careful about believing everything you read on this forum.
edit.. Forgot to mention the extra heat going out the exhaust. Duh.
FS
04-30-2005, 03:43 AM
#28
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The simplest way to enjoy good milage out of the 8 is not to look at the fuel guage. As the old adage says "what the eye doesnt see the heart doesnt grieve about" Try too hard to squeeze more mpg and you just wasting the experience.
However on a more useful note, 4 things that have improved my mpg are:
1. don't drive too conservatively (trying too hard seems to make it worse) use 2nd and 3rd gears regularly keeping between 3500 - 4750 rpm, doesnt greatly effect mpg and does increase driving pleasure.
2. crisp efficent gear changes - dont depress the clutch all the way down and then ride it on the way back up whilst feeding the accelator, in an effort to keep the change smooth. Learn where it bites and dip in and out short, fast(er) but smoothly and you wont even notice the gear change. Over a tank of petrol you'll notice the difference once you've mastered efficient gear changes.
3. Euro unleaded 95 just doesnt work at all (splutters and falters at 6500 as the 3rd ports open and generally feels strained) and disapperas faster than a glass of good wine, and 100 seems more efficient than 98 (but mine is a type S JDM so that might be why it prefers 100 octane)
4. I used to have a normal 1.6si corolla and always used to floor it in every gear. Wide Open Throttle is very rarely necessary with the 8 from a bangs-for-your-bucks point of view. 60-75% open throttle makes a deal of difference to the mpg. Don't stomp on the accelarator pedal either feed in quick and smooth for better accelaration and mpg
However on a more useful note, 4 things that have improved my mpg are:
1. don't drive too conservatively (trying too hard seems to make it worse) use 2nd and 3rd gears regularly keeping between 3500 - 4750 rpm, doesnt greatly effect mpg and does increase driving pleasure.
2. crisp efficent gear changes - dont depress the clutch all the way down and then ride it on the way back up whilst feeding the accelator, in an effort to keep the change smooth. Learn where it bites and dip in and out short, fast(er) but smoothly and you wont even notice the gear change. Over a tank of petrol you'll notice the difference once you've mastered efficient gear changes.
3. Euro unleaded 95 just doesnt work at all (splutters and falters at 6500 as the 3rd ports open and generally feels strained) and disapperas faster than a glass of good wine, and 100 seems more efficient than 98 (but mine is a type S JDM so that might be why it prefers 100 octane)
4. I used to have a normal 1.6si corolla and always used to floor it in every gear. Wide Open Throttle is very rarely necessary with the 8 from a bangs-for-your-bucks point of view. 60-75% open throttle makes a deal of difference to the mpg. Don't stomp on the accelarator pedal either feed in quick and smooth for better accelaration and mpg
04-30-2005, 06:28 AM
#29
A nice step up!!!
Originally Posted by fullsmoke
Per unit gas, per unit power produced. Else why wouldn't every engine just dump in a bunch of extra fuel and air into every RPM (provided the engine wouldn't die out)?
FS
FS
I think the best analogy would be to think of moving a stack of bricks from one pile to another. (Doing work)
Low RPM - You could do a lot of work with a little movement and move the whole pile at once but you wouldn't have enough power to do it. (lugging)
Optimum RPM - you could take a few at a time 5, 8, 10 whatever you were comfortable with based on your strength, build and other factors.
High RPM - You could take one at a time very quickly and easily but there would be so much other work going back and forth that that wouldn't be the best way.
I know I'll probably get flamed because it isn't a perfect analogy but I think it kind of gets the point across.
I think this horse is dead.
04-30-2005, 02:40 PM
#31
Originally Posted by SDRacer87
False! At higher RPM's you burn more fuel, faster.
04-30-2005, 05:59 PM
#32
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I tend to agree with Vip_C. We shouldn't even be having this conversation. Getting an RX-8 and then complaining about gas mileage is almost as absurd as getting an RX-8 and complaining that it doesn't handle well off-road. This is a SPORTSCAR, not a Prius!
04-30-2005, 06:35 PM
#33
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Originally Posted by SDRacer87
False! At higher RPM's you burn more fuel, faster.
as I have proven in another thread, the best efficiency is 3200-3400 rpms, which coincidently corresponds to 6th gear at 65mph and 5th gear at 55mph
05-01-2005, 02:59 AM
#35
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Originally Posted by Vip_C
What the f**k???
The 8 is a guzzler, get use to it!
I wouldn't drive mine like a pansy to get an extra 10/20 miles out of a full tank,
Drive it how you like..
The 8 is a guzzler, get use to it!
I wouldn't drive mine like a pansy to get an extra 10/20 miles out of a full tank,
Drive it how you like..
peeps always poppin up threads to gain an extra mile... i dont know why?
everyone buys this car knowing very well about rotaries (especially the mileage, from the RX7)
its a sports car the last thing on your mind should have been mileage.. if you want a economical car go buy a toyota..
and dont bother getting technical on me because you get 16-17mpg when the sticker says 18mpg... i dont really care and those peeps need to lighten up and drive, appreciate the car for its HORRible mileage or simply get rid of it and buy a corolla!
05-01-2005, 09:15 AM
#36
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Originally Posted by agoodcave
Sorry, but fuel is not potential energy (g*z). It is internal energy.
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