Gas mileage ?'s

[SIMPLETON]

I haven't posted on here in quite a while but I have a few questions/observations about fuel economy in my car.

the car: '02 WRX

I just got back from a long road trip where the average gas mileage was about 28-29 mpg doing mostly highways at about 65 or 70 mph occasionally flooring it to pass slow pokes.

this car has an Autometer boost guage. At 60 mph in 5th gear im pulling about 10-12 inches of vacuum. But at the same speed in 4th gear its about 15 in. of vac. There is about 500 rpm difference between them. Now as I under stand it the more vacuum you are pulling the less throttle you are using. And the less throttle you are using the less gas you are using.

So my main question is, is the rpm difference in 5th large enough to offset using more throttle than 4th to get better gas mileage?

[Niko_Fx]

It's been a while since I don't see you around man, nice car

29mpg sounds pretty good, I thought gas-mileage sucked big time on WRXs... But then again 65mph is the perfect speed to get the most out of your mpgs.

Can't answer your question, it's good to see you around though.

[baddabang]

Damn I only get 27 with a 2.2.

[Niko_Fx]

I got 35mpg last time I measured about a month ago. It included city and highway... Highway-only should give me even more than that, can't really complain about my pos Civic.

[SIMPLETON]

Originally Posted by Niko_Fx

It's been a while since I don't see you around man, nice car

29mpg sounds pretty good, I thought gas-mileage sucked big time on WRXs... But then again 65mph is the perfect speed to get the most out of your mpgs.

Can't answer your question, it's good to see you around though.

yeah I'm sure If I drove it around in the city's alot or more aggresively the mileage would probably go down a bunch.

It is thouroughly fast for me right now, so I cant really complain about the mileage. Plus it makes a great car to drive in the snow. Although it seems like ever since I got there hasnt been any

It's an awesome feeling when you hit 4500 rpm where it gets to the meat of its power. You floor it and it's like ....hmm this is pretty qui--DAMN

[drakkie]

Originally Posted by Niko_Fx

I got 35mpg last time I measured about a month ago. It included city and highway... Highway-only should give me even more than that, can't really complain about my pos Civic.

pwned 45-50 mpg or 1l:23km to 1l:25km without effort. 1l:18km when flooring it. Eat that you gas guzzlers

[70cuda88]

Originally Posted by drakkie

pwned 45-50 mpg or 1l:23km to 1l:25km without effort. 1l:18km when flooring it. Eat that you gas guzzlers

whats your top speed? like 45? ok just makin sure.

[2ndclasscitizen]

Originally Posted by drakkie

pwned 45-50 mpg or 1l:23km to 1l:25km without effort. 1l:18km when flooring it. Eat that you gas guzzlers

I do the same, but the difference of course being when I give it some stick I run sub 4 sec to 100km/h and 10sec 1/4s. Can your Alto do that?

[jediali]

Originally Posted by drakkie

pwned 45-50 mpg or 1l:23km to 1l:25km without effort. 1l:18km when flooring it. Eat that you gas guzzlers

I can see the advantage. I can get 30mpg overall generally but when im doing less im grinning for different reasons than fuel economy.

[henk4]

my car has this on board computer and it allows you to see how many kms you can do with what is left in the tank. Interestingly, when you start the car it computes the remaining km on the basis of your average mileage over a historically longer period. It is very interesting to actually see, while driving, that your range goes significantly up, if you keep your right foot under control...

[70cuda88]

my bmw has the same thing, but its pretty funny when its raining, and you spin the tires from stop signs for a second, it calculates you have gone further, faster so the miles go up.

[drakkie]

Originally Posted by 70cuda88

whats your top speed? like 45? ok just makin sure.

The speedo has been rather far beyond the 160 km/h where it ends. I estimate 180 km/h, take off 10% speedo error and you have about 160 real kilometers per hour. 140 is a nice cruising speed though, when it needs to go fast.

Originally Posted by 2ndclasscitizen

I do the same, but the difference of course being when I give it some stick I run sub 4 sec to 100km/h and 10sec 1/4s. Can your Alto do that?

About 9-10 seconds to the 100km/h right now with the current mods. Hope 5-6 seconds after the summer

[Bob]

Originally Posted by SIMPLETON

I haven't posted on here in quite a while but I have a few questions/observations about fuel economy in my car.

the car: '02 WRX

I just got back from a long road trip where the average gas mileage was about 28-29 mpg doing mostly highways at about 65 or 70 mph occasionally flooring it to pass slow pokes.

this car has an Autometer boost guage. At 60 mph in 5th gear im pulling about 10-12 inches of vacuum. But at the same speed in 4th gear its about 15 in. of vac. There is about 500 rpm difference between them. Now as I under stand it the more vacuum you are pulling the less throttle you are using. And the less throttle you are using the less gas you are using.

So my main question is, is the rpm difference in 5th large enough to offset using more throttle than 4th to get better gas mileage?

I like the WRX to answer your question, less throttle does not equal less fuel. Heavy throttle is actually more efficient than light throttle, as long as you stay at low rpm (and barring enrichment above a certain throttle threshold.)

Less fuel comes from less air, because your engine "decides" how much fuel to add based on the airflow into the engine.

What this basically means is that your engine is more efficient in 5th gear at that speed in two ways:
1. You're losing less energy to friction because the engine is rotating more slowly
2. Your more open throttle means that the engine is actually running more efficiently for the given amount of air entering the engine

[2ndclasscitizen]

Originally Posted by drakkie

Hope 5-6 seconds after the summer

Ha.

Ha ha ha.

AHAHAHAHAHAHAHAHAHAHAHAHA!

[RobPorsche]

I get 100mpg on my hog...and a whole lotta laughs too.