best fuel shift points?
08-03-2004, 12:22 PM
#1
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Join Date: Jul 2004
Posts: 296
best fuel shift points?
with gas prices as it is (i pay about $2.20 for premium) wat are the optimum shift points for the best gas mileage? i get about 370mi/ tank, roughly 24mpg (96 gxe 5sp). is the higher gear always the best choice? at 40mph u can be in either 4 or 5 (for best economy). wat gear is better to be in at that point? i try to shift out by 3k in 1&2, and before even that in 3-5. i'd like to see what other people's input in this subject.
08-03-2004, 12:27 PM
#2
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Join Date: Feb 2002
Posts: 525
when im on E i shift around 2.5-3 . but since my knock sensor is dead as it is im filling regular for another week or so. florida tax cut is lovely, i paid 1.789 for gas at hess and its staying like that until august 31. yay!
08-03-2004, 12:45 PM
#3
Your engine is never going to get better mileage than when you are shifting at 2.5-3.0k rpms. You cannot get deep into the pedal when you are doing this either.
Other than that, there is nothing much you can do.
I cannot drive like that, because it would bore me to death.
I have tried it and you might save like a gallon to a gallon and a half. Not worth it in my book. I mean, it would be different if you were getting way worse gas mileage than that.
Other than that, there is nothing much you can do.
I cannot drive like that, because it would bore me to death.
I have tried it and you might save like a gallon to a gallon and a half. Not worth it in my book. I mean, it would be different if you were getting way worse gas mileage than that.
08-03-2004, 12:57 PM
#4
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Join Date: Jul 2004
Posts: 296
the main thing is that it costs me nearly 34$ to fill up my tank, and thats at least 2x a week. im burnin nearly 70$/week-1.5 weeks. and u got to add the 7$ car wash too. as long as i look good, so will my ride 
08-03-2004, 05:26 PM
#11
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Join Date: Aug 2003
Location: Cincinnati, Ohio
Posts: 641
Originally Posted by shmad
and u got to add the 7$ car wash too. as long as i look good, so will my ride
The $7 car wash?? You mean the automatic wash at the gas station?? Think about how many people use that wash every day, how dirty their cars are, and how much crap could get caught up in the spinners, and THEN decide if you want those dirty-*** brushes all over your Max. The same goes for the foaming brush at the spray gun wash - how many pebbles and shards of glass and other junk gets tied up in the brush? And how often do those brushes get cleaned? Ick ... if you want to get lazy about washing your car, please use a touch-free car wash.
08-03-2004, 08:10 PM
#16
How much gas is used has nothing to do with RPM. It has to do with how far down the gas pedal is pushed. For example, you will save more gas driving in 3rd gear@3500 RPM with 20% throttle than if you drive in 5th gear@2100 RPM with 30% throttle. The reason i used that example is because in certain cases cruising in a higher gear causes you to have to press the gas down more to maintain a certain speed than if you were in a lower gear at the same speed, thus using more gas. Hope that makes sense... 
08-03-2004, 08:36 PM
#17
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Originally Posted by wariow
if you want to save gas, just shift from first to 5th
The suggestions to shift at 2.5-3k are good. And use 5th gear when cruising as much as possible. But if you're going through hills and the engine is lugging in 5th, shift it down to 4th. Lugging causes you to use a much higher throttle position which may kick the engine into open-loop mode where it's running very rich and using more fuel when you could have just downshifted, maintained a lower throttle position, and kept the engine in lean/econo-friendly closed-loop mode. As per my OBD-II scanner, the engine will go from closed-loop to open-loop at anything over 30-35% throttle or so. So also try to accelerate as smoothly as possible.
08-03-2004, 08:36 PM
#18
i shift at 3.5 from 1st to 2nd and then 3 at 2nd then in 3rd i got up tp 10 mph over the limit then i just coast in neutral til the next traffic light. neutral is the best gear to be in when u want to save gas
08-03-2004, 08:49 PM
#20
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Originally Posted by IwANnAMaX96
How much gas is used has nothing to do with RPM. It has to do with how far down the gas pedal is pushed. For example, you will save more gas driving in 3rd gear@3500 RPM with 20% throttle than if you drive in 5th gear@2100 RPM with 30% throttle. The reason i used that example is because in certain cases cruising in a higher gear causes you to have to press the gas down more to maintain a certain speed than if you were in a lower gear at the same speed, thus using more gas. Hope that makes sense...
5th: 2100 rpm x 0.30 = 630
3rd: 3500 rpm x 0.20 = 700 oh oh
So 3rd is burning more fuel, BUT....
wtq @ rpm x gear ratio x throttle x final drive = approx thrust
160 wtq x 0.80 x 0.30 x 3.82 = 147 lbs thrust
175 wtq x 1.27 x 0.20 x 3.82 = 170 lbs thrust
3rd gear is also producing more thrust. You could backoff the throttle to about 17% for the same thrust in 3rd. Recalculating above, the 3rd gear burn rate is now 595 vs 630 in 5th which makes 3rd the more economical gear. BUT...this doesn't take into account friction, which will be higher at 3500rpm than 2100rpm, but it's good enough for our purposes here.
The point you were trying to make was good and correct, though. It's better to downshift and use a much lower throttle position than lugging the engine in a higher gear at a lower RPM with a higher throttle position.
08-03-2004, 09:05 PM
#21
Originally Posted by SteVTEC
Not necessarily. We can do a little informal fuel burn rate and thrust calculations here...
5th: 2100 rpm x 0.30 = 630
3rd: 3500 rpm x 0.20 = 700 oh oh
So 3rd is burning more fuel, BUT....
wtq @ rpm x gear ratio x throttle x final drive = approx thrust
160 wtq x 0.80 x 0.30 x 3.82 = 147 lbs thrust
175 wtq x 1.27 x 0.20 x 3.82 = 170 lbs thrust
3rd gear is also producing more thrust. You could backoff the throttle to about 17% for the same thrust in 3rd. Recalculating above, the 3rd gear burn rate is now 595 vs 630 in 5th which makes 3rd the more economical gear. BUT...this doesn't take into account friction, which will be higher at 3500rpm than 2100rpm, but it's good enough for our purposes here.
The point you were trying to make was good and correct, though. It's better to downshift and use a much lower throttle position than lugging the engine in a higher gear at a lower RPM with a higher throttle position.
5th: 2100 rpm x 0.30 = 630
3rd: 3500 rpm x 0.20 = 700 oh oh
So 3rd is burning more fuel, BUT....
wtq @ rpm x gear ratio x throttle x final drive = approx thrust
160 wtq x 0.80 x 0.30 x 3.82 = 147 lbs thrust
175 wtq x 1.27 x 0.20 x 3.82 = 170 lbs thrust
3rd gear is also producing more thrust. You could backoff the throttle to about 17% for the same thrust in 3rd. Recalculating above, the 3rd gear burn rate is now 595 vs 630 in 5th which makes 3rd the more economical gear. BUT...this doesn't take into account friction, which will be higher at 3500rpm than 2100rpm, but it's good enough for our purposes here.
The point you were trying to make was good and correct, though. It's better to downshift and use a much lower throttle position than lugging the engine in a higher gear at a lower RPM with a higher throttle position.
BTW the numbers i used were just examples. And you went ahead and threw them into equations
08-03-2004, 09:31 PM
#24
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Originally Posted by IwANnAMaX96
There are certain things in your explanation that I'm not understanding. Why does it matter what RPM the engine is running at, what the coefficient of friction is at those RPM's, and what gear you're in? You have to adjust the throttle position to account for all of those factors, so throttle position takes everything into account. Am i missing something?
2100 RPM in a 3.0L engine @ 30% throttle = 945 L/min of air
3500 RPM in a 3.0L engine @ 30% throttle = 1575 L/min of air
More air going into the engine means more fuel also since the ECU wants to maintain the same AFR at all times. The same throttle position and higher RPM = a higher rate of fuel consumption.
08-04-2004, 02:27 PM
#25
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Location: Cincinnati, Ohio
Posts: 641
Originally Posted by 95whitese
whats lugging?
08-04-2004, 02:36 PM
#26
Originally Posted by shmad
its all about the touch free car wash... i cant wash my car myself at my apartment
When I lived in an apt, I bought a 125' hose, and went out into the parking lot and washed it.
A lot of the apartments now evern have one of those wash-it-yourself things with the brush. You can use that at least for the spraying, and then just scrub it yourself.
Thats true... 
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