Highway Cruising RPM and Gas Mileage
06-04-2010, 09:18 AM
#1
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Highway Cruising RPM and Gas Mileage
I have read somewhere (another forum) that cruising at 4000-4200 rpm saves more gas than cruising at approximately 3500-3700 rpm. I was also talking to a fellow s2k owner and he said he heard the same thing from a Honda Tech. None of us have tested this before.
I also noticed that the car feels smoother cruising at about 4k rpm as opposed to 3k where it feels like the engine is working harder.. is it just me?
This seems really counter intuitive, I always thought cruising at higher RPMs means more gas is used.
Can anyone shed any light on this? Sorry if this has been discussed before, I did not find anything when I used the search function.
...also.. I heard VTEC was developed for saving gas, is this true? and how?
Thanks in advance!
Reference:
http://www.s2000.com/forums/engine-tech-dr...gear-ratio.html
I also noticed that the car feels smoother cruising at about 4k rpm as opposed to 3k where it feels like the engine is working harder.. is it just me?
This seems really counter intuitive, I always thought cruising at higher RPMs means more gas is used.
Can anyone shed any light on this? Sorry if this has been discussed before, I did not find anything when I used the search function.
...also.. I heard VTEC was developed for saving gas, is this true? and how?
Thanks in advance!
Reference:
http://www.s2000.com/forums/engine-tech-dr...gear-ratio.html
06-04-2010, 12:09 PM
#3
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Originally Posted by nartnailuj,Jun 4 2010, 11:57 AM
I notice that shifting is smoother when i shift at 4000k-4500k than around 3000k
06-04-2010, 12:11 PM
#4
Please read this thread: https://www.s2ki.com/forums/index.php?showtopic=793386
I posted a lot of ways to save gas and maximize gas mileage in it.
But in regards to better gas mileage on the highway with cruising RPM... I have heard similar things. And I believe I saw someone that had a Scangauge II hooked up to their S2000 reported that they got better gas mileage on the highway at 75-80 than they did at 65-70... which sounds counterintuitive but someone else speculated that it leans out the fuel more as it gets closer to the VTEC engagement window (5-6k RPM).
Anyone else have any info on this? I'll try to find the link for it.
I posted a lot of ways to save gas and maximize gas mileage in it.
But in regards to better gas mileage on the highway with cruising RPM... I have heard similar things. And I believe I saw someone that had a Scangauge II hooked up to their S2000 reported that they got better gas mileage on the highway at 75-80 than they did at 65-70... which sounds counterintuitive but someone else speculated that it leans out the fuel more as it gets closer to the VTEC engagement window (5-6k RPM).
Anyone else have any info on this? I'll try to find the link for it.
06-04-2010, 12:24 PM
#5
Originally Posted by Disgustipated,Jun 4 2010, 01:11 PM
someone else speculated that it leans out the fuel more as it gets closer to the VTEC engagement window (5-6k RPM).
Anyone else have any info on this? I'll try to find the link for it.
Anyone else have any info on this? I'll try to find the link for it.
06-04-2010, 12:47 PM
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Originally Posted by Disgustipated,Jun 4 2010, 03:11 PM
But in regards to better gas mileage on the highway with cruising RPM... I have heard similar things. And I believe I saw someone that had a Scangauge II hooked up to their S2000 reported that they got better gas mileage on the highway at 75-80 than they did at 65-70... which sounds counterintuitive but someone else speculated that it leans out the fuel more as it gets closer to the VTEC engagement window (5-6k RPM).
I'd be very interested in seeing this data.If it's true, it seems that the fuel map must lean out significantly as speed and revs increase. Consider that aerodynamic drag is 16% greater at 70 mph than at 65 mph, and it's 33% greater at 75 mph than at 65 mph, so that's quite a bit of increased resistance to be offset by a drop in the amount of fuel being injected. Plus, everything I've ever read on fuel consumption says mileage goes down once you get above 60-65 mph, primarily due to increasing aerodynamic drag. But YMMV
06-04-2010, 02:41 PM
#7
Originally Posted by s2kapow,Jun 4 2010, 01:47 PM
This sounds a bit bizarro to me I'd be very interested in seeing this data.
If it's true, it seems that the fuel map must lean out significantly as speed and revs increase. Consider that aerodynamic drag is 16% greater at 70 mph than at 65 mph, and it's 33% greater at 75 mph than at 65 mph, so that's quite a bit of increased resistance to be offset by a drop in the amount of fuel being injected. Plus, everything I've ever read on fuel consumption says mileage goes down once you get above 60-65 mph, primarily due to increasing aerodynamic drag. But YMMV
I'd be very interested in seeing this data.If it's true, it seems that the fuel map must lean out significantly as speed and revs increase. Consider that aerodynamic drag is 16% greater at 70 mph than at 65 mph, and it's 33% greater at 75 mph than at 65 mph, so that's quite a bit of increased resistance to be offset by a drop in the amount of fuel being injected. Plus, everything I've ever read on fuel consumption says mileage goes down once you get above 60-65 mph, primarily due to increasing aerodynamic drag. But YMMV
Check out this link, this guy uses a Scangauge II and claims "throttle position 14" is the sweet spot. He claims to get around 35-37 mpg avg on his S2000.
Here's the thread:
http://s2000.com/forums/engine-tech-drivet...eage-wtf-4.html
And here's the post specifically:
http://s2000.com/forums/engine-tech-drivet....html#post69873
1. Mods. Mostly "driver" mods, i.e. adjusting the way I drive. See below for breakdown. For the vehicle, I removed the pass seat (-weight), use a ScanGuageII, and have a front air dam and grill block.
2. Power. Can't notice a difference, it is still there when I need it...I just don't use it that much.
3. Lifetime...maintenance? Standard MY02 needs oil every few thousand miles, softtop replaced (rips). Lifetime...mileage? 34+ mpg last 90 days, but like I said, I used to get the same as everyone else, 23-24 mpg. Lifetime...miles? Just passed 134,000.
Mods. Most of the info you want is in the EM Garage at ecomodder.com (see above). I really don't have the time to do A-B-A tests, coastdown tests, etc, so I am relying on "mileage over time" to determine the effectiveness of the mods. A rough breakdown (again, details in the EM Garage):
23-24 mpg "normal" S2000 style driving
27-28 mpg cruise 75mph on highway (estimated)
30-31 mpg cruise 64mph on highway
32-33 mpg not using a/c (not using lights about 50% of the time)
36-37 mpg using ScanGauge to keep Thottle Position Sensor (TPS) at 14
so +5-7mpg by slowing down from 80mph to 64mph, then +2-3mpg by not using a/c or lights, then +3-4mpg by using SG to monitor TPS and maintain constant throttle. Also, engine off coast (down hills, before stoplights, etc) during my 400+ mile round trip commute usually gives me anywhere from 6 to 20 "free" miles.
2. Power. Can't notice a difference, it is still there when I need it...I just don't use it that much.
3. Lifetime...maintenance? Standard MY02 needs oil every few thousand miles, softtop replaced (rips). Lifetime...mileage? 34+ mpg last 90 days, but like I said, I used to get the same as everyone else, 23-24 mpg. Lifetime...miles? Just passed 134,000.
Mods. Most of the info you want is in the EM Garage at ecomodder.com (see above). I really don't have the time to do A-B-A tests, coastdown tests, etc, so I am relying on "mileage over time" to determine the effectiveness of the mods. A rough breakdown (again, details in the EM Garage):
23-24 mpg "normal" S2000 style driving
27-28 mpg cruise 75mph on highway (estimated)
30-31 mpg cruise 64mph on highway
32-33 mpg not using a/c (not using lights about 50% of the time)
36-37 mpg using ScanGauge to keep Thottle Position Sensor (TPS) at 14
so +5-7mpg by slowing down from 80mph to 64mph, then +2-3mpg by not using a/c or lights, then +3-4mpg by using SG to monitor TPS and maintain constant throttle. Also, engine off coast (down hills, before stoplights, etc) during my 400+ mile round trip commute usually gives me anywhere from 6 to 20 "free" miles.
here are other devices available - this is the only one I've used. It is an instant feedback device. There is no other way you can tell how moving a pedal a fraction of an inch translates to mpg savings. Literally. You can be cruising along, showing 32 mpg (assume a constant rate and load). Then let off a hair on the pedal...by staying the same or maybe giving up 1mph, the gauge will show an increase of 2-3 mpg. Again, this driving technique requires constant driver input/corrections
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06-04-2010, 02:56 PM
#8
I wouldn't necessarily trust instantaneous MPG on the Scangauge. I have a DashDyno SPD (basically upgraded Scangauge with bigger screen by same company) and the MPG feature is really just a derived calculation based on vehicle speed / (injector pulse width * RPM) reported over the OBDII interface.
In other words, it is relying on OBDII data, it can't magically determine the MPG. It is only as accurate as the OBDII parameters are, and I'm sure there are artifacts there (the pulse width being most suspect).
If he derived his MPG from empirical data (miles driven / gallons needed at next fill up), then the data would be interesting.
In other words, it is relying on OBDII data, it can't magically determine the MPG. It is only as accurate as the OBDII parameters are, and I'm sure there are artifacts there (the pulse width being most suspect).
If he derived his MPG from empirical data (miles driven / gallons needed at next fill up), then the data would be interesting.
06-04-2010, 03:22 PM
#9
Originally Posted by urBan_dK,Jun 4 2010, 03:56 PM
I wouldn't necessarily trust instantaneous MPG on the Scangauge. I have a DashDyno SPD (basically upgraded Scangauge with bigger screen by same company) and the MPG feature is really just a derived calculation based on vehicle speed / (injector pulse width * RPM) reported over the OBDII interface.
In other words, it is relying on OBDII data, it can't magically determine the MPG. It is only as accurate as the OBDII parameters are, and I'm sure there are artifacts there (the pulse width being most suspect).
If he derived his MPG from empirical data (miles driven / gallons needed at next fill up), then the data would be interesting.
In other words, it is relying on OBDII data, it can't magically determine the MPG. It is only as accurate as the OBDII parameters are, and I'm sure there are artifacts there (the pulse width being most suspect).
If he derived his MPG from empirical data (miles driven / gallons needed at next fill up), then the data would be interesting.
I also saw some interesting posts on ClubRSX... some guy claimed his Scangauge read that coasting in neutral uses less fuel than coasting in gear, clutch out with no throttle. Something about the RSX having a weird throttle positioning where the throttle always reads at least 8-10% throttle even with no gas applied! I can get the links to that for anyone interested, I wonder if the S2000 has the same problem? Would be neat to check.
06-04-2010, 03:27 PM
#10
I can tell you from my experience that coasting in gear will actually show a higher MPG (as much as 150 MPG from my experience) because the fuel is actually shut off when coasting in gear. If you are coasting in neutral, it uses exactly as much fuel as idling in order to keep the engine running.
Still, coasting in neutral is a better way to go for fuel economy because coasting in gear will decrease your speed much quicker due to the engine braking.
Still, coasting in neutral is a better way to go for fuel economy because coasting in gear will decrease your speed much quicker due to the engine braking.