How can I get better mileage?
05-10-05, 03:06 PM
#26
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Originally Posted by Icemark
I usually do around 17-18 myself in my tweaked vert.
O2 is only good for increasing gas mileage at idle.
SAFC pretty much only increases gas mileage above 4000 RPM (and on a non turbo).
Good (and often replaced) sparkplugs, regular oil changes, keeping RPMs under 4000, clean air filter, clean cats, proper tune (you'd be surprised at what a bad BAC, idle mixture set, and timing and TPS off can do to mess up mileage), clean fuel filters (both tank and in-line), clean injectors, all can help increase mileage.
O2 is only good for increasing gas mileage at idle.
SAFC pretty much only increases gas mileage above 4000 RPM (and on a non turbo).
Good (and often replaced) sparkplugs, regular oil changes, keeping RPMs under 4000, clean air filter, clean cats, proper tune (you'd be surprised at what a bad BAC, idle mixture set, and timing and TPS off can do to mess up mileage), clean fuel filters (both tank and in-line), clean injectors, all can help increase mileage.
05-10-05, 03:29 PM
#27
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Originally Posted by MechE00
Drive safe on the street. 
Autocross >> on-street jack-assery
Autocross >> on-street jack-assery
it's true, "pushing" your car on the street usually means going WOT. that's all, big deal, who cares. that's nothing compared to autocrossing.
and I am dying to run on an open track!
05-10-05, 03:35 PM
#29
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Steps to avoid nusty gas consuption:
-Buy new injectors
-Pray to God
-Place an egg between the gas petal and the floor- Try not to brake it
-Lock the car, use it only once at 3 days
-Buy new injectors
-Pray to God
-Place an egg between the gas petal and the floor- Try not to brake it
-Lock the car, use it only once at 3 days
05-10-05, 03:36 PM
#30
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I get 17 - 17.5 mpg FULL city driving, haven't even tested highway because I never use it with any of my commutes.
It's easy to get good gas mileage, even with a modded engine. My engine is recently rebuilt and ported by me, full exhaust, CAI, alum flywheel/good clutch, underdrive main pulley, advanced timing, bla bla bla. I am also untuned still, running all this off the stock original (read uncleaned) injectors, TII fuel pump, and no tuning.
I found that weight reduction as well as a full tuneup can really help mpg. I have around 230 to 250 lbs taken off my car with full interior minus storage bins, and have done a full tuneup. The thing that helped me the most was tweaking the idle and resetting the TPS. I've also been running with my O2 sensor not working (wire melted on the header, still haven't fixed that) and my mpg didn't change noticeably.
It's easy to get good gas mileage, even with a modded engine. My engine is recently rebuilt and ported by me, full exhaust, CAI, alum flywheel/good clutch, underdrive main pulley, advanced timing, bla bla bla. I am also untuned still, running all this off the stock original (read uncleaned) injectors, TII fuel pump, and no tuning.
I found that weight reduction as well as a full tuneup can really help mpg. I have around 230 to 250 lbs taken off my car with full interior minus storage bins, and have done a full tuneup. The thing that helped me the most was tweaking the idle and resetting the TPS. I've also been running with my O2 sensor not working (wire melted on the header, still haven't fixed that) and my mpg didn't change noticeably.
05-10-05, 04:07 PM
#33
Lives on the Forum
Originally Posted by Icemark
O2 is only good for increasing gas mileage at idle.
Rotaries behave differently than a reciprocating piston popper. The inherent design acts somewhat like a flywheel. In other words, discounting wind resistance, cruising at 3500 rpms will actually net better mileage than cruising at 3000. Don't argue with me on this point, either, I've driven the same 100 mile round trip back and forth to work for over 5 years now, 95% of it highway (70 mph+). When it rains, or for any other reason I have to drive slower than normal for a day, the gas mileage actually goes DOWN.
I've also heard several guys here say they get better mileage cruising at, say 80 than at 70 on long trips, which proves my theory, notwithstanding the fact I've proved it to myself time and time again, just in case y'all think I'm nuts
05-10-05, 04:31 PM
#34
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To summarize, I think you mean that since a rotating rotar has less wasted energy instead of a full 180 degrees of it (such as a boinger). The momenum of a rotating rotar will be higher at higher rpms, thus causing less power and ,subsequently, less fuel to push the car at the same speed. The problem then comes when you push the car faster; an exponential amount of extra fuel and power is required the faster you need to go. In conclusion, constant speeds = better gas milage. Constant acceleration = worse milage. Thus highway and city mpg variations, respectively.
05-10-05, 04:34 PM
#35
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Originally Posted by WAYNE88N/A
Wha???
Rotaries behave differently than a reciprocating piston popper. The inherent design acts somewhat like a flywheel. In other words, discounting wind resistance, cruising at 3500 rpms will actually net better mileage than cruising at 3000. Don't argue with me on this point, either, I've driven the same 100 mile round trip back and forth to work for over 5 years now, 95% of it highway (70 mph+). When it rains, or for any other reason I have to drive slower than normal for a day, the gas mileage actually goes DOWN.
I've also heard several guys here say they get better mileage cruising at, say 80 than at 70 on long trips, which proves my theory, notwithstanding the fact I've proved it to myself time and time again, just in case y'all think I'm nuts
Rotaries behave differently than a reciprocating piston popper. The inherent design acts somewhat like a flywheel. In other words, discounting wind resistance, cruising at 3500 rpms will actually net better mileage than cruising at 3000. Don't argue with me on this point, either, I've driven the same 100 mile round trip back and forth to work for over 5 years now, 95% of it highway (70 mph+). When it rains, or for any other reason I have to drive slower than normal for a day, the gas mileage actually goes DOWN.
I've also heard several guys here say they get better mileage cruising at, say 80 than at 70 on long trips, which proves my theory, notwithstanding the fact I've proved it to myself time and time again, just in case y'all think I'm nuts
05-10-05, 04:45 PM
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Originally Posted by 1990RXHeaven
To summarize, I think you mean that since a rotating rotar has less wasted energy instead of a full 180 degrees of it (such as a boinger). The momenum of a rotating rotar will be higher at higher rpms, thus causing less power and ,subsequently, less fuel to push the car at the same speed.
The oscillation of the piston mass is not an energy loss mechanism assuming rigid, frictionless components. Making up "rotaries are really different!" myths is not really a good thing.
Who knows, I'm kinda preoccupied right now, so maybe I'm missing something you guys are saying that actually makes some sense in physics terms..
05-10-05, 05:38 PM
#37
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Originally Posted by MechE00
Drive safe on the street.
Find a local autocross club. Autocross >> on-street jack-assery.. Track driving is another good driving thrill that doesn't cause the same legal/ethical problems.
Find a local autocross club. Autocross >> on-street jack-assery.. Track driving is another good driving thrill that doesn't cause the same legal/ethical problems.
05-10-05, 05:56 PM
#38
Former Moderator. RIP Icemark.
Originally Posted by WAYNE88N/A
Wha???
Rotaries behave differently than a reciprocating piston popper. The inherent design acts somewhat like a flywheel. In other words, discounting wind resistance, cruising at 3500 rpms will actually net better mileage than cruising at 3000. Don't argue with me on this point, either, I've driven the same 100 mile round trip back and forth to work for over 5 years now, 95% of it highway (70 mph+). When it rains, or for any other reason I have to drive slower than normal for a day, the gas mileage actually goes DOWN.
I've also heard several guys here say they get better mileage cruising at, say 80 than at 70 on long trips, which proves my theory, notwithstanding the fact I've proved it to myself time and time again, just in case y'all think I'm nuts
Rotaries behave differently than a reciprocating piston popper. The inherent design acts somewhat like a flywheel. In other words, discounting wind resistance, cruising at 3500 rpms will actually net better mileage than cruising at 3000. Don't argue with me on this point, either, I've driven the same 100 mile round trip back and forth to work for over 5 years now, 95% of it highway (70 mph+). When it rains, or for any other reason I have to drive slower than normal for a day, the gas mileage actually goes DOWN.
I've also heard several guys here say they get better mileage cruising at, say 80 than at 70 on long trips, which proves my theory, notwithstanding the fact I've proved it to myself time and time again, just in case y'all think I'm nuts
An O2 sensor will have very very little effect on gas mileage.
And yes steady state driving at highway/freeway/tollway speeds will get you better mileage, but the minute you get above the 2ndaries kicking in (3800-4000 RPM) your mileage will go down.
But again, not sure what point you are trying to make.
05-10-05, 06:53 PM
#39
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Well, for starters you stated that the O2 sensor saves gas at idle. We're not in closed loop at idle, therefore the O2 sensor is not even used (although its input is still there at the ECU)...
For people like me that drive mostly highway, an O2 sensor has a BIG affect on gas mileage. Don't believe me? Get to the ECU, put a meter on the O2's input, and go for a long cruise- what you'll see a couple of seconds into a stable throttle position is the O2 sensor's output voltage oscillating between .4 and .5 volts... This is the ECU scheduling fuel at the stoich point.
Now disconnect the O2 sensor, and perform the same tests. What you'll see now is voltage a considerable amount beyond that .1v stoich range. In fact, it runs about .6 to .7v and bounces around wildly.... Which means you're using more gas. Which means your gas mileage is not as good as it would be if the sensor was connected.
My point- that you're wrong about the O2 sensor at idle statement...
For people like me that drive mostly highway, an O2 sensor has a BIG affect on gas mileage. Don't believe me? Get to the ECU, put a meter on the O2's input, and go for a long cruise- what you'll see a couple of seconds into a stable throttle position is the O2 sensor's output voltage oscillating between .4 and .5 volts... This is the ECU scheduling fuel at the stoich point.
Now disconnect the O2 sensor, and perform the same tests. What you'll see now is voltage a considerable amount beyond that .1v stoich range. In fact, it runs about .6 to .7v and bounces around wildly.... Which means you're using more gas. Which means your gas mileage is not as good as it would be if the sensor was connected.
My point- that you're wrong about the O2 sensor at idle statement...
05-10-05, 08:17 PM
#40
... or plug a test LED into the O2 sensor check pin of the diagnostic connector (at least on an S4... no clue about the S5, but I imagine there's something similar).
From my research on O2 sensor behavior (both with the light & with the SAFC hooked to the O2 sensor input), the following are true on a S4 engine.
The O2 sensor is not used at idle. Idle is quite rich.
The O2 sensor is not used during most driving. Anything involving noticeable acceleration will be in open loop mode, and quite rich.
The O2 sensor *is* used in steady state cruising, but only up to 3500 RPM. It's very easy to hit the gas hard enough to knock the ECU back into open loop mode (and you can actually hear the difference in engine sound if you're listening for it), and the cruise control will repeatedly knock the ECU into open loop mode going up hills.
The O2 sensor is no longer used past 3500 RPM. As you gently accelerate (in closed loop) through 3500 RPM, the O2 sensor flips to rich and stays there.
When doing sustained 100mph+ runs (on... uh... tracks), fuel economy blows. You can practically watch the fuel gauge drop. Cops also don't like the "I was just testing out some engine repairs" excuse.
As for higher cruise speeds, I've found that my fuel economy is down since my speeding ticket - I cruise at 75 or so instead of my previous 85. It seems the engine gets significantly more efficient as you crank closer to 3500 RPM, but going above that will lead to an immediate loss of fuel economy as the ECU is in open loop mode.
I can't speak for the S5. Someone else can talk about those, but I'll stand behind my results when discussing S4 NAs.
-=Russ=-
From my research on O2 sensor behavior (both with the light & with the SAFC hooked to the O2 sensor input), the following are true on a S4 engine.
The O2 sensor is not used at idle. Idle is quite rich.
The O2 sensor is not used during most driving. Anything involving noticeable acceleration will be in open loop mode, and quite rich.
The O2 sensor *is* used in steady state cruising, but only up to 3500 RPM. It's very easy to hit the gas hard enough to knock the ECU back into open loop mode (and you can actually hear the difference in engine sound if you're listening for it), and the cruise control will repeatedly knock the ECU into open loop mode going up hills.
The O2 sensor is no longer used past 3500 RPM. As you gently accelerate (in closed loop) through 3500 RPM, the O2 sensor flips to rich and stays there.
When doing sustained 100mph+ runs (on... uh... tracks), fuel economy blows. You can practically watch the fuel gauge drop. Cops also don't like the "I was just testing out some engine repairs" excuse.
As for higher cruise speeds, I've found that my fuel economy is down since my speeding ticket - I cruise at 75 or so instead of my previous 85. It seems the engine gets significantly more efficient as you crank closer to 3500 RPM, but going above that will lead to an immediate loss of fuel economy as the ECU is in open loop mode.
I can't speak for the S5. Someone else can talk about those, but I'll stand behind my results when discussing S4 NAs.
-=Russ=-
05-10-05, 08:21 PM
#41
Former Moderator. RIP Icemark.
Originally Posted by WAYNE88N/A
Well, for starters you stated that the O2 sensor saves gas at idle. We're not in closed loop at idle, therefore the O2 sensor is not even used (although its input is still there at the ECU)...
For people like me that drive mostly highway, an O2 sensor has a BIG affect on gas mileage. Don't believe me? Get to the ECU, put a meter on the O2's input, and go for a long cruise- what you'll see a couple of seconds into a stable throttle position is the O2 sensor's output voltage oscillating between .4 and .5 volts... This is the ECU scheduling fuel at the stoich point.
Now disconnect the O2 sensor, and perform the same tests. What you'll see now is voltage a considerable amount beyond that .1v stoich range. In fact, it runs about .6 to .7v and bounces around wildly.... Which means you're using more gas. Which means your gas mileage is not as good as it would be if the sensor was connected.
My point- that you're wrong about the O2 sensor at idle statement...
For people like me that drive mostly highway, an O2 sensor has a BIG affect on gas mileage. Don't believe me? Get to the ECU, put a meter on the O2's input, and go for a long cruise- what you'll see a couple of seconds into a stable throttle position is the O2 sensor's output voltage oscillating between .4 and .5 volts... This is the ECU scheduling fuel at the stoich point.
Now disconnect the O2 sensor, and perform the same tests. What you'll see now is voltage a considerable amount beyond that .1v stoich range. In fact, it runs about .6 to .7v and bounces around wildly.... Which means you're using more gas. Which means your gas mileage is not as good as it would be if the sensor was connected.
My point- that you're wrong about the O2 sensor at idle statement...
This will give you a ball park figure (that should not be confused with real scientific testing- because you may have minor differnces in filling amount), but still give you a ball park idea.
I bet you a 6 pack at Sevenstock this year that there will be only the most absolute minor differences if any.
Infact I bet, if you disconnect the 5th gear (over the top ) switch, it will have more of an effect on mileage than the O2 sensor
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Last edited by Icemark; 05-10-05 at 08:26 PM.
05-10-05, 08:30 PM
#43
Icemark: If your commute to work is mostly city driving, then the O2 sensor won't do anything, because the ECU is spending barely any time in closed loop mode.
A better test would be to do the same thing but on the highway... say, a 60 mile round trip. You'll see a difference.
-=Russ=-
A better test would be to do the same thing but on the highway... say, a 60 mile round trip. You'll see a difference.
-=Russ=-
05-10-05, 08:32 PM
#44
I think I'm addicted
wow... now there's a bet i want to see.......
Icemark vs Wayne....
but honestly, i come to accept my poor gas mileage.... turbo and all....
but there are some things u can do (i think it is more significant on turboIIs though)
before i got a crane Hi-6 CDI i got like 16-HIGH 17 mpg MAX but after i got that... the first tank driving 65 mph constantly 95% freeway i got 20mpg, now a race and hard accel here and there i get constant 18 mpg....
since i drive freeway alot, i plan to do an e-fan conversion and also change the O2 (its old anyways) see if that makes alot of difference.... but 21mpg is great in my point of view.... as alot of members here say.... if u want something with better gas mileage, go get a civic and don't put a MONSTROUS spoiler on it... then you are done...
^_^ if u decide to do that can u sell your FC to me? i wouldn't mind having a 21 mpg NA
that can be my weekday car =D
Icemark vs Wayne....
but honestly, i come to accept my poor gas mileage.... turbo and all....
but there are some things u can do (i think it is more significant on turboIIs though)
before i got a crane Hi-6 CDI i got like 16-HIGH 17 mpg MAX but after i got that... the first tank driving 65 mph constantly 95% freeway i got 20mpg, now a race and hard accel here and there i get constant 18 mpg....
since i drive freeway alot, i plan to do an e-fan conversion and also change the O2 (its old anyways) see if that makes alot of difference.... but 21mpg is great in my point of view.... as alot of members here say.... if u want something with better gas mileage, go get a civic and don't put a MONSTROUS spoiler on it... then you are done...
^_^ if u decide to do that can u sell your FC to me? i wouldn't mind having a 21 mpg NA
that can be my weekday car =D
05-10-05, 08:34 PM
#45
Lives on the Forum
Look Mark, I'm not arguing just to argue here, and I'm not out to prove you wrong...I've done the exact same tests Russ is talking about above your last post, and come to the very same conclusions. Very impressive, BTW, Russ, I thought I was the only one interested enough to track all of our ECU inputs, lol...
And Mark, I have driven with a bad O2 sensor input, so there's no need to do it again and repeat my earlier testing...And it does affect gas mileage, in a bad way. Remember I drive almost exclusively highway. City drivers will not notice this, probably, which is where your point of view coming from, I'm sure...
I get VERY accurate gas mileage estimates, just because of the fact that I only drive the car to work, along the same route, and it's almost exactly 100 miles round trip. When I fill up, the odo reads 300.4 miles every time. And I fill her up all the way to the neck. Last fillup netted 27.2 mpg (as its getting warmer out, mileage goes up, I was doing 26.7 or so for the previous couple of cold months). And that's romping on her at least once a trip (gotta get on the freeway, right?)
And Russ- I know how you feel- I gotta slow down because of all the cops too...
And Mark, I have driven with a bad O2 sensor input, so there's no need to do it again and repeat my earlier testing...And it does affect gas mileage, in a bad way. Remember I drive almost exclusively highway. City drivers will not notice this, probably, which is where your point of view coming from, I'm sure...
I get VERY accurate gas mileage estimates, just because of the fact that I only drive the car to work, along the same route, and it's almost exactly 100 miles round trip. When I fill up, the odo reads 300.4 miles every time. And I fill her up all the way to the neck. Last fillup netted 27.2 mpg (as its getting warmer out, mileage goes up, I was doing 26.7 or so for the previous couple of cold months). And that's romping on her at least once a trip (gotta get on the freeway, right?
)And Russ- I know how you feel- I gotta slow down because of all the cops too...
05-10-05, 08:34 PM
#46
I think I'm addicted
Originally Posted by seven1997
My sons 88SE averaged 25 to 26mpg on the highway. 750 mile trip last week, Portland Oregon to Rigby Idaho. Has 148000 miles , original engine and the only mod is a Borla Catback with Bonez free flow catalytic converter.
? How'd he do that? i want to know how to get 25-26mpg
05-10-05, 08:41 PM
#47
Lives on the Forum
Originally Posted by Cybaster
since i drive freeway alot, i plan to do an e-fan conversion and also change the O2 (its old anyways) see if that makes alot of difference....
05-10-05, 08:44 PM
#48
Former Moderator. RIP Icemark.
Originally Posted by WAYNE88N/A
That's a very good idea- I don't even turn my e-fan on until a mile before I get to work, when I gotta get off the freeway and hit a couple of lights. She runs about 1/3 gauge the whole way when it's 85*F out or so, with no fan at all on...You'll see about .5 mpg more or so when you take the stock fan off, if you mostly drive highway and leave the e-fan off...
Since you need to be going at least 45 to just be in 5th gear, you should never have problems with cooling.
05-10-05, 08:46 PM
#49
Lives on the Forum
Originally Posted by Icemark
Infact I bet, if you disconnect the 5th gear (over the top ) switch, it will have more of an effect on mileage than the O2 sensor
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And, my ACV isn't at all active anymore on my car, so the split air solenoid will have no affect on my mileage
05-10-05, 08:48 PM
#50
Former Moderator. RIP Icemark.
Originally Posted by WAYNE88N/A
You'll lose that bet- the 5th gear switch doesn't "activate" the O2 sensor, in fact you can drive in closed loop in 4th gear also. Hailers also knows this, because he's the one that made me prove this to myself to settle a little "civil discussion" we were having. I lost that one, lol...
And, my ACV isn't at all active anymore on my car, so the split air solenoid will have no affect on my mileage
And, my ACV isn't at all active anymore on my car, so the split air solenoid will have no affect on my mileage