| Author |
Message |
Guest
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 Posted:
Fri Nov 04, 2005 9:17 am Post subject:
vibe/matrix gas mileage problems |
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I just got a 2003 Vibe, 5 speed, with 27K miles. Great car! However,
for the last two tanks of gas (since I bought the car), I've been
averaging only 26 miles per gallon. Mostly, but not entirely, city
driving. That's with a K&N air filter, which increased the mileage of
my Camry by 2-3mpg.
EPA says the manual transmission base Vibe is supposed to get 30/36mpg.
What might be wrong? Why would a Vibe get worse mileage than a Camry
(98, 5-speed, CE) under the same driving conditions? (I'm not hauling
any extra weight, not drag racing, tires are inflated, etc.) Would the
dealer take me seriously if I brought it in and complained? (It's
still under warranty)
I'd appreciate any opinions or shared experience.
Thanks,
Andy
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Guest
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| Posted:
Fri Nov 04, 2005 9:17 am Post subject:
Re: vibe/matrix gas mileage problems |
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Ed, If you read my original post, you'll note that I have a 5 speed
manual transmission, BASE model Vibe. The "Sports" model is called the
GT, and it has a 6-speed manual transmission.
Also, regardless of calculations, gas formulations, number of tanks
calculated, or whatever, the fact remains that my Camry has never
gotten less than 27mpg (usually 33+mpg highway), when the EPA says it
should get 23/32, and my Vibe has never gotten more than 26, when the
EPA says 30(or 29)/36. Both manual transmissions, same calculations,
same gas, same commute, and (as close as I can tell) same driving. I
know the EPA estimates are not necessarily real-world scores, so let me
restate the question:
Why is my Camry 20% above the EPA city estimate, while my Vibe is 10%
below? Did their estimates really change that much in 5 years?
I wondered also about the odometer being off - how often does an
odometer "go bad"? I did put on new tires, but I calculated the
circumference to be within 1cm of the old tires, which should change
the odometer reading by half a percent or less. I'll try to test the
odometer by driving the same route in both cars and comparing readings.
Regarding the K&N air filter, I did calculate mileage over several
tanks of gas both before and after I installed the filter on my Camry,
and mileage was consistently at least 2mpg better after. If that means
there was something wrong with my old air filter, so be it. In that
case, there also must have been something wrong with the old air filter
on my mother's '00 Camry, and my father's '03 F150, because mileage on
both of those vehicles consistently increased as well after the
addition of K&N filters.
Andy |
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Ray O
Guest
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| Posted:
Fri Nov 04, 2005 9:17 am Post subject:
Re: vibe/matrix gas mileage problems |
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<andynewhouse@yahoo.com> wrote in message
news:1131083820.502673.137630@g14g2000cwa.googlegroups.com...
| Quote: | Ed, If you read my original post, you'll note that I have a 5 speed
manual transmission, BASE model Vibe. The "Sports" model is called the
GT, and it has a 6-speed manual transmission.
Also, regardless of calculations, gas formulations, number of tanks
calculated, or whatever, the fact remains that my Camry has never
gotten less than 27mpg (usually 33+mpg highway), when the EPA says it
should get 23/32, and my Vibe has never gotten more than 26, when the
EPA says 30(or 29)/36. Both manual transmissions, same calculations,
same gas, same commute, and (as close as I can tell) same driving. I
know the EPA estimates are not necessarily real-world scores, so let me
restate the question:
Why is my Camry 20% above the EPA city estimate, while my Vibe is 10%
below?
|
Keep in mind that without examining both vehicles and measuring results with
you driving on a dynamometer, all anyone can give you are guesses.
I'll give my guesses.
The odometer on one or both cars could be incorrect. Check accuracy by
using the mile markers on highways over a 5 or 10 mile stretch. Inaccuracy
can be caused by differences in tire diameter as well as by an internal
problem with the odometer. If I were to guess, I'd say that the Camry's
odometer is overstating miles traveled.
Another possibility is that the driving style that has resulted in very good
fuel mileage in your Camry does not neessarily work as well for the Matrix.
The Matrix has a smaller engine and so later shifts may be necessary to get
the same performance and/or fuel economy as the Camry because the Matrix's
engine is lugging a little bit.
Did their estimates really change that much in 5 years?
The methodology for determing fuel economy has not changed that much in the
past 5 years but I believe that it will change soon to more closely reflect
real-world dirving conditions and will probably result in lower fuel economy
estimates.
| Quote: | I wondered also about the odometer being off - how often does an
odometer "go bad"?
|
Very rarely in a Toyota. In fact, I have never run across one, although
accuracy can very as much as 10% over or under.
I did put on new tires, but I calculated the
| Quote: | circumference to be within 1cm of the old tires, which should change
the odometer reading by half a percent or less. I'll try to test the
odometer by driving the same route in both cars and comparing readings.
|
Try measuing the circumference of the tires instead of calculating them.
Your suggested test is a good one.
| Quote: | Regarding the K&N air filter, I did calculate mileage over several
tanks of gas both before and after I installed the filter on my Camry,
and mileage was consistently at least 2mpg better after. If that means
there was something wrong with my old air filter, so be it. In that
case, there also must have been something wrong with the old air filter
on my mother's '00 Camry, and my father's '03 F150, because mileage on
both of those vehicles consistently increased as well after the
addition of K&N filters.
Andy
K&N and other "high performance" air filters may improve fuel economy and |
performance, but bear in mind that in order to improve air flow, the
passages are not as fine so they have a tendency to allow more contaminants
to pass than a conventional filter. More contaminants means shorter engine
life and more frequent oil changes required. The filters that are soaked
with oil can also have an adverse affect on MAP/MAF sensors. For this
reason, I am not a fan of "performance" air filters for normal street use.
--
Ray O
correct the return address punctuation to reply
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C. E. White
Guest
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| Posted:
Fri Nov 04, 2005 9:17 am Post subject:
Re: vibe/matrix gas mileage problems |
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<andynewhouse@yahoo.com> wrote in message
news:1131075116.520496.238460@o13g2000cwo.googlegroups.com...
| Quote: | I just got a 2003 Vibe, 5 speed, with 27K miles. Great car! However,
for the last two tanks of gas (since I bought the car), I've been
averaging only 26 miles per gallon. Mostly, but not entirely, city
driving. That's with a K&N air filter, which increased the mileage of
my Camry by 2-3mpg.
EPA says the manual transmission base Vibe is supposed to get 30/36mpg.
What might be wrong? Why would a Vibe get worse mileage than a Camry
(98, 5-speed, CE) under the same driving conditions? (I'm not hauling
any extra weight, not drag racing, tires are inflated, etc.) Would the
dealer take me seriously if I brought it in and complained? (It's
still under warranty)
I'd appreciate any opinions or shared experience.
|
I suspect you need to take your data more carefully.. Unless there was
something horribly wrong with your Camry, there is no way a K&N filter
should have any measurable affect on fuel economy. Fuel injected engines are
not adversely affected by air filter restrictions like old carbureted cars
were. For a fuel injected car, there is very little difference as far as the
engine computer is concerned between a restricted air filter and a slightly
more closed throttle. K&N filters might (but probably don't) provide more
high end horsepower if the OE filter is poorly design, but there is no way
they are going to improve the mileage of a recent fuel injected vehicle by 2
to 3 miles per gallon (unless there was something horribly wrong with the OE
intake and filter).
Other possible reasons for lower than expected fuel economy include using
one of the various reformulated gasolines, dragging brakes, incorrect
odometer, poor mileage calculations. You need to record gas purchased for
multiple tank fulls and compute an overall average to get a reasonably
accurate estimate of your fuel economy. Single tank averages can be very
misleading. And finally, if you are doing mostly city driving, averaging 26
mpg versus an EPA estimate of 30 is not that unexpected. City mileage is
particularly dependent on driving style. Maybe the Vibe encourages spirited
driving? And exactly which model Vibe do you have? One 2003 sports model is
only rated 25 city / 30 highway (and requires premium fuel). And in fact
none of the 2003 Vibes are rated better than 29 / 36. So, you need to
verify your model. It is possible you are actually beating the EPA estimates
if you have a Sports model.
Ed |
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C. E. White
Guest
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| Posted:
Fri Nov 04, 2005 9:17 am Post subject:
Re: vibe/matrix gas mileage problems |
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"John Karpich" <`rocket9005@earthlink.net> wrote in message
news:mNAaf.1819$Y75.1420@fe06.lga...
| Quote: | andynewhouse@yahoo.com wrote:
I just got a 2003 Vibe, 5 speed, with 27K miles. Great car! However,
for the last two tanks of gas (since I bought the car), I've been
averaging only 26 miles per gallon. Mostly, but not entirely, city
driving. That's with a K&N air filter, which increased the mileage of
my Camry by 2-3mpg.
EPA says the manual transmission base Vibe is supposed to get 30/36mpg.
What might be wrong? Why would a Vibe get worse mileage than a Camry
(98, 5-speed, CE) under the same driving conditions? (I'm not hauling
any extra weight, not drag racing, tires are inflated, etc.) Would the
dealer take me seriously if I brought it in and complained? (It's
still under warranty)
I'd appreciate any opinions or shared experience.
Thanks,
Andy
If you have the defrost on all the time the AC is running too, if the
outside temp is over 32 F. That could kill your millage. I live in CT and
the past couple of mornings I've had to use the defrost to clear the
windows. I was used keeping on all winter long in my old Tercel.
|
The A/C compressor won't run if the temeprature is below approximately 40
degrees F even if you are in the defrost mode (even if the system normally
runs the A/C in defrost mode). At low temperatures the A/C cycle ceases to
work and the compressor is shut down.
Ed |
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Guest
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| Posted:
Fri Nov 04, 2005 9:18 am Post subject:
Re: vibe/matrix gas mileage problems |
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Thanks for the quick reply. I'm aware that the defrost automatically
kicks on the AC. Haven't been running the AC or defrost very much. My
main concern is that I've never gotten mileage this low in my Camry,
even loaded heavy with the AC on!
Andy |
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John Karpich
Guest
|
| Posted:
Fri Nov 04, 2005 9:18 am Post subject:
Re: vibe/matrix gas mileage problems |
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andynewhouse@yahoo.com wrote:
| Quote: | I just got a 2003 Vibe, 5 speed, with 27K miles. Great car! However,
for the last two tanks of gas (since I bought the car), I've been
averaging only 26 miles per gallon. Mostly, but not entirely, city
driving. That's with a K&N air filter, which increased the mileage of
my Camry by 2-3mpg.
EPA says the manual transmission base Vibe is supposed to get 30/36mpg.
What might be wrong? Why would a Vibe get worse mileage than a Camry
(98, 5-speed, CE) under the same driving conditions? (I'm not hauling
any extra weight, not drag racing, tires are inflated, etc.) Would the
dealer take me seriously if I brought it in and complained? (It's
still under warranty)
I'd appreciate any opinions or shared experience.
Thanks,
Andy
|
If you have the defrost on all the time the AC is running too, if the
outside temp is over 32 F. That could kill your millage. I live in CT
and the past couple of mornings I've had to use the defrost to clear the
windows. I was used keeping on all winter long in my old Tercel.
John |
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Guest
|
| Posted:
Fri Nov 04, 2005 3:19 pm Post subject:
Re: vibe/matrix gas mileage problems |
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Thanks for your guesses! I'll take them into consideration.
Andy |
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Philip
Guest
|
| Posted:
Fri Nov 04, 2005 9:56 pm Post subject:
Re: vibe/matrix gas mileage problems |
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Andy: When I bought my Corolla new back in 2003, it got considerably less
than EPA mileage for the first 2,000 miles. The car didn't start getting
close to EPA until it had 6k miles. And it wasn't until nearly 15k miles
that it would meet EPA mileage on occasion.
With the manual transmission, you DO need to limit engine rpm to no more
than 2500 and keep your foot out of the throttle to get those EPA mileage
figures.
--
- Philip
<andynewhouse@yahoo.com> wrote in message
news:1131083820.502673.137630@g14g2000cwa.googlegroups.com...
| Quote: | Ed, If you read my original post, you'll note that I have a 5 speed
manual transmission, BASE model Vibe. The "Sports" model is called the
GT, and it has a 6-speed manual transmission.
Also, regardless of calculations, gas formulations, number of tanks
calculated, or whatever, the fact remains that my Camry has never
gotten less than 27mpg (usually 33+mpg highway), when the EPA says it
should get 23/32, and my Vibe has never gotten more than 26, when the
EPA says 30(or 29)/36. Both manual transmissions, same calculations,
same gas, same commute, and (as close as I can tell) same driving. I
know the EPA estimates are not necessarily real-world scores, so let me
restate the question:
Why is my Camry 20% above the EPA city estimate, while my Vibe is 10%
below? Did their estimates really change that much in 5 years?
I wondered also about the odometer being off - how often does an
odometer "go bad"? I did put on new tires, but I calculated the
circumference to be within 1cm of the old tires, which should change
the odometer reading by half a percent or less. I'll try to test the
odometer by driving the same route in both cars and comparing readings.
Regarding the K&N air filter, I did calculate mileage over several
tanks of gas both before and after I installed the filter on my Camry,
and mileage was consistently at least 2mpg better after. If that means
there was something wrong with my old air filter, so be it. In that
case, there also must have been something wrong with the old air filter
on my mother's '00 Camry, and my father's '03 F150, because mileage on
both of those vehicles consistently increased as well after the
addition of K&N filters.
Andy
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Gord Beaman
Guest
|
| Posted:
Fri Nov 04, 2005 11:12 pm Post subject:
Re: vibe/matrix gas mileage problems |
|
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andynewhouse@yahoo.com wrote:
| Quote: | Thanks for the quick reply. I'm aware that the defrost automatically
kicks on the AC. Haven't been running the AC or defrost very much. My
main concern is that I've never gotten mileage this low in my Camry,
even loaded heavy with the AC on!
Andy
|
We've been tryin t'tell you Andy...Toyotas rule! :)
--
-Gord.
(use gordon in email) |
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Ray O
Guest
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| Posted:
Sat Nov 05, 2005 12:04 am Post subject:
Re: vibe/matrix gas mileage problems |
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<andynewhouse@yahoo.com> wrote in message
news:1131095942.542144.87000@z14g2000cwz.googlegroups.com...
| Quote: | Thanks for your guesses! I'll take them into consideration.
Andy
|
You're welcome!
--
Ray O
correct the return address punctuation to reply |
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C. E. White
Guest
|
| Posted:
Sat Nov 05, 2005 2:10 am Post subject:
Re: vibe/matrix gas mileage problems |
|
|
<andynewhouse@yahoo.com> wrote in message
news:1131083820.502673.137630@g14g2000cwa.googlegroups.com...
| Quote: | Regarding the K&N air filter, I did calculate mileage over several
tanks of gas both before and after I installed the filter on my Camry,
and mileage was consistently at least 2mpg better after. If that means
there was something wrong with my old air filter, so be it. In that
case, there also must have been something wrong with the old air filter
on my mother's '00 Camry, and my father's '03 F150, because mileage on
both of those vehicles consistently increased as well after the
addition of K&N filters.
|
So why did installing a K&N Air Filter result in the mileage increasing? How
does the engine tell the difference between the restriction of a paper air
filter + throttle plate and the restriction of a K&N air filter plus
throttle plate? With modern fuel injected engines, the amount of fuel
injected is adjusted by the PCM based on the oxygen sensor reading. If less
air gets into the engine less fuel will be injected. The amount of air
inducted into the engine is controlled by the air restriction in the intake
tract. This restriction is a combination of the air restrictions of the
intake tract, air filter, and throttle plate. If you lower the restriction
presented by the air filter, you'll just close the throttle a little more to
arrive at the same overall restriction. The PCM has no idea whether the
restriction is a result of the air filter or the throttle. There is no basis
to believe that a K&N filter should increase fuel economy for a modern
feedback controlled fuel injected engine. In the old days of carbureted
engines, air filter restrictions would affect fuel economy because the
increased restriction would act like a choke and richen the mixture.
So why do people report increases in fuel economy with K&N air filter. I
have a few theories:
1) Wishful thinking - they want it to show an improvement, so it does
2) Poor fuel economy measurement - most likely cause
3) Induction noise changes because of the change in filter and people drive
more slowly because they confuse noise with power
4) K&N was installed as part of a general tune-up
5) People modify their driving style after the installation because they
installed it as part of an overall desire to improve fuel economy
6) The reduced restriction does actually screw up the sensors and this
results in a leaner mixture which actually improves fuel economy. This seems
very unlikely unless things really get out of whack, The PCM should adjust
the fuel trim based on the O2 output, but I suppose minor improvement might
be possible - but certainly not the 10+% you are claiming. If Ford, or GM,
or Toyota thought they could increase fuel economy by 10% by just changing
air filters, they would. And they would not have to use a K&N to do it -
just a much larger paper filter. From calculations I have done in the past,
most US vehicles already come with air filter substantially larger than
necessary to provide a minimum air filter restriction. |
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Philip
Guest
|
| Posted:
Sat Nov 05, 2005 8:19 am Post subject:
Re: vibe/matrix gas mileage problems |
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|
"C. E. White" <cewhite3@mindspring.com> wrote in message
news:5fPaf.4196$2y.1993@newsread2.news.atl.earthlink.net...
snip
| Quote: | So why did installing a K&N Air Filter result in the mileage increasing?
How does the engine tell the difference between the restriction of a paper
air filter + throttle plate and the restriction of a K&N air filter plus
throttle plate? With modern fuel injected engines, the amount of fuel
injected is adjusted by the PCM based on the oxygen sensor reading. If
less air gets into the engine less fuel will be injected. The amount of
air inducted into the engine is controlled by the air restriction in the
intake tract. This restriction is a combination of the air restrictions of
the intake tract, air filter, and throttle plate. If you lower the
restriction presented by the air filter, you'll just close the throttle a
little more to arrive at the same overall restriction. The PCM has no idea
whether the restriction is a result of the air filter or the throttle.
There is no basis to believe that a K&N filter should increase fuel
economy for a modern feedback controlled fuel injected engine. In the old
days of carbureted engines, air filter restrictions would affect fuel
economy because the increased restriction would act like a choke and
richen the mixture.
So why do people report increases in fuel economy with K&N air filter. I
have a few theories:
1) Wishful thinking - they want it to show an improvement, so it does
2) Poor fuel economy measurement - most likely cause
3) Induction noise changes because of the change in filter and people
drive more slowly because they confuse noise with power
4) K&N was installed as part of a general tune-up
5) People modify their driving style after the installation because they
installed it as part of an overall desire to improve fuel economy
6) The reduced restriction does actually screw up the sensors and this
results in a leaner mixture which actually improves fuel economy. This
seems very unlikely unless things really get out of whack, The PCM should
adjust the fuel trim based on the O2 output, but I suppose minor
improvement might be possible - but certainly not the 10+% you are
claiming. If Ford, or GM, or Toyota thought they could increase fuel
economy by 10% by just changing air filters, they would. And they would
not have to use a K&N to do it - just a much larger paper filter. From
calculations I have done in the past, most US vehicles already come with
air filter substantially larger than necessary to provide a minimum air
filter restriction.
|
GOOD post, CE White! I agree with your 6 points.
--
- Philip |
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Todd
Guest
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| Posted:
Fri Nov 11, 2005 6:51 am Post subject:
Re: vibe/matrix gas mileage problems |
|
|
C. E. White wrote:
| Quote: |
So why did installing a K&N Air Filter result in the mileage increasing? How
does the engine tell the difference between the restriction of a paper air
filter + throttle plate and the restriction of a K&N air filter plus
throttle plate? With modern fuel injected engines, the amount of fuel
injected is adjusted by the PCM based on the oxygen sensor reading. If less
air gets into the engine less fuel will be injected. The amount of air
inducted into the engine is controlled by the air restriction in the intake
tract. This restriction is a combination of the air restrictions of the
intake tract, air filter, and throttle plate. If you lower the restriction
presented by the air filter, you'll just close the throttle a little more to
arrive at the same overall restriction. The PCM has no idea whether the
restriction is a result of the air filter or the throttle. There is no basis
to believe that a K&N filter should increase fuel economy for a modern
feedback controlled fuel injected engine. In the old days of carbureted
engines, air filter restrictions would affect fuel economy because the
increased restriction would act like a choke and richen the mixture.
So why do people report increases in fuel economy with K&N air filter. I
have a few theories:
|
Well, one thing you are forgetting (although you did mention it) is the
term "feedback system" (it's a reactive system, not proactive). So what
is it feeding back to? A hard coded fuel map based on throttle postion,
temperature, etc. Fuel injection is really not that far off from the
carbs of old (which is why there is little mileage improvement when you
compare most modern FI engine over their older carbed brethren). The
fuel map determines how much fuel at any given throttle position should
be injected and the feedback sensors (MAF/MAP and O2 and probably some
others like IAT) allow the computer to trim the fuel for emissions as
required. But the fuel map is what determines the injector pulses and
overall amount of fuel. So if a filter allows more air in, then that
"should" require less throttle. And at less throttle, the map is going
to assign less injector pulses and then trim from there. I'm guessing
the reason some people see improvements and others don't is more a
factor on how restrictive the factory intake setup is (twists, turns,
etc.) and maybe even whether the factory sized filter is adequate or
not. But the bottom line is many, many people report SOME type of
improvement overall in both power and mileage and I'd be hard pressed
to say they are all just imagining it. My conclusion would be that
there are some benefits to the filter, and each person must decide if
the cost is worth the gain.
I had an '81 350cid (5.7L) Chevy pickup that got 20mpg with a 4 barrel
carb and 3 speed tranny, yet my '04 262cid (4.3L) S10 with modern fuel
injection and a 4 speed tranny is lucky to see 18mpg on that same
highway...go figure.
Todd |
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