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Is my engine fooling me?? (MPG thread)


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18 replies to this topic

#1 crazyman03

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Posted 11 December 2012 - 11:34 PM

So, I'm pretty sure my car is faking me out with MPG. Every time i put a new air filter in, I get awesome mileage. I'll get 20.. 21ish MPG, put a new filter in and get about 22,23ish. Not a huge jump, but still an improvement.

So, to attempt to help the situation, I installed an after market "high-flow" air filter, and the first complete tank of gas i got almost 24MPG out of it - mixed driving, mostly stop/go city (I drive all over repairing copiers). My driving habits havent changed.. I feather-hypermile the throttle like crazy.


Is there such thing as too much hypermiling? I have been babying the throttle a lot more to get every bit more of mileage i can get.. is it too much?


I thought, maybe I'm crazy, so I started tracking my mileage last month on fuelly. It doesnt reflect my fillups with the older "stock" filters. I filled my tank again just tonight.. Its the first full tank after my last full tank which i got almost 24mpg.

Maybe I'm trying too hard and its working harder to run??

my fuelly acct: http://www.fuelly.co...zyman03/impreza


My air filter:
Posted Image

Ideas?

-Justin

Edited by crazyman03, 11 December 2012 - 11:38 PM.


#2 cal_look_zero

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Posted 11 December 2012 - 11:55 PM

That type of intake will act as a "hot air intake" which will lower hp but increase mpgs.

#3 Subaru_dude

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Posted 11 December 2012 - 11:55 PM

My sisters 1996 Legacy sedan auto EJ22 gets 26 in mixed driving, she did manage a tad over 30 once on the interstate. She doesn't really pay a whole lot of attention to how she drives but she certainly isn't a lead foot. Her drive to work is a total of MAYBE 6 miles, with 6 redlights if I remember correctly, and it's nearly flat. Her and the bf take her car everywhere being he drives a truck, and if they go anywhere it's into the city to go eat or watch a movie. I would think your Impreza would get at least what her Legacy gets. You got a check engine light on? Maybe hypermiling doesn't work well with automatics...

#4 Fairtax4me

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Posted 11 December 2012 - 11:57 PM

95-96 ej22? What trans? Awd?

I don't know that those hot air intake filters help much but a new filter will certainly work better than an old dirty one. You'd be better off from a power standpoint to put the stock airbox back and use a high flow drop in filter like Fram. Stay away from oiled filters as they can gunk up the MAF sensor element.

Hypermiling I don't know much about, but going easy on the throttle and up shifting sooner will save you a little bit of gas. Simple things like plugs wires and fuel/air filters can make a difference in engine power. And dont foget about the pcv valve.
24 all city is not bad though.

#5 1 Lucky Texan

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Posted 12 December 2012 - 12:26 AM

the only downsides I can dream up from hypermiling might be from 'lugging' the engine. that 'could' lead to higher localized temps, higher pressure on bearings, maybe even increased carbon deposits. Whether this happens in real life and how severe any effects are - I dunno.

just speculation

#6 CoupedUpSubie

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Posted 12 December 2012 - 07:58 AM

24 mpg in the city isn't bad. I imagine if you went on a longer drive without many stops you would be around 28 or so. I pulled the silencer(white pipe in your fender by the filter) and left the stock airbox with a K&N filter. I clean it every now and then but make sure it is fairly dry before it goes back in. An oiled filter is fine if you properly oil it. If your worried about the MAF getting dirty buy a can of cleaner for it and keep it in the car.

#7 crazyman03

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Posted 12 December 2012 - 08:23 AM

That type of intake will act as a "hot air intake" which will lower hp but increase mpgs.



Yea, I now that works that way.. Eventually I was thinking of making a cold air box for it. I did get the nose of the filter into the air duct so it'll pull more from there..

It is a ej22 automatic with the awd works.

I realize that different people have views of these filters. But I would think that if I got 24ish mpg, if I were to continue driving the same way, I should get somewhere near the same right?

It seems do do this with any filter I put in. I get great mileage with the first full tank after installing, then **ppft** back down to 20/21ish..



-Justin

#8 bulwnkl

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Posted 12 December 2012 - 08:46 AM

my fuelly acct: http://www.fuelly.co...zyman03/impreza


Looks to me like the 24mpg fill-up is the anomaly (if there could be one from just 4 tanks). By far the most likely explanation for that is that the tank didn't get filled quite as full on that tank, so mpg calculated higher. The next tank 'evened things out' and so mpg calculated lower.

#9 86BRATMAN

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Posted 12 December 2012 - 09:26 AM

Personally, after reading about the hypermiling. I think thats a little ridicoulous. I've been around quite a few ej's in my days. And even with my heavy footed late teenage years I never got less than 23mpg. The 98 legacy L, auto, with 200k+ miles that we sold about 3 years ago averaged 25 in town and 29-31 highway. I've never bought into the silly fads for increasing mpg.

#10 Gloyale

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Posted 12 December 2012 - 11:30 AM

Those Spectre flilters suck. Even the K+N ones are not so good for engine.

"high flow" = poor filtration. Dust and dirt will get in and waer out the rings....then the milage will really suck.

You are way better off with a new paper filter.

Change your 02 sensor. Biggest contributor to mileage in my opinion.

#11 Nbe1210

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Posted 12 December 2012 - 11:54 AM

I installed a new front 02 sensor on my 97 legacy brighton and my mpgs went up about 2-3. The sensors are pretty cheap on Amazon , <$60, and easy to get to from under the hood. I had to run the car for a few minutes to heat it up and get the old one out but the whole thing took about 25 minutes to replace.

http://www.amazon.co...ils_o00_s00_i00

#12 forester2002s

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Posted 12 December 2012 - 04:30 PM

I keep track of my gasoline purchases, and enter them into a spreadsheet.
It is then easy to plot gas consumption.
(I love graphs - give me set of numbers, and I'll plot a graph).

The figures from each gas fill are not much help; they jump all over the place, based on how much fuel actually goes into the top of the tank.

So I plot a 5-fill moving average; I average out the fuel consumption from the the previous 5 fills, and I plot that. The graph is now fairly smooth, and one can detect long-term changes to consumption. Most of my driving is in and around the city, but on longer trips I can see the improvement quite clearly on the graph.

I bought this car new, and 10-years and 190,000-km later, the fuel consumption really hasn't changed significantly over time.

Edited by forester2002s, 12 December 2012 - 04:33 PM.


#13 sario

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Posted 12 December 2012 - 11:03 PM

I keep track of my gasoline purchases, and enter them into a spreadsheet.
It is then easy to plot gas consumption...



I've also plotted my MPG for years. I'm not really sure why I do it. My wife thinks It makes me a huge dork.

#14 crazyman03

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Posted 13 December 2012 - 08:59 AM

I've also plotted my MPG for years. I'm not really sure why I do it. My wife thinks It makes me a huge dork.


Haha! My wife says e same thing! She also laughs when I get excited when we get good mileage. She also yells at me when we go on toad trips and I want to set the cruise at 68.. "The speed limit is 75! You can set it on 80 and be done with it!" Lol

Anyway, I'm going to keep an eye through fuelly. I have been myself.. If you look in my glove box you'll find recipts with miles and mpg written on all of them. It just seemed to me that whenever I put a new air filter in, it would fake me out and give me great mileage. I'm going to try the o2 sensor next. It makes a bit of sense about what it's doing.


-Justin

#15 heartless

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Posted 13 December 2012 - 09:14 AM

1990 Legacy LS wagon, EJ22, AWD, 4EAT, currently has a tad over 230,000 on the clock, northern half of Wisconsin...Most of my driving is country roads, with some city driving thrown in (I live 10 miles from anything, 15 miles to "small town" & 30 miles to the nearest town of any size)

Summer average - 28-29 mpg average, mixed driving

Winter average - drops to 24-25 mpg average, mixed driving. factoring winter blend gas, and extended warm-up periods, this about right.

Not a huge "lead-foot" but dont putz around like grandma, either.

I did break the 30mpg barrier once, during a freeway run. :D

#16 ivans imports

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Posted 13 December 2012 - 11:56 AM

all ej subarus seem to average 300kms on 30 $ consistatly give er take

#17 sario

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Posted 14 December 2012 - 09:18 AM

I looked at my records. The last 6 air filter changes didn't affect the MPG on my EJ25. I change my filter about once a year or so. I'm not sure if that means anything though.

#18 crazyman03

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Posted 14 December 2012 - 02:44 PM

By far the most likely explanation for that is that the tank didn't get filled quite as full on that tank, so mpg calculated higher. The next tank 'evened things out' and so mpg calculated lower.


Yea, my fill-ups vary because my fuel gauge doesn't work correctly half the time. Fr example, the last fill, I was at 1/16th of a tank for a while. I need to look at h sending unit at some point. The times where I spent 12 gallons worth, either I had no monies, or the gauge was telling me different. (It varies abut 1/4 of a tank sometimes dropping and raising randomly..





-Justin

#19 bulwnkl

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Posted 14 December 2012 - 05:57 PM

I'm not talking about anything to do with the gauge. I'm talking about how the tank is filled by the pump, which is to do with a combination of the pump, the nozzle, and your vapor recovery system. You don't get _exactly_ the same degree of fill every time, even if you use the same nozzle from the same pump at the same station. Changing any of those variables essentially assures you a different fill level. Watch things over a few tanks before getting too excited one way or the other.




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