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bad fuel economy?

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Old 09-17-06, 01:30 PM
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bad fuel economy?

Im not sure about this, because to be honest i really dont drive the car that much, but i think i have a problem.

I fileld my car up with petrol the other day, and ive driven 60 miles since. Albeit 60 pretty hard miles, its 60 miles. My fuel gauge? Just over half now.

This isnt normal is it? What could cause this?

car has about 6k on a rebuild with a new o2 sensor (although my air pump was not working for unknown amount of time so could be plugged up)

car stinks pig rich at idle, but always has done. Not smelled any other sevens though to see if thats unusual.

What could be causing this?
Old 09-17-06, 01:32 PM
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miles or kilometers?
Old 09-17-06, 02:16 PM
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miles dude, read the post!
Old 09-17-06, 02:20 PM
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How about some more info as well. What mods have you done to the car, what kind of driving (stop and go with some nice aggressive redlight to redlight?) type stuff.

Tim
Old 09-17-06, 02:27 PM
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The fuel gauge is meaningless! Go fill up and see how many gallons you have actually burned through. Troubleshooting 101....
Old 09-17-06, 02:57 PM
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Originally Posted by rynberg
The fuel gauge is meaningless! Go fill up and see how many gallons you have actually burned through. Troubleshooting 101....

Yeah, my gas gauge usually reads about a quarter tank low.
Actually, the gauges on my other cars(Outback and Sienna) aren't very accurate either. I usually know what kind of mileage I get, so I read the trip meter to get a more meaning feeling about how much gas I have left.
Old 09-17-06, 03:33 PM
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you did say 60 pretty hard miles. sounds about right to me. if im on my car for 60 hard miles a half tank is about right.
Old 09-17-06, 03:39 PM
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How many gallons does the tank hold anyway? I put 18 in it one day and thought that it was probably bone dry.

I always warm the car up before I drive it, so 10 minutes of sitting every time I start it (if it needs warmed up that is) burns up a good amount of gas. But I didn't buy it to save on fuel....or anything for that matter.
Old 09-17-06, 03:44 PM
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Originally Posted by spandy
How many gallons does the tank hold anyway? I put 18 in it one day and thought that it was probably bone dry.
About 20 gallons. I try not to let it get below 1/4 tank.
Old 09-17-06, 04:29 PM
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I get about 10 mpg with average driving on my new engine. So you are about right. I think the mileage drops into the singe digits with a bit of "aggressive" driving.
Old 09-17-06, 06:41 PM
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Originally Posted by spandy
I always warm the car up before I drive it, so 10 minutes of sitting every time I start it (if it needs warmed up that is) burns up a good amount of gas. But I didn't buy it to save on fuel....or anything for that matter.
Never figured this one out. IT'S A CAR. You start it and drive it. It isn't an exotic F1 car. Mazda designed a very nice system (save the 3k AWS) to make the car run great when cold. You're not doing anything "nice" for the car, you're just burning gas.

To the original poster - it's impossible to tell if you have a mileage problem as of yet. You have to go through a whole tank, fill up, and do the math. The sender for the gas gauge might be funny, etc. - too hard to tell.

BTW, I drive my car for work (yes, no kidding) every day, and typically get around 18 mpg mixed city/highway driving. I usually get low 20's on an interstate trip.

Dale
Old 09-17-06, 11:37 PM
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Define "hard miles".

I get about 24 mpg cruising on the interstate and just over 4 mpg on the track.
Old 09-18-06, 06:44 AM
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Hard miles...well, i've been out for a few blasts, which typically involve first second and halfway though 3rd WOT, a bit of hard cornering, and some cruising inbetween (let her cool down)

Ive also been having fun in some large car parks etc....i guess ill just wait till she's empty and see how many miles i get to the tank when i fill up.

Sorry about the vagueness of my question! I should really put my mods in my sig :S (none really)
Old 11-01-06, 12:46 AM
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Gadd 24 hwy? What is your secret?
Old 11-01-06, 01:17 AM
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exhaust overheat

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Originally Posted by Seattle7
Gadd 24 hwy? What is your secret?
25mpg here. Full bolt ons and PFC.
Old 11-01-06, 02:15 AM
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Originally Posted by windom
25mpg here. Full bolt ons and PFC.
im new, what is PFC?
Old 11-01-06, 02:18 AM
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exhaust overheat

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Originally Posted by Seattle7
im new, what is PFC?
Apex'i powerFC ECU, it's a standalone.
Old 11-01-06, 02:26 AM
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plug and play? mmk. and have you had it tuned by a pro? oh **** mines an automatic too. ugh nevermind im screwed
Old 11-01-06, 02:57 AM
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exhaust overheat

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No, tuned by me. But on the stock map it comes with, designed for stock boost and bolt ons, I got a steady 25MPG on the way back from NC (1300miles).
Old 11-01-06, 03:05 AM
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Yeah, aftermarket ECU is pretty key for gas mileage. My car came with an M2 Stage III ECU, and I managed almost 25mpg with that. I cracked 25mpg going down to SoCal for Sevenstock (that was hitting ~140mph a few times too), and on the way back up I got my mileage up to 27mpg. Never downshifting while on the highway seems to be the trick, along with a stock-port engine, and fresh spark plugs/wires. I think I might be able to get close to 30mpg by switching to stock wheels and leaning out the PFC a little for cruising, but I'll have to pop in a wideband to be sure i can go any leaner.


edit: enough bragging. Do you know the condition of your primary injectors? Maybe they're leaking, causing the rich idle? I dunno, you should also check how your spark plugs look if you haven't looked at that already. Do you have a boost gauge, any other info on how the car is for normal driving?
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