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Discussion Starter · #1 ·
I posted pick of how i modded my air box a few weeks back after people claimed to get outstanding results from such a simple project. It was almost too easy to try and cheap too. Just to sum up the project... I took off the snorkel, took out filter in the top of the air box, installed a K&N filter, installed the TRD cold air bumper inlet. Looked for an esthetically pleasing way to remove the silencer but never got around to it.
I drove around for a few weeks with this set up and i am not happy with the way it drives. IT does have better acceleration but I can not see how people got what they clam to have received in MPG... :mad:... I have actually decreased in MPG since this mod...This was the whole idea of the mod was to increase MPG... :(... But i have been thinking about it and i wanted to run these thoughts by others to make sure i am not too far off line. I have worked with several carbed race cars but with EFI and computers i am not up too par with as of yet
First, When you have a basically stock engine and exhaust and you increase the airflow past the mass air sensor this tells the computer to add more fuel to compensate. In the computers eyes it feels that the car is running too lean and wants to correct this action by increasing fuel output. Second, If i go back to the stock setup i will decrease air flow but it should restore my fuel milage back to the max that i was getting before due to fixing what the computer was reading as lean.
Just modding the intake does not seem to make sense for gas milage and i have to throw the bull **** flag when i see people say they are getting 31 MPG after doing something so simple. If it was that simple then i feel that the dealers would have it that way off the show room floor to meet the demands of what the auto industry is trying to establish with the MPG requirements.

ANY THOUGHTS OR IDEA WOULD BE GREAT TO SUPPORT MY THOUGHTS OR TO PROVE THEM WRONG...THANKS
 

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My sentiments exactly. More air means more fuel to compensate which means less mpg. All I did to my XB is install the TRD Sport exhaust really for looks and different sound.

I proved this with my friend's XB. He had an aftermarket CAI. At my request he took it off and installed the stock air filter assembly. His mpg's improved. He reinstalled the CAI because he missed the sound from the CAI.

While it is true you will get more power, you don't get it at take off. You will notice the gain in power at higher speed.

It all comes down to this...more hp means more fuel.

And like you said, if it was meant to have better mpg....SCION would have built it that way...
 

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In my opinion, it all comes down to how you drive. For most people, if they add a "performance" mod, they are going to regularly tickle it. The more throttle you apply, the less MPG you're going to see. The direct advantage I had with a CAI is the same amount of throttle provides more rapid acceleration -- also true with the other two engine mods I made. The result is, I no longer need to apply anywhere near the same amount of throttle to achieve the same response as OE. I'm not so sure a CAI allows MPG to improve over OE, but it definitely doesn't force it lower -- driving behavior does that :)!
 

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ai17828 said:
It all comes down to this...more hp means more fuel.
Actually, that's not necessarily true, it depends on how the greater HP is achieved. The key issue is turbulence and/or restriction of gas flow through the engine and manifolds. The harder the engine has to work to push/pull the gases though the system, the more fuel is being wasted. The easier it is for the engine to breath, the more HP can be realized from the same amount of fuel.
 

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Discussion Starter · #5 ·
I understand all points. But the truth comes down to what i am actually doing and the results that i have actually received.

Here is the breakdown to help you understand my driving habits. I live about 1.5 miles from my work. In the AM when i go to work it is bumper to bumper traffic for that 1.5 miles because of the Air Force base gate. When i am on base i drive less than 30 MPH EVEYWHERE... so there is no need to get to that speed too quickly... and i don't want to loose driving privileges. so i drive like a grandpa for 70% of the time i drive. So to give you actual number stats; i went from 270-285 miles per tank down to my gas light coming on at 235 miles for the tank on a regular basis.

The other 30% of the time i drive in regular traffic around town. I understand that the xB is not a drag car so i don't try to race it. It is about as aerodynamic as a wall. Some people don't understand that 4cylinder engines that are stock, like my xB, are SLOW AS HELL!!!

So to put it simple...it isn't my driving habits. I really don't think the tach has hit over 3,000 rpm more than a hand full of times. Mostly when going up a hill with cruise control on.


So these are my reasons for throwing the BS FLAG
 

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Still with you. ;)

The other day that I filled up my gas tank, I happened to look at the gage to see how many miles I had to go before I had to fill up after the reset and to my dismay it read at 248 miles. Am I really only getting 248 miles per tank? If that's true then that means I'm only getting 17.7 mpg!!! Or is the 248 miles inaccurate?
 

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ai17828 said:
Still with you. ;)

The other day that I filled up my gas tank, I happened to look at the gage to see how many miles I had to go before I had to fill up after the reset and to my dismay it read at 248 miles. Am I really only getting 248 miles per tank? If that's true then that means I'm only getting 17.7 mpg!!! Or is the 248 miles inaccurate?
Boy do you have a lead foot. If my math is correct, at 17.7 MPG and 248 miles you had to put in 14 gallons. At your MPG that works out to be 247.8 miles. You were on fumes as the tank only holds 14 gallons.
 

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As I clearly said above, I make no suggestion that your MPG should have increased from adding a CAI -- so please don't confuse me with anyone who might have suggested that. However, I do disagree that installing a CAI inherently reduces MPG (also clearly stated above).

My last fill up was 27.5 mpg and the elapsed distance was 330miles and I still had two gallons in the tank (I always calculate my numbers manually). My engine mods are a homemade CAI (first mod), a lightweight OE sized crank pulley (second mod), and a ported & polished Throttle Body (third mod). The car moves out pretty spryly when asked to (IMO :yes:)!

Driving conditions are mostly town with speeds varying from 20-28 mph on some roads and 30 to 38mph on others. There's plenty of time stopped at lights and zero highway miles -- very rare I get even near 55mph.

So, as I said, my guess is it's a driving issue.

PS. Just checked my records and I performed my CAI mod at about 100mi (picked up the car with a full tank at 70mi), and my first fill up was at 364 mi. The calculated gas mileage for that fill was 25.9 mpg.
 

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Don't forget guys! The reserve tank has 4 gallons so when your gas meter is on empty you should have 4 more gallons if i remember hearing correctly.
 

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gr8scape said:
ai17828 said:
Still with you. ;)

The other day that I filled up my gas tank, I happened to look at the gage to see how many miles I had to go before I had to fill up after the reset and to my dismay it read at 248 miles. Am I really only getting 248 miles per tank? If that's true then that means I'm only getting 17.7 mpg!!! Or is the 248 miles inaccurate?
Boy do you have a lead foot. If my math is correct, at 17.7 MPG and 248 miles you had to put in 14 gallons. At your MPG that works out to be 247.8 miles. You were on fumes as the tank only holds 14 gallons.
Incorrect. No lead foot. Just regular driving. The only mod I have is the TRD Sport exhaust.
 

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Parkers09xB said:
MenniFresh said:
Don't forget guys! The reserve tank has 4 gallons so when your gas meter is on empty you should have 4 more gallons if i remember hearing correctly.
Where did you hear this?
Looking at the gauge . . .
Several years of fill-ups for "tests" . . .
Basic Math . . .

Fill up just when hits "E." Put in 10 gallons of gas.
Do it again.

Several, then dozens of times putting approx. 10 gallons in when empty. Figure "hit E when need about 10 gallons.
Read manual to see "fuel capacity." It reads "14 gallons." Humm . . . maybe there is more in there . . .
Go WAY over "E" and light on, sweat "I'm gonna run out of gas in the middle of nowhere" (where I live, there is A LOT of "nowhere" in the middle of miles, miles, and miles of trees), and wonder how much could POSSIBLY be left . . .
Fill up, then only put in 12.5 gallons (the most I ever have).

SO . ..
14-10= approx. 4 gallon "reserve" when hit "E."

You know . . .
It seems like they designed that for college kids who wait till absolutely the last minute to add gas . . .
(As a safety margin, b/c actually running out w/ fuel injection alone is bad, so running out w/ a VVT-I engine is likely VERY bad.)
 

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Question on this same issue. When I top off with fuel, my gauge usually shows I have 248 miles to go on the tank once it's full. If my math is correct that means I'm getting 17.71 mpg. Does that sound about right? I've seen people claiming 25 mpg's and above...
 

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ai17828 said:
Question on this same issue. When I top off with fuel, my gauge usually shows I have 248 miles to go on the tank once it's full. If my math is correct that means I'm getting 17.71 mpg. Does that sound about right? I've seen people claiming 25 mpg's and above...
Are you looking at the 10 (when hits "E" and light comes on) or the 14 total?
The computer calculates miles to the "E." I've driven past "0" on the mile-to-go many times.
 

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14 total. I just looked at the window sticker (i kept it when I bought the car) and it states 22 street and 28 hwy but in smaller print it states that most drivers will see 18 mpgs street and 23 mpgs hwy. So how are these other xb2 owners claiming over 25mpgs?
 

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TartanJack said:
I've driven past "0" on the mile-to-go many times.
Really? I got it down to the "0" pulling into the gas station one night and was scared I was gonna run out when it hit the 1. Guess not. Haha

ai17828 said:
14 total. I just looked at the window sticker (i kept it when I bought the car) and it states 22 street and 28 hwy but in smaller print it states that most drivers will see 18 mpgs street and 23 mpgs hwy. So how are these other xb2 owners claiming over 25mpgs?
That's weird... My dashboard MPG calculator currently reads 20.6 MPG.

When I bought my xB (used), it said something like 24.4 MPG.
 

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Your 20.6 mpg indicates that TartanJack is correct. There are 4 gallons still in the tank after the gauge light turns on. If my gauges reads 248 miles to go at full tank. 248/14 gallons is 17.77 mpg but if you calculate this way 248/10(which TaranJack states is when the light goes on) then the mpg's are 24.8. Correct?
 

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ai17828 said:
Your 20.6 mpg indicates that TartanJack is correct. There are 4 gallons still in the tank after the gauge light turns on. If my gauges reads 248 miles to go at full tank. 248/14 gallons is 17.77 mpg but if you calculate this way 248/10(which TaranJack states is when the light goes on) then the mpg's are 24.8. Correct?
Correct. When my gas gauge light comes though, it usually says around 13 or 14 miles left on the Range meter. I guess this explains why TJ can drive past the "0 mile" range. I guess all these different meters aren't as helpful as I thought... Bummer.
 

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You are correct about the meters/gauges not being very helpful. My mpg gauge/meter fluctuates all the time so I don't go by that. I go by the fill-ups and see how many miles I've driven, etc. etc.
 
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