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Just wanted to verify about how ECU controls AFR.
So there's a korean guy at clubtuscani.com, which is the biggest tiburon forum in Korea.
He re-maps his own ECU and managed to get 230whp out of his tib with some mods that he did himself.
According to him, our ECU controls AFR constantly to be 14.7 with oxygen sensor feedback only when the throttle is below about 80% opened. If the throttle is opened wider than 80%, then AFR is controlled not according to any sensor's feedback but according to the MAP saved in the ECU. It is well known that our tib's default AFR is super rich and that's why the fuel mileage is low. But actually this is not entirely correct. The AFR on dyno graph seems to be super rich only because they floor the throttle to measure the horsepower and the AFR is adjusted according to the MAP already setup in the ECU. So basically, our cars have a bad MAP when the throttle is almost fully opened. ECU remapping means remapping this MAP, but not modifying the AFR by sensors' feedback.

Adding mods such as intake and exhaust would not lean out the AFR when we normally drive because of sensors' feedback. So we won't experience that much of a difference in MPG. But it will lean out the super rich AFR by the MAP when we accelerate hard, so we will experience increased horsepower and better MPG.
Now if this is true, it makes sense that driving habits really matter.

For those who have 07 and 08 have a picky ECU, Modding intake could result in CEL on.
I have an 08 v6 SE myself and have had this experience.
And if CEL indicates the system is running lean, then more fuel is added, and thus low MPG and power. I heard that when you add CAI to 07 or 08, the bending angle of intake pipes in between the MAF sensor really matters and better these two pipes be lined up straight so that MAF doesn't read wrong values because of the turbulence created by the curvature.

I know there are many people here who know about this already
but I just wanted to share this for those who are new to this.
Let me know if i know anything wrong here.
 

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Just wanted to verify about how ECU controls AFR.
So there's a korean guy at clubtuscani.com, which is the biggest tiburon forum in Korea.
He re-maps his own ECU and managed to get 230whp out of his tib with some mods that he did himself.
According to him, our ECU controls AFR constantly to be 14.7 with oxygen sensor feedback only when the throttle is below about 80% opened.
This is called "closed loop" operation, where the car is polling specific sensors to achieve a target AFR of 14.7 (stoich). I believe the 14.7 AFR is optimal for catalytic converter & emissions purposes. I have wondered and it seems feasible if one were to run "catless", can the target AFR be modified slightly leaner (15+ for example) for better fuel economy under light load, cruising conditions, as the motor can be safely ran (within reason) in the 15-16 afr region (according to a local tuner) for a motor like this. Oh and "partial throttle" according to stock parameters is 20% throttle or less.

If the throttle is opened wider than 80%, then AFR is controlled not according to any sensor's feedback but according to the MAP saved in the ECU. It is well known that our tib's default AFR is super rich and that's why the fuel mileage is low. But actually this is not entirely correct. The AFR on dyno graph seems to be super rich only because they floor the throttle to measure the horsepower and the AFR is adjusted according to the MAP already setup in the ECU. So basically, our cars have a bad MAP when the throttle is almost fully opened. ECU remapping means remapping this MAP, but not modifying the AFR by sensors' feedback.
This is called "closed loop" operation, where on a stock tune, anything over 20% throttle the ECU relies on many different factory programmed AFR tables when running. Even with these "tables" there are fuel trims (long term/short term) that are taken into account to "fine tune" these tables (or maps). This is the adaptive nature of our ECU's designed to compensate for long term wear on parts and sensors to keep the motor running in as peak condition as possible.

Adding mods such as intake and exhaust would not lean out the AFR when we normally drive because of sensors' feedback. So we won't experience that much of a difference in MPG. But it will lean out the super rich AFR by the MAP when we accelerate hard, so we will experience increased horsepower and better MPG.
OK, not entirely true. An engine is basically a huge pump. Even in closed loop where the motor is targeting a 14.7 afr, installing mods that increases it's pumping efficiency (I/H/E) allows the air to enter/pass thru the motor with less drag(etc.), letting the engine "breathe" easier. This will translate into better MPGs. You could also view it as the engine is doing less "work" to achieve the same target 14.7.

Now if this is true, it makes sense that driving habits really matter.
Driving habits ALWAYS matter. Staying in closed loop operation will net you the best MPG's as you stay off the richer fuel tables. Besides the thermal losses like heat absorption in surrounding metal in low speed operation, around town driving has us laying our feet on the pedal past 20% throttle which throws us in open loop, using more gas (for example, accelerating up to speed). Highway driving and cruising keeps us in closed loop.

For those who have 07 and 08 have a picky ECU, Modding intake could result in CEL on.
I have an 08 v6 SE myself and have had this experience.
And if CEL indicates the system is running lean, then more fuel is added, and thus low MPG and power. I heard that when you add CAI to 07 or 08, the bending angle of intake pipes in between the MAF sensor really matters and better these two pipes be lined up straight so that MAF doesn't read wrong values because of the turbulence created by the curvature.

I know there are many people here who know about this already
but I just wanted to share this for those who are new to this.
Let me know if i know anything wrong here.
Many times when a CEL is active, the car is running in "limp" mode. "limp" mode basically foregoes the closed loop operation entirely as the ECU believes there is a "problem" and is running on base maps the WHOLE time. Obviously these maps aren't the most efficient setup but it is enough to keep the car running. Hence, wasted fuel.
 

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That is good :D I filled my SE up today and got almost 27 mpg and last time i filled up I got 29. Sounds crazy but it is for real haha I am thinking of putting headers on it after the warranty is up (which I think is next year seeing as how most cars are made a year before their model). But I think that i have heard that the TIbs are made the same year as the model date. Anyways I will also upgrade the intake since it was bought off ebay. I am thinking of a K&N set up.
I used to get about 220 miles a tank with everything stock. When I put my K&N CAI in I now get 260 a tank. I never have calculated the MPG, I usually go on how many miles I can get out of a tank. I usually fill when it's on 1/4 tank.
 

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Discussion Starter · #45 ·
I used to get about 220 miles a tank with everything stock. When I put my K&N CAI in I now get 260 a tank. I never have calculated the MPG, I usually go on how many miles I can get out of a tank. I usually fill when it's on 1/4 tank.
I usually do the same. So far I have been getting, on average, around 350-375 a tank. Not to shabby since it is rated for less than that.
 

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I usually do the same. So far I have been getting, on average, around 350-375 a tank. Not to shabby since it is rated for less than that.
Wow, thats a number I thought my car could ever reach, whats making you get that high? Just the mods?
 

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Mine gets that many miles on a pretty regular basis, haha.

-Brian
 

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Lets not forget guys that rotational mass has A LOT to do with parasitic losses. By reducing any rotating mass connected to the drivetrian, you decrease this loss (ie. LWCP, LWFW, LW Rims (forged or MAT casting)).

There is also parasitic drag. There isn't much you can do concerning the drag from motor oil and other fluids, which is probably in the "it's so small who cares" category. And there pretty much isn't anything you can do about the valvetrain, various pumps, piston rings, etc.

But another form of parasitic drag, profile drag (the shape of the car) can easily be improved. A lowered car reduces the high pressure under the car in conjunction with various functional splitters, as well as the REMOVAL of wings can help lower the Cd (drag coefficient) , improving mileage.

AND of course the frictional drag on the tires is another component one can improve upon. Having the correct tire pressure is ideal for all situations and having really wide tires increases drag. For every 1 psi loss in tire pressure one looses 0.4% mpg. So a 10 psi loss nets a 4% loss to overal mpg's. Not good. It's also good to know that for every 10deg F decrease in temp, tire pressure drops 1 psi as well.
 

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What affect do headers have on gas mileage?
I believe you asked this question in a similar thread young JC~~~~
 

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After modding several cars, I have to say do not exceed 3k rpm's and you will always get good gas mileage. Heck I get 20-25 mpg with my Rx-7 by driving it like an old lady and if you know anything about rotaries you know that they are notorious for getting crap gas mileage being a very small motor.
 

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After modding several cars, I have to say do not exceed 3k rpm's and you will always get good gas mileage. Heck I get 20-25 mpg with my Rx-7 by driving it like an old lady and if you know anything about rotaries you know that they are notorious for getting crap gas mileage being a very small motor.
welcome young sparten~~~
 

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From what it looks like either people are getting exceptional mpg or not at all. I think that the claims of 30+ are a little far fetched unless they are driving with an I4 instead of V6. I guess I will just find out when I get the car and drive it around a little. I figure most of my miles will be highway but I get off work around 5 o'clock and that is when the traffic is hellish:m_BangHea . The one thing no one has mentioned though is with the warranty ie will CAI rid the car of the warranty (granted I guess I will figure that out when I get the car).
it could be the transmission too. The manual has an extra gear so it helps alot. I have the 2.7 v6 with a dumb a$$ 4spd auto and i get 22 average but i babied it like a grandma one time and got 25 or 26. who puts a transmission like that in a car anyway?
 

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Discussion Starter · #55 ·
it could be the transmission too. The manual has an extra gear so it helps alot. I have the 2.7 v6 with a dumb a$$ 4spd auto and i get 22 average but i babied it like a grandma one time and got 25 or 26. who puts a transmission like that in a car anyway?
Yeah the auto trans screws you over in some respects but the ultimate irony is the fast Tib on here is an I4 with an Auto trans. But to update you on the gas mileage, i consistently get 25+ mpg and a few times I have been 28+ and that is not completely babying it either. I am quite surprised at how well the gas mileage is compared to the EPA ratings.
 

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Discussion Starter · #59 ·
huh... i get maybe 19 to the gallon driving a 2004 manual GT full stock...
then again I am going 100mph on my commute... Oops
Not to be a douche or anything but try not to comment on threads that are over a month old. You will get hammered from the MODS eventually. Granted of the thread is stickied I don't believe that rule applies. Just a heads up.
 

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Not to be a douche or anything but try not to comment on threads that are over a month old. You will get hammered from the MODS eventually. Granted of the thread is stickied I don't believe that rule applies. Just a heads up.
Lol I had no intention to boost my post numbers, if that were the case I would be much higher. I have been bed ridden all day so I have been reading a lot of these forums and putting input in, majority trying to be helpful!
 
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