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post #1 of 23 Old 10-03-2005, 10:43 PM Thread Starter
blizzboy283
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K&N FIPK

Hi, I was wondering how much better fuel economy I can get with a K&N FIPK and a Gibson cat-back exhaust on a 99 WJ Limited V8? Thanks

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post #2 of 23 Old 10-03-2005, 11:13 PM
JCDubya
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It'll probably be worse. More air in needs more fuel to have a proper combustion.
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post #3 of 23 Old 10-04-2005, 04:20 AM
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Performance parts rarely mean better mileage.


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post #4 of 23 Old 10-04-2005, 08:49 AM
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at best, mpg will be about the same. I have noticed a "perceived" performance improvment at WOT on on-ramps and passing. I have improved my average mpg by driving smoother and slower, anticipating stops, avoiding rush hour jams, planning trips. I was avreaging about 14.8 mpg and now i'm up to about 16.2. I do about 95% in-town driving and rarely go faster that 40 mph.

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post #5 of 23 Old 10-04-2005, 03:30 PM Thread Starter
blizzboy283
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Quote:
Originally Posted by JCDubya
It'll probably be worse. More air in needs more fuel to have a proper combustion.

Man no offense but that was a blind guess you took. That is like saying a clean air filter will mean less gas mileage because more air is coming in when it will only improve gas mileage. My main question for asking was seeing if any that have them have seen any gains.
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post #6 of 23 Old 10-04-2005, 03:47 PM
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gasoline engines always put in the same amount of fuel at a certain rpm. the throttle doesn't control how much gas you put into your engine but how much air you are putting in to your engine and if you can get more air in at lower rpms then you will make more power at lower rpms and you won't have to go as high in rpms to accelerate the same, meaning better mpg

1995 ZJ 4X4
command-trac (NP231) with SYE
K&N FIPK intake
RE 6.5in lift with 33X12.5 BFG MT and no Rear Sway bar
4.56 gears--axle swap soon
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post #7 of 23 Old 10-04-2005, 03:53 PM
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Maybe 1-3mpg

And for those saying worse - try and back that up scientifically. Hopefully you own one of dem toranado intake spinners too

Less restictions = better performance from more efficiency.

TJ
4.0L, 5spd, 2"BB, 31x10.5 Mud Terrains, Black Steelies,Hella 100W, Custom Brushguard, IPF H4 housings w/ Fatboys, Sirius 23 Hair Nation!
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post #8 of 23 Old 10-04-2005, 04:01 PM
MidniteSquirrel
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I haven't seen anyone report worse mileage due to better airflow like that...

unless they're hitting the gas more do to the feel of more power?

2002 WJ - I6

BB+UC 3.5" lift | K&N FIPK | Armor/Tow points |
265/75R16 Cooper Discoverer S/Ts
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post #9 of 23 Old 10-04-2005, 04:03 PM Thread Starter
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Brad and Awild thank you for your input and advice. I knew there had to be some performance enthusiasts here! My last car was a mustang cobra so I knew the K&N had to help some how. Thanks again!
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post #10 of 23 Old 10-04-2005, 04:03 PM
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Hmm I thought the computer told the fuel injectors how much to fuel to send based on the input from the sensors.
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post #11 of 23 Old 10-04-2005, 05:10 PM
JCDubya
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Quote:
Originally Posted by blizzboy283
Man no offense but that was a blind guess you took.
Actually it wasn't. If you're so sure I'm wrong they why did you start this thread? You obviously have your mind set on getting better mileage.


Quote:
Originally Posted by BradBurdett
gasoline engines always put in the same amount of fuel at a certain rpm. the throttle doesn't control how much gas you put into your engine but how much air you are putting in to your engine and if you can get more air in at lower rpms then you will make more power at lower rpms and you won't have to go as high in rpms to accelerate the same, meaning better mpg
No they don't always put in the same amount of fuel at a certain RPM. It depends on vacuum (how much AIR is being put through the motor). For example, you could bog (kind of hard on an automatic) at 2k or you could be at WOT which = 0 vacuum. Do you think the same amount of fuel is being dumped in when your bogging as when your flooring it? If you don't understand, look at this. This is the program I used to tune my integra. The Y-axis is RPM. The upper X-axis is vacuum and the lower x-axis is boost. This is an unfinished map but it's just go give you an idea. Pick any RMP you want. Follow it over to the right, the further right you go, the less vacuum there is which means you're stepping on the gas more. For the n0Obs, the higher the number inside the chart means more fuel (more red). and they call it air/fuel ratio for a reason, not rpm/fuel ratio.


And when you talk about making "more power at lower RPMs". What is power? It's an explosion. For something to combust you need oxygen, fuel, and heat. To get more power (ie. bigger, stronger explosion) you need more air and fuel. You can't increase just one and expect the same results. The computer puts in the proper amount of fuel based off of a MAP like the above diagram, or some cars use a Mass Air Flow Sensor.

Quote:
Originally Posted by AWILD
Hopefully you own one of dem toranado intake spinners too
Yes I have one of "dem" intake spinners, it's called a turbo.

and the butt dyno can be very deceiving when it comes to a new performance part and how much power you gained - think placebo.
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post #12 of 23 Old 10-04-2005, 05:26 PM
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Quote:
Originally Posted by blizzboy283
Hi, I was wondering how much better fuel economy I can get with a K&N FIPK and a Gibson cat-back exhaust on a 99 WJ Limited V8? Thanks
You are not likely to see much (if any) increase in your average miles per gallon. Certainly not enough to offset the cost of those two systems.
That being said, a less restrictive intake and exhaust have been proven to increase engine performance. Of course, a cat and back is not going to net you the gains that headers and back will. I have a performance package installed on my Jeep, and I can tell you I saw no gains in fuel economy. However, I do feel the engine doesn't work as hard to get up to and maintain speed. This is entirely a subjective (emotional) feeling and I don't spend much time dwelling on it. I know that my Jeep accellerates more quickly and easily than it did before I upgraded, and that's what I wanted to achieve. If I were looking to improve fuel efficiency to any measurable degree, there are other ways to achieve that, driving style being the first (and most dramatic) area to address.
HTH

Warren
Black 1996 5.2L ZJ Limited
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post #13 of 23 Old 10-04-2005, 06:26 PM
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Quote:
Originally Posted by JCDubya
Yes I have one of "dem" intake spinners, it's called a turbo.
.
Hmm...thought turbos (since i've owned two modded DSM's) spun exhaust not intake

Does your "turbo" look like this by chance HERE

Because from the sounds of your talk, any real turbo owner should know that better intake and better exhaust will make your turbo spool faster = better perfomance from (get this) more efficient air flow which ironically leads to better mpg.

My Talon had damn near 350hp and got over 30mpg (close to the rated stock mpg)

My 3000GT has intake and straightpipes and again gets more mpg than stock

TJ
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post #14 of 23 Old 10-04-2005, 06:59 PM
JCDubya
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Geeze, give it up. I'm was just messing around. A turbo "spins" exhaust and intake as you like to put it. Exhaust passes through the turbine housing, spinning the turbine which then spins the compressor which sucks in the ambient air.

No it wasn't one of those cheap blower fans. It was a T3/T04e. No kidding, a free flowing exhaust will spool it faster. I had a full 3" system. But what does that have to do with better MPG? I too, got close to stock MGPs but that's all in the tuning. You couldn't expect to get better mileage if you ran just a FMU.
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post #15 of 23 Old 10-04-2005, 07:07 PM
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I'm done arguing. Believe what you want

TJ
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