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post #1 of 39 (permalink) Old 11-14-2005, 05:00 PM Thread Starter
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Mods for gas mileage

Has anyone actually noticed a change in fuel economy when they put on the K&N Fipk? What about a dual exhaust? I see Trubenz makes a pretty good exhaust but does its really do anything for performance or fuel economy? I have a 01 R/T. I currently get between 22-24 with mostly city driving. I realize thats pretty good for a big car and big engine, but ever since I got that evic with the Average/miles/gallon I've been trying to get better mileage. It's almosts like a game....
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post #2 of 39 (permalink) Old 11-14-2005, 05:52 PM
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Maxing out your gas mileage requires a few compromises. Inflate your tires to the maximum allowable pressure as stated on the sidewall, usually around 44 psi. This will give you a rock-hard ride, but it's the way to the least amount of rolling resistance. Reduce any unnecessary weight in the car. When accelerating, don't let the engine go over 2500 rpm before it shifts. This basically means to act as if there were an egg underneath the gas pedal. Time traffic lights so you don't have to stop. Drive at the speed limit or 5 under on freeways. Drive with the windows closed, and if you must use the A/C, keep it about halfway up the temperature dial, not at full cold, and the blower at low speed. This will reduce the amount of time the compressor is on. Any extra electrical loads put extra stress on the alternator, so keep those to a minimum. Of course, doing all of these things isn't practical in the real world, but I did all of these things for one tank of gas, just to see what kind of mileage I'd get. I got about 35 mpg, and that's with a 3.5L H.O.
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post #3 of 39 (permalink) Old 11-15-2005, 02:50 AM
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All you can really do is keep up on your general maintmence. I don't know if the FIPK or an exhaust will help MPG, (although i'd think it would)

Check and replace spark plugs
Keep up on oil/trans fluid changes
check your tire pressures


I just took a 1200 mile trip over the weekend, my only performance mod is a drop in K&N filter. Set the cruise to 75 mph the entire time. The first half of the trip i turned 25 mpg. I checked my tires out, and they were all at least 10lbs low. I pumped them all up to 40lbs, and got 27mpg on the second half of the trip. The ride was much harsher though...
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post #4 of 39 (permalink) Old 11-15-2005, 09:55 AM Thread Starter
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I know about the maintenace and the driving tips but is there no concrete evidence to proven gas mileage saving devices?
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post #5 of 39 (permalink) Old 11-15-2005, 10:22 AM
 
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Jacking up the tire pressure might be a good way to boost fuel economy but is not very safe. Decreasing the rolling resistance has the effect of increaed braking distance. Rolling resistance is better than skid resistance, hence why ABS was invented. When a car locks up, the resistance between the tires and the road is greatly reduced than that of a rolling tire. Also, increasing the tire pressure will cause the center of the tread to wear faster than the rest. And the increased tire pressure creates less of a contact patch between the road and the tread (which leads to the reduced rolling resistance). This all translates into reduced handling and braking. Keeping tires slightly overinflated by a couple pounds wouldn't be detrimental but 10+ overinflated is ill-advised.

I do mostly highway driving with a 2.7 and am lucky to get 24 MPG. How anybody with an R/T and 3.5 is getting 22-24 mostly city or 35 on the highway I'd like to know. The best I've seen out of this car was 28 or 29 which was all highway.
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post #6 of 39 (permalink) Old 11-15-2005, 10:59 AM
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My ES i got 30.2 going to GearFest. With the cruise set on 72 mpg. I have the Flowmaster single in dual out. And a bored out TBI. Tire psi set at 36 psi. Going home i was doing 75 to 85 mph and got 28.9 mpg. A CAI and better Exhaust and higher tire psi. Will gain maybe between 1 to 3 better mpg. If you still drive like a little old lady.
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post #7 of 39 (permalink) Old 11-15-2005, 02:35 PM
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I have both Custom True Duals and a K&N FIPK. Fuel economy has improved on the highway, but I can't seem to keep my foot light enough around town for a full tank so city driving has decreased. Tank avereages are between 20-23, depending on how many times I showed off. ;-)
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post #8 of 39 (permalink) Old 11-20-2005, 08:16 AM
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Quote:
Originally Posted by mbtech208
Maxing out your gas mileage requires a few compromises. Inflate your tires to the maximum allowable pressure as stated on the sidewall, usually around 44 psi. This will give you a rock-hard ride, but it's the way to the least amount of rolling resistance. Reduce any unnecessary weight in the car. When accelerating, don't let the engine go over 2500 rpm before it shifts. This basically means to act as if there were an egg underneath the gas pedal. Time traffic lights so you don't have to stop. Drive at the speed limit or 5 under on freeways. Drive with the windows closed, and if you must use the A/C, keep it about halfway up the temperature dial, not at full cold, and the blower at low speed. This will reduce the amount of time the compressor is on. Any extra electrical loads put extra stress on the alternator, so keep those to a minimum. Of course, doing all of these things isn't practical in the real world, but I did all of these things for one tank of gas, just to see what kind of mileage I'd get. I got about 35 mpg, and that's with a 3.5L H.O.
I'm shocked that a certified mechanic suggested bringing tire pressure to its rated maximum. I've been always of the opinion that the pressure rating on the driver side door was the pressure adjusted for the weight of the vehicle.
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post #9 of 39 (permalink) Old 11-20-2005, 10:19 AM
 
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Quote:
Originally Posted by nemaroller
I'm shocked that a certified mechanic suggested bringing tire pressure to its rated maximum. I've been always of the opinion that the pressure rating on the driver side door was the pressure adjusted for the weight of the vehicle.
It is. The tire pressure listed on the tire is the max recommended by the tire manufacturer. Somebody had a thread started on what pressure to use. Someone in there posted to use the pressure on the tire as a recommended by the maker, not the door sticker. I did searching on many tire makers' sites and all said to go by the sticker in the car. Most tires are made for a wide variety of vehicles so its impossible for them to be able to recommend a pressure for any car. This is the reason why inflation pressures are listed on a sticker in all cars nowadays. The max pressure listed on the tire itself, is the maximum deemed safe for that particular tire, not nessesarily what is safe for your car.

As I stated in my previous post, overinflating the tires is a sure way to lose control of the car.

Last edited by froggy81500; 11-20-2005 at 10:22 AM.
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post #10 of 39 (permalink) Old 11-20-2005, 10:22 AM
 
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My friend has an 02 GAGT, and he went to Napa and bought a "Tornado Fuel Saver". It pops in your intake just before the throtle body. He's claimed 5-10mpg increase, and a slightly deeper exhaust note.
Couldn't hurt to check that out. :P
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post #11 of 39 (permalink) Old 11-20-2005, 12:16 PM
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i run my tires cold at 36PSI, K&N drop in, joeKD intake. stock exhaust for now, and according to computer i am averaging 23.2 MPG, that being said remember that cold weather states use a higher blend alcohol based fuel, which causes loss of mileage. In the last month i have lost mileage from 23.4, and i have changed plugs, and cleaned the filter
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post #12 of 39 (permalink) Old 11-20-2005, 01:35 PM
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Quote:
Originally Posted by 02R/T
My friend has an 02 GAGT, and he went to Napa and bought a "Tornado Fuel Saver". It pops in your intake just before the throtle body. He's claimed 5-10mpg increase, and a slightly deeper exhaust note.
Couldn't hurt to check that out. :P
Your friend is full of it. They just did a study (Popular Mech) on all the so called fuel savers. They all are rip offs. Tornado lost 10% mpg and 10% on the dyno. Do not waste your money on these things.
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post #13 of 39 (permalink) Old 11-20-2005, 03:05 PM
 
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Quote:
Originally Posted by dabirdzR/T
i run my tires cold at 36PSI, K&N drop in, joeKD intake. stock exhaust for now, and according to computer i am averaging 23.2 MPG, that being said remember that cold weather states use a higher blend alcohol based fuel, which causes loss of mileage. In the last month i have lost mileage from 23.4, and i have changed plugs, and cleaned the filter
Yeah but keep in mind also, that when it gets colder outside, you'll lose fuel economy also. the longer it takes the engine to warm up, the more fuel is wasted warming it up. Regardless of whether you let it sit and idle to warm up or drive it to warm it up, cold weather is a real beater on fuel economy.

Yeah and those tornado things, yeah I think I'll get some sheet metal and twist it into a propeller and stick it in my intake. That should to get me 35 MPG while my car idles in the driveway. The EPA and others have tested these supposed "fuel savers" including the tornado and the magnet on the fuel line gizmo. Snake oil. Honestly, if any of those items actually worked, don't you think they'd get some kind of ok by the EPA or Dept of Energy? And don't confuse a patent as an approval. A patent is given to legally protect their designs to keep others from copying it, regardless of whether it works or not.
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post #14 of 39 (permalink) Old 11-20-2005, 06:04 PM
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Here are a few tips for tire pressure setting.

If you can find Nitrogen in your area, fill your tires with that. It is less susceptible than regular air to temperature changes.

Tire pressure changes 1 psi for every 10 degrees of temperature. So if you were at 32psi and the temp dropped 30 deg overnight, then your tires would drop to 29 psi.

Think if you have your tires at 44psi and then you go on a long road trip. Your tire temp is gonna rise right? Maybe you get on some hot blacktop in Texas where the road is 40 deg hotter than your garage - where does that put you ?

Just food for thought
Never inflate your tires to max pressure on sidewall

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post #15 of 39 (permalink) Old 11-20-2005, 06:54 PM
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Quote:
Originally Posted by nemaroller
I'm shocked that a certified mechanic suggested bringing tire pressure to its rated maximum. I've been always of the opinion that the pressure rating on the driver side door was the pressure adjusted for the weight of the vehicle.

For all you guys making a big deal about high pressure, go out and do some performance driving, then rethink if 44 psi is really a big deal. It's NOT. Do it all the time for autocross, that's the only way to save the sidewalls.

The max pressure listed on the sidewall is FAR away from the actual rupture pressure. It has VERY little ill effect on handling. Sure it'll give you a bit less grip, but much better steering response, body roll reduction, etc. Normal drivers are unlikely to venture near those grip limits anyway.

The door pressure was typed in by the manufacture, not GOD. It's usually aimed at comfort, not just safety. Look at the late 90's Ford Explorers, what happened when soccer moms actually believed the 23 psi stamped on the door?
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