29.4 hwy mpg despite mods

ksfrogman · 02-03-2007, 02:54 AM

Being the sometimes neglectful guy that I am, I let my tire pressures deflate to around 22 psi. This evening, I inflated each tire back to 34 psi, and to my surprise, my mpg went up to 29.4 mpg (highway mostly), which is the highest it has been since I had switched out the rear diff to one with shorter gearing.

I was so ecstatic with my gas mileage, I had to share.

Factors that may affect mpg:

Odometer: 20,900 mi.
Trans: 6MT
Rear Diff. Gear Ratio: 3.64:1 (stock: 3.15:1)
Intake: GruppeM / Open air dam / Dinan high flow throttle body
Exhaust: Eisenmann race quads
Wheels & Tires: 19x10 rear w/ 235/35 ZR19 Toyo Proxes4 rear, 19x8.5 w/ 235/35/ZR19 Toyo Proxes4 front

uhaulball · 02-03-2007, 03:00 AM

u use 34psi? i use 40psi. im gonna try 35 due to ur post.

Jaws · 02-03-2007, 12:08 PM

Great numbers. As an aside, I've noticed that the computer is a bit optimistic. I was on a long road trip last weekend and got 6.9 L/100 km on the computer, but got 7.3 ( 32 mi/US gal) when I calculated it by hand.

///Matt · 02-03-2007, 12:44 PM

The computer is actually adjustable, by a BMW tech. If you think it is inaccurate in it's mileage calculations, take it to the dealer, and have them adjust the calculation.

ironic · 02-03-2007, 01:14 PM

Quote:

Originally Posted by ///Matt

The computer is actually adjustable, by a BMW tech. If you think it is inaccurate in it's mileage calculations, take it to the dealer, and have them adjust the calculation.

lol that seems odd, shouldn't it be objective?

///Matt · 02-03-2007, 01:26 PM

Well, it's an algorithm of some kind to calculate MPG based on distance travelled and TI signal (fuel injector on time).

just4kickz · 02-03-2007, 02:40 PM

how fast were u going? i got good mileage when i had a flat... i mean i had to go like 55mph on 6th gear... so my mileage was around 30mpg, but i usually cruise around 70-80 and that makes me get around 25mpg

ksfrogman · 02-03-2007, 02:45 PM

Quote:

Originally Posted by just4kickz

how fast were u going? i got good mileage when i had a flat... i mean i had to go like 55mph on 6th gear... so my mileage was around 30mpg, but i usually cruise around 70-80 and that makes me get around 25mpg

I was going between 70 and 80 mph in 6th gear on the 110 Harbor Fwy through L.A., definitely no lower than 70 mph.

porksoda · 02-04-2007, 01:39 AM

Quote:

Originally Posted by ///Matt

The computer is actually adjustable, by a BMW tech. If you think it is inaccurate in it's mileage calculations, take it to the dealer, and have them adjust the calculation.

No matter how much you adjust em.. they will never be accurate... always calculate them yourself... then you get the actual mpg.

Jaws · 02-04-2007, 12:50 PM

Quote:

Originally Posted by porksoda

No matter how much you adjust em.. they will never be accurate... always calculate them yourself... then you get the actual mpg.

It's an instrument just like any other, so if the dealer can put a "fudge factor" adjustment in the DME, it will become more accurate. In my post above, I noted that when the computer stated the mileage as being 6.9, that it was actually 7.3. Now, this may mean that it is consistanly .4 high, but I do not think that this inaccuracy is linear throughout the range.

I understand that the only true way to measure is by manual calculation, but even then there are variables such as how much gas you really did use (when did the fuel nozzle "click" off? Was the tank really full or was it a litre or two short).

02-03-2007, 02:54 AM	#1
ksfrogman Major General 576 Rep 6,750 Posts Drives: E90 330i 6MT Join Date: Nov 2005 Location: Torrance, CA iTrader: (12) Garage List 2006 330i [0.00] 2006 330i [0.00]	29.4 hwy mpg despite mods Being the sometimes neglectful guy that I am, I let my tire pressures deflate to around 22 psi. This evening, I inflated each tire back to 34 psi, and to my surprise, my mpg went up to 29.4 mpg (highway mostly), which is the highest it has been since I had switched out the rear diff to one with shorter gearing. I was so ecstatic with my gas mileage, I had to share. Factors that may affect mpg: Odometer: 20,900 mi. Trans: 6MT Rear Diff. Gear Ratio: 3.64:1 (stock: 3.15:1) Intake: GruppeM / Open air dam / Dinan high flow throttle body Exhaust: Eisenmann race quads Wheels & Tires: 19x10 rear w/ 235/35 ZR19 Toyo Proxes4 rear, 19x8.5 w/ 235/35/ZR19 Toyo Proxes4 front __________________
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02-03-2007, 03:00 AM	#2
uhaulball Brigadier General 195 Rep 4,163 Posts Drives: e90 330xi Join Date: Dec 2005 Location: Long Island, NY iTrader: (11)	u use 34psi? i use 40psi. im gonna try 35 due to ur post. __________________ '06 bsm e90 330xi : 18" VMR CSL : KW V3 : GruppeM Rep Intake : UUC/Corsa Catback : Hartge Lip : ACS Roof Spoiler OEM CF Trunk Spoiler : CF Emblems. Pillars. Mirror. Grille : LUXER12 led plate : V1 Hardwired : OG.longtran e90post sticker! circa 2005
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02-03-2007, 12:08 PM	#3
Jaws Lieutenant Colonel 45 Rep 1,738 Posts Drives: 2006 325i mt Join Date: Aug 2006 Location: Edmonton iTrader: (0)	Great numbers. As an aside, I've noticed that the computer is a bit optimistic. I was on a long road trip last weekend and got 6.9 L/100 km on the computer, but got 7.3 ( 32 mi/US gal) when I calculated it by hand. __________________ 2006 325i - Sparkling Graphite 2000 S2000 - New Formula Red 2007 Chev Silverado crew cab Z71
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02-03-2007, 12:44 PM	#4
///Matt United States Marine 318 Rep 2,748 Posts Drives: 2007 Dodge Ram 1500 Join Date: Jul 2006 Location: Los Angeles iTrader: (8) Garage List 2006 330i [0.00]	The computer is actually adjustable, by a BMW tech. If you think it is inaccurate in it's mileage calculations, take it to the dealer, and have them adjust the calculation.
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02-03-2007, 01:26 PM	#6
///Matt United States Marine 318 Rep 2,748 Posts Drives: 2007 Dodge Ram 1500 Join Date: Jul 2006 Location: Los Angeles iTrader: (8) Garage List 2006 330i [0.00]	Well, it's an algorithm of some kind to calculate MPG based on distance travelled and TI signal (fuel injector on time).
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02-03-2007, 02:40 PM	#7
just4kickz boku no namae ha... 336 Rep 11,025 Posts Drives: 2006 BS 330i Join Date: Feb 2006 Location: S. Bay Area, CA + Newark, NJ + ChiCity + True Blue iTrader: (11) Garage List 2006 E90 330i [0.00]	how fast were u going? i got good mileage when i had a flat... i mean i had to go like 55mph on 6th gear... so my mileage was around 30mpg, but i usually cruise around 70-80 and that makes me get around 25mpg __________________ looking for a PreLCI Black Sapphire e90 front bumper without license plate holes "Akimbo shotguns. Broken wrists anyone? And don't give me that 'it's just a game' bull**. Where the are my akimbo interventions then?! One scope on each eye mother**er!!"
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