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What do you guys get for highway fuel economy?

Discussion pertaining to positive pressure E28s.
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Jeremy
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What do you guys get for highway fuel economy?

Post by Jeremy »

And what's your average travel speed? Going out to Toronto last weekend, I got my usual 21 mpg. I set the cruise at 78 mph by GPS (82 on the speedo).

On the way home I decided to see what would happen if I set the cruise at 70 instead, so I did. Achieved 23-25 mpg for the trip home, which is quite a substantial increase.

With the 3.46 gears, the car cruises at ~3100 rpm at 78 and around 2800 rpm at 70. My guess is that the motor is sucking down fuel since it's so close to being on cam, as opposed to being just off cam at 70, and I'd get better fuel economy with a 3.25 or 3.07 at the higher speed.

Or it could just be the fact that at 70 mph I can maintain constant speed without constantly having to slow down for and go around traffic. Which is more likely, any thoughts?

Jeremy
RDAvena
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Post by RDAvena »

roughly about 25. This is with the MS and 3.07 diff. If I keep my foot out of it it should yield a little more. This plus some more economy tuning of the fuel maps.
BMWgiant
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Post by BMWgiant »

I get about 23-25mpg highway at a steady 80mph... I did follow a semi for about 20mi once going between 70-80mph and was able to get 31mpg on the OBC.. I was very impressed..
davidu
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Post by davidu »

mine gets around 18mpg and way less under boost...
M3fan4eva
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my mileage

Post by M3fan4eva »

I only get about 15, granted, i boost it sometimes during my daily driving, but does the fact that i put bigger injectors in there diminish my gas mileage? I have an A/F ratio monitor in the car and cruising it says i get around 14.7, so does the fact that i got bigger injectors really matter? or is it cancelled out by the fact that I tuned my AFM to compensate.
karl
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mpg

Post by karl »

I got 34.2 on my last fill with mixed driving; mostly highway at 70+mph.
Bill in MN
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Post by Bill in MN »

15-18 for local/boost driving. Highway/no boost is around 23-25 on a good day. 3.73 w/auto.
JamusMcFamus
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Re: mpg

Post by JamusMcFamus »

karl wrote:I got 34.2 on my last fill with mixed driving; mostly highway at 70+mph.
You got ~500 miles on one tank of gas?! Tell me I did my math wrong...
shifty
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Re: mpg

Post by shifty »

JamusMcFamus wrote:
karl wrote:I got 34.2 on my last fill with mixed driving; mostly highway at 70+mph.
You got ~500 miles on one tank of gas?! Tell me I did my math wrong...
PSSST, he's probably talking about his 524td with manual transmission.
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Post by JamusMcFamus »

How I missed that, God will only know.
shifty
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Post by shifty »

JamusMcFamus wrote:How I missed that, God will only know.

;) Not trying to bust your chops or anything. I don't pay attention to sig lines too terribly often, either.
Shawn D.
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Post by Shawn D. »

Before anyone else posts their MPG, note that Jeremy isn't asking "What MPG does your E28 get?," he's asking "What MPG does your E28 with a turbocharged M30 get?"
a
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Post by a »

Shawn D. wrote:Before anyone else posts their MPG, note that Jeremy isn't asking "What MPG does your E28 get?," he's asking "What MPG does your E28 with a turbocharged M30 get?"
Best Peter Sellers playing Inspector Clousseau voice :Ihh knew thet :laugh:
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Post by shifty »

Shawn D. wrote:he's asking "What MPG does your E28 with a turbocharged M30 get?"

It was so obvious, too, since the only E28 that would fall under Forced Induction would be a turbo M30. ;)
landspeed
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Post by landspeed »

shifty wrote:
Shawn D. wrote:he's asking "What MPG does your E28 with a turbocharged M30 get?"

It was so obvious, too, since the only E28 that would fall under Forced Induction would be a turbo M30. ;)
Or a turbo M20 :roll:
shifty
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Post by shifty »

landspeed wrote:
shifty wrote:
Shawn D. wrote:he's asking "What MPG does your E28 with a turbocharged M30 get?"

It was so obvious, too, since the only E28 that would fall under Forced Induction would be a turbo M30. ;)
Or a turbo M20 :roll:
Or a turbo M21, or a turbo S38, or a supercharged M60. . . I was being facetious.
Shawn D.
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Post by Shawn D. »

Yeah, it's soooo obvious... so don't tell me that -- tell BMWgiant and karl. :roll:
shifty
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Post by shifty »

Shawn D. wrote:Yeah, it's soooo obvious... so don't tell me that -- tell BMWgiant and karl. :roll:
Want a hug, Shawn? I was kidding, buddy! ;)
Shawn D.
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Post by Shawn D. »

shifty wrote:Want a hug, Shawn? I was kidding, buddy! ;)
After struggling with lowering the transmission on my Mercedes 300td wagon so I could replace the tranny cable, I really could have used one at 01:00... :bawl:
M3fan4eva
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Post by M3fan4eva »

On my turbo, I had adjusted the AFM to about a 14.7 at idle and crusing. Even though I have bigger injectors and if on a given tank of gas, I do not turbo it once, will i get rather impressive gas mileage? I want something to be at least in the 20's. at least.
Jeremy
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Post by Jeremy »

I'm running 30 lb injectors and have tuned for a slightly lean cruise. Get's 20-21 in the cold with cruise at 78 mph on a long trip, and not making any effort to stay out of the boost. Cruise at 70 and staying out of the boost gives me closer to 24 mpg.

My car has a 3.46 differential, so cruising at 78 puts me at 3100 rpm. This appears to be a rather thirsty area for the m30.

Getting 20+ mpg out of your e30 should not be an issue if you drive conservatively and use the right gears.

Jeremy
M3fan4eva
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Post by M3fan4eva »

Great, I'll try to drive a full tank w/o any boost and very conservative acceleration. I'll see what I get. Looking around 24mpg.

Unfortunately, there's a shiteload of snow on the ground, so driving it it out of tze qvestion.
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