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Old 06-26-2008, 12:25 PM   #1
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Anyone hypermile a BMW?

BMWs are nice fast luxury fuel efficient sport cars. They get good fuel economy for being speedy. I'm looking to get a used 330CI or 330i for less than $14,000 - as a weekend toy car. Does 0-60 in 6.1 sec [01 to 03 model] 5.7 sec [04 to 05 models] and get 18/27 mpg on premium. Premium hurts!

Anyone got a BMW and hypermile it. How fast 0-60 is it and what mpg's do you get?
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Old 06-26-2008, 12:35 PM   #2
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I think people who buy bmws are rich enough not to hypermille =P
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Old 06-26-2008, 12:36 PM   #3
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They pay attention to the aero on them, so they should respond to some careful driving. I kept thinking of trying an old 316 when I had cash for an econobox.
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Old 06-26-2008, 02:16 PM   #4
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Recently I have paid close attention to driving for efficiency and I got 34 mpg in my 318ti. I am just starting out and my goal is to eventually reach 40 mpg. It is a 4 cylinder so it gets better mpg than the 6 you want to get but it is also much slower.

My dad has a 1998 528i and he gets amazing highway mileage without paying a lot of attention to being fuel efficient. Using cruise control at 65 mph gets about 33 mpg. In the city its weight really hurts though and only gets about 25 mpg.

Since the 3 series you want to get is a lot lighter I would guess that you would get around 27 mpg city and 34 mpg highway if you keep it around 65 mph.
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Old 06-26-2008, 05:22 PM   #5
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Quote:
Originally Posted by Kohote View Post
Recently I have paid close attention to driving for efficiency and I got 34 mpg in my 318ti. I am just starting out and my goal is to eventually reach 40 mpg. It is a 4 cylinder so it gets better mpg than the 6 you want to get but it is also much slower.
Try swapping your differential for a 3.23 or 2.93. The gearing on the 318 is extremely short. I get between 28 city to 35 highway in my 91 318i.
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Old 06-26-2008, 08:51 PM   #6
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Hey man, I recognize you from m42 club. You should add your e30 to the garage here, there are not many bmws in the garage and it would be great to see another m42.

I have been thinking about swapping to a lower diff because right now I am running crazy revs on the highway. I am pretty sure it is a 4.10 because 75 mph is around 3500rpm. Do you think I would be ok with a 3.23 or even a 2.93? I would really like to lower the revs for the highway but I am worried I may be lugging the engine a lot or have to downshift for even the slightest hills. How much do you think a small case 3.23 open diff would cost? I checked out diffsonline but I could only find prices for medium case and larger diffs. What diff do you have and how do you like it? Thanks for your help!
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Old 06-26-2008, 11:15 PM   #7
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One of these days I'll get around to adding my car to the garage.

The differential depends on whether your car is automatic or manual. The E36 has a 1 to 1 5th gear as opposed to the E30s .81 5th. So the numeric ratio is completely different but the end result is the same. The 318ti 5 speed came from the factory with a 3.44 small case differential. The automatic had a 4.4 diff because of the totally different gearing in 4 speed auto. The E30 318i has a 4.1 diff from the factory. But the E30 and E36 M42 powered cars run almost exactly the same RPM on the highway.

E36 318ti


E30 318i


I change my E30 differential from 4.11 to 3.64. RPMs dropped about 12%.


If your car is a 5 speed 318ti, i would go to a 3.23 medium case diff from a E34 525i (M50) 5 speed (with E30 diff cover) or a 2.93 medium case diff from an E30 325e 5 speed. This should give you similar RPM drop. You'll probably be able to find either ratio with an LSD which is nice to have in the winter.
I picked up my 3.64 differential for $50. 325e are all over the JYs around here.

E30 diff ratios
http://www.e30tech.com/forum/showthread.php?t=1863
E34 diff ratios
http://farm3.static.flickr.com/2069/...f11d7523_o.jpg
318ti diff swap
http://www.emotors.ca/Articles/7.aspx
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Old 06-27-2008, 05:59 AM   #8
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Quote:
Originally Posted by Kohote View Post
I would really like to lower the revs for the highway but I am worried I may be lugging the engine a lot or have to downshift for even the slightest hills.
If you're worried about engine longevity consequences, then you probably don't need to worry about lugging; most modern computer-controlled cars either run or stall but can't lug.
http://www.gassavers.org/showpost.ph...6&postcount=10

I personally am a big fan of tall gears and low RPMs.
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Old 06-27-2008, 09:37 PM   #9
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Wow! Thank you so much, I was trying to find something exactly like that. So the tallest small case diff is the 3.44 in the ti? Is the medium case diff significantly heavier than the small case diff?

My ti is a five speed, would you go for the 3.23 or the 2.93? I would prefer the rpms to be as low as possible on the highway but still only have to downshift for really long steep uphill grades. I think the 2.93 would still be okay because 3k rpm would be at 75 mph. With that setup it looks like I would still spend most of my time between 2500-2750 rpm, which gives lots of margin before being completely out of power.

I would love to get an lsd for the winter. So if I find a diff from an e30 325es I will be all set? Do you know if any other bmws had a 2.93 lsd?
Sorry for all the questions, I really appreciate your help.
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Old 06-28-2008, 12:29 AM   #10
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As far as I know, yes the tallest small case LSD available in the US is 3.44. I think there might be some taller small case diffs on some weird models in europe but I'm not sure. The medium case weighs about 30lb more than the small case and it also adds about 3% more internal friction according to Metric Mechanics. PDF, page 5
http://www.metricmechanic.com/pdfs/m...al-booklet.pdf
If you reallly wanted to go off the deep end with this project, instead of replacing the differential, you would replace the transmission for an E30 .81 overdrive unit. This would give you the best of both worlds. Small case diff and taller gearing. But thats a lot more work than swapping diffs.
I think the M42 engine can handle the 2.93. You will give up some peak acceleration and you'll have to downshift more often to pass people on the freeway but I think its worth it.
If you want to make sure you have an LSD before you buy it, have both rear wheels off the ground on the JY car, turn one wheel and watch the direction of the other. If the other wheel turns the opposite direction, its an open diff. If it turns the same direction, its an LSD. Some cars will have a tag hanging off one of the bolts on the rear cover with the differential ratio number. LSDs have an "S" in front of the number. S2.93 for example.
A 2.93 diff will drop RPMs by about 15% which sounds perfect to me. I if I could go from the 3.64 to a 3.44 in my car, that would be ideal.
I think some E28 5 series might have the 2.93 as well. I know for sure the E28, E30 and E34 share the same differential case with the E36 318ti. But thats a unique situation. All other E36 cars have a completely different differential case that is not compatible with the TI.

Small case right, medium case left.
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