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F30 / F31 / F32 / F33 (2012 - current)
The sixth generation 3 series, chassis code F30. 2013 model year 328i and 335i sedans now in production. Read the F30 frequently asked question thread for all your basic question and dive into all the details in the ultimate F30 information thread.

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  #1  
Old 09-29-2013, 10:37 AM
M34Lnch M34Lnch is offline
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Anyone notice that the 428i only gets 1 mpg better in the city compared to the 435i?

Good news for 435i owners, how did they achieve this?

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  #2  
Old 10-03-2013, 09:05 AM
M34Lnch M34Lnch is offline
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Old 10-03-2013, 09:31 AM
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Is it good news for the 435 or bad news for the 428? N4S
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Old 10-03-2013, 09:38 AM
M34Lnch M34Lnch is offline
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At first I thought it had something to do with the new 8-speed transmissions, but now i think it is likely related to the engine auto start/stop function?
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Old 10-03-2013, 10:22 AM
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Yeah, but using that theory the 428 would be higher then it is.
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Old 11-16-2013, 07:27 AM
M34Lnch M34Lnch is offline
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Old 11-16-2013, 08:26 AM
Michael Schott Michael Schott is offline
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Why do you keep bumping this thread?
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Old 11-16-2013, 09:08 AM
M34Lnch M34Lnch is offline
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Because I don't have an answer to my original question.
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Old 11-16-2013, 09:38 AM
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Probably just physics. The 4cyl is working harder than the I6 in the city cycle, decreasing it's efficiency. It would normally make up for lost ground during idle time, but ASS takes that advantage away.
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Old 11-16-2013, 02:12 PM
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Re: Anyone notice that the 428i only gets 1 mpg better in the city compared to the 43

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Because I don't have an answer to my original question.
Yes
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Old 11-16-2013, 02:53 PM
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probably just physics. The 4cyl is working harder than the i6 in the city cycle, decreasing it's efficiency. It would normally make up for lost ground during idle time, but ass takes that advantage away.

this. ^^
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Old 11-16-2013, 06:43 PM
Michael Schott Michael Schott is offline
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Quote:
Originally Posted by M34Lnch View Post
Because I don't have an answer to my original question.
There is no easy answer. My guess is that the EPA test cycle is not like real life and that in reality the I4 is much more efficient. I also disagree that the I4 works harder than the I6 as said above. It's doing the same amount of work with 2 less cylinders that are basically the same size as those in the N52. It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel. It only works hard when you put your foot into it and spool up the turbos. These 4 cylinders are not turning at higher RPM than those of the I6 and in fact make more power at lower RPM.

I can tell you that my N20 with 1400 miles on it is averaging an indicated 26.1 mpg in city/local highway driving averaging 31 mph. My N52 averaged about 23 mpg at that average speed.
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Old 11-16-2013, 08:23 PM
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Originally Posted by Michael Schott View Post
There is no easy answer. My guess is that the EPA test cycle is not like real life and that in reality the I4 is much more efficient. I also disagree that the I4 works harder than the I6 as said above. It's doing the same amount of work with 2 less cylinders that are basically the same size as those in the N52. It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel. It only works hard when you put your foot into it and spool up the turbos. These 4 cylinders are not turning at higher RPM than those of the I6 and in fact make more power at lower RPM.
My glib answer of "physics" assumed some grounding in physics, so I apologize for not being more clear.

Your statement "It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel" only makes sense if you discount the element of time. If you said, "A 4 cylinder could do the work of 6 with 33% less fuel if it were given 33% more time to do the work", then that's a statement I could agree with in principle. However when both engines have to perform the same work in the same amount of time, you can't expect a 33% advantage.

Since the N20 and N55 share the same basic architecture it makes for a pretty simple conversation - to accelerate at the same rate the N20 must rev higher. Both the N20 and N55 are doing the same amount of work when accelerating at the same rate, however the N20 is revving higher. Yes the N55 has to push more pistons, but the N20 has to rev a bit more; obviously in the EPA test these different approaches to performing the same work offset each other pretty closely. YMMV in the real world as you mention, especially for drivers that accelerate slowly.

Where I would expect the N20 to be more efficient is steady-state cruising at moderate rpm. In that case the superior torque of the N55 is not needed and the additional reciprocating mass, etc of the N55 takes its toll. And indeed this is borne out by the 328i's superior highway mpg rating. In theory I'd expect this to break down at higher speeds as wind resistance increases the need for torque, so at some point the N20 would start revving higher than the N55.
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Old 11-16-2013, 08:52 PM
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Quote:
Originally Posted by chiefneil View Post
My glib answer of "physics" assumed some grounding in physics, so I apologize for not being more clear.

Your statement "It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel" only makes sense if you discount the element of time. If you said, "A 4 cylinder could do the work of 6 with 33% less fuel if it were given 33% more time to do the work", then that's a statement I could agree with in principle. However when both engines have to perform the same work in the same amount of time, you can't expect a 33% advantage.

Since the N20 and N55 share the same basic architecture it makes for a pretty simple conversation - to accelerate at the same rate the N20 must rev higher. Both the N20 and N55 are doing the same amount of work when accelerating at the same rate, however the N20 is revving higher. Yes the N55 has to push more pistons, but the N20 has to rev a bit more; obviously in the EPA test these different approaches to performing the same work offset each other pretty closely. YMMV in the real world as you mention, especially for drivers that accelerate slowly.

Where I would expect the N20 to be more efficient is steady-state cruising at moderate rpm. In that case the superior torque of the N55 is not needed and the additional reciprocating mass, etc of the N55 takes its toll. And indeed this is borne out by the 328i's superior highway mpg rating. In theory I'd expect this to break down at higher speeds as wind resistance increases the need for torque, so at some point the N20 would start revving higher than the N55.
Great answer.
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Old 11-16-2013, 09:23 PM
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Originally Posted by chiefneil View Post

"......Where I would expect the N20 to be more efficient is steady-state cruising at moderate rpm. In that case the superior torque of the N55 is not needed and the additional reciprocating mass, etc of the N55 takes its toll. And indeed this is borne out by the 328i's superior highway mpg rating. In theory I'd expect this to break down at higher speeds as wind resistance increases the need for torque, so at some point the N20 would start revving higher than the N55."
Totally agree with this simply based on the cylinder shutdown technology used by some manufacturers to get higher hwy. MPG from larger engines! It has been proven!
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Old 11-16-2013, 09:35 PM
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Totally agree with this simply based on the cylinder shutdown technology used by some manufacturers to get higher hwy. MPG from larger engines! It has been proven!
Does the N55 not turn off half of its cylinders while cruising? I just assumed that that was pretty much standard on all 6 cylinder cars these days.
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Old 11-16-2013, 09:40 PM
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Does the N55 not turn off half of its cylinders while cruising? I just assumed that that was pretty much standard on all 6 cylinder cars these days.
No. I was pointing out that based on cylinder shutdown technology it has been proven that once a vehicle reaches cruising speed, a 3 or 4 cylinder engine will get better gas mileage than a 6 or 8 because it takes much less torque/horsepower to maintain speed, therefore the extra cylinders are just burning more fuel.
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Old 11-17-2013, 03:56 AM
Michael Schott Michael Schott is offline
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Quote:
Originally Posted by chiefneil View Post
My glib answer of "physics" assumed some grounding in physics, so I apologize for not being more clear.

Your statement "It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel" only makes sense if you discount the element of time. If you said, "A 4 cylinder could do the work of 6 with 33% less fuel if it were given 33% more time to do the work", then that's a statement I could agree with in principle. However when both engines have to perform the same work in the same amount of time, you can't expect a 33% advantage.

Since the N20 and N55 share the same basic architecture it makes for a pretty simple conversation - to accelerate at the same rate the N20 must rev higher. Both the N20 and N55 are doing the same amount of work when accelerating at the same rate, however the N20 is revving higher. Yes the N55 has to push more pistons, but the N20 has to rev a bit more; obviously in the EPA test these different approaches to performing the same work offset each other pretty closely. YMMV in the real world as you mention, especially for drivers that accelerate slowly.

Where I would expect the N20 to be more efficient is steady-state cruising at moderate rpm. In that case the superior torque of the N55 is not needed and the additional reciprocating mass, etc of the N55 takes its toll. And indeed this is borne out by the 328i's superior highway mpg rating. In theory I'd expect this to break down at higher speeds as wind resistance increases the need for torque, so at some point the N20 would start revving higher than the N55.
Thanks. I guess that an N20 to N55 comparison is difficult to begin with as one is rated at 240 HP and the other 300 so the added displacement automatically means the N55 makes power more easily but then again the N20 is not as fast which makes sense. It can never work as hard as the N55 because of the smaller displacement.

The reason the F30 N55 gets better mileage than the E90 N55 is a better question and is entirely related to the new ZF 8AT.

In regards to the original question by the OP which I've strayed from, I believe that the EPA test cycle benefits the 335 but everyday driving benefits the N20 and as I mentioned above, I see a significant decrease in consumption between my E90 N52 MT and my F30 N20 MT.
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Old 11-17-2013, 04:52 AM
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Quote:
Originally Posted by chiefneil View Post
My glib answer of "physics" assumed some grounding in physics, so I apologize for not being more clear.

Your statement "It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel" only makes sense if you discount the element of time. If you said, "A 4 cylinder could do the work of 6 with 33% less fuel if it were given 33% more time to do the work", then that's a statement I could agree with in principle. However when both engines have to perform the same work in the same amount of time, you can't expect a 33% advantage.

Since the N20 and N55 share the same basic architecture it makes for a pretty simple conversation - to accelerate at the same rate the N20 must rev higher. Both the N20 and N55 are doing the same amount of work when accelerating at the same rate, however the N20 is revving higher. Yes the N55 has to push more pistons, but the N20 has to rev a bit more; obviously in the EPA test these different approaches to performing the same work offset each other pretty closely. YMMV in the real world as you mention, especially for drivers that accelerate slowly.

Where I would expect the N20 to be more efficient is steady-state cruising at moderate rpm. In that case the superior torque of the N55 is not needed and the additional reciprocating mass, etc of the N55 takes its toll. And indeed this is borne out by the 328i's superior highway mpg rating. In theory I'd expect this to break down at higher speeds as wind resistance increases the need for torque, so at some point the N20 would start revving higher than the N55.
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Old 11-17-2013, 04:34 PM
Kayani_1 Kayani_1 is offline
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At no point does the N20 make more horse power or torque then a inline-6 N55 or N54. Even at 1300 rpm the N55 is making close to 175 lb-ft of rear wheel torque and N20 is merely making 130 lb-ft of rear wheel torque. By the time rpms rise to 2500 rpm the N55 is making close to 270 lb-ft of rear wheel torque and N20 is merely at 225 lb-ft of rear wheel torque.





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These 4 cylinders are not turning at higher RPM than those of the I6 and in fact make more power at lower RPM.
[/quote]
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Old 11-17-2013, 06:23 PM
Michael Schott Michael Schott is offline
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At no point does the N20 make more horse power or torque then a inline-6 N55 or N54. Even at 1300 rpm the N55 is making close to 175 lb-ft of rear wheel torque and N20 is merely making 130 lb-ft of rear wheel torque. By the time rpms rise to 2500 rpm the N55 is making close to 270 lb-ft of rear wheel torque and N20 is merely at 225 lb-ft of rear wheel torque.




[/QUOTE]
Sorry for not being clear. I was referring to the N52 in that post.
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Old 11-17-2013, 10:18 PM
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Quote:
Originally Posted by chiefneil View Post
My glib answer of "physics" assumed some grounding in physics, so I apologize for not being more clear.

Your statement "It only makes sense that using 4 equal size cylinders to do the job of 6 uses in theory 33% less fuel" only makes sense if you discount the element of time. If you said, "A 4 cylinder could do the work of 6 with 33% less fuel if it were given 33% more time to do the work", then that's a statement I could agree with in principle. However when both engines have to perform the same work in the same amount of time, you can't expect a 33% advantage.

Since the N20 and N55 share the same basic architecture it makes for a pretty simple conversation - to accelerate at the same rate the N20 must rev higher. Both the N20 and N55 are doing the same amount of work when accelerating at the same rate, however the N20 is revving higher. Yes the N55 has to push more pistons, but the N20 has to rev a bit more; obviously in the EPA test these different approaches to performing the same work offset each other pretty closely. YMMV in the real world as you mention, especially for drivers that accelerate slowly.

Where I would expect the N20 to be more efficient is steady-state cruising at moderate rpm. In that case the superior torque of the N55 is not needed and the additional reciprocating mass, etc of the N55 takes its toll. And indeed this is borne out by the 328i's superior highway mpg rating. In theory I'd expect this to break down at higher speeds as wind resistance increases the need for torque, so at some point the N20 would start revving higher than the N55.
Which fits the EPA test cycle. The EPA test is performed with virtually perfect precision from vehicle to vehicle, including the same rate of acceleration during each phase of the test no matter what size motor or vehicle. Test drivers are trained and experienced and they follow a precise driving pattern that is projected onto a screen in front of them.
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  #23  
Old 11-18-2013, 07:32 AM
Jamesonsviggen Jamesonsviggen is offline
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There are times when the N20 exploits the smaller displacement and then times it gives up any advantage to the N55 due to utilizing twice the boost.

This is all largely dependent on driving style.

When trying to test absolute economy, 75-80mph, a few traffic lights, a minute of stop and go, I got 39.9mpg out of my 6mt N20 and 35.5mpg out of an 8spd N55. Now had I flogged both cars the gap may have shrunken a fair bit. But on the easy driving, had the N55 been a 6mt, the gap would have worsened. So your driving style dictates that gap.
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Old 11-18-2013, 01:23 PM
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Re: Anyone notice that the 428i only gets 1 mpg better in the city compared to the 43

All of these comparisons remind me of when "Top Gear" did a gas mileage comparison between a Prius and an M3. For those who have never seen it, they drove the Prius around the track as hard as they could, and all the M3 driver had to do was keep up. The M3 won! (More fuel efficient!)

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Old 11-18-2013, 03:30 PM
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All of these comparisons remind me of when "Top Gear" did a gas mileage comparison between a Prius and an M3. For those who have never seen it, they drove the Prius around the track as hard as they could, and all the M3 driver had to do was keep up. The M3 won! (More fuel efficient!)

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One of the best TG episodes I've seen
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