more displacement--why
08-25-2010, 02:57 PM
#21
Senior Members
Join Date: Mar 2007
Location: North Carolina, USA
Posts: 1,517
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2008 BMW 550i
2006 BMW X3
I6 or V6 doesn't change the fuel economy, there are other more important factors. The biggest being the engine tune and gearing.
The Malibu V6 is deisgned to crusie at low RPMs and be efficient at 55mph.
The BMW 3.0 I6 (both NA and TT versions) is designed to be responsive and fun to drive at Autobahn speeds. You can't always have both (low RPM efficiency and high RPM performance).
Note the Corvette does a good job of this but I test drove a 5.7 400hp Vette back to back with my 5.0 400hp M5 at the time. In 6th gear & 60 mph the Vette was at 1500 RPMs and very flat performing while the M5 would be at 2000 RPMs and surprisingly peppy. The Vette had a MUCH more narrow power band than the M5.
The Malibu V6 is deisgned to crusie at low RPMs and be efficient at 55mph.
The BMW 3.0 I6 (both NA and TT versions) is designed to be responsive and fun to drive at Autobahn speeds. You can't always have both (low RPM efficiency and high RPM performance).
Note the Corvette does a good job of this but I test drove a 5.7 400hp Vette back to back with my 5.0 400hp M5 at the time. In 6th gear & 60 mph the Vette was at 1500 RPMs and very flat performing while the M5 would be at 2000 RPMs and surprisingly peppy. The Vette had a MUCH more narrow power band than the M5.
08-25-2010, 04:04 PM
#22
Contributors
Join Date: Jun 2008
Location: FT. Bliss Texas
Posts: 2,674
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2008 528i, Space Grey, Nav, PDC, Premium, Sports, Grey Leather, Xenon, Cornering...
08-25-2010, 04:23 PM
#24
Contributors
Join Date: Jan 2005
Location: San Jose, California, USA
Posts: 4,119
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2008 Porsche 911 Carrera S Convertible. Midnight Blue, 6 Speed.Retired - 2007 997 Carrera S, Midnight Blue, Grey leather, premium audioRetired - 2007 550i, Monaco Blue over Beige, Navigation, Logic 7, Cold Weather Pack, Comfort Access, Sport Package
Model Year: 2008
The BMW I6 engine is already a very long engine, physically longer than competing V6s and also V8s of often much larger displacement.
To increase displacement in an I6 will require an even longer engine to accomodate the physically bigger cylinder bores, assuming you are also preserving the amount of metal between the cylinder bores to maintain the structural strength and integrity of the engine. Alternatively, some very expensive cylinder wall reinforcement might let an engine of a larger displacement be engineered from the same size block if the physical gap between cylinders were to be reduced. Neither option is an easy or inexpensive challenge to solve. I agree a good V6 is, for practical purposes, essentially indistinguishable from a good I6 and it can of course fit into a smaller space. In sum, a larger displacement V6 or V8 can fit in the same physical space as a smaller displacement I6, and it is space requirements that most probably become the major limiting factor.
To increase displacement in an I6 will require an even longer engine to accomodate the physically bigger cylinder bores, assuming you are also preserving the amount of metal between the cylinder bores to maintain the structural strength and integrity of the engine. Alternatively, some very expensive cylinder wall reinforcement might let an engine of a larger displacement be engineered from the same size block if the physical gap between cylinders were to be reduced. Neither option is an easy or inexpensive challenge to solve. I agree a good V6 is, for practical purposes, essentially indistinguishable from a good I6 and it can of course fit into a smaller space. In sum, a larger displacement V6 or V8 can fit in the same physical space as a smaller displacement I6, and it is space requirements that most probably become the major limiting factor.
08-25-2010, 04:49 PM
#25
Super Moderator
Join Date: Jan 2008
Location: So. Cal (SFV)
Posts: 17,508
Likes: 0
Received 3 Likes
on
3 Posts
My Ride: 2011.5 Alpine White E90 M3 | Black Novillo Leather | Carbon Fiber Leather Trim | ZCP | ZP2 | M-DCT | Navigation | Moonroof | 6FL Mods: TMS 12.5mm spacers all around l Hawk HPS Brake Pads l OEM M3 Edition Grills l Paint Matched Side Gills l Key Hole D
The BMW I6 engine is already a very long engine, physically longer than competing V6s and also V8s of often much larger displacement.
To increase displacement in an I6 will require an even longer engine to accomodate the physically bigger cylinder bores, assuming you are also preserving the amount of metal between the cylinder bores to maintain the structural strength and integrity of the engine. Alternatively, some very expensive cylinder wall reinforcement might let an engine of a larger displacement be engineered from the same size block if the physical gap between cylinders were to be reduced. Neither option is an easy or inexpensive challenge to solve. I agree a good V6 is, for practical purposes, essentially indistinguishable from a good I6 and it can of course fit into a smaller space. In sum, a larger displacement V6 or V8 can fit in the same physical space as a smaller displacement I6, and it is space requirements that most probably become the major limiting factor.
To increase displacement in an I6 will require an even longer engine to accomodate the physically bigger cylinder bores, assuming you are also preserving the amount of metal between the cylinder bores to maintain the structural strength and integrity of the engine. Alternatively, some very expensive cylinder wall reinforcement might let an engine of a larger displacement be engineered from the same size block if the physical gap between cylinders were to be reduced. Neither option is an easy or inexpensive challenge to solve. I agree a good V6 is, for practical purposes, essentially indistinguishable from a good I6 and it can of course fit into a smaller space. In sum, a larger displacement V6 or V8 can fit in the same physical space as a smaller displacement I6, and it is space requirements that most probably become the major limiting factor.
08-25-2010, 07:52 PM
#29
Contributors
Join Date: Jan 2005
Location: San Jose, California, USA
Posts: 4,119
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2008 Porsche 911 Carrera S Convertible. Midnight Blue, 6 Speed.Retired - 2007 997 Carrera S, Midnight Blue, Grey leather, premium audioRetired - 2007 550i, Monaco Blue over Beige, Navigation, Logic 7, Cold Weather Pack, Comfort Access, Sport Package
Model Year: 2008
08-26-2010, 05:03 AM
#30
Members
Join Date: May 2008
Location: Cape Elizabeth, ME
Posts: 156
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2005 525i, 6spd manual, Premium pkg, Cold Weather pkg
Great thread. I especially like the post about increasing displacement. I was wondering about that myself; if it can be done, i.e. boring out the cylinders.