2012 Hyundai Equus.
Smoothest idle?
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Originally Posted By: 4WD
Boxer engine - movement is horizontally opposed
Porsche made a flat 12 but I can't comment on the idle..
Boxer engine - movement is horizontally opposed
Porsche made a flat 12 but I can't comment on the idle..
Originally Posted By: rooflessVW
Originally Posted By: Olas
BMW V12 in an 850i was the smoothest idling thing I've driven, it was surreal.
I've got another vote. We tried the "coin test" when I owned my 750i. You could start, rev, and stop the engine with a coin standing on the engine cover.
And the gear reduction starter made an awesome noise as well.
It's the same family of engines that eventually found their way into McLarens F1 - not noted for its civility.
How much influence do engine mounts make? I'd bet a V8 running on 7 could idle incredibly smoothly if it was supported solely on failed hydro mounts - in contrast changing the main two of my 30yr old mounts for factory items and replacing the supplementary mounts with Grp.4 'cup' items has made the perceived idle change from buttery smooth to noticeably vibrate - y.
A previous post mentioned NVH insulation which always make an engine 'seem smoother'
Originally Posted By: Olas
BMW V12 in an 850i was the smoothest idling thing I've driven, it was surreal.
I've got another vote. We tried the "coin test" when I owned my 750i. You could start, rev, and stop the engine with a coin standing on the engine cover.
And the gear reduction starter made an awesome noise as well.
It's the same family of engines that eventually found their way into McLarens F1 - not noted for its civility.
How much influence do engine mounts make? I'd bet a V8 running on 7 could idle incredibly smoothly if it was supported solely on failed hydro mounts - in contrast changing the main two of my 30yr old mounts for factory items and replacing the supplementary mounts with Grp.4 'cup' items has made the perceived idle change from buttery smooth to noticeably vibrate - y.
A previous post mentioned NVH insulation which always make an engine 'seem smoother'
1960 Lincoln. I actually saw a neighbor balance a NICKLE edge wise on the air cleaner while idling. Ed
Rotary engines have an advantage here, I remember working on a Mazda RX-8 in good condition, and the engine felt like it wasn't even there.
I have heard that the twin turbo 3-rotor engine found in the Eunos Cosmo is smoother than that, but I never encountered one, and I probably never will.
I have heard that the twin turbo 3-rotor engine found in the Eunos Cosmo is smoother than that, but I never encountered one, and I probably never will.
Surprised no one mentioned the old Straight Eights. I had a '39 Buick Eight Special with a 248ci Straight Eight, OHV with Hydraulic Lifters, Not only smooth but very quiet!! You could idle it down to 300 rpm & still smooth as glass.
The smoothest engines I have owned, with the best (smoothest) first.
BMW V12 in a 750iL
BMW 3.0 I6 in my wife's X3
GM 4.2L I6 in our old Trailblazer
BMW V12 in a 750iL
BMW 3.0 I6 in my wife's X3
GM 4.2L I6 in our old Trailblazer
#1 by a pretty wide margin- 1949 Plymouth 217.5 CI flathead six. Glassy-smooth all through the RPM range, but most remarkable at idle, even lugged down to 300 RPM or so. You can do that with a heavy crank, heavy flywheel, long connecting rods, inline-6 architecture, and 7:1 compression. 
#2- Too many to count or rank, including a lot of rental v6 and v8 engines as well as the two Pentastar v6's I've owned thus far.
"Smooth idle" hasn't ever been very high on my list of desirable characteristics, to be honest. As long as the steering wheel doesn't buzz (rules out most inline-4's) I'm happy. A big v8 with a lumpy idle is the best thing in the world.
#2- Too many to count or rank, including a lot of rental v6 and v8 engines as well as the two Pentastar v6's I've owned thus far.
"Smooth idle" hasn't ever been very high on my list of desirable characteristics, to be honest. As long as the steering wheel doesn't buzz (rules out most inline-4's) I'm happy. A big v8 with a lumpy idle is the best thing in the world.
I remember driving a Mercedes with a V-12 which was the smoothest running engine I encountered. I don't remember the particulars on the car, it was a long time ago. But it was smooth, quiet, and drove very nicely.
I sat in a running LS400 years ago, which definitely leaves an impression. With the doors shut, the only thing that even indicates the car is running is the backlit tach hovering around 850. Otherwise, you hear & feel nothing.
Compared to my two vehicles - an inline 4 with poly motor mount and a 205000 mile inline 6 that is losing compression in one cylinder ... pretty much anything.
The Honda J engines are super smooth for a "normal" engine.
The Honda J engines are super smooth for a "normal" engine.
That's pretty amazing!
Originally Posted By: rooflessVW
Originally Posted By: Olas
BMW V12 in an 850i was the smoothest idling thing I've driven, it was surreal.
I've got another vote. We tried the "coin test" when I owned my 750i. You could start, rev, and stop the engine with a coin standing on the engine cover.
And the gear reduction starter made an awesome noise as well.
Originally Posted By: rooflessVW
Originally Posted By: Olas
BMW V12 in an 850i was the smoothest idling thing I've driven, it was surreal.
I've got another vote. We tried the "coin test" when I owned my 750i. You could start, rev, and stop the engine with a coin standing on the engine cover.
And the gear reduction starter made an awesome noise as well.
For the old stuff, here are a few that come to mind that I have owned, been in or have seen:
1970 Ford Fairlane 302 V8
1966 Lincoln 462 ("MEL" design - not a 460) V8
1966 Plymouth Belvedere 318 "Poly" V8
1968 Olds Toronado 455 V8
1965 Chevy Impala 283 V8
1975 Chevy Malibu 350 V8
1972 Chevy Kingswood Estate 400 V8
1977 Chrysler Cordoba 400 V8
1977 Buick Century (Buick 350 V8)
1982 Datsun 210 1.5L
1974 Toyota Celica 2.0L
1974 and '76 Pontiac 400 V8
The newer cars have the advantage of "hydro" motor mounts and electronic engine management so finding a car with a very smooth idle after the mid-'80s (especially from how it feels inside the car) isn't that hard.
Andrew S.
1970 Ford Fairlane 302 V8
1966 Lincoln 462 ("MEL" design - not a 460) V8
1966 Plymouth Belvedere 318 "Poly" V8
1968 Olds Toronado 455 V8
1965 Chevy Impala 283 V8
1975 Chevy Malibu 350 V8
1972 Chevy Kingswood Estate 400 V8
1977 Chrysler Cordoba 400 V8
1977 Buick Century (Buick 350 V8)
1982 Datsun 210 1.5L
1974 Toyota Celica 2.0L
1974 and '76 Pontiac 400 V8
The newer cars have the advantage of "hydro" motor mounts and electronic engine management so finding a car with a very smooth idle after the mid-'80s (especially from how it feels inside the car) isn't that hard.
Andrew S.
Anything with more than 4 cyls will be smooth. I can't feel my 5 cyl Volvo running.
Originally Posted By: clinebarger
Surprised no one mentioned the old Straight Eights. I had a '39 Buick Eight Special with a 248ci Straight Eight, OHV with Hydraulic Lifters, Not only smooth but very quiet!! You could idle it down to 300 rpm & still smooth as glass.
That is because those cars became extremely rare before many BITOGers were even born.
Surprised no one mentioned the old Straight Eights. I had a '39 Buick Eight Special with a 248ci Straight Eight, OHV with Hydraulic Lifters, Not only smooth but very quiet!! You could idle it down to 300 rpm & still smooth as glass.
That is because those cars became extremely rare before many BITOGers were even born.
The straight eights (like a Packard) are very, very smooth at idle. When you get a nine-main bearing engine with eight cylinders, it's both dynamically balanced by having a firing pulse every 90 degrees and the crank is supported by all those bearings, resulting in super smooth operation, including idle.
The 60 degree V-12 is also incredibly smooth. Again, a matter of primary balance. Packard, again, built a V-12 in 1915 for that reason.
And, yeah, the V-12 in the S-600 is also very smooth at idle and under acceleration, because of the primary balance. It's one sweet engine.
The 60 degree V-12 is also incredibly smooth. Again, a matter of primary balance. Packard, again, built a V-12 in 1915 for that reason.
And, yeah, the V-12 in the S-600 is also very smooth at idle and under acceleration, because of the primary balance. It's one sweet engine.
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