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Old 17th January 2006, 13:11   #1
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Default V-6 or I-6?

Is a V-6 engine superior to an I-6, meaning straight-six or inline-six?

I would imagine that a V-6 being compact as it is only 3-cylinders long, would be preferred for fitment in a front-wheel drive small car, where most likely it would be mounted transversely.
Big rear-wheel drives, like BMWs, Volvos, Jaguars and even Nissan Skylines with no space restrictions would have a straight-six. Then a straight-six with one-cylinder head and one camshaft is simpler and smoother.
On the other hand a V-6 is always unbalanced, vibrates like crazy and needs counter balance shafts and harmonic damping.

In 1959 when Standard-Triumph of England introduced the Standard Herald, they also conceived of a six-cylinder "power" version. Triumph engineers shoe-horned a 2-litre 6-cylinder engine into a Herald. The Italian designer Giovanni Michelotti conceptualized new front styling and the car was given a reworked, sturdier chassis frame than the Herald.
The result was a potent sporting saloon with its 2-litre engine giving 160 km/h performance. In its day it was a potent zippy sports car, and was positioned for the sports car enthusiast with a growing family.



That 2-door body, made in India by Standard Motors at Madras, but only with a 4-cylinder 958cc 39 bhp engine, was called Standard Herald Mark 2. Back in England, a 1971 2-litre (1998 cc) 6-cylinder Triumph Vitesse developed 104 bhp@5300 rpm.


I-6s on the other hand are high torque truck engines, while V-6 are bhp engines better suited to lightweight race cars.
Serious 4-wheel drive people, like those that do the Rubicon in California prefer straight sixes or vee-eights to vee-sixes, which are considered rather wimpy.
The old Willy Jeep CJ-5, to which our MM-540/550 is related had a Buick “Dauntless” V-6. But after that all US-made Jeeps have had straight-six high torque engines. Example: Jeep's strong 4-litre 185 bhp I-6 and our Nissan G-60 "Jonga" 4-litre 110 bhp straight-six. Some light Japanese 4x4s do come with V-6s, but they are more show and less go. Certainly not boulder bashers.

I welcome your comments.
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Old 17th January 2006, 14:18   #2
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hmmm...
I always thought V engines are better than I engines.. Did not think all theis before though

But, a good write up!!! Keep up the good job.
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Old 17th January 2006, 14:28   #3
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i think straight 6's are more refined??? lesser vibrations???smoother???

dont mock me guys..
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Old 17th January 2006, 15:58   #4
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im not much of a car guy but from what i know
inlines = sheer raw power.
v's = smooth,torquey ride.
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Old 17th January 2006, 16:46   #5
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Quote:
im not much of a car guy but from what i know
inlines = sheer raw power.
v's = smooth,torquey ride.
Exact opposite of ram's post!

An I6 anyday for me.
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Old 17th January 2006, 20:57   #6
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i think V6, coz less bulkier,more balanced (dynamic force balancing), hence less vibrations!!!
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Old 17th January 2006, 21:09   #7
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Quote:
Originally Posted by cbr1000f
im not much of a car guy but from what i know
inlines = sheer raw power.
v's = smooth,torquey ride.
What you mean is sheer raw torque.
An inline 6-cylinder design inherently has both primary and secondary balance.

Primary balance is when the crankshaft counterweights offset the weight of the piston and rod.
Secondary balance is when the movement of one piston balances the movement of another.

Now we can plainly see, V6s have a secondary imbalance that causes engine vibration.

Adding a counter balance shaft can reduce this imbalance, but that adds weight and complexity.
The "V" engine was designed to reduce size and weight.
What got sacrificed was smoothness. "V" engines vibrate too much.
All "V" engines run less smoothly than their equivalent straight in-line counterparts.
This applies to V4s, V6s and V8s.
A "V" engine also always has more wear-and-tear.

For what it's worth, let me say this. When I bought my 1979 Ford Mustang hatchback in Everett, Washington, I had a choice of Ford's turbosupercharged 2300 cc Lima in-line four-cylinder, Ford's 3-litre Essex V-6 and Ford's 5-litre V-8.
After driving all three cars, I found the 2.3 litre turbo the smoothest (and most fuel efficient). After 1981 Ford themselves discontinued the V6 and replaced it with a smooth I-6.

My first car, a 1974 Ford Maverick had a silky-smooth I-6 engine.



I also had a Pontiac Catalina Safari station wagon with a small-block 4.9 liter Pontiac 301-cid V8 mated to GM's Turbo-Hydramatic 350 automatic transmission.

Last edited by Ram : 17th January 2006 at 21:25.
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Old 17th January 2006, 23:01   #8
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World's lightest six cylinder engine is the new valvetronic I-6 that was launched with the E-90 3 series.
Its uses a magnesuim block.
Generally, V-6s have a short stiff cranks but need 2 sets of timing drives and package much better than an I-6.
But Daewoo has packaged an I-6 FWD for their flagship car (Verona)
With hydraulic mounts and such, vibration is now so low that it hard to tell if the engine is even running....let alone tell a V-6 apart from an I-6.
Only at very high rpms, do you feel any vibes. But........the I-6 is a dying breed.
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Old 19th January 2006, 14:57   #9
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Quote:
Originally Posted by Mpower
World's lightest six cylinder engine is the new valvetronic I-6 that was launched with the E-90 3 series.
It uses a magnesium block.
Generally, V-6s have a short stiff cranks but need 2 sets of timing drives and package much better than an I-6.
But Daewoo has packaged an I-6 FWD for their flagship car (Verona)
With hydraulic mounts and such, vibration is now so low that it hard to tell if the engine is even running....let alone tell a V-6 apart from an I-6.
Only at very high rpms, do you feel any vibes. But........the I-6 is a dying breed.
I guess the Suzuki Verona is what was to have been the Daewoo Leganza, had Daewoo survived.
It has a transverse-mounted 2.5 litre 24-valve straight-six that puts out 155 bhp and drives the front wheels.
Supposedly has a rave-worthy silky smooth BMW I-6 like character.

Seriously, most V-6s shake even if they have split-journal even-fire crankshafts, balance shafts, 60-degree banking, etc.

That's because they have untamable harmonics at certain engine speeds.
The larger the displacement, the worse the amplitude of the harmonics get, too.
Engine mounts - especially electrically valved hydraulic - can all but mask it to passengers, but those untamed harmonics are always present.

If you want a smooth six, the only way is a fully counterbalanced, seven main bearing, inline six cylinder.

Last edited by Ram : 19th January 2006 at 15:09.
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Old 19th January 2006, 22:17   #10
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Many of the american V-6 are born of slicing 2 cyls off a V8. Those are the 90 deg ones that need a balance shaft.

I-6 definetly has an edge for balance and vibration. But it depends on how you define superior? Mercedes converted from I to V6 for all their petrols in the late 90s and now their I-6 diesels are going to V-6 (280Cdi). Both Skyline and Supra lost went from I-6 to V-6. Today packaging is king. Front crash performance is also not good with an I-6.
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Old 20th January 2006, 22:56   #11
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The sound of the in-line six is rich. Just hear a BMW in-line six at high rpm. V6s just don't sound right!! You can say, that's just my opinion, and you won't be wrong!
BMW has a 3.2L in-line 6 that puts out 333hp.
Mercedes just took the cheaper, high volume approach when they came out with the V6.
They were driven by purely commercial interests (profit margins) rather than rich quality.
So says, Germany's respected "auto motor und sport" magazine.
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Old 21st January 2006, 06:49   #12
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[SIZE=2]How can I disagree. I have that very 3.2 L inline-6 sitting in my garage. [/SIZE]
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