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Advantages and disadvantages of the I-6

1.3K views 26 replies 21 participants last post by  GT_McCann  
#1 ·
Iam not talking bout just the z's inline 6, iam talking in general, BMW, Porsche, Jeep, Z. How come V-6's are the choice in most cars? How come only high performance machines like the BMW and porsches and our z's use the I-6? Is it harder to manufacture? This is just me taking a guess bout inline-6's; they cant produce more hp than a v6 could, but make more torque than a v6 could. is this noob talk? tell me bout I-6's please.... anything , what is there deal? thanks
 
#2 ·
It's mostly about packaging.

A V6 is easier to fit inside the engine bay of a modern car and will leave more room for the FWD assembly.

I'm sure there are other considerations, but it's my understanding that this is the primary.
 
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#3 ·
They (inline 6) were darn good engines in their day and many fine sports cars used them. V8 took over from Staight 8 and so forth.

I don't know about Straight 16 vs V16 but they were there. I assume two eight cylinder engines was a bit long and in todays traffic when the front of the car arrives a half hour before the passengers - well maybe impractical too.

Better or perhaps more conenient engine designs and some advertising hype (ie - Hemi Engine) may also play a factor.

I'm sure you will get a lot of arguement about which engine is better.

Getting people to say why this or that engine is better and for what application is another matter.

Newer is not always "better" - but some old classic superior designs are just too costly to make in today's economy.



Post Edited (Mar 19, 10:33pm)
 
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#4 ·
It just has to do with costs and market trends. FWD is actually cheaper to build and the public ate them up during the 80's. Smaller cars, more interior... No more than that.

Fricken manufacturers.
 
#5 ·
I think the main factor is size and weight. The straight six is a heavy motor, and it does need more hood space.
 
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#7 ·
A lot of the advantage of an inline 6 is its balancing. an inline 6 has a natural balance too it and its very smooth, making a smooth power band, and not much vibration and so forth, that is why they have no need for a counter rotating shaft like inline 4's or v6's (and some modern v8's). but disadvantages include price, thats why you see them in expensive cars (M3's, supras, skylines, and so on). there is virtually no noticeable diference in v6 power vs inline 6 power, but you will generally see MUCH higher torque and hp numbers out of cars like the supra that have straight six's. and horsepower=torque x rpm so there is no reason (other than an engine being rpm restricted) why a v6 of comparable litreage and redline would outperform a straight 6 and visaversa.
 
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#9 ·
the only reason why a straight 6 would be heavier would be (if like a Z) it has a cast iron block and the v6 has a aluminum one. they are actually lighter (i6's) because they dont need as much cross-sectional support like a v6 does or any v configured engine for that matter, pretty much a block, head, oil pan, and some guts.
 
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#10 ·
Also:

V6 = lower center of gravity

I6: The head gets longer when hot. More so with a bi metallic config like the Z.

I remember seeing some old inline’s from like the 30’s (6 or 8cyc) had two-piece heads.
 
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#11 ·
The old Straight 16's were just two straight 8 blocks welded together and hsaring the same drive shaft.

(Interview with Jay Leno)
 
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#12 ·
i dont know of any Inline 16's (cadilac and im sure others made v16's) v16's of old had a problem with warpage, cranks were especially suseptable to bending and warping in those engines, even in some straight 8's
 
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#13 ·
After all these years, Jeep is just now ending production of their 4.0L I6 engines. I'm not sure why they want to stop making such an awesome engine, but it has lasted a long time. my 4.0L is an awesome engine. It has the torque to pull off a dead stop and it actually has a lot of high end HP. Although the motor redlines at on 6k, I can drop to third at 55mph and blow by anything in front of me like it's sitting still. I6's are great engines and I hate to see them go. Especially to such an inferior counterpart.
 
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#14 ·
Porsche is a flat six ! But all of the rest is answered above to my opinion !
 
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#15 ·
7 fricken main bearings

its stronger, and more rigid then all those girly v8's and such with only 5
 
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#16 ·
"Porsche is a flat six!" Depends on what Porsche you are thinking (they made more than boxters, and 911's you know)

With an inline engine format you would have more mains in the bottom end than a comparable cylinder "V" engine.

As to how much of a difference this makes, well, you see 1000 hp out of both formats so neither can be bad. My experience with I-6 BMW's and Datsuns is that they are a little smoother.

In the end the V format will prevail because of the want of s**tbox FWD cars.
 
#17 ·
inlines don't torque around in the chassis like a V motor does. When you have a V type motor and hit the gas the motor twist towards the passenger side, effectively taking weight off the drivers front tire and adding it to the passenger side, inline motors don't do this. Watch a dragster take off the drivers front tire always lifts first then the passenger twisting the chassis. This is not what you want coming out of corners.

This is one if not the main reason inline 6 Z's still beat V8 z's around race tracks, and also the reason why people tell you a Z loses all it's "nimbleness" when you go V8. However with the right chassis work V8 Z's are awesome and handle well beyond most peoples limits or guts, heck even stock chassis they still do pretty good until you race them on a track against an inline Z with equal suspension and tires.

Matt
 
#18 ·
It's easier to set a v6 sideways (crank parallel to the axle) in a car than a straight 6.
It's a pakaging thing--
Dan
 
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#19 ·
Matt,
Engine (multiplied by tranny ratio) torque in an IRS car is reacted within the chassis.

Engein torque in a live-axle car is reacted at the wheels/rear suspension, which is why they twist and pick up one of the fronts before the other.

Nothing to do with inline vs. V!
 
#20 ·
Strength, torque, and smoothness are the I6s advantage over a V6, V6s are better at everything else.

And not all V6s are have 4 mains instead of 7 like a I6, the GM 2.8L 60° V6 I was looking at had a lot more than fout, looked like 7 to me. So does VWs VR series v6s.
 
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#21 ·
""Porsche is a flat six!" Depends on what Porsche you are thinking (they made more than boxters, and 911's you know)"

Well, this thread is about 6 cylinder engines. There's never been a V6 or I6 Porsche that I've ever heard of. School me if I'm wrong...
 
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#22 ·
You guys are forgetting another major advantage of inline sixes. 1 head, 1 valve cover, 1 exhaust manifold, 1 timing chain, etc. If something goes wrong, it's cheaper and easier to replace.
 
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#23 ·
thats true, and yes, i dont know of ANY porsche car that has EVER had anything but a flat or boxer six, except for the 928 which had a v8, the 966 which had a dohc 4, and the 924 and 944 which shared the same sohc 4.
 
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#24 ·
2 reasons:

Common Theory:

It's a space thing, V engines are more compact

Conspiracy Theory:

V engines, by design, are designed to fail......Can't sell new cars if the old ones last forever.

Think of a piston going straight up and down in an straight engine. Now think of that same piston running on an angle. Over the years, gravity will win, causing that piston to wear on the bottom cylinder wall and over time wear out the engine.
 
#25 ·
A little off topic, but one "advantage" I enjoy in the Straight 6 is it's uniqueness. It's no rotary, but not many cars have then these days. One more reason my Z rocks!
 
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#26 ·
Long sexy hoods - instead of short boxes with wheels on what used to be a bumper.
 
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