Straight-6 vs V6 Question

[Jimmy Magnusson]

I'll start by saying that I'm not the best when it comes to engines. Therefore, I have a question to you guys here! Is there any preformance difference between a straight 6 cylinder engine and a V6 of the same cylinder volume? If so, how big is the difference? And if used in a race car, would one be favorable over the other?

[greenamex2]

In theory a V6 will be more powerful because a shorter, stiffer lighter crank allowing higher revs, and less frictional power losses due to fewer main bearings.

In reality difference in other aspects of the engines design is going to cause a far greater difference. The main is probably going to be bore size and it's affect on valve sizes. I don't know why but most production V6's are seriously over square compared to straight 6's and hence can accomodate much larger valves (when was the last time you heard a race engine builder say "I could fit larger valves but there is no point, they are big enough already!").

[greenamex2]

Oh yeah, and a v6 will GENERALLY be lighter, more compact and hence easier to package.

[austin_ob]

you'll find that v6 is better power wise but an advantage of a straight is probably the best ballanced engine there is as regards firing order and i suppose you could say that its easy to work on a straight 6.

[Al Weyman]

I know a couple of guys who tried to make the straight 6 Opel engine work in ModProds and spent large disproportionate ammounts of dosh and as I understood it one of the weaknesses was crankshaft twist causing timing problems (cam and/or ignition cannot remember the full specifics) and front damper problems. IMHO something like the V6 Chevy or Ford engines are way better than a straight 6.

[esper]

Hi All, to find you here? but nevermind the emotional side between V6 and 6 line is the sound . A stright six is unbeatable in that aspect , apart from a v12.

But to all the other aspects its a v6 !!!

[johnny yuma]

The V6 being shorter can be set further back in a rwd car better balance/handling.The V6 does not have the 6300 rmm destructive harmonic of the straight six,but apart from that the straight six in "the only cylinder layout to have perfectly even firing impulses" [source forgotten].Seven main bearings in an inline six helps,but this and big bores makes them a bit long.
The V6 would have the opposite problem -if the stroke was long the motor would grow wide at the top,especially in say a 60 deg.V6.The V6 seems a better racing proposition in theory at least.

[zac510]

Once BMW, TVR and Ford Australia stop making inline 6s, will any manufacturer ever design another brand new inline 6?
We haven't seen a bespoke motorsport inline 6 for a long time. The packaging and vehicle dynamics advantages that johhny and denis outlined are becoming more important in road cars too!

[greenamex2]

I can't see BMW stopping in the short term, although it is interesting that the new M3 went V8 rather than the bigger capacity inline 6.

[Raglanparade]

i like my Falcon with the Inline6... sounds Purrrrfect

[chunder]

Think much like an inline 4 there is only so far you can go with the size of the block

And by the way some of the most powerful tuned engines around are straight six.

Although they are turbo the Nissan and Toyota straight six are also very good and probly able to go quite well N?A coz of the huge bottom end strengthening parts available due to the 1000hp plus turbo engines requirements in drag spec.

[gttouring]

V6..well the sound is never like a Straight 6..but this is a tough one..
I am leaning towards V6

[zac510]

chunder, that has less to do with their build (although they are strong) and far more to do with the prevalence of the things.

[trikesrule]

Inline six vs V6 = how much $ have u got and what do u need it to do? V6 potentially will package way better leading to a better balanced chassis. I wouldn't tow a stockie with a V6 - no guts (torque). My inline Falcon 6 will out pull a std V6 (or V8) any weekend up a mountain range.....trikes

[Al Weyman]

My Vortex V6 Blazer pulls my heavy chevy on a 6 wheeler commercial trailer OK Trikes.

[esper]

my inline 6 racer doesn't pull anything, its the sensation, the sound the vibes,
they call it the handsome brute..................what to compare

and when its pulled its either by a 6 litre native dutch quality diesel (inline!! theres no better) or a 7.4 americaniron v8 but, its always waiting untlll we can fire the british 3000 6 inline gun .

[Notso Swift]

Originally Posted by zac510

Once BMW, TVR and Ford Australia stop making inline 6s, will any manufacturer ever design another brand new inline 6?

TVR is not that old a design
GM have just released one in one of thier Daewoo thing, Volvo have theirs as well, not to mention the Toyota's. And there are quite a few Diesels still (though not passenger, more 4wd or commercial).

[JohnD]

Johnny YUma,
The destructive harmonic of the straight six at 6300 rpm.

Is this intrinsic to the straight six design? I understand about harmonics etc. but Googling several ways for more info. doesn't find anything.
Please say more
John

[Al Weyman]

Originally Posted by esper

my inline 6 racer doesn't pull anything, its the sensation, the sound the vibes,
they call it the handsome brute..................what to compare

and when its pulled its either by a 6 litre native dutch quality diesel (inline!! theres no better) or a 7.4 americaniron v8 but, its always waiting untlll we can fire the british 3000 6 inline gun .

Hey esper when I get a moment I will post some pictures up from the 60's of my 'Road' racer Healy 3000 which got me more chicks (we used that word in those days) and looks than any other car you can imagine, I warn you though purist Healy enthusiasts will NOT like it because, well I wanted a Cobra and there were no kits about then so I sort of altered the old girl a bit if you know what I mean. It did have raised compression and a twin system with massive tail pipes and sounded awesome when it fired up.

Oh I also took some inspiration from Mrs Segals works Healy that was based a mile or three from where I lived and was always parked outside her house!

[Rubinho]

Don't forget that the flat 6 (a la Porsche) is also perfectly balanced in the 1st and 2nd order as well as the inline 6 and V12.

The reason for the balancing is indeed intrinsic to the design. There are two main aspects, balance of forces (up/down displacement) and balance of moments (see-saw motion). A perfectly balanced engine, due to it's layout, will always have motion in equal and opposite directions at the same time.

[trikesrule]

Just re reading some of the posts here and something struck me. Dennis do your engines have main bearing problems? My engine bearings run pressurised oil between each slipper. Tell us about yours......sorry Denis or was it an oxymoron?.......trikes

[jonners]

Given the impressive outputs achievable with BMW M series straight sixes and Nissan Skylines there can't be much wrong with the basis 'format' of a straight six - must've been something specific to the Opel/Vauxhall engine

Given their attachment to the big front engined rear wheel drivers, have always wondered why BMW have never tried a v6 given the packaging and handling advantages - as stated above the new M3 is a v8 as was the old M5.

The M3 started as a four, then straight six, then v8. The M5 started as a straight six then v8 now v10.

In other words everything except a v6.

Must be a reason....

[esper]

Originally Posted by Al Weyman

Hey esper when I get a moment I will post some pictures up from the 60's of my 'Road' racer Healy 3000 which got me more chicks (we used that word in those days) and looks than any other car you can imagine, I warn you though purist Healy enthusiasts will NOT like it because, well I wanted a Cobra and there were no kits about then so I sort of altered the old girl a bit if you know what I mean. It did have raised compression and a twin system with massive tail pipes and sounded awesome when it fired up.

Oh I also took some inspiration from Mrs Segals works Healy that was based a mile or three from where I lived and was always parked outside her house!

so after all its all down to a "compromise" , its sounds as loving a woman. still wondering why healeys keep being that popular!!!!!!!!