Straight Six Advantages
Discussion
Was chatting with an old fella with a Ferrari yesterday. He was interested by the Tuscan - had never seen one before, like most people around here. He was also interested by the Straight Six engine and was talking about racing cars and how there have been a lot with Straight Sixes. Not the first time I've heard this and thought to learn a bit more about the Straight Six concept. Searched "straight six advantages" here but couldn't find any 
So had a look on the Net and found this much:
So, what's the deal then - advantages of Speed Six over V6's and 8/12 cylinders please!? Anyone here in a position to teach? - more responsive/higher revving (certainly seems it when I'm racing Griffs
) and/or what else..? I'd like to be a bit more engaging in the next conversation!
Cheers
So had a look on the Net and found this much: Net said:And found a 1930 Bently racer with a Straight Six that came 2nd at Le Mans
The laws of physics; a straight-six power unit offers the optimum physical configuration for a six-cylinder engine.
The near perfect inner balance of the straight-six means an absence of free mass forces.
The straight-six does not require balance shafts and elaborate engine mounts to overcome the inherent vibrations of other designs.
With valve drive systems becoming more complex, there are engineering advantages in having only one cylinder head and only one valve train.
So, what's the deal then - advantages of Speed Six over V6's and 8/12 cylinders please!? Anyone here in a position to teach? - more responsive/higher revving (certainly seems it when I'm racing Griffs
) and/or what else..? I'd like to be a bit more engaging in the next conversation! Cheers
It is true that straight six engines are inherently smoother - I believe it's the secondary forces which balance each other out, simply by virtue of having six cylinders and 360 degrees.
For a middling capacity engine, i.e. something from two to four litres, there's probably little to beat a straight six. Going above that you're going to run into problems with pistons being too big, or the stroke being too long. Either one is going to make the engine low on responsiveness and restrict its ability to rev. This is certainly part of the reason why TVR have gone down the supercharged route with the Typhon, rather than boring/stroking a bigger normally aspirated six.
A straight six means only one cylinder head, meaning lower costs, and higher reliability for the same effort. Twin overhead camshafts are the optimum configuration - with a V engine you're going to need four camshafts rather than two. Obviously this makes things more complex/expensive.
Packaging is one advantage with the V configuration. Just look at compact the AJP V8 is.
For a middling capacity engine, i.e. something from two to four litres, there's probably little to beat a straight six. Going above that you're going to run into problems with pistons being too big, or the stroke being too long. Either one is going to make the engine low on responsiveness and restrict its ability to rev. This is certainly part of the reason why TVR have gone down the supercharged route with the Typhon, rather than boring/stroking a bigger normally aspirated six.
A straight six means only one cylinder head, meaning lower costs, and higher reliability for the same effort. Twin overhead camshafts are the optimum configuration - with a V engine you're going to need four camshafts rather than two. Obviously this makes things more complex/expensive.
Packaging is one advantage with the V configuration. Just look at compact the AJP V8 is.
There was a thread a while ago about engine configurations (and flat plane cranks), it was about the AJP (but slated the Speed 6 because it was nowhere near balanced if I remember correctly).
Might be worth a search on the Cerb or engine forums.
In theory a straight 6 is smaller than a v6 and much revvier/more responsive than an 8 I think.
D
Might be worth a search on the Cerb or engine forums.
In theory a straight 6 is smaller than a v6 and much revvier/more responsive than an 8 I think.
D
_dj_ said:
In theory a straight 6 is smaller than a v6 and much revvier/more responsive than an 8 I think.
D
For the same engine capacity, an engine with greater cylinders should be more responsive and be able to rev to a higher limit. This is because the each piston can be smaller or the stroke can be reduced, reducing in either case the mass and consequently the rotational forces.
>> Edited by admiral on Monday 15th November 10:56
admiral said:
In theory a straight 6 is smaller than a v6 and much revvier/more responsive than an 8 I think.
D
For the same engine capacity, an engine with greater cylinders should be more responsive and be able to rev to a higher limit. This is because the each piston can be smaller or the stroke can be reduced, reducing in either case the mass and consequently the rotational forces.
>> Edited by admiral on Monday 15th November 10:56
I think you can exclude the RV8 from this ..
Gassing Station | General TVR Stuff & Gossip | Top of Page | What's New | My Stuff