Transverse mid engined cars
Discussion
AER said:
Yes, but there are still 101 compromises in all of those designs. If you want a low CoG, then get the crankshaft (the heaviest part of any engine) as low as possible. This will pretty much dictate a V-configuration by the time you've specified a dry sump and multi-plate clutch, á la F1 engine.
A longitudinal engine layout demands you turn the power through a less efficient 90°, so you've already accepted a compromise there too. It's horses for courses and budgets play a large part in how much hay your horses eat.
exactly...A longitudinal engine layout demands you turn the power through a less efficient 90°, so you've already accepted a compromise there too. It's horses for courses and budgets play a large part in how much hay your horses eat.
when all said and done, (as has been said already) it's really all about packaging.
Lotus Evora is a prime case in point, it's pushing the boundaries of being mid-engined becuse the engines pushed back high above the axle line to make space for the back seat, if it was longetudinal, that's just not possible.
obviously this has huge downsides in terms of COG etc, but that's the compromise in making it a mid-engined 2+2 (and why they are a very rare thing).
ravon said:
Yes Kambites, I have, an Evora, not a Noble or an Exige S. Didn't care for the twisted driving position, a bit like, but not as bad as, a right hand drive air-cooled 911, and thought the gear linkage was appalling, far worse than my M100 Elan which is two decades old !
Out of interest, do you actually think the Cayman handles better than the Evora overall? AER said:
Look a this! The Boxster crankshaft is so high they run the gearbox input shaft above the final drive axis!
Surely the heads are lower than a V6 though? I'm not saying that makes up for it, but whilst the crank weighs a fair bit, so do the cylinder heads and certain areas of the block. I'd like to see the engine's CofG rather than guessing. Also, how much lower and more central is the engine than a typical mid-engined layout?
I tried to link toa cut-away of an Audi R8 and similar, but most pages are blocked at work..
blueg33 said:
Am am just looking at a cutaway of the Evora and woyls suggest that the engine isn't as high as you suggest. The bulk of the mass is in line with the torso of the driver. I seem to recall that is similar in an F355 as an example.
not sure what your looking at but this is what I am getting at:
(this is without the supercharger bolted on top too)
yes, it's not at head hight, but it's not far off it, and whilst the crank may well be the single heaviest part, two twin-cam cylinder heads are not insignificant weights.
Indeed, having the gearbox that way around makes sense because the Porsche is wet sumped (I assume?) so needs clearance under the crank for the sump pan anyway. I don't see how you could get a wet sumped engine lower down than the Cayman's unless you actually had an inverted V (which would have interesting oil return problems 
).
On a slightly different but related note, that cutaway above makes it obvious why Porsche couldn't fit double wishbones at the rear, so the flat six does have its downsides.
). On a slightly different but related note, that cutaway above makes it obvious why Porsche couldn't fit double wishbones at the rear, so the flat six does have its downsides.
Edited by kambites on Friday 29th August 08:34
Kambites, I'd have to drive both back to back, on various circuits and roads with similar spec tyres to comment. I can only say the 981 Cayman utterly excels in all that I could ask of it, extraordinarily economical on normal road drives, 100mph down the Craner curves at Donington in completely standard form, faults, the only one that stands out is tyre noise, which is high, but to my amazement on route to Circuite de Bretagne a couple of weeks ago, as soon as the car hit French tarmac, the tyre noise was all but gone. So i'm guessing the suspension bushing isn't optimised for UK roads ?
What do you think of the way the 981 drives, how do you believe it compares to an Evora S ?
What do you think of the way the 981 drives, how do you believe it compares to an Evora S ?
ravon said:
What do you think of the way the 981 drives, how do you believe it compares to an Evora S ?
I don't because I haven't driven either. That's why I was asking someone who has. 
ETA: I've spent quite a lot of time in the 987 and 986 and obviously own an Elise so I have some experience of the basic layouts. I felt the 987 was a huge step backwards as a drivers' car from the 986 (which I think is quite an usual view) and neither can get anywhere near an Elise, but then I suppose you wouldn't expect them to weighing >50% more. I'd love to have a go in an Evora, I'm put off even trying the 981 by what I've read about the steering system (which has always been the single most important element of a drivers' car to me).
Scuffers said:
blueg33 said:
Am am just looking at a cutaway of the Evora and woyls suggest that the engine isn't as high as you suggest. The bulk of the mass is in line with the torso of the driver. I seem to recall that is similar in an F355 as an example.
not sure what your looking at but this is what I am getting at:(this is without the supercharger bolted on top too)
yes, it's not at head hight, but it's not far off it, and whilst the crank may well be the single heaviest part, two twin-cam cylinder heads are not insignificant weights.
I agree that the Evora engine sits higher that a longitudinal mounted engine and obviously higher than a boxer engine in a Cayman by virtue of the cylinder layout. I just dont think that the impact is as much as has been implied
otolith said:
But horizontal distribution of masses (distance from centre of mass) and height of centre of mass are also important, not just f:r ratio.
absolutely, yes. I was just responding to the specific point. This is of course why a 911 handles differently to an Elise, despite having a similar F:R bias; the polar moment is different.
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