Transverse mid engined cars

[Scuffers]

Captain Muppet said:

Sorry, I meant a typical modern gearbox, as used in any of the modern transverse mid-engined cars in this thread. MR2s, MGs and Lotuses.

For a given engine transverse doesn't make the engine higher than longitudinal. If your engine CofG is too high you need a different engine, not to fit the same engine the other way round.

to a point, yes, but just because the engine/box are a fixed item to each other does not mean you can't rotate the whole package.

what I am getting at is that in a FWD scenario, you want the drive line as far forward as possible whilst keeping the engine as far back as you can get, some of this is achieved by slanting the engine over the driveline (this also keeps the bonnet height down at the front of the car).

now, when you then use the same powertrain in a mid-engined setup, the logical thing to do is to slant the engine the other way to keep it forward of the driveline (within the limits of the wet sump etc).

the alternative is to change the orientation of the bell housing on the engine, (or specing another gearbox) but that costs money and goes away from the std powertrain setup, thus unlikely unless you're into decent production numbers.

[MGJohn]

etchacan said:

Don't forget the MGF - may be Metro subframes and a parts bin special, but it fits the bill

And yes, I do have one...

PSSSST! This is PH. Mention of the MGF is poor form here. Yes, it fits the powertrain configuration bill precisely and I also have one which I enjoy as do many other owners.

The ignorant point out the MGF has some components shared with the Metro and see that as a negative. Whilst others like me see it as a positive.

My son has an Elise S2 ... with near identical powertrain.

[otolith]

I found a Car and Driver test of the 911 GT3 and 2011 Cayman R, in which they measured the height of the CoG. And reported only the difference between them, not the absolute figures. Doh!

It looks as if they do routinely measure it though, from this quote;

" I know from Car and Driver that the latest Porsche Cayman S center of gravity is kinda high at 20", the current MX-5 is 19", and the Scion FR-S is a low 18". My last car a 2011 Mustang GT was 21". Has anyone measured it for the Spyder, any educated guesses? "

http://www.spyderchat.com/forums/showthread.php?56...

Twenty inches - that's 508mm.

Presumably the height of the CoG needs to be understood in the context of the width of the track of the car?

[kambites]

otolith said:

Presumably the height of the CoG needs to be understood in the context of the width of the track of the car?

Indeed, but it hardly sounds as if the Cayman is making the most of its low mounted engine. I wouldn't be hugely surprised if the Evora was no higher than that.

[Captain Muppet]

Scuffers said:

Captain Muppet said:

Sorry, I meant a typical modern gearbox, as used in any of the modern transverse mid-engined cars in this thread. MR2s, MGs and Lotuses.

For a given engine transverse doesn't make the engine higher than longitudinal. If your engine CofG is too high you need a different engine, not to fit the same engine the other way round.

to a point, yes, but just because the engine/box are a fixed item to each other does not mean you can't rotate the whole package.

what I am getting at is that in a FWD scenario, you want the drive line as far forward as possible whilst keeping the engine as far back as you can get, some of this is achieved by slanting the engine over the driveline (this also keeps the bonnet height down at the front of the car).

now, when you then use the same powertrain in a mid-engined setup, the logical thing to do is to slant the engine the other way to keep it forward of the driveline (within the limits of the wet sump etc).

the alternative is to change the orientation of the bell housing on the engine, (or specing another gearbox) but that costs money and goes away from the std powertrain setup, thus unlikely unless you're into decent production numbers.

I was replying to a post in which a chap said the transverse gearbox is under the engine. Context is important, although it does mean loads of tedious multi-quote posts which is no fun for anyone.

I spent a few years doing engine packaging for OEMs. If this thread is going to turn in to another day at work I'd rather just do another day of work.

[Scuffers]

Captain Muppet said:

I was replying to a post in which a chap said the transverse gearbox is under the engine. Context is important, although it does mean loads of tedious multi-quote posts which is no fun for anyone.

I spent a few years doing engine packaging for OEMs. If this thread is going to turn in to another day at work I'd rather just do another day of work.

fair enough...

[RobM77]

kambites said:

otolith said:

Presumably the height of the CoG needs to be understood in the context of the width of the track of the car?

Indeed, but it hardly sounds as if the Cayman is making the most of its low mounted engine. I wouldn't be hugely surprised if the Evora was no higher than that.

That's a genuine surprise to me. The engine is mounted extremely low, and it's also a flat configuration (although bear in mind the discussion on that in recent pages).

[MGJohn]

doogz said:

RobM77 said:

wasn't the person saying that, but I read it and thought no more of it as it sounded right to my untrained mind. What would make the CofG higher on a boxer (or a flat engine?) higher than a V? I'm trying to think what would offset the higher cylinder heads of the V. Genuine question - I have no strong feelings either way, but it just tickled my curiousity.

The boxer engine itself has a lower CoG than a V engine generally would.

But they tend to be mounted higher, to allow for the manifold underneath.

First time I lifted the bonnet on a Subaru, I was surprised at how high that "flat" engine was mounted.

[braddo]

I guess there is only so much influence the engine type can have on the centre of gravity.

In the Evora/Cayman context, you're talking about 50-100kg of engine weight being maybe 30cm higher or lower in a 1400kg car (i.e. if you put a V6 in the Cayman, the heads will obviously sit higher).

[kambites]

Probably more like 5-10cm.

Makes you wonder whether (from an engineering rather than marketing perspective) it's actually worth Porsche continuing to build boxer engines.

[Scuffers]

MGJohn said:

First time I lifted the bonnet on a Subaru, I was surprised at how high that "flat" engine was mounted.

kind of depends what you're calling an engine though...

lots of paraphernalia bolted to the top of it, but in terns of the major masses, bugger all.

[shoestring7]

otolith said:

I found a Car and Driver test of the 911 GT3 and 2011 Cayman R, in which they measured the height of the CoG. And reported only the difference between them, not the absolute figures. Doh!

It looks as if they do routinely measure it though, from this quote;

" I know from Car and Driver that the latest Porsche Cayman S center of gravity is kinda high at 20", the current MX-5 is 19", and the Scion FR-S is a low 18". My last car a 2011 Mustang GT was 21". Has anyone measured it for the Spyder, any educated guesses? "

http://www.spyderchat.com/forums/showthread.php?56...

Twenty inches - that's 508mm.

Presumably the height of the CoG needs to be understood in the context of the width of the track of the car?

Something not right there. The Toyburu's CoG is supposed to be less than 1" higher than a GT3 and lower than a Cayman, but the C&D then put the GT3's CofG only 0.5" lower than a Cayman.

SS7

[AW111]

Looking at some photo's of my MR2, the lowest points are
Exhaust (under drive shaft)
Sump
Bellhousing.

So if you dry-sumped it, you could rotate the engine forward for a lower cog.

I wonder if transverse v6's are rotated further back in their fwd homes to keep the front bank further back?

[otolith]

Scuffers said:

kind of depends what you're calling an engine though...

lots of paraphernalia bolted to the top of it, but in terns of the major masses, bugger all.

Sounds like the RX-8 engine bay - chock full of plastic bits, but the dense bit is the size of a builder's bucket and stuffed up under the scuttle.

[TheRealFingers99]

ravon said:

Wonder why no racing cars, where performance is the sole criteria, opt for the transverse, side gearbox, rear axle mounted engine route ?

Modern formula cars (at least) are all about aero. Which is why they, at least, are now boring longitudinal V or straight. Not even flat engines can cut it anymore.

[shoestring7]

TheRealFingers99 said:

ravon said:

Wonder why no racing cars, where performance is the sole criteria, opt for the transverse, side gearbox, rear axle mounted engine route ?

Modern formula cars (at least) are all about aero. Which is why they, at least, are now boring longitudinal V or straight. Not even flat engines can cut it anymore.

It has been tried:



SS7

[RobM77]

MGJohn said:

doogz said:

RobM77 said:

wasn't the person saying that, but I read it and thought no more of it as it sounded right to my untrained mind. What would make the CofG higher on a boxer (or a flat engine?) higher than a V? I'm trying to think what would offset the higher cylinder heads of the V. Genuine question - I have no strong feelings either way, but it just tickled my curiousity.

The boxer engine itself has a lower CoG than a V engine generally would.

But they tend to be mounted higher, to allow for the manifold underneath.

First time I lifted the bonnet on a Subaru, I was surprised at how high that "flat" engine was mounted.

Why can't the manifold be on top? Sorry if I'm hijacking the thread to ask basic engine questions!

[AW111]

doogz said:

Pardon?

Behind the block. Around about the crank centreline?

I'm going off visual memory. My mind's eye says about an inch above crank.

Car is in shed and it's cold and dark.

[xRIEx]

RobM77 said:

MGJohn said:

doogz said:

RobM77 said:

wasn't the person saying that, but I read it and thought no more of it as it sounded right to my untrained mind. What would make the CofG higher on a boxer (or a flat engine?) higher than a V? I'm trying to think what would offset the higher cylinder heads of the V. Genuine question - I have no strong feelings either way, but it just tickled my curiousity.

The boxer engine itself has a lower CoG than a V engine generally would.

But they tend to be mounted higher, to allow for the manifold underneath.

First time I lifted the bonnet on a Subaru, I was surprised at how high that "flat" engine was mounted.

Why can't the manifold be on top? Sorry if I'm hijacking the thread to ask basic engine questions!

It does have a manifold on top, as well as the one underneath.

[TheRealFingers99]

shoestring7 said:

TheRealFingers99 said:

ravon said:

Wonder why no racing cars, where performance is the sole criteria, opt for the transverse, side gearbox, rear axle mounted engine route ?

Modern formula cars (at least) are all about aero. Which is why they, at least, are now boring longitudinal V or straight. Not even flat engines can cut it anymore.

It has been tried:



SS7

It wasn't developed though. Arguably it couldn't be, but remember that even the D50 took around a year to be more than just competitive.

But Honda won the 1965 Mexican Grand Prix with their RA272.