Emira weight distribution

[GrahamClark_60-68]

Ok, to preface this noob of the century question I recall the following saying “Better to stay silent and be thought the fool than to speak and remove all doubt.” But after much thought and many Google searches that have come up naught, I’m throwing caution to the wind here.

On weight distribution of the Emira V6 wrt other mid engine cars I understand that the engine positioning which is pretty much over the rear axle rather than more forward of the rear axle puts the car more in the category of “mid-rear” engine rather than “true” mid engine. A quick glance at the specs of the Espirit V8 and Ferrari 308 as a comparison surprisingly (at least to me) shows only slightly more mid bias (2-3%) than the Emira, I’m guessing attributed to the lighter power plant on the Emira. And I do appreciate the extra space I get behind the seats as a result as opposed to these other cars with the seats right up against the firewall.

But…. I’ve always been baffled by the left to right bias of the engine on the Evora and Emira (biased to the right looking from rear of the car). If I didn’t know its origins were British I could chalk it up to the driver being on the left and no passenger (i.e., better balance on the track and for solo driving). But of course for those of you driving on the wrong side of the car and road that would be double trouble (driver and engine on the same side of the car).

I also thought that maybe I was just looking at the supercharger cover and maybe it was offset to the right somehow and the engine itself was actually centered left to right but in the many assembly pictures I’ve seen that doesn’t seem to be the case and it does appear the engine itself is more to the right of the car.

So with this said, yes I’m out of ideas. Can someone help me out with my insanity?

 

[KAR120C]

The transmission is off the shelf as far as dimensions go, so I’m sure they didn’t want to develop a new unit.

 

[me73]

Interesting. I didn’t realize the position of the engine relative to the rear axel was fixed. I assumed you could move the engine forward without moving the rear axel but that they didn’t to save engineering costs. Sounds like there is an engineering constraint.

The transmission determines where the drivetrain mass is relative to the axle. In a front drive car it's beneficial to get the engine as close to the axle as possible for weight distribution and packaging. Unless Lotus was to design a different transmission, they're limited. You can move the relative axle position a little but it starts to effect some behaviors of the car and longevity of the parts.

 

[geoffbland]

Interesting. I didn’t realize the position of the engine relative to the rear axel was fixed. I assumed you could move the engine forward without moving the rear axel but that they didn’t to save engineering costs. Sounds like there is an engineering constraint.

With the engine being mounted transversely, the gearbox is mounted to the side of the engine, on the left-hand side of the car. A half-shaft comes out of the gearbox directly into the left-hand wheel. Another longer half-shaft also comes out of the gearbox travels under the engine to the right hand wheel. I think I have that right, difficult to tell from the service manual as there's no "overall" diagram just smaller detailed ones. Hopefully someone will correct me if I am wrong.
So you may be able tilt the top of the engine forward slightly (might be oiling issues with that) to improve centre of mass. But to move the engine forward without a complete redesign of the transmission you would need some extra linkages to the half-shafts as there would not longer be inline with the gearbox. That would mean extra complexity, more transmission losses and an extra failure point.

It's also worth pointing out that the v6 engine only weights +170KG so around only 12% of the dry weight of the car.

 

[GrahamClark_60-68]

With the engine being mounted transversely, the gearbox is mounted to the side of the engine, on the left-hand side of the car. A half-shaft comes out of the gearbox directly into the left-hand wheel. Another longer half-shaft also comes out of the gearbox travels under the engine to the right hand wheel. I think I have that right, difficult to tell from the service manual as there's no "overall" diagram just smaller detailed ones. Hopefully someone will correct me if I am wrong.
So you may be able tilt the top of the engine forward slightly (might be oiling issues with that) to improve centre of mass. But to move the engine forward without a complete redesign of the transmission you would need some extra linkages to the half-shafts as there would not longer be inline with the gearbox. That would mean extra complexity, more transmission losses and an extra failure point.

It's also worth pointing out that the v6 engine only weights +170KG so around only 12% of the dry weight of the car.

Thanks for that explanation, as I’ve been wondering how a transverse engine actually connects with the wheels. So if I understand correctly, the engine itself can be basically as it is from Toyota (out of a Camry) but it seems the transmission would have to be either full custom or a modification of an existing unit to allow for these two half shafts to connect up to the drive wheels? Or is the trans also basically “normal” and just the drive shaft coming out of the trans is some custom origami two part thing? (Sorry for the partial detour on my own thread but this is pretty interesting to me). And presumably this design was lifted straight from the Evora?

 

[KAR120C]

Thanks for that explanation, as I’ve been wondering how a transverse engine actually connects with the wheels. So if I understand correctly, the engine itself can be basically as it is from Toyota (out of a Camry) but it seems the transmission would have to be either full custom or a modification of an existing unit to allow for these two half shafts to connect up to the drive wheels? Or is the trans also basically “normal” and just the drive shaft coming out of the trans is some custom origami two part thing? (Sorry for the partial detour on my own thread but this is pretty interesting to me). And presumably this design was lifted straight from the Evora?

Transmission is stock dimensions. Lotus changes internal gears and cuts out a piece of the casing so starter fits.

It’s from a truck. Probably why 1st and 2nd are a little noisy.

 

[geoffbland]

Thanks for that explanation, as I’ve been wondering how a transverse engine actually connects with the wheels. So if I understand correctly, the engine itself can be basically as it is from Toyota (out of a Camry) but it seems the transmission would have to be either full custom or a modification of an existing unit to allow for these two half shafts to connect up to the drive wheels? Or is the trans also basically “normal” and just the drive shaft coming out of the trans is some custom origami two part thing? (Sorry for the partial detour on my own thread but this is pretty interesting to me). And presumably this design was lifted straight from the Evora?

I know very little about the US Camry. If the Camry has the V6 as a front engine, transverse mounted then you will have something very similar with a side mounted gear box and half-shafts too I guess? The Emira gear box is not made by Toyota but not a Lotus specific one either, not sure if the same unit was used on the Evora and the V6 Exige. Hopefully someone else can provide the details.

I can't remember which car it is now - but there is a car where to allow the transverse engine to sit lower in the car, one of the half-shafts actually travels through the engine rather than under it.

 

[GrahamClark_60-68]

I know very little about the US Camry. If the Camry has the V6 as a front engine, transverse mounted then you will have something very similar with a side mounted gear box and half-shafts too I guess? The Emira gear box is not made by Toyota but not a Lotus specific one either, not sure if the same unit was used on the Evora and the V6 Exige. Hopefully someone else can provide the details.

I can't remember which car it is now - but there is a car where to allow the transverse engine to sit lower in the car, one of the half-shafts actually travels through the engine rather than under it.

Sorry you’re right, “normal” in my brain was it was longitudinally mounted and rear wheel drive in the Camry. Just Google’d it and yea, duh, it’s transverse and front wheel drive so I guess a similar config for the Evora/Emira. My bad.

 

[GrahamClark_60-68]

Transmission is stock dimensions. Lotus changes internal gears and cuts out a piece of the casing so starter fits.

It’s from a truck. Probably why 1st and 2nd are a little noisy.

I guess you’re right but I’ve never felt a 6 speed manual as tight as the Emira in any truck I’ve ever driven. I suppose linkage plays a big part in that. What truck?

 

[freefall_junkie]

I know very little about the US Camry. If the Camry has the V6 as a front engine, transverse mounted then you will have something very similar with a side mounted gear box and half-shafts too I guess? The Emira gear box is not made by Toyota but not a Lotus specific one either, not sure if the same unit was used on the Evora and the V6 Exige. Hopefully someone else can provide the details.

I can't remember which car it is now - but there is a car where to allow the transverse engine to sit lower in the car, one of the half-shafts actually travels through the engine rather than under it.

The gearbox is the Aisin EA60, same as the Evora and v6 Exige. Aisin is owned by Toyota. The box was used in the diesel Toyota Auris - exotic it ain't