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Esprit gearbox positions


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Throughout it's history, the one criticism the Esprit never fails to attract is over the gearbox.

This is mainly due to it's location, being right at the rear of the car, and the linkages required to connect the lever to the selectors.

Is this because the 4cyl and v8 engines were originally designed for front engine, RWD applications?

Do other mid engined supercars (Ferrari) have the gearbox on the other side i.e. designed for purpose?

I'm assuming that if the new Esprit goes for the M5 BMW unit (again front engine RWD), it risks a similar problem?

I personally think Lotus would be well advised to address the main (and only real) criticism of the Esprit.

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The gearbox is in the ideal position for a mid mounted engine design. The criticism is of the gearbox choice and the some times notchy gear change linkage. Quite a few cars now have cable operated gear linkage completely unknown to the owner so what can be expected is a far smoother gear change and one would hope a much better choice of gearbox from the start. The citreon box was always able to handle the power of the early S1 through to the S3 but suffered a bit with heavily driven S3 Turbo where the power output was reaching the limits of the power handling of the gearbox. Again the Renault box did a good enough job with the early S cars but with release of the V8 was very much on its limit. Despite this being a so called week point how may times have you read a post saying "I've blown another gearbox".

I am sure we can expect a very careful selection of gearbox when it comes to the new Esprit, after all I am sure Lotus would not like to repeat history with negetive feedback on their gearbox selection for their flagship model.

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Thanks for that

What got me thinking about it, was driving my gf's MX5, where the lever drops straight into the box, it's beautiful to drive.

I actually dont have a problem with my Esprit, I can change gear with 1 finger, it's just that there are better units/systems out there.

So is it possible to produce a gearchange as positive as say an MX5 with a cable system?

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If Lotus had put the gearbox in fron t of the engine the esprit would have made the early 911s look nose heavy.

The Porsche had the engine after the box, and suffered from the front of the car over-steering, with the Esprit being even lighter at the front it would be even more sensitive.

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Absolutely!

When we were at the M6 Toll day last weekend one of the scooby drivers was looking at the car and said - why is the engine there and not in the front? So we pointed out that it is in the optimum position for handling - why do you think F1 cars have them there.

He said "yes but F1 cars have no space at the front" so we pointed out that early F1 cars did indeed have engines in the front. He went quiet then!

F1 cars have the same basic layout as ours - mid engined with the gearbox behind the engine. This is the optimum layout for weight balance and handling.

Dave - 2000 Sport 350
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I'm sure a read somewhere the Testarossa has the gear box in front of the engine with a prop shaft then going back through the engine to the final drive which is at the rear of the engine. Something to do with the fact there simply wasnt room behind the huge flat 12 to have the gear box behind like the Esprit.

Thinking about it now, are Lambos the same? (Contach, Diablo, Merci)

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Gary, the downside of having a prop shaft running under the engine is that the engine needs to be raised and hence increases the height of the centre of gravity. Not that desirable for a sports car.

I'm sure that the Lambos have the prop shaft running under the engine.

Regards,

Peter.

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The mid engined position offers the best possibility for the car being balanced 50/50 front to rear. Why, because tyres work best in corners when they each carry 25% of the overall weight for as long as possible. The weight loadings though don't stay static but undergo a dynamic change, towards the outside tyres, as the car progresses through the corner.

This can be where suspension tuning becomes something of a "black art" for most or science for some like Lotus. Often cars are set far too stiff in springs and dampers resulting in premature weight transfer to the outside tyres. If the settings can be as soft as possible depending on the road and speed, energy can be absorbed by the springs and dampers rather than being tranferred too quickly to the outside tyres. Ideally this absorption of energy should reach its limit at the apex of the corner. Remember the key is to keep the loadings on the tyres at 25% each for as long as possible. With the mid engined setup this optimum weight distribution is easier to obtain than any other engine configuration. So why the bigger tyres on the rear? Dynamic weight transfer is mostly towards rear with the main exception being the front on braking.

There's also the advantage of a lower "polar moment of inertia" or how quickly a car can change direction. Think of how much easier it is to twist a kilo weight held in your hand compared to twisting two 500gram weights on the end of a bar held in your hand. Or to put it another way when you ride your bike the main mass of rider and engine is in the middle of the two wheels. Imagine how it would react if that weight was biased over the front or rear wheel.

Of course there are exceptions. Porsche have succeeded in making an "outboard" rear-engined car corner with the best. Then again they do it even better and easier with the Boxster which has a similar engine location to the Esprit.

DanR

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In some ways a mid engine layout is more effective & compact if the engine is mounted transversely like in the Elise, it frees up space & gear box/final drive positions isn

Edited by Splodge s4
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Gary,

I think the MR2, MGF & Elise all use a "relatively" small/light engine, so the cost of mounting it high above the gear box isn't too large. However, if you mount a larger/heavier engine up high it's going to have adverse effect on handling. However, not sure my O'level Physics necessarily qualifies me to comment on this issue. I'm sure there's some more intelligent people out there who can give a better argument.

Regards,

Peter.

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Think of it more as a packaging arrangemet. The engine and gearbox are only two parts to the puzzle. You also need to position the rest of the mechanical items around the ar for best weight distribution. Fuel Tanks for example again best kept low and between the front and back wheels. It is all about ditributing the parts around the car as low as possible to create a very low roll centre and still maintain the optimum distribution usual most cars aim as close to the above mentioned 50/50 but often have a small bias over the rear driven wheels.

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Honda's NSX achieved very satisfactory packaging with a transverse layout by placing the engine and gearbox side-by-side as this illustration shows. Engine on the right and gearbox on the left. This can generally only be done with a fairly short engine - hence the V6 as opposed to V8.

inomoto_nsx.jpg

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Another reason for the transverse engine/gearbox setup is because that's what readily available these days. There's a proliferation of excellent engine/gearbox packages that can be transplanted from so many front wheel drive cars. Look at the earlier Nobles. They do exceptionly well with a high powered V6 set transversely. It succeeds because that engine is one of the lightest V6's available. Nonetheless his later car has reverted back to the traditional longitudinal location for even higher roadholding capabilities.

One problem with the rear transverse setup is too much weight being over the rear axle. That 50/50 ideal starts heading towards 40/60. Good for traction in the dry but can be problematic in the wet, much like 911's.

There are very few readily available gearboxes left that suit a longitudinal layout. Probably only Porsche, Audi and Subaru with the last two needing their AWD output shafts being changed if in a rear drive only application.

DanR

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.... and here's the transmission (auto) used by General Motors in its high powered front-wheel-drive cars using the Northstar V8 engine. Typically Cadillacs and Buicks. Whilst this setup could be transferred directly to the back of a mid-engined car the character of the engine/transmission is not ideal. Shows it could be done though!

07204T8020MH120LoR.jpg

You can guess where the V8 engine goes...

Edited by Lowtus
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Or stick one of these in...SydneyMotorShow2007043.jpg

It's the new 3.6 Subaru boxer six cylinder. Not only a longitudinal setup but has a low engine mass for a better centre of gravity.

DanR

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Another reason for the transverse engine/gearbox setup is because that's what readily available these days. There's a proliferation of excellent engine/gearbox packages that can be transplanted from so many front wheel drive cars. Look at the earlier Nobles. They do exceptionly well with a high powered V6 set transversely. It succeeds because that engine is one of the lightest V6's available. Nonetheless his later car has reverted back to the traditional longitudinal location for even higher roadholding capabilities.

One problem with the rear transverse setup is too much weight being over the rear axle. That 50/50 ideal starts heading towards 40/60. Good for traction in the dry but can be problematic in the wet, much like 911's.

There are very few readily available gearboxes left that suit a longitudinal layout. Probably only Porsche, Audi and Subaru with the last two needing their AWD output shafts being changed if in a rear drive only application.

Another problem with using a FWD gearbox is that due to the limits of power that can be put through the front wheels, the boxes aren't strong enough to handle serious torque. Noble is a case in point - for the M12 they couldn't increase the power from the engine or it would trash the Mondeo box. Or indeed our favourite, the Renault UN1! This also applies to a lesser degree with AWD boxes it you put all the torque through one shaft.

It is possible to use a rear engined Porsche box. It can handle the torque but you have to turn the box upside down for a mid engined car so the wheels drive forwards which makes mating it to the driveshafts and engine more difficult, raises the cog of the box and causes lubrication issues.

So if you want a serious power mid-engined RWD car you really need a box designed for the application. You won't find any mass produced factory boxes (imagine the cost of buying one from Ferrari) so the only cost effective solution is one from the likes of ZF or Quaife.

Unless you want a compact engine/box combination for packaging reasons, longtitudinal is the way to go since you want the engine (which is by far the heaviest component) as close as possible to the middle of the car. It helps obtain a 50/50 f-r ratio but more importantly a low polar moment of inertia. Dan describes it perfectly:

'There's also the advantage of a lower "polar moment of inertia" or how quickly a car can change direction. Think of how much easier it is to twist a kilo weight held in your hand compared to twisting two 500gram weights on the end of a bar held in your hand.'

You can easily achieve 50/50 f-r with a FE RWD car (e.g. BMWs). You can even mount the engine behind the front wheels (technically mid-engined) with the gearbox ahead of the rear wheels (e.g. Ferrari 599) but this still results in a higher polar moment than a true mid-engined design.

Look at a Zonda or Koenigsegg for example, the occupants are way ahead of the mid point of the wheelbase so the engine can be bang in the middle.

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Neal, as you know I am relatively new to the forum, but have read enough of your posts to know that your information/advice can pretty much be "taken to the bank". You have assisted me on more than one occassion, for which I am truely grateful. So forgive me for commenting on one negative aspect of "low polar moment of inertia"---a term I have been familiar with for 34 years of Europa ownership. While my 4 pot is currently stored, I can still vividly recall "swaping ends" in the wet a number of times. There was virually no warning. Granted, tire ("tyre" for the Queen's subjects) technology was not at today's level, but my recollection was that my '74 Europa laid claim to being the 3rd best cornering car in the known universe (behind a Ferrari and one other Lotus I believe) for the era in question. Has today's mid engine design found a cure for a wet track? Short of installing a "stability control" module (which would probably defeat the whole concept of "racing"), what advances have been made?

Keep the "sunroof side" up!

John

Being second is to be the first of the ones who lose.

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Neal, as you know I am relatively new to the forum, but have read enough of your posts to know that your information/advice can pretty much be "taken to the bank". You have assisted me on more than one occassion, for which I am truely grateful. So forgive me for commenting on one negative aspect of "low polar moment of inertia"---a term I have been familiar with for 34 years of Europa ownership. While my 4 pot is currently stored, I can still vividly recall "swaping ends" in the wet a number of times. There was virually no warning. Granted, tire ("tyre" for the Queen's subjects) technology was not at today's level, but my recollection was that my '74 Europa laid claim to being the 3rd best cornering car in the known universe (behind a Ferrari and one other Lotus I believe) for the era in question. Has today's mid engine design found a cure for a wet track? Short of installing a "stability control" module (which would probably defeat the whole concept of "racing"), what advances have been made?

Keep the "sunroof side" up!

John

Yes, you're absolutely right. I was coming from the perspective of how you can design a car to change direction as easily and quickly as possible to maximise the cornering performance. Whether such an extreme is desirable depends very much on the circumstances under which it is being driven. As you say, with a low polar moment once the back end starts to let go it will do so very quickly, and much more so in the wet. Taking it to the other extreme drifters look for cars with a high polar moment (front engine, RWD) which makes the car slower to respond, so they can hold a drift with minimal steering input and transition from drifting in one direction to the other smoothly.

In terms of advances, it has to go hand in hand with a modern traction control (as opposed to a traditional TC which simply prevented you from exploring even close to the limits of a cars handling). You can take a car with fundamentally excellent handling ability (there's no point starting off with a bad car) and dynamically dial in just how docile or twitchy you want it to be depending on any number of factors (road conditions, driver's preference, etc.), something that cannot be done with a static setup. In fact if you look at the latest fighter jets, they're designed to be aerodyamically unstable to improve the handling characterics while the electronics keep it in the air.

For racing though, I completetly agree that TC is a bad thing. But its banning from F1 hasn't made the manufactures go back on their designs to make the cars easier to drive. Performance is still paramount so it's shifted the balance onto the drivers, allowing them to demonstrate their true ability. I would image a moderm F1 car is a nightmare to drive now, evident by the number of top-tier drivers going off this season, but then that's the expectation of them from being at the top of their sport.

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Thanks for the reply, Neal. Based on your additional input (and my past "track record" with the Europa), I have decided to "pull" my application for next season's F1 competition. I was having difficulty finding a sponser anyway. :devil:

Regards,

John

Being second is to be the first of the ones who lose.

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