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Discussion Starter #1 (Edited)
Ian Kuah drives the U.S. Elise at Hethel and adds some
information about the new car in the March 2004 issue of Sports
Car International.

<http://www.amazon.com/exec/obidos/tg/detail/-/B00009MQ7U/102-2673417-4480141?v=glance>

Significantly it appears he was able to ask some of the Lotus
engineers about the weight budget for the revised car. It seems
that the Toyota 2ZZ-GE engine adds 64 pounds over the Rover K.
Toyota's 6-speed C64 transmission, lifted straight from their
Celica adds 13 pounds over the Rover's. Air
conditioning adds 22 pounds and twin oil coolers adds 29 pounds.
No doubt quite a bit of the weights for the added cooling and air
conditioning come from their plumbing. A few additional
modifications result is a 154 pound increase over "the weight of
a Euro-spec 111S." Here's a summary:

1. 2ZZ-GE Engine: 64 pounds
2. C64 Transmission: 13 pounds
3. Air Conditioning: 22 pounds
4. Twin Oil coolers: 29 pounds
5. Other modifications: 26 pounds

Front to rear weight distribution remains largely unchanged since
added coolers up front balance out the drivetrain increases in
back.

Fuel tank is 10.5 (U.S.) Gallons and fuel economy is 36 (U.S.)
Miles per Gallon. European LEV1 emissions certifications were
"easily breezed through" and LEV2 certification is underway.

Kuah notes that the Toyota engine and transmission are both
more effective in the significantly lighter Elise than the
Celica from which it came. Due to the much lower mass, the
torque is more useful and tractable. He did not mention that
part of Lotus' ECU re-tuning was to increase torque. Gearbox
feel is "slick," and:
"the stubby lever can be moved swiftly and surely
across the gate, totally in keeping with the light,
fluid and tactile Elise experience that we have come
to know and love -- the Toyota 6-speed is a good fit"
Andrew Barron also noted in Lotus ReMarque, the U.S. club
newsletter, that the engine and gearbox work better in the Elise
than the Celica, and I believe he rightly attributed some of that
to the much lower overall weight of Elise.

Kuah notes very good passenger cell protection from the chassis
and impact-absorbing sections up front. He mentions that Lotus
is now cleared to reveal that they designed the crash structure
for the Aston Martin Vanquish. The only safety changes for the
U.S. Elise are the addition of small airbags, which in turn
prompted a redesign of the dashboard, which is now precision
injection-molded.


Instrument pack is new, and includes tire pressure warning lights
and a "race style engine rpm upshift" light.
"A new center console carries the controls for the
lightweight air-conditioning system that came onstream
last year when the Euro Elise 111S was launched. A/C
comes standard on the U.S. car, as do power windows."
The chassis was recalibrated for U.S. driving conditions, notably
big bumps and huge potholes. A new rear subframe has a forward
attachment point at the bulkhead, behind the fuel tank. Spring
and damper rates are up slightly in to better control the
slightly increased mass, and new dampers have 10 mm more travel.

In order to handle noise from expansion joints and other road
irregularity impacts on the suspension, Lotus ride and handling
development engineer Simon Newton told Kuah that more complaint
lower, forward A-arm bushings were specified in order to:
"cope with 'wheel recession,' which is how Lotus
describes the phenomenon of the wheel and suspension
being pushed backwards when they encounter a short,
sharp obstacle like and expansion joint."
(Sounds quite a bit like the rationale for the "raft" subframe under the front
of the M100 Elan.) (Expansion joints are lateral gaps between
longitudinal concrete sections of highway which the rest of the
world may not have as prominently as do some U.S. roads.)

In addition the brackets that contain these slightly softened
bushings "are wider and other minor changes have been made to
optimize the chassis for U.S. road conditions." It's not clear
whether European versions of the Toyota-engined Elise will get
similar suspension modifications. (Mike Caucer or anyone who
else gets a look at the European versions may want to compare
bushing brackets...)

Tires are the same Elise-specific Yokohama 175/55ZR16 and
225/45ZR17 sizes used in the European 111S.

New power-boosted ABS brakes are fitted which underwent
extensive, careful development by Lotus. Lotus used the brakes
on the Porsche 911 as their benchmark in developing the new Elise
ABS brakes. Simon Newton described the new braking system to
Kuah thusly:
"We worked very hard on this system. A few years ago,
we were against ABS, as it interfered with the purity
of the car on the track. But things have moved on and
current technology allows us to develop a system that
suits this car.

Our major criticism of most ABS systems is the way
they perform on a circuit [racing course]. We
originally wanted an on/off switch, but this was
not possible because of legal liability in case of
an accident. The alternative was to develop a
better system ourselves, and our benchmark was the
Porsche 911."
Kuah describes the resulting braking system:
"Basically Lotus has designed an ABS system that
does not trigger too quickly, which makes it
especially suited to track use. The system
actually allows a bit of lock before triggering
and keeps the pedal from going hard while the
ABS is pulsing in order to preserve brake feel.
Ultimately this allows you to go deeper into
corners. As with the engine and other changes
that have been made to the Elise, the added
weight and complexity was justified."
After driving the prototype with U.S. spec engine and suspension
around the Hethel test track Kuah reports:
"Poise into and through fast bends and the
delicacy of steering feel are unaffected by
the changes, but the extra thrust out of
bends can be readily felt and straight-line
speed is most impressive. At last the chassis
has the engine it was always crying out for."
I note that Kuah is a very prolific reviewer, writer and
photographer. He has probably driven most of the major
production sporty cars during Europe's recent decades, and quite
a few custom specials. He gave rave reviews to the Motorsport
Elise he drove a year or two ago, so if he feels that the
Toyota-engined Elise is a good version of the car, he's probably
right...

Cheers,

Jeff C.
--
Jeff Chan
mailto:[email protected]
http://www.jeffchan.com/
 

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Thanks Jeff!
 

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Discussion Starter #5
No problem guys! This info was too good not to share. Sounds like the car is a winner!
 

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Discussion Starter #7 (Edited)
Yeah the Mercedes SLR is great if you like 3700 pound carbon fiber cars. :confused: :rolleyes: I'm sure their weight budget would be excruciatingly painful to read.... :mad: :( :cool: :D :p :eek:
 

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Great article.

I didn't quite understand the part about the new rear subframe... can anyone explain the nature of the difference? I figure some changes are due to the different engine, but it sounds like there may be other changes.

Sounds like the ABS system is going to be awesome.

I just hope those bushings aren't too soft. I want to feel the road surface like you do with the Euro car. That includes expansion joints! I don't want the road feel of the car to be muted beyond the point where you can "tell how many legs it had" when you run over an insect. ;)
 

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straw,
here's a pic of the rear subframe for the S2. I'm told they had to beef it up because of higher power (also weight as the Yota/gearbox engine is something like 50 pounds heavier than the rover unit)

Chris
 

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Discussion Starter #12 (Edited)
strawtarget said:
Great article.

I didn't quite understand the part about the new rear subframe... can anyone explain the nature of the difference? I figure some changes are due to the different engine, but it sounds like there may be other changes.

Sounds like the ABS system is going to be awesome.

I just hope those bushings aren't too soft. I want to feel the road surface like you do with the Euro car. That includes expansion joints! I don't want the road feel of the car to be muted beyond the point where you can "tell how many legs it had" when you run over an insect. ;)
Hi Straw,
Regarding the new subframe I suspect you're right: a new subframe was needed to cradle the new engine, and they took the opportunity to revise how it attaches to the chassis.

I agree it sounds like the ABS system is well engineered towards performance. Using the 911 as a benchmark says Lotus is serious about performance and feel.

Regarding the bushings, I think you may be misinterpreting the intentions. If the tires are upset by large disruptions they won't be in good, stable contact with the road. If the tires don't have a consistent interface with the road then what you feel will be scrambled. It's by building a little compliance into just one part of the suspension that the tires will be kept in better contact with the road and you will feel the important stuff, i.e. the real, usable surface, not the large gaps and large disruptions. What you'll feel is the tires working with better contact with the part of the road surface that actually provides grip. In other words you'll be able to count the insect's legs through the steering wheel, even if the insect is just beyond a pothole. Before you would have felt the chassis, suspension and tire flailing madly to deal with the pothole. That's a benefit. :)

This should be especially noticeable during a bump in a turn, because as I remember Lotus Engineer Clive Roberts explaining about the M100 subframe raft, the longitudinal compliance allows the suspension to be set to smaller castor settings, which means the driver is presented a finer feel of the tire loading:

Absolutely right - the Something Else is pneumatic trail, a property of the
tyre.

The effort you feel at the wheel comes from two sources (if we disregard
friction in the rack and column - well worth checking on Triumph-based racks)
-

1. The moment about the kingpin axis, tending to return the tyre to
straight-ahead, caused by the castor angle - don't need much more detail,
except that it's virtually constant, and gets larger as the castor angle
increases. The important point is that it doesn't vary as cornering effort
changes - it's just there, a force you have to work to overcome. It only
needs to be there, in some small amount, to ensure straight running.

2. The torque caused by the cornering force acting through the contact patch
- this is the interesting item, because as cornering effort rises so the
contact patch changes shape - thus the point at which the cornering force
acts on the steering system (pneumatic trail) changes position. This means
that the tyre is actually sending you signals to tell you how much work it's
doing on your behalf - as it approaches the limit, the torque felt through
the steering gets smaller - in other words, the steering gets light. This is
a very good signal, AS LONG AS YOU CAN RECEIVE IT. If you have a large castor
angle, you won't - it will be masked by the unnecessary and unhelpful grunt
factor required to overcome the castor.

There is really no need for large castor angles on a well designed suspension
- there is no inherent merit in having 6 degrees instead of 3 - it only needs
to be just positive at all times. Old wishbone systems will tend to lose
castor under braking (as the brakes try to rotate the upright), but more
recent designs will have ways to compensate, allowing low static castor
settings. (an extreme case being the M100, whose raft allowed as little as 2
degrees static castor, and kept it constant under load).

cheers

Clive
I suspect the slight added longitudinal compliance created by the new front bushing arrangement is meant to control castor change after a large bump or pothole, thus preserving the feel of pneumatic trail in the new Elise which Clive mentions in general terms. That would be an excelent question for Lotus regarding the new model.

I didn't mention it originally, but Kuah's article also mentioned that the Elise bushings are already 50-60% stiffer than most other cars, accoring to that same development engineer. I seriously doubt that Lotus has turned the Elise into a Cadillac Seville wannabe. Lotus undertstands how important steering feel is and have found a way to preserve it even with our less than perfect road paving.
 

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Discussion Starter #13
zvezdah1 said:
straw,
here's a pic of the rear subframe for the S2. I'm told they had to beef it up because of higher power (also weight as the Yota/gearbox engine is something like 50 pounds heavier than the rover unit)

Chris
Thanks for the pic Chris. A very logical question then would be: where did the old (Rover) subframe attach? How is the new one different? The one shown in the diagram seems the best for a solid, triangulated connection to the frame and roll structure.... Can't really imagine doing it any other way. :)
 

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I suppose titanium as a replacement to the steel would be out if the question :rolleyes:
It makes me feel good about the ABS, I track my boxster and I absolutely LOVE the ABS ! My only problem is that with later and later braking, eventually I run out of capabilty to actually slow in the space I allow :p Locking up is never a concern and feel is great. The brakes use ALL of the the traction available by the 245 Hoosiers I use.

I want mine now!! :eek:
 
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