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Hybrid Lotus 49 Esprit V8 Setup For Enna Pergusa


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#1 John Woods

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Posted Mar 20 2015 - 05:51 PM

Just Guessing...

Awhile back began thinking the Lotus Esprit Twin Turbo V8 is maybe the closest production model Lotus has made that sort of is configured like the 49. The Esprit weighs 2,866 pounds and depending on tune may have well over its stock 350hp. The original pre-production racing engine that was said to be around 500hp was only de-tuned for production.

Zero to 100 in less than 10 seconds. To 60mph in  4.3. Top speed well beyond prudence. Not bad for a 1996 supercar.

Road & Track certified it being one of the best handling cars money could buy, matching it up against other world class g-force contenders: the Viper, 911 AWD, Ferrari, an NSX, and a C5 Corvette, (all much newer cars).

That article, (link found on a Corvette forum), prompted an interest in how setting up a Lotus V8 might be similar to a Lotus 49 at least in some general respects.

This led to the discovery of reference to a late issue Lotus Service Bulletin on suspension upgrades that included spring rates for the standard version and the 350 Sport, (only fifty 350s were made out of over 10,000 V8s). They were tweaked for performance and only sold in Europe.

Standard street version F/R spring rates: 250/275.
350 Sport: 350/330.

!

JMHO, it seemed to me a curious thing the performance version would have softer rear springs. It goes against all this 40/60 balance stuff about Grand Prix Legends setups.

The Lotus V8 has nearly 50/50 balance built-in.The ratio of F/R spring rate for the street version is 47.6/52.4 by percent, while the ratio for the 350 Sport is 51.4/48.6. Ride height for both is the same front and rear.

However, for this and all my GPL setups, rather than computing the ratio of gross weight to spring rate and correlate to the 49, spring rates were determined by relying on a non-GPL chart posted here awhile back that indicated an appropriate front spring rate by gross weight for a typical race car. For a hotlap car at 1,350 pounds, a spring rate of 125 pounds is "in the range."

Therefore, 125/51.4 x 48.6 = Rear Spring Rate of 118 pounds when front is 125.

Searching through Lotus V8 forums for suspension tuning tips found various suggestions and specs. So far the following has seemed most credible and respected without too much argument among the Lotus forum gurus.
In my view these changes make a comfortable and capable 49. Not pretending its fast, faster, fastest...only that it is pleasant to drive and behaves well enough.

Front camber: -.5 (minus point five)
Rear camber: -1.0 (minus point one)
Front toe-out: .15 (point one five)
Rear toe-in: .13 (point one three)

Front bar: 180 (Current Preference)
Rear bar: 95 (Same)

Diff: 45/85/2 (Based on Kaemmer/Hine Interview reference)
Steering ratio: 9:1

Ride Height Front and Rear: 2.5in.

Enna Pergusa Setup Asymmetries:

Tires Front: 21L 20R
Tires Rear: 19L 18R

Bump Stops Front: 1.7inL 1.65inR
Bump Stops Rear: 1.75inL 1.7inR

This setup is for me about the easiest ever flat out in mid-corner.

Probably needs something tho...probably slow.
:)

Edited by John Woods, Mar 21 2015 - 10:12 AM.


#2 Nicolas

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Posted Mar 21 2015 - 01:53 AM

Quote

In 2005, nine years later, Road & Track certified it [Lotus Esprit Twin Turbo V8 1996] being one of the best handling cars money could buy, matching it up against other world class g-force contenders: the Viper, 911 AWD, Ferrari, an NSX, and a C5 Corvette, (all much newer cars), in a competition in which it finished fourth.
The "much newer cars" claim needs some detail. The Esprit model has been around since 1976, but the TTV8 version since 1996. The NSX has been around since 1990 so is 6 years older than the Esprit V8, but 14 years younger than the Esprit model itself. Idem dito for the Viper: in production since 1992, 4 years before the Esprit V8 but 16 years after the Esprit model. Corvette C5 1997 so newer in either sense. 911 AWD: I assume that implies the 2005 model, indeed quite a bit more recent than 1996. "Ferrari" without further detail is a likely red car. :) Anyway, barring high prices and terrible timing belt lifespan on the non V8 models, and slightly unpleasing aestethics on the first generations, I love the Esprit and I'd like to have one. From a sophistication point of view, the NSX was 15 years ahead of its time in 1990. In the end of the day, I don't want sophistication, I just want an unhealthy amount of HP and torque on a tail happy but controllable chassis. :) Hence GPL! :D Interesting to see what happens if you apply Esprit setups to the 49. I'll give a setup like that a try. I like an easy handling 67 from time to time.

Edited by Nicolas, Mar 21 2015 - 01:54 AM.


#3 John Woods

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Posted Mar 21 2015 - 07:07 AM

Thanks Nicolas,

Its a hybrid setup, made up of my GPL Lotus base preferences with Esprit suggested tweaks and my own interpretations. If testing on your own, maybe for best result start with your own favorite setup and apply changes to that.

And as usual made some errors...should have read with more focus on words.
It had been too long, (weeks) since reading the article.
It was published in 1999, not 2005.
Had to search around to find it again, this time on an NSX site.

NSX Prime

The model years were not provided, but these are the cars: Acura NSX Zanardi Edition, Chevrolet Corvette C5 Hardtop, Dodge Viper GTS-R, Ferrari F355 Spider, Lotus Esprit V8 and Porsche 911 Carrera 4

Road & Track authors made the point the Lotus suspension is basically unchanged since 1975. So as Nicolas noted not so much model year as engineering design year when referring to the Esprit's age.

The Esprit finished last, but did best the Vette on the skidpad.

Edited by John Woods, Mar 21 2015 - 07:40 AM.


#4 Nicolas

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Posted Mar 21 2015 - 07:45 AM

Corvettes and skidding are not best friends, so I can imagine that. In 99 the Viper was the most advanced chassis of "common" American powercars. A Mustang is a horsecart in comparison. A fun horsecart, but a cart nonetheless. :) Very good effort from Lotus to get these results with what is indeed basically a 1975 design. Then again, look at what Porsche did starting from a basic seventies 924 up to a 911 beating 968 still using essentially the same basics.

#5 John Woods

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Posted Mar 24 2015 - 12:12 PM

Few days ago found a couple of Lotus Talk forum posts about setting shocks and springs. Different shock manufacturers use different ways of noting the settings for their shocks.

There is some variety of opinion about how to set up shocks. But one post went into more detail and it offers ratings in pounds instead of clicks or numbers: (think this was for Spax shocks)

Front  475/320  (60/40 by percent)
Rear   320/265  (54/46)
Springs   425/300  (59/41)

Here again the rear is softer than the front in all respects. However, guessing its the ratios that are significant more than the pounds. Note also front rebound and rear bump are the same.

So still have to wonder, are these IRL Lotus V8 guys wrong about less rebound than bump and being softer on the rear?

Edited by John Woods, Mar 25 2015 - 06:46 PM.





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