carrera 4 vs 4S - why quicker straight line?

[944doc]

just curious, but looking at performance specs for the 993 carrera 4 versus the 4S they have identical top speed but the 4S is a bit quicker 0-60. I understood that the 4S was essentially a turbo bodied car with turbo brakes/suspension etc and a normally aspirated engine. I can see how this might affect handling etc anf real life or track performance but how does it improve straight line dash?

is it that the turbo body is more aerodynamically efficient?

on a similar vein, what is a 2S? is it the same as a 4s but rear wheel drive only?

[GreigM]

944doc said:

just curious, but looking at performance specs for the 993 carrera 4 versus the 4S they have identical top speed but the 4S is a bit quicker 0-60. I understood that the 4S was essentially a turbo bodied car with turbo brakes/suspension etc and a normally aspirated engine. I can see how this might affect handling etc anf real life or track performance but how does it improve straight line dash? is it that the turbo body is more aerodynamically efficient? on a similar vein, what is a 2S? is it the same as a 4s but rear wheel drive only?

Is it slightly fatter tyres giving more grip and getting it off the line quicker?

Top speed is probably more related to aerodynamic drag - as flemke said in his F1 thread.

2S - yes, I believe this is a turbo bodied C2

[verysideways]

4S got turbo body, bumpers, brakes, lookalike wheels, and suspension.
2S just got the body/bumpers. Most 2S's also got the lookalike wheels.

(* i say lookalike, because the turbo wheels had hollow spokes, the 4S (and 2S in some cases) got the solid spoke wheels that looked the same as the turbo wheels).

Chances are, 4S is quicker off the line due to increased traction (more rubber on the road from those big tyres).

Just my £0.02

VS

[nel]

Funny - I thought I'd heard that the NA widebody versions had a slower top speed because of increased drag for the same engine power?

[dazren]

nel said:

Funny - I thought I'd heard that the NA widebody versions had a slower top speed because of increased drag for the same engine power?

I believe this to be the case. Same reason some ultra tuners give an option of going the narrowbody route and thus a higher top speed, assuming gearing permits.

DAZ

[grant3]

Probably because you are comparing figures for a pre-varioram 993C4 with a varioram 993C4S ????

[warmfuzzies]

Hmm, not sure about the complete differences, but top speed is relative to BHP, frontal area and Cd.


K.

[turbobloke]

warmfuzzies said:

Hmm, not sure about the complete differences, but top speed is relative to BHP, frontal area and Cd. K.

Assuming identical gearing o'course...

[warmfuzzies]

hmm,

Never assume......

Gearing will make a difference for take offs, but....as wind resistance plays a rather large part in top speed, the car will run out of power to drive it forward, before the gearing tops out, and hence makes a diference to the top speed.
It will make a slight difference, but not one of any consequence.
www.miata.net/sport/Physics/06-Speed.html


IS one example showing why its as I quoted.....

K1p.

>> Edited by warmfuzzies on Friday 22 October 22:34

[ian_dorrian]

Just got out my Carrera 4S 1996 owners manual since I have need to change a rear brake light bulb and it quotes figures for all the 993 range: top speed / 0-100km/h /standing km

Carrera - 171mph / 5.4secs / 24.6 secs
Carrera 4 - 171mph / 5.3secs / 24.8secs
Carerra 4S - 168mph / 5.3secs / 25secs
Carerra Tip S - 168mph / 6.4 secs / 25.4secs
Turbo - 180mph / 4.5secs / 23secs

So Porsche reckon the NA varios have faster 0-100 in 4wd guise to the tune of 01.secs but the turbo body definitely messes up top speed and based on the clever maths we saw earlier, it looks like its going to take one almighty rechip to get the those 2mph back...

Ian D

[turbobloke]

ian_dorrian said:

the clever maths

quite right too but the physics has an error of between 7% and 8% because most racing is carried out at nearer 20 deg C than 0 deg C

[Pickled Piper]

Also, don't forget that wider tyres have a higher rolling resistance and can easily account for a 2 to 3mph detriment to top speed.

[james_j]

verysideways said:

4S got turbo body, bumpers, brakes, lookalike wheels, and suspension. 2S just got the body/bumpers. Most 2S's also got the lookalike wheels. (* i say lookalike, because the turbo wheels had hollow spokes, the 4S (and 2S in some cases) got the solid spoke wheels that looked the same as the turbo wheels). Chances are, 4S is quicker off the line due to increased traction (more rubber on the road from those big tyres). Just my £0.02 VS

When the 2S was new, if the 18" wheels were specified, they would be hollow spoke turbo wheels. If the 4S owner specified 18" wheels in the same circumstances, they would get solid "look alike" wheels, not turbo wheels.