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[AC] Porsche 550 Spyder


Alessandro Pollini

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File Name: Porsche 550 Spyder

File Submitter: Alessandro Pollini

File Submitted: 25 Jul 2015

File Category: Cover Wheelers Mods



Author : Ensyuya

 

Release notes

 

The two physics set.
The base 1955 Porsche 550/1500 RS (110 BHp, Dunlop R3 natural rubber tires - overheats at 80C, huge slip angle possible)
And the "s1" version being a late 50's hillclimb prepared version with RSK engine part upgrade, increased displacement (1650-1700cc) and new Dunlop R5 tires (synthetic rubber) slightly wider rubber at the rear. Such a car finished 2nd at the 1960 Pikes Peak with Roger Ward at the wheel. We used dyno curves of a 547 1755cc engine.

 

Porsche 550 physics background
The 550 was basically the first ever mid-engine road car, so its design is not perfect. Suspension was all based on VW parts. Front was the double torsion bars (a Porsche patent) and rear was a basic swing axle - both causing horrible camber change under cornering. On top of that, the frame was weak and twisted a lot. It has drum brakes and 50's tires less than 100mm (4'') wide.
However, aerodynamics was very sleek. Weight and inertia are extremely low (under 600kg) and the 4-cam 547 engine was way ahead of its time, revving easily up to 7500 rpm. It would be Porsche's race department workhorse for an entire decade.

 

Overall the car has good handling for its time, but it was notoriously oversteering . Many period pictures show 550's in oversteer.
Ken Miles (aka "Spyderman") said: "Steering the 550 was very much a matter of very large steering movement to produce the desired result",
He also mentioned this about the 550 vs 550A (not in the mod currently) “The change in handling is unbelievable. Gone was the excessive oversteer (of the original 550), the RS (550A) was now as forgiving a car as one could possibly wish to meet."

 

 

Credits
Ensyuya (Mitsunari Ishii) : Project lead, 3d Model, textures, animations, shaders, sounds
Patrice Cote : Physics, UI car history
Engine sound sources except high rev sound : Citytea
Beta tester : Phil E, Maseratialfa, Jon Uyan and Hutch from the CMS Historical racing league (cmsracing.com)

 

About sounds
The engine sound is from real type 547 engine that Citytea recorded around 2006 at Salzburgring with his old Boss R-1 digital-recorder. He gave us permission to use with pleasure.

 

Other sound samples are recorded by Ensyuya from real classic VWs or Kunos original ones.

 

Polycounts, file size and distance for optimization are about
LOD A 230000 95mb from 0 meter
LOD B 131000 79mb from 6 meters
LOD C 45000 32mb from 32 meters
LOD D 14000 5mb from 48 meters

 

Damage model function fully works.
550 spyder mod got all functions that should be in this mod. All functions Kunos implemented in AC are working properly.

 

Benchmark of 550/1500 RS Spyder mod
I tried to measure the PC system performance hit of 550/1500 RS Spyder mod, because the development of basic part of this mod has been completed all. I used the official Alfa Romeo GTA for comparison as the benchmark. Generally results are not so bad for this mod. The load of this mod to the system is about 30% heavier than the Alfa Romeo GTA.

 

System specification of my PC
CPU Core i3 Clarkdale @3.5GHz
System memory 8GB
GPU Geforce 560GTX with graphics memory 1GB
====================================================================
Display
Resolution 1280 x 720
Single Screen
Full Screen
Anisotropic Filtering 4x
Anti-Aliasing Samples Off
World detail Max
Shadow Resolution Ultra
====================================================================
Effect
Smoke generation Normal
smoke in mirrors Off
Enable post - processing effects Default
====================================================================
Reflections
Mirror Resolution Normal
HQ Mirror Reflection Off
Reflection Quality Medium
Reflection Rendering Frequency Medium
====================================================================
Quick Race
Single-make grid (Opponents will use the same car as you)
WEATHER Clear
RACE DURATION 2Laps
====================================================================
SPA-FRANCORCHAMPS
Porsche 550/1500 RS Spyder
Opponents total = 10
Warning CPU Occupancy > 99% = once for a moment

 

FPS min = 30
max = 49
average = 40+

 

Alfa Romeo GTA
Opponents total = 14
Warning CPU Occupancy > 99% = once for a moment

 

FPS min = 26
max = 40
average = 30+
====================================================================
Eastern Creek Brabham
Porsche 550/1500 RS Spyder
Opponents total = 9
Warning CPU Occupancy > 99% = none

 

FPS min = 28
max = 58
average = 35+

 

Alfa Romeo GTA
Opponents total = 13
Warning CPU Occupancy > 99% = 3 times

 

FPS min = 22
max = 58
average = 30+-
====================================================================
Silverstone
Porsche 550/1500 RS Spyder
Opponents total = 10
Warning CPU Occupancy > 99% = none

 

FPS min = 31
max = 47
average = 35+

 

Alfa Romeo GTA
Opponents total = 13
Warning CPU Occupancy > 99% = none

 

FPS min = 27
max = 50+
average = 35+-

 



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"Front [suspension] was the double torsion bars (a Porsche patent) and rear was a basic swing axle - both causing horrible camber change under cornering. On top of that, the frame was weak and twisted a lot. It has drum brakes and 50's tires less than 100mm (4'') wide."

 

Actually, there was absolutely no camber change whatsoever in the front suspension (trailing arms); the wheels were always at the same angle as the chassis (as opposed to the desirable camber gain you get with an SLA suspension).  And the 550's tires were on 4.5-inch rims in the early versions and later on 5-inch rims (the tires themselves were about a half-inch wider, so five and 5-1/2 inches).  

 

I only drove a 550 once or twice, and not at racing speeds, but this version feels pretty authentic. I added quite a bit more rear camber.  In the real world, Spyders ran at least two degrees, sometimes more.  If you got the CG under the inboard U-joints, the rear end would squat under lateral acceleration, but one little bump and the rear wheels would want to click heels.

 

Also, in the real Spyders, you couldn't change the front camber (except by shimming--which made the suspension bind--or by bending the torsion tubes, a dangerous, dicey job).  

 

Ken Miles once told me, when I complained, "If you're getting understeer, you're not going fast enough.

 

Nice package, with all the historical material (photos, articles).  And the stereo sound is quite nice.

Edited by Toonces
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