Jump to content


- - - - -

Asymmetric Cars - Fundamental Bug In Nr2003


  • Please log in to reply
3 replies to this topic

#1 BrunoB

BrunoB

    Denny Hulme

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 155 posts
  • Gender:Male
  • Location:Denmark, Jutland
  • Interests:GTP, GTP and GTP
  • Sim interest:GPL

Posted Apr 12 2012 - 04:14 AM

Asymmetric cars - fundamental bug in NR2003 and all its mods.

To the best of my knowledge no NR2003 setup wizard have acknowledged (or discovered) that there is a hardcoded bug burried deep inside the NR2003 game engine.
The cars are fundamentally asymmetric in the horizontal plane!

What does that mean?
It means that if you create a 100% symmetric setup then the cars behaviour is different if you want it to turn left or right!
Because the grip values is different in leftward corners than in rightwards!

The reason is surely because the orig NR2003 was created to be driven on ovals.
And on ovals you only turn to the left.

But if we compare this to the real world then no chassis of real Nascars (or Indycars for that matter) are made fundamentally asymmetric.
Its only the special asymmetric oval setups for these cars which makes their behaviour asymmetric.

OK I can hear you say that this is no big deal for this great sim and all its mods.
Not much difference if the asymmetry is in the car itself or introduced in the setups (as in real cars).
But the problem explodes when we are taking our virtual cars away from ovals and place them on a road track with rightward corners.
Because then we have to create an assymetric setup to try to make the car behaving (kind of) symmetric!

I admit this is not really a problem for a rookie driver or a more casual driver because they probably cannot feel the difference between the "normal" car control difficulties and this general behaviour issue.
But why have no of the more experienced drivers discovered and targeted this issue?
Probably because they have driving skills which are able to compensate for the problem.
But at least in my mind there is no doubt that even aliens would benefit of implementing changes caused by this discovery.

You can download the full article as a Word document here:
http://dl.dropbox.co...g in NR2003.doc

BrunoB Racelab

Attached Files



#2 jgf

jgf

    Denny Hulme

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 675 posts
  • Gender:Male
  • Location:Columbus, OH
  • Sim interest:GPL and P&G

Posted Apr 12 2012 - 08:58 AM

View PostBrunoB, on Apr 12 2012 - 04:14 AM, said:

...
But if we compare this to the real world then no chassis of real Nascars (or Indycars for that matter) are made fundamentally asymmetric.
Its only the special asymmetric oval setups for these cars which makes their behaviour asymmetric.

...
I don't know when Indycar abandoned the visibly asymmetric suspensions, but NASCARE definitely still uses them.  Larger, more affluent, teams build specific cars for short tracks, speedways, superspeedways, etc.;  the chassis are certainly similar but definitely neither identical nor symmetric.

From http://www.autocentr...hassis-For-0001

"While tight regulation applies to most parts of the vehicle chassis, the suspension system represents a relatively unrestricted zone that leaves plenty of opportunity to engineer inherently faster race cars. After establishing subtle compromises between vehicle aerodynamics and handling performance, detailed suspension design and tuning begins. Chris Hussey explains that consistent tire patch contact with the track can be maintained under all racing circumstances, by adapting suspension characteristics to align the driving behavior of the car to the size and banking of the oval track. "Besides focusing on designing for lighter vehicle weight, we modify the suspension design, all within the design boundaries imposed by NASCAR. We tune caster and camber in the asymmetric suspension along with toe, and design the right amount of toe out that can be gained on the inside tire in a turn. Following our strategy to bringing more engineering in-house, we take full control over chassis/suspension engineering and safeguard our technical expertise."

If you perceive a difference in grip for left hand vs right hand turns in the sim with a neutral setup I would first suspect a software issue.  Also consider a psychological/physiological issue;  being right handed, I find it easier to make left turns than right ones ...in real life and in sims.  A quick test in a sim is to create a completely symmetric, neutral setup and do a few medium speed laps at a speedway;  just warm up the tires, don't try for hotlaps, and note the tire temps.  Start over and do equal laps in the opposite direction, again noting tire temps.  If the chassis physics are modeled symmetrically, and your driving is consistent, tire temps will be congruent, though reversed, for both runs.

I do feel there are physics issues with the GTP mod since these cars should be significantly faster on a superspeedway than a Cup car, yet they are invariably slower.

#3 BrunoB

BrunoB

    Denny Hulme

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 155 posts
  • Gender:Male
  • Location:Denmark, Jutland
  • Interests:GTP, GTP and GTP
  • Sim interest:GPL

Posted Apr 12 2012 - 10:51 AM

First my postulate that real oval cars are not created/build asymmetric.
I think its a matter of choosing the words because as I clearly points out in the article the setups for real oval cars ARE (ofcourse) asymmetric.
But maybe I have not taken the thought fully to its end because as I understand your quotation the asymmetry is more drastic than giving the camber, caster, pressure and springs asymmetric values (as was my thought) but also changing/redesigning some swingarms and stuff. Thats OK with me. It just shows that they are taking the setup settings further asymmetric than I thought:-)

But then to this other one where I to the contrary of the above think that you havent completely got my point (hard but nice unfair postulate :-):-)

View Postjgf, on Apr 12 2012 - 08:58 AM, said:

If you perceive a difference in grip for left hand vs right hand turns in the sim with a neutral setup I would first suspect a software issue.
Because the only reason I use so much time "translating" the Papyrus help text (and calling it from the mouth of the horse itself:-) is solely because this is the closest of a proof you can get!
Because if the NR2003 cars were not fundamentally asymmetric there would not be any asymetric difference in gripchange from low to high speed corners.
Exactly how it is in the rear!

This fundamental asymmetry has absolutely nothing to do with "a software issue" or a "psychological/physiological issue" (like kinda placebo effect).
Or formulated rhetorical: why do you think Papyrus need to make this strange asymmetric distinction between how the front grip changes and the rear grip does?

Please dont take this as Im patronizing you. Because Im pretty satisfied that at least you give some feedback/questions my findings.

#4 jgf

jgf

    Denny Hulme

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 675 posts
  • Gender:Male
  • Location:Columbus, OH
  • Sim interest:GPL and P&G

Posted Mar 14 2014 - 08:27 PM

Dredging up an old topic here but I've been digging through my old N2003 stuff recently (it was too cold to go outside and enjoy winter this year).  In the track.ini are settings for "track type" and "chassis type" which seem to reference hard-coded "suspension" (handling) parameters;  all the oval settings apparently replicate asymmetric suspensions (stagger?  this was a setup option in early versions of Nascar Racing), the "road course" option probably being the only one capable of true symmetric setups.

I haven't experimented with these much, beyond removing restrictor plates, and there is some controversy over what exactly these settings control.  The following are from my notes (sources unknown ...long forgotten):
----------------------
"You can try any chassis type at any track by putting in one of the numbers below.

1 = superspeedway with restrictor plate
2 = speedway
3 = short track
4 = road course
5 = superspeedway without restrictor plate"
-------------------------
"0 = short track
1 = mile oval
2 = medium oval (1-2 mile)
3 = long oval (think this is the 2 mile)
4 = super speedway
5 = road course

Chassis types:
0 = ?
1 = super speedway
2 = speedway
3 = short track
4 = road course

From testing at Talladega -

Chassis 0 - high drag, huge torque, tires never wear out, top speed around 190.
Chassis 1 - low drag, low HP, fixed rear springs, shocks and spoiler, top speed around 185.
Chassis 2 - medium drag, top speed around 210.
Chassis 3 - medium drag, top speed around 205.
Chassis 4 - medium drag, top speed around 205.
Chassis 5 - minimal drag, doesn't like to turn or stop, top speed around 240."
-------------------------

From those Talladega results I would think Chassis 0 = short track, Chassis 1 = restrictor plate, Chassis 5 = superspeedway with no plate; the others - ???, too little data.

As you can see there is some confusion just between those two quotes, and I've no idea whether the track or chassis parameter, or some arcane combination thereof, tells the sim which physics modifications to apply.  (For example, what if you designate Daytona as a medium oval and select the road course chassis?)

And how much, if any, of this applies to the GTP mod is anyone's guess.  Redline modified the physics so greatly that all this may be entirely irrelevant.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

Sim Racing Links