Gran Turismo 5 physics and vehicle dynamics discussion thread

Discussion in 'Tuning General' started by clacksman, Nov 18, 2010.

  1. clacksman

    clacksman Licensed Racer

    I'm interested in picking the brains of the racers finding themselves entertained by GT5. For those unaware, several TPRA drivers of the Prologue era actually push cars around a track in a competitive environment of some sort, from track days in street cars to autocross to race cars in races. I've merely played GT from day one and watched an unhealthy amount of Speedvision and televised racing in general, so I'm really only qualified to comment on how game replays compare to reality.

    We've seen GT5 includes factors like weather, fuel depletion and damage (all of which we'll get to experience for the first time while racing online), and apparently the Prologue physics split of Standard/Professional has now replaced by 'skid recovery force'. We've seen the draft is no longer the overly-long-and-strong of Prologue.

    What I'd like to learn includes how similar the virtual race driving is to real race driving and why (or why not).

  2. Mechs2002

    Mechs2002 Licensed Racer

    Well I've only done a couple autocross events, but I'll put my two cents in. I drive a 2010 Cobalt SS on Federal Motorsports 595 225/40R/18 front and back. On real vs virtual, I think GT5 does a pretty damn good job and coming very close. The only thing missing is the actual G forces and pretty just the feel of the car through the seat of your pants feeling IMHO.
  3. THE_KART96

    THE_KART96 TPRA Staff

    Once I get GT5, I'll let you know how the karts match up.
  4. clacksman

    clacksman Licensed Racer

    Close enough thread topic is close enough.

    I just did the 60-lap Grand Valley 300km in a Celica GT-Four '98. 341hp & 1268kg. On Sports Softs I went 20 laps, Mediums I went 28. That's not the interesting part.

    On lap 15 I realized I had used just barely more than 1/4 tank of fuel. On my first pitstop on lap 20 I took no fuel as I thought I might make it without adding any if I smoothed out my driving a bit more and short-shifted. For my first stint I drove pretty smooth in an effort to extend tire life of the Sports Softs.
    On my second stop on lap 48 I took 10 litres as I was clearly not going to make it on fuel despite running the entire stint upshifting 1000rpm earlier than I had been in stint 1. The game suggested 16 litres at this time, I reduced it to 10.
    On lap 56 I ran out coming onto the frontstraight and pitted, I didn't notice the fuel was red until I had no power. The game suggested 6 litres, I took that much, and made the finish back down to red on fuel.
    So had I taken 16 instead of 10 on lap 48 I likely would have made the finish on fuel without the final unplanned stop.

    Caution: math content ahead
    What was my fuel consumption rate?
    Track is 4.9448 km
    60 laps is 296.688 km
    I went nearly (~500m short) of 56 laps (276.9088 km) on *full+10 L
    It took less than 6L to go 3 laps or 14.8344 km
  5. vkaifh

    vkaifh Licensed Racer

    finally a question in an area of my expertise: math :sHa_clap: Lets hope I make my math teacher proud.

    I believe the question would be with how much gas you started or is that known?

    To calculate the size of the tank I have to make some assumptions, otherwise the equation has to many variables (or is getting too difficult):
    assumption 1: your consumption was the same all the time
    assumption 2: you consumed the whole 6 liter in the last 3 laps.

    6l for 14.8344km => consumption rate is 40.4465 liter / 100km (that's quite a lot)
    296.688 km with that consumption rate => total consumption 120 liter
    you refilled 16 liter => so you started with 104 liter (that's a big tank, isn't it?)

    However if you know the liters you had originally on we could calculate your consumption on the first stint.

    EDIT for the US Americans:
    1 gallon = 3.78 liter => tank size 27.5 gallons
    40.4465 l / 100km = 5.8 miles per gallon
    Last edited: Dec 10, 2010
  6. clacksman

    clacksman Licensed Racer

    I don't know my starting fuel load, that was my math problem too. 104 sounds odd, it's likely 100 to start. Try that and we'll see wat happens.
  7. RackAttack

    RackAttack Licensed Racer

    I can say from experience with my RX-8 at the track that 5-6 MPG is about right. A 28 gallon tank on the other hand... not so much.
  8. vkaifh

    vkaifh Licensed Racer

    wouldn't make a huge difference; your consumption rate would go down to 39.09 l / 100km
  9. Forgetful

    Forgetful Licensed Racer

    FYI, full is 100L. At least, it was in the Roadster. I ran out on purpose, doing the 4hr Roadster race at Tsukuba. I was able to drive for ~3'30 with my gauge reading empty.

    So, on 110L you went 276km (100x110/276) = 39.86L/100km
    Then, (100x6/14.8344) = 40.45L/100km

    Seems backing off may have had a minor impact.

    Edit: lol, seems I need a new picture of a tree
  10. clacksman

    clacksman Licensed Racer

    So the rate is plausible but the tank size isn't. Thatr's about what I thought before I posted. GT4 fuel tanks were 80L IIRC.
  11. clacksman

    clacksman Licensed Racer

    Purpose-built race cars hold 100L somewhat often, A '98 Celica with some bolt-ons ... not so much. My huge car holds 80L.
  12. Forgetful

    Forgetful Licensed Racer

    A quick look tell me a 100L fuel cell is about 2x2x1. Would fit fine in most cars in the game.

    So, just like we have to have Muscle Cars with ECUs (no carburetors), all cars in GT have a racing fuel cell pre-installed.
  13. Maineiac Moose

    Maineiac Moose Administrator

    Anyone else get nervouse when the car overtaking you is as wrinkled up as a slept in suit?
  14. clacksman

    clacksman Licensed Racer


    I kind of like it when a blue car goes whipping by me with the near side all blackened.
  15. Forgetful

    Forgetful Licensed Racer

    Can't say that I do...:rolleyes:
  16. clacksman

    clacksman Licensed Racer

    I'm most of the way thru the Indy 500 as I type this on a snack break. Minolta 88C-V with big turbo. I pitted when the right rear was dead (car loose in turns), so far 4 stops.
    Started on softs; needed 91L of fuel
    Took mediums; needed 88L of fuel and the last lap on those contained virtual death (~2 min lap).
    Took hards; needed 87L of fuel and may have been able to go 1 more lap but I didn't want to risk another 2-min in-lap job.
    Took softs; needed 91L of fuel again once the right rear died (it was definitely dead)
    Lap times were about .2 sec/lap worse per tire grade.
    Conclusion: Among Racing tires only buy Softs ever, there's no benefit to anything else.
  17. Mike_Delaney

    Mike_Delaney Licensed Racer

    Well, that's a little disappointing to hear about the tires. I was hoping that there would be a bigger difference in tire performance so that they would be a point of strategy.
  18. clacksman

    clacksman Licensed Racer

    Prehistoric thread bump because best thread I could find for this.

    With some of the GTL cars seeming a bit odd for weight balance % I thought I'd dig into it a bit comparing numbers found in GT5 (using fresh, unmodified car) with ones found on the interwebs. No doubt there's plenty of car-stats collections on the net, I used carfolio and CarType (seem good enough) and the Car and Driver magazine site (they measure all the stuff they test).

    Dodge Challenger SRT8 '08 (automatic)
    GT5 has it weighing 1878kg with 56/44 % distribution.
    carfolio has it 1891kg, 55.6% of that on the front.
    C/D has it 1899kg with 55.9/44.1% distribution.
    So that one is close enough to be within range of varying option packages and fuel load.

    Chevrolet Camaro SS '10 (manual)
    GT5 has it at 1755kg with 47/53 distribution.
    CarType has it 1755kg with 52/48 % distribution.
    carfolio has 1751 kg.
    C/D has 1751kg with 52.3/47/7 % distribution.
    So that one is very close except the in-game F/R balance is reversed from reality.

    Ford Mustang - Tougher one because I didn't find a dead-on car match.
    GT5 has the '07 Premium (automatic) at 1630kg with 65/35 % distribution.
    carfolio has the '05 GT weighing 1596kg.
    carfolio has the '10 GT (auto) weighing 1622kg with 54% of that on the front.
    carfolio has the '10 GT (manual) weighing 1603kg with 54% of that on the front.
    C/D has the '05 GT weighing 1621kg with 52.5/47/5 % distribution.
    C/D has the '07 Bullitt weighing 1603kg with 54.5/45.5 distribution.
    So GT5s' weight number is slightly higher than all I found (plausible as the in-game car is both the Premium model and automatic), and the distribution is off more than 10 % forward.

    edit: Conclusion: lolFord, or don't write down scale numbers when three guys are standing on it, or something ...
    Last edited: Jul 12, 2011

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