Gran Turismo Scientist symposium

Discussion in 'Gran Turismo 1' started by gtmaster08, Mar 12, 2009.

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  1. SportWagon

    SportWagon Premium

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    It always seemed odd that the lightweight parts don't change the total car weight, not even by a pound or two.

    It also seems odd how relatively unchanged the selection of car parts has remained through the series, even retaining oddities like lighter parts not changing overall weight, and arbitrary details such as (generally) maximum of three stages of NA tuning and 4 stages of turbo tuning (not to be confused with a multi-stage turbocharger, although it sometimes is).
     
  2. Parnelli Bone

    Parnelli Bone Premium

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    That's my point. Why say that lighter parts are being used, but then once you install them, there is no weight difference shown in specs? GT1 and GT4 are the only games that have an actual change when comparing weight specs between garage and track, so in these two games, it is possible PD could have programmed weight specs to change once different parts are in place. But apparently, they neglected to do so.

    In other words, if you have a Mazda Miata with stock weight, it'll be 2,160 pounds in the garage. But if you look at the track specs (GT1 features actual track specs for every car) the weight changes....i think it's like 2,139 pounds.

    Something like that. That's not exactly accurate, i'm just trying to to illustrate there's an actual difference between track and garage weight specs in GT1. :idea:

    Why is PD trying to illustrate this? Who knows. Maybe one weight is supposed to be the curb weight of the car, which is how much each car weighs when loaded with the proper amount of all fluids + a full tank of gas, but no passengers. But at the track, perhaps some fuel is supposed to be displaced? :confused: I'm pretty sure cars are shown as weighing less at the track than they are in the dealer & garage.

    But then (as SW notes) why go to this extent, but then not show a weight difference when lighter flywheels & the carbon shaft are in place? :confused: Or a lighter set of cams & manifolds, etc? Even in GT4, if you swap a stock shaft & flywheel for lighter ones, there is no weight difference shown in the garage. However, there is a difference in weight shown in GT4 between dealer/weight reduction specs, and what is shows in the garage.

    I believe that in GT4, PD is compensating for weight between garage to dealer. When you look at a car's weight in the garage, it's going to be less than it says it is at the dealer. I believe the garage weight is supposed to represent how much the car weighs when it's got an empty tank. But the weight shown at the dealer or tuner shop (when looking at the specs of each car before we buy weight reductions) is supposed to represent each car's weight with a full tank of gas.


    off-topic now, but i happen to know the Miata (in real-life) has its battery placed in the trunk; obviously this helps with weight distribution. True, a battery doesn't weigh as much as an engine or whatever, and the Miata has a 26-series battery, which is among the lightest, but i'm just trying to illustrate that even tho a stock driveshaft and a carbon driveshaft only vary a few pounds or kg in weight, Mazda seems as though they were really trying to be careful with distribution in the Mx5, so that replacing a stock driveshaft with a carbon one should make a difference in the car's balance and handling, no matter how small...
     
    Last edited: Mar 18, 2009
  3. LeGeNd-1

    LeGeNd-1 Premium

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    Well we all know how much mistakes PD has made over the years, I wouldn't be surprised if the weight difference between garage and track is just another one of their goofs. Why lighter parts don't change the weight is also beyond my understanding, but maybe it's more a technical related problem rather than laziness. Just imagine how many combinations of parts there are and how many cars in GT, trying to program all of the weights possible would take up the whole disc!
     
  4. Parnelli Bone

    Parnelli Bone Premium

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    I don't think it is a goof in GT4, but it could be in GT1.

    If you do an endurance in 4, and start with a full tank of gas, and your power hasn't been temporarily tweaked with an oil change (so power stays constant thruout the race), your speed down a long straight will be a few mph (or kph) lower when your tank is full than it is later in the race once you've got a near-empty tank. I've won endurance races this way, by running my tank drier.:idea:

    So in GT4, i think PD definately took this into account, and garage versus dealer/tuner shop weight is supposed to show the possible difference. Whatever, tho. Just my theory.

    I know. It would be very nitpicky if someone sat there programming every little detail of a car's weight (and tried to do so accurately). I was just trying to open discussion in a sort of theoretical basis so far as possibilities go. I would be VERY surprised if (in GT5) Pd started getting super-anal about every little detail

    ...even tho at the same time, such little details are the ones that please me most. :D
     
  5. SportWagon

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    I'd assume the car weight would be just a parameter used in some calculations. If they can model fuel consumption, they ought to be able to model a few pounds reduction for lighter parts. True, accounting for where the weight was lost from would be more difficult, but that would just be the weight (mass), plus a 3D location in the car model. Easier than fuel consumption, since the calculations would be evaluated before the race to create the in-race working model. And, on disc, perhaps 32 extra bytes per part maximum. Around 100Kbytes, or a minute proportion of 9G.

    Of course, having a variety of weight combinations might complicate play testing (I wonder if play testing is why [size=+1]GT4[/size] lineups are predictable to some degree?), especially as weight affects A-spec value. (Ooh! Those wouldn't be free upgrades anymore!--but the game would also need to determine what lightweight parts to give AI cars too, etc.)
     
  6. Parnelli Bone

    Parnelli Bone Premium

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    ha ha..who knows?! Someday some ex-PD disgruntled employee is gonna show up here and spill all the secrets.

    Where the hell is our host by the way? Our Scientist Symposium leader? :boggled: Dude i want my 50 credits for getting this thread on-track for ya! :lol:
     
  7. viperin

    viperin

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    I reckon your thoughts are worth 100 Cr at least !
    Good stuff.

    I wonder if the weight of lighter parts does not seem to compute, as extra parts are usually added as well, rather than lightweight parts in isolation ?

    What I mean by that is, adding a lightweight part is cancelled out by the weight of the Turbo (for example ) upgrade ?
     
  8. nk4e

    nk4e

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    Why not get some actual data on this? The miata would be a good example because of the 50-50 Power to Weight Ratio. ( so will the S2k?) But do minor add-ons to keep that same weight distribution. Record Time Trials and see if we could get something.
     
  9. Parnelli Bone

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    It sounds like you've got all the ideas! Why don't you try it? :idae:
     
  10. nk4e

    nk4e

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    I don't have the ideas and I will find the game again and do it with the Miata and will report back.
     
  11. SportWagon

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    I know for a fact that adding power upgrades never adds weight, and adding (only) lightweight parts does not reduce weight.

    The fact power upgrades don't add weight is a good rationale for why adding lightweight parts shouldn't reduce weight. It can be argued that the two simplifications approximately cancel each other out.
     
    Last edited: Mar 25, 2009
  12. Parnelli Bone

    Parnelli Bone Premium

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    So far:

    A room is rented at a conference room at the local VFW hall, the Gran Turismo Scientist Symposium is under way! Fliers are posted, bulletins posted, calls are made, yet the only people showing up are a couple of hecklers.

    Some of the hecklers demand that the host shows some proof that he is an actual college-educated scientist. Other hecklers simply have a joke or two. The Host says the term "scientist" is being used in a rather prosaic manner. He's not really a scientist per se, and the guests that show up don't have to be scientists either.

    The heckling continues. Finally, one of the "scientists" who previously made a heckling comment decides he's going to address the floor in a serious manner. Actual topics are raised. Other scientists join in to find solutions via the Scientific Method.

    The host goes out for a smoke break (apparently) but never returns. Awkwardly, the remaining guests have a go of keeping conversation alive in hopes the host will come back and lead the way; but eventually, all the pretzels are gone, th e Kool-Aid drunk away, the popcorn bags are empty..



    :guilty:
     
  13. nk4e

    nk4e

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  14. LeGeNd-1

    LeGeNd-1 Premium

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    :lol: Good one Parnelli :lol: Makes me wonder, when are you going to continue the GT2 story again?
     
  15. TheBook

    TheBook Premium

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    No.

    We don't need another good thread getting shut down. :lol:
     
  16. Parnelli Bone

    Parnelli Bone Premium

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    Yea i should get on that story again. :)

    And it looks like the Kool Aid man is here, at least we have somthing to drink :dopey:
     
  17. SportWagon

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    If you have access to a slide-rule, you can use the C1 and D scale to calculate maximum speeds for different gear ratios.

    Simply line up the maximum speed on the D scale with the gear ratio on the C1 (inverse scale--this requires using the cursor). The ratio used can be any of final drive, gear ratio, or the "effective ratio" product, so long as it's the inverse or denominator value such as used in the [size=+1]GT[/size] series. Your slide rule is now a chart which (as long as you scale correctly) reads on the D scale the maximum speed achievable (assuming sufficient power) if the chosen ratio is changed to the value chosen on the C1 scale.

    When reacquainting myself with this, I found it convenient to use my circular slide rule since the ratios often do move their decimal point.

    For instance, line up 95 on D with 1.64 (the value of the previous gear in the line). The D@C1 scale then reads 49@3.18, 72@2.18, 126@1.24, 155@1.01, (confirming the other figures in the chart) and... 168@0.929.

    So at 8200rpm, we should be going 168mph in 6th gear.

    So let's line up 168 on D with 4.29 on C1 (our final drive). 2.700 actually lines up with 266mph, suggesting other things are slowing the car down at that point. That calculation is actually confirmed by the in-game chart which shows a speed of 247 for getting into 6th (maxing 5th), and also observations of engine speed in 6th gear. (Though, in fact, when observing the tach, I have difficulty believing the speed at 8200rpm in 6th isn't a little over 168).

    240 on D actually lines up with about 2.98 on C1, so let's try a final drive of 2.98, and see if it makes things any better or worse.

    It seems to make things slightly worse. Now why would that be? Well, we need to look at the power curve (Change Parts: NA Tuning) with stated figures of 439.7ft-lb@6000rpm Max Torque, and 568hp@7000rpm Max Power. We really should not be trying to drive the engine up to 8200rpm at high speed. In addition, and related, it leaves us with only two gears, instead of three, to use as speed drops around the banking.

    Roughly speaking, when you change up gears, you want to end up at the maximum point on the torque curve, but, in fact the lower gear will have more effective torque for given torque, and so you'd compare the torque in the gear you are in to T2*G2/G1 at rpm you end up, and shift when that latter figure is higher (i.e. when you've gone so far past the point where the torque curve drops off that the real torque loss caused by the higher ratio is offset by the torque gained by moving to the new point on the curve).

    T2 = torque figure in new gear (at new rpm)
    G2 = gear ratio of new gear (smaller denominator value)
    G1 = gear ratio of current gear (higher denominator value)

    Note that the torques in question will be at different points on the curve (corresponding again, in fact, to the ratio of the gear ratios; also there will be rev loss caused by shifting).
     
    Last edited: Mar 28, 2009
  18. Parnelli Bone

    Parnelli Bone Premium

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    Wow. First i need to get a slide-rule, i guess
     
  19. Blitz187

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    Hmmm this thread got longer than I thought it would, but I see that the host has not come back... :lol: Where is he???
     
  20. SportWagon

    SportWagon Premium

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    Probably looking for his slide-rule.
     
  21. tsamuel60

    tsamuel60

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    Hello everyone, I am new to this website. As you see here, I am known as tsamuel60. I found out about this website through some of my friends at work. So I decided to give this forum a try. And by the way, who is this "gtmaster08" guy? Is he the leader of this thread?
     
  22. gtmaster08

    gtmaster08

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    Hello everyone, I'm back! I do apologize for my absence, I was a bit busy doing some important research on some other games. Anyway, the "redlining" topic of the symposium is done for now! Now I will do a Q&A with the other "scientists" on this thread. In other words, ask me anything about Gran Turismo 1 and I will answer to the best of my ability as a part of my research!:) And don't worry; I'm here to stay because I was able to complete my extensive research on my other games! Oh, and one more thing.

    To Parnelli Bone: :lol::lol:MAN that story of yours was freaking funny!:lol::lol: Where do you GET this stuff from?!:)
     
  23. Smallhorses

    Smallhorses Staff Emeritus

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    Being as you and gtmaster08 share an IP address in common, meaning you've both posted or viewed GTPlanet from the same computer, I'd guess you should already know that. :sly: (Perhaps somebody from your work)

    Please take time to settle into :gtplanet: have a look around and enjoy the site.
     
  24. gtmaster08

    gtmaster08

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    Well actually, there was a friend of mine at work who I told about the website. He wanted to join so I signed him up and he confirmed his e-mail letter. I was just seeing if he would be able to do a post, and apparently he can. That's why the IP address is the same. I hope that this clears things up.
     
  25. Parnelli Bone

    Parnelli Bone Premium

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    Where's your sliderule? :odd: This is no time to be coy, sir.




    ...i'm kidding.
    :)
     
  26. nk4e

    nk4e

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    More Kool-Aide and pretzels then?
     
  27. gtmaster08

    gtmaster08

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    Ok, now we're moving onto the next topic which is... looks through an envelope

    drumroll

    Aha! Oversteering! And I will start by asking this; what do you think causes oversteering (other than car drivetrain) in the game?
     
  28. Parnelli Bone

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    Well first of all, a drivetrain alone can't be the sole cause of oversteer. Not all rear-drive cars oversteer as a guarantee, for instance. At least outside of the world of GT1.

    That being said, here's a couple of guaranteed causes.

    1). The most obvious. An overload of power from the engine, which causes tires (usually the rear tires) to break traction. Then the car starts sliding from the rear.

    2). There is also what i like to call "body-sway oversteer". Cars that have a high center of gravity display BSO the most. This means that as you corner harsly, weight is transferred to the outside rear, causing the rear of the car to slide around. At the very worst, the outside-rear tire gets overloaded and now you've got yourself a spin. :ouch:

    Lots of cars display body-sway in GT1, GT2, and GT3 (not so much in the 4th game). This includes some front-drive and all-wheel drive cars, not just rear-drives.


    There, that should start things off for part II of the Symposium :p


    All that being said, it's my opinion that oversteer isn't represented very well in GT1 (sorry TMM and HYBRIDLVR!). So many cars oversteer grandly in GT1 (but feel more contained in later games). You can literally do a side-by-side comparison between GT1, GT2, GT3, and GT4 with some Lancer Evos, Mk4 Supras (that's '93 thru '99) RX-7 Infini III, and Viper GTS, to see what i'm talking about. Just turn the wheel sharply in any corner, and the rear breaks traction in these cars. With another simple flick, you get it all back under control. Fun, but not realisitic. There's not as much a sense of danger in GT1 with oversteer.

    I'm not bashing GT1, just stating some observations. For its time, the physics model certainly blew away any other racing game from the mid-'90s or earlier that i ever played.
     
    Last edited: Apr 7, 2009
  29. AERO_HDT

    AERO_HDT

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    Gee, there's one guy claiming to be a wizardly scientist who knows everything and asks all the questions like a teacher with a room full of pupils.

    The pupils are evidently a lot smarter than the teacher however (I think he has come to realise this), so thus this will be a clever thread about a supposed teacher "educating" his pupils, LOL.

    Shouldn't the scenario be the other way around?

    ;)

    The dealership weight / garage weight in GT4 I always assumed was the same, I have not noticed any difference between the two (assuming I read past posts correctly). The fuel/lap speed issue has of course been a life-saver for me on many occaisions, perhaps the only reason why I have won some enduro races. If only the AI were clever enough to do the same....

    Speaking of the driveshaft issue, it is my understanding that it does not affect the FR/RR weight distribution at all in GT (I have yet to see proof of this, only speculation), and rather than it being a weight reducing item, it is merely considered by most as a method of minimising drivetrain loss, enabling the car to transmit more power to the rear wheels. I don't know if the physics engine in GT was complex enough to calculate drivetrain power loss, but the fact that a carbon fibre driveshaft gave the car an increase in speed (but not horsepower) suggests that perhaps the physics engine does indeed calibrate such things.

    As for BSO as Parnelli eloquently puts it (inertia oversteer would perhaps be a better term?), it is something that just about any car an attain if driving poorly or harshly enough. The difference I noticed between GT and later physics models was that there was always grip at the front wheels in GT and understeer only really became an issue on very long sweepers or when you were powering out of a corner too early. As all four physics models have been different in many ways to each other it makes you wonder whether or not you could actually formulate a set physics engine difference between the games? Was the physics engine in GT2 averaging a second a lap faster than GT1? Was GT3 slower than GT2 and was GT2 quicker than GT4?

    And another question, does the fitment of an LSD increase the chances of oversteer or induce understeer? I've driven my own car with an open spinner diff and the understeer is not pretty, yet after the fitment of an LSD, I found it easy to get the rear dancing around.

    Jaguar refuse to fit an LSD to their XKR because they claim that it increases understeer too much....

    Hmmm....
     
    Last edited: Apr 8, 2009
  30. Parnelli Bone

    Parnelli Bone Premium

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    I've noticed it. Look at a car's weight at the dealership when it's new (or unbought). Buy it. Get a weight reduction and note how much the car is supposed to weigh (according to the weight reduction spec) with Stage 1 in place. Now compare the car's weight in the garage to what it's supposed to weigh after weight reduction 1. I've noticed it's off by a few kg, although i haven't checked this with every single car i've reduced weight with.

    At this moment, i'm forgetting if kg varies while the car is still stock (no weight removed).

    Me too.

    :tup: I agree.
    I've personally only compared the same cars one after the other if they appear from game to game. My feeling is that with each successive game (GT..GT2..GT3..GT4) an Infini III, Mk IV Supra, Lancer Evo, etc. feels more "dialed in". GT obviously has the most primitive feel, wheras in GT4, things are now more complex.

    But GT4 lacks a few traits (mostly oversteer and low-speed manuevering traits) found in earlier games, and is unrealistic in this way. We've all experienced this with GT4 by now, so i'm not going into heavy detail...

    ...plus, Sportwagon won't let me borrow his sliderule, so i can't do a scientific analysis at this time. :lol:


    I can't comment on real-life stuff, but in GT2, 3, and 4, LSD upgrades reliably induce understeer. Generally, oversteer vanishes more and more the stronger those LSD settings become. :idea:
     
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