Originally posted by bread82
Hi SiNiST3R,
You don't know me, but I have been reading GT tuning guides since GT4 (mostly on GTP). I've written a couple of posts there about the ride height bug, and how I believe that the high-front low-rear was adding caster, which affects camber behaviour during steering, potentially causing a great turn in, but then understeer later in the corner as the camber becomes too much. There could well be other factors at play as I don't know how roll centres etc are modelled. I happened to find the NGU forum the other week and what you have written (about all aspects of suspension) interests me.
I have a few questions and would appreciate your thoughts:
Cheers,
Bread
I will try, Im getting a bit swamped on a few angles but I will try to address everybody.
Originally posted by bread82
1) You mentioned that PD appear to use a leverage factor and spring rate to hit a target freq. Do you know why this is, rather than just doing a single parameter "wheel rate" to give the desired frequency? Is it something to do with their "standard car geometry" which they then modify to fit real world cars?
In my opinion based on the adjustable parameters in the game and the hidden cars specs in the SpecDB PoDi uses the leverage factor and spring rate because we are adjusting the spring rate, we need the factors that go into the motion ratio individually to make a dynamic value adjustable over a fixed value. The Motion Ration is a product of the spring rate and overall leverage factor of the suspension geometry and used with the sprung weight to then get a frequency. Motion Ratio is basically the dynamical spring rate seen at the tire contact patch.
Originally posted by bread82
2) Do you know if their target freq is the same front and rear, I think your calcs where you find the leverage factor front/rear difference assume equal target freqs front and rear? I was wondering because in real life rears are often ~10% higher freq (for street cars). Can you see the raw freq data?
No the frequency is changed as any parameter is changed, as tuners our goal is to balance them out on our set up. The target data I believe comes from KW 7 post rig data and I would assume would be based on results from testing cars on the rig. Tuning frequencies the usual goal is relatively equal a little bit higher frequency in the rear, but the cars are measured on stock suspensions not tuned for the track in most cases so its hard to say, but I would assume no unless the car tested measured a balanced F/R frequency.
Originally posted by bread82
3) Roll bars... you mention that you can see the proper stiffness rather than just a "1-7" scale, and that they're different front and rear... are the roll bar values real life values that have been put in, or are they modified like the springs? I often wondered if they're proportional to PD's spring values. Also, do you know if the roll bars use the same leverage factor as the springs? I'd love to be able to guess at how much a bar click is worth - don't know why PD didn't put the units in!
In order to know this I would have to have a lb/in or kg/mm measurement for a set of factory roll bars. The bars in the game are in fact measured in kg/mm as bars can be IRL, but often looking at a factory sway bar IRL we get thickness but no real kg/mm spec, improving performance is often measured in thickness above stock as apposed to a kg/mm reading per bar. Keeping in mind some brands like EiBach will give lb/in specs for their bars (not always) easily converted to kg/mm and while we cant tune in the specific kg/mm we usually can get relatively close.
Originally posted by bread82
4) In tuning, I generally set my springs first (after power/weight/tranny etc), then set the dampers, then start to play with roll bars. In your opinion should dampers be set to also take into account roll bars? i.e. if I have soft springs with sensibly set dampers, and stiff roll bars then my car will be perfectly damped in pitch but presumably underdamped in roll.
Yes and no. The dampers and spring rates go together and adjusting one I find always best to adjust the other to insure the one is in tune with the changes to the other. Spring Rates and Roll Bars ultimately generate the total roll resistance together, if my roll coupling is set and I need to adjust either the SR or ARB, I have to adjust the other to keep my roll coupling. Having had to adjust the SR, that means I should revisit the damps again to insure they are tuned in to the changes.
PERSONALLY I use an advance damper tuning technique cross tuning dampers for cornering performance breaking the corner into multiple sections. Before fine tuning the damps in the corners I make sure the damps are well tuned for the SR/ARB combination with general front and rear under/over dampening tuning damp to spring. When I dial in Dampers for cornering performance its after the springs/damps/arb are already tuned together and when fine tuning the damps in the corners this way I do not touch the spring rates or ARB during tuning.
There are a few ways to tune dampers, however the end results can most often be quantified in under or over dampened and then one would address the dampening individually as the case calls for it. For me this is dialed in ultimately when fine tuning the dampers in the corners.
Hope Im being helpful
Originally posted by RocketScientist
Good work there, im into drifting, what about default lsd on some fr cars with 80 value on acceleration and 50 on intial ? is it the same inside specdb ? what does 80 value mean compared to maximum 60 on custom lsd ? will it give special effect as im told 80 value on accel are on cars with torsen or vlsd. for drift is just use all 60 60 60 or 60 60 5
Interesting question. Its hard to say for certain what "60" or "80" represents, I'm not certain it means % of lock (although that is my suspicion) I will do some testing with a hybrid. Ill change the settings to 100/100/100 and see what happens, if I get full lock. I figure that if its locked I will get to see it in the data analyzer wheel speeds. Then take it from there... Ill also check if the cars with 80 settings (I think a Z car) is similar to the Miata LSD the codes are posted for as you may notice it has a 1 way diff. I think very few cars have a default 2 way set up (the GTR's run a full 2way set up), most cars have a 1.5 way set up default. I think your asking if the INT can offset the limitation of the Accel setting, 60/60 vs ??/80, I believe it can and should as long as the stock int isn't too high on that diff with an 80 accel, lol but needs testing to be certain, wheel speed indicators in the data analyzer should give some insight.
The LSD is something Ive yet to dive deep into in GT6 code / testing to get any certainties. I dont take much at face value anymore as behind the scenes it can be much different, so everything needs a bit of looking into to say anything for certain.
Looking at the SpecDB data posted there is little reveled except a shared diff "type" among vehicles. I see an additional accel and decell code but both mirror the DF settings so Ill have to look into that further on more cars, the same with diff type, now Im looking for different types and to see how type 109 looks to be the standard adjustable.
A lot on the plate apologies if Im going a bit slow trying to address everybody.