As promised here is a 'report of some kind' with regard to some experiments in how the chassis and suspension adjustments in GT4 appear to work. It's a bit disjointed as it was written over a couple of days and sees my opinion waver from 'somethings astray' to 'things're okay'
. I hope that it'll be of help to someone anyhow, particularly as it stays (mostly) away from technical language and focusses purely on empirical observation.
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Trying to tune up an Aston Martin Vantage so that it's fun to drive.
It has lots of weight and wags of torque, which means that it spins up the rears very easily in low gears and punishes tyres.
Trying some experiments with Dampers to see what effects changing just those has on the handling of the car. The circuit is High Speed Ring and the tyres are feeble S2's (feeble with all that weight on them at any rate
).
I found early on that there was high speed understeer (in the fast sweepers) and lift off understeer too (in the slower corners lifting the throttle did not encourage the nose to tuck into the line).
I set the Bound at a level 6/6 and tried the Rebound at a traditional 9/8. The understeer noted above was the result. Tried 9/10 and found that straight line speed was improved (huh? Might be better traction on corner exit) but the cornering understeer was more pronounced. Cut the Rear Rebound to 6 and found that the car was much more inclined to turn and hold tighter lines. Cut the Front Rebound to 6 and found that the understeer came back. A setting of 8 was pretty good. 10 seemed an odd mix where sometimes she would really cut a good line and other times the load on the tyres seemed too much and she'd run wide. There did seem to be a modicum of throttle steer available too, if you didn't go too mad with the loud pedal too early in a corner.
Put the Rebound back to 8/6 and try increasing the Rear Bound. It seems to increase entry oversteer but also increase exit understeer. Swap it around with 8 Bound at the Front and 6 bound at the Rear. It was a case of more understeer going in (as if the tyres were being overloaded under braking) and more oversteer coming out. Try 4/6 Bound (with 8/6 Rebound). Not bad handling actually. I was able to use power oversteer to control my exits from corners quite nicely and didn't find corner entry understeer too much of a problem if I braked properly (she would wash wide if you didn't get down to a slow enough speed for the tyres). Back to 6/6 Bound and 8/6 Rebound for a comparison run as I've gotten faster and faster laps as I've gone and want to make sure it's hardware changes rather than wet-ware improvements
.
It feels like a swings and roundabouts deal, 4/6 gives you more oversteer on exits and thus more speed into the straights whereas 6/6 gives you more stability into the corners and thus allows you to set your apexes better. They're about as fast as each other but the 4/6 is marginally quicker in the laps I've run.
I'm noting that these observations do not correspond with accepted tuning wisdom from the real world. It is in fact backwards as Front Bound and Rear Rebound are supposed to come into play during corner entry and Rear Bound with Front Rebound are the controlling factors on exit. For oversteer on entry and exit I want Soft Bound and Stiff Rebound at both ends. Try her with 3 Bound and 9 Rebound to see what I get. I could feel the oversteer was there actually, it was especially noticible in the slower corners. The laps were much slower however. Invert it to 9/9 Bound and 3/3 Rebound. I can feel the general understeer there but it seems also to translate into more grip and so lap times are not too far off what I was getting before with 6/6 and 8/6.
Put 4/6 and 8/6 on for comparison run. Faster than both the 'extreme' settings. Ah, a spanner in the works is that the HP has dropped. Oil change time. There is without a doubt more corner entry understeer with this set-up and more corner exit oversteer (especially on the power in an FR car).
I wonder if this is an opposite corners situation? Try reducing the Rear Rebound to match the Front. Much slower. There is an appearance of mid-corner understeer which means you have to throttle off. Back to 6/6 & 8/6 and got my fastest lap and a definite impression of more exit understeer but more 'bite' going in on the brakes.
The basic canon of knowledge is that if I want more oversteer on corner exit then I should increase Front Rebound and reduce Rear Bound. Try 6/5 and 9/6. I got more exit understeer, I'm positive of this. Assume that PD have coded it so that lower numbers mean slower Rebound i.e. more resistance. Keep Bound at 6/5 and put Rebound to 2/4. I got more exit oversteer and more corner understeer. Case almost proven to me I reckon. Reduce Bound to 4/4, 6/6 and 7/7 (three seperate sets of runs) to see if the 'inverse stiffness' applies there too i.e. that a lower number means a slower response. 6/6 was by far the best set and produced my fastest time so far. There seemed less grip and more tyre noise with 7/7 somehow and I didn't like the cars response at all. I would guess that means that high Bound values mean stiffer shocks (as per 'reality').
The cars weight is 1635KG and I'm running springs at 14.0/14.0. Maybe 16.4/16.4 Spring Rate is an interesting experiment? Feels more stable but is not quite as fast. Perhaps the springs are overpowering the Dampers? Assuming inverse Rebound then I'm running total shock stiffness of 15 at the Front and 13 at the Rear. Put the Spring Rates to that and test. Get more understeer. Try for a while and get used to it but it's still slower than the 14.0/14.0 I had originally. Put 16.4/16.4 Springs back on and adjust dampers to 7/9 & 2/4. Not too bad for feel and handling but slower than before. To check for any degradation of the car, put it back as it was. Not as good now ... give up as I'm too tired to drive with delicacy and am trying to force it. Ah the chassis refresh has gone. Try again tomorrow with a refreshed chassis and oil so I can compare like with like.
To recap, running the following set-up I was lapping at 1:14.0 to 1:14.1 (BL 1:13.895):
Springs: 14.0/14.0
Ride: 83/83
Damper Bound: 6/6
Damper Rebound: 2/4
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 6/6
The following gave the same:
Springs: 16.4/16.4
Ride: 83/83
Damper Bound: 4/6
Damper Rebound: 8/6
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 6/6
Changing it to the following set-up gave me 1:14.3 to 1:14.5
Springs: 16.4/16.4
Ride: 83/83
Damper Bound: 7/9
Damper Rebound: 2/4
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 6/6
The car felt very planted with this set-up but the ability to throttle steer was reduced which resulted in a tendency to push mid-corner to exit. Increasing Rear Bound is supposed to give more exit oversteer so I'm a bit confused there. Perhaps it's a case of simply too much rear grip and that's overriding the effect of the dampers high resistance? Put Rear Bound to 7. Less solid feel to handling and the tendency to run wide on exit is increased a bit I reckon (hard to tell as I got involved with 'Ghost Chasing' in the session
). Times similar to 6/6 Dampers. What does 9/7 Bound get me? Hard to tell; it's as if the chassis is a little confused and grip becomes unpredicatable.
Noticed that HP had dropped again, thus invalidating some of the above.
Ran with:
Springs: 16.4/16.4
Ride: 83/83
Damper Bound: 6/6
Damper Rebound: 2/4
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 6/6
Got noticeable corner exit understeer at high speed and lift-off understeer too; indicative of too much rear end grip. Stiffening Rear Bound should lessen that. Try 7. Seems worse. Try 8. Is better, I must have been getting a weird harmonic glitch with 7. The car is showing a tendency to understeer going in to a corner now. Try 9. As before when tried with Rear Bound this high, the car felt very planted but times are still in the same 1:14.3 band i.e. slower than with 6 Bound.
Try 7/7 & 2/2. Very good, as good as my previous best set. The only thing is a reluctance to take an attitude going into a corner - entry understeer.
The 'proper' cure for this is to Soften the Front Bound and Stiffen the Rear Rebound. Put Front Bound to 6 and Rear Rebound to 1. Worked quite well in the fast corners and vey well in the medium to slow corners.
For a final check, put the Front Bound to 6 but the Rear Rebound to 10 i.e. going from what may be Full Stiff in the Inverse System to what would be Full Stiff in the Orthodox System. Performed very similar times (a bit faster actually) and generally felt much freer, especially on the power oversteer and reduced turn-in understeer. The only way I can explain that is ... nope, I can't
. After seeing some evidence that LOWER Rebound values mean Stiffer, I find here that HIGHER values give me the correct 'stiff damper' responses. The turn-in response to power was quite marked, such that I had to back off the steering at times to avoid apexing too early (that qualifies as genuine oversteer in my book).
My guess would be that the game, incorrectly, uses the ratio between the Front and Rear Rebounds to create understeer or oversteer. Swap Front and Rear values and see. The high value Front Rebound, coupled with the very low Rear Rebound, meant that Front end pointability was excellent, such that the car felt very good through the first high speed left hander (by far the best so far). Braking into corners tho' seemed to exhibit a tendency to wash wide and a reluctance to tuck the nose in, exactly what you'd expect from a high Front Rebound as you come off the brakes and steer more deeply into the turn.
The only conclusion I have at the moment is that 'lap times don't lie' and with a high torgue, heavy, FR car the fastest times I got on this track (BL 1:13.614) were from using dampers set to 6/7 & 10/2. This made the back end quite light and allowed good throttle steer as well as causing the nose to track well through the apexes of corners (altho' a bit of understeer was detected in Stage 2 of entry i.e. brakes off and steering increasing).
Springs: 16.4/16.4
Ride: 83/83
Damper Bound: 6/7
Damper Rebound: 10/2
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 6/6
In the search for some ratios I can use, the relevant car stats are weight of 1635KG and Length of 4745. The total of Front Damping adds up to the Weight of car/100 and the total of Rear Damping is about half that.
Some random notes that may become relevant:
I've noticed whilst playing the game that the Front end is given much more emphasis than the rear (such that the game takes no notice of what tyres you put on the rear when it comes to calculating A-Spec points for example).
Utterly disregarding real world information on tuning, it seems, in-game, on some cars, that increasing the Rebound value at the Rear end gives more understeer on exit and increasing the Rebound on the Front end gives more oversteer on exit (which it shouldn't be affecting really).
The bottom line seems to be that for exit oversteer you need a high Front Rebound and a low Rear Rebound. If you want exit understeer (or a sense of 'pointability') then use a low Front Bound and a high Rear Bound. For just a feel of better stability out of corners tho', just a click higher on the Rear Bound seems to help.
I think that this car is an extreme example due to it's great weight and massive torque, which the game doesn't simulate well at all, but I think the principles seem fairly clear. As a caveat, because the rest of the suspension wasn't dialed in, simply set to be stiff, the results are by no means conclusive as before you can truly fettle the dampers in the real world, you have to get your springs and stabalisers and general weight balance right first.
I will try the above procedure with another car. Keep to my favourite FR drive train but go for a lighter, less torquey model ... and one that hasn't been daubed with the Anti-Non-Nippon Dehandling Brush
.
A Honda S2000 Type V '00. Buy all the suspenion and transmission toys and lighten it down still further (Stage 1 1260KG reduced to 1146KG, Stage 2 down to 1108KG (Stage 3 would give 1071KG but don't buy it). Put on a Racing Chip, Racing Exhaust and Stage 2 NA tune with an Oil Change (307HP). I don't know if this'll be fast enough to show up suspension changes in Turn 1 but we'll see. I was right - the S2000 handles perfectly around this track and shows no vices with Dampers at their stock 8/8 & 8/8. Perhaps a little too responsive on turn-in at high speed.
Springs:11.1/11.1
Ride: 96/96
Damper Bound: 8/8
Damper Rebound: 8/8
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 6/6
Try the same ratios as for the Vantage but proportionally less: 4/5 Bound and 6/2 Rebound. This gave slower straight line speed, understeer when braking into corners and a nicely balanced oversteer on the throttle on corner exit (lift-off oversteer also). Put 6/6 Bound on. The nicely balanced oversteer ha diminished somewhat but has been replaced by a fraz of understeer that gives a sense of stability and actually allows faster exits. The braking understeer remains. Try exactly the same Damper settings as for the Vantage. Handles quite nicely and goes two tenths faster than before (BL 1:16.345). Try a more traditional 6/5 and 9/8 set-up. Slower by a couple of tenths, less grip mid-corner on fast bends, improved turn-in under braking, nice throttle-on exit lines. Try 5/6 & 9/8. Very good. The extra Bound at the rear, which should give more understeer, translates as extra grip allowing fuller use of the throttle. Try 5/6 & 8/9. Perhaps a bit better but it's very hard to tell but it 'feels' nicer to drive. The nonsensical 6/7 & 10/2 is still pretty fast but the last damper arrangement has it beat here.
Took her to a Family Cup race, at maximum difficulty and took a very easy huge win for 197 A-Spec Points (no Pro-Nippon bias there then
).
Want to work on a theory that the 'Anti-Logic' Dampers can be turned back into proper function by correct balancing of the other chassis factors. Go back to the Vantage and get the stock chassis figures:
Springs: 9.6/8.4
Ride: 98/98
Damper Bound: 8/8
Damper Rebound: 8/8
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 5/5
Not badly handling at stock settings, the most obvious handling flaw being lift off understeer and a tendency to understeer on constant throttle. Lap times are slow at BL 1:14.3.
Weight Distribution seems to be 53.3/46.7 going by the static spring rate snapshot. Try altering the springs to 9.6/9.6 and moving the Weight Distribution Slider to -15. A feeling of improvement in the handling in that the lift-off understeer disappeared but the lap times did not improve. Try +15. Definitely more oversteer and the ability to use power-on oversteer more freely whilst power-off understeer has lost that 'jerk' to the outside that was evident before.
Increase the Spring Rates to 16.4/16.4. Handling now feels quite good and stable but the lap times do not improve and there is still understeer in the chassis. The Brakes at 1/5 help with corner entry turn-in but don't materially affect things on this circuit. Ah, HP has dropped again to 539. Go get an oil change HP=565. Re-run last test. 1:14.3's.
Lower Ride Height to 83/83. Instant improvment to 1:13.8's.
Stiffen stabalisers to 6/6. Feels tighter but loses traction at the rear a bit too much I think - doesn't affect the line but does lose exit speed. Try 6/5. Slower by quite a bit altho' the handling feels a lot nicer, less chance of messing it up. Try 5/6. Again, the lines feel very good but it's just not quite as fast. Try 6/7. Nope. The rear is too loose and yet there is a ceratin degree of understeer too in parts of fast corners. Stick to 5/5, it's defintiely faster.
The cars handling fine as it is but is two tenths slower than the Improbability Drive set-up I had before. Put the Bound to 6/6 and the Rebound to 9/9. Excellent! Got back into the 1:13.6's and even put in a 1:13.5. So, if you sort out the crippled chassis balance first then the dampers seem to work as you would expect them too - that's quiet a relief at the moment as I was beginning to worry myself with the outputs I was getting at the start of all this.
Now try the 'Heart of Gold' Settings on the Dampers: 6/7 & 10/2. Thankfully they're not faster, tho' they are as good and, to be honest, I find that the rear is much freer flowing with them; ah well :shrugs:.
I actually like that result as it suggests that there is more than one way to skin the tuning rabbit i.e. you can fix, to an extent, flawed chassis modelling by using more than one method.
Put her to the following:
Springs: 16.4/16.4
Ride: 83/83
Damper Bound: 6/7
Damper Rebound: 9/9
Camber: 2.0/1.0
Toe: 0/0
Stabaliser: 5/5
Test her out in a max. difficulty Family Cup race. Got a nice 194 Point victory.
Just to round this off, note that the above testing was quite exhaustive (it wsn't a case of change a setting, run a lap, reach a conclusion). I went through two chassis refreshes and a number of oil changes on the Vantage, so that's quite a few laps under the wheels
.