Special Review by @@Lewis_Hamilton_ driving both GT6 version replica and Assetto Corsa and 1080/60 fps video of the lap at Spa on both GT6 replica and Assetto Corsa Yellow Bird :
Ok, so I've ran some laps of the 38/62 weight distribution set up in GT6, and then hopped on to AC (both games running at the same time). Tried some laps at default LSD (40%), and at 80%. There's also the option for 60% which I haven't tried.
Initial impressions are that GT6 is both too slippery and grippy at the same time, if that makes any sense whatsoever, and I'm wondering how much of this comes down to GT6's track grip settings, broken camber physics and pandering to the casual players. Between the two games, I matched the same time of day, ambient temps and weather conditions (50% GT6 / mid-heavy cloud cover AC), and in AC I set the track to optimum conditions - which is the equivalent of a whole field of cars that have rubbered in the track for many laps. The reason why I've picked this rather than a none rubbered in track that's slick and slippery is because the YB in AC would be even slower. Interestingly, the look of the lighting/atmosphere in both is very similar.
As for the car:
In GT6 with 38/62 WD, the back end steps out both more frequently, easily and by much greater angles, but at the same time, it is still holding higher cornering speeds and is easy to recover, not once did I spin or go flying off the track. In AC, both with 40% and 80% LSD, the car feels more stable/planted but has lower cornering speed ability. 80% feels too safe to me however. The biggest difference is that in AC, you only need about half of the momentum of the weight shifting around at the rear in order to put the car in a situation where it is impossible to save and you end up facing the wrong way, no matter how quickly you react, what you do with the pedals or steering wheel. If you try and shift the weight around quickly, it's going to spin every time, where in GT6 it turns into an angled drift which you can save.
Another thing I noticed is that there is more wheel spin in AC - coming out of any corner in 2nd gear - despite GT6 being on the 2nd least grippy set of tyres. To match AC in this regard and cornering speeds, I think you would have to go down to CH tyres. In my opinion the problem is when you do that on GT6, it starts to feel like you're driving in the wet, you just don't have that feeling of connection with the road. Trying to match what I was doing in GT6 either resulted in going wide or the rear coming around despite initially being at much lower slip angles than GT6, but I have always complained about this issue for lord knows how many years, GT6 is just too forgiving and allows you to be far too aggressive, that's just how the physics are. Over all, lap times in GT6 were 4-5 seconds quicker around Spa. I'd test around Tsukuba but I don't think the Tsukuba that's been modded by whoever in AC is of high enough quality, at least Spa is fully modeled and laser scanned by Kunos.
I'm going to give the 40/60 WD set up a go now, I reckon that will help match the two games closer together, so that there's less weight on the rear causing more wheel spin in 2nd, and so that the rear isn't swinging around so wildly and easily. Braking without ABS on both is pretty similar, you can feel the bite and lock up much better in AC (a result of the game physics and not the cars), but importantly the actual braking distances and point of lock up is closely matched.
So after the first test, I think CH tyres in GT6 will get the games to perform similar laps times and cornering speeds, but I don't think they'd be anything you could do to match the feeling you have in AC of driving a real car simply because it is much more advanced and has a lot more grunt to pull it off (hardware wise).
Please don't think I am criticizing your replica, by GT6 standards it feels great and you've done a great job, it's GT's physics that are letting it down rather than the car itself. If I drive in GT6 the same way I have to in AC then both feel more similar, it's when you come to pushing lap times that GT exposes it's flaws. I'll give you some more feedback on the other 40/60 WD and will probably try "stock" 43/57 as well.
Good news! It's a new Dacia Sandero!
Ok so I've tried out the 40/60 distribution and also bumped up the rear BB to 6. Did about 15 laps on GT6 and then jumped into AC, increased the tyre pressure but dropped it down to "Green" track settings (about medium grip out of all the options, takes a while for the track to come in). Within 5 laps I was just 5 hundredths off my lap time in GT6.
The 40/60 WD helps to match the AC versions corner entry understeer, tyre slip in 2nd gear and cornering speeds. There were differences here and there, and I also find it harder to get the line right in AC (need to fiddle with controller settings), but over all, the lap times are nearly identical. In GT6 I also had a couple of rear end snapping and off track moments like I did in AC when trying to drive both the same way. GT6's version still has a looser rear end, and it's still easier to regain control, but the behaviour of the car is much closer. Now if only GT had a tyre model, I bet you could get them to react very similar indeed, with the main differences being how the cars feel to drive due to the different physics engines.
I've saved a replay on each game. Driving style and lines will probably look quite different, but the particular lap replays I saved had a mere 0.03 difference.
I tested with the 4.000 final drive, the gearing was pretty much spot on so I didn't fiddle with it. I stuck with CM tyres, increasing the tyre pressure and ambient temp by 2 celsius in AC helped to make the car faster in AC. I tried to drive both the same, I fell behind in GT6 after Eau Rouge because the rear was sliding, but managed to catch up the gap at Bruxelles with a more aggressive exit that only GT6 would allow, from there on, both laps are almost identical, even the gear changes. I tried to keep the upshift time equal in GT6, as the YB in GT6 can upshift instantly, whereas in AC the game simulates this better. Basically I let go of the throttle for the same amount of time that I would in my real life car when "giving it the beans".
Though I agree that adding more camber would have helped adjust the lap time, I think it would have made the car too slippery, GT6 already feels like it's on ice when you've just come from AC, there is so much difference in the feeling even if both cars are doing the same thing. Anyway here's the video, split screen 1080p/60.