To throw another couple of pennies into the opinions pot here are some observations from me.
It's never "just" the car, it's always a combination of things such as driver + car + track. For example after the Rome race I hopped into a couple of different cars, some that were on the list and some that weren't but were still 90s Japanese, during that race I averaged 1'15 to 1'17 for lap times with (once I figured out how to drive) some mid 1'14 "fast" laps. I tried the MR2 and NSX Type S Zero (and the Nissan Silvia K's Aero (S14) '93, a light FR car) but the results were not much different, I wasn't magically faster and in fact ran very similar times to the 300ZX I used in the race.
The big difference on that track I found between race and post race alternate cars was the tire wear, given the relatively twisty nature of Rome the heavier cars (300ZX around 1500kg) used tires much more quickly than the lighter cars (around 1200kg). However that doesn't always hold true on every track, think back to Daytona Road, if I remember right my tires wore similarly with Ex's (Me in the 300ZX, him in an NSX I think) and the final result came down to pitstops.
Also La Sarthe is another example worth noting, a few cars had better top end than others when it came to the straight so in open air they had the advantage however if another car could stick close enough to use the draft then the advantage went away. Working examples again were myself in the 300ZX dogging Ex in the NSX for the first 5 or so laps, we lost eachother in pitstops but I picked up Turbo's coat tails I think (it was an S2000 I followed) and basically so long as I kept in draft range on the straight bits both cars were pretty even and it resulted in some great racing action.
Some cars are also better with more tuning than they are in a series like this, great example of that is the Mitsubishi GTO / 3000GT. I love the car with some weight reduction and other things done to it, but at the specs for this series I found it to be a bit too unwieldy which was a shame. Also I find I'm mediocre in MR cars generally speaking but others are much better at driving them.
Anyway, I'm not sure now where I was going with this post
, my train of thought pulled into a siding a number of times and I think has finally gotten derailed so I'm going to stop rambling
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