Last night I pulled up some logs in LogAnal and noticed immediately that I, too, had run much faster laps with the longer gears. I was surprised. I thought I had better control with the shorter gears. Obviously, it was really just a case of me running granny laps so of course I felt like I had more control.
Well with extra shifts in a slow gearbox you're probably looking at 0.15 - 0.25s each, so if you lost half of that in actual time you'd be losing about 0.3 - 0.5s per lap give or take. These engines did have wide torque bands so it's feasible that you could be losing time from five gears over four in specific circumstances; after all the 7 speed gearbox was introduced by Ferrari in 1991 IIRC to compensate for their V12 engine's crap torque band. That said it probably has more to do with minimising wheelspin as you're spending less time in the most punchy range of the engine. God knows I extend the gears on that monstrous FRenault 3.5 engine to stop it spinning up the tires in 3rd and 4th gear.
It doesn't surprise me at all that drivers are going faster with taller gears as you are likely concentrating more on your driving and getting the most out of the power and hitting apexes just right instead of being lulled into a false sense of speed just because you can spin the tires at will...
Yup, I've been wanting to mention that about the ISIengine for many, many years now. I notice it a ton in ISIengine games since the very early 2000s. It's almost easier to drive and control cars with very short and crazy torquey/powerful gears since, with longer gears, once the tyres start slipping then they'll easily keep spinning more and more to way higher speeds. This also has a second effect in making short shifting not as useful as it should (unless the short shift induces a ton of understeer which forces you to stay off the power anyways). It's as if, once the slightest amount of wheelspin occurs, the tyres aren't even touching the ground or something - they want to spin up more and more extremely, extremely easily as if the car suddenly gained 10,000 lb/ft of torque and/or as if the tyres are raised off the ground pr something. Not to mention, while in that slipping state, it's also unrealistically difficult and/or just "odd" to modulate the wheelspin and slide relative to real-life as-well as Live For Speed, Netkar Pro, and Driver's Republic (alpha).
I don't see a problem in the engine. This effect is pretty normal because of static friction. You need a lot more toque to overcome the static friction than you need to keep it sliding. Maybe this is exaggerated in rF2 but the effect per se is not unrealistic.
Once they start sliding, the surface temp goes up, which reduces the grip, which causes more sliding, etc.
