Hi Ruben
If the difference between your average laptime over 5min and your fastest laptime is 0.3 - 0.4 sec, that is very good ! (I'm not sure if you meant that though!)
I'm pleased if I get around 0.7 sec difference, but the best drivers are generally all below 0.5sec. Aim for consistency first, rather than fast lap times, the overall result is always poorer when you try too hard
On a practice day, I sometimes pick a corner, or series of corners, and concentrate on keeping the same speed, same line, braking points and so on. See if you can string 5 - 10 laps together exactly the same, and then pick another series of corners. Another idea that worked for me was to forget about my place in the club championship rankings or trying to win individual races, but just settled on driving slightly slower, but with maximum consistency - my driving improved a lot, and guess what - my overall results improved, simply because I was not crashing so much.
Once you stop crashing, you need to focus on positioning the car with accuracy. I am always impressed with top drivers like Andy Moore or Ollie Jeffries here in the UK - they position their car within 25mm at the corner apex, lap after lap. Once you can position your car accurately, then you need to follow the best racing lines, and get more "aggressive" with throttle and braking. A race car should ideally be always on the limit of the available frictional grip when cornering, braking or accelerating.
In terms of car setup, don't go for a very aggressive or responsive setup initially as it may be too twitchy and hard to drive, so, go for softer springs, lighter oil and so on (within reason!). As previous poster's mention, the "kit" setup is the normal starting place, and if you end up with VERY different settings, it usually means you've got "lost" in setting up, so go back to the base kit setup, and make small changes one by one, testing after each change. You can usually tell the car's behaviour quite quickly, after only a couple of laps (even if the tyres are cool). Once you have a setup that works, you do need to do a timed 5min run and check your laptimes.
It has sometimes been said that a setup that is easy to drive can be slow, and a twitchy responsive setup hard-to-drive one is fast - laptimes are the only judge ! I have found that mild understeer ("push") feels OK to drive, but is slow, and can be hard to diagnose - get an experienced racer to look at your car (or drive it) and give you some tips.
Hope this helps !
