REALZEUS:
F1 cars still produce more downforce though, even though their drag is very high. That said. they reach unbelievable speeds when they take less wing on due to their mighty engines (in recent years there ha been a drop of power though - back in 2004 in Monza, top speeds were in excess of 370 kph, now they are some 20 kph lower).
The greatest amount of downforce and efficiency (a little less than 5 tons at 200mph with around 800 kg drag, around 5-6 to 1 LD ratio) was seen in sportsprototype championship, especially in IMSA (because of tight tracks and lack of fuel limits) in the end 80's till beginning of 90's. No one is near even today...
370 kph is a great speed, but if you compare it to CART and Sportprototypes from historical point of view it is low. In 2005 BAR HONDA has shown what speed V10 cars can reach - 413 on straight of aeroport without rear wing and less than 400 on salt. Of course these aero specifications are extreme and not useful during the race. In race specs CART record is 413 kph on oval. Sportprototypes records - 405 kph Mulsanne straight, 413 kph Talladega oval, more than 400 kph Fuji.
If we will talk about now, speeds are much much lower. I have seen by telemetry that in SPA AUDI r18 reaches 293 kph, F1 car - 303 kph. AUDI has around 0,65 hp per kilo, F1 car has 1,21. So, even with standard diffuser (regulations) LMP1 has a great efficiency aero. Also, in interview Alan McNish has told that their cars reach the same and even larger amount of DF than F1 cars. The main problem of LMP - weight, 920 kg is too much to compare cars dynamics in corners.
Also, from times you can see that F1 car loses around 8-9 secs on such track as SPA when it is fully loaded by fuel. Diesel LMP1 cars at this moment have around 600 hp (they officially claim around 500, but lets take the higher figure), f1 car has around 750 hp, so with 150 hp difference, much softer tyres compound and more than 150 kg difference between fully loaded f1 car and empty lmp1 the time difference will be 5-6 secs max.
Resume: if the lmp1 car will have the same weight as f1 or even 100 kgs more and the same amount of power as today lmp1 has, lmp1 will have the same pace over 1 lap.
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