Question about air restrictors

[ABP]

I have seen many tables of restrictor diameter sizes and I have a question regarding unrestricted engines:
How big is the diameter of the air flow into the engine in unrestricted engines? If it varies, what are the determining factors? Any actual data is greatly appreciated.

(I am just a math head and would like to... eh... calculate thing)

 

[Furinkazen]

I have seen many tables of restrictor diameter sizes and I have a question regarding unrestricted engines:
How big is the diameter of the air flow into the engine in unrestricted engines? If it varies, what are the determining factors? Any actual data is greatly appreciated.

(I am just a math head and would like to... eh... calculate thing)

Do you mean like this?
http://auto.howstuffworks.com/auto-racing/nascar/nascar-basics/nascar-safety4.htm

 

[ABP]

Yes I do. I'm just wondering because I have read somewhere that WRC-Cars with about 10mm bigger restrictor are capable of 500+ hp.

 

[Carlos]

Yes I do. I'm just wondering because I have read somewhere that WRC-Cars with about 10mm bigger restrictor are capable of 500+ hp.

What kind of era do you mean? Since 2011 for example the Polo R has 33mm restrictor.

Type Straight-four engine with turbocharger and intercooling, transversally mounted in front of the front axle
Displacement 1,600 cc
Power output 232 kW (315 hp) at 6,250 rpm
Torque 425 Nm at 5,000 rpm
Bore / stroke 83,0 mm / 73,8 mm
Air restrictor 33 mm (FIA regulation)
Engine control unit Bosch
Power transmission
Gearbox Sequential, six-speed racing gear box, transversally mounted
Gearbox Final drive Permanent four-wheel drive with fixed drive between the front and rear axles, multi-plate limited-slip differentials, front and rear
Clutch Hydraulically actuated double-disk sintered metal clutch from ZF