I'm looking for the inlet diameter of the OEM turbo on the WRX and STI...

This is all part of our research for possible rules changes for 2008. I figured you Motor Sports guys would know this just as well as anyone else.

Also, what are the inlet diameters for the more "popular" bolt-on turbo upgrades? I'm sure there are tons of upgrades, but there are always typically a handful that are by far, the most popular bolt-on options...

Thanks!

Nikolas

7mm or ~2.4" for the stock VF39/43 on all 04-07 sti's

i think its the same on the WRX's

For our cars, they are not very popular because its a PITA to get to, it also yields a 0 hp increase. Some aftermaket ones need to be used on bigger turbos, mostly they are 3".

Assuming you're going for some type of turbo sizing class like the NHRA, inlet diameter is almost meaningless in this context. The number you really need is INDUCER diameter. This is how the NHRA words it:


1) Turbocharger must be of conventional impeller and housing design and type.
2) Turbocharger is limited to a maximum size of 3.602" (91.49mm) - inducer wheel diameter at the point where the leading edge of the compressor wheel meets the inlet housing.
3) Inlet housing is permitted a maximum inlet diameter of 3.673" (93.29mm) where the leading edge of the compressor wheel meets the housing.
4) All air entering the turbocharger must pass through the turbocharger inlet. Injection of any liquid, gas or any other substance into the inlet or exhaust housing is prohibited. Turbocharger compressor wheel must be constructed of cast or billet aluminum. Exotic material wheels prohibited.

7mm or ~2.4" for the stock VF39/43 on all 04-07 sti's

i think its the same on the WRX's

For our cars, they are not very popular because its a PITA to get to, it also yields a 0 hp increase. Some aftermaket ones need to be used on bigger turbos, mostly they are 3".

7mm != 2.4 inches

2.4" = ~61mm

Alright, I got curious. Near as I can find, the inducer diameter of a TD04L-13T is 40.1mm and the inducer diameter of a VF39 is 48mm.