Why is it difficult to find flow for these turbo’s? I want to know mostly out of curiosity. I’m old school and used to guage turbos on known turbo’s i’ve run. Mostly Mitsu stuff like 20g’s, 16G’s, E316G’s for small frame turbos, which by today’s standards on this platform would be considered big. Won’t even mention the large frames I’ve since irrelevant to small turbos which the S280 def is IMO.
I know the 20g flowed 39 lbs/min at peak efficiency, but on track days I’ve run it full closed wastegate and saw 40psi dropping to 28 by redline. Def not recommended, but always kept spares. For us old heads, what would this turbo compare to. 16g? Super60? Have to be over 40 to probably know anything about those turbos. Lol. Thanks for anyone in the know.
In order to make a compressor map like the ones from MHI, you have to run an actual compressor hooked up to an insane high speed motor or forced air turbine blower on a precision flow bench setup at every single operating point on the map in question while measuring inlet/outlet pressure, mass flow and temperature, shaft RPM, etc - basically hundreds of data points, from which the compressor map is then constructed. Big manufacturers like MHI/Garrett/BW can afford to run these tests on mass production turbos.
Aftermarket turbos have all gone to custom designed billet compressor wheels, which while they are designed with industry knowledge and CFD simulations around a few potential operating points, they are not tested like the production turbos are.
But to put some things in context, almost all bolt on Fiesta ST turbos (Whoosh, S280, Pumaspeed, etc) are designed around a Borg Warner (KKK) K04 turbine wheel, the next frame size up from the KP39. The K04 is 44/50mm diameter - slightly smaller even than a T25/28 or TD04 turbine wheel (about halfway between a T22 and T25. Much smaller than any TD05H turbine you’d find on a 16G. The compressor sizes vary much more in size, but the turbine wheel ultimately is limiting exhaust flow.
You can tell some, but not as much information about the compressor wheel diameter, keeping in mind that like in the DSM world, you can get a bit more out of a billet wheel. The S280 is basically designed around a Disco Potato (GT2860RS) compressor housing (but with a better flowing wheel). A standard potato is good for 300-360hp combined with the standard (larger) GT28 turbine, so with a billet wheel and smaller turbine, the S280 comes out in about the same ballpark.
Long story short, even the biggest big turbos we strap to these cars are smaller than the 56mm turbine and 68mm compressor on a “Big/E3” 16G, but that’s pretty normal considering we’re dealing with a smaller 1.6L engine, and a stock standard cast wheel E3/16G can hit 350hp on pump and well over 400 on E85/race gas on a 2.0L engine.
Just remember that wheel diameters put you in the ballpark, but are really broad strokes when it comes to actual flow, especially since various wheels are designed for both different pressure and flow operating points.
The main advantage of billet wheels is not so much that they inherently flow more than cast wheels - it’s more that you can tweak the blade design to move the most efficient operating points (efficiency island) to higher pressure and flow points than the original compressors were designed for.
