it’s called inefficiency, and in a 9180 it starts kicking in at at about 90 lb/min, so low 700 whp is banging on that wall pretty good

https://cimg3.ibsrv.net/gimg/www.rx7...e5e03faec.jpeg



a 9280 will get you some more, but less than 800 whp unless you want to really crank up the boost, but more than likely to run out of flow/overspeed …


https://cimg1.ibsrv.net/gimg/www.rx7...ecc0b7fe1.jpeg



you should probably be looking at a Garrett G42 instead or possibly a Garrett G40-1150 depending on your goal …
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^^ can’t edit that, but at the end the alternative should have been G42-1200C, or possibly the G42-1450, not G40-1150. Also a G45-1500.

Carrying over from some back scene discussions, he already has the EFR9280 and I hadn’t really looked at these larger sizes much, but pulled some estimates together for it

It looks like the 80mm 1.45 A/R housing peaks at about 36 lb/min turbine flow and on a 20B the 9280 in theory stalls out at 7500 rpm with about 101 lb/min compressor flow at 30 psi boost and 35 psi emap. That’s making numerous estimates and assumptions, but the thing that impressed on me was down at 3000 rpm it was already well up on the turbine flow curve. This would suggest it’s going to be very punchy down low, likely even capable of surging with too much boost too early. Which then also suggests it’s a bit undersized for top end flow on a 20B.

So then looking at a Garrett G42-1200C, the 1.01 housing is capable of 43 lb/min flow and should support the 110 lb/min compressor limit at 3 bar seeing as how it’s still over 70% efficient there. That’s right at the overspeed limit though, so it better have the speed sensor and overspeed software safety programming in place. It will likely lack the low end punch of the EFR, but be quite exciting otherwise. :suspect:
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