So my math says the G40 900 which can flow up to ~80 lbs/min is good for around 600rwhp.

This is the turbo used by Rob in this video making over 700rwhp -
I figure it would need to be flowing around 90+ lbs/min to make 700rwhp.
Am I missing something here 🤔

 

Jumped through a few points, couldn't see brand of dyno, that can make a massive difference to the reading.

The turbo will probably flow that air in overspeed and make that power even on a mainline or dyno dynamics, for how long is another question. Noting on nearly all the modern Garrett turbos it's a max speed line, not a choke line.

 

Good point Slides
I missed that it's not the choke line so rpm could be high enough to go off the chart!

 

Most U.S. dynos read in rwhp/whp but without real-world data like 1/4-mile traps speed, 100–200 km/h, 60–130 mph, etc. the dyno sheet doesn’t mean much, imo.

I had the same issue here in the U.K. with a G35-1050 on a street port at ~20 psi. The dyno guy swore it made 515 rwhp, but Dragy runs showed it was nowhere near that. If it really made 515 rwhp, that’s roughly 600 engine hp, which clearly wasn’t the case.

That’s why I don’t buy the claims of the G40-900 making 700 rwhp on a 13b (maybe piston engine). Omar kindly shared a G40 900 at 24-25psi and the 100-200 was closer to 500rwhp level at 24-25psi.

For reference, Nath’s G42-1200C at ~32 psi made around 630 rwhp on a Bridgeport and his best 100–200 was in the 4.9s on pump fuel with WMI. My G35-1050 27psi setup managed a 5.5s on pump + WMI. I suspect the G40 900 will slot in between these two turbos in terms of real world performance.

700rwhp ~ 800hp is not realistic for a G40-900 on a 13b. I’ve actually got a G40-900 1.19 going on my setup over winter, so I’ll be able to see for myself where it taps out. My guess: it’ll comfortably do a true 500 rwhp and maybe stretch to 600 rwhp max.

 

It didn’t have the restrictive factory UIM and was set to 30 psig boost, but dropped back to 26-27 psig at the top end. Which confirms they were wringing the turbo out for all it was worth. It also has the 8.5:1 rotors, which matters more than some recognize imo …
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Same dyno, same turbo ( different car, one of our v1 cast fd ewg kits). Different tuner. I do think this dyno reads high ( its not a calibration issue, I checked it personally).

This turbo will absolutely make 600rwhp at same boost on other dynos at 29 psi as shown here. 700rwhp usually takes a 67+ mm frame compressor in my experience.

 

STD J607 will always read high.

 

the correction factor (free hp) game has always been one of my pet peeves. i assume that anyone who owns/operates a dyno knows correction factors. simply put if you don't use SAE, you get 3% more power. of course in a world where there is often as much as a 20% diff amongst dynos it is not consequential, but as they say in the courtroom, "it goes to intent."

i have a spread sheet of around 85 dyno runs and they are all corrected to SAE. weird how minds work...

 

"That’s why I don’t buy the claims of the G40-900 making 700 rwhp on a 13b"

count me in with Pat on that. do i believe Garrett or? it is an 80 pound turbo. 600 and pocket change. that said it is my current fav turbo for any dual purpose FD wanting 600 tops. it has a 62 (!!!) inducer. spool city. combine it w Garrett's cutting edge engineering and it is worth the money. Garrett's recent engineering is, of course, being 100% driven by the soon coming to a theatre near you electric turbo for the masses. i am happy to go along for the ride.

 

until somebody pairs the G40-900 up with the 0.85 A/R div T4 housing on a 13B, we haven’t seen the true spool potential yet. The peak 35 lb/min exhaust map rating of the 0.85 is going to be optimum for that low end response in the 550-600 whp range for a 13B …

even that smallest A/R is looser than other 13B turbo turbines with an equivalent whp output range are at; BW 8374 as an example, or how oversized the 1.06 A/R is for it in comparison. Which even your own emap results using the larger -1150 compressor back up. It’s another factor that leads me to believe the possibility of the -900 paired with the 1.06 can be run that far out into overspeed past the indicated 80 lb/min compressor flow map line.
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Also from back in 2021 the Garrett website has an article for the G40-900 with 1.06 A/R turbine housing on a Nissan 370Z 3.0L engine. At 〜3.5 bar boost it supposedly recorded 905 whp on a Dynojet. The compressor map shows 79 lb/min max flow at 3.5 bar (70% compressor eff). That result would also seem to suggest that the turbo was run out past overspeed to get there.