In racing, turbo compressors wheel sizes are typically referred to by their minor diameter (the smallest diameter of the fins) as that largely dictates the maximum power the compressor can make.

Manufacturers themselves dont follow any naming rules.

Borg Warner EFR turbos are named after the major diameter of the compressor wheel followerd by the major diameter of the exhaust wheel. Example EFR 9180.

Garret GT turbos were named by the frame size/family of exhaust wheel followed by their compressor major diameter ending with an R if it was ball bearing. Example GT3582R

G series turbos use the frame size/family of exhaust wheel followed by max piston HP they recommend running on it. Example G35-900.

 

Spinny thing go Pshhhhhhhhh!


There is no G35 turbo. There is a G35 series of turbos. There are G35-660 variants, G35-770 variants, G35-900 variants.

 

turbo nomenclature has always been confusing as been referenced above. this is partially because there hasn't been a constancy as to referencing the dimensions.

each wheel, compressor and turbine, has two different diameters. the compressor has a smaller diameter on the intake side and a larger diameter on the outflow side. the turbine also has differing diameters, also having the smaller diameter facing the inflow from the motor and the larger diameter handling the outflow.

it has not been settled as to which of the dimensions should be referenced when referring to a particular turbo and this has caused lots of initial confusion. lousy marketing. i had a lengthy discussion w Dan Sussna, at the time CEO of Garrett, about this. IMO a need to simplify nomenclature so the market could sort thru all the GT3582 morass.

Garrett got it done w the group tag, say G40, and then the flow, say 1150. the market, which is of course piston, knows you take the 1150 and divide it by ten to get max power. easy. Borg Warner hasn't yet put on it's marketing hat. EFR8374 huh?

attempting to find an understandable means of comparison i have taken the diameter of each wheel, solved for the area. since there is a smaller and larger diameter on each wheel i add them and divide by two. we now have an average area for each wheel.

while other factors enter, such as wheel height and shape, these numbers provide a worthwhile starting point to compare turbo options.

while size matters, another often overlooked factor is Trim. trim is expressed as, a number such as 54 or 64. it is the relationship between the areas of the inflow diameter to the outflow. if trim is in the low 50s the wheel favors early spool. if it is the 60s it favors top end.

for all the turbos numbers see my thread: Turbo Comparisons

https://www.rx7club.com/single-turbo...st-one-869614/

 

Thanks very insightful! hahah!
Should have clarified, I meant the G35-1050. I thought the 68mm compressor size would have given it away but I appreciate there are other variants.

 

Thanks Howard, I've found your turbo thread very helpful to compare the compressor and turbine side.
I should have clarified earlier, I do like how precision turbos address their turbo sizing which makes complex turbo nomenclature clear for a turbo noob like me. Correct me if I'm wrong here but the 6870, means they are referring to the compressor as 68mm and the turbine is 70mm? That's what I was trying to get at earlier but got confusing real quick as you've mentioned above as the compressor & turbine have two sizes.

 

That's how precision work, inducer on intake and exducer on exhaust. It's probably most sensible in cases where racing classes are determined by inducer diameter, it generally correlates best with power potential too as regardless of any compressor aero design advances you can't surpass choke flow for that orifice/venturi/restrictor size factoring some variance in trumpet/taper constraints down to that size.


Physical packaging is a bit different, frame size kind of gets there but it's not like any of them are based on a square or I guess golden ratio w/l box in inches which might be beneficial.

 

Have decided to go with the G40-1150 with 1.19ar. Hoping the T4 Twin scroll & dual wastegate get it on boost quick enough.

Will keep you updated on the progress.

 

it’s a safe choice if your engine configuration is similar, but honestly there’s so much incorrect or bad information in this thread it’s a miracle anyone asking the question can figure anything out

his result posted at the beginning of the thread is closer to 725 - 750 whp here on USA dynos. Which is not really a fair comparison to make against the G42-1450 it was paired with on the dyno sheet. That’s a 850 - 1000 whp range compressor on a rotary engine with the appropriate turbine housing choice. The G42-1200 or -1200C might have fared better.

He likely also mistakenly stated 1.06 A/R as well since moving past face value of the posting, there isn’t one offered anywhere for a G42 that I can find. It most likely was the 1.01 A/R (1.15 & 1.28 are the others offered) which would put it about equal on turbine flow potential to the G40 1.19 AR.

So the appropriate comparison or consideration would be the G40-1150 1.19 vs the G42-1200 1.01.
.

 

I went with the PSR 7170G which is a copy of the G40-1150.
Omar from Raceonly recommends the psr 6270g / g40-900 for 500whp.

 

Who knew it would be so hard to find a workshop in Sydney to do the work though!

If anyone has any Rotary specialists in Sydney they can recommend that'd be great.

 

So what would you guys recommend for a halfbridged engine with bigger exhaust ports aiming for 500-550 hp? using it for the track (grip) mostly. was thinking about g40 or g42 compact but can't decide on the trims

 

Dear friend. I am looking to move a step further upgrading from my gt 4088 to psr 7170g too. Can you share the results of psr7170g? What is your opinion? Laggy for street use? whp numbers at 15 - 18 psi boost?

 

I haven't dynoed by car yet but I'm at 1.5 bar boost by 4500rpm I believe.

The psr g series turbos are great for the price. I have two rx7s one is with a 6270g .96 which is a street port rx7 the other is a half bridge rx7 with a 7170g 1.06.

The t51r mod sounds sweet too!