Hi guys. Back in the RX7 game after a decade long hiatus.

Looking to upgrade the twins on my new RX7. My last GT35 car/setup went 11.1@126 26psi on pump gas/water-injection but that engine didnt last too long. This was on the first try at the strip, then they kicked me off for no cage. Looking for lower boost and more reliability. This is a street/strip car.

Short term goal is 11.5s (425ish whp) for a year or so.
Long term goal is 10.5s (550ish? Whp) in the future.

Since im on 92 octane plus meth injection (no E85 here in Hawaii), can this be done with an 8374 IWG? Or do I need a 9180 IWG? Want to max at 22psi boost due to fuel type.

Stock ports (not porting unless it blows)
turblown UIM
3in full open exhaust
ign1a ignition
Vmount intercooler
Drag radials nitto555r2


Thanks

 

The short runner manifold will help a bit but if you aren't using evaporative cooling to increase charge with heavy ethanol or methanol fuel mix I think you will struggle at that boost without porting unless you strip weight and have perfect gearing.

 

Definitely go with the larger 9180 turbo. Might want to go up to 3.5" for exhaust also. On 92 gas the realistic limit for 8374 is around 400whp.

 

a very interesting question from so many aspects.

turbo choice
fuel
ports

first off, BIG congrats on being almost in the 10s w a dual purpose FD. unless you wanted to stuff a huge frame GT42 in your engine bay the GT3582r was the weapon of choice. it was way ahead of anything available for a long time. Podiums 2000, 2001, 2002 LeMans.

here's a compressor map from the first GT35:



looks like around 60 pounds.... 450. newsflash, Garrett is still in business. i suggest your title should be more generalized rather than which BW turbo.

take a look at the 2025 GT3582R... renamed as the G35-1050



60 V 100 pounds of air from the same sized frame? yes, Garrett is still making turbos. my money is on Garrett because they are in the lead for the (electric) turbo revolution so they put their money on the table (OE type money) for serious aero research. and it shows.

gross flow of course is only part of the picture. DENSITY is the giraffe in the room as expressed on the chart as efficiency. we are simply talking temperature. it is all about how many oxygen molecules are entering the motor. the cooler the intake air the more oxygen to burn and make power.

it is all about "EFFICIENCY."

so let's take a look....

17 psi 400/53 pounds, 20 psi, 500/67 pounds and 20 psi 600/80 pounds hp (Dynojet power)

here's the turbo everyone owns, the EFR8374



Garrett G35-1050


EFR 9180


Garrett G40-1150



PERCENT EFFICIENCY


.........................400..............500..... .......600

EFR8374...........74.................63........... .N/A

G35-1050..........78.................78..............73

EFR9180...........76.................70........... ...60

G40-1150..........77..................78..............77

advantage Garrett

i measure air temperature between the compressor and the intercooler. 4 times a second, accuracy at 99%+. typical logged temps have ranged for 230 F to 450 F! gasoline autoignites around 450. a very good intercooler removes up to 65% of the difference between the temp out of the compressor and ambient. ambient being the temp at your air filter, not outside air.

doing the math... at say 20 psi boost... about 340... ambient 125. 215 is the rise due to compression within the turbo X .65 = 140 removed.

340 - 140 = 200 F into your motor but your IAT measured w a "fast" thermistor reads 75????


here's a Power FC log from a 20 psi/500 hp dyno run i did in 2006. the same 96 F from 2400 to 6800? the following month i said goodby to my thermistor and added a proper air thermocouple. but you have a "fast" thermocouple. like having a fast turtle. if you are making 500 your air temps are above 300. your IC removes 65% of the rise... your real air temps are much closer to 200 than 100. BTW, if you use straight meth as AI you can remove between 45 and 60 F.

just to put a period on fast thermistors i added one to my Turblown UIM along side my thermocouple and logged both outputs. on 600 hp runs it the thermistor temp barely moved, staying around 70/80. the thermocouple initially moved upwards with the compressor output temp and then around 9 psi dropped with the onset of the meth AI... to end up around where the thermistor was plodding along.

as we appreciate the dynamic rise in turbo charge air temps, and the fact that our real IATs actually are a potential problem, turbo efficiency becomes an important consideration.

"but EFR turbos have a 40% lighter turbine wheel so they spool really fast...."

so said Mr. Marketing.

let's take a closer look.

Titanium Aluminide is 40% lighter than inconel. therefore...

how about the fact that at higher temps Ti-Al isn't as strong so you need MORE of it.

when i switched from my EFR9180 to my G40-1150 i had them both on the bench and compared hot wheels. WOW

notice the additional mass BW had to put at the bottom of the vanes to provide support...

compare to the Garrett hotside... beautiful



additional Garrett positive factors:

EFR has a thicker hub. hubs do nothing, vanes do the work
Garrett vanes are thinner and have a more sophisticated shape
(Dan Barlog, the brains behind Precision Turbo responded w "we picked flow over weight" when i asked him about Titanium-Aluminide. they couldn't properly shape it and retain needed hi temp strength)

FUEL

you live in California i believe... where you see mostly 91 octane. did you know there is approx the same amount of energy content in 91 as 93? yes, as you know, 93 has more knock resistance so it is challenging/risky to run at higher flow levels. there is an easy fix. 100% methanol AI. delivered at around 1000 cc/min it will turn your 91 into rocket fuel. i have run 100% meth since 2006. i recommend an Alkycontrol setup with ProMeth nozzles..

PORTS

not an easy fix. the Primary port is the Primary problem.... so much can be gained by giving it attention.. please see my section as to further info..

PORT TECH

you will be making the turbo work harder thru the stock ports so your compressor temps will be higher

 

Thanks! That was almost 20 years ago too.

The main reason I'm looking at the BW turbos vs Garretts is because of the cost, and secondarily, the simplicity. The garrets are clearly better as you have explained. The BWs come with IWGs and boost control. The Garrett plus those features will cost about $1500 more. I have 4 young kids now so trying to keep the costs down while still achieving my goals for the car.

In this scenario, would you agree that the 9180 is the overall best choice? It seems so.

Im in Hawaii on 92 octane. While I can still get meth, that's not exactly easy as well. Im on 350ccs now and it blows through the meth/water tank fast. My typical IAT at 15psi twins are in the mid 30Cs with the stock IAT.

Im also concerned about 100% meth due to fire hazard as I've had an engine catch on fire before. Maybe this concern is overblown though. This was not due to meth line popping off but a shitty turbo blanket.

I would think 1000cc of 50/50 water/meth ar 22psi would be ok for my needs and situation? I on a snow stage 1 kit that I just bought and it can run 50% max methanol so I have to work around this.

Pretty confident I can run 10s with the 9180 as my tuning knowledge has improved significantly over the years.

What would spool rpm look like on a 9180 stock ports?

Thanks!

 

Great info Howard! I'm considering a G40-1150 for a semipp 13B .
You didn't mention in your post turbine flow for the comparisons...
The G35 has a small turbine size compared to the others, although the designs are different but I'm sure this is important for a rotary with regards to exhaust back pressure and egt's.