TURBOCHARGER TECHNOLOGY /ROTARY
Think of the Garrett GT3582r as the Motorola mobile phone and the GTX3582r as the Apple I 10... While it is easy to pick out the current phone, as you can see turbos pose a bigger challenge. The 2019 vintage has matching exterior dimensions, same size turbine wheel and housing, and a TWO PERCENT larger compressor wheel...
As well as 20 years of additional engineering.
The result is that one makes 467 rotary rwhp and the other 618. That'd be 32% more from virtually the same frame.
Unlike the phones, turbos look similar. Make the wrong choice and you might be bolting on the Motorola rather than the iPhone.
Fortunately there is ample data, as well as options, from the manufacturers so your selection can fit like a custom tailored suit.
Proper turbo selection for a rotary is both difficult and rewarding. It starts with deciding how you want to use your FD and what you want out of it.
When you are thinking about your power target please do not confuse Mustang/Camaro power levels with vehicular performance. They are dragging around another one thousand pounds!
This is the genius of Mazda, i think of the company as the Asian counterpart to Colin Chapman's Lotus. Light weight pays dividends any time the engine is running... faster corner speeds, better deceleration and of course acceleration and the FD weighs in at 2862 compared to the fatties around 3900 pounds or more.
2862 is the key
As we look at the long list of available turbos in 2019, many offering more than 600 rwhp, remember there is a significant cost as you move above supercar territory. For instance, the clutch package... The rotary is a small engine and, as such, it has a small flywheel with a small frictional surface. There is no magic with regard to clutches. It is the amount of frictional surface (and the rotary is small), the coefficient of friction of the mating surfaces and the spring pressure. All working against driveability as additional clamp is needed. I promise you that if you buy too stiff a clutch you will soon HATE driving your RX7. The answer is an Exedy double disc unit and the price tag is right around $1400. If you are making over 500 you will need it as it offers ample clamp, and unlike higher pressure single disc clutches is happy in traffic and can be feathered on takeup.
A proper 600 rwhp build should entail replacing or modifying virtually everything on the powertrain and chassis. The transmission was designed for 184 foot pounds of rear wheel torque. The typical 600 rwhp rotary makes 500 foot pounds of torque, almost three times that number. I run a Tremec 6 speed T56. The spider gears in the Torsen limited slip are fragile and take out the entire gear case when they fail. i run a plate type LSD. The key consideration for a 550/600 rwhp FD is that the mod process never ends.
It is worth considering that a 450 rwhp FD will run with virtually anything and is happy with a driveable single plate clutch, stock transmission and Torsen LSD. etc, etc, etc...
It is so easy to buy a bigger turbo than you need... they are generally about the same price... until you later realize that you need another $10,000 of mods.
Keep in mind that you can beat a Hellcat Redeye in a straight line with 450 rwhp;)
Please do not take this as discouragement from deciding on the 600 option, just a bit of reality.
O K, enough of that and on to turbos viewed from a rotary perspective...
One of the key marketing points has been that Titanium Aluminide is 40% lighter than inconel. A fair point however because the material is not as strong as inconel when heated to the 1700 F area certain structural issues arise which may reduce the weight advantage. Notice the material at the base of the fins on the Borg Warner. This material provides added support to the vanes as does the thicker hub. Compare to the Garrett. BW's material may be 40% lighter but more material is needed to bolster the tensile strength.
Further, the vanes are thinner on the Garrett. I asked Dan Barlog, head engineer for Precision Turbos, if he had evaluated Titanium Aluminide. "We picked flow over weight" was his answer. Precision was unable to get the vane shape they wanted.
Again, all actually very interesting but how does it net out for me? i am glad you asked as i now have the answer.
Awesome.
I generally equate 20 psi boost with approximately 500 rw (Dynojet) hp. This worked with a number of Borg Warner SX-E turbos. My Borg Warner EFR 9180 was around 525. A few days ago i did a run to 8008 RPM in third at 21 psi with my G40-1150. 611 rwhp. The run was interrupted at 8008 when the rear end started going sideways.
Flow going into the motor at sea level is 14.7 plus gauge pressure so 20 psi boost is 34.7 into the motor. 21 boost is 35.7 actual or 2.9% more air. Correcting the 9180 at 20 psi boost to 21 we get 540. The G40-1150 produced 611 or 13% more power at similar boost.
But the positive dynamics don't end with more power. I have logged exhaust backpressure since 2013. EMAP is a big deal as it works against the motor and also pollutes the incoming charge air.
For sure, numerous factors effect the level of backpressure. Two key items are the shape of the exhaust port and the turbo manifold. Most in the know run similar exhaust ports, early open, no changes to the width or close. The turbo manifold is a BIG deal and I am quite happy with my CPR design. (see "The Why of System Design Section" for details). While both manifold and ports are important, since they were unchanged in my turbo comparo, it is clearly the turbo that is isolated.
Exhaust backpressure starts out at less than boost and then rises with RPM. At a point, backpressure equals boost. This point is "crossover" and it provides an easy way to compare exhaust pressure dynamics. My EFR 9180 crossover on a 20 psi run was 5955. My G40- crossed over at 6544! WOW.
It is important to appreciate how significant this is as to promoting rotary engine health. Less exhaust into the intake charge... further pushing the knock threshold away.
More flow at less boost.
All a great/interesting story but what does that have to do with me and my FD you say. I say you can bolt that same level of technology onto your FD motor.
I did.
Currently Garrett has about 5% of the FD single turbo market.
That 5% is mostly GT3582rs from yesteryear. Borg Warner owns the single turbo FD market currently. The culprit is marketing rather than product. As a person that may have spent too much time nosing into turbos I can tell you that there has always been lots of skepticism in the rotary community, myself included, regarding Garrett's predilection for "small" turbines. Garrett compressor maps, in the last 10 years, have always been boffo but they were hooked up to smallish turbine wheels. The rotary community knows that it takes around 30% more exhaust flow to make equivalent piston power... placing significant focus on the hotside. Not many peeps in the rotary community wanted to step up and be the guinea pig.
"Small" relates to comparing the relative diameters of the hot and cold side wheels. For we plebians, lacking aero tools and parallel processing computers in our garages wheel diameters has been the tool of choice. Certainly this is a reasonable initial place to start. However, it appears, that the 21st century has trumped the ruler.
And here, Honeywell enters the Garrett picture. Honeywell bought Garrett Turbosystems in 2004. Honeywell annual revenues in 2004 were $25 Billion dollars. Garrett was tucked into the Aerospace Division. 2000 Engineers. Garrett chose Daniel Sussna from that division to head up Garrett. Daniel told me he had all 2000 engineers in his rolodex as well as Honeywell's Aerospace Division hardware/software...
And it shows when you look closely at Garrett's recent products. Fueled by the promise of the mainstreaming of OE E Turbo business mega dollars, Garrett aggressively leveraged Honeywell's capabilities and the motorsports market is the early beneficiary.
A couple of years ago i decided to swap my Borg Warner EFR 9180 for a Garrett G40-1150. The initial reason was that BW, out of the blue, decided 1765 F was the temp limit of their Titanium Aluminide turbine wheel. For those running on ethanol, not a problem. Gasoline in the 500+ area could be a problem. I liked my 9180's dynamic spool but did trade it for a Garrett G40-1150. And a heavier "smaller" turbine wheel.
EFR 9180 compressor wheel average diameter: 7.84 square inches
EFR 9180 turbine wheel average diameter 7.189 square inches
G40-1150 compressor wheel average diameter: 7.76 square inches
G40-1150 turbine wheel average diameter: 6.58 square inches
My new turbo had a 9% smaller area turbine wheel and the hotside wheel average area was only 85% of the compressor while the EFR 9180 hotside was 92% of the cold side wheel.
Maybe a bad trade?
Or maybe Garrett and Honeywell knew what they were doing.
Things became very interesting when i had both turbos on my table with the hotside housings off.
Turbos are more difficult to analyze, for instance here are two..
The Borg Warner hub is thicker (.965 V .87) than the Garrett. Hubs, of course, are subtractive as to output. Vanes do the work. Fully half of the diameter difference is lost with the larger hub.
Garrett also gains additional working area by having the vanes .2 of an inch taller (axial).
The other measuring stick as to backpressure is the amount at the end of the pull. It is not uncommon to see close to double the boost, I E 40 psi back pressure at 20 psi boost. According to Borg Warner it takes around 100 horsepower to drive the turbo around the 500 hp area so there's a lot of pressure between the combustion chamber and the turbine wheel. At the end of my run my boost was 22.0 and back pressure was 30.2 or 37% more than boost. Comparative EFR 9180 numbers were around 50%.
Power is all about airflow and airflow is commonly measured in pounds per minute. BorgWarner and Garrett generally offer compressor maps for each of their turbos and from them we can zero in on a turbo to fit
our power objective.
It isn't as simple as reading the sales brochure as the horsepower number is for piston engines. Reaching the rotary number is simply a matter of multiplying the number by .75. In other words if you see a turbo rated at "600" you simply multiply 600 by .75 and find it will make 450 rear wheel rotary. (While it is true that the rotary isn't as efficient as a piston engine at converting a set amount of air to power the rotary is capable of flowing lots more air than a piston motor so it more than makes up for its combustive inefficiency with additional flow.)
The estimated power numbers offered by turbo vendors are based on airflow which is commonly expressed as pounds per minute. Compressor maps provide the data.
Now that i have your attention let's talk turbos. SO what the heck is a picture of the "Pass Time" babe Paige Simpson doing here? If you are a car guy you probably remember watching the cable drag racing show a few years ago. You probably remember Paige who did the serious staging work.
What jumped out at me, and it wasn't particularly a surprise, was the unending procession of supposedly daily drivers with huge cams that would hardly idle and all the 11 second time slips from these beasts. Every now and then a fox body Mustang would appear. Initially you almost wonder what the hell is this doing here as you could barely hear it at idle. And what were the two funny looking holes in the front fascia for? The light turns green and the E T is... 7.70!
Turbos are game changers.
Normally aspirated engines are charged with air. 14.7 psi at sea level. All the cam timing in the world can't change that. Engines make power by burning oxygen molecules. More oxygen, more power and no automotive motor breathes like a rotary. Combine a turbo and a rotary and you have something very special powerwise.
The rotary power key is the peripheral 50 mm exhaust port. No valve in the way and zero bends in the runner. A straight shot from the combustion to the turbine wheel. Fully developed, this 184 pound shortblock, measuring 13 X 13 inches can make well over 1000 rwhp on methanol.
We aren't going to go there. Coleman Precision Rotaries is all about dual purpose with an interest in longevity and approximately 600 as a max target. Another reason not to go there (over 600) is that you don't have to in order to put them in your rear view mirror as the FD weighs just under ONE THOUSAND pounds less than the competition.
RX7 2862 pounds
2019 Camaro LT1 3863
2019 Mustang GT 350 3805
2019 Dodge Challenger Hellcat 4448 yikes what a boat
Let's get to the bottom line, rear wheel horsepower to weight, to see what it will take to beat these 2019 beasts:
2019 Camaro LT1 8.23 pounds per rear wheel horsepower
2019 Mustang GT 350 8.5
2019 Hellcat Redeye (797 hp) 6.57
RX7 450 rwhp 6.36
Yes, you can beat a 2019 top of the line Hellcat Redeye with your 450 rwhp RX7! And should the road have a few bends the over two tons of lard will be shrinking at a very fast rate in your rear view mirror.
It isn't difficult to figure out which of these two mobile phones is where on the development tree...
Clearing away the cobwebs it looks like around 65 pounds of air from the first GT3582r.... good for 490 rotary rwhp. Still impressive for such a diminutive package.
Now take a good look at Garrett's uprated version, the G35-900... still in the same small physical package...
The BorgWarner S300 SXE 62 is one of my favorite turbos for the dual purpose rotary. Note that BW estimates max power at 775 which is the typical 10 times max pounds per minute of air found at the most eastward plot. Since this is piston power we need to adjust it to rotary. We simply multiply 775 by .75 to get rotary power. 775 X .75 = 581. While this is a bit over the recommended 450/500 dual purpose objective a bit of overhead is good so the turbo isn't working too hard.
"Working too hard" as in starting to overheat the charge airflow. Note the decreasing distance between the efficiency contours as the flow heads eastward to maximum. The efficiency contours are really BIG factors as to power.
This "efficiency" concept might be best understood by considering the RX7 stock twin setup. The stock turbos were designed to run around 10 psi. Since we are all prone to tweak things looking for more power the tweaking began... less restrictive exhaust upped the boost, restrictive pills in the wastegate control system upped the boost. And as we watched our boost rise lots of happy faces until we very quickly reached a point where boost was high and power... rapidly started heading south.
Push the compressor wheel to the point where it loses grip on the air and slippage occurs. Rub your hands together and very soon they get HOT. Friction/slippage is EVIL simply because it creates HEAT and HEAT is the ultimate villain as heat causes the oxygen molecules to vibrate. When they vibrate they take up more space. More space means less molecules to burn and make power. A typical turbo on a rotary around 20 psi boost/500 rwhp outputs charge air just over 300 F. If a turbo is run into the inefficiency areas the air could be 350 F or more. You don't want to select a turbo that will need to be run into the inefficiency zone to make your desired power level.
One of the really neat things about the BW SXE 62 is how wide the efficiency zones are... airflow is important but cooler airflow is God.
Especially for the rotary.
Cooler/denser air makes more power
Cooler/denser air is less prone to detonation/knock.
I recall looking at my Intake Air Temperature (IAT) log from a dyno run around 500 hp back in 2008. It showed 27 C from 2000 to 9000 RPM. Of course the problem was the IAT sensor. OE IAT sensors are designed to function much like a choke on a carburetor. Glacial speed when you need warp speed if you wish to understand true IAT.
Since one of my my primary interests is efficient system design i needed to get real time data. The answer was a Type K Thermocouple similar to what you may be using to monitor EGTs. There is an "air" thermocouple that reads air temperature:
four readings per second
+/- .4 tenths of one percent error over the entire range. That would be total max error of 2.4 F at 300 degrees
(details found in the Tuning/ Hardware Section)
It is all about cool dense air into the motor... and the process is sequential.
It starts with air temp into the air filter. If your filter is anywhere near your intercooler/radiator you are in big trouble. Even if it isn't, you are sucking engine bay air starting around 150 F! A PTP Lava Turbo Blanket and wrapped downpipe will remove 20 degrees. Turbo selection is next... you want to be running in an efficient zone on the compressor map so the charge air out of the turbo is as low as possible. The intercooler needs to be efficient. I favor the stock location Pettit Coolcharge 3 over the front mount/V mount as it retains the stock (excellently located) radiator, doesn't clog up the engine compartment and drops IAT 130 F. ( see System Design Section). The essential AI system also helps a great deal. I use 100% methanol as injectant as it takes easily 50 F out of the charge air. Water does not lower charge air temps.
Let's now survey the 2019 turbo options. Given my power range interest i am going to exclude some of the smaller and larger turbos and focus on the 400/600 range. This of course includes that make more than 600 as we don't want to run the turbos at max output as they would be out of efficient ranges.
There are numerous companies offering turbos. I am going to focus on turbos from three companies.
BORG WARNER
BorgWarner is a 10 Billion dollar annual revenue American-headquartered global automotive company with deep roots back to the inception of the automobile. One of the most iconic and prestigious motor racing trophies, the Borg Warner Indianapolis 500 Trophy, has been handed out with the quart of milk since 1936. Borg Warner EFR turbos currently power every Indycar.
BorgWarner is a major factor in the OE turbo market. Ford's Ecoboost V6 features BW EFR turbos and is one of the world's largest passenger car turbo applications.
BorgWarner has probably invested the greatest amount of resources into turbocharger development of any corporation. Not only are the current end products reflective of this effort from an output aspect but they also benefit from the fact that they have to measure up to lofty OE standards from durability/longevity and safety.
BorgWarner offers two distinct lines of turbos:
EFR (Engineered For Racing)
Airwerks S 300 Series SX-E
Engineered For Racing
The EFR line started with a clean sheet of paper and is perhaps the most aggressively engineered OE accepted turbo available. Literally every component of the turbo is worthy of comment so i will keep it brief. If you are interested in all aspects of the EFR line i highly recommend the BW 120 page manual. Don't be put off by the length as there are lots of pictures and big print. An easy and enlightening read for those with interest.
BW Training manual http://www.turbos.borgwarner.com/files/pdf/efr_turbo_technical_brief.pdf
While it is hard to pick the most amazing aspects of the EFR line, the turbine wheel must lead the list. Turbine wheels are HEAVY as they are made from heat resistant Inconel. The EFR wheels are made of Titanium Aluminide and are approximately 40% lighter! All EFR turbos have a dynamic spool advantage over most other turbos due to the lighter hotside wheel.
Another impressive aspect is the ceramic ball bearing assembly. Ball bearing turbos came on the scene just before 2000. Most of us remember the Garrett GT35, GT42 that featured steel ball bearings. BorgWarner elected to go with ceramic ball bearings, retained in a metal casing. The bearings are also spaced wide apart and are flanked by double O rings.
Gorgeous
The Precision GEN 2 turbos are awesome.
i spent a day touring their facilities hosted by Dan Barlog, Chief Engineer and was very impressed. Precision started 30 years ago and followed the typical path of a startup. It is very neat to see the succession of larger and larger buildings with more and more sophisticated machinery inside. Precision started by modifying Garrett turbos and has advanced to the point that literally every component on their GEN 2 and other top of the line turbos is engineered 100% by them. Items like the stamped steel thermal shield separating the hotside from the bearing assembly are CNC machined out of stainless stock. Wow.
Dan showed me a Borg Warner compressor wheel and compared it to the Precision wheel... very impressive.
Unlike Borg Warner, a 9 Billion $ Revenue company serving primarily the OE market, Precision was started by a racer's racer (Harry Hruska) and is singularly focused on the sharp end of performance. Many BW engineers look at Precision with a wishful eye as BW turbos (including the racing side) have to live under somewhat burdensome constraints. while this is a good thing it does come with a price which is a slight discount to performance.
While many of us appreciate the 40% lighter EFR titanium aluminide turbine wheel (fast spool), there may be another side... according to Dan, Precision tried the material and found they were unable to shape it to their desired configuration and chose "flow over weight."
Precision has aggressively pursued a lower drag bearing system. A special ceramic ball bearing material allows them to not have to use oil as a thermal transfer. The bearing is air cooled contributing to a lower drag and faster spool.
All i can say is if you look at various serious race classes, where turbo selection s open, Precision is generally on the top of the podium. There are various areas of motorsports racing that I know very little about such as tractor pulling that are hugely popular and ultra competitive and, surprise, surprise offer huge purses to the winner where there is much grumbling among competitors that they are unable to get the latest Precision turbo to compete with fellow racers that do... and these turbos price north of $20,000!
If you are truly interested in cutting edge technology Precision should not be overlooked. I am not aware of one FD running a GEN2. Borg Warner, and to a lessor extent Garrett, power most FDs partially because of superior marketing to the community.
Precision remains very high on my interest list and i have a feeling that a Precision FD marriage would result in a significant re-appraisal of the brand.
as to a specific Precision recommendation for the street/track:
GEN2 6266SP 600 rotary rwhp
GEN2 6466 675 rotary rwhp
they do have a GEN2 6062 562 but the hotside is too small (5.408 sq inches) for the rotary.
While the newer 8474 makes 92 pounds of air and the 9180 makes 87, i prefer the 9180 for the rotary as it has a 21% larger turbine wheel. Rotaries need approximately 30% more air than a piston engine and that means they need to flow 30% more exhaust. Rotaries need LARGE hotside turbine wheels. A larger hotside wheel will lower EGTs and exhaust back pressure. While the 5.91 average square inch hotside wheel might work O K for the 8374 i do not like it matched up with a 92 pound per minute compressor wheel on the 8474 for the rotary. When i swapped in my 9180 ( 7.14 square inch turbine wheel) after testing a SX-E with a 6.31 inch wheel my EGTs dropped 100 F and my backpressure was 20% less.
The best way to understand this important relationship is to compare the turbine wheel average area (TWAA) to the maximum compressor output in pounds per minute (PPM) of air. We end up with a helpful ratio:
EFR
8374 72 pounds per minute (PPM) / 5.91 turbine wheel average area (TWAA) = 12.18
8474 92 PPM / 5.91 TWAA = 15.56
9174 86 PPM / 5.91 TWAA = 14.55
9180 87 PPM / 7.15 TWAA = 12.17
9274 105 PPM / 7.15 TWAA = 14.68
9280 110 PPM / 7.15 TWAA = 15.38
SX-E
62 76 PPM / 6.31 TWAA = 12.04
62 76 PPM / 7.15 TWAA = 10.63 (optional 80 mm turbine wheel)
63 78 PPM / 6.31 TWAA = 12.36
63 78 PPM / 7.15 TWAA = 10.91 (optional 80 mm turbine wheel)
64 81 PPM / 6.31 TWAA = 12.83
64 81 PPM / 7.15 TWAA = 11.33 (optional 80 mm turbine wheel)
66 87 PPM / 7.15 TWAA = 12.17
69 98 PPM / 7.15 TWAA = 13.70
72 112 PPM / 7.15 TWAA = 15.66
As we draw conclusions from the above relationships keep in mind that the rotary exhaust differs significantly from the piston engine:
requires approximately 30% more airflow versus a piston engine and therefore produces 30% more exhaust flow
due to no exhaust valve and a straight shot from the combustion chamber is approximately 300 F higher temperature
both of these factors place an important premium on a larger turbine wheel and hotside housing.
Consider the above ratios... blue is rotary friendly, red is not.
I like the EFR 8374 and the EFR 9180... I like the SXE 62, 63 with either wheels and the 64 with the larger wheel. BW recognized this and does not offer the 66 with the smaller wheel. The 66 looks really good for the rotary and has a small 52 trim bringing mid range to the high power party. BW uses the same larger wheel for the 69 and 72 and you can see it is small for the compressor output.
(Please see the end of this section for an explanation re areas of compressor and turbine wheels and a complete list of virtually all turbos with wheel areas.)
As to power, my 9180 is not fully evaluated but it did make 585 rwhp at 24.9 psi boost on 93 pump and 1000 cc of methanol as AI. Right on the money with more available. I may run my 9180 in October at the Texas Mile. I should be able to run just over 200 mph at the 575 power level.
It is possible to project power at higher boost levels if you have a base number. For instance in the above example at 24.9 and 585...
Let's say you want to know power at 29 psi...
The key to getting to a fairly close number is to remember that the 24.9 is in addition to the 14.7 of atmospheric pressure.
24.9 + 14.7 = 39.6
29 + 14.7 = 43.7
43.7/39.6 = 1.10
585 X 1.1 = 643 rwhp at 29 psi
Caveats: This assumes the turbo can produce air at the higher boost and does not factor any drop off in efficiency. All calculations carry with them qualifiers and should only be used as a guide but the key here is realizing that you need to add in atmospheric pressure
Airwerks S300 SX-E
BorgWarner's legacy brand is the updated Airwerks S300 series, known as the Airwerks S300 SX-E. While the general S300 frame has been around and quite successful for many years BW did a major high tech, very recent update. This re-work occurred after most of the EFR project and i find the SX-E compressor maps are often slightly superior to the EFR maps by virtue of wider efficiency islands. The recent SX-E upgrade extends to the twin hydrodynamic bearings with the addition of a 360 degree axial thrust bearing. Unlike the EFR line the SX-E line does not offer water cooling to the bearing case. While this might be preferable i have found that it is not an issue. Both lines use an aluminum forged billet material for the compressor wheel.
Both employ BW's extended tip technology which makes the wheel effectively bigger.
Circling back to the question relating to turbine sizing and the rotary and looking at the data it is easy to see that Garrett has created something special. More power, more efficiency. While i have experienced this with my G40-1150, Garrett has a full line of options for any rotary app. Many other options are just clones of the G40 but in a different size.
One of the most attractive options is the 2024 version of the GT3582r. When the GT3582r was introduced at the end of the last century it literally turned the performance world upside down. In 2000 the GT was on the podium at LeMans. Such a shift from tractor turbos. Ball bearings, greatly uprated aero wheels in such a small 194 inch package. Without any question the Garrett GT35 laid the foundation for all modern turbos. Here's the original compressor map from my archives:
Garrett G40-1150 turbine wheel
The EFR 8374 and S300 SE-E 62 have virtually the same size compressor wheels however there are not insignificant differences as to their output as expressed within their respective compressor maps.
I see 3 primary differences.
Maximum air output advantage SX-E, 76 versus 73.
The SX-E starts working earlier, for instance at 20 psi boost ( 2.36 Pressure Ratios) the SX-E starts working at 22 and the EFR at 26. While both these metrics are at the edges of the map the important widths of efficiency measurements are perhaps more important and favor the SX-E.
I measured the width of the 70% efficiency islands on all 6 Borg Warner SX-E turbos and 5 EFR models at 17.4 psi (2.2 Pressure Ratios), 20 psi (2.36 P R), and 30 psi (3 P R). I added the 3 widths together.
SX-E 62 width totaled 107.5
EFR 8374 92.5
Wider is of course better and better efficiency is at work all the time the engine is operating. Cooler Intake Air Temperatures and more oxygen more easily into the motor.
The difference is certainly not a deal breaker but there is an edge in this area that goes to the SX-E. In other areas such as dynamic spool the EFR line has an advantage due to the 40% lighter turbine wheel. Other EFR advantages are the bearing system... less overall drag, less axial (front to rear) drag and water cooled. The EFR also incorporates a boost re-circulating (blow off valve) within the compressor cover.
There are four SX-E sizes that are of interest if we are shopping for approximately 600 maximum.
SXE-62 570 max rw rotary hp
SX-E 63 587
SX-E 64 610
SX-E 66 655
There are two SX-E turbine wheel sizes. The "76" wheel and the "80". Both hotside wheel sizes are available for the 62, 63 and 64. The 66 is available only with the 80. The "76" wheel is actually LARGE and fits the rotary like a custom made suit. General thinking (often wrong) is that the 80 wheel is too large for the 62 compressor but after doing extensive testing with both the 76 and 80 i am very interested in testing the 62 with an 80 hotwheel. No doubt lower EGTs and backpressure, the question is as to spool.
I really like both ends of this list. I love the SX-E 62 as a bread and butter high tech do most everything turbo perfectly suited for probably 80% of RX7 owners. For the other 20% looking for the higher end of the SX-E power range i love the 66 as it has a 52 Trim making it not only a top end monster but a killer in midrange.
In summary as to Borg Warner i am very impressed with all of their turbos.
EFR clean sheet of paper design down to the last nut and bolt. OE durability, quality yet radical in design targeting maximum output dynamics.
SX-E very aggressive update to bullet proof legacy line. priced at approximately 40% of the equivalent EFR.
PRECISION TURBO
This is what Precision is all about... WINNING ON BIG TIME STAGES SUCH AS NHRA PRO MOD
Based on my interest of approximately 600 maximum rear wheel horsepower, and the need to have the turbo produce a bit more so it won't be running on the wrong end of the efficiency curve, there are three EFR turbos that are attractive.
EFR 8374 529 max rotary rear wheel horsepower
EFR 8474 693 max rrwhp
EFR 9180 655 max rrwhp
The 8374 is to the rotary as the Garrett GT3582r was back in the day. Groundbreaking technology, premium priced, appealing to medium power buyers. It is an excellent turbo.
I owned and have evaluated the EFR 9180.
Similar to Borg Warner, Garrett's roots reach back many decades and both companies are now major corporate entities. Both focus on the OE global markets and test much of their engineering in a broad range of motorsports markets. Just around the corner in the up engineered OE markets is the E Turbo and Garrett's lead E Turbo product is already making major waves powering the all conquering Mercedes AMG ONE. The ONE recently lowered it's own 6:34 all time production car record at Nurburgring to 6:29! Everything on the car is cutting edge including the Garrett E Turbo powering the 1.6L V6.
82 pounds of air around 20 psi! Wow, 615 rotary rwhp.
i have an engine customer that bought this turbo on my recommendation and will be firing it up this spring. While 80 pounds of air isn't uncommon today what is uncommon is the size of the turbo which makes fitting it into the engine compartment so much easier.
The G35-900 is my top suggestion for a majority of the new builds in 2024/2025. Garrett engineering and quality in a killer turbo. Happy tooling around town and on track.
Should neither the G35-900 or the G40-1150 be your fit please do refer to Garrett's catalog for a blizzard of options but know they all carry Garrett state of the art technology.
GARRETT
During the final stages of the SX-E workup BW found something new on the compressor side that led them to delay introduction for 6 months. The compressor wheels on the EFR and SX-E are very close to identical and speculation is that it was something within the compressor cover design. Whatever. I find it interesting that a comparison of an EFR and SX-E compressor map does favor the SX-E.