TURBOCHARGER SPECS







​exducer inducer trim GT say what?

As i initially approached understanding turbos things became more, not less, confusing... some referenced turbos by inducer size, some by exducer. of course they reverse when you are talking turbine wheel V compressor.

I felt there needed to be a better way of comparing turbos.

As you may know, all wheels have a minor diameter size and a major diameter. They are often in inches or millimeters. I wanted something simple to help me with sizing them and settled on the following:.

take the minor diameter and solve for the area.
take the major diameter and solve for the area.
add together, divide by two.

you now have the average area of the wheel.

do it for the compressor (coldside/intake) , do it for the turbine (hotside/exhaust).

You now have two understandable numbers that help a great deal when you seek to compare turbos. Needless to say there is a major correlation between area and airflow.

The cold side area determines the airflow potential, the hotside must deliver the power to actualize the potential.

hot area V cold area is especially valuable w the rotary. The rotary places a premium on large hot V cold wheel relationships. you want something approaching 1 to 1 areawise.

EDIT NOTE: significant flow advances for newer turbos which are bolded 



Here's the list in square inches:..........cold.......................hot....................relationship

GT2860RS (Disco Potato).....................3.549................. ..3.105.................... 87%
FC T2 (OEM).........................................3.57 9....................4.288................... 119
BW EFR "6255".......discontinued..........3.79........... ...........6.758....................178
TDO5H 18G..........................................4.375 ......................3.363....................77
BW EFR "6758"....................................4.498... .................5.229....................86
BW EFR "7064"....................................4.632... .................5.229.....................88
GT3071R........................................... ....4.776....................4.019................ ... 84
GT3071R........................................... ....4.776....................3.683................ .... 77
GT2876............................................ .....5.224.....................3.108.............. ..... 59
RX6 TCW 17..........................................5.29.. .....................4.315....................82
BW K27............................................... ..5.36.......................5.06................. .....94
TO4E 57 Trim........................................5.369. ....................5.408 (Stg 5)......... 100
GT3776............................................ .....5.374.....................5.441.............. ...... 101
BW S200SX...........................................5 .40......................5.24..................... ....97
TO4E 60 Trim.........................................5.476 ....................5.408...................... 98
GT3076R........................................... .....5.511...................4.019................ ....... 73
BW S300SXE 7670..................................5.52........ ............5.27........................95
BW EFR "7670"......................................5.524. ..................5.229.......................95
GTW5857........................................... ....5.59......................4.52................ .......81 
GTX3076R.......................................... .....5.614..................4.019................. ......71.5
RX6 TCW10............................................. 5.63....................4.315..................... ..77
HKS TO4S.............................................. .5.64.....................5.89.................... ....104
Turbonetics 60-1....................................5.647........ ...........5.89....................... 104
Turbonetics T61......................................5.79..... ............... 5.89......................101
TO4B 62-1..............................................5.8 7..................... 5.89...................... 100
FD (OEM)............................................. ....5.972.................5.25.................... ..... 88
RX6 TCW 76.............................................6.0 3....................4.315......................72
Precision 6062.........................................6.27. ...................5.408......................86
RX6 TCW77............................................. .6.356..................4.315..................... .68
Borg Warner S300 60 PN177282 & 80.....6.383..................6.328............... ........99
GT3582R........................................... ........6.386..................5.171.............. ........81
HTA 3582R (Forced Performance)............ 6.386.................5.171....................... 81
GT3574 (A-Spec, Turblown TD61)..............6.386..................5.89.(P) .................92
GT3082R........................................... .........6.386.................smaller than GT35R..?
Precision 6262...........................................6.4 48..................5.408.....................84
Precision 6265........................................... 6.448.................5.885 (P)...............91
GTX3582R.......................................... .........6.519..................5.171............. .......79
BW S362 FMW (billet)................................6.53...... ...............6.35......................97
BW S300 SXE 62-76..............................6.54.............. .......6.31.....................96 (2015) PN 13009097056   my 400-500 hp value pick for 2019
BW S300 SXE 62-80..............................6.54.............. .......7.15..................109 (2015) PN 13009097053 


BW EFR "8374"..........................................6. 626..................5.91....................89
BW, R85, TEC300...................................... 6.667...................6.93...................... 104
GTW6262........................................... ........6.69......................5.38............ .......80 (2015 Garrett)
GTW6265........................................... .........6.69....................5.88............. .......88 (2015 Garrett)
BW Bullseye S362.......................................6.69... .................6.31.....................94
GTX3582r GEN II........................................6.73.... ..................5.15....................76..(201 8 Garrett)
HTA 3586 (Forced Performance).................6.839................ ...5.171....................76
GTW6465........................................... ........6.84......................5.88............ ........86 (2015 Garrett)
Precision GEN2 6266..................................6.91........ .............6.........................87 (2015)
Borg W S300s 61/87(2010 catalog)...........6.946..................6.928... ..................100
Precision 6765............................................6. 997.................. 5.885 (P).............. 84
Precision 6768............................................6. 997..................6.652 (GTQ)........... 95
TO4Z, A Spec GT500 PT67...........................7.002.............. ....5.885 (P)...............87
GTX3584RS......................................... .........7.02.....................5.13............ .......73 (2016 Garrett)
BW S300 SXE 63..........................................7.06.. ..................7.15.....................101 (2015)
Borg Warner S300 63 PN177283................ 7.06....................6.31....................89
Precision GEN2 6466.....................................7.07..... ..............6.........................85 (2015)
GTW6765........................................... ............7.09....................5.88.......... .......83 (2015 Garrett)
BW EFR 8474.............................................. ..7.10....................5.91..................83 (2019)
GT3788R........................................... ........... 7.155................. 5.694...................80
GT4088R........................................... ........... 7.167................. 6.423...................90
GTX4088R.......................................................7.167.. ................6.423.................90
Borg Warner S364 FMW...............................7.17............ ........6.31....................88
BW S300 SXE 64...........................................7.17. ...................7.15...................99 (2015)
GT4088............................................ ............ 7.26.................... 6.633..................91
Precision 6766...........................................7.5 1......................6......................80 (2016)
T78............................................... ............... 7.584................... 5.903................. 78
T88 33D............................................... ........ 7.58..................... 7.577................. 100
T66............................................... ............... 7.657.................. 5.894.................77
Borg Warner S300X 9179............................ 7.691................... 5.885 (P)........... 77
BW S300 SXE 66..........................................7.74.. .....................7.15...................92 (2015)  My 2019 pick for 600 rotary rwhp at a value price. Love the small trim and big top end contact me
Borg W S300sx 66/91(2010 catalog)............7.743....................7.151 .................92
Garrett G42-1200...........................................7.7 5.....................7.52..................97 (2018)
BW EFR 9180.............................................. ....7.84....................7.189................. 92  i own and will be further testing this turbo in 2019. i may run it at Texas Mile
Borg Warner S366......................................... 7.88.....................7.15................... 91
BW S300 SXE 69...........................................7.99. ......................7.15..................89 (2015)
Precision GEN2 6870.....................................8.01..... .................6.77..................85 (2015)
Xona/Tial 6894 "XR 95-68 X3C"......................8.17.................... 6.34...................78 (2019)  i will be taking a close look at this cutting edge turbo
GT4094R........................................... ........... 8.175................... 6.423..................79
BW S300 SXE 72..........................................8.18.. ................. 7.15......................87 (2019)
BW EFR 9274.............................................. ..8.18...................7.15..................... ..87 (2019)
BW EFR 9280.............................................. ..8.36....................7.15.................... .85 (2019)
GT4294, T51R.............................................. 8.384................... 7.527..................90
Borg W K29 Billet (2010 catalog)..................8.432................... .7.175..................85
T88 34D............................................... ........ 8.449................... 7.577.................. 90
MasterPower "GT42"................................... 8.658................... 6.871................. 79
T70............................................... ................ 8.725.................. 6.648.................. 76
Borg Warner S368.........................................9.1.. ......................7.49....................77
Borg W S400sx (2010 catalog)......................9.174............... .....7.62....................83
Borg Warner S372-80.................................. 9.456................... 7.173................... 76
Borg Warner S372-83.4............................... 9.456................... 7.593................... 80
Borg Warner S372-84.................................. 9.456................... 10.298................. 109
Borg Warner S475....................................... 9.49...................... 10.292.................108
T72............................................... ................. 9.549.................. 6.648 (Q)............. 69
GT4202............................................ ............. 9.726................... 7.527.................... 77
T51R Spl............................................... ......... 9.92..................... 7.194.................... 73
Borg W K29 Billet (2010 catalog)..................8.432................... .7.175..................85
Masterpower GT45................................... 10.082..................... 8.4739.................... 84
T88 34D............................................... ........ 8.449................... 7.577.................. 90
MasterPower "GT42"................................... 8.658................... 6.871................. 79
T70............................................... ................ 8.725.................. 6.648.................. 76
Borg Warner S368.........................................9.1.. ......................7.49....................77
Borg W S400sx (2010 catalog)......................9.174............... .....7.62....................83
Borg Warner S372-80.................................. 9.456................... 7.173................... 76
Borg Warner S372-83.4............................... 9.456................... 7.593................... 80
Borg Warner S372-84.................................. 9.456................... 10.298................. 109
Borg Warner S475....................................... 9.49...................... 10.292.................108
T72............................................... ................. 9.549.................. 6.648 (Q)............. 69
GT4202............................................ ............. 9.726................... 7.527.................... 77
T51R Spl............................................... ......... 9.92..................... 7.194.................... 73
Masterpower GT45................................... 10.082..................... 8.4739.................... 84%




Some turbos can be fixtured w different hotside wheels. Most now employ billet compressor wheel which may offer additional flow per diameter due to less hub/more fins. 

Trim relationships are important. High trim numbers indication the input diameter is closer to the output diameter favor top end while smaller numbers favor midrange.


Please do visit the System Design Section as to optimally incorporate your turbo.


Lots more to come soon in this Section.






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.  

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.

I do consult and sell BorgWarner, Garrett and Xona turbos as well as consult on Precision.  contact: howracer@gmail.com

​COVERAGE OF GARRETT, PRECISION AND XONA ROTOR TURBOS COMING SOON

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.

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 four companies.

                        BorgWarner



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

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 the to the rotary as the Garrett GT3582r was back in the day. Groundbreaking technology, premium priced, appealing to the modest to medium power buyers. It is an excellent turbo.

I own and am in process of testing the EFR 9180. 

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 2960 compared to the fatties around 3900 pounds or more. 


                                                                                                   2960 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...   

Turbos are more difficult to analyze, for instance here are two..

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                     2960 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...