Making the case for the TURBO'D rotary FD... Turbo options simplified
10-20-09, 02:10 PM
#1
Racing Rotary Since 1983
Thread Starter
iTrader: (6)
Making the case for the TURBO'D rotary FD... Turbo options simplified
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.
i 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 actualise 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.
here's my list in square inches:...............cold.......................h ot....................relationship
GT2860RS (Disco Potato).....................3.549................. ..3.105.................... 87%
FC T2 (OEM).........................................3.57 9....................4.288................... 119
GT3071R........................................... ....4.776....................4.019................ ... 84
GT3071R........................................... ....4.776....................3.683................ .... 77
GT2876............................................ .....5.224.....................3.108.............. ..... 59
TO4E 57 Trim........................................5.369. ....................5.408 (Stg 5)......... 100
GT3776............................................ .....5.374.....................5.441.............. ...... 101
TO4E 60 Trim.........................................5.476 ....................5.408...................... 98
GT3076R........................................... .....5.511...................4.019................ ....... 73
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
BW BullsEye S362................................... 6.291................ 5.408...................... 86
RX6 TCW77............................................. .6.356..................4.315..................... .68
Borg Warner S300SX 8375......................6.383..................5 .408.......................85
GT3582R........................................... ........6.383..................5.171.............. ........81
HTA 3582R (Forced Performance)............ 6.383.................5.171....................... 81
A Spec GT3574..........................................6. 383................5.89.........................92
GT3082R........................................... .........6.386.................smaller than GT35R..?
Precision 6262...........................................6.4 48..................5.408.....................84
Precision 6265........................................... 6.448.................5.885 (P)...............91
BW, R85, TEC300...................................... 6.667...................6.93...................... 104
HTA 3586 (Forced Performance).................6.839................ ...5.171....................76
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
Borg Warner S300SX 8875......................... 7.12....................5.408....................7 6
GT3788R........................................... ........... 7.155................. 5.694...................80
GT4088R........................................... ........... 7.167................. 6.423...................90
GT4088............................................ ............ 7.26.................... 6.633..................91
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
Borg Warner S366....................................... 7.88..................... 6.23................... 79
GT4094R........................................... ........... 8.175................... 6.423..................79
GT4294, T51R.............................................. 8.384................... 7.527..................90
T88 34D............................................... ........ 8.449................... 7.577.................. 90
MasterPower "GT42"................................... 8.658................... 6.871................. 79
T70............................................... ................ 8.725.................. 6.648.................. 76
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
i also have max flow numbers in pounds per minute for each turbo that has a compressor map. take the pounds per minute, multiply by 14.471 to get CFM and divide by 1.92 to get approx max rear wheel rotary hp. or take pounds per minute, multiply by 10 and divide by 1.3 to get to the same general vicinity.
for instance... the GT3582R puts a hair better than 60 pounds per minute between 2.3 and 2.9 pressure ratios. (19-28 psi).
so, 60 X 14.471 = 868 CFM/ 1.92 = 452 max rotary rwhp. if you will notice the compressor map at 60 pounds you will note the RPM lines are very close to vertical which means the compressor is not able to accelerate further... it is very close to stall mode. overdriven.
a turbo acts at this point as a restrictor plate ala NASCAR. no more air. so IF the compressor map is accruate that's about it. you can do the same for any of the turbos.
this thread should be read as a companion to my "Making the case for the (rotary) powered FD.. The Fix.
the Fix is AI.
and AI changes how we can fixture our cars. we can run larger turbos because alcohol and water cools the CCP.
so take a look at the above list and pick your poison. i like 550 as a max target as above that number the engine becomes a bit in need of some reconstruction. also, if you have ever been in a 500 hp FD you will quickly realise it is about all you can hope to hook up without different transmissions and rear driveline components.
most of the numbers above should be accurate. feel free to offer any corrections. some turbos above can be fixtured w different hotside wheels. also the new deal is the billet compressor wheel which may offer additional flow per diameter due to less hub/more fins. most of this addition happens at very high pressure ratios (boost) and we are all waiting to see what happens when billet meets rotary.
trim relationships also add or detract from low rpm V higher RPM but area numbers should, i hope, be helpful.
additional turbo discussion welcomed... especially considering the ability to run alot more airflow w AI.
howard coleman
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.
i 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 actualise 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.
here's my list in square inches:...............cold.......................h ot....................relationship
GT2860RS (Disco Potato).....................3.549................. ..3.105.................... 87%
FC T2 (OEM).........................................3.57 9....................4.288................... 119
GT3071R........................................... ....4.776....................4.019................ ... 84
GT3071R........................................... ....4.776....................3.683................ .... 77
GT2876............................................ .....5.224.....................3.108.............. ..... 59
TO4E 57 Trim........................................5.369. ....................5.408 (Stg 5)......... 100
GT3776............................................ .....5.374.....................5.441.............. ...... 101
TO4E 60 Trim.........................................5.476 ....................5.408...................... 98
GT3076R........................................... .....5.511...................4.019................ ....... 73
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
BW BullsEye S362................................... 6.291................ 5.408...................... 86
RX6 TCW77............................................. .6.356..................4.315..................... .68
Borg Warner S300SX 8375......................6.383..................5 .408.......................85
GT3582R........................................... ........6.383..................5.171.............. ........81
HTA 3582R (Forced Performance)............ 6.383.................5.171....................... 81
A Spec GT3574..........................................6. 383................5.89.........................92
GT3082R........................................... .........6.386.................smaller than GT35R..?
Precision 6262...........................................6.4 48..................5.408.....................84
Precision 6265........................................... 6.448.................5.885 (P)...............91
BW, R85, TEC300...................................... 6.667...................6.93...................... 104
HTA 3586 (Forced Performance).................6.839................ ...5.171....................76
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
Borg Warner S300SX 8875......................... 7.12....................5.408....................7 6
GT3788R........................................... ........... 7.155................. 5.694...................80
GT4088R........................................... ........... 7.167................. 6.423...................90
GT4088............................................ ............ 7.26.................... 6.633..................91
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
Borg Warner S366....................................... 7.88..................... 6.23................... 79
GT4094R........................................... ........... 8.175................... 6.423..................79
GT4294, T51R.............................................. 8.384................... 7.527..................90
T88 34D............................................... ........ 8.449................... 7.577.................. 90
MasterPower "GT42"................................... 8.658................... 6.871................. 79
T70............................................... ................ 8.725.................. 6.648.................. 76
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
i also have max flow numbers in pounds per minute for each turbo that has a compressor map. take the pounds per minute, multiply by 14.471 to get CFM and divide by 1.92 to get approx max rear wheel rotary hp. or take pounds per minute, multiply by 10 and divide by 1.3 to get to the same general vicinity.
for instance... the GT3582R puts a hair better than 60 pounds per minute between 2.3 and 2.9 pressure ratios. (19-28 psi).
so, 60 X 14.471 = 868 CFM/ 1.92 = 452 max rotary rwhp. if you will notice the compressor map at 60 pounds you will note the RPM lines are very close to vertical which means the compressor is not able to accelerate further... it is very close to stall mode. overdriven.
a turbo acts at this point as a restrictor plate ala NASCAR. no more air. so IF the compressor map is accruate that's about it. you can do the same for any of the turbos.
this thread should be read as a companion to my "Making the case for the (rotary) powered FD.. The Fix.
the Fix is AI.
and AI changes how we can fixture our cars. we can run larger turbos because alcohol and water cools the CCP.
so take a look at the above list and pick your poison. i like 550 as a max target as above that number the engine becomes a bit in need of some reconstruction. also, if you have ever been in a 500 hp FD you will quickly realise it is about all you can hope to hook up without different transmissions and rear driveline components.
most of the numbers above should be accurate. feel free to offer any corrections. some turbos above can be fixtured w different hotside wheels. also the new deal is the billet compressor wheel which may offer additional flow per diameter due to less hub/more fins. most of this addition happens at very high pressure ratios (boost) and we are all waiting to see what happens when billet meets rotary.
trim relationships also add or detract from low rpm V higher RPM but area numbers should, i hope, be helpful.
additional turbo discussion welcomed... especially considering the ability to run alot more airflow w AI.
howard coleman
Last edited by Howard Coleman; 10-27-09 at 09:01 AM.
10-20-09, 04:23 PM
#3
Howard,
I appreciate your efforts in bringing turbo selection to the masses. But I'm concerned that you're entering into the territory of oversimplification, especially since there was no discussion of thermal efficiency at given pressure ratios. Thermal efficiency is the amount of energy you get out of a system compared to how much you put in, and it is very important when reading compressor maps and sizing a turbo.
There are so many other aspects of turbo design and so many confusing names out there. I made a thread a while back in the single turbo that was a guide various manufacturer's naming schemes (nomenclature): https://www.rx7club.com/single-turbo-rx-7s-23/official-turbo-nomenclature-guide-796257/
Compressor flow dynamics are pretty complicated. I've lately been reducing SAE and other fluid dynamics journals in an effort to understand centrifugal compressor (any compressor that is similar to a turbo) design, and I feel that I know even less now than I did before. I'm not sure how useful the area really is. The area of the wheel may help us compare how big one wheel is to another, but it still gives us no real understanding of a compressor wheel's efficiency at a given level of boost. Beyond the basic flow rate, it is the efficiency of the compressor that tells us its ability to make power in the way we intend to use it.
After you get the basic measurements of the wheel, it is more important to understand the relationship between the inducer and the exducer. The inducer is the smaller part of the wheel which draws the air in an axial direction (towards the middle, think 3 dimensionally). The exducer is the larger wheel measurement which directs the air laterally into the volute (the snail part). The ratio between those two is called the trim.
Trim is inducer^2 / exducer ^2 . Compressor area tells us nothing about efficiency, or how much useable energy the turbo will produce at a given flow rate. The higher the trim value, the more efficient the turbo is at lower pressure ratios compared to other similarly sized turbos.
50 trim T04E wheel:
60 trim T04E wheel:
I know a lot of the people reading this have only an inkling about how to read compressor maps. Let's just say that the higher number on the left, the more efficient it is at higher boost, generally speaking. The 60 trim wheel flows more air but doesn't do so well at high boost. A lot of high horsepower 4 cylinder cars use 40 to 50 trim turbos and boost 30-35psi.
You have to be really careful with "max flow numbers" you may read. They are usually measured at the choke line, the point where the compressor wheel is pushed to its absolute limit. Maximum flow ratings are often not very good indicators of what the turbo can do reliably at the boost level you intend to run.
In theory this is important, but in reality there are only two wheels that most people use on street Rx-7's with Garret based turbos:
1. a T3 stage V equivalent wheel and its cousin, the GT35 turbine wheel. These are used on T3 turbine housings. This includes all the precision wheels.
2. the P trim wheel (65mm on the small/exducer measurement, 74mm on the major side). These are used on T4 hotsides. There are also larger ones like the Q trim, and the larger GT class turbine wheels (GT40, GT42 etc)
of course there are Greddy/Mitsu, Holset, Borg Warner etc. the area is all well and good but you don't have that many turbine wheel choices, and that's where compressor area comes into play.
I appreciate your efforts in bringing turbo selection to the masses. But I'm concerned that you're entering into the territory of oversimplification, especially since there was no discussion of thermal efficiency at given pressure ratios. Thermal efficiency is the amount of energy you get out of a system compared to how much you put in, and it is very important when reading compressor maps and sizing a turbo.
There are so many other aspects of turbo design and so many confusing names out there. I made a thread a while back in the single turbo that was a guide various manufacturer's naming schemes (nomenclature): https://www.rx7club.com/single-turbo-rx-7s-23/official-turbo-nomenclature-guide-796257/
you now have the average area of the wheel.
After you get the basic measurements of the wheel, it is more important to understand the relationship between the inducer and the exducer. The inducer is the smaller part of the wheel which draws the air in an axial direction (towards the middle, think 3 dimensionally). The exducer is the larger wheel measurement which directs the air laterally into the volute (the snail part). The ratio between those two is called the trim.
Trim is inducer^2 / exducer ^2 . Compressor area tells us nothing about efficiency, or how much useable energy the turbo will produce at a given flow rate. The higher the trim value, the more efficient the turbo is at lower pressure ratios compared to other similarly sized turbos.
50 trim T04E wheel:
60 trim T04E wheel:
I know a lot of the people reading this have only an inkling about how to read compressor maps. Let's just say that the higher number on the left, the more efficient it is at higher boost, generally speaking. The 60 trim wheel flows more air but doesn't do so well at high boost. A lot of high horsepower 4 cylinder cars use 40 to 50 trim turbos and boost 30-35psi.
i also have max flow numbers in pounds per minute for each turbo that has a compressor map. take the pounds per minute, multiply by 14.471 to get CFM and divide ny 1.92 to get approx max rear wheel rotary hp. or take pounds per minute, multiply by 10 and divide by 1.3 to get to the same general vicinity.
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.
1. a T3 stage V equivalent wheel and its cousin, the GT35 turbine wheel. These are used on T3 turbine housings. This includes all the precision wheels.
2. the P trim wheel (65mm on the small/exducer measurement, 74mm on the major side). These are used on T4 hotsides. There are also larger ones like the Q trim, and the larger GT class turbine wheels (GT40, GT42 etc)
of course there are Greddy/Mitsu, Holset, Borg Warner etc. the area is all well and good but you don't have that many turbine wheel choices, and that's where compressor area comes into play.
10-20-09, 07:49 PM
#4
Racing Rotary Since 1983
Thread Starter
iTrader: (6)
all good points that are additive and we could go on and on but there is a relationship between flow and average compressor area and it is a nice place to start.
howard
howard
10-20-09, 08:21 PM
#5
Over the years I have developed a spread sheet (actually I used many of the calculations that J.D. Estill formulated years ago) for sizing fueling systems and turbochargers. This last year I have been working to adapt the tool to the rotary engine. Needless to say the rotary dynamics are vastly different from reciprocating - so the work continues. The thermodynamics and mass flow properties play critical rolls in the turbocharger turbine and compressor sizing. You can see in the below example the variance in the P2/P1 vs. mass flow over the RPM range by the same turbocharger (it is not linear). As far as the turbocharger goes this tool allows one to plot a line (P2/P1 and mass flow) over a turbo map allowing a proper selection of the compressor. I do like Howard Coleman's relationship between the compressor and turbine wheels however the blade depth plays a more important roll.
I can't seem to figure out to post a bigger picture so in you know a way let me know and I'll repost.
If anyone is interested I can send the Excel file so you can play with it - just PM me.
I can't seem to figure out to post a bigger picture so in you know a way let me know and I'll repost.
If anyone is interested I can send the Excel file so you can play with it - just PM me.
10-22-09, 09:22 PM
#7
Compressor Map 101 -
Hopefully this will help some on what the turbocharger compressor maps mean:
The map simply shows the efficency of the compressor as a pump.
Efficiency means a measurement of the compressor to provide the highest mass of air for the work needed to produce the air.
OK - The line drawn up through the map is a calculated line based upon the derived engine performance parameters (compressor flow demand / desire, capability to pressurize the engine, thermodynamic effects of the pump, and engine RPM. Note when calculating the mass corrected air flow it aligns with engine RPM so one can plot very well a performance curve on the map.
The objective is to contain your engine operating "sweet spot" in the highest efficiency island. This will provide the coolest most efficient mass air flow from the compressor. In the below map (I didn't show the engine RPM here) the engine is operating between 3500 and 4500 RPM right in the highest efficiency. Secondly, the line is well distanced from the surge limit at any appreciable load. This would be a very good choice for a street engine. Conversly, for a drag engine where one would want to stage at say 8500 RPM and produce maximum efficiency between 8000 and 9500 RPM this compressor would be small. Hope this helps....
Hopefully this will help some on what the turbocharger compressor maps mean:
The map simply shows the efficency of the compressor as a pump.
Efficiency means a measurement of the compressor to provide the highest mass of air for the work needed to produce the air.
- Pressure Ratio is the outlet pressure over the inlet pressure measured in PSIA
- Air Flow is the corrected for temperature mass air flow produced by the compressor in pounds per minute.
- The compressor map circular shapes are known as the "efficiency islands"; these are the performance areas in the pump in percent efficiency. In the below map for this Turbonetics T61 76% is the highest efficiency.
- The map curved lines are the turbine and compressor rotating components speed in RPM. These really have little to do with specifying a compressor other than when the demand will extend into or past the maximum shown rotor speed.
- The Surge limit line is where the mass flow related to the pressure ratio results in stalled or unstable air flow. Operating to the left of the surge limit will potentially damage the compressor. If you ever see a turbocharger comming up on a dyno and it looks like it wants to jump out of the engine bay it is probably operating too close to the surge line.
OK - The line drawn up through the map is a calculated line based upon the derived engine performance parameters (compressor flow demand / desire, capability to pressurize the engine, thermodynamic effects of the pump, and engine RPM. Note when calculating the mass corrected air flow it aligns with engine RPM so one can plot very well a performance curve on the map.
The objective is to contain your engine operating "sweet spot" in the highest efficiency island. This will provide the coolest most efficient mass air flow from the compressor. In the below map (I didn't show the engine RPM here) the engine is operating between 3500 and 4500 RPM right in the highest efficiency. Secondly, the line is well distanced from the surge limit at any appreciable load. This would be a very good choice for a street engine. Conversly, for a drag engine where one would want to stage at say 8500 RPM and produce maximum efficiency between 8000 and 9500 RPM this compressor would be small. Hope this helps....
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