Comparison of Rx-7 13B-REW and Supra 2JZ-GTE sequential turbos
12-10-11, 09:35 AM
#27
The 2JZ doesn't have a CRV but the 2JZ was engineered not to have one.
Thank you for the positive feedback. There is about equal amount of info out there for both the REW and the 2JZ, it's just easier to find for the REW. I'm good at digging stuff up.
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Gear2078 (11-07-18)
08-06-12, 10:29 AM
#28
So I stumbled upon some diagrams of the Porsche 959 engine. This is the first production engine with sequential twin turbos.
You can see it's a flat 6 with one turbo charger on each bank, with what appears to be the muffler located in the front of the picture. There's also two external wastegate style valves, one on each bank. I found two unlabeled diagrams showing airflow under primary turbocharger operation and operation after the turbo transition.
Just looking at this diagram I can speculate about the overall arrangement. There are two banks with a crossover pipe between them. Exhaust flows through the turbocharger on the left, exiting out the muffler at the bottom of the diagram. Compressed air flows through an intercooler into the throttlebody. The secondary turbo (on the right) seems to have its exhaust flow plugged up by an external-wastegate style valve (right, #10). The compressor side of the secondary turbo looks like it has a valve controlling its flow (right, #8). The basic control concept is similar to the Supra 2JZ engine.
After transition, the exhaust flows out of the secondary turbocharger on the right and an external wastegate (left, #8) opens to bleed off exhaust for boost control. Air flows through both turbochargers and both intercoolers in the throttlebody.
I'm not sure exactly how the transition is handled. The valve on the exhaust side of the secondary turbo may be duty controlled. It doesn't look like there is a dedicated "prespool valve" like the 2JZ and 13B-REW have.
You can see it's a flat 6 with one turbo charger on each bank, with what appears to be the muffler located in the front of the picture. There's also two external wastegate style valves, one on each bank. I found two unlabeled diagrams showing airflow under primary turbocharger operation and operation after the turbo transition.
Just looking at this diagram I can speculate about the overall arrangement. There are two banks with a crossover pipe between them. Exhaust flows through the turbocharger on the left, exiting out the muffler at the bottom of the diagram. Compressed air flows through an intercooler into the throttlebody. The secondary turbo (on the right) seems to have its exhaust flow plugged up by an external-wastegate style valve (right, #10). The compressor side of the secondary turbo looks like it has a valve controlling its flow (right, #8). The basic control concept is similar to the Supra 2JZ engine.
After transition, the exhaust flows out of the secondary turbocharger on the right and an external wastegate (left, #8) opens to bleed off exhaust for boost control. Air flows through both turbochargers and both intercoolers in the throttlebody.
I'm not sure exactly how the transition is handled. The valve on the exhaust side of the secondary turbo may be duty controlled. It doesn't look like there is a dedicated "prespool valve" like the 2JZ and 13B-REW have.
08-14-12, 09:05 PM
#31
Very interesting about the control of the CRV versus the Y pipe CCV.
I always assumed the following:
CRV = open when CCV = closed. (prespool)
CRV = closed when CCV = open (secondary online)
I had no idea that the ECU is able to (via electronic switching of the appropriate solenoid to supply a vac signal to the top of the CRV) modulate when the CRV opens and closes, to bring the secondary turbo into surge.
I always thought it was dumber than this- CCV flaps open, CRV shuts, in one swift operation. Apparently the ECU is smarter than I gave it credit for...
Deleting the CRV is probably not going to achieve anything good, if this is how it is controlled. You'll operate in surge exclusively, and who knows how that would affect turbine speed.
Also says that the cars we bring in from Japan which have two aftermarket BOVs (one replacing the CRV) are not functioning well in their secondary system operation.. I've even seen some BOV manufacturers list that the 3rd Gen "requires 2x BOV" and double the price of their BOV kits, because they assume in error that the CRV functions like the stock bypass valve and you should replace both with a BOV. Clearly not the case, but we all knew that already.
Really really amazed me to know that the BMW V8 has reversed flow cylinder heads. Blows my mind. But makes so much sense really. Much more compact to direct the gases to a central place in the valley.
I always assumed the following:
CRV = open when CCV = closed. (prespool)
CRV = closed when CCV = open (secondary online)
I had no idea that the ECU is able to (via electronic switching of the appropriate solenoid to supply a vac signal to the top of the CRV) modulate when the CRV opens and closes, to bring the secondary turbo into surge.
I always thought it was dumber than this- CCV flaps open, CRV shuts, in one swift operation. Apparently the ECU is smarter than I gave it credit for...
Deleting the CRV is probably not going to achieve anything good, if this is how it is controlled. You'll operate in surge exclusively, and who knows how that would affect turbine speed.
Also says that the cars we bring in from Japan which have two aftermarket BOVs (one replacing the CRV) are not functioning well in their secondary system operation.. I've even seen some BOV manufacturers list that the 3rd Gen "requires 2x BOV" and double the price of their BOV kits, because they assume in error that the CRV functions like the stock bypass valve and you should replace both with a BOV. Clearly not the case, but we all knew that already.
Really really amazed me to know that the BMW V8 has reversed flow cylinder heads. Blows my mind. But makes so much sense really. Much more compact to direct the gases to a central place in the valley.
08-15-12, 08:57 AM
#33
I've often wondered if you were the same 'Argh' poster as the one on M5Board.com, with the black porsche avatar, that used to frequent the E39 M5 section, back when I played around with mine.. You seem to know your stuff pretty well.
The CRV is the part that I think is often most overlooked on sequential setups, and how its operated. Because it is a plastic Denso diverter valve, its operation is different to an aftermarket piston-type BOV, and I'm led to believe that originally the CRV has a different opening kpa pressure rating to the factory BOV (despite them both looking identical) but I think Mazda uses the same part for either BOV or CRV these days.
If the stock plastic BOV can leak, and people are so quick to want to swap them out for some perceived reason that an aftermarket BOV is "better", then it makes you wonder about those people who run modified sequential or BNR's and run more boost. Is the stock CRV up to the job?
I dont see the actuation system as being that complicated really. It surprised me that the Supra system's prespool of the secondary turbo is not as well refined as the REW, in that it does not vent, and the ECU does not control surge, like the Mazda system can. Granted, the Mazda system is not controlling it based on real time data. Its opening/closing the CRV based on some predefined limit by the engineers of how long to run the secondary in surge without burning it out. The stock ECU must have a set time or something, maybe in conjunction with some other input signal, to decide when the CRV is open or closed.
Just rambling to myself, trying to get a handle on it all..
The CRV is the part that I think is often most overlooked on sequential setups, and how its operated. Because it is a plastic Denso diverter valve, its operation is different to an aftermarket piston-type BOV, and I'm led to believe that originally the CRV has a different opening kpa pressure rating to the factory BOV (despite them both looking identical) but I think Mazda uses the same part for either BOV or CRV these days.
If the stock plastic BOV can leak, and people are so quick to want to swap them out for some perceived reason that an aftermarket BOV is "better", then it makes you wonder about those people who run modified sequential or BNR's and run more boost. Is the stock CRV up to the job?
I dont see the actuation system as being that complicated really. It surprised me that the Supra system's prespool of the secondary turbo is not as well refined as the REW, in that it does not vent, and the ECU does not control surge, like the Mazda system can. Granted, the Mazda system is not controlling it based on real time data. Its opening/closing the CRV based on some predefined limit by the engineers of how long to run the secondary in surge without burning it out. The stock ECU must have a set time or something, maybe in conjunction with some other input signal, to decide when the CRV is open or closed.
Just rambling to myself, trying to get a handle on it all..
08-15-12, 10:04 PM
#34
The CRV is the part that I think is often most overlooked on sequential setups, and how its operated. Because it is a plastic Denso diverter valve, its operation is different to an aftermarket piston-type BOV, and I'm led to believe that originally the CRV has a different opening kpa pressure rating to the factory BOV (despite them both looking identical) but I think Mazda uses the same part for either BOV or CRV these days.
If you go by the service manual procedures, they are slightly different.
If the stock plastic BOV can leak, and people are so quick to want to swap them out for some perceived reason that an aftermarket BOV is "better", then it makes you wonder about those people who run modified sequential or BNR's and run more boost. Is the stock CRV up to the job?
That's one CRV though. I imagine the air bypass valve is the same. It's possible for them to fail I'm sure but in that one bench test it seems to me like a good condition one will, for all intents and purposes, hold unlimited boost.
I dont see the actuation system as being that complicated really. It surprised me that the Supra system's prespool of the secondary turbo is not as well refined as the REW, in that it does not vent, and the ECU does not control surge, like the Mazda system can.
Granted, the Mazda system is not controlling it based on real time data. Its opening/closing the CRV based on some predefined limit by the engineers of how long to run the secondary in surge without burning it out. The stock ECU must have a set time or something, maybe in conjunction with some other input signal, to decide when the CRV is open or closed.
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