rx7 single turbo

two small sequential turbos will provide smoother, faster power but a single phat turbo will produce more power albeit peakier...
 
thefullcollapse said:
two small sequentials?

i was under the impression one is bigger than the other


Possibly, I don't know RX7s inside out but i'd be fairly certain any single replacement will be a fair bit larger than either sequentials.
 
Think about it this way.. half exhaust gases going to a small, and half to a big turbo = little lag due to small turbo, and good power thanks to big turbo.

Now think all exhaust gases straight through one turbo = more power BUT due to more gases through one turbo, reduced lag (ish)

Basically more power without sacrificing too much driveability I think.
 
thefullcollapse said:
no no no.

isnt it all into small, then when the revs are high enough all into big?

I'm not sure, but seeing as most turbos only have a small penny valve, I can't see that working.
I know on the Skyline GTR, 3 cylinders go to a small turbo, and 3 to the bigger turbo. Maybe the RX7 is different?
 
usually if people go single turbo then they are running monster power and they need all the engine's exhaust gasses to run a football sized blower!
 
serv_2.jpg


Skyline turbo arrangement
 
paradigm said:
But the rotary engine doesn't have 2 banks of 3 cylinders with which to do that.


Has two rotors though, which I assume will have their own 'set' of exhaust gases...
 
Looks like the engine has 3 exhausts ports that discharge out the top of the engine into a manifold which splits into two and the air is equally shared between both turbos.

Using a single turbo will mean you can spin up a bigger one faster, bigger turbo - more power, if you upgrade the two smaller turbos to bigger units they engine won't flow sufficient exhaust gases and the turbos will stall.
 
Wikipedia said:
Sequential Twin-Turbo refers to a set up in which the motor can utilize only one turbocharger for lower engine speeds, and both turbochargers at higher engine speeds. During low to mid engine speeds, when available spent exhaust energy is minimal, only one turbocharger (the primary turbocharger) is active. During this period, all of the engine's exhaust energy is directed to the primary turbocharger only, lowering the boost threshold, and increasing power output at low engine speeds. Towards the end of this cycle, the secondary turbocharger is partially activated (both compressor and turbine flow) in order to pre-spool the secondary turbocharger prior to its full utilization. Once a preset engine speed or boost pressure is attained, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely. At this point the engine is functioning in a full twin-turbocharger form, providing maximum power output. Sequential twin-turbocharger systems provide a way to decrease turbo lag without compromising ultimate boost output and engine power. Examples of cars with a sequential twin-turbo setup include the actual Volkswagen Golf (Rabbit) MK5 GT 1993-2002 Toyota Supra Turbo (JZA8x), the 1992-2002 Mazda RX-7 Turbo (FD3S), and the 1986-1988 Porsche 959, and some older Audis, including the 1997-2002 S4 (B5) and 1997-2004 A6. With recent advancements in turbocharger design, sequential twin turbo systems have fallen out of favor because they are seen as unnecessarily costly and complex.
 
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