Rotrex Superchargers
06-07-10, 10:02 PM
#1
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Rotrex Superchargers
Since I kind of took over another thread with questions, I figured I would start a new one.
These new Rotrex chargers are starting to look very interesting.
My posts from the other thread
These new Rotrex chargers are starting to look very interesting.
My posts from the other thread
I've been snooping on some compressor maps with the Rotrex.
http://www.rotrex.com/Home/Technolog...ical_Data.aspx
Seems like the C30-94 would be a realistic 400whp but with not a lot of room to grow.
Or you could go with the C38-61 and spin it lower (80,000rpm) and flow 49lb/min at a 2.0VE (15ish PSI) but have room to go to a smaller pulley and up the power if you wanted to go WI.
The bracket seems very simple to make looking at Monster Garage's pics.
The thing I love about the idea of this, is the low low charge temps, lower EGT's, the Rotrex with it's planitary gear drive will have very little load on the engine at low RPMs.
And the fact that no one does it!
I also own a turbo miata, and there are a few Rotrex kits for them now which is what got me thinking of doing this on the FD. Everyone who's driven one says it feels like a big V6 in a miata. I can imagine it feeling like a BIG V8 in an RX7 with a properly sized charger.
http://www.rotrex.com/Home/Technolog...ical_Data.aspx
Seems like the C30-94 would be a realistic 400whp but with not a lot of room to grow.
Or you could go with the C38-61 and spin it lower (80,000rpm) and flow 49lb/min at a 2.0VE (15ish PSI) but have room to go to a smaller pulley and up the power if you wanted to go WI.
The bracket seems very simple to make looking at Monster Garage's pics.
The thing I love about the idea of this, is the low low charge temps, lower EGT's, the Rotrex with it's planitary gear drive will have very little load on the engine at low RPMs.
And the fact that no one does it!
I also own a turbo miata, and there are a few Rotrex kits for them now which is what got me thinking of doing this on the FD. Everyone who's driven one says it feels like a big V6 in a miata. I can imagine it feeling like a BIG V8 in an RX7 with a properly sized charger.
Here's another thing I was thinking. Most people don't boost with a turbo past 15PSI or so on pump gas. One would think that this is because the intake charge temps are a lot hotter.
With a rotrex, if you were boosting a max of 15PSI, the only time you're seeing that 15PSI is at redline since boost comes on in a linear fasion.
So... that being said. Could you run say... 18-20PSI on PUMP gas with a Rotrex?
PS... Can someone who knows more about compressor maps take a look at the link I posted (in the PDF files) of the C30-94 and the C38-61 and throw your input in.
With a rotrex, if you were boosting a max of 15PSI, the only time you're seeing that 15PSI is at redline since boost comes on in a linear fasion.
So... that being said. Could you run say... 18-20PSI on PUMP gas with a Rotrex?
PS... Can someone who knows more about compressor maps take a look at the link I posted (in the PDF files) of the C30-94 and the C38-61 and throw your input in.
Yes... looks like someone has done what I'm in the process of doing. Just you wait you supercharger nay sayers. The ROTREX is the new wave of centerfugal chargers. Low parasitic load, ridiculously low charge temps and a powerband like a big V8.
I just wish someone has a bracket already for the Rotrex on the FD.
bump.
I just wish someone has a bracket already for the Rotrex on the FD.
bump.
06-07-10, 10:51 PM
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On a twin screw or roots supercharger, yes. These are what most people think of when they hear the word "supercharger".
Rotrex superchargers are centrifugal basically a turbo compressor wheel/housing attached to a drive gear that is run off the crank. Max PSI @ Max RPM.
Example... (on a Miata)
http://www.youtube.com/watch?v=Vh1o9275VyM
Rotrex superchargers are centrifugal basically a turbo compressor wheel/housing attached to a drive gear that is run off the crank. Max PSI @ Max RPM.
Example... (on a Miata)
http://www.youtube.com/watch?v=Vh1o9275VyM
06-08-10, 08:03 AM
#4
You should try contacting Atkins Rotary:
http://www.atkinsrotary.com/index.php?pag=7
They've had success for years supercharging rotaries. I don't know if they've done any 3rd gens, but I know they've done many of the other 2 generations. They never post info about supercharging on the forum as in the past it always started arguments. However, they've always helped people offline. I have no idea if they've started using any of the newer superchargers as of yet.
http://www.atkinsrotary.com/index.php?pag=7
They've had success for years supercharging rotaries. I don't know if they've done any 3rd gens, but I know they've done many of the other 2 generations. They never post info about supercharging on the forum as in the past it always started arguments. However, they've always helped people offline. I have no idea if they've started using any of the newer superchargers as of yet.
06-08-10, 09:31 AM
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I have thought about supercharged rotaries in the past and ive had a few concerns for them. First many of us stay out of boost on newly started/ cold engines. I personally attempt to stay out of boost until it is fully warmed. Wouldnt it be bad to supercharge the rotary as regardless of whether it is hot or cold you are still forcing the same boost into the engine at the same rpm?
I am more interested in how well rotaries can handle superchargers. Any ideas on this subject?
I am more interested in how well rotaries can handle superchargers. Any ideas on this subject?
06-08-10, 09:02 PM
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Well I've been in talk with Monster Garage who made the one in the thread. They used a C30-94 and ran it off the waterpump/alt pully. The bracket looks simple enough to make. 1 week and I'm ordering it and going to give er a go.
We'll see.
We'll see.
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06-08-10, 09:03 PM
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regarding the issue with the no boost on cold start issue, why not mod the sc with an electric clutch that ties into the coolant thermosensor and engages when the engine reaches operation temps? It may not be easy, but considering what you'll need to install the sc to start with it shouldn't be too difficult.
06-08-10, 09:15 PM
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I have thought about supercharged rotaries in the past and ive had a few concerns for them. First many of us stay out of boost on newly started/ cold engines. I personally attempt to stay out of boost until it is fully warmed. Wouldnt it be bad to supercharge the rotary as regardless of whether it is hot or cold you are still forcing the same boost into the engine at the same rpm?
I am more interested in how well rotaries can handle superchargers. Any ideas on this subject?
I am more interested in how well rotaries can handle superchargers. Any ideas on this subject?
06-08-10, 11:38 PM
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C30-94
According to the thread that explains compressor maps, the author states that a 13b wants approx 49lbs per min at 15PSI (2.0 Pressure Ratio). That works out to about .39kg per second. 50lbs per min = 375 rotary wheel HP. X 1.10 (for ported motor) that puts me at approx 412 rotary WHP.
This is the smaller of the two Rotrex I`m looking at, how would someone who knows more than I do think of this map. With this one, to flow my goal of lbs per min, I would be spinning the rotrex close to it`s suggested MAX rpm. So not much room to grow if I ever choose to go with WI and want to up the boost.
Here is the larger `C38-61`
It dosen`t nearly come close to maxing out at 2.0 PR but will I have slightly worse spool... hrm...
According to the thread that explains compressor maps, the author states that a 13b wants approx 49lbs per min at 15PSI (2.0 Pressure Ratio). That works out to about .39kg per second. 50lbs per min = 375 rotary wheel HP. X 1.10 (for ported motor) that puts me at approx 412 rotary WHP.
This is the smaller of the two Rotrex I`m looking at, how would someone who knows more than I do think of this map. With this one, to flow my goal of lbs per min, I would be spinning the rotrex close to it`s suggested MAX rpm. So not much room to grow if I ever choose to go with WI and want to up the boost.
Here is the larger `C38-61`
It dosen`t nearly come close to maxing out at 2.0 PR but will I have slightly worse spool... hrm...
Last edited by bc_fd3s; 06-08-10 at 11:42 PM.
06-10-10, 10:43 PM
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OK, I did a few CFM calculations on the C38-61 compressor map.
8psi =1.55 Pressure Ratio
545 CFM
38.19lb/min = .29kg/second
60,000 blower RPM
320 whp
12 PSI = 1.8PR
632.6CFM = 44.33lb/min = .335kg/second
372whp
70,000 blower rpm
And it seems like this particular blower will be close to maxing out around....
20PSI = 2.4PR
843.39CFM
59.1 lb/min
.44kg/sec
496whp
87,000 blower RPM
So basically... I'm going to be going with the C38-61. I don't plan to run more than 14-15PSI. But realistically I'll run 12PSI on the street on pump gas.
But it's nice to know that if I ever want to run water injection, I can up the boost to 21PSI and break the 500whp mark or there abouts.
8psi =1.55 Pressure Ratio
545 CFM
38.19lb/min = .29kg/second
60,000 blower RPM
320 whp
12 PSI = 1.8PR
632.6CFM = 44.33lb/min = .335kg/second
372whp
70,000 blower rpm
And it seems like this particular blower will be close to maxing out around....
20PSI = 2.4PR
843.39CFM
59.1 lb/min
.44kg/sec
496whp
87,000 blower RPM
So basically... I'm going to be going with the C38-61. I don't plan to run more than 14-15PSI. But realistically I'll run 12PSI on the street on pump gas.
But it's nice to know that if I ever want to run water injection, I can up the boost to 21PSI and break the 500whp mark or there abouts.
06-11-10, 01:06 AM
#12
isnt the whole point of using a S/C to get a hell of a lot more down low? No offense at all because i'm a lover of people doing things different... but if i'm understanding correctly isn't the rotrex just a belt driven turbo? I feel like you might as well just go turbo with a 35r rather than have the rotrex. 1 psi at 1000 rpm doesn't sound to much better than an efficiently matched 35r.. correct me if i'm wrong. Anyone played around with using a roots style S/C and using it to feed a larger turbo?
09-10-10, 09:21 PM
#19
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And, to date, turbo RX-8s hold records for the most horsepower AND torque, and power under the curve. I think the max torque any Pettit S/C RX-8 has put down is 190ft lbs (stock is 160ish), while I put down over 320ft-lbs with a turbo.
09-10-10, 11:18 PM
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It was not designed to be a world beater.
Last edited by T-R-C; 09-10-10 at 11:36 PM.
09-11-10, 08:23 AM
#22
I really would question having lower AIT's. Pressure change = increase in temperate whether its through an exhaust driven compressor or a crank driven compressor. You may see a small difference due to the location of the compressor housing but beyond that you will see similar temps.
09-29-10, 05:22 PM
#23
https://www.rx7club.com/build-threads-293/well-rotrex-supercharger-has-been-ordered-921875/
I just bought one if anyone is interested and maybe I'll be making kits later on
I just bought one if anyone is interested and maybe I'll be making kits later on
09-29-10, 05:35 PM
#24
i think what most people mean by lack of torque is the lack of throttle response with a turbo, out of boost at low RPMs they are dogs, a supercharger will improve that respect.
this belt driven "turbo" will probably be more responsive than an exhaust driven turbo. but is it more efficient than a turbine driven turbo? at higher HP levels i doubt it.
this belt driven "turbo" will probably be more responsive than an exhaust driven turbo. but is it more efficient than a turbine driven turbo? at higher HP levels i doubt it.