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Index > Engine/Drivetrain > Thread: Paxton Supercharger kit for a rotary???
Thread: Paxton Supercharger kit for a rotary???
wvoigt


Revvin Up
Posts: 75
posted September 08, 2009 09:21 PM

Paxton Supercharger kit for a rotary???

I just got a Paxton Supercharger kit for a 12a(used).It looks like it could fit a 13b with a couple of minor changes? Can anyone tell me more about this kit?Is a Dellorto 48 large enough?

Thanks
Bill
San Diego
P.S. Anyone have anything to trade at seven stock?

____________
1974 Repu
1973 Courier
1989 Car Dolly

       
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sparky


Redlining
Posts: 299
posted September 08, 2009 10:12 PM

Hi Bill,
Did a little research. The supercharger is a Nelson Paxton belt driven turbo. They are no longer available. Found some info on Nopistons.com. If you install be sure you go with an air/fuel meter to monitor exhaust gas. One guy was getting 17 psi boost and 210 RWHP. This setup was used on 2nd gen rx-7 and it was recommended to increase fuel injector size. The Dellorto DHLA 48 will match the existing Weber DCOE 45 flange, but the 48 most likely is undersized. You really need to talk someone who has experience with this. Too much power to send to 1 wheel. Gotto go with the Torsen upgrade.

       
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repumax


Redlining
Posts: 427
posted September 09, 2009 07:32 AM

Nice find Bill. I'll trade you 2 fenders, a hood and a front clip for the supercharger.
____________
1974 Mazda Repu
1986 Yamaha RZ 500
1988 Yamaha YSR 50
1991 Suzuki RGV 250
1992 Yamaha TZR 250 SP
1996 Aprilia RS 250
2003 Ford F-450 6.0 Diesel
2004 Mazda RX8
2006 Yamaha Banshee
2014 18' Eclipse Toy Hauler

       
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Brad


Rotorhead
Posts: 1672
posted September 09, 2009 03:46 PM
Edited By: Brad on 9 Sep 2009 15:53

I think a Dellorto could feed it, the Camden kit uses a DCOE. Keep the same 39mm chokes that is in it for now, increase fuel lines from tank to carb to 3/8". Carbs w/forced induction need a rising rate fuel pressure regulator. Put a pressure gauge in the truck cab. Wideband required.

Increase oil pressure to 90psi to move oil faster and help cool the rotors, consider a thicker radiator as overheated apex seals tend to warp or break. As do apex seal springs. If you go over 5psi use low compression rotors. It needs a BOV and water injection helps. I don't know what to do about the timing issue w/o engine management (Megasquirt). Hopefully you have the bigger pulley to slow the blower's rpms.

Racing Beat's old catalog says 9.4:1 compression ratio is a major problem, use low compression rotors. But the 6 port setup helps it breathe, and use the oil injection to the rotor housing surface. Doubling oil injection rate helps with apex seal erosion.

http://www.rx7club.com/showthread.php?t=840421&highlight=supercharge
http://www.rx7club.com/showthread.php?t=755424

Don't take the supercharger over 3800rpms:
http://www.rx7club.com/showthread.php?t=800695

quote:
Quote from rotarygod regarding the Paxton:

You can't buy those anymore. Any you do find will have to be used. There were some design issues with the original kit. The sc pulley was too small causing the blower to overspeed. The solution of course is to use a larger sc pulley which also reduces boost. That kit also has no bov. Easily remedied. I'd personally use one that is from Vortec and then plumb it back into the intake side of the sc. They have a unit which is not only a bov but also a bypass valve depending on load level.

Those kits did not have any kind of engine management. They only had the rising rate fpr. It came preset and the owner was instructed to back off 5* of timing on the cas. Of course this also hurts power everywhere at every load as well. The hope was the the rich mixture and the slightly lowered timing would result in no detonation yet still have a performance benefit. It had it but admittedly not nearly what would be considered optimal. There is power being left on the table without ecu tuning. Those kits typically dyno'd 210-215 or so. Not that bad for no tuning, no intercooler, and only about 7 psi or so. Then you had the issues below.

You had the blowers themselves. Those were very old designs. The compressors were very inefficient by today's standards with their straight blades. A good 10-15% lower in effiency than modern units. Their drive systems were also inefficient. It takes alot of effort to spin those old things. They were not belt or gear driven. They were friction drives. Imagine ball bearings compacted together so tightly that the force or friction between them moved the others when one spun. That's basically how those work. More or less. So now we have a less volumetrically efficient and more mechanically parasitic blower design. Still pretty decent numbers considering all the things going against it. Compare that to a TII at the same boost! I'd love to see a more modern centrifugal such as a Vortec which is less parasitic and with a higher VE combined with proper ecu tuning. I'll bet it could be pretty nice.

It's no wonder so many rotary people hate superchargers. They've only ever seen 2 designs. The old Paxton units suffing the issues I just described and the Camden roots blowers which are the oldest most antiquated and least efficient of all blowers, even roots style. Throw a good sc on a rotary and I'll bet many people would change their views of superchargers a little bit. There will always be the debate over turbos vs supers of course but at the end of the day the only real answer to the argument is "it depends". Everything has it's place, including superchargers.

       
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