FI: Twin screw
 

I have read about roots type blowers being used. And, heard rumor about a twin screw? maybe.

But, my question is, what is the main downfall and problems associated with a twin screw setup? What are the major difficulties in getting one setup on a 13B?

I do a lot of autocross / daily driving. I was hoping to improve torque and lower RPM power.

I was thinking about a twin screw and a 4.3 or 4.88 rear.

My main goal is 0-100 speed. Could care less about anything after 100. not practical for daily.

Thanks.

running blowers on a rotory isnt really optimal. with the already low amount of torque made, the extra load from the charger pulley makes it more noticeable imo. not saying its a bad idea, but even piecing together your own kit is hard. if you do a little searching you'll find some guys that are runnings s/c's. you should talk to them.

I've been toying with the idea of a centrifugal SC setup. It'd certainly be easier to set up than to use a custom intake for the roots style. Of course, you still have the fuel/air mixture setup but that'd be there either way.

you should look into the camdem s/c's that atkins rotary sells.... i've seen 2 fc's in my lifetime that have this setup done RIGHT!

with the proper final drive ratio, tuning, and s/c size (they sell sizes from a 6" to a 12", measure in length front to back), the two i've seen one made 230hp and 250tq and another made 237hp and 260tq.

one of the men i talked to about their setup said that its not really and ideal setup for daily driving as the roots/eaton/twin screw superchargers create a lot of their own heat due to the fact that there is no heat exchange being done to control intake temps. which is what the tuning is there fore, yet on a decently rich tune, the car would dramatically have ill effects to fuel efficiency because the fuel is also used to cool the charge air.
their dyno graphs were pretty good considering torque was 150 by 2000rpm and stayed at 200+ until 5000rpm where hp took over. yet with the s/c being there, the engine wouldnt make much power past 7k. and both these motors were rebuilt with a mild street port on the intake with TII irons and not running exhaust sleeves(which made thins very loud)

IMO, if you were to go this route, some sort of secondary injection would be in order such as alky, meth, water or any combination of the two.

it is a great idea if there was someone who could do the research to actually make this a feasible project and not something that is more of a novelty than anything else.

i do love the sound a roots/twin screw blower makes when its in positive boost.. like a crying baby lol. and sounds just the same on a rotary, with the metallic exhaust sound of course it sounds a bit beastly

The only kits currently on the market are from Camden. They use an old style of Roots blower that is not very efficient, but the kit does work.
http://www.camdensuperchargers.com/

None on the market yet as far as I know.

- No kits are available
- Most RX-7 owners are broke and would not pay $6K for a kit anyway
- Used twin screw superchargers from other cars are the wrong size
- Nobody on this forum has successfully made a custom setup
- A new twin screw supercharger is expensive

Er, why don't you just save yourself a lot of time and trouble and simply sell your car and buy a TurboII? At least that way you could autocross in a lower class.

Anyone know what type of superchargers are on the speedsource rx8's?

I have run the camden for years now. It provides great torque and makes for a great daily driver. It does not however bring out the most of the rotary if you are looking at racing. To go with a twin screw, you'd have to fab almost everything, $$$$. As for centrifigal, same as turbo but you use the engine to drive it. Might as well go with a premium ball bearing turbo, this way there is a tone of aftermarket stuff from standalones to manifolds to ease installation and setup. You'd spend about $5000+ to get maybe 300hp from a twin screw fab'd setup, whereas a bb turbo with a good engine will net 400+