green 59

can any body tell me how much power can be got from a twin rotor naturally aspirated and still be smooth to drive on the road? cheers

Lynn E. Hanover

That would be a trick question, in that any answer could end up being wrong. It all depends on what you think smooth might be.



To many young people hanging out in a bar with Metalica blasting at 110 Db is just right. Others might find classical in the shop turned down low is just right (me).



So smooth is in the mind of the driver. The sputtering and jerking of a bridgeported 12A with a metal clutch leaving a traffic light might be a riot to me, but make you unhappy after a week or so.



I would think that smooth would be little to no porting in the primaries (center iron) and a medium street port in the secondaries (end irons) Maybe 60 degrees closing.



The best 12A street ports from years back when we were racing, was about 220 HP. That would be a wild *** port that eats side seals each weekend and needs rebuilt. All irons ported, no bottom end, power from 7,000 to 9,000 RPM.



A reliable street port with no side seal damage and a near stock center irons and a medium port in the end irons might get you up to 170 HP. But it will need to be reved up quite a bit to show it off.



The engines have poor low speed torque, and porting does nothing to improve that.



The other problem is that, how good it feels when you get done porting the engine depends a lot on how much power it had before you started. So an RX-3 with 115 HP stock feels like a dragster if you just replace the stock flywheel with a light aftermarket piece. An FD starting out at 255 HP will need some serious money to go enough faster to feel it in the lumbar support.



A lower rear end ratio and a light flywheel give you more performance for less effort. Unless the engine is apart anyway. Just smooth up the primaries, and do a (fill in the blank) street port on the end irons.



Lynn E. Hanover

green 59

thanks mate

j9fd3s

yep, lynn's on the money.



the later engines are in the 180-200hp range on mild ports, 180 can be done on the stock ports

heretic

Fuel injection cures many ills.



It's possible to make over 200hp with a decent street port 13B if everything else is decently sorted, with good drivability and a quiet enough exhaust.



Some people are reporting incredible gains with Renesis engines. They can't really be ported but manifold and header work reaps great dividends. That's my next step. I have standing orders with the local junkyards for a 6 port RX-8 engine.

j9fd3s

for a street type car its a much better option than the PP... which is alive BTW

dac

Disagree, Fuel Injection can't compensate for Massive Overlap from the Porting. Kinda like putting a Big Cam in a piston motor and saying Fuel Injection will make it IDLE. Just not going to happen.

j9fd3s

sure it is. you should see the speedsource rx8 run. 20b PP engine, it runs like a stock car. or the 787B

Maxt

Fuel Injection does a fine job on huge overlap motors.. The big kerfuffle with the pport was everyone said it couldnt be street driven because, it had to idle so high, hard to start blah blah blah..

I have had my efi p-port idling at 750 rpm. it likes 950 ish more, try that with a set of webers on a p-port and 20 mpg highway to boot. It starts off the key better than most stock rx-7's.

j9fd3s

so far my weber fed PP is way more tolerant of the mixture being way off than a stock port, so far