9:7:1 rotors run n/a with fd block
 

Im wondering what modifications would need be needed to run an fd block as n/a using 9:7:1 rotors. I am only asking about what modifications would need to be made to the shortblock itself (housings, etc.) to get this to work, not about computer, injectors, etc.

open engine and switch rotors.

The counterweights have to be balanced for the rotors - either find front and rear counterweights that match the rotors or have the assembly balanced.

Also, the FD's intake setup is optimized for a turbo, and it's really not the best for non-turbo use. Not to mention you'll have a hard time making any appreciable power, even with high compression rotors. 160 to the ground would be good, 170-180 would be phenomenal. Go see what 2nd gen NA guys have done trying to make power.

Any reason you're asking this?

Dale

on 4 psi I made 262...

I was wondering what my engine would make with 0 boost?? Probably an expodential decrease in power as you decrease boost pressure from that point.

Good Question Dale?!?!?! Why run a REW block N/A? mpg and life?

I like the idea of boosting it. With proper tuning and some goodies...you can make good power with not so much boost. And have it come on like a light switch.


WWDD
hmm...what would dubulup do?

very efficient IC
fail safe tuned WI (maybe a little meth)
Fuel cooler
excellent IAT and Coolant temp, timing/fuel correction maps

I'd say 400rwhp around 12psi on a nice single in the sweet spot. finding the right turbine housing to compressor housing might take someone more educated than me...

a guy out here in pigeon forge, tn made some rather impressive power using na rotors in his 3rd gen. hes running a gt35r and of course a good bit of race gas. i dont know what kind of power he put down as we didnt do any dyno pulls for the BDC tuning event here in mid ten this past december. everyone said it was a relative beast.

and about the balancing. . . you should only have to use the corresponding counterweight from an auto FC in conjunction with a lightweight aftermarket flywheel.

The weights are the same Dale. You must have the S5 NA rotors confused with the S4 NA rotors. S5 NA 9.7 rotors weight the same as Fd and 20b rotors. teamafx, just make sure your rotors are within two letter weights of each other. I got lucky and found 3 "C" weight 9.7 rotors to put in my 20b. :D

I thought just S5 TII were the same as 20B and S6 rotors? Or are they different in compression but still same in weight?

yes. FD, 20b, s5TII are all interchangable 9.0:1's

but you have to pay attention to the weight letter stamped on the sides of the rotors

At least for the S5 TII and S6 rotors, they aren't the same part, but they do have the same weight and compression ratio. That makes them interchangable, AFAIK.

-Max

That I'm aware of also. I was more worried about this comment

all 89+ rotors weigh the same, 9.5lb, weight letter codes aside.

No need to worry about my comment. I was correct. I don't try to post a whole bunch of BS on the forum if I can help it.

http://www.mazdatrix.com/FAQ/ROTORWGT.HTM

and the bearings need to be changed the FD bearins have a deeper groove

Personally, I wouldn't mix and match counterweights - I'm just not comfortable with that. It would probably work, but I'd want to have a known matched set.

Definitely wouldn't want a new expensive motor shaking itself apart :).

Dale

thats what we do when we put a lightweight flywheel on our cars. . . auto counterweight.

How about Renesis rotors, would they fit also? They've got a 10:1 compression ratio, and better seals from what I've heard.


-s-

any 13b rotor fits into any 13b engine...with the proper counterbalance, and in the case of the renesis rotors, you have to do a bit of milling to the apex seal slots (so I have been told, as I have not used any yet). The expense would not be worth the extra ~3hp that the 0.3:1 CR increase would likely net on an NA application. The power gain in the renesis is due to port layout, intake manifold design, and ecu programming.

The only real advantage to the renesis rotors is they are cheaper to purchase new and their lighter weight for higher revs. However by the time you mill the apex seal grooves to fit regular 2mm apex seals, you would have spent about the same amount of money as compared to purchasing new 9:7 rotors that need no modification. Renesis apex seals aren't designed to travel over the PP exhaust of the older engines as one person who experimented already found out. The seals warped.