www•rx-7france•com ∞ Forum Francophone Mazda RX-7

Petite question aux connaisseurs :

quelles sont les différences entre les stationnary gears de FB/FC N/A/FC TII/FD/RX8 d'un point de vue performances, résistance et compatibilité ?

je m'explique, je vais re-ouvrir le 13B N/A de la caisse de drag pour le vérifier et le refaire en atmo (avec carbu ou injection, pas encore décidé) pour essayer d'en sortir des cv. j'aurai aimer savoir si les stationnary d'origines étaient suffisant et si il y avais des avantages (si c'est possible) d'en monter d'autres (meilleurs lubrification, plus solide etc etc ?)

sachant que j'aimerai essayer de faire un beau porting et une belle prépa pour prendre au moins 9000 trs

Hi, answer in English sorry.

FB, not hardened
FC S4 more than likely not hardened
FC S5 and FD S6-8 hardened gears (nitrided)
RX8 hardened gears, rear gear does not have oring groove like earlier engines, bearings are different too

13B-REW also has larger torrington bearings, so need to use matching stat gear, torringtons and fron counterweight. S5-S8 are the same rotating mass.

What are you trying to do?

thanks for the answer.

i want to do an engine with différents parts from Renesis engine and RX7 FC S4 engine, for make a natural aspired engine who can have High rpm and power.

i have an RX7 FC N/A engine and a RX8 192 HP engine.

I have MSD ignition system and dual WERBER 48 carburators and intake that match for S4 N/A 6 ports engine.

i woud like to use RX8 rotors and excentric, S4 6 port plates and houssing, RX8 flywheel.

you think it's better to use RX8 stationnary gears too ? (and maybe oil pump too ?)

i want to use the MSD ignition and weber carburetor because if the engine is not enought powerfull for the FC for trackday use, it will fit in the 818 for road use. so i want old school engine, no injection or electronic ignition.

Here are the stat gears, 12A, S5 turbo and REW from top to bottom:



REW uses grub screw to keep in place.

You can see the REW uses bigger torrington bearings here:



13 stat gear is also longer in the teeth:

You will need to use RX8 front counterweight as well. I suspect the RX8 uses the larger torrington bearings (I don't know) so you will need to use the matching stat gears.

RX8 rear stat gear is differnet to RX7 gears for sure. No oring groove and I think oil galleries are different.
RX8 eshaft is tapered on rear journal too.
RX8 rotors have small apex seals and side seal location moved too iirc. Watch out for your ports.

S5 NA rotating assembly is best option imho. 9.7:1 comp. No guess work.

Ok thanks, i didn't know for the side seal ! i will look for that.

otherwise, i can use only 13B houssing and all other part from RX8 engine.

i will need to make custom intake pipe for the carburetor and use the rx7 front cover for the ignition distributor fit on it.

and of course, custom exhaust header for the 6 exhaust port

i don't know if the rx7 NA distributor is ok for use on hight RPM, maybe it can be modified for that. or i will need to buy a competition distributor, i don't know if i can modify the masse in it for change / custom the ignition curve.

i will need help from people who know about it i think ^^

is the 192 HP engine is OK for this idea ? or is it better to take a 231 HP engine (better intake port ?)

I was looking for part on the net and i see that the water pump is include in the front cover on the rx8 engine, but i need a rx7 front cover for the ignition distributor.

the rx7 pump can be mounted on the rx8 front plate ? or i will need to have an electric water pump and build something for plug it on the engine ?

I think you're creating a lot of extra work. Just build an FC NA motor. Parts are all still available from Mazda.
Renesis is a big compromise.

S2/3 electronic dizzy curve modification is well documented. My RX4 style 13B BP runs a stock S3 dizzy set to 24 BTDC @ 4000rpm leading.

you are right, it's a little expensive and lot of works for juste some HP more.

i will build a good 13B S4 with big porting and nice part on it !