zoil

hello i have a 91 rx7 and i have been told i have a 6 port motor. how do i find out if its right ? whats the big difference in the 4 port to the 6 port? is one better then the other?

i am planning on supercharging my rx7. it is a n/a motor in there now

Black Knight RX7 FC3S

iTrader: (7)

all natural aspirated engine in the FC are 6 port. Only the turbo engines are 4 port.

zoil

ok but will the 6 ports be a problem with a turbo or supercharger? will it make more power? is there a difference in the porting ?

gerald m

Try the fsm's there are lots threads on the subject

Black Knight RX7 FC3S

iTrader: (7)

There shouldnt be a problem boosting it, unless you are looking for crazy power.
It will make more power because of the higher compression and more air being crammed in because of the 5/6th ports. As for the ports, the n.a primary and secondary(?) ports are smaller then the turbo ports, but the 5/6th ports makes up for it.

zoil

I'm planning on a large street port and half bridge port with a 9" supercharger 650cfm Carb. The website for the supercharger says compression needs to be 8.5to1 to run 5lbs. I know stock for my motor is 9.4to1. I need to lower it to bout 7.5 to run 10lbs of boost. I'm trying to make 350hp to 450hp

RotaryEvolution

iTrader: (30)

the intake side of the 6 port motors is actually already more than sufficient in stock form, the intake manifold itself will be a slight restriction depending on power levels.

the largest restriction in the 6 port motors is the exhaust sleeve in the exhaust side, if you're going to force induct the engine then that should be the first to go, but also requires full teardown of the engine.

zoil

The supercharger it self has a new manifold. So should take care of that. Thanks for the great info. Think ill still do the port since I'm tearing the motor down. What's a safe compression after boosting the motor?

PvillKnight7

iTrader: (16)

9.4:1 cpr is fine for boost. The FD rx-7 has 9.4:1 cpr.

RotaryEvolution

iTrader: (30)

depends on your tune and boost level. lower compression is safer but less responsive, higher compression requires more safeguards like higher octane fuels or AI and conservative tuning.

correction as the FD is slightly lower than that, .4:1 CR does make a bit of difference, in this case it is .7:1CR lower than the rather extreme CR of the S5 n/a.

non turbo S4: 9.4:1
turbo S4: 8.5:1
non turbo S5: 9.7:1
turbo S5/6: 9.0:1
RX8: 10.0:1

RX8 owners have boosted engines successfully even though they have issues with the side seals soaking up too much heat and warping, not an issue you have to worry about with the peripheral exhaust on the mid year 13B engines.

the '91 engine referred to here is a 9.7:1CR engine, it will require considerations before just cramming air into it. i would also suggest a more durable seal like ALS, goopy or rotary aviation. you may also want to look into a stud kit or dowelling the motor, if the timing isn't spot on or retarded a bit then preignition will twist apart a high compression engine like a twizzler.

cheapest alternative would be to run the 8.5 or 9.0CR rotors. the 9.0 will work with your rotating assembly, the 8.5:1 rotors would require the series 4 front and rear balancers.

Aaron Cake

iTrader: (1)

You're referring to the Camden supercharger? If so, you won't be happy with it and you'll never make even close to 350HP - 450HP. A 650CFM carb also won't support that power on the rotary, and with that bridgeport on the huge port area of the 6 port irons, the car won't drive very well below 5000 RPM either.

My advice is to ditch the bridgeport and supercharger, install the TII intake manifolds, then bolt on a TII GT35R turbo kit with the appropriate fuel mods and full standalone. 350HP all day long.

84stock

iTrader: (5)

As a long time camden user, I second that!

The 9 inch is actually too big for the 13b, the 650 would be too small, and after spending a ton of money you will never see over 250 rwhp.

Follow Aarons advice, get good seals, streetport it, start with a small turbo and you can upgrade from there.

zoil

thanks for the advice. if i cant make the power i want with a supercharger then ill just rebuild and stay N/A. everyone puts a turbo on a rx7 and i could do that at anytime but the supercharger just would be different and cool

bumpstart

use the modded t2 manifolds ( port matched suit the 6 p inlet ) add larger secondary injectors of 750- 1000 cc and add a highflow for around 300 rwhp at 14 psi
or add two more of the same injectors into the primary injector position
and chuck at it a a t04 and gate of your choice for the 350- 400 shoot

i personally run 6p turbo setups, have done for many years and my personal choice is to strip and rebuild it with a t2 centre plate ( G type ) and t2 housings ( no exhaust baffle wing ) and oil pump ( higher volume )
if you couple this to the correct TB ( type with cold start vac controlled delay secondaries ) and hook it up with a trick
you can gain a fair bit of the down low response back that is lost when you delete the aux valve control

zoil

Thank ill keep that I'm mind. I think ill see how much I can get out of a n/a build with the option of boosting the car