Like the title says...what are the differences between the FD rotor housings and the FC TII rotor housings?

 

No coolant passage to the manifold (for the turbo coolant feed) on the FD rotor housings. minor changes in spark location (timing). The FD housing's chroming process is much better than the FC. Maybe a minor difference in the exhaust port, but I don't think so.

Hope that helps.

 

Yea I've been told several times that they are interchangable, except of course for features mentioned by duncan.

They are superior to the FC housings, and IMO are worth the extra money for longevity reasons.

 

what about cosmo?

 

I was asking this to really find out if they could be used for rebuilding an s4 tII engine.
Anybody ever done this? Ever used fd housings with s4 tII rotors ?

 

Guys in Japan do it all the time, benefit of the s4 t2 rotors is lower compression, allowing them to run greater amounts of boost with less fear of detonation.

--Fritz

 

I have fd rotor housings on my TII engine build.
They swap no problem.
JDuncan got all the differences right.

 

Yes. But if you're using a stock turbo you'll have to get creative for a coolant feed.

 

right now it's an 88 motor just pulled apart with 2 bad housings. I know I'm gonna use s4 rotors...however it will be an s5 turbo. I was asking just in case i found a good set of fd housings before I found a good set of s4 or s5 housings. So any of you guys that have used fd housings...what did you do to resolve the coolant issue?

 

Actually..you can just machine out the plug and use them like a tII housing. Its really easy.

 

i believe guys do this with NA housings too.

 

.

 

They're all the same. As long as the displacement is the same, then the housing should be the same. It wouldn't make sense for mazda to spend more money manufacturing a different housing for an engine, it saves them machining parts and of course manufacturing costs to create just one size of housing.
Thats why the NA's and FD's have the plugs on the housings, cause they're all from the same cast, just modified with plugs depending on what kind of car they are going into.

In other words, Cosmo 20B housings should work no problem.

 

not trying to rain on any parades, but there are several differences in the castings on the rotor housings and the side housings from model to model.

the cosmo rotor houseings are basically worthless due to the size of the exhaust inserts, ya you can change them out, but if you are looking at used houseings to replace your S4 then go for the FD. the best chrome, the best inserts, will have to drill out the spot for the coolenat flow, no problems.

the cosmo housing would require changing the inserts, which means either getting a set of FD houseings anyways, or using the inserts from the S4. since you are doing a rebuild why waste time and money just get the FD housings.

kenn

 

so a stock cosmo engine isnt good or what

 

The only thing bad about a 13bcosmo engine is that it doesn't have 3rotors

 

sweet...thanks for all the info guys
Gonna look into finding some fd housings.

 

Put a big *** oil cooled turbo on the side of the motor.

 

Worked for me.

 

Eeees Ok meyann but its butthole is to puckered up! if it had a looser butthole it would run faster meyan.

Like I said the rotor houseings exhasut port is crappy on that motor, where it shines is the intake ports, its ports are like ginormous and taper down nicely to increase the speed as it exits into the rotor housing, so you really get a good intake charge and then the rotor hoseing screws the pooch. mazda wanted people to buy the 3 rotor, if they made the 13b model put out similiar HP then your average consumer would say "**** its only got a couple more HP why not buy the cheaper 13b model" they wouldn't understand the difference the torque makes.

wanna make a killer engine for the FC? take the cosmo 13b irons, use FD exhaust housing with FD rotors, and journal shaft. thats the hot ticket for stock parts, port it and get more.

kenn

 

what if u just port the Cosmo engine, then the "butthole" wont be plugged up/

 

I've heard that the FD housings moved the spark plug location a little.
---
Anyone that can confirm this, or come up with the reasoning?

 

I thought I already stated that difference. Consider it confirmed.

 

Cant you just remover the exhaust sleeves and port the cosmo housings and have a similar/better one that a REW housing. It only makes sense.