i am currently rebuilding my fd3s engine and after closing the short block i realised that i have inverted the front and rear rotor housing. Did not notice any difference in the shape or construction of the housings and if i remember well i had read somewhere did there is no difference for the fd engine's housing but i'm not sure. Can anyone inform me of what difference there is between the two and what problems might arise if these are left they way they are assembled.

Far as I know there is no real difference and shouldn't be a problem.



I'm hoping you inspect the inside of the housings and replaced the apex seals??

the air injection passages are different front to rear, they are mirror images. so if you swap them round, the air pump is blocked off, and the car will not pass smog.

Yes inspected the housings . Actually i bought a used set from a low mileage jdm engine which are in very good condition since the original had blown a seal and was unusable. Most of the engine parts are new like all seals and gaskets and bearings.



Do the rotor housings have any connection to the smog pump ??? Have never noticed any of these or read about them anywere. Doesnt the smog pump only have connections to the precat and exhaust???

for some reason this is a big secret, but its in the book.



from idle to ~2500 rpms the air pump air is injected into the exhaust ports, it goes thru the center housing and into the rotor housings. you can drill the rotor housings to work backwards, the 12a's are like that from the factory.



the split air pipe to the cat isnt used for much, in fact you can remove it and the car will pass smog just fine

ah, I didn't know that. Thanks for teaching me something new.

Forget to tell that my car is a japanese model and does not have the EGR valve. Does the issue still hold?

Basically the answer is that if you dont run your emissions equipment then having the housings swapped doesnt matter.







My FD never passed without the split air pipe. Connecting it reduced my emissions by 25% or more. Who knows, maybe something else was wrong with the car but it ran great and that cat lasted 80k miles or so.

this is for the air pump air, i think the egr goes to a different place, but since the erg oriface is like 2mm it really doesnt matter.... its just eye candy

Can these be drilled when the engine is assembled ? If so do you have any pics to indicate which holes have to be drilled . Tried to inspect the housings but still can't figure out which holes you are talking about