Like the title says.

The car is an S4 Turbo II, however, due to the overall better quality of the housings, I ordered two S5 rotor housings (front and rear, obviously.)

I called and spoke to Mazda Motorsports today, however, and they informed me that the rear rotor housing is on back order, and it potentially may be weeks longer than anticipated.

Based on my research, I know that you cannot mix and match S4 & S5 housings due to the differentiation between spark plug locations, and I wouldn't want to use S4 housings anyway. But what about an S5 front rotor housing and an S6 rear? They do have the FD housings in stock.

If I'm correct, the FD rear housing does not have the coolant supply for the turbo that I will need, so I would have to tap into it.

My overall question, though, is can I use an S5 front rotor housing and an S6 rear rotor housing, turbo coolant supply issue aside?

 

yep, biggest difference is the lack of a coolant O Ring passage, ideally you'd use a front FD housing and Rear FC, that way you'd keep the coolant O Ring you need and remove the one your don't.

the other obvious difference is the exhaust manifold studs are longer on the FD, kind of a plus. the FD uses taller lock nuts, which also are better than the goofy lock tabs the FC uses (9YB1-01-001)

 

Unfortunately, the rear rotor housing is still on back order, I'm being told it could be weeks. With my appointment to drop my engine off at Rotorsports coming up in a little over a week, I'm not sure it will arrive in time, so I may indeed have to use an FD housing for the rear.

I've searched far and wide on the forums, but I can't seem to find a write up or process of anyone actually tapping the rear housing for the turbo coolant feed in a setup like mine. I believe Bryan from rotorsports when he says it's do-able, I'm just curious as to if anyone might know of a thread that I might have missed that shows it being done for curiosity's sake.

 

its pretty simple, although you need a mill. you need to mill the O Ring land, and then drill the hole for the water. if you look at your front housing its like that

 

Gotcha, that works. I trust him when he says he can perform it, so worst case, the biggest issue I'll have to deal with is the fact that the FD rear housing is significantly more expensive. Which honestly to me is better than not having a housing at all and waiting.