like it sais are the s4 and the s5 turbo rotar housing the same or what. also how can you what compression rotars you have because the guy that i bought the car from said that when the motor was rebuilt he put higher compression rotors in. He said that he didnt know that compreddion they were any help. This if my first rebuild and any help would be greatly appreciated.

 

As far as i know, the s5 and s4 rotor housings aren't interchangeable due to different timing on the trailing spark plug.

-Justin

 

o yea i i forgot to ask. How can i tell if it has been streetported because he also said he had that. And do they port the intake or exhaust or both on the sideplate or on the housing. thanks

 

The S5 13BT rotor housing have the spark plugs located lower on the rotor housings.
Go ask BDC about mixing and matching the rotors housings, since he's done it already.

It's hard to tell what compression ratio the rotors are unless you have both NA and turbo rotors in front of you.
You can tell S4 from S5 by *weighing* them.
S4 is over 10 lbs.
S5 is under 10 lbs.

Mazdatrix has a handy chart here:
http://www.mazdatrix.com/faq/rotorwgt.htm


-Ted

 

S5 rotors also have machined reliefs whereas S4 rotors have rough cast ones.

S4 rotors also have deeper pockets than S5 rotors do but unless you know you have a pair of both turbo rotors or n/a it can be tough to tell between all 4 different types of rotors.

 

ok well then can you use a 87 n/a for an 87 tii or what. and can i put n/a rotors in the tii. I know it is higher compression but with 3 mm seals should it be ok?

 

3mm apex seals has nothing to do with compression.
What are you trying to do?


-Ted

 

i have a good 87 n/a motor and a 87 tii motor with a bad rear rotor and housing. Just wondeing if i can use the n/a rotors and rear housing. With 3 mm seals then it should be reliable.

 

Yes, you can swap out the rotors and the rotor housing no problem.
Mechnically speaking, it's not a problem.
What you're effectively doing is increasing the compression ratio (significantly).
This is not recommended, unless you have a way to compensate for the increased compression ratio.
Are you trying to do this with the stock ECU? This is not recommended.
If you're running a stand-alone, then you can easily compensate for the increased compression ratio.


3mm apex seals do not increase "reliability", IMO.
Do you have some way of machining the rotors properly to take the larger 3mm apex seals?


-Ted

 

well i think that i am going to just go with tii parts but still get 3 mm seals. I have a friend that runs a machine shop and can wright the program for the cnc and machine the rotors. And am going to go with rotary aviation seals because i have heard only good things.

 

I'm really happy with my RA seals.. The only thing that I was annoyed with is their Viton (Sp?) Combuston O-Rings. I think ReTed posted links to a McMaster Carr O-Ring that he uses for combustion rings. I'd probably go with those if I rebuild again. Other than the RA kit is good!

I can't actually add anything else to the conversation.

 

well im am still wondering if you can just cnc the rotors for 3mm or is there a special mill that is needed.

 

The point is, you don't need 3mm seals. They are just a crutch for poor tuning IMO. There are several guys that run 2mm seals and produce tons of power.

Zach

 

thread resurrection but can I use a s5 TII housing on my s4 block?

 

You cannot use just one S5 housing and one S4 housing. You have to have two S5s or two S4s.

 

only in pairs, as mentioned.

 

there is a thread on here that i cant find at the moment where the guy measures the housings and there is no difference in the s4 and s5 housings

 

That's not entirely true. You can mix and match them but it's not advised as the leading plug location is slightly lower on the S5 and newer housings. I used to run a setup about 10-11 years ago that made a good amount of power (peaked at 424 on the dyno) that had a mismatched pair of rotor housings. I never knew until a couple years later. Didn't seem to be an issue in how the car ran, though.

If I were doing an engine today, I wouldn't use the mismatched housings.

B

 

i had an engine with mismatched housings that broke a side seal, i have yet to see any other engine do that and the reason was unknown still to this day as to why it broke aside from the mixed ignition timing locations in the rotor housings.

if you want to be super cheap and mix housings, it may work and it may not, may run well for a while or it may experience the same issue as i experienced with it. i may miss the opportunity to say "i told you so", so i'm doing it now.

that car was only making about 300 or so wheel horsepower on a smaller hybrid turbo. in non turbo applications it will probably be less noticable, but the combustion cycle IS different from one rotor to the other if you mix the housings.

 

the spark plug is visibly in a different place. however i think i remember the thread and he was looking at NON-USA S4 housings which actually do have the S5 spark plug placement.

so to recap.

the N326 and N332 rotor housings have different spark plug placement from the N350/N318/FD/cosmo rotor housings.

 

Can you run S4 T2 Irons & Rotors with S4 N/A housings?

 

yes.

 

Sweet because i am having a hell of a time finding T2 Housings for my T2 rebuild.

 

yes, all Jspec engines have S5/6 spark plug timing regardless of the series of engine. USDM S4 rotor housings are the only ones with unique plug timing with a smaller split between the plugs. it was before this thread was made that i figured that out the hard way with the side seal issue in a TII where the car already had a S4 jspec swapped in and i had to replace one of the housings.

 

hows this, Ideal in my case as I'm building an engine from S3, S4 na &bt, and S5bt parts would be since I'm using S5 housings would be to use S5 front hub and timing pulley. Will the timing pin on my GSL-SE front cover be in the correct location?