Well, after looking on Mazdatrix's website, it looks like the fuel filter was the same for the S4 and S5 models since it only had one listed for 86-92. Now, the O2 sensor looked to be different between the S4 and S5 models since they had two different ones listed. Was the S5 exhaust manifold different from the S4 exhaust manifold? I'm guessing that it was a better flowing design, since Mazda decided to change the intake setups also between the two series. If you guys know anything, I'd appreciate the help.

 

I had an extra S5 NGK oxygen sensor and checked to see if I could use it on my S4 just a couple weeks ago. The electric connectors for the oxygen sensors are different from S4 to S5, and the lead length is a little longer for the S4 (IIRC). Whether there are actual electronic differences in the sensor itself, I don't know. It may be that if you cut the connector off one, you could splice it on the other with no problems. (?)

 

Ah, ok. That would make sense why they are different part numbers then. I wasn't sure if the S4 and S5 maybe had different exhaust manifolds and that was the reasoning for using two different O2 sensors. I'm in the midst of figuring out what intake/exhaust setups I want to go with for my car, and that was my reasoning for asking about this.

 

Well, Mazdatrix only has the gasket listed, and they are two seperate gaskets, but the gasket looks the exact same between the series. Does anyone have a S4 and S5 exhaust manifold laying around?

 

http://www.mazdatrix.com/e6.htm

The series four has the hole for the EGR exaust gasses to enter the intermediate housing. See the two n/a gasket picutures in the url

 

I just took off my exhaust manifold (91 N/A) and replaced it with racing beat headers. The gasket for the manifold looked exactly the same for the headers as it did for the exhaust manifold. The only thing that i cant say for sure is that the manifold gasket for an s5 is the same for an s4, as i do not own an s4 so i would not know.

 

I used to have both of them laying around, but I tossed the s4 one because the studs had come out. Anyway, they appeared to be the same.

Edit: They are different part numbers for the manifold as well as the gasket, so they apparently aren't identical.

 

Series four exaust gasket has the hole for the EGR in it. See the pictures in my above post.

 

Sorry Hailers, completely missed your post above. Oddly enough, in the 91 parts manual the gasket and manifold pictured actually has the hole for the EGR in it, just like in the s4 which is what threw me for a loop. Also, the manifold on my 87 didn't have that hole either, so it must have been from an s5.

So as long as you don't need an operational EGR, they are interchangeable.

 

i just bought one wth out the conector. i just cut the wire to the old one and connected it together and heat shrinked the two together. It works great and increased my gas millage by 30 miles i know now very much but hey i get an extra 30 which helps out.,

 

oh i bought it from advanced auto parts

 

Alright, so reviewing this, the S4 and S5 manifold are identical besides the fact that the S4 had the hole for the EGR gases to enter the intermediate housing and go to the EGR. Flow wise they appear to be the same. So if you aren't using an EGR, the manifolds are interchangable, but in the case of performance, it doesn't matter which you have. The only difference will be if you switch to a aftermarket header of some type. Has anyone tried to port the stock exhaust manifold? I remember reading that there's really nothing you can port on it since it's already pretty thin, and porting it even more makes me think that it may start warping.

 

Porting the stock manifold is an exercise in futility. The problem isn't so much the total flow, the the way the air flows. It just dumps everything into the same chamber, and theres no amount of porting that can help that.

 

Yea, that make sense. I was told there's nothing you can do to really port it because of how it flows. Looks like I'll be ordering my stuff here pretty soon then.

 

Ordered my stuff just a bit ago. Looking forward to installing them.