Ok, so I searched and have read the FAQ's at rotary ressurection. I have not found an answer specific to my question so if you have any knowladge of this, I would appericate it.

Ok, here we go....I had an apex seal take off in a major way in my ITS car and need to do a rebuild on her. I have a set of S4 housings and am wondering what I need to do to be able to use these in an S5. How do I ( or do I even need to) accomodate knock sensors, and what is plug timing(is that the location or the actual firing of the plug). Any other issues you fine folks may know would be appericated. thanks guys!!!

 

these are rotor housings too, not irons, just to be more specific Thanks!!

 

your good with the housings I don't believe there isn't a difference between S4 to S5 rotor housings

 

im no expert but i dont think there is a difference , i think your good to go .

 

I have an engine with one S4 and one S5 housings. No problem, runs great.

 

I believe the spark time might be slightly revised, but nothing very noticable, especially if both housings are from the same series.

 

what do you mean by time, is that the location of the hole? thanks sideways

 

The only differences:
S4 irons do not have a mount above the spark plugs for the knock sensor. S4's mount the knock sensor in the intermediate iron. You could easily tap the intermediate iron to accomdate for this, the boss is there on the S5 iron.
S5's supposedly had a better chrome coating that was suppsoed to last longer.
S5's had a revised spark plug location. This does NOT affect engine timing. It merely affects where the flame propagates from. Timing refers to at what rotational degree of the engine (or at what position the rotor is at) when the spark plug fires. Moving the spark plug up or down doesn't change the rotor's positions when the spark plug fires. The only difference that is changed is where the flame front starts in relation to the rotor.

So use 2 S4 housings and tap the intermediate iron for the knock sensor and you're fine.

 

It DOES effect ignition timing
To set the timing correctly you will need a S4 main pulley. The timing is very different between S4 and S5. You certainly should not mix S4 and S5 rotor housings in the same engine.
There is no need to tap the housing for the knoock sensor, just move it to the intermediate iron at the base of the oil neck, where it is located on the S4.

 

I currently have the racing beat pully set on the S4 ITS motor in the car now...can i switch that over to the s5 to adj timing....i currently run a conservative 20degrees....is that still ok???

 

bump

 

Wrong.
The ignition timing is not affected by spark plug location.

If you fire the trailing plugs when the rotor is at 10 degrees before TDC, what is the tailing ignition timing? 10*BTDC.
If you fire the leading plugs when the rotor is at 10 degrees before TDC, what is the leading ignition timing? 10*BTDC.

In both cases the rotor is at the same position: 10* BTDC, yet the spark plugs are in two different locations. Moving the spark plug around in the combustion chamber does NOT change ignition timing. Ignition timing is a reference to at what position the rotor is at when the spark is fired.

If you put a S4 pulley onto an S5, and do nothing else, does the timing change? Of course not. The pulley markings just no longer reflect the rotor position.

If anyone is actually serious about ensuring their engine is timed correctly, they verify their eccentric pulley against a degree wheel. I always do. Regardless, just because you have your pulley mismarked does not change igniton timing, it merely changes what you think your engine timing is.

Again: moving the spark plug does NOT change ignition timing. The revised spark plug location on S5's has nothing to do with the ignition timing. The ONLY change by moving the spark plugs is where the combustion flame begins from.

No.
Never ever change stock pulleys.
The pulleys are matched to the hubs.
Check the part numbers:
N326-11-400B for the S4's and N350-11-400B for the S5's.
These parts are for the hub and pulley together. You must keep them as a matched set.
The timing key is in the same location on both S4 and S5 front covers. The eccentric shaft key-way is the same between s4 and S5's. All you need to do is ensure your pulley is the same one that came from the factory with your hub.
You always keep the same generation pulley with the same generation hub. Its best never to separate them.
Then again, its best to verify the pulley markings with a degree wheel.

 

The eccentric shaft is virtually the same between S4 and S5. So, assuming the the RB pulley is correctly marked in the first place, their will be no change in ignition timing by using that pulley with the S5 rotor hosuings.

I don't know why people can't understand this.
If your motor fires at 26* BTDC, this refers to the eccentric shaft position. Moving the spark plugs will have an affect on combustion, but it will not affect the ignition timing.

 

the difference between the flame front timing will affect the running of the engine, it will damage parts since the 2 rotors will not be power balanced properly between the 2 rotors.

if you want to test this theory, feel free, i've already been through what happens when you mix 2 different series rotor housings. might work fine in n/a applications but not in turboed ones.

 

Ah, good. Maybe Scathcat can clear something up for me.

Both S5 and S4 eccentric shaft are the same. Both have the keyway ninty degrees from TDC. So I'm taking that as a given.

So now I ask myself *why worry about using a pulley (not hub, pulley) from a S4 on a S5??? Every thing seems the same. The only reason for them being different would be if the holes on the HUB that attach the pulley were different on the S5 vs S4. So? Is that the case?????

And I agree in spades with what Scathcat said about the timing vs the sparkplug hole location etc.

And I'm a newbee. Where does one get a degree wheel? Piece of paper with degrees on it that you mate on the pulley??????

 

I can't verify with 100% certainty the difference between S4 and S5 hubs/pulleys.
The problem, I think, is that Mazda didn't switch over the pulley/hub difference immediately with the S5's, or they started the difference early on the S4's. Just when I think I've found a pattern, another car comes along to throw it off. Then throw in remans and rebuilds.... its not infrequent that they mismatch hub/pulley combos.

I can tell you this: I have seen stock pulleys that do not match up to the eccentric shaft timing. The only way this is possible is for there to be a difference in hubs.

I have only seen two variations on the timing marks... either the mark lines up one way, or its off to the same certain degree.

Since there are different part numbers, it fairly safe to assume: there are only two versions of pulleys, and there are only two versions of hubs. I can tell you that there are definitely two versions of each.


A degree wheel is simply a round wheel that you attach to the eccentric shaft, with a rigid pointer. You can buy a degree wheel, or make your own. I bought mine:

Its a mr gasket 11" wheel.

I attached it to a stock flywheel nut. I like to use the flywheel nut since it allows you to stack the front cover and mark/verify the front pulley, and you can read it on the engine stand easily without having to bend down. You can just as easily mount it to a front hub.
Mounting is up to you.

When you mount to the front hub, you would need to make sure the eccentric shaft is at TDC, then mount the hub, then mount the pointer, then mount the degree wheel to the hub while aligning it to match the TDC on the pointer. As long as you kept the same pointer, and the same hub, you could check different engines by simply slipping the hub on.

With my mounting, which I prefer, you must calibrate the degree wheel every time you install it. The flyhweel nut which it is mounted to has a set screw which I thighten to bind it to the eccentric shaft. The pointer is simple 1" x 1/8" steel, ground to a point and mounted across the water pump bolts.

To calibrate, I install a front iron onto an engine stand, then mount the pointer. Then, I install the eccentric shaft (with a front stationary gear installed), and then thread on the degree wheel/flywheel nut, and turn the eccentric shaft to approximately TDC and then lock down the degree wheel set screw.
Next, I mount a piece of aluminum angle bar across the spark-plug side of the engine, bolting it to the front iron. I make sure that this bar is parallel to the engine porting side. Then, I turn the eccentric shaft until it hits this bar in one direction and read the degree wheel pointer. Then, I turn the eccentric shaft the other direction until it hits the bar, and read the degree wheel. The reading directly between these two points is Exactly top dead center, so I unlock the set screw, spin the degree wheel to what I have found out, and the use the set screw again.

For example: If the eccentric shaft hits at 20 degrees on one side, and 24 degrees on the other, I know to line the pointer up to 22 degrees. You are trying to achieve the same reading on both sides.

I prefer my method of calibration every time since it allows me to verify against different stock hubs and pulleys, and it makes up for differences in the pointer bending/moving around between installs.

You can also use a carefully placed dial gauge to find TDC.

 

Wow. thank you all for your time, I can see that is a time consuming and extremely thorough, and helpful answer, thank you all, Scathcart especially!!!

 

To reiterate the answer your original question:
Yes, you can use S4 housings with an S5 engine. Just make sure you use a matched set: 2 S4 housings, or 2 S5 housings.
Use the pulley you've got now. It should be matched to the eccentric shaft and should reference timing exactly.
The knock sensor can be mounted in the intermediate iron, below the oil filler neck, on the front side of the iron. I can't remember if the boss is drilled on the S5 irons or not. If it isn't, you'll need to tap it. If it is tapped, even better.

Good luck next season.


I'll be setting up the degree wheel tomorrow as I rough out a port design/check the pulley. I'll snap some pictures of the assembly, and the different hubs/pulleys and the problems it can create.