What are the diffs between the two.

Short block only, as manifolds, ignition systems and, etc are interchangable.

S3:
3mm Apex seal
Waterjacket o-ring location is on aluminium housings

S4:
2mm Apex seal
Waterjacket o-ring location is on iron housings

What else?

Are the 3mm apex's really better than the 2mm? Better handling of PSI for boosted applications, but more damage to the rotor housings.

Does the waterjacket o-ring location really matter? Does anyone even lap irons anymore? You lose the nitride coating when you do that.

 

the manifolds are interchangable on engines, but the upper and lower bolt patterns are slightly different. the S3 used a distributor with its primitive EFI, the S4 used the crank angle sensor with it's improved EFI. much better in my opinion ...

2 mm vs. 3 mm - do you really want to start that argument here? i think it's a mtter of how far you want to go and how dedicated (pronounced "****") you are about getting there. i'll leave it there.

otherwise, as far as i know, the only major difference with the engine itself is what you mentioned - the water seal locations.

 

Also the S4 NA engines have diffusers in the exhaust ports. Quiets it down a bit, but will probably hurt flow. You can grind them out (lot of work) or replace with T2 exhaust sleeves.

The S4 also has lighter rotors and a lighter flywheel. The 3mm vs. 2mm seals doesn't really matter. The 2mm can hold plenty of boost . The 3mm isn't really an advantage.

The other main difference is the location of the coolant seals as already mentioned. I am not sure if there is an advantage to one way or the other. It does seem that the 2nd/3rd gens have more problems with coolant seals, but that may just be because there are more of them around and have to deal with higher engine bay temps. I do believe the RX-8 went back to having the seals in the rotor housings, so maybe that is the better design afterall.

The S4 engine would probably be easier to find and you probably could get one cheaper becuase there are so many more of them compared to the S3 13Bs.

 

just to add to this ... this is a thread in the Gen II Archives that i've recently become familiar with on this subject.

 

Well, add to the oppourtunities of engines I can get, an S5 N/A... Just pulled in a wrecker... Front end damage crushed the coils and battery, but engine looks good. Once I get a little SawzAll action going on, I'll check out the engine.

S5's were similar to S4's except they have electric OMP (Which I do not like.) Lighter rotors/higher compression... What else?

S3 engine is free, High mileage core (Close to 200K, still running.). Inexchange for helping someone install a MegaSquirt.

S4 engine is a recent rebuild of unknown quality. As such, it's being sold at a core price, if I chose to buy it.

Ditto with above mentioned S5...

All three are long blocks with the exception of the S3 13B which is missing oil pan and front cover...

I also have my stock 12A that I have yet to pull.

So.. I have a HUGE pile of parts available, and I'm trying to build something.

My goals:

Street ported, possible forced induction at a later date.
EFI, MegaSquirt. Preferably 2 stage injection, FC primary, GSL-SE secondaries.
FC Ignition controled by MS (Trailing works now. )

I'm still trying to figure out which set of housings to use. The N/A diffusers will be removed.

 

I think it was mentioned that the S4 engines have less chrome flaking than S3 rotor housings.

Also, having opened up an S3 engine and a bunch of S4's, the exhaust ports on the S3 13B's are much smaller.

 

the primary runners are smaller on the se 13b's. IMO the se block is better just for the fact it has the grooves on the housings. Why, because that way you can lap the plates without sacrificing groove space, also stronger for boost. Just port the **** outta the se block. If you are really worried about chrome flaking get them cermet coated

JHBperformance.com does the cermet

 

from waht you've presented as having access to and what you described as your goal, i would say get the S3 and build your engine using the side housings from your 12A.

if that doesn't appeal to you, then my next vote would streetport the S5 ...

 

If you are going to streetport and all that stuff do the s5, high compression is better in all applications. If you thought about going forced induction it would also be better, spool quicker, more horsepower with lower boost. You would just have to step up the intake cooling a little bit (as I'm sure you know), maybe throw a singlestage water/alcohol injection piece of mind.

 

If you plan on boosting make sure you go low compression. I used s5 turbo rotors, nice compromise between the s4 turbo and high compression. Handles boost well and still has good torque without boost.

 

Why do the FC and FD guys have thier rotors milled out for 3mm Apex'es if the 2mm is just fine?

 

it all comes down to different schools of thought. you'll hear some say it's for a larger error margin and you'll hear some say that it's required for big power.

i'm of the opinion that you'll make the same power, just as reliably as you've tuned the thing, on either apex seal. i, personally, like the newer 2 mm seals - though i have nothing against the older 3 mm ones.

 

Well, I tend to look at things from a Pro and Con standpoint...

Logic would dictate that given the same material, the 3mm would be stronger, but would cause more housing wear...

But there's probably more to it than that, as I don't know if it is the same material and such.

 

Also, what does the R5 cast housing come from, as I'm told it's the strongest... Looking for a set.

 

also the s3, and s4s5 6 ports have different timing. I know one had 10* moreof port timing, but cant remember if it is teh s3 or s4s5.

 

The R5 comes from the 70s 13b i believe, strongest not sure about that.

 

The main problem with haveing that water seal grove on the cast iron pieces is the grooves themselves become prone to cracking.

Ive never seen the grooves on a rotor housing crack

 

So here's what I'm thinking:

Rotor housings, Irons, and E-Shaft: S3
Rotors, If I can find some good ones: S5 N/A (After prying off the hood, I found out the N/A Engine that was swapped into the wrecked TII is an S4. Drivetrain is still TII though )
Oil pump, OMP: S4
Water pump and housing: S4
Manifolds: S5

Keep the 2mm Apex seals. Street ported. Remove exhaust sleeves in rotor housings. FD Corner seal springs, and if I can find R5 cast iron housings, use em.

Frankenstein engine. The best parts I can find offa anything else.

I might go Forced induction later on, low boost.

I remember there was a chart of Years, rotor weights, and compression ratios. I thought it was at Mazdatrix's site, but I can't find it. Anyone know about it?

 

not jacking the thread, but what are your guys' opinions on how high a bost has to be to make it a high bost, and how low for a low bost?

 

the s3 rotor housings have different spark plug location vs. the s4 rotor housings. Make sure you match the ignition system to the rotor housings. The s4's were the only odd *****, s3 and earlier along with the s5 and s6 all have the same spark plug locations.

 

But the S4 and S5 coils and CAS are the same right?

I was planning on using whatever the platinum plug is for the FC. My standalone controls ignition, leading and trailing based off the FC CAS.

 

the ECU's are different

 

Not gonna touch Stock FC electronics. I have a standalone that'll work.

 

Bump