Difference between S4 engine and S5
 

I just found an S4 engine for $675.

What is the difference between it and the S5 engine that came in my 89TII?

Will i experience any problems putting in the S4 instead of the S5. Will I be able to get as much gain from modifications when compared to the S5?

S5 its like 20 more HP, its got an electric OMP, higher compression rotors

It takes a diff wiring harness and ecu ect ect ect, you will have less power than the S5

Lots of differences. Don't do it. :)

If you're talking about ONLY the shortblock, it'll work, but you won't like it - you'll be down on torque (probably similar hp). Most everything else changed from 88 to 89.

Brandon

well crap...

Indeed, injectors are different, front covers are different (to work with the mechanical MOP) The throttle body is also different, as the S5 has a dual TPS setup, and the series4 has a single. Not to mention that the water pumps are slightly different (though it can be used)

use the sht block it canhande more power,ask any rotory builder the 91 engine is a piece of shit.

why is it a piece of shit?????
 

explain rudeboy!

I'm plannin on goin from a 88 N/A to a 91 TII..... its my first time takin a engine out.. about how long do u guys think it will take me......... i'm hoppin for atlest 5 days... non-stop...... i need the car

i know im in the wrong forum but........i was just curious..... what is the average 1/4 mile run for a 88 N/A?

I THINK ITS LOW 16'S FOR A STOCK N/A

it took me about 3 hours to pull my first 13B.
it took another 3-4 to take it apart.

What is so wrong with the series 5 engines? Other than the electronic oil pumps, I can't think of much a reason. This especially blows my mind when you yourself used a 91 block in a series 4.

There are quite a few differences in the S4 and S5 engines both internally and externally. The S5 is definatly the beter of the two in my opinion.

The external differances are the intake/exhaust manifolds, the tb cap, the location of the knock sensor, the electronic OMP, front pully, flywheel and some varios other sensors and things.

THe short block is sinificantly differant also when you consider there are so few parts to it. The rotors are the major difference. First the increased in compression (8.7:1 to 9.0:1). Also the S5 motor has milled/machined compression faces (like the FD) as opposed to the cast faces on the S4. This produces a much more uniform compression face. Also the dowell pin area's of the S5 housings are stronger so they will support more HP overall, though cracking in this area is only a concern over ~400whp or so.

The biggest thing for me is the better rotors. The more cleaner compression face would seem to me to prevent detonation much better than one with the imperfections.

Will my S4 block work with S5 external parts?

Yes, it would, but not well, the fuel maps were different from s4 to s5 and due to the compression change, I heard it runs like crap if at all. But you can always try!

The stationary gears on the s5 were stronger.

I have a friend that races a s5 professionally,
and for his engine he uses N/A s4 housings with s5 internals and e-shaft

I was pretty sure the stationary gears were the only difference in the S5 rotors and the FD rotors. I wonder if they are the same rotors, anyone work in a Mazda parts department and want to look up some part #'s?

S4 Housings with the rest of an S5 engine???
That's odd... I thought they were the same, I wonder if they aren't what the diff is.
About the only advantage the S4 engine has is the slightly lower compression rotors have more resistance to detonation when running 15psi+ boost. That's a pretty narrow market that goes there...
So for the rest of us who aren't running pro drag cars, the S5 engine is better.

I think this is the first post I've seen that deals with an S5 swap to S4!!

I wonder when were going to see a TII to N/A swap!

i used a 91 in a 91 but with s4 electronics,thats how alot of rotary shops in suth florida do it .ruff racing runs low 11's with s4 equipment in an 91,stock comp ,upgraded turbo,and injectors.And yes it's because of the lower compression rotors but als mzda's build quality changed over the years,the s5 motor was cheaply built.

Higher compression doesn’t require more or less fuel, so the fuel maps won’t be that different. Ignition timing is more important when talking compression changes. Besides, it’s only a small increase in compression (8.5:1 to 9.0:1 for Turbo), so I’m sure it would run fine.

I have heard the same thing TurboII Rudeboy! In fact 3 very knowledgable mechanics that work exclusivly with the rotary have told me the same thing; that, for some reasons that are over MY head, the s5 engines "skimped" in many areas. I guess many of the parts they used were just NOT as high quaility as the s4's! Cheaper metals were used in some areas. That is what I was TOLD and by THREE different people, so it is probably true, I don't know for SURE about that though!!