S4 vs. S5

[ITS5GB]

Looking for a little feedback on the S4 vs. S5. I know factory set up shows the S4 making 146hp and the S5 making 160. What is the optimum set up assuming you are using all stock components? My 2nd gen ITS car had an S4 with S5 electronics (I think). Are the "kegs" interchangeable? Can the S4 setup do as well as the S5?
There are a few S4's for sale at reasonable prices. Just wondering what you guys think/know. Thanks

[Andy Bettencourt]

Looking for a little feedback on the S4 vs. S5. I know factory set up shows the S4 making 146hp and the S5 making 160. What is the optimum set up assuming you are using all stock components? My 2nd gen ITS car had an S4 with S5 electronics (I think). Are the "kegs" interchangeable? Can the S4 setup do as well as the S5?
There are a few S4's for sale at reasonable prices. Just wondering what you guys think/know. Thanks

More than likely your car had S5 rotors with the S4 intake, AFM, OMP and electronics. A common swap is the S5 intake into that mix. Most guys do it all at once with the S5 'upper and lower' ends (intake, housings, rotors, etc) into an S4 chassis and install the accessories as noted above.

Nobody should be running the guts out of an S4.

[ITS5GB]

So should I be looking for a car with the 351 coded ECU as a start?

[Fallout]

Looks like the ECU has to stay with the car. Same with the front cover, throttle body, injectors, AFM, water pump.

http://www.rotaryresurrection.com/rotary%20pages/series5swap%20folder/series5swap.html

So even if you use a higher compression S5 engine, you will have to operate it with a ECU that is tuned for the lower compression, at least if this article is right. And the internet is always right, right?

[mbuskuhl]

'86 chassis IIRC is the lightest. S5 rotors and intake superior to S4, those are the two biggies for hp. Lots of other differences between the two, with "better" falling in both buckets.

I ran a S4 shell, S4 ECU w/ clipped limiter, S4 housings, S5 rotors, S5 intake, S4 TB and AFM and the car made power.

Take a look around at rx7club.com and you will find lots of information on the various differences. The best car is half S4, half S5.

[Greg Amy]

...S4 housings, S5 rotors, S5 intake, S4 TB and AFM and the car made power...

Uuuuhhhh...what happened to "shall be substituted as a complete assembly"...?

[Dano77]

How did I know you would ask that Greg. Hmmmmmm

Dan-0

[jrx13]

ECU's are free now so you would not need the S5 ECU and electronic metering pump. You just want the S5 rotors, I have heard back and forth on which intake to run S4 or S5 but never seen back to back dyno results. I agree the best is S4 lighter chassis with S5 power.
Going off memory but I think the S4 control arms have replaceable ball joints and the S5 also has a slightly bigger fuel tank, but the S5 body updates do look a little more modern.

[mbuskuhl]

Uuuuhhhh...what happened to "shall be substituted as a complete assembly"...?

Just read the rules again. Thanks for pointing that out. I ran ITS for a brief period in '07 is all. Since there were no other ITS cars in my area then, I switched to ITE and later PT_. Looks like you need to use the entire long block. There is no advantage to the S4 housings, AFM or TB, but the rules are what they are and call for "complete assembly".

[Fallout]

So help me to understand that better:

The rules dictate a housing and rotors coming from the same Generation.
And it is a big problem to swap a complete S5 engine into a S4 car.

-> Most 2nd Gen ITS cars out there are S4s due to the lighter chassis and have S4 engines w. S4 ECU/TB/AFM with S5 intakes?

[Andy Bettencourt]

So help me to understand that better:

The rules dictate a housing and rotors coming from the same Generation.
And it is a big problem to swap a complete S5 engine into a S4 car.

-> Most 2nd Gen ITS cars out there are S4s due to the lighter chassis and have S4 engines w. S4 ECU/TB/AFM with S5 intakes?

No, it's not a big problem. I may be over-simplifying it but:

S5 motor. Complete with housings, rotors, intake, etc.

If you are running an S4 chassis, you will probably be using the S4 harness. So the easy button is the AFM from the S4 (not the MAF from the S5), and the manual OMP hardware. ECU's are open but using the one from the S4 is cheap.

Bolt on a nice intake, get the ISC header and exhaust and you will have about 170whp.