i am rebuilding my s4 tll motor and i am wondering if i should stick with my s4 rotors or go with the s5 i am looking to get 400 hp out of it any suggestions

 

 

i know i'll probably catch hell for saying this, but personally, i wouldn't lose sleep over getting the S5 (9.0:1) rotors unless something was wrong with one of yours, forcing you to replace them anyway. you'll have to put the same effort into tuning the engine for your 400HP goal regardless of rotor weight or compression. neither is a substitute for tuning. put the extra $100 to 200 that you would have spent on a pair of rotors (and counterweights or balancing) into your fuel, engine management or turbo funds.

 

S4 has lower 8.5:1 compression ratio, so it will have less chance of detonation at higher boost levels needed for 400RWHP than 9:1 S5 rotors. Also, they have a thicker face and so do not dent from detonation.

Downside is they are heavier, but you don't have to rev it high to make the power with a turbo.

DO use S5 rear side housing (easiest w/ S5 front housing to match as ports are diffrerent) as it has an extra cast in reinforcement at the rear dowel pin area where S4 housings commonly crack at this power level.

 

Hey isnt there a site that shows the difference between all rotors with their comp. ratio and weight and all that? Ive seen it once but if someone could link it that would be cool.

 

the chart is on the Mazdatrix site

 

So you are saying that S5 rear housing is compatible w/ S4 motor?

 

yes. Gen II and Gen III 13B housings work together, but it helps if you match the secondaries (front and rear).