I'm looking into the option of rebuilding with higher compression rotors and I remember seeing somewhere the compression ratio's for all the rotors but I can't seem to find it in search (sooo many results). Can anybody show me a link/list them off?

Also, anybody know the "danger" level for boost on N/A rotors (SX?)?

Thanks.

 

S5 N/A rotors have a high compression.

 

I know, but I'm looking for numbers.

 

The FAQ...

But I can tell you here, 9.7:1 on S5

 

S4 na: 9.4:1
s5 na: 9.7:1
s4 tii: 8.5:1
s5 tii: 9.0:1
FD3S: 9.0:1

I don't know first gens though.

 

74-78 13b = 9.2 : 1
74- 12a= 9.4 : 1
84-85 13b GSL-SE RESI engine = 9.4 : 1


personally,, having done this more than just a couple of times
the 9.7 will have practical limits in boost ,, with boosts over 10 psi needing quite significant retard ( fuel= aussie 98 RON, equiv to your 92 MON )

9.7 rotors are the lightest,, but also the thinnest and weakest in combustion face
- unless careful will be prone to detonation ,, and denting of rotor flanks


9.4 rotors however ( s4 NA ) are nearly as light ,, but without the compromise in rotor face strength,, and without the drastic retard above 10 psi

-- currently am daily driving a boosted s5 NA block using NA s4 ( 9.4 ) rotors and balance weights
( albiet on propane )
( at 12 psi,, with no hint of det )

and i think out of all the combos of rotors i have used with similar plate/port
this is the best evolution/ combination without compromises

 

Alright, thanks for the help guys, much appreciated.