What is the difference between the two S4 engines? You would think someone would have asked it and it would be a sticky by now. Maybe someone could fill in the blanks. There is alot of info on this board about this, but none of it is consolidated. I could search for hours by taking the above title and plugging it into the search function... 500 results... Im sure that was capped off to.

what are the various variations of the 13b Available and why are they different?
Im about to drive across town and spend an hour on the road just to see a N/A 13B s4 and see why its different than my 13B S4 turbo II with S5 housings...

Ray

 

N/A USDM 13B S4
N/A JDM 13B S4

N/A USDM 13B S5
N/A JDM 13B S5

Turbo USDM 13B S4
Turbo JDM 13B S4

Turbo USDM 13B S5
Turbo JDM 13B S5

There aren't anymore variations are there? Or should I put on my flame suit?

 

unmolested non-turbo engines have 6 intake ports whereas unmolested turbo engines have 4. also, provisons for turbo oil supply on the front housing and front cover. that's it. that's all.

there are other small variations from series to series (port timing, rotors, EGR passages, etc.) but the number of ports are likely to be the only obvious difference in a visual inspection.

 

Besides port configuration and timing, compression ratios are the next big difference:

S4 NA are 9.4:1
S4 T2 are 8.5:1
S5 NA are 9.7:1
S5 T2 are 9.0:1
S6 FD and beyond are 9.0:1
RENESIS is 10.0:1

I don't know the compression ratios for the older 13bs off hand.

FC NA versions have metal diffusers inside the exhaust port sleeves to cut down on noise. Also the T2 uses a larger oil pump than the NA motors.

 

yeah, forgot about the diffusers in a spot-check. i didn't get into the specifics of the rotors because other than being able to differentiate between pre-S5 and S5+, there's no visual cue - definitely not between N/A and Turbo of the same series (at least not without having them side by side - turbo is a little deeper).

anyway ... 9.2 for the old-school 13Bs ('74-'78) and 9.4 for the 6PI in the GSL-SE.