it's a european thing

 

the EU S4 FC's are weird. they use a thermal reactor emissions system, like a pre 1981, US model. since the reactor is so big, they don't have room for the 6PI stuff, and need butterflies instead. the engine is also different, its almost a GSL-SE engine with coolant seals in the wrong place (in the irons, FC), and S4 rotors. since the 6PI is a butterfly those ports are like normal ports, and not like its been drilled like the US engines. they have a completely different control system, it seems to be an overgrown GSL-SE system, it uses a distributor, and a 12V AFM, but has 4 injectors like every other FC.

the S5 and FD engines are the same as the US versions. the cars are too, although they have different option packages.

 

Freaky!

A 12v AFM seems inefficient if that 12v reference is coming from the battery/alternator. So they used a junky distributor, a junky thermal reactor (better than 2 cats I suppose) an unreliable 12v afm with a more efficient 6 port system and fuel injection...makes sense.

I wonder what the power difference is.

 

actually the distributor/thermal reactor is pretty bulletproof, the reactor might literally be so. the reactor is basically just a normal exhaust manifold thats bigger. it works by using the air pump air and heat (hence the name) to basically get the unburned HC's to burn off. since its basically passive, it doesn't fail like a cat does.

the distributor is basically the same as the 1st gen, and those are dead reliable.

the AFM just gets a 12v reference from the ecu instead of 5v, its just as reliable, just a different sensor range than normal.

no power difference, they are all 146hp

 

12v would have better resolution than 5v, but i have a feeling it is not an isolated 12v and that it fluctuates, which is not so good, where the 5v is filtered and stable.