182bhp turbo 318is!!!

[Demlotcrew]

(all the below are just my own ideas based on general theories, i don't have experiance with working on M42/S14/S5x heads or engines but i thought i'd try to contribute some ideas to this interesting discusion)

Dude we need a little input, this is way out of my knowledge of engine dynamics. I did get a very old book out on long term loan from uni but then could not read it as i had other uni commitments to be getting on with.

Andrew

[tim_s]

hmm yeah vanos, does complicate things somewhat i guess!! but as a counter-argument the single vanos on the s50b30 is a pretty simple affair, wihich only adjusts the cam timing, not the duration/lift, only has two positions, and only adjusts at two engine speeds, so the cam timing advances at mid rpms (just off idle) then retards to the orig position at higher rpms. so at high rpms the cam is at the same position as at idle.
with the s50b30 the vanos simply adds some cam timing which gives good torque at mid rpms, and removes the compromise that you have with the m42 (hence why people piss around with the cam gears on the m42).

but as far as port tuning (in terms of the inlet ports, port length, throttle body size, trumpet length) is concerned, there is still a compromise to be made, whether it has single vanos or not.What i'm driving at (in a roundabout kinda way) is I can't see how the port design would be greatly affected due to the engine having single vanos and i dunno that it would otherwise have bigger valves/ports to make the same power. it would probably just run less cam advance at low rpms. to make its big power figures higher up the rev range, regardless of the cam timing (which with single vanos at high rpm is at the same timing as at idle), the port tuning is just as important on both engines, and the VANOS not really a factor. you'd have thought, if anything, VANOS would have meant the opposite - that is that the inlet ports could be wider and the valves bigger on the s50b30 and esp s50b32 due to cam timing being able to compensate for port tuning towards higher rpms.

i know its a different matter with double VANOS on s50b32 and s54 though which is a much cooler system! but the inl ports/valve size/tb size etc all remain pertty much unchanged from the s50b30, which suggest that the VANOS isn't really a factor in the inl port design.

i guess if anything the use of vanos + small ports points towards wider power/torque spread. think the most compelling argument still is the most simple - the s14 has bigger bore so bigger ports. dunno what that means about the throttle bodies though, that is weird!

[Demlotcrew]

ON the Evo II cars they were fitted with a Exhaust cam gear, which retarded the exhaust cam by 6deg, all this did was move the power band lower in the rev range to make it more of a street car (the peak lbft was reached sooner)(the gear helped the exhaust scavenging thus changing the power curve) I wonder if the single vanos S50 does the same (except its on the Inlet side)

Andrew