Originally Posted by
mgtkr1
as gus said, in a nut shell, longer inlet trumpets/tracts promotote midrange power where a shorter increase peak hp. not sure how this fares in the forced induction world. would speculate its much the same. but i always thought a turbocharged engine can still produce rlatively huge hp/torque on the shittiest of flowing engines compared to n/a equivelant. higher boost rs turbo vs gas flowed xr3i for instance. anyway sorry for the drift, how much are these inlets rob? what is the std inlets max ability in terms hp. i know the head on the rst can manage 250hp before its restrictive.
They aren't outrageous, I started looking at them because the burton catalog lists them for £600, however this is without a machined back plate (no port holes, trumpets etc) so maybe even cheaper if you go jenvey direct...
The stuff you mention regarding port length is true, I believe it may have a larger effect on a n/a engine... it would be good to get input from some one who specialises in this kind of thing, but they tend to keep their hard earned knowledge to them selves (fair enough i guess).
I don't totally agree with the rst head being restrictive at 250 bhp... its restrictive at lower HP figures too. Its just that it becomes a problem around that figure, ie having to use more and more boost for a smaller HP gain.
IMO, a decent head and inlet manifold would still be advantageous on lower bhp engines, not just because they are more efficient but because they can be tailored to your application as Perry says...
My general aim is for a high 200's (260-280 bhp) car that drives like a 200 bhp escort does with a stage 2 t3.... just faster obviously. So really responsive, nice wide power band etc... compared to most 300 bhp rs turbos which are very peaky and not particularly rewarding to drive on the road, bar the occasional run up a dual carriage way.