Extractors can actually vary quite greatly in design and configuration - ie. they can have different diameter pipes, the primaries and secondaries can be different lengths and their configuration can vary - as in you can get 2 sets of 3 pipes that go into two larger ones or you can get 3 sets of 2 pipes that go into 3 larger ones (or straight into one large one) etc. etc.
As I said, some designs work but others don't - I have felt the immediate difference of changing one set of extractors which never did feel like they made any difference with another set which imediately made a NOTICEABLE difference! Rule of thumb I gather is that to actually feel a difference it needs to be something like 4 or 5 Kw?
Nope - I'm an aircraft engineer (ie, somewhat analytical and critical) and have also done heaps of work on this car - some things have yielded noticeable result, others haven't - I trust my ability to "feel" whether there are actual results or otherwise.
As a matter of interest I never felt any improvement in power with fitting a K&N panel filter either - and when I replaced that with a pod inside the airbox I think there MIGHT have been a barely perceptible improvement - but not enough that I'd actually state that "it made an improvement".
I've also gotten a definite improvement in fuel economy with these new extractors - that's something both myself and my wife have seen, not just "perceived".
EB4ME - The extractors I've got now are Pacemakers with 402 stamped on the flange - don't know if that's any help? They have 2 sets of 3 primaries which go into 2 secondaries which then meet pretty much right at the flange where the rest of the system bolts on. I don't know what the other set were - they had 3 sets of 2 primaries going into 3 short secondaries that went into one at the joiner flange (that flange was up much closer to the side of the engine too - ie. as opposed to the Pacemakers which have the flange pretty much under the driver's feet) - they actually looked quite a bit better and more "business like" than these Pacemaker ones do - but right from the day I got them I felt no improvement whatsoever - but as I said, these Pacemakers did make an immediate and NOTICEABLE difference.
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