alexluker

Scott

You aksed for pictures of a 6-3-1 manifold.

See this link

http://www.chriswitor.co.uk/Chris_Witor_St...el_Products.pdf

Chris was the ONLY person I would deal with for my Triumph. However since I wrote it off and got a sensible car I'm hoping he'll get interested in the IS.

I thnik that's more than enough manifold spiel from me.

Alex

Why didn't you go for a 6-3-1 format? Possibly an opportunity missed?

It's a 6-2-1: could do better

See my earlier comments.

However it's shiny and it's your money...

Which format do these manifolds come in for the six cylinder engine? 6-3-1 or 6-2-1?

I spent many happy years tinkering with Triumph 2.5PI's and you need a 6-3-1 on ANY straight six. The trouble is that the headers need to be paired up 1 and 6, 2 and 5, 3 and 4. Clearly to maintain the same pressure drop becomes a tricky exercise in pipework fabrication. Most so-called specialists opt out and connect 1,2,3 and 4,5,6 together as a 6-2-1.

The reason for pairing up a 6-3-1 with pairs at opposite ends of the block is that it's good to connect cylinders 360degrees apart (in terms of crankshaft rotation) so that you get a scavenging effect

I've never found out the firing order on an IS200 but it’s either 153624 (like a Triumph) or 142635 (like a BMW??). This is because a six has a firing stroke every 120 degrees of crankshaft rotation so it either turns one way or the other. The pistons come up and down in pairs but each pair (1 and 6, 2 and 5, 3 and 4) is phased 120degres apart. Obviously the pair in question don't fire together but alternate in a four stroke style. The slug of exhaust gas from one cylinder is on its way down the header by the time the slug from its mate starts its journey. The first slug creates a partial vacuum in it wake which helps to draw the second slug along - hence scavenging or 'extractor'.

Of course this is really ancient technology; maybe I'm a 30 something old f@rt and things have moved on. I guess chipping it and bolting on a blower makes this all a bit academic.

Enough oily fingered rambling – after all I'm too scared to take my IS apart!!

Alex