Dai... I've been having some thoughts (or more to the point, talking to a few people... don't want to limit just to my thoughts ) I know equal length tracts on an exhaust is a Good Thing(tm) but, would the increased length from 3/4th pot to turbo introduce lag?
Also, if I had one of those early 440 manifolds in the garage... would I need to use the dual butterfly tb that it uses, or can I just bolt the 18ft throttle body with big butterfly in place? I can see that on part open throttle, if the butterfly is rotated to the wrong alignment, then one side would get more air than the other, but if you mounted it so that when it starts to open all intake are covered (e.g. split in manifold |, and butterfly pivot --)
Equal length is theoretically better, but it's not going to stop you making good power. I'd suggest it's more important to get a nice diameter primary pipe for each pot, running into a decent collector, rather than worrying about equal length. If you can do equal length, it won't hurt, but I'd not get too wound up over it. 'Log' manifolds like the standard 400 series turbo one (if I'm remembering what it looks like correctly) aren't a nice design in the grand scheme of things, but I'd not worry too much about that - there are other things which will undoubedly be more important when it comes to getting a setup which works nicely.
Moving on...'Inbalances' like that are inherant to most inlet manifold designs. I'd not worry about it too much. For example, on a redblock 8v EFI manifold (as found in a GLT), the runners for pots 2 and 3 flow marginally than those for 1 and 4. IIRC, Volvo allegedly ran a marginally richer AFR on #3 for the Group A 242s to compensate.
Sorry dude, didn't explain myself proper on the inlet manifold side. If the throttle body is mounted with the pivot axle of the butterfly in plane with the split in the manifold, when it is only slightly open (i.e. when cruising) the air will be allowed into the first cylnider only, not equal flow to all cylinders.
I'm thinking if I mount the single butterfly throttlebody at 90degrees, e.g. the butterfly axle is perpendicular to the manifold split, then the air *should* equal flow to all cylinders, all the time.
THe early 440 injection manifold is a progresive twin choke throttle body (for those who do not know what progressive it means that the primary butterfly opens to about 3/4 open before the second butterfly starts to open so the last quater of pedal movent will be opening both chokes at the same time with the secondary chock opening very quickly) and is therefore coupled to a common collector. As a result of that it does not matter how you intraduce the air. The idea of the progressive twin choke is to give smother low down response and improved fuel consumption.
If you want to fit the TB of the turbo manifold you will have to make an adaptor plate.
James as to the equal length on the exhaust its not the end of the world tbh. Most likely what will happen is 1 & 4 are going to be a little longer than 2 & 3.
The guy who will be building the manifolds realy knows his stuff and the final desicion will be in his hands.
Sorry - I went off on a bit of a tangent there without including what was supposed to be my first sentance, and actually answering the question! The split in the pipes doesn't happen immediately Chris...hence why you can get away with that arrangement without creating an imbalance.
My memory of the throttle arrangement was that the throttle area was pretty small - as Dai says, most likely designed to aid fuel economy, etc - I'd look at upgrading to a single larger throttle anyway.
classicswede wrote:James as to the equal length on the exhaust its not the end of the world
Exactly what I meant...it's nice, but not critical.
) I know equal length tracts on an exhaust is a Good Thing(tm) but, would the increased length from 3/4th pot to turbo introduce lag?
