Modifying intake manifold

[Mark Halligan]

quote:
@Mark - Oi geezer that's quite a penknife you have there

Paul, my trusty Dremel with cut off wheels.
I do CHEAP dental work too :eek2: if any one is interested. Best bring your own anasthetic though, or its the 5 pound club hammer .

Mark.

[Pisobiker]

Originally posted by Mark Halligan
Paul,

You could well be right, who knows especially when it comes to forced induction.
I did do a bit of reading up today between butchering expensive bits of metal, and one book I have, advised smoothing out any high spots (welding dags, etc) and then in another paragraph said that inbuilt turbulators can help with equal cylinder distribution :wacked: .
On another note, does anyone here know if the SQ KW inlet manifold can be adapted to fit our engines? I know it has the water manifold built into it, but I think I read somewhere that it could be made to fit?


Cheers, Mark.

As far as I know the smoother the surface the better the flow.
There have been some talking lately among tuners, about the need of leaving some "roughness" on the intake ducts. This because it suddenly came out that aerodynamical "limit layer" ( literallly translated from Italian ) could be reduced if doing so.
Most efficient moovement of fluid in a duct is "laminar", which means fluid can be considered as many fluid layers mooving at increasing speeds while going from outer to center section of duct. "Limit layer" is the layer very next to duct's wall which is supposed not to be mooving because to friction with the wall itself. Then the smaller the "limit layer" the better the flow (average speed of fluid in duct's section). But the smoother the wall and the less the turbulances, the thinner the "limit layer" will be. If the "rough" issue would have been correct, then, at least F1 engines wouldn't have had "mirror finished" intake ducts, like they have .
Turbulances in the intake ducts and some "roughness" are aerodynamical ways to allow better low rpm torque, better mixing of charge, thus reducing fuel consumption and exhaust pollution (high swirl intake engines where designed to allow stoichiometric charge to reach only combustion chamber part wery next to spark plug, than having a leaner mixture in the other volume) but they will definitly affect high rpm flow (therefore top performances).

About using "steps" and other aerodynamical "brakes" to allow even distribution of flow among cylinders, I believe this is not the "high performance" way to manage the problem. This in fact is supposed to do the job by "lowering" flow reaching the best fed cylinders, instead of upgrading manifold and duct's design for "increasing" efficiency of the worst fed ones.


A way of testing intake ducts flow (inside runners and head ports) could be as follows (I know this would not be a "cheap" way of testing intake duct flow, but probably the easyest one):

Drilling 5 holes on the IM runners (one each) at the same point, then thread them putting in 5 fittings for small pressure hoses. Then five equal lenght hoses to 5 boost gauges with "top boost" memory (maybe all 5 of them bolted in a straight line on a metal bar). Running this device at WOT at different rpm ranges (lets say in 1000 rpm increments) will give flow rate for each cylinder at given rpm. Maight not be 100% precise, but could give some good information to find out if optimizing would be worth or not.


Marco