Intake manifold comparison

[Roman]

Not an overly scientific analasys admittedly, just casual observation that I've noted down for sake of comparison.

Okay well here's how it stacks up:

Redtop manifold.

45mm intake runner diamter.
67mm throttle diameter.
67mm wide flare on end of runners, with approx 45 degree bevel.
Shortest runner is 230mm long, each one after that is slightly longer and more bent.
approx 130 degree bend overall in intake runners.
approx 50mm from plenum wall to end of intake runners.

comments:
Base manifold part is made from rubber/alloy, and has a nasty looking transition from the 45mm round runner to 49x40mm port entrance. Could be flow improvements by looking at that part? May be a good reason for it I guess, not sure...
Interesting that runners are slightly different lengths, plenum design possibly compensates for this?


Altezza manifold

46mm runner diameter
72mm throttle diameter
approx 70ish degree bevel on intake runner ends
approx 250mm intake runner length, lengths are near equal for all 4.
approx 30mm bend 'down' in intake runner, and 30 degree bend 'up' in base manifold part.
approx 40-50mm from plenum wall to end of intake runners, looks closer than redtop but hard to measure.

comments: Interesting that there's a large resonance chamber built into the bottom, that isnt connected to the manifold air at all. It must resonate at a certain RPM to either influence helmholtz resonance, or maybe dampen a particularly noisy/harsh vibration? It's also got the same nasty looking bottom manifold piece. Plenum volume is a bit larger than redtop.
Plenum design is apparently quite good, local engine builder uses them on the end of his quad throttle setups, reckons it's a brilliant design. (Was used in Altezza touring car this way)

quads

runner diameter goes from 88 > 50 > 45 > 48 > 53x43mm at port entrance.
4x 45mm throttle plates.
88m flare at end of intake runners, 270 degree bevel on end.
all intake runners exactly same length.
105mm long trumpets, 75mm long throttle section, ~60mm long manifold.
overall runner length is approx 240mm. (I'm gonna double check this, I'm sure it was longer ie 300mm...)
Approx 30 degree angle to the head where it bolts on... to match the angle of the ports.

comments: Can see straight down to the valves when throttles are open, as opposed to other manifolds which are 'bent'. Which should be good for flow I guess.

Matching of throttle body to manifold isnt the best, manifold and throttles will need die grinding slightly to match properly with standard blacktop 4age throttles. (Dont think I've got them on upside down or anything....)

Port entrance diameter on base manifold is larger than the others, larger than ports possibly? (havent checked yet)
Lots of space in engine bay for longer runners. I may make a spacer to go longer again, to give overall runner distance equal to or longer than standard manifolds.
It seems odd to have the runner diameter tapering in and out.
As you're speeding up the air towards the 45mm throttle plate... And then slowing it down again before the port? Which seems like exactly what you dont want to do.
Possibly of more of a benefit when larger diameter throttles are used, eg. 50mm throttle plates to keep continous diameter to the port entrance?




edit: measurement at port should read 49x40, my bad.



edit: Aaahhh, my picture might be misleading in terms of how much it flares in/out, here's a cad drawing. Top one flaring out, bottom one how it would make more sense IMO? (No flaring back out, slight taper inwards? Even more so, if the port is 49x40 instead of 53x43)