Das Beast: My E30 track / street build

[Digitalwave]

I love science.

[dvallis]

#Facepalm! Of frigging course. You need to open the runners in order of firing sequence. That makes total sense. Thanks Digger.

Like you said, flow looks a bit uneven in some runners. I think we'll still stick with OEM as it's a known quantity.

[digger]

here are all runners drawing



firing orders



runners 3 and 6 drawing



runners 1 and 4



the difference in mass flow between them is very small. it would run ok atleast a from a distribution perspective

obviously a transient analysis simulating the pulses is better way to do but this is a cheap and nasty way to get an idea

[digger]

the reality is all runners arent flowing at the same time. the stock stuff is garbage when you do that as OE does not use pressure revovery except the S54 CSL. the boundary conditions are incorrect with all runners flowing. obviosuly if it does have pretty close to equal flow in case of all runners case then its going to work ok. but its a pretty meanginless analysis IMO as manifolds that fail can actually work pretty well.

here is stock a quick and dirty model. air wont turn the corner to 3 and 4. when you look at the firing order 3 and 6 are drawing at same time so there is potnetial for 6 to rob from 3 but its much less pronounced than the all runners analysis. the stock one isnt great even with the two runner analysis

[dvallis]

Here you go, 20 psi inlet pressure. You can see there is pressure in all the runners, just bugger all for flow in #1. It's pretty clear from the S54 intake above that you have to design with flow in mind. The S54 has a throttle body angle and housing that directs flow evenly across the runners, which is captured smoothly by the velocity stacks. Makes a lot of sense when you see it like that.