Elbow is about 10’ of extra length
Equivalent length tables can be tricky because the loss depends on pipe diameter, bend radius, velocity, and density. I didn't come up with much when applied to the speeds involved here because it's well outside of what's commonly used in HVAC duct sizing, but I found some loss factors that can be used with the velocity and fluid properties that might work better and it came out to about 2 equivalent feet in this case.
I only have basic fundamentals that I am applying from some old fire service pumping hydraulics class. I think you guys have a few more education hours invested
With that thought I am just thinking everything is incremental in friction loss from getting from the high pressure side to low pressure side. My CAI design was use the bigger XJ filter, a larger 3” pipe..keep it short as possible and draw air from outside the engine compartment. Luck would have it I only have the 90 turning down into the throttle body.
Ran some numbers for rpm at peak power, assuming VE of 1 (which will inflate the numbers somewhat)
I'm fairly confident in the tube number, the elbow numbers might be inflated because I didn't take off my intake tube to measure the ID there, but it does look like they increase a bit before entering the throttle body so I ran them with a diameter halfway between the 50mm tube and the 60mm TB. The accordion boot requires some pretty extreme extrapolation because the depth of the folds puts it well outside the widely available data.
The number suggest that the 5" of accordion boot is about equivalent to the entire 16" tube, and that both combined are only about 75% as much as the two successive elbows feeding the throttle body. In total, about 0.7psi, which means a reduction in the maximum available MAP by the same amount.
If you cut the elbow bends down to just 1 and used a true long radius elbow (bend radius to diameter ratio of 1.5, assuming there's room under the hood), used a flexible coupling instead of the accordion and kept the ID to 60mm matching the TB throughout, you can cut the losses by a significant proportion and bump the MAP by about half a psi. The engine guys will have to tell us how much power that's worth.
I ran the numbers for a duct internal diameter of 68mm and it only changed it by 0.07 psi so I think beyond 60mm is a diminishing return from a pressure loss standpoint, and even 60 may be past it already from a power standpoint.
EDIT: Updated screenshots with final pressure values in kPa because that's how Jezza refers to MAP in his dyno test video.
