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We know from the PCM's turbo flow model the stock turbo flows about 24kg/min tops.

Now it's time to pull up our favorite simple online flow calculator and we see that With the 43mm plastic funnel in the stock hot-side boost pipe, the velocity in the funnel is mach 0.643 and the pressure drop is 323mbar, or 4.68psig -> our max boost expectancy with the stock piping is 1.34bar or 19.4psi @ 6500. Still makes sense, uh?

With 2.5" boost pipes the stock throttle at 57mm is the next bottleneck. At 82° max angle the effective area is 2197mm² which correspond to an unobstructed tube of ø52.9mm. Back to the gas flow calculator,
Worth pointing out that the flow calculator you are using is not applicable to control valves.

You appear to be trying to work out the pressure drop across the butterfly control valve when it is in the fully open position.

You need to do a Cv (flow coefficient) calculation. Specifically a gas Cv calculation.

You have the mass air flow rate at 24kg/min.
You can usually get the Cv of the valve at the fully open position from the manufacturer. Knowing the max Cv and the mass flow rate you can calculate the pressure drop. You can do this for each of the TB sizes and then compare the pressure drop.

The calculator you have linked is based on Bernoulli’s equation and assumes a constant density, neglects the length of piping, surface finish and bends.
 

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Worth pointing out that the flow calculator you are using is not applicable to control valves.

You appear to be trying to work out the pressure drop across the butterfly control valve when it is in the fully open position.

You need to do a Cv (flow coefficient) calculation. Specifically a gas Cv calculation.

You have the mass air flow rate at 24kg/min.
You can usually get the Cv of the valve at the fully open position from the manufacturer. Knowing the max Cv and the mass flow rate you can calculate the pressure drop. You can do this for each of the TB sizes and then compare the pressure drop.

The calculator you have linked is based on Bernoulli’s equation and assumes a constant density, neglects the length of piping, surface finish and bends.
I agree the method is not perfect. The goal was to get a ballpark idea and to make rough comparisons to see if there would be any benefit at max aperture and max flow, and in first approximation it appears there may be.

It happens the numbers that came up reasonably match the observed manifold pressure for the stock piping and TB. This gives at least some confidence the method is not completely off.

That being said, I made that study as good as I had time for. I have access to CFD software and my original intent was to model all three throttle bodies and run flow simulations to get accurate results. I save that for another day.

I’m testing the large throttle on the car now.
 

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The stock turbo is a garret 2263. Just to get the convo more focused.


16 Ford Focus RS Grey
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Has anyone measured the dimensions of the plastic flow inhibitor?

My wife got me the Damond kit for my birthday. It has the wiring and hoses to replace the TB with the Mustang one. I installed it and kept the stock hoses for the time being, which means Ikept the flow inhibitor/velocity raiser. Trying to think through if there is any interim solution I can do while keeping the stock pipes until I get replacements. I should have measured everything myself, but any car time I get is me working around my work schedule and my son’s schedule.

349785
 

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43mm held over 50mm. There is no other name I can think of for that thing other than “flow restrictor”.
 

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