engineermike

This can be a fun discussion. While restriction does cause some amount of boost, it's a small percentage. Pressure increases the density inside the cylinder, which is not a measure of restriction. If your intake and heads had zero restriction, you still want boost to increase the density of the charge.

Not exactly. A more efficient compressor will generate boost with less heat, while taking less turbine power to do it. Less turbine shaft power plus a larger turbine generates less exhaust/drive pressure. This reduces pumping losses and increases airflow at the same boost level, increasing power. If you are fuel system limited, you could reduce boost and make the same power.

cptbimes

Ya got me. Didn't pay attention at the start of the thread. Went back and read it though just now.

I should have put "restriction" in quotations. The air flowing into the cylinders from the turbine outlet gets "backed up" in the cold side of the turbo system. Depending on where you reference your boost signal, the pressure reading will vary depending on the velocity of the gas at that particular point. Smaller passage way = more velocity = lower pressure.

Now onto your compressor talk. You're getting into way more than just A/R ratios. You're marching onward into compressor maps, trims and efficiencies where I was daydreaming in themal and fluid dynamics. So I'll just have to sit back and watch here.

CoreyMS

I've seen the bone. An attempt to work with the DI for more fuel is in progress.

engineermike

Here's a fun mental exercise...

Say you have a high performance engine that has >100% Volumetric Efficiency, and it produces 500 hp at WOT. Now, what happens if you double atmospheric pressure? If you answered, "the power will double", then we agree. Using density=PV/RT, so if you double the pressure, the density doubles, the mass flow rate doubles, and the power doubles...but it still has 100% VE. So, you have doubled the pressure in the intake manifold but you have not added any restriction. You also have doubled the pressure on the exhaust side.

While a typical OEM turbo system will have up to 3x boost in exhaust pressure, a good race system can be at unity or below. Imagine running 20 psi boost with only 16 psi exhaust pressure. This would be a slightly better scenario than doubling atmospheric pressure as described above.

Make sense?

cptbimes

Of course.

You ever been to a 10.5 Outlaw race?

engineermike

Nope. When I was going to the track regularly, it wasn't to watch.

flyinfry

Has any tried the Throttle Body upgrade yet? I wonder if our intake would need to be ported to match the opening of the Throttle Body. Do you need a tune to take advantage of the bigger Throttle Body?

Matt6951

save your money, 3mm on a forced induction set up is worthless on a stock engine. plus its bbk, not my favorite. they are on the cheaper end of the quality scale.

flyinfry

Thanks Matt6951! I'm used to building 5.0 Mustangs where the Throttle Body's actually made a difference. I remember the BBK ones always having some weird problems that the other ones didn't.

PetroBoost

+1 For re-using as much oem as possible to keep the costs down.

Also, being a 2013 "better" turbo owner is there any "free" hp/torque that can be gained by porting out the stock exhaust manifolds?