Nice Setup Porter, I would recomend routing the air fiter out of the hot side of the engine bay, and increasing the size of your IC pipes, it is certainly a unique setup.
The thing with turbos is interesting. Nick was right on the money.
To go a bit deeper, your turbo is a compressor and a pump. Superchargers are only pumps (eaton/roots styles). So with a supercharger, a bigger pump makes more "boost" and more power. The 7m injests 3 liters of air ever two revolutions of the crank. That is what makes it a 3 liter and this can NEVER change. So if you wanted 14.7 pounds of boost from a perfectly efficient supercharger, you would just get a charger and spin it so it pumps 6 liters of air for every two crank revs.
PV = nRT.
P is pressure
V entering the engine is ALWAYS 3 liters,
n is the number of gas particles entering the engine.
R is an Ideal gas constant,
T is temp.
So with the supercharger, you try to squeeze 6 liters of air into the 3 liter engine and you get 3 liters of air, double the air particles (n) and double pressure. sits atmosphereic pressure is about 14.7, that gets you 14.7 psi.
That only works if the pump is 100% efficient and does not heat the air at all, hence intercooling.
Turbos are neat.
The end effect of a turbo is like that of a pump, but turbos can actually blow 3 liters of compressed air into the 7m. 14.7 psi coming out of the volute of a turbo can get cooled, and enter the engine as 14.7 psi, 3 liters. A pump could not achieve this, a pressure between the pump and engine is simply a measurement of the reistance from the engine to the increase volume of air the pump is trying to move.
All of this talk of air in liters per two revs is a bit sloppy, so smart folks decided that there should be a better term, so airflow got the units of pounds per minute, or if you know the density of the air on any given day, cubic feet per minute can be calculated. That's CFM. Realistically, CFM and lbs/min is all that matters.
lbs/min of airflow has a neat way of helping you estimate horsepower, kind of like how the cc size of injectors gives an estimate of power production. The injector trick works only with 6 cyl engines and varies based on the BSFC values for the engine, but still, 550 cc injectors should make about 550 hp before being tapped out.
Well, to make that 550 horsepower, you'll need ROUGHLY 55lbs/min from that turbo.
So. A CT-26 blows 18 psi out its snail shell and into a nice intercooler. After getting chilled to a reasonable temp, the engine injests this air and makes some power. Well, a T-88 can make 550 hp with 18 psi. That's because if you simply spun a T-88 up to a nice 90,000 rpm or so and supplied 55lbs/min into it's inlet, you would read a gauge pressure of about 18 psi on the volute. You could spin a CT-26 up to 160,000 rpm and supply 55lbs/min to the inlet, and it simply could not flow all of the available air through the restrictive impeller wheel.
Similarly, if you put a restriction on either of the turbos to regulate pressure coming out of the compressor housing to 18 psi, you would find that the T-88 sucks somewhere around 55 lbs/min through the inlet. The CT-26 would be sucking somewhere around 30-35 lbs/min. That is why CT-26s have trouble making the big numbers. You can play around with shaft rpm to tweak the pressure vs airflow numbers a tad and that's how they make compressor maps. Here's a map of your T-66
The boost on these maps is listed as a pressure ratio, where 1 is 1 atmosphere, or 14.7 psi. So in order to make your 600 hp, you'll need to spin the turbo up to a little over 100K rpm and have a pressure ratio of 3:1. That's 14.7X3 = 44.1 psi absolute. so that's 29.4 psi on the gauge to make that power.
Down at 9 psi, your looking at an absolute pressure of 23.7 psi and a pressure ratio of 1.6:1
Looking at the map above, 1.6:1 should be spining the turbo about 56K RPM and pushing 30 lbs/min or so. Basically, the T-66 running 9 psi should make similar power to a stock CT-26 pushing 18 psi. The car would certainly feel sluggish down low because the T-66 spools so much later.
Sorry for the novel, but I thought I'd really explain what's going on with boost and airflow etc. Of course there's more, because a CT-26 can blow 29.4 psi out it's snout, but the 7m just sucks that air down, so the intake manifold will never show that kind of pressure because the turbo is acting as a pump, and there isn't enough restriction to flow on the engines side to maintain that pressure.
Any Questions?
-Jake
