3SGTE Twin Charged

[Duk]

Ahhh twin charging, is there a more controversial topic amongst the 4AGZE community? Then there is the rest of the automotive world .
A few things to consider:
1: A piston engine is an air pump. But, it is a pump with too many things moving in too many different directions to be a particularly efficient pump.
2: A positive displacement supercharger is also an air pump. It moves a given amount of air per revolution of the pump/super charger. That assumes (the mother of all fuck ups!) that there is no internal leakage, and there always is.
3: Using Eaton/Magnuson's research, PD SC's efficiency go's up (less internal leakage) with SC RPM, but go's down with boost pressure (more internal leakage). Yes the factory SC12/14's aren't Eaton/Magnuson's, but the theory should be applicable.
4: Centrifugal pumps/superchargers(turbo chargers) are the most efficient air pumps available.
5: Industrial air compressor research (where a lot of supercharger research is derived) always talks of "Free air delivery". That is, the unrestricted maximum airflow that the 'air pump' can ever use.
This is where pressure ratios come into it. A pressure ratio of 2:1 gives a discharge/manifold pressure of 14.7psi/1Bar. But this is really an inlet manifold pressure of 29.4 psi/2Bar.
14.7psi/1 Bar (typical atmospheric pressure at sea level) at the inlet of the SC (or a naturally aspirated engine, for that matter) but there is 29.4psi/2Bar of absolute pressure in the discharge/inlet manifold.
6: If you add 7psi/0.5Bar of turbo delivered air to a PD supercharger that supplies a 2:1 pressure ratio then there will be 21.4psi/1.5Bar (instead of the usual 14.7/1Bar) at the SC inlet and this results in 43.4psi/3Bar (absolute) at the discharge/inlet manifold. This assumes (the mother of........) that there is no internal leakage of the PD SC (and there always is ).

Incidentally, over the years I have read of race bread engines (especially from the turbo era of Formula 1) that, apparently, achieved higher inlet manifold pressure than exhaust manifold (back) pressure. This seams unlikely (given the inevitable loss's through the whole system). But, a twin charger arrangement is a definate way to achieve inlet pressure that is higher than exhaust manifold/turbine housing back pressure. The advantages for reduced combustion chamber temperatures from residual exhaust gas, and so reduced engine knock, can't be ignored.

My 2 cents

[feral4mr2]

if doing this way, will the turbo air flow choke down at supercharger during high boost(14 till 30psi)? this make sense but i am consider about the life span of the supercharger too as it will receive hot air from turbo. did you disable the supercharger at high boost when going this route? i think we can't right as once SC stop spinning the charged air from turbo hardly can pass thru the supercharger right?

i only ran at 18psi, the turbo isnt pushing much into the s/c to make that boost (though i never actualy measured how much), so the charge air into the s/c IMO isnt all that hot.
i left my s/c controled via the ecu, so no i didnt disable the s/c at full noise.

a couple hardware faults had me pull mine apart, but i am longing to set it up again.