FI Experts, can someone explain the whole process of supercharging?
06-20-2011, 08:46 AM
#1
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FI Experts, can someone explain the whole process of supercharging?
Is the Comptech, Vortech, SOS blower all centrifugal types?
The basic theory is that a supercharger increases the volume of air entering the engine by "compressing" it first so the engine becomes more efficient. The compressor itself is driven by the crankshaft connected by a belt.
So for our s2000 application:
Air enters the intake, gets pressurized by the charger > flows through the aftercooler > cool air enters the intake plenum and gets used by the engine
So when we are at partial throttle, what happens? at idle? what about when we go WOT and let off the gas? What part does the BOV play in this type of scenario?
btw the reason I'm asking is I'm trying to think of ways to increase efficiency
The basic theory is that a supercharger increases the volume of air entering the engine by "compressing" it first so the engine becomes more efficient. The compressor itself is driven by the crankshaft connected by a belt.
So for our s2000 application:
Air enters the intake, gets pressurized by the charger > flows through the aftercooler > cool air enters the intake plenum and gets used by the engine
So when we are at partial throttle, what happens? at idle? what about when we go WOT and let off the gas? What part does the BOV play in this type of scenario?
btw the reason I'm asking is I'm trying to think of ways to increase efficiency
06-20-2011, 08:56 AM
#2
Yes, they are all centrifugal SC's, from the same companies. This happens 100% of the time:
Air enters the intake, gets pressurized by the charger > flows through the aftercooler > cool air enters the intake plenum and gets used by the engine
But there are situations where the charger is shoving more air into the engine than we want it to. You listed some examples:
at partial throttle? at idle? what about when we go WOT and let off the gas?
The BOV is plumbed into a vacuum line. When you are not pressing the gas enough to cause the engine to accelerate significantly, then the vacuum line sends a signal to the BOV to open. That vents off the excess pressure. This takes place when you are cruising at a constant speed, or when you let off the gas (from WOT or just to slow down) or when the car is at idle. At partial throttle, if the car is accelerating, the BOV is closed. But if it's at partial throttle and just cruising or slowing down, the BOV is open.
In another thread, someone mentioned that the roots type blowers have an internal valve that opens in these situations. They allow air to bypass the SC entirely. So instead of the compressing the air first and then blowing it off before it reaches the engine, the air just goes straight to the engine uncompressed.
We could modify the centrifugals the same way by putting a larger BOV in front of the SC that routes air around it when not boosting (and blocks the air going into the SC). Someone who knows more than I do can tell you if that would make the SC more efficient because it doesn't have to work to compress all that air.
Another way to do it is to have a clutch between the SC and the pulley system. Disengage the clutch when you don't need boost, and that would remove the parasitic drag the SC places on the engine. (SC systems can consume a lot of HP just turning and compressing air.)
Another thing to consider is that by compressing the air, the SC raises its temperature. Hot air is less dense than cool air, and makes less power. So whatever you can do to lower the intake air temp will make more power. Trying different aftercooler / heat exchanger setups may lead to more power. In a recent thread, some folks mentioned that you can also drop the air temp going into the SC by using a cold air setup. That's another opportunity.
Air enters the intake, gets pressurized by the charger > flows through the aftercooler > cool air enters the intake plenum and gets used by the engine
But there are situations where the charger is shoving more air into the engine than we want it to. You listed some examples:
at partial throttle? at idle? what about when we go WOT and let off the gas?
The BOV is plumbed into a vacuum line. When you are not pressing the gas enough to cause the engine to accelerate significantly, then the vacuum line sends a signal to the BOV to open. That vents off the excess pressure. This takes place when you are cruising at a constant speed, or when you let off the gas (from WOT or just to slow down) or when the car is at idle. At partial throttle, if the car is accelerating, the BOV is closed. But if it's at partial throttle and just cruising or slowing down, the BOV is open.
In another thread, someone mentioned that the roots type blowers have an internal valve that opens in these situations. They allow air to bypass the SC entirely. So instead of the compressing the air first and then blowing it off before it reaches the engine, the air just goes straight to the engine uncompressed.
We could modify the centrifugals the same way by putting a larger BOV in front of the SC that routes air around it when not boosting (and blocks the air going into the SC). Someone who knows more than I do can tell you if that would make the SC more efficient because it doesn't have to work to compress all that air.
Another way to do it is to have a clutch between the SC and the pulley system. Disengage the clutch when you don't need boost, and that would remove the parasitic drag the SC places on the engine. (SC systems can consume a lot of HP just turning and compressing air.)
Another thing to consider is that by compressing the air, the SC raises its temperature. Hot air is less dense than cool air, and makes less power. So whatever you can do to lower the intake air temp will make more power. Trying different aftercooler / heat exchanger setups may lead to more power. In a recent thread, some folks mentioned that you can also drop the air temp going into the SC by using a cold air setup. That's another opportunity.
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