Three-stage boost for 4-cyl engine?

[J-Ri]

I have a 2004 Chevy Cavalier with the 2.2L Ecotec. I already have a supercharger and charge air cooler on it. What I'm contemplating is adding ram air and an "e-turbo". Since the boost is multiplied in each stage of boost, any increase into the throttle body would be multiplied considerably before being forced into the engine. The "e-turbo" would be homemade, utilizing a 12v dc motor I have just taking up space in my garage. I know they work on very small naturally aspirated engines, but I don't know about an engine that's already sucking in the air of a small N/A V8. I have many different 12V DC motors, ranging from tiny actuators up to a starter motor for a large V8 engine, so whatever size I need, I probably have. I have a couple blower motors that pull 16A and 27A with no load, that have the impellers still on them. I would like to use one of those if either, or possibly both, would be powerful enough.

Facts about the engine:
2.2L 4-cycle
14 PSI of boost from the supercharger
At it's 6,800 RPM redline, I calculate that the supercharger sucks in about 520 CFM.

How large a motor do I need to build about 1-2 PSI before the supercharger? Keep in mind the "e-turbo" would have minimal boost into it from the ram air. I will build a controller that opens the bypass valve on the supercharger to maintain a maximum of 18 PSI, so I'm not worried about over-boost or the wide range of boost that I'm sure this setup would (probably?) create

How much would the ram air help? I already have more power than the tires can handle below about 40 MPH. The gear-limited top speed is 148 MPH. I will be taking the car on a road course next summer, where I expect to stay between 70 and 130 MPH. I also drag race and hit about 105 MPH at the 1/4 mile (maybe more depending on how much boost this adds). The left front headlight assembly can be removed easily and I can fabricate a funnel/pipe to go in it's place and feed into a custom air filter housing for track use, on the street I won't have any use for extra boost anyway.

I should add that the main reason for going this route, for now, is to alleviate some of the heat of compression in the supercharger. I could go with a .1" smaller pulley, but the IAT has gone as high as 170°F and would have gone much higher if I hadn't let off the gas (that's measuring after the water-to-air cooler). I am currently designing a water/methanol injection system that should help a lot, after that is installed I will probably switch to the smaller S/C pulley. Down the road I will either switch to a turbo or twin-charge setup, but I can't add much more power before I need stronger internals.

Thanks in advance for any help!

-Jason

 

[Navin A S]

The size of the motor you need to build 1-2 PSI before the supercharger would depend on how much air you are expecting it to move. A DC motor with 16A-27A of no load current should do the job if it is able to move enough air. You would also need to make sure that the motor can handle the higher boost levels and temperatures that it will be exposed to. You would also need to make sure the motor is properly sealed and protected from moisture and debris. The ram air would help a bit, but it would not provide a substantial increase in power. It would likely provide a slight boost in power at lower speeds, but the main benefit would be to reduce the temperature of the air entering the engine. The cooler air allows more oxygen to enter the engine, so it can burn more fuel and produce more power. If you do decide to go with the ram air and e-turbo setup, you will need to tune the engine and adjust the boost controller to ensure that you are not over-boosting or exceeding the safe limits for your engine. It is also important to ensure that the motor is properly sealed and protected from moisture and debris.