Supercharging

[Ian Szgatti]

I would be interested in hearing from anyone who has concidered building a mild supercharging system. Ideally it would be capable of supplying a small amount of boost in mid to high rpm while still allowing stock PCM fuel ratios... I guess I mean, a mass air-flow sensor must be able to read the volume of air, and the fuel injection system must be able to provide the proper amount of fuel.

If you would like to just throw out ideas based on your own imagined ideas, feel free. Some engines allow for completely custom backyard set-ups... like the 3300 in an olds ciera for example... while not entirely practical, I'd still like some input, I'm not going for practical. It doesnt matter how crude you imagine the devices to be... and I dont want to hear.."just buy a supercharger"... thats obvious. The point here is to fabricate and improvise using a stock NA engine without making it run to lean and destroying it.

[MagicRat]

A while back, I suggested hooking up a leaf blower to the intake hose of a car. (Stop laughing)
Some of the most powerful cordless blowers use 12 volt, and blow 400 cfm, which would be enough for smaller engines. Sure, they will only provide 1-2 psi, but they would provide a small power boost,(no lean out condition to worry about) they could be hooked up to a gas pedal switch where they only activate at full throttle, and when they are not spinning, the engine could easily suck the intake air past the stationary fan vanes.

I also thought of using a mondo 2 stroke back pack blower for the drag strip. They provide much more cfm than an electric, and enough pressure to easily blow rocks, gravel etc
Just imagine, pull start the blower and wind it out just before the bleach box......cool, eh?

[KiwiBacon]

An electric supercharger is only capable of supplying boost to get an engine off idle. Take a look through the "forced induction" forum for a breakdown of how much power it takes to create boost.

A small petrol engine may be your best option. Completely uncoupled from engine speed and capable of good power for the size (intermittent use only for cooling reasons).

[UncleBob]

I think your question isn't so much about the fabrication necessary to install the supercharger, but how the engine management needs to be compensated for?

The installation is simply finding the right-sized SC for your project and mounting it. Paxton style SC's are a little easier to make work, due to its just an added component to the accessories. Twin screw types, more complicated, depending on what you're starting with.

The engine management, there are calibrated MAF's you can buy that are calibrated to a set of larger injectors, without any modifications to the stock computer. They work mostly well....they handle the fuel metering well, but some situations can cause too much timing under boost (its a very complicated subject)

You could of course go with stand alone, or a piggy back setup. Many stock ECU's have a fair amount of adjustability....but again, without a very specific example, every car has its own limitations and options

[GreyGoose006]

i've long thought about mounting a small air compressor in the bed of a truck and have it fill a 10 gallon tank to about 30-40 psi. then under full throttle (and only under full throttle) have it release air at a predetermined pressure into the intake. it could be fully adjustable from 0-whatever psi you wanted.

the setup i imagined would work similarly to an airbag or airbrake system.

you would of course have to know the flow rate of incoming air into the engine. at least the ideal flow rate.
then calculate the flow rate needed to provide a certain pressure, and get a valve to restrict the flow to the ammount you determined.
this would only work at full or near full throttle, because if the flow past the valve remained constant, the pressure would be higher at lower rpms.

good idea?

[534BC]

A small block can suck it dry in less than a second.

[UncleBob]

10 gallons is roughly 38 liters. 5.7L engine would pull that volume in less than 14 revolutions. That doesn't compensate for the pressure ratio, but lets just say, it wouldn't last long even at 2000psi

[GreyGoose006]

even at very low psi?
i guess a bigger tank could be used at higher pressure.

[534BC]

An engine is a huge air pump, trying to store the air for it isn't a good idea. Storing it in liquid form is ok and works well.

[GreyGoose006]

but in a small engine it might work.
around 1.5 liters

although i see your point

[UncleBob]

1.8L at 38L is a whopping 42 revolutions of the crank.

If you're talking 8000+ RPM's we're talking some serious flow here folks. how many times can you divide 42 revs into that? A lot. A mucho lot

[Ian Szgatti]

Originally Posted by UncleBob

The engine management, there are calibrated MAF's you can buy that are calibrated to a set of larger injectors, without any modifications to the stock computer. They work mostly well....they handle the fuel metering well, but some situations can cause too much timing under boost (its a very complicated subject)

great answer... i see what your getting at here, and having read each reply, my goal has become a little more clear. that is to take the benifits of blowing air in, but only use from either a stand still, or at higher rpm when the engine starts to struggle to fill it's cylinders.

really, there are so many complicated variables... especially when it comes to compression/timing, etc. I do appreciate the ideas though. By the way, I have seen a leaf blower in action provide ten horsepower on a dyno... it was goddam halarious to see this stupid looking leaf blower on the intake, but it worked.
Unfortunately, the blower would probably not be easy for the alternator to power, therefor it would likely cause it to run near full field current, which the engine would notice as it struggled to turn the alt pulley... there are always trade offs because you can't get free energy.

[GreyGoose006]

what about the fan and motor from an AC unit?
that would be able to push a huge ammount of air easily.
the power required would be insane, but it might work for a while

[KiwiBacon]

Originally Posted by GreyGoose006

what about the fan and motor from an AC unit?
that would be able to push a huge ammount of air easily.
the power required would be insane, but it might work for a while

While such a fan can shift air, it can't create much of a pressure increase. It's pressure increase which is going to compress the air and allow more air molecules into your engine.

[UncleBob]

all the electric fan ideas have been played with many times. they just aren't realistic. You would need so much amperage to drive a electric air displacement device to actually see a note-worthy gain, that it would require several batteries, and you'd have only very short bursts

It would also be expensive. NOS would be a way cheaper option if you don't mind having the very limited use of said power increase.

If you want sustained power increase, you need "traditional" SC or TC