Forced induction by other means

[Bell040]

just a thought...

if a supercharger simply raises the air pressure in the intake.... why can't you just plumb up some tubing that goes to the intake from an air (or pure o2) cylinder with a pressure regulator. Then you could add pressure on demand with a valve.

seems like a no-brainer, but there must be a reason that noone does it this way.

thoughts?

[06blownSS]

This is not a good idea lol. You cant just add pressurized air into the intake to make more power. Power is made by adding air and fuel. I cant imagine what your ecu will think if it senses a burst in air pressure all of a sudden with no extra fuel to compensate

[stanwilliams]

that is kind of what nitrous does with a little nitrogen to buffer the mix.

[nova]

Volume/pressure prohibitive if I had to guess.

Work through the math to see just what volumetric flow rate an LS3 has at say 4000rpm.

You can then backsolve to determine what volume of tank you would have to have at what pressure in order to supply that flow rate @ say 20 psi (6psi boost) for any amount of time.

Not having worked the math, I'd be willing to bet my eng. degree you're looking at either a big tank or one at REALLY high pressure, neither of which is very practical.

Now if you just want a few seconds of boost, then that might be feasible.

[DGthe3]

Originally Posted by Bell040

just a thought...

if a supercharger simply raises the air pressure in the intake.... why can't you just plumb up some tubing that goes to the intake from an air (or pure o2) cylinder with a pressure regulator. Then you could add pressure on demand with a valve.

seems like a no-brainer, but there must be a reason that noone does it this way.

thoughts?

Thats essentially the premise behind a dry nitrous oxide system. Nitrous has about 3x the oxygen that air does but is much easier to work with than pure oxygen. As others have said, its not specifically the pressure its the amount of oxygen. Air at 7psi (over atmosphere) has 50% more oxygen than the same volume at atmospheric pressure. You can get the same effect by adding a relatively small volume of pure oxygen, or a slightly bigger volume of N20 (nitrous oxide).

[Bell040]

PV=nRT (ideal gas law)... (btw, I'm a ChemE)

As "P" increases, "n" increases

n = number of air molecules (air is 79% N2 and 21% O2)

So, if the reason for a supercharger is to increase the number of oxygen (O2) molecules supplied to the throttle valve... knowing that the PCM uses the O2 sensor to control the amount of fuel added to the chambers (to keep the reaction optimized)...

Then adding O2, by any other means, should yield the same result.

Originally Posted by nova

Volume/pressure prohibitive if I had to guess.

Work through the math to see just what volumetric flow rate an LS3 has at say 4000rpm.

You can then backsolve to determine what volume of tank you would have to have at what pressure in order to supply that flow rate @ say 20 psi (6psi boost) for any amount of time.

Not having worked the math, I'd be willing to bet my eng. degree you're looking at either a big tank or one at REALLY high pressure, neither of which is very practical.

Now if you just want a few seconds of boost, then that might be feasible.

A 3000psi air cylinder will handle very high flow rates for a very long time (again PV=nRT).

... and even if you cant get to 6psi..... It should still increase the pressure by a very decent amount.


I am not going to try it and void my warranty... I was just wondering if anyone else has tried this in the past before spending $7000 on a fancy air compressor... "permanent" air compressor I might add.

[Bell040]

Originally Posted by 06blownSS

This is not a good idea lol. You cant just add pressurized air into the intake to make more power. Power is made by adding air and fuel. I cant imagine what your ecu will think if it senses a burst in air pressure all of a sudden with no extra fuel to compensate

you would add the air (or O2) line before the throttle valve and MAF sensor, but after the air filter...

the PCM would compensate... just as it does with ram air or a supercharger

and if it doesn't, you would just have to put a second valve on the air line that mimics the throttle valve

[SoloSK71]

Remember that FI is just that. Forced in, with some kind of backpressure that prevents the increased volume of air from flowing back outside the engine.

In an SC or turbo the spinning fan/lobes are this prevention, with a BOV there for the times there can be an overpressure.

With a nitrous system, the only pressure is enough to force the nitrous out against atmospheric pressure, the flow of air into the engine does the rest.

Oxygen injection systems try to combine this with the FI part. You would (I think) get a small increase in O2 content of the air, similar to running at lower altitude (quite possibly MUCH lower altitude) but not the same kind of boost as in an FI or nitrous system.

Exceptions to this occur when the 'natural' air pressure is already much higher than normal. RAMJET and SCRAMJET systems where you are either feeding LOX or O2 and there is a HUGE pressure differential from the front (intake) to the turbines or combustion chamber.

I think it would be a simple and interesting experiment to hook an O2 bottle up to the air intake on a basic EFI engine at high altitude and see what the before and after numbers are.

- SK

[nova]

Originally Posted by Bell040

PV=nRT (ideal gas law)... (btw, I'm a ChemE)

As "P" increases, "n" increases

n = number of air molecules (air is 79% N2 and 21% O2)

So, if the reason for a supercharger is to increase the number of oxygen (O2) molecules supplied to the throttle valve... knowing that the PCM uses the O2 sensor to control the amount of fuel added to the chambers (to keep the reaction optimized)...

Then adding O2, by any other means, should yield the same result.

A 3000psi air cylinder will handle very high flow rates for a very long time (again PV=nRT).

... and even if you cant get to 6psi..... It should still increase the pressure by a very decent amount.

I am not going to try it and void my warranty... I was just wondering if anyone else has tried this in the past before spending $7000 on a fancy air compressor... "permanent" air compressor I might add.

AeroE here

Yeah, now that I think about it, you're probably only talking 350-400 cfm @ 4000.

I've been dealing with turbines and their huge mass/volume flow rates I'm out of practice swagging recips.

[14pilot]

How about ditching the intake system entirely and doing a variation of a Directly Injected Engine that also directly injects high-pressure air into the cylinders along with the fuel?

Use the engery that was required to run the intake valves and instead, use that energy to run a very large air compressor?

Move this to Half-Bakery.com?

[nova]

As long as we're talking unorthodox ideas, how about a hybrid recip/gas turbine system.

Basically add a turbocharger with a modified install to the recip. The compressor output would be split between the recip intake and the turbine intake. In between the compressor and the turbine would be a small combustor with a fuel injector. Using some sort of solenoid actuated valve setup, your recip exhaust would go to the turbine until it got spooled up, at which point you would ignite the combustor and re-direct the recip exhaust to somewhere else.

At that point the turbocharger is a self sustaining gas turbine engine, providing a continuous boost to the recip.

Completely and utterly impractical but it would be cool to say "MY Camaro has a turbine in it."

[BlackinBlack]

Using compressed air would work...but two major issues. One is flow. The CFM needed would require some major piping sizes. 2nd would be capacity the volume of air would require some major tanks. NOS is a liquid and the amount of oxygen per volume is a bunch higher than straight air. So there is no real advantage to use bottled compressed air. For compressed air use a infinite air bottle AKA supercharger or turbo.

As for liquid O2. The germans tried it in WW2. If you attempted it please record the attempt because the resulting explosion would be awesome.

[Bell040]

Originally Posted by SoloSK71

.....

Oxygen injection systems try to combine this with the FI part. You would (I think) get a small increase in O2 content of the air, similar to running at lower altitude (quite possibly MUCH lower altitude) but not the same kind of boost as in an FI or nitrous system.

So there are O2 injection systems out there?

[Bell040]

Originally Posted by SoloSK71

Remember that FI is just that. Forced in, with some kind of backpressure that prevents the increased volume of air from flowing back outside the engine.

In an SC or turbo the spinning fan/lobes are this prevention, with a BOV there for the times there can be an overpressure.

With a nitrous system, the only pressure is enough to force the nitrous out against atmospheric pressure, the flow of air into the engine does the rest.

I didnt think about that... I figured that there is actually a vacuum in the intake from the valve inlet cycles, so the pressure gradient would keep the air from reverse flowing through the filter.

But yea... if the pressure was increased to >14.7 psia, then I can see how reverse flow would be a problem.

also, could you explain the nitrous part a little better? I am not familiar with nitrous at all. Are you saying that the pressure is not increased in a nitrous system? ... just the combustion chemistry?