Turbo versus Air-pump

Power or fuel efficiency?

These tend to be a bit contradictory, probably easier to add power.

Your compressor and air storage sounds fine except for the weight penalty of the storage tank. Maybe if you can do without the tank? It's just an electric turbo I s'pose, so it should work! Sounds like a fun project!

If you want better fuel efficiency, chop off & throw away all the excess weight, fit narrow profile high pressure tyres, take your right shoe off and drive carefully!

Is the vehicle one which is low fuel consumption in the first place?

There would be little point trying to make a lumbering 4x4 SUV more fuel efficient?! Except maybe converting it to LPG?

The LPG conversion is not more fuel efficient. (It can be, if you build the engine with high compression to take advantge of the high octain of the LPG).

think about it. a 3 liter engine at 4000 RPM aspirates 12,000 liters/minute at normal temperature and pressure. If you want to increase that to 18,000 liters/minute or 50% boost, you will need close to 8 pounds per square inch of boost pressure, from ~15 to 23 PSI. How many 12,000 liter tanks can you carry? Each one good for 1 minute.

Then the power for this comes from???

What they typically use is an exhaust turbibe abd a rootes style blower for the boost. You may also need to change then engine or it may break as in explode.

http://www.google.com/search?hl=en&q=%22roots+blower%22+%2Bboost&btnG=Search

or maybe a 2 litre tank at 1000 atm.... 1 minute of boost is alooong way! 1/4 mile takes between 15 to 25 seconds for a road car. at 15 seconds you would travel 4 miles when the boost ran out. you would probably be well over 100 MPh and probably closer to 200kph at that moment!

Given the gas was cooled after compression, and you solved all the induction problems the idea is indeed feasible. the expanding air would mean you could leave the compression higher as it would be a cold intake charge lowering your detonation risk.

Recharging could take place on overun as a form of regenerative braking.

If you want to increase that to 18,000 liters/minute or 50% boost, you will need close to 8 pounds per square inch of boost pressure, from ~15 to 23 PSI.

This presupposes that you can somehow blow this pressure into the intake manifold without it all leaking back out through the air filter; you'd need to have some sort of one-way valve letting a 1-atmosphere charge in, then closing off the inlet while you dumped in the 8 psi boost, and let that flow out of the manifold through the intake valve(s). This seems to require tight coordination between this added valve and the engine's timing. Conceivably, putting in a one-way valve at each runner where it exits the plenum could handle this, but I suspect the $1k - 2k budget will go bye-bye first. Otherwise, you could close off the air intake entirely, and dump the full 23 psi into the manifold until you've reached to speed you want, or until your storage tank is down to that pressure; open the extra valve and run at one atmosphere while you recharge the tank, and repeat.

You might be better off finding a used nitrous oxide kit, if you're after power. An engine swap might be a cheaper way to handle either power OR economy improvement, if your vehicle had a better alternative from the factory.

The problem of the pressure blowing back into the manifold was my main issue. I'm still not sure if I will do it, but it still sounds like something fun to try out. Either this or I'll look into adding a custom hood scoop ram air, though it probably won't happen. Just lookin for ways to keep the mind occupied late at night.

Appreciate the comments,

Matt

boosters fit in front of the air inlet and increase the charge pressure and dendity into the engine. Often the air filter is removed and a new larger area, low flow loss filter is fitted. The roots blowers need a filter in front of them as they are very tightly machined rotating lobe air blowers and cannot tolerate any grit.

http://en.wikipedia.org/wiki/Roots_blower

a 3 liter engine at 4000 RPM aspirates 12,000 liters/minute at normal temperature and pressure.

This would be true for a two-stroke, but all current auto engines that I know of are four-stroke, cutting the liters per minute in half. It takes two revolutions to pump the nominal displacement volume. This doesn't significantly change any of the analyses in this thread; it is only a comment. (I've always said that a degree in physics enables me to say that a factor of two is "close" with a straight face. For some kinds of estimates, that would be wonderful accuracy!). Mazda Wankels are a separate case, since the way that their displacement and number of cycles is calculated doesn't conform to the same rules as conventional piston engines.

That is correct. I realized this after the edit window had closed, but did not create a later post. In addtiion the action of the throttle also starves the engine, thus the manifold vacuum, leading to an even greater reduction in pumped volume.

Matt, study the physical application of a turbo charger and you will notice that you have the air supply from the turbo attached directly to the carburator air inlet. This is necessary for the fuel system to relate to the quantity of available air. Introducing the pressurized air directly into the manifold after the carburator will more than likely just let all the excess air escape backwards via the carburator. The same applies to fuel injected engines. In simplicity the turbo must trap the pressurized air between itself and the intake manifold. Hope this broadens your understanding of pressurizing air intake systems. Del Sol engineering. dw.

Exactly, the air/fuel ratio 14:1 has to be maintained. Too lean and it too hot to rich and no power.

I'm glad someone mentioned fuel / air ratio. Most of what I have seen so far matches my idea of wild speculation. The cost of a fuel system to keep up with all that incoming air. . . I just don't see any of these ideas being cheaper than a good ol' fashioned turbocharger. However, I suppose from ideas like these comes innovation.

My father had an idea of mounting a rocket in the tail pipe to evacuate the exhaust, creating a vacuum in the combustion chamber. I feel a little sad now that I told him it wouldn't work. Shame on me.

Build it, test it. Just leave the JATOs at home.

-A-

If you think 'Mixture delivery` instead of 'Air delivery` you will

have a clearer picture of the problems you would be facing.

It doesn't have to be very expensive to turbo charge an engine. Get a used turbo of appropriate size (or two for a v-8). Rebuild if necessary. Have it installed in the exhaust . run the pressure plumbing to a bonnet that blows through the carburetor or throttle body. If Carbureted, you will need a fuel pressure booster pump with a switch on the throttle linkage to turn it on at WOT.

This will not work on fuel injected vehicles with a MAP sensor (which meter fuel by measuring manifold vacuum and therefor cannot function under boost). Also, stock air mass meters will not function well under boost conditions as they are not calibrated to measure a ΔP greater than 1 ATM. Both applications will lead to immediately catastrophic engine failure as soon as boost is achieved. If you absolutely must have EFI, your looking at a stand alone ECM with some aftermarket (DC) injectors and fuel pump.

Best stick with the ol' 4-barrel carb with some big honkin' foggers as your secondary mains. Fuel pressure booster pump is a good idea, however you may need it to kick in well before WOT. More fuel is better than not enough (ka-boom!), even at the cost of running a little rich. It's time to read your blower chart and do some calculating.

Either way, your looking at having to spend time in a book. This, I find, is what prevents most people from doing things the right way. There is nothing new here. All the science and experimenting has been done. Take advantage of it.

-A-

Wouldn't this be a supercharger with a reservoir to allow extra boost at low rpm? It must have been done. I can't see it being a bad idea, but I could imagine serious issues with ignition timing and fuel injection timing (if fitted) as they would differ from standard settings required for a normally aspirated engine. As this is, as required boost, your engine management system would have to be able to accommodate the normal slow speed settings for idle and cruising and then be able to detect and change to the boosted settings. This is occurring at similar rev ranges. Lots of issues to hard and complex for me!!