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Let's 86 the intake valves

Replace them with air injectors .... of course!
  (+3, -2)
(+3, -2)
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Lets redesign this thing already. Remove those intake valves and replace them with high pressure air injectors.

For example, a 6 liter Chevy LS2 engine running at 7000 rpm requires around 92.70100 SCFM per injector. For a single stroke the injector has about .00857142857 seconds to deliver the required .026486 cubic feet of air. That’s a flow rate of about 1.54501667 standard cubic feet per second. OK, obviously sequential fuel injectors have no problem with delivering the fuel, but can they deliver the air?

A fuel injector for this particular engine can pass 1.17638889 scfs of fuel at 48 psi (8.8 gallons of fuel per second). So, if we raised the air pressure to approximately 63.0410578 psi it could deliver somewhere around the required 1.54501667 scfs. All we need to do is design an injector that would be optimized for passing gas (not fuel). After all, there’s no need to atomize all that air.

We'd need a redesign of the head to remove the intake valve completely. In it's place you install the fuel and air injectors directly into the cylinder dome. Get rid of that intake manifold, no reason to have that anymore. Who needs those extra cam lobes spinning around too?

While you’re at it we should make the exhaust valves discharge out the center of the engine to run a nice big centrally located turbo to pump up the air. Put it where the intake manifold used to be. Heck, I think we can reach the spark plugs now. Pipe the turbo to some nice polished stainless air runners to match the nice polished stainless fuel runners conveniently located on the outboard side of the engine.

You don’t need any valve overlap here. You simply have the engine control unit pop open the air injector to clean out any remaining exhaust gasses in the cylinder.

It would be awful nice to be able to dial in whatever cylinder pressure we wanted. Just let the air injectors stay open longer when we want a little extra oomph. After all, it is turbo charged.

jdog9, Aug 14 2006

Advanced Actuators Research Group http://www.me.sc.edu/Research/aarg/
AARG! Camless engines! [wiml, Aug 15 2006]


       Well, all it would take would be one ESD incident to the computer to turn the whole thing into an inanimate object, but we're pretty much going that direction anyway. I'll give you a preliminary pastry.
normzone, Aug 14 2006

       Yes, this would work, and I think it's been done, at least at an expiramental level. You would just need a LOT of very high pressure air. I'm not sure that a conventional turbocharger would work, since most turbos provide only about 16 psi at peak rpm. Even if you did have a turbo or supercharger big enough, it wouldn't supply enough pressure at low rpm, so you would need a reservoir to hold air.
discontinuuity, Aug 15 2006

       I barely understand this. Would the whine from the air compressor outdo the engine in noise?   

       Is it possible to have such a compressor, belt driven?   

       Would this be too hot? Where's [Rayford Steele]?
Zimmy, Aug 15 2006

       I think this would be a very inefficient engine that robs a lot of power.   

       Can "A fuel injector for this particular engine" really pass "8.8 gallons of fuel per second"?
BJS, Aug 15 2006

       Any frictional loss in the air intake will reduce efficiency. Any energy to pre-pressurize air is going to have to come from somewhere.
supercat, Aug 15 2006

       I may get smashed just for asking this, but wouldn't the air flow easier than fuel? So it seems that it would need less than the 63 psi given here.   

       Other than that, this seems to be (possibly) a good idea, but would likely be used only in pure race engines that can afford to cost a few million dollars to build. Two phrases here earned you a bun, though. Using the word "approximately" before a number that goes to the 7th decimal, and mentioning an injector optimized for "passing gas."
Hunter79764, Aug 15 2006

       [Hunter79764], of course air flows easier than fuel (by "fuel" I am assuming that you mean liquid fuel), but it doesn't flow through a high pressure injector easier than a practically non-restrictive intake valve system.   

       The numbers provided are only approximates because all engines and circumstances are at least slightly different.
BJS, Aug 15 2006

       I like this idea ... but thinking about it, how is it different from an individually-actuated intake valve? In both cases, you just have a valve that connects the cylinder to a reservoir of higher-pressure air, and the computer opens the valve at the appropriate time.   

       By "individually actuated" I mean those valves that are controlled by solenoids or something, instead of by the traditional camshaft design.   

       Hmmm, googling suggests that such solenoid-operated valves are still pretty much an experimental engine feature.
wiml, Aug 15 2006

       Isn't an intake valve nothing but an injector for air?   

       A fuel injector has two jobs. One is to atomize the fuel. Not needed for air. The second is to only allow fuel into the cylinder at the correct time, in other words it is a valve.   

       The intake valves just serve to allow air to pass from a high pressure side to a low pressure side at the appropriate moment. (And yes, even a normally aspirated engine has both. The intake manifold is at ambient air pressure, say 14 PSI. The cylinder is at Ambient * compression ratio. If the compression ratio is 1/7 then the pressure inside the cylinder is 2 PSI. )   

       I see no invention here. Get your knuckles dirty for a while before speculating about engines.
Galbinus_Caeli, Aug 16 2006

       How about using a RAM type air scoop to create the needed pressure? It would only work at higher speeds though.
Aq_Bi, Aug 16 2006

       Do you mean that the tiny little hole in a fuel injector passes 1+ scfs @ 48psi? That is a lot of flow. Maybe if we made the air injector bigger it could pass the needed volume with less pressure. Also, you wouldn't need quite 63psig to the injector, because there will be less than atmospheric pressure in the cylinder. You will only need differential pressure between air manifold and cylinder to equal 63psi.   

       Is it possible that releasing 63 psi air from a tiny hole in an injector would cool the air to the point that it may make a performance gain? What to do with the heat produced by compressing the air to begin with? I know, a Stirling air compressor!
wittyhoosier, Aug 16 2006


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