Negative Pressure Supercharging..Thoughts/comments?

[Norbie]

You don't need to be an engineer to figure that out. Even if you were able to acheive absolute vacuum with "negative supercharging", the maximum pressure differential you'll ever see is 1 atmosphere. (Of course you'll never get anywhere near absolute vacuum). Compare that to actual supercharging where you can theoretically crank it up to several atmospheres.

[VHDREAMS]

I agree, but that doesnt mean its a pointless exercise...

Cory

[Beavis]

Well AFAIK there used to be some two-stroke diesel truck engines that used superchargers to suck the gasses out rather than blow-through.
There's a bit to be gained from lowering the backpressure but suffice to say I'm not entirely confident about it producing 'violent acceleration' as such.

I think this is called "crankcase supercharging", in the two-stroke world?

[floody]

I think this is called "crankcase supercharging", in the two-stroke world?

All two stroke petrol motors pre-compress the mixture somewhat in the crankcase. Motorcycle engines use careful direction of sound waves, pressure etc to provide different effects as well, to keep gases in or suck out of the exhaust ports.
I'm not sure on 2 stroke diesels?

[GTSBoy]

It doesn't matrer what freaky low pressure you create in the exhaust manifold/collector. It still has to come out the tailpipe where the local pressure is exactly 1 atmosphere. If you decrease the local pressure in the exhaust to below that value in order to suck gases out of the engine, then you only have to pump the gases back up to atmospheric to get them out the tailpipe. Not a winning solution.

cheers

[Beavis]

All two stroke petrol motors pre-compress the mixture somewhat in the crankcase. Motorcycle engines use careful direction of sound waves, pressure etc to provide different effects as well, to keep gases in or suck out of the exhaust ports.
I'm not sure on 2 stroke diesels?

Sorry, I meant "I think this is called crankcase supercharging" when referring to two-stroke diesels.

Say, isn't it impossible to have a two-stroke diesel without having a blower? I remember reading something like that on www.howstuffworks.com

[BigMuz]

I agree, but that doesnt mean its a pointless exercise...

Cory

Pointless and unfathomable. The point is that cams have been designed around the concepts of air momentum since day 1 (possibly day 2 :D).

Cams and exhaust and inlets are designed to give an efficient working range with consideration to the intended use of the engine.

If you want to sacrifice a broad operating range then it is easy to make an engine breathe extremely well (over 100% VE) over a narrow range of rpm. That is all this clown is doing, compromising the usable rpm range of his engine to make peak torque early and over a small rev range. (Not that hard to do, ask mr Harley Davidson how :D)

His bizarro cam timings are irrelevant, I am betting good results can be had without resorting to artificially closing inlests early etc.

Muz

[Lobster]

So, someone go out there and go for a ride in his car...

[Nitephyre]

It's interesting to note that in 1876 the inventor of the 4-stroke engine was not the steam locomotive companies but instead Nicolaus August Otto a brilliant self-taught engineer. The situation is the same today. Its not car companies that have invented this revolutionary new supercharging process that makes the 4-stroke engine supercharge itself using NO air pump but again a brilliant self-taught engineer, Alexander Chabry.

Himself. On. Tickets. Has.