[Timmeh]

Sorry to post again but I can't let this go:

Originally Posted by Panda

Where to start, where to start....

[Font=Tahoma]Exhaust Cycle
The Negative Pressure Supercharging process begins with the exhaust cycle. As the exhaust valve opens the massive gas pressure produced after combustion it has already expended it's energy - driving down the pistonforces itself through a compact header with very small and short pipes. This causes the high pressure gas to compress in the small pipe increasing pressure, reducing flow = no net increase in gas flowand accelerate to a high velocity which is twice the speed produced by typical large pipe headersagain, increasing pressure and reducing flow = no net change in gas flow. As a result a negative pressure is produced behind the high velocity gas in the small pipe which is so strong it reduces the pressure in the cylinder during the exhaust stroke. it is the positive pressure in the cylinder which moves the gas, it does not move on it's own

There is nothing wrong with what is said here, although it is described interestingly. The burnt air initially gets pushed out of the cylinder by the piston rising after its power stroke. A set of extractors or well made exhaust manifold will have a low pressure scavenging wave arrive at the overlap from the other pistons that have previously fired, helping draw the air out.

The momentum of the air leaving the cylinder does create a low pressure in the cylinder of a normal engine, but this is where these two designs (the one in topic and a regular engine) differ. At this point in a normal engine, the inlet valve is open (yes, both the inlet and exhaust valves are open at this point, called overlap), and the escaping exhaust burnt mixture leaving creates a low pressure drawing thru the unburnt fuel air mixture of the next cycle. From what I understand with this setup, they are closing the exhaust valve before the inlet valve is opened to have the low pressure trapped inside.

The reason I think this setup is crap is that the inlet valve now has a shorter total time to be open, and may not get the full advantage of the exhaust gas drawing it in.

Originally Posted by Panda

However, the high pressure gas in the small pipe of the header will remain compressed for only a short distance before it builds up back pressure and restricts the gas flow. nopeTherefore, the small pipe of the header is very short and a megaphone pipe is used after the header to allow the compressed gas in the small pipe to gradually expand into the larger diameter of the megaphone pipe.this does actually work - the venturi effect This allows the exhaust gas to flow only away from the exhaust port at a very high velocity and with no back pressure to restrict the gas flow. this part however is crap

Here they are just talking about how to now best get rid of the exhaust gases that have left the engine. However, this part is not as important. Any exhaust gas flowing will leave a low pressure behind, its a basic fundamental of any extractors.

Originally Posted by Panda

Keep in mind that negative (low) pressure is naturally produced behind all moving objects which travel at a high speedcrap, gasses do not have a mass. The faster the speed of a moving object, the lower and stronger the negative pressure is behind the fast moving object. wrong for so many reasonsThe same principle applies to the gas flow in the primary pipe of a typical headerhorse-shit. The smaller the pipe, the faster the gas speed trueand therefore the lower and stronger the negative pressure is behind the gas flow in the header. false

Where you say wrong for so many reasons, I'd like to hear them. I work in aviation and it's what aerodynamics is all about. When a train passes thru a station, the faster it passes thru, the more disturbed the air behind it is, like when you see ads of the train blowing a girls hair as it passes. Just like the faster an aircrafts wing goes, the lower the pressure above it due to the rising airspeed is, and the wing gets sucked up (as well as creating high pressure below it and being pushed up). I don't think what is being said here is wrong, in my opinion. And I still stand that gasses DO have mass, its a basic fundamental on how an engine works, drawing air into the cylinder, as explained in my previous reply.

Originally Posted by Panda

Overlap Period
At the end of the exhaust cycle during the overlap period, the negative (low) pressure is trapped in the combustion chamber by closing the exhaust valve early before TDC and using low exhaust valve lift. so you close in the cylinder while the piston is still compressingSoon after the exhaust valve has closed, the intake valve opens early before TDC still compressingto allow the negative pressure trapped in the combustion chamber to pull the intake charge into the engine instead of into the exhaust system. crap

You seem to be very mixed up here. If the exhaust valve has just closed, you're not on the compression stroke. You're finishing the power stroke, remember that a piston travels twice for every one time it fires. It won't be compressing while either valves are open (in a normal engine, both will be open during an overlap period). Remember the sequence: exhaust (up) - intake (down) - compression (up) - power (down). Your reply there was thinking that this was happening on the compression stroke, but it is clearly describing the exhaust to intake part of the sequence. There is absolutley nothing wrong with the description here - only the theory behind the idea is not what I would use.

Originally Posted by Panda

Intake Cycle
The intake valve opens before TDC and after the exhaust valve has closed, to allow the negative pressure trapped in the combustion chamber to pull the intake charge into the engine and fill the cylinder very rapidly with a greater volume of air early in the intake cycle. still crapThe intake charge is also increased to a hot temperature atomised fuel is already above it's flash point. Increasing the termerature further will make it ignite, but why do you want this on the intake cycle?to produce more combustion pressure you can't produce compression on the intake cycleand burn faster. little bit true

Once again, you have confused the stroke the piston is currently in. No need to explain this again.

Originally Posted by Panda

As the piston moves down the cylinder during the intake stroke, it further reduces the pressure in the cylinder. This pulls an additional volume of hot air into the engine faster than the speed of sound. you're ****ing kidding me aren't youAt the end of the intake cycle the intake valve closes early after BDC same as normalto trap the much larger volume of hot air in the cylinder and prevent the air from being forced back into the intake manifold during the compression stroke. same as normal

I think you're underestimating the speed air flows into a cylinder. Well designed engines will pile air thru the intake port at over 800km/h. So, it's not far off what they quote, but I do agree that 'faster than the speed of sound' is a bit dramatic and exagerated. As you say, the rest is normal, so you've managed to catch up to the right stroke at some time in your thought process.

Originally Posted by Panda

Keep in mind that even though hot gas is less dense it explodes with a much greater force because it reaches its maximum pressure much faster than the more dense cold gas. because it is less dense the computer has to swing the Air / Fuel ratio - giving you less fuelTherefore, the engine is able to produce more power with a hotter intake charge because the increase in power produced by the higher combustion pressure and faster burn of hot gas is much greater than the loss produced by less dense hot air.

The speed at which the fuel burns is important, an uncontrolled burn with hot mixtures will cause detonation and a rapid destruction of the engine. Water injection kits are designed specifically to cool the air fuel mixture, so here is where I am pointing my finger at this idea and calling it crap, rather than trying to correct anomalies in the reply.

I hope that makes things a bit more clear for people, not trying to be a real bass, but there was alot of incorrect information there that needed to be explained.

My verdict: it's crap too.

Tim