[matty87]

suzi blu you are dead right what i was trying to get at is that in the real world nothing is perfect, meaning that pipes have wall friction and cause shearing in fluids and thus pressure drop etc.

However in the name of making modeling systems such as engines and exhausts and water pipes etc posible simplifications are often made one of these being simplifiying fluid interactions between pipe walls and the fluid itself, often including at times making pipe wall friction negligable.

it is a masive topic but in the end it boils down to trial and error and lots of testing is the way to do it.

[SuziBlu]

Yes, exactly.

You say there is pressure, but, in a simplified world, there is no such thing as pressure, just resistance to flow. A 3,000 PSI hydrolic hose will pump out, at very low flow, if it is unrestricted, but, take that same 1" line, and restrict it to 1/32" and it will cut your finger off with ease.

How can we restrict an exhaust pipe, so that there is good "flow" and so, there is a scavenging effect, meaning, a well set up system has negative pressure and so cleans and replaces the gasses within the combustion chamber, when there is back pressure.

From my knowledge, back pressure was needed eons ago, when metallurgy was nothing like it is today, and so, valves would burn out.

This is why I do not like turbos, they need to restrict the exhaust upstream of the blower, so as to produce a very fast flowing stream of "air" to spin the turbine, where as a mechanically driven compressor, has the beauty of a well designed free flowing scavenging exhaust. Best of both worlds.

When I did marine engineering, the basics was called, "suck, squeeze, bang, blow" (4 stroke) a hair dryer, is very restrictive, a mechanical blower has no such restriction, and so produces vast amount of bottom end grunt. Which is what all 4wders want.

The full scientific study of exhausts is beyond me, but, I am not trying to do a scientific analysis of it, there are the experts out there that have done this, and can produce a vast amount more power for you than a stock, cheap, exhaust.

[matty87]

hahaha i like it suck, squeeze, bang, blow. iv heard that before my old man uses it when describing 4 strokes to year 10s just like sex and that would get some attention. i do think the moral to this story is the guy at the exahust shop often does know what is going on but may not be able to provide you with the best setup. that is why systems built by some of the big american companies like magnaflow are worth the money if you want the best results.

[MacDaddy]

I was out driving to day, and i noticed something...

Since i had the extractors and the 2inch system fitted, my engine has continued to run better and better over time, must be getting rid of alot of carbon and crap in the cylinder heads, and isnt recycling burnt exhaust gases anymore...

But the thing i really noticed today, was that even though here has been an increase in engine performance and power across all RPM, both low, Med and high, when the engine gets to 3000rpm there is a slight surge of power, and when the engine hits 4000rpm, there is a very noticeable increase in power, if i put my foot to the floor the engine just winds out, and i can very quickly hit 120kph before i know it

I had a Sports system fitted, and i can now see it is designed to give maximum performance at higher RPM's, which is great for a Zook engine, they just love high RPM's

Not bad for engine thats done nearly 230,000 km's...

Anybody else notice anything like this ?