Quote:
Originally Posted by pounsfos
hes talking about variable exhaust valve that sits in the exhaust pipe
(most are butterfly valves like your throttle body butterfly valve)
it closes the butterfly vavle at low cruizing loads to improve low end response (as you now have more back pressure so gasses escape easier compared to a bigger exhaust)
then it opens as load increases (like w.o.t)
all this is controlled either by your ecu or by engine vacuum
as for an increase in fuel economy well i wouldnt know but if you ask me you could invest your money in something abit more worthwhile, like a "economy grind camshaft" or a some intake mods and stripping emissions devices to increase fuel economy.
do a google search and some reading on it and report back as you have me interested on if this might do something or not (if it does then i'm moving upto a bigger exhaust hahahaha
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Well that's what I have now, but I am going to redo the whole thing with one high flow muffler and 2" piping ( good for 150ish hp flow wise) and butterfly valve that's going to open at 5k rpm controlled by ecu, and the other one with a stock muffler and 1" piping that should be good for up to 40ish hp ( perfect for light throttle cruising). Basically the exhaust is going to have to go through stocking muffler and 1" pipe 0-5k rpm ( velocity should be at it's max around 4.5k) and after that 5k-13k the exhaust is going to be routed to go through both pipes and both mufflers all together should be able to support 200hp or so which is about what I need. I could have done 3 stage set up when it starts with 1" pipe, then goes through 2" pipe and then both pipes, but I'll see how this works out and if it does good 10% or so I might step up to a 3 stage set up and go little further in the head, plus intake variable length that is little more complicated, but is doable. The name of this game is velocity, try to keep it as high as possible without backpressure, because we all know, backpressure is not good.