new exhaust system
#11
05-18-2011, 04:06 PM
then he needs to study exhaust theory..
the basic concept is generating enough heat to create a vacuum like effect from the heads to the tips- the engine is only strong enough to push it so far- it needs help from heat to create that vacuum, and help from the other bank to generate a tug when the opposite one slows.. It is referred to as scavenging, but many confuse the term with back-pressure.. back pressure is bad.. scavenging is good..
on the flip side, if it is too open, the air cools too fast and creates a barrier for the pulse behind it.. back pressure..
if it is too restrictive, it can't get out of the way of itself fast enough.. back pressure..
just the right size will heat enough to create that conveyor I mentioned, and NOT create back pressure..
you're leaving cats in it- that actually will help you because cats get dang hot.. dang hot when the exhaust is attempting to cool, which gives you a tug about the same time the engines pushing has exhausted itself..
you're on the right track, and he is right but not for the right reason- smaller pipes generate more heat.. wrapped pipes not only keep the engine bay cooler (which is a side effect of wrapping them) they also insulate and keep the pipes hotter (which is good).. ceramic is the preferred wrap, but exhaust tape is often used as well.
the basic concept is generating enough heat to create a vacuum like effect from the heads to the tips- the engine is only strong enough to push it so far- it needs help from heat to create that vacuum, and help from the other bank to generate a tug when the opposite one slows.. It is referred to as scavenging, but many confuse the term with back-pressure.. back pressure is bad.. scavenging is good..
on the flip side, if it is too open, the air cools too fast and creates a barrier for the pulse behind it.. back pressure..
if it is too restrictive, it can't get out of the way of itself fast enough.. back pressure..
just the right size will heat enough to create that conveyor I mentioned, and NOT create back pressure..
you're leaving cats in it- that actually will help you because cats get dang hot.. dang hot when the exhaust is attempting to cool, which gives you a tug about the same time the engines pushing has exhausted itself..
you're on the right track, and he is right but not for the right reason- smaller pipes generate more heat.. wrapped pipes not only keep the engine bay cooler (which is a side effect of wrapping them) they also insulate and keep the pipes hotter (which is good).. ceramic is the preferred wrap, but exhaust tape is often used as well.
What about size for no cats?
sorry to keep asking questions
#12
05-18-2011, 04:11 PM
Champion
I don't have the knowledge to do the math, but it is generally agreed that 2.25 to 2.5" pipes on a dual exhaust system is optimum.. 3" on a Y piped system is fine.. 3" on duals is too much.. those cats you're getting are high flows, they will get hot like any other cat, and help with scavenging but not restrict like a OE cat will.. The difference in having them and not having them is slight.. I'd rec you have them for legal purposes, but also to create another hot spot to draft the pulses out better.. It's up to you..
the biggest thing you'll need, though, is good mandrel bends and good welds.. try to keep the pipes as close to the same length as the opposite banks, and generate as little back pressure as possible...
the biggest thing you'll need, though, is good mandrel bends and good welds.. try to keep the pipes as close to the same length as the opposite banks, and generate as little back pressure as possible...
#14
05-20-2011, 02:02 PM
#15
05-20-2011, 02:32 PM
Champion
the paint thats on them is on them for one reason: so they don't rust while they wait for someone to buy them.. it isn't even temperature rated.. it will burn off in the first week you have them on, and you'll be able to see and smell it..
to do it right, you can sandblast them and do the oven thing, but if you have a wife or girlfriend that lives with you they likely won't forgive you. if you wrap them with tape it will serve the same purpose, but promote premature rust due to trapping moisture.. if you paint them w/ temperature rated paint you will thwart rust in the near future..
Or, you can bolt them on as is, and just ride it out.. up to you.. personally, I'd blast and paint them and walk away.. or blast paint and wrap them..
to do it right, you can sandblast them and do the oven thing, but if you have a wife or girlfriend that lives with you they likely won't forgive you. if you wrap them with tape it will serve the same purpose, but promote premature rust due to trapping moisture.. if you paint them w/ temperature rated paint you will thwart rust in the near future..
Or, you can bolt them on as is, and just ride it out.. up to you.. personally, I'd blast and paint them and walk away.. or blast paint and wrap them..
#16
05-20-2011, 02:37 PM
Champion
#17
05-20-2011, 03:28 PM
Grand Champion
#19
05-20-2011, 08:26 PM
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#20
05-20-2011, 08:53 PM