rileyrs
Well-Known Member
- Joined
- January 22, 2009
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- Year, Model & Trim Level
- 2002 ranger
i just posted this in my exhaust thread, about finishing my system, and was explaining my backpressure info, then i did a search, and realized that tons of people are actually confused with this topic, so i though id post this to try to clear up some stuff about backpressure.
my exhaust thread:
http://www.explorerforum.com/forums/showthread.php?t=256037
first some basic exhaust theory:
http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm
http://www.thumpertalk.com/forum/showthread.php?t=659727
also if any of you read petersens 4wheel and off road magazine, in the october 2005 issue there was some great info about intake and exhaust, and it explains backpressure clearly.
the thumpertalk one, focuses on backpressure only, but explains it well.
Here Goes.
no car ever needs backpressure, not even the sohc, despite what people say.
backpressure is always bad.
what is good, is a condition that creates backpressure which is the higher pressure within the exhaust, than the atmospheric pressure. also know as the exhaust pulses, which pull the gas out, but this simultaniously creates back pressure, so many people confuse these.
also gas velocity is needed, and smaller pipes yield higher velocity, often people use too large of diameter pipes, and their gas velocity is now so slow, that is also kills the exhaust pulses, and they loose power, and it leads them to falsely believe that they need backpressure.
but if your system is done well these pulses will work together to pull themselves out, so the engine doesnt have to, which keeps gases flowing quickly. headers will help do this, since they work with the exhaust pulses from each cylinder, rather than muffle them, and kill their velocity like stock manifolds.
i know this is a commonly confused issue, but its just not true that a free flowing system is bad.
many people just think the sohc needs backpressure because they put a flowmaster, and 3 inch piping, in their stock system and it loses power, but thats simply because they didnt do the rest of the exhaust, or enough reading, and the cats are destroying that exhaust pulse, and making the engine work to expell the gases from the combustion chamber.
but if the whole system is done right, then there is no back pressure, but good solid pulses... and in turn More Power!!!
anyway, hopefully that explains backpressure a bit, its kinda hard to explain, but ive read tons of stuff on exhaust theory, and this is the best way i can explain it, since its kinda hard to put in writing.
if anyone has anything to add that i missed, please do so, im just starting this thread to try to help people with their backpressure confusion, and in general to build their exhaust systems, correctly.
my exhaust thread:
http://www.explorerforum.com/forums/showthread.php?t=256037
first some basic exhaust theory:
http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm
http://www.thumpertalk.com/forum/showthread.php?t=659727
also if any of you read petersens 4wheel and off road magazine, in the october 2005 issue there was some great info about intake and exhaust, and it explains backpressure clearly.
the thumpertalk one, focuses on backpressure only, but explains it well.
Here Goes.
no car ever needs backpressure, not even the sohc, despite what people say.
backpressure is always bad.
what is good, is a condition that creates backpressure which is the higher pressure within the exhaust, than the atmospheric pressure. also know as the exhaust pulses, which pull the gas out, but this simultaniously creates back pressure, so many people confuse these.
also gas velocity is needed, and smaller pipes yield higher velocity, often people use too large of diameter pipes, and their gas velocity is now so slow, that is also kills the exhaust pulses, and they loose power, and it leads them to falsely believe that they need backpressure.
but if your system is done well these pulses will work together to pull themselves out, so the engine doesnt have to, which keeps gases flowing quickly. headers will help do this, since they work with the exhaust pulses from each cylinder, rather than muffle them, and kill their velocity like stock manifolds.
i know this is a commonly confused issue, but its just not true that a free flowing system is bad.
many people just think the sohc needs backpressure because they put a flowmaster, and 3 inch piping, in their stock system and it loses power, but thats simply because they didnt do the rest of the exhaust, or enough reading, and the cats are destroying that exhaust pulse, and making the engine work to expell the gases from the combustion chamber.
but if the whole system is done right, then there is no back pressure, but good solid pulses... and in turn More Power!!!
anyway, hopefully that explains backpressure a bit, its kinda hard to explain, but ive read tons of stuff on exhaust theory, and this is the best way i can explain it, since its kinda hard to put in writing.
if anyone has anything to add that i missed, please do so, im just starting this thread to try to help people with their backpressure confusion, and in general to build their exhaust systems, correctly.