#89404, "is no backpressure the best way to go for max power?"
im just wondering cause i have been runnin open header (no cat no muffler ) right off my turbo and out the side of my front bumper for a while now and the car is fast. i once did connect it to my exhaust ( 2.5" pipe with only aftermarket muffler) and it def lost power. so ive just always been runnin open header and i like it but is there any power to gain from adding some backpressure or is open header the best way to go.
91 civic hatch, homemade turbo+ LS motor = 12 sec street car.
#89406, "RE: is no backpressure the best way to go for max power?" In response to Reply # 1
ya thats what i figured but i didnt know if it was none at all or just a tiny bit or what. i have none at all. i dont have pics no but in my sig if u look close u can see the pipe sticking out the side of my front bumper. basically i just bought pipe bends and cut them to what i need and welded them to stick out my bumper . so my whole exhaust is only like 2 feet long. but its only about 2.5" pipe i used ,thats the biggest i can fit without hittin radiator.
91 civic hatch, homemade turbo+ LS motor = 12 sec street car.
#89417, "RE: is no backpressure the best way to go for max power?" In response to Reply # 2
Originally posted by 97grnRS ya thats what i figured but i didnt know if it was none at all or just a tiny bit or what. i have none at all. i dont have pics no but in my sig if u look close u can see the pipe sticking out the side of my front bumper. basically i just bought pipe bends and cut them to what i need and welded them to stick out my bumper . so my whole exhaust is only like 2 feet long. but its only about 2.5" pipe i used ,thats the biggest i can fit without hittin radiator.
Jeez I bet thats loud, at least it comes out the passenger side. As for backpressure I'm sure someone will tell you want some backpressure but the simple fact is the easier it is for your engine to breathe the more efficiantly it will operate. On a n/a car low or no backpressure will kill low end making it seem like you lost power but the power has moved to a higher rpm range thats all. There have been alot of discusions about this topic and the way I see it is if your n/a(which your not) you probably want some backpressure for drivablity reasons, but if your turbo then the less backpressure the better.
#89466, "RE: is no backpressure the best way to go for max power?" In response to Reply # 4
its actually not too loud until i go full throttle but it sure gets alot of looks at stop lights. ppl look down like what the hell is that? its funny. i do notice low end power sucks for normal driving but if i gun it it really goes. and ya a 14B bolted and welded to my stock manifold . eight lbs on rebuilt to stock spec motor. fast is all i can say. i ran a 14.3 with my old homemade setup which was a subaru ihi rhb5 turbo on my stock mani and no inter cooler at 8 psi. this setup is way faster and ive done more mods since then so i know ill easily break 13's next time i run it. . on shitty street 14" wheels.
91 civic hatch, homemade turbo+ LS motor = 12 sec street car.
#89473, "RE: is no backpressure the best way to go for max power?" In response to Reply # 3
Originally posted by Talontaxi
Originally posted by 97grnRS ya thats what i figured but i didnt know if it was none at all or just a tiny bit or what. i have none at all. i dont have pics no but in my sig if u look close u can see the pipe sticking out the side of my front bumper. basically i just bought pipe bends and cut them to what i need and welded them to stick out my bumper . so my whole exhaust is only like 2 feet long. but its only about 2.5" pipe i used ,thats the biggest i can fit without hittin radiator.
Jeez I bet thats loud, at least it comes out the passenger side. As for backpressure I'm sure someone will tell you want some backpressure but the simple fact is the easier it is for your engine to breathe the more efficiantly it will operate. On a n/a car low or no backpressure will kill low end making it seem like you lost power but the power has moved to a higher rpm range thats all. There have been alot of discusions about this topic and the way I see it is if your n/a(which your not) you probably want some backpressure for drivablity reasons, but if your turbo then the less backpressure the better.
I've got the open downpipe right now, mine is only 8" long haha... it is pretty loud. Sounds pretty mean too, I want to keep it like this, but sucking exhaust fumes all the time while I'm driving really sucks. It is probably not as loud as you would think, though... and once you get your foot into it, it absolutely ROARS. Plus the turbo is really really really loud, so you get to hear that wonderful whistling a lot.
#89475, "RE: is no backpressure the best way to go for max power?" In response to Reply # 8
Originally posted by BumpinTalon
Originally posted by Talontaxi
Originally posted by 97grnRS ya thats what i figured but i didnt know if it was none at all or just a tiny bit or what. i have none at all. i dont have pics no but in my sig if u look close u can see the pipe sticking out the side of my front bumper. basically i just bought pipe bends and cut them to what i need and welded them to stick out my bumper . so my whole exhaust is only like 2 feet long. but its only about 2.5" pipe i used ,thats the biggest i can fit without hittin radiator.
Jeez I bet thats loud, at least it comes out the passenger side. As for backpressure I'm sure someone will tell you want some backpressure but the simple fact is the easier it is for your engine to breathe the more efficiantly it will operate. On a n/a car low or no backpressure will kill low end making it seem like you lost power but the power has moved to a higher rpm range thats all. There have been alot of discusions about this topic and the way I see it is if your n/a(which your not) you probably want some backpressure for drivablity reasons, but if your turbo then the less backpressure the better.
I've got the open downpipe right now, mine is only 8" long haha... it is pretty loud. Sounds pretty mean too, I want to keep it like this, but sucking exhaust fumes all the time while I'm driving really sucks. It is probably not as loud as you would think, though... and once you get your foot into it, it absolutely ROARS. Plus the turbo is really really really loud, so you get to hear that wonderful whistling a lot.
Yup, I got my Mccord cutout at the end of my DP and it get's real loud at WOT. I have a stcok GST exhaust on. I miss gunning it all the time and feeling the boost, instead I have to open the valve then gun it. I dunno, I'll be moving to San Diego soon so we'll see if the sleeper look flys. BTW I love that whistle sound too, like at 1/4 throttle, you think folks outside can hear it?
#89494, "RE: is no backpressure the best way to go for max power?" In response to Reply # 10
Originally posted by Semperboost Yup, I got my Mccord cutout at the end of my DP and it get's real loud at WOT. I have a stcok GST exhaust on. I miss gunning it all the time and feeling the boost, instead I have to open the valve then gun it. I dunno, I'll be moving to San Diego soon so we'll see if the sleeper look flys. BTW I love that whistle sound too, like at 1/4 throttle, you think folks outside can hear it? Alvin http://www.cardomain.com/id/96rst
can folks outside hear it? hmm I dunno. My turbo doesn't really spool to around 3500rpm right so I doubt people can hear it at 1/4 throttle.. at about half throttle the turbo gets really apparent, and at full throttle at about 5000rpm its all you can hear.. and you can definitely hear it from outside the car, I got my buddy to do full throttle standing starts while I stood outside just to make sure
#89536, "RE: is no backpressure the best way to go for max power?" In response to Reply # 3 Sep-12-05 04:13 PM by ner947
Originally posted by Talontaxi As for backpressure I'm sure someone will tell you want some backpressure but the simple fact is the easier it is for your engine to breathe the more efficiantly it will operate. On a n/a car low or no backpressure will kill low end making it seem like you lost power but the power has moved to a higher rpm range thats all.
You're mixing up backpressure with velocity... Backpressure is bad. Always.
A given sized exhaust pipe will yield a peak velocity at a certain amount of airflow. Velocity yields torque, power is a function of torque and RPM therefore if you maximize your velocity you will make the most power. This is why a 3" exhaust on a normally aspirated 420A will make the car slow unless you have some crazy cams, nitrous, and some serious headwork. Even with all of that 3" is probably still too big. All of that extra width will reduce velocity. The flipside of the coin is that if you make the pipe too small, it will be restrictive and the backpressure will increase. Very small pipes work great on a Geo Metro 3 banger, because they don't flow much air to begin with so they don't need much width to peak the velocity.
A good size to stick with for a normally aspirated 420A application is around 2.25” – 2.5”.
For a turbo, it's a bit different. You will have the highest turbine efficiency if the pressure after the turbine is at it's lowest. That means almost NO exhaust is ideal in this case. Of course, it's not pratical to run an open downpipe because of cops, rednecks with pitchforks, little old ladies trying to cross the street with heart conditions, etc...
#89556, "RE: is no backpressure the best way to go for max power?" In response to Reply # 12
Originally posted by ner947
Originally posted by Talontaxi As for backpressure I'm sure someone will tell you want some backpressure but the simple fact is the easier it is for your engine to breathe the more efficiantly it will operate. On a n/a car low or no backpressure will kill low end making it seem like you lost power but the power has moved to a higher rpm range thats all.
You're mixing up backpressure with velocity... Backpressure is bad. Always. A given sized exhaust pipe will yield a peak velocity at a certain amount of airflow. Velocity yields torque, power is a function of torque and RPM therefore if you maximize your velocity you will make the most power. This is why a 3" exhaust on a normally aspirated 420A will make the car slow unless you have some crazy cams, nitrous, and some serious headwork. Even with all of that 3" is probably still too big. All of that extra width will reduce velocity. The flipside of the coin is that if you make the pipe too small, it will be restrictive and the backpressure will increase. Very small pipes work great on a Geo Metro 3 banger, because they don't flow much air to begin with so they don't need much width to peak the velocity. A good size to stick with for a normally aspirated 420A application is around 2.25” – 2.5”. For a turbo, it's a bit different. You will have the highest turbine efficiency if the pressure after the turbine is at it's lowest. That means almost NO exhaust is ideal in this case. Of course, it's not pratical to run an open downpipe because of cops, rednecks with pitchforks, little old ladies trying to cross the street with heart conditions, etc...
Backpressure is not bad all the time. Only on turbo cars I thought. N/A cars need backpressure for torque dont they?
#89557, "RE: is no backpressure the best way to go for max power?" In response to Reply # 13
Originally posted by BANME!TuNeR Backpressure is not bad all the time. Only on turbo cars I thought. N/A cars need backpressure for torque dont they? Brian
#89558, "RE: is no backpressure the best way to go for max power?" In response to Reply # 14
Originally posted by ner947
Originally posted by BANME!TuNeR Backpressure is not bad all the time. Only on turbo cars I thought. N/A cars need backpressure for torque dont they? Brian
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