Backpressure argument with brother
02-15-2009, 03:22 PM
#1
TECH Regular
Thread Starter
iTrader: (1)
Join Date: Mar 2006
Location: Cali
Posts: 485
Likes: 0
Received 0 Likes
on
0 Posts
Backpressure argument with brother Ok so me and my brother have been haveing a little dispute regarding backpressure. He insists that " a certain amount of backpressure is needed to create a vacuum to suck out exhaust, you need back pressure to a certain extent cus it effects the intake,the faster you remove exhaust gasses the faster the intake sucks air." On the other hand im saying that you need good flowing headers(Not hugeee ones) but no back pressure is needed ,the more exhaust out is better
what do you think?
what do you think?
02-15-2009, 03:48 PM
#3
I have heard alot of people preaching the backpressure sermon, but in aviation school in piston engine shop, the ideal exhaust system to have is one that pulls a vacuum in the cylinder which in turn would completely scavenge the cylinder of all the gasses and whatever else is in there..
02-15-2009, 03:59 PM
#4
TECH Regular
iTrader: (1)
Join Date: Aug 2008
Location: Colorado
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
Backpressure shifts the torque curve downwards and reduces peak HP. depending on what you're doing, this may or may not be desirable.
For instance, on my motorcycle, I want some back pressure so that low-RPM cruising doesn't suck, and since a peak HP build has a very very narrow powerband and I want mid-range power instead. On the car, you want a lot less - I'm looking for peak power more, since I have more to work with.
It all depends on what the goal is.
edit: and yes, it can be used to create a scavenging effect, I believe - I'm most familiar with it from the MC world where we don't have to worry about that, as my pipes are 1 per cylinder
For instance, on my motorcycle, I want some back pressure so that low-RPM cruising doesn't suck, and since a peak HP build has a very very narrow powerband and I want mid-range power instead. On the car, you want a lot less - I'm looking for peak power more, since I have more to work with.
It all depends on what the goal is.
edit: and yes, it can be used to create a scavenging effect, I believe - I'm most familiar with it from the MC world where we don't have to worry about that, as my pipes are 1 per cylinder
02-16-2009, 05:56 PM
#6
TECH Senior Member
iTrader: (96)
Join Date: Aug 2007
Location: Turnin' Wrenches Infractions: 005
Posts: 24,240
Likes: 0
Received 81 Likes
on
72 Posts
Backpressure shifts the torque curve downwards and reduces peak HP. depending on what you're doing, this may or may not be desirable.
For instance, on my motorcycle, I want some back pressure so that low-RPM cruising doesn't suck, and since a peak HP build has a very very narrow powerband and I want mid-range power instead. On the car, you want a lot less - I'm looking for peak power more, since I have more to work with.
It all depends on what the goal is.
edit: and yes, it can be used to create a scavenging effect, I believe - I'm most familiar with it from the MC world where we don't have to worry about that, as my pipes are 1 per cylinder
For instance, on my motorcycle, I want some back pressure so that low-RPM cruising doesn't suck, and since a peak HP build has a very very narrow powerband and I want mid-range power instead. On the car, you want a lot less - I'm looking for peak power more, since I have more to work with.
It all depends on what the goal is.
edit: and yes, it can be used to create a scavenging effect, I believe - I'm most familiar with it from the MC world where we don't have to worry about that, as my pipes are 1 per cylinder
