back pressure?

[Groundhawger]

ive got a 98 z71 with a rebuilt 350. im running dual exhaust out the rear. still has both converters on it but doesnt have any mufflers. am i loosing power because i dont really have any back pressure cuz i dont have muffler?

[marshall]

no

[Jjay78]

no your cats provide more than enough back pressure

[Disturban]

An Engine Needing Back Pressure is a bunch of BS!!!   Any body who tells you that bs has no idea what they are talking about. Think of an engine as an air pump (a little more complicated than that but) What goes in must come out. To big of a pipe will cool and slow the exhaust gas pulses diminising the scavageing effect. To small will cause back pressure making the engine work to force the exhaust gasses out. Both will cause a loss in power. Back pressure is bad! You have back pressure even though you have no mufflers. You are fine. You more than likely won't be able to feel the differance between a properly set up exhaust and yours on a stock 350, even thought you may think you can. Your fine, no worries. 

X2 could not have said it better...I would put in a X pipe or H pipe to help with scavenging though.

[85cHeavyMetalBogger]

what about people runnun uprights or open exhaust

[chevyjake]

An Engine Needing Back Pressure is a bunch of BS!!!   Any body who tells you that bs has no idea what they are talking about. Think of an engine as an air pump (a little more complicated than that but) What goes in must come out. To big of a pipe will cool and slow the exhaust gas pulses diminising the scavageing effect. To small will cause back pressure making the engine work to force the exhaust gasses out. Both will cause a loss in power. Back pressure is bad! You have back pressure even though you have no mufflers. You are fine. You more than likely won't be able to feel the differance between a properly set up exhaust and yours on a stock 350, even thought you may think you can. Your fine, no worries. 

X2 could not have said it better...I would put in a X pipe or H pipe to help with scavenging though.

max back pressure should only be a few pounds.  basiclly you just want a good flow, like intakes, more power with better flow.

[old school truck dude]

If it was a carb motor with no computer Id say the less back pressure the better, however these computer controlled motors needs the amount of back pressure that they came from the factory with unless youre going to modify the computer to reflect the difference, it runs richer with less back pressure and the computer compensates by leaning out the mixture, and presto!! You have pretty much the same or slightly less performance and very bad gas mileage (youll be pushin the gas pedal down just a little further to do things) but it sure sounds good Power comes in a package, you cant change one thing without affecting others and when theres a computer involved, you have to be able to predict how it will react to changes in the system. The key word here is system.  If it were me and I had the $$ I would get a proven exhaust system from a reputable dealer

[old school truck dude]

EFI engines are not equipped with PSI sensors. 

Thats right, but they are equipped with o2 sensors and thats where the problem begins. With little or no back pressure more raw fuel makes it into the exhaust system and it gives a rich signal to the computer. The computer compensates by leaning out the mixture. Youre actually running rich but the computer makes it lean. You end up with a lean code among other things.

[Groundhawger]

so if i put mufflers on it i should get alittle better gas mileage?

[J.C.]

so if i put mufflers on it i should get alittle better gas mileage?

prolly good for a few mpgs, 1-5 maybe

[old school truck dude]

so if i put mufflers on it i should get alittle better gas mileage?

so if i put mufflers on it i should get alittle better gas mileage?

prolly good for a few mpgs, 1-5 maybe

x2

[RIP_K52007]

Nope its the scavaging that will effect your power output... as long as you have a good set of headers or the factory manifolds that are designed to scavange correctly you should be fine..


I also have a topic going on about back pressure.

http://wegotmud.com/forum/index.php?topic=69517.0

[old school truck dude]

Scavenging is one of three things that figure into it, the other two are back pressure and gas velocity. Theres alot of research and developement by engineers that goes into all this