EcoModder.com

EcoModder.com (https://ecomodder.com/forum/)
-   EcoModding Central (https://ecomodder.com/forum/ecomodding-central.html)
-   -   Back pressure (https://ecomodder.com/forum/showthread.php/back-pressure-24910.html)

kanoshee 02-11-2013 04:04 AM

Back pressure
 
is it necessary? i have a 98 2.2 camry the codes i'm reading suggest my catalytic converter is bad so i'm wondering if cutting it out would be good for my fuel efficiency i have NO care about performance or speed in this car just comfort and fuel efficiency i have the capability to gut it out but does my engine need backpressure? should i get a "high flow" cat,no cat, gutted cat, new exhaust piping all together? i was thinking of replacing my muffler because the current one is HEAVY i think i'm gonna put the one off my old wrecked 89 camry on. also before i bought it it ran on 1-3 cylinders so there is ALOT of soot in my exhaust is it worth trying to get out? and what if i took my current exhaust manifold off and polished it? stacy david of gears suggested it lol
also the bend for my o2 sensor gets really small should that be dealt with or not? my exhaust has been welded on and patch so many times it changes from stock pipe to slightly bigger pipe 4 times it has one convertor one resonator and one muffler i'll post pictures tommorow.

serialk11r 02-11-2013 04:19 AM

No, backpressure is not necessary and it doesn't help. If you cut all that out of your exhaust though your car will be insanely loud and will piss everyone off.

kanoshee 02-11-2013 04:30 AM

Quote:

Originally Posted by serialk11r (Post 355926)
No, backpressure is not necessary and it doesn't help. If you cut all that out of your exhaust though your car will be insanely loud and will piss everyone off.

what about just the cat and keep the muffler and all? i hate loud cars with an extreme passion.... to be honest i hate them entirely too much

Tesla 02-11-2013 04:41 AM

Ignoring what the codes tell you for a minute, does the vehicle run poorly and is your fuel economy bad or gotten worse recently?

Your cat may be bad and gutting it may be fine, but it may not be your problem, be careful of jumping at shadows, look deeper to diagnose the real problem, it may actually just be a sensor problem.

Have you gone to vehicle specific discussion groups to see if yours is a common problem and how others have resolved it, everyone here has different vehicles so the info is more general and not vehicle specific.

razor02097 02-11-2013 07:41 AM

Back pressure is a commonly misused term when people speak of exhaust systems.... Velocity and flow are the important things in an exhaust.

The purpose of an exhaust system is to simply provide a way of exit for exhaust gasses. In order to get the maximum performance you want an exhaust system free of as many restrictions as possible. Obviously having a larger pipe diameter can increase flow capability...However you can go too far! An engine can only put out so much air. If the pipe is too large you loose velocity of the exhaust gasses. When that happens the exhaust cools and condenses. The engine literally has to push the exhaust out of the pipe. This pushing creates a differential which people refer to as "Back pressure".

Ideally you want a smooth pipe of the proper size that flows the perfect amount of air at the engine's most efficient operating RPM. This keeps the velocity of the exhaust gasses high which helps efficiency.

But wait... there's more! Just putting a pipe on there is going to make 5-0 unhappy... so you have to account for a muffler which controls noise and a resonator which controls drone. Placement of the muffler and resonator is very important. If you are in the USA you will also need a catalytic converter to make the EPA happy...

markweatherill 02-11-2013 07:47 AM

Quote:

Originally Posted by kanoshee (Post 355924)
does my engine need backpressure?

The valve timing will be set up with a certain amount of back pressure in mind ie with a stock exhaust.

Removing all the mufflers and silencers with the intent of reducing back pressure might negatively affect low speed running and driveability - and fuel economy.

Replacing the catalytic converter with a straight pipe shouldn't make much difference.

MTXA 02-11-2013 08:21 AM

It's a pretty simple to check for exhaust restriction. Remove an upstream O2 sensor and screw a 5/8" spark plug adapter from a compression tester into the bung. Connect a vacuum gauge that also reads positive pressure to the adapter. Fire up the engine and observe the gauge. Less than 4" of positive pressure = a serviceable exhaust.

If it ain't broke, why fix it?

royanddoreen 02-11-2013 08:49 AM

race cars a loud but they use wide open throttle most of the time

Ryland 02-11-2013 09:33 AM

Cutting out the catalytic converter will not make the dash light go out and like MTXA said, you can measure your back pressure, but the larger chunks of exhaust pipe you have could be the root of your problem, causing the exhaust to slow in the pipe and screwing with the function of the catalytic converter and o2 sensor.
Try fixing the exhaust piping first with something as close to stock as you can, reset the check engine light and see if it keeps coming back as being an issue.

slownugly 02-11-2013 10:36 AM

If you gut it, it will throw a 420 cat code. Fix it right. Back pressure on this vehicle is not as critical. Gutting it you wont notice much difference in sound or performance. Make no mistake, on performance applications back pressure IS very important. Rather than running open headers some drag racers switch out tuned extended header collectors to change torque curve and make more power at different rpm ranges. On street cars it's easy to install a larger exhaust than you need and you can actually decrease horsepower.

samwichse 02-11-2013 11:32 AM

Please don't just gut your cat, it will let a lot more NOx emissions out your tailpipe.

Take your converter off, soak it in a mild citric acid solution for 6-8 hours, then flush it with water at moderate pressure (not from a pressure washer, basically), remount, and if it was plugged with soot, it's good as new.

Sam

RobertISaar 02-11-2013 03:54 PM

pressure = restriction to flow. exhaust backpressure is no different.

restrictions in the exhaust = the piston has more force pushing against it while coming up during the exhaust cycle.

"needing backpressure" is an old wive's tale that still has yet to leave. commonly associated with "no backpressure will cause burned exhaust valves", among others.

BackroadBomber 02-11-2013 04:00 PM

If you gut the cat make sure you get the "spark plug non foulers" or whatever they're called... Basically they're 3 inch long tubes that are threaded and they move your o2 sensor farther from the pipe. And since an o2 sensor works on heat, it will trick your car into thinking that the cat is still working. That way your cel stays off and you can still pass inspection.

Ryland 02-11-2013 04:05 PM

You are never going to see 0 pressure in the exhaust, pretty much the lowest you can get it is 3psi, back pressure is a lousy wording because it does not describe what is really happening, it's pulses, just like a musical note from a trumpet is sound pulses, toss some weird sized chunk of pipe in there and it makes it go out of tune.
An exhaust pipe is part of the engine, if it was just a duct for exhaust then it wouldn't matter, but if you pull the exhaust manifold off the head of an engine it will hardly run, but at that point it will have -0- back pressure, exhaust is a gas, gases fallow rules of fluid dynamics, it has weight and momentum and it moves in pulses.

Fix the rest of your broken system before replacing or destroying an expensive part like a catalytic converter, the cat might not even be broken or clogged if this is a new problem.

kanoshee 02-11-2013 04:51 PM

Quote:

Originally Posted by Tesla (Post 355929)
Ignoring what the codes tell you for a minute, does the vehicle run poorly and is your fuel economy bad or gotten worse recently?

Your cat may be bad and gutting it may be fine, but it may not be your problem, be careful of jumping at shadows, look deeper to diagnose the real problem, it may actually just be a sensor problem.

Have you gone to vehicle specific discussion groups to see if yours is a common problem and how others have resolved it, everyone here has different vehicles so the info is more general and not vehicle specific.

i've already replaced my o2 sensor it was also bad and the car is weak but my effeciency is ok

kanoshee 02-11-2013 04:52 PM

Quote:

Originally Posted by samwichse (Post 355968)
Please don't just gut your cat, it will let a lot more NOx emissions out your tailpipe.

Take your converter off, soak it in a mild citric acid solution for 6-8 hours, then flush it with water at moderate pressure (not from a pressure washer, basically), remount, and if it was plugged with soot, it's good as new.

Sam

um... who gives a **** about that?

kanoshee 02-11-2013 04:53 PM

Quote:

Originally Posted by BackroadBomber (Post 356002)
If you gut the cat make sure you get the "spark plug non foulers" or whatever they're called... Basically they're 3 inch long tubes that are threaded and they move your o2 sensor farther from the pipe. And since an o2 sensor works on heat, it will trick your car into thinking that the cat is still working. That way your cel stays off and you can still pass inspection.

non emmisions county

kanoshee 02-11-2013 04:54 PM

Quote:

Originally Posted by Ryland (Post 356004)
You are never going to see 0 pressure in the exhaust, pretty much the lowest you can get it is 3psi, back pressure is a lousy wording because it does not describe what is really happening, it's pulses, just like a musical note from a trumpet is sound pulses, toss some weird sized chunk of pipe in there and it makes it go out of tune.
An exhaust pipe is part of the engine, if it was just a duct for exhaust then it wouldn't matter, but if you pull the exhaust manifold off the head of an engine it will hardly run, but at that point it will have -0- back pressure, exhaust is a gas, gases fallow rules of fluid dynamics, it has weight and momentum and it moves in pulses.

Fix the rest of your broken system before replacing or destroying an expensive part like a catalytic converter, the cat might not even be broken or clogged if this is a new problem.

nothing else on my system is broken?

oil pan 4 02-11-2013 06:01 PM

Quote:

Originally Posted by BackroadBomber (Post 356002)
If you gut the cat make sure you get the "spark plug non foulers" or whatever they're called... Basically they're 3 inch long tubes that are threaded and they move your o2 sensor farther from the pipe. And since an o2 sensor works on heat, it will trick your car into thinking that the cat is still working. That way your cel stays off and you can still pass inspection.

Taking the oxygen sensor out of the exhaust stream does make it read leaner.

Ryland 02-11-2013 06:14 PM

Quote:

Originally Posted by kanoshee (Post 356012)
nothing else on my system is broken?

Quote:

my exhaust has been welded on and patch so many times it changes from stock pipe to slightly bigger pipe 4 times it has one convertor one resonator and one muffler
Cobbled together exhaust systems put more stress on the o2 sensors and more stress on the catalytic converter because it messes with the exhaust flow, there are plenty of cars out there with 300,000 miles on them that have the original catalytic converter.
If your check engine light is on with a cat code, removing it isn't going to change anything unless you replace it with a working part, replacing it with a working part is only going to last if it's not under abnormal stress.

some_other_dave 02-11-2013 08:15 PM

Quote:

Originally Posted by kanoshee (Post 356009)
um... who gives a **** about that?

People who breathe do. For instance, ask anyone who lived in L.A. 30 years ago. You wouldn't want your area to turn into something like that, would you?

-soD

kanoshee 02-11-2013 10:47 PM

Quote:

Originally Posted by Ryland (Post 356024)
Cobbled together exhaust systems put more stress on the o2 sensors and more stress on the catalytic converter because it messes with the exhaust flow, there are plenty of cars out there with 300,000 miles on them that have the original catalytic converter.
If your check engine light is on with a cat code, removing it isn't going to change anything unless you replace it with a working part, replacing it with a working part is only going to last if it's not under abnormal stress.

ok i get it now nothing else is leaking or messed up but i get what your saying


All times are GMT -4. The time now is 08:50 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com