Hey guys,
Im new to this site but have been messing around with my ram since i got it in 2006. I have a 06 hemi and have changed my exhaust many times... I now have pacesetter LT's, off road y-pipe and a magnaflow muffler with a turn down before the rear. Do you all think this is creating enough back pressure? The other issues as far as my exhaust goes is that my truck has a 4/6 drop on it and moes performance traction bars so it kinda limits my options. Just wondering what you all think about the back pressure.. thanks

 

No engine on EARTH will bennifit from "BACK PRESSURE"!

OLD SCHOOLERS used to suggest "BACK PRESSURE" had en effect on HP after going to an exhaust too large they just assumed a loss in "BACK PRESSURE" caused the low end torque loss.

But the fact is, it was not the loss of "BACK PRESSURE" that was lost... it was "VELOCITY" that was lost from going to a too large of an exhaust system.

Back pressure is exactly what it says it is... Its a RESTRICTION!

You exhaust system either promotes:

BACK PRESSURE = WORST
LOW VELOCITY = POOR
HIGH VELOCITY = BEST

Choosing a system that promotes HIGH VELOCITY throughout the system at your desired RPM range will give you the best performance. This is why single exhaust systems have been becoming very popular in the performance world... With dual exhaust its very easy to go too large which kills velocity. They also tend to lose heat... which is energy, and aids in keeping the velocity high in the system.

A single exhaust system allows you to promote High Velocity and retain more heat throughout the system... all good for velocity.

Velocity is good because it has a key in scavenging exhaust gas from the cylinder when the exhaust valve opens... at this point there is an overlap where you have both the INTAKE & EXHAUST valves open at the same time. A high pulse on the exhaust side can/will suck on the intake side and give the intake charge a running charge into the cylinder... This is commonly known as the scavenging effect.

So Too large of a system = LOW VELOCITY POOR LOW END POWER
Too Small of a system = BACK PRESSURE
The right size system = HIGH VELOCITY GREAT LOW END & TOP END POWER

The 4.7L engine seems to perform well with a true single 3" exhaust system. While most 5.7L engines would benefit from the same single 3" system, a single 3.25" would be ideal for the 5.7L.

SPEED SAFE, AIR RAM

 

I have 2.25 dual outs on my 05 ram, but did not really notice a loss in power

 

If you must go duals then 2.25 is about right for both the 4.7L & 5.7L..

SPEED SAFE, AIR RAM

 

Back pressure was for the old timer cars with Carburators. Newer fuel injected cars can have stright headers and have no driveability issues

 

Im not to sure about that... The old timers never really knew why they lost torque and just blamed it on back pressure.

ALL engines with overlapping cams will benefit from an exhaust system that promotes high velocity.

I just drove my truck with "OPEN HEADERS" to our exhaust guys shop... That was a nightmare and I though I was going to brake down on the side of the road. So I know the PCM did not like the open headers. Sure I bet it could be tuned to run open. But torque will still suffer do to the lack of velocity.

SPEED SAFE, AIR RAM

 

I will have to
disagree just beacause
I can and I have
nothing else to
contribute.
I have never
had any experience
in any way regarding this
question so I would just like to argue
and talk about how it's Air_Ram's
custom intakes that cause you
velocity problems and
not the exhaust
LMAO
j/k...lol


The velocity concept is true and depends on how long the primaries are and how the firecone is constructed which help the most in this situation. Definately would need a tune, but it was a mere exaggeration simply to give an example if that makes sense? Anyone running stright pipes out the back with virtually no bends will benefit the most, ofcourse this is tough to do in most situations so any bends that are placed in the tubing will add to the amount of pressure build up in the system along with turbulence, but the turbulence is so far past the headers it makes minimal difference. Please correct me if I am wrong as I have no problems in learning. Sorry for the spamming above, but it was an urge that hadn't been fulfilled by the normal member...lol

 

That was funny...

Well your right in a since but off a little. The VOLUME of the exhaust pipe must be matched to the power output of the engine in order to promote high velocity in the system. Its important to understand that your exhaust system can in fact MAKE HP/TQ not just fee it up.

A misconception is that exhaust work only FREE'S UP HP/TQ... Sure if its restrictive... but it can also MAKE more HP/TQ if the right volume pipe is selected. Some engines are built to run off headers alone... but their cams are chosen for that. A factory engine with stock cams... even most aftermarket cams need a well designed exhaust system that promotes the SCAVENGING EFFECT to make the most hp/tq.

The larger the pipe you go, the higher the engine needs to rev to create the needed velocity to scavenge from the cylinders. This is where you can tune the exhaust to be more effective in the area you need it to be.

I'm a fan of a SINGLE 3" system on most engines 5.0L to 5.7L... or any engine making from 300RWHP up to 400RWHP... Since the 4.7L engine likes to rev. It also benefits from that same 3" single. I feel FULL LENGTH systems are best on street driven trucks that may Haul or tow... I'm just a fan of torque when dealing with trucks!

The right exhaust system will MAKE torque and horsepower... not just free it up.

SPEED SAFE, AIR RAM

 

I know for a fact that Airram is correct.Growing up the son and nephew of mechanics,i was always taught an engine must ''breathe''with plenty of air flow from intake through exhaust.I have seen many dyno test with same vehicle and several exhaust setups (open,headers,straight,duals and singles) that completely changed my thoughts on performance exhaust modification.Back pressure is what you get after a long day at work not what your exhaust needs.

 

So, the Magnaflow side exit exhaust that dumps just infront of the rear wheel not good for towing? You think over the axle and out the side is better?