Educate me on exhaust loops

[Joshin38]

There are offerings for loop delete kits. Am I missing the point of the loop or is it some how cheaper for Jeep to build that loop than to do a direct line like the delete kits do?

Sponsored

 

[TA1ton]

@Joshin38; there are many theories behind having the loop. Short version...it’s good for emissions and low end torque. Long version...it aligns the exhaust gas pulses (both high pressure wave and exhaust gas “slug”) for two big reasons:

1. The high pressure wave, created by the expansion of the exhaust gases, moves down the exhaust pipe and out the end of the pipe. Once it leaves the pipe, a rarefaction (low pressure wave) is reflected back up the pipe. If the length is calculated properly, this low pressure wave will reach the cylinder during the valve overlap period (when both intake and exhaust valves are open). At a given engine speed, this low pressure (think vacuum) will pull more exhaust gases out of the combustion chamber and more fresh air into it. This increases efficiency and power. It is also called scavenging.

2. It aligns the exhaust gas “slugs” so that they are entering the “Y” pipe in a staggered pattern so as to not “bump” into each other. This creates a smoother flow of gases by reducing turbulence which again...leads to more efficiency and power. It also affects the exhaust note of the vehicle.

Now these theories can be implemented in several ways...tuned headers would be another example. Also...still being theories...many people don’t believe it’s true and admittedly, it seems like the benefit would be small. So how much benefit do we see from this loop? Can’t really say...but it is apparently enough to convince FCA to spend the extra money on pipe for hundreds of thousands of Jeeps. Do you need this loop? No...not at all...and there very well could be other benefits from deleting it...engine/exhaust tuning can be broken down to one simple variable...air flow. The more air you can move through an engine...the more fuel you can put in it and therefore increase power and/or efficiency. But in reality...it is a very complex science...

 

[Equitasforall]

@Joshin38; there are many theories behind having the loop. Short version...it’s good for emissions and low end torque. Long version...it aligns the exhaust gas pulses (both high pressure wave and exhaust gas “slug”) for two big reasons:

1. The high pressure wave, created by the expansion of the exhaust gases, moves down the exhaust pipe and out the end of the pipe. Once it leaves the pipe, a rarefaction (low pressure wave) is reflected back up the pipe. If the length is calculated properly, this low pressure wave will reach the cylinder during the valve overlap period (when both intake and exhaust valves are open). At a given engine speed, this low pressure (think vacuum) will pull more exhaust gases out of the combustion chamber and more fresh air into it. This increases efficiency and power. It is also called scavenging.

2. It aligns the exhaust gas “slugs” so that they are entering the “Y” pipe in a staggered pattern so as to not “bump” into each other. This creates a smoother flow of gases by reducing turbulence which again...leads to more efficiency and power. It also affects the exhaust note of the vehicle.

Now these theories can be implemented in several ways...tuned headers would be another example. Also...still being theories...many people don’t believe it’s true and admittedly, it seems like the benefit would be small. So how much benefit do we see from this loop? Can’t really say...but it is apparently enough to convince FCA to spend the extra money on pipe for hundreds of thousands of Jeeps. Do you need this loop? No...not at all...and there very well could be other benefits from deleting it...engine/exhaust tuning can be broken down to one simple variable...air flow. The more air you can move through an engine...the more fuel you can put in it and therefore increase power and/or efficiency. But in reality...it is a very complex science...

Great explanation!

After typing all that though you must be exhausted....

 

[rubileon]

@Joshin38; but it is apparently enough to convince FCA to spend the extra money on pipe for hundreds of thousands of Jeeps.

Good point. It's not like useless vents or the styling lines either because the loop has nothing to do with appearance. They definitely think it's more important than a catch can too.

 

[turbosix]

Good point. It's not like useless vents or the styling lines either because the loop has nothing to do with appearance. They definitely think it's more important than a catch can too.

Lmfaooooo this guy

A production car with a catch can.

 

[rubileon]

Lmfaooooo this guy

A production car with a catch can.

So you got the point

 

[TA1ton]

Great explanation!

After typing all that though you must be exhausted....

I see what you did there...

 

[spurly]

@Joshin38; there are many theories behind having the loop. Short version...it’s good for emissions and low end torque. Long version...it aligns the exhaust gas pulses (both high pressure wave and exhaust gas “slug”) for two big reasons:

1. The high pressure wave, created by the expansion of the exhaust gases, moves down the exhaust pipe and out the end of the pipe. Once it leaves the pipe, a rarefaction (low pressure wave) is reflected back up the pipe. If the length is calculated properly, this low pressure wave will reach the cylinder during the valve overlap period (when both intake and exhaust valves are open). At a given engine speed, this low pressure (think vacuum) will pull more exhaust gases out of the combustion chamber and more fresh air into it. This increases efficiency and power. It is also called scavenging.

2. It aligns the exhaust gas “slugs” so that they are entering the “Y” pipe in a staggered pattern so as to not “bump” into each other. This creates a smoother flow of gases by reducing turbulence which again...leads to more efficiency and power. It also affects the exhaust note of the vehicle.

Now these theories can be implemented in several ways...tuned headers would be another example. Also...still being theories...many people don’t believe it’s true and admittedly, it seems like the benefit would be small. So how much benefit do we see from this loop? Can’t really say...but it is apparently enough to convince FCA to spend the extra money on pipe for hundreds of thousands of Jeeps. Do you need this loop? No...not at all...and there very well could be other benefits from deleting it...engine/exhaust tuning can be broken down to one simple variable...air flow. The more air you can move through an engine...the more fuel you can put in it and therefore increase power and/or efficiency. But in reality...it is a very complex science...

Nicely done. Go grab yourself a beer. (Or drink of choice)

Sponsored