Active Exhaust - Meh?

[Cz_Ziemniak]

When was the last time you saw a 6” diesel exhaust on a mustang?

Whens the last time you saw a restrictor plate on the end of an exhaust to increase backpressure.

Just because backpressure goes up on a more restrictive exhaust does not mean its the reason the engine makes more power. That would be like saying that radiation is good for you because its in the bananas we eat. Well, no, not at all. There's simply more good in bananas that outweighs the bad of the radiation in potassium.

Psst: velocity is a byproduct of resistance

let’s not forget about overlap

Velocity is the product of displacement over time. Its a vector quantity with absolutely no relation to resistance. However, you can certainly add resistance and decrease velocity.

Before you talk down to me, I highly recommend reading a single thing I posted. If you read any of it, I'm sure this would make sense.

Sponsored

 

[Zig]

Whens the last time you saw a restrictor plate on the end of an exhaust to increase backpressure.

Just because backpressure goes up on a more restrictive exhaust does not mean its the reason the engine makes more power. That would be like saying that radiation is good for you because its in the bananas we eat. Well, no, not at all. There's simply more good in bananas that outweighs the bad of the radiation in potassium.




Velocity is the product of displacement over time. Its a vector quantity with absolutely no relation to resistance. However, you can certainly add resistance and decrease velocity.

Before you talk down to me, I highly recommend reading a single thing I posted. If you read any of it, I'm sure this would make sense.

Talk down? Guess you’ve never used your thumb over the end of a garden hose. 100% resistance 0 velocity, minimized opening managed resistance increased velocity however the source pressure didn’t change.

restriction is pressure and the return of pressure back to the cylinder to create pull is what?

 

[Zig]

Whens the last time you saw a restrictor plate on the end of an exhaust to increase backpressure.

Just because backpressure goes up on a more restrictive exhaust does not mean its the reason the engine makes more power. That would be like saying that radiation is good for you because its in the bananas we eat. Well, no, not at all. There's simply more good in bananas that outweighs the bad of the radiation in potassium.




Velocity is the product of displacement over time. Its a vector quantity with absolutely no relation to resistance. However, you can certainly add resistance and decrease velocity.

Before you talk down to me, I highly recommend reading a single thing I posted. If you read any of it, I'm sure this would make sense.

Psst: dual 3” is umm … oh nvm

 

[Cz_Ziemniak]

Talk down? Guess you’ve never used your thumb over the end of a garden hose. 100% resistance 0 velocity, minimized resistance increased velocity however the source pressure didn’t change.

restriction is pressure and the return of pressure back to the cylinder to create pull is what?

So the great thing about bernoullis equation is that when calculating constant flow, both sides equal eachother depending on what you are calculating for. Increasing pressure on the end of the hose increases velocity at the kink, but does not increases the total volume of water through the system. In the real world, it actually decreases the total amount of water, since there is a restriction on the system, and typically the load cannot be overcome fully.

We calculated examples of this for three months in Advanced Fluid Dynamics.

Just because the velocity at the end of the hose is increased does not mean that the velocity behind it is increased. The velocity increase at the end is simply a result of the system needing to evacuate the water when it is flowing at a constant volume at X time. All you are doing is increasing the load at the source of the system. The source (In this case being our engine) has to work harder to maintain a constant flow because of the restriction

If you have 10 gal/min of flow, and you put a thumb over the hose, you do not suddenly have 11 gal/min of flow, rather you have 10 gal/min of flow at a higher velocity AT THE END of the hose. The source of the flow is not also flowing faster.

Lets propose a scenario where we do not factor in scavenging. Scavenging in this example does not exist, period. If you are pumping out exhaust at, say, 100 m/s with a pipe thats 3", and 300 m/s with a pipe thats 1.0", and the engine for both pipes is stable at 4000 rpm, the smaller pipe with the higher velocity is not good because the exhaust has a higher velocity. The higher velocity is simply because the engine is pumping the same volume of exhaust through a smaller orifice. The total volume of exhaust moved per minute in both scenarios is the same. HOWEVER, the engine that has to pump through the 1.0" exhaust is likely under greater load due to the restriction caused by the smaller diameter plumbing (remember, not considering exhaust scavenging which is a completely separate variable from back pressure. The two do not have a relationship). Remember, In both scenarios, the engine maintains 4000 rpm. The total volume of exhaust gasses moved stays the same.

Read a single link I posted, otherwise you are intentionally being thickheaded and choosing to not learn something. People have tested this and provided data.

 

[Zig]

So the great thing about bernoullis equation is that when calculating constant flow, both sides equal eachother depending on what you are calculating for. Increasing pressure on the end of the hose increases velocity at the kink, but does not increases the total volume of water through the system. In the real world, it actually decreases the total amount of water, since there is a restriction on the system, and typically the load cannot be overcome fully.

We calculated examples of this for three months in Advanced Fluid Dynamics.

Just because the velocity at the end of the hose is increased does not mean that the velocity behind it is increased. The velocity increase at the end is simply a result of the system needing to evacuate the water when it is flowing at a constant volume at X time. All you are doing is increasing the load at the source of the system. The source (In this case being our engine) has to work harder to maintain a constant flow because of the restriction

If you have 10 gal/min of flow, and you put a thumb over the hose, you do not suddenly have 11 gal/min of flow, rather you have 10 gal/min of flow at a higher velocity AT THE END of the hose. The source of the flow is not also flowing faster.

Lets propose a scenario where we do not factor in scavenging. Scavenging in this example does not exist, period. If you are pumping out exhaust at, say, 100 m/s with a pipe thats 3", and 300 m/s with a pipe thats 1.0", and the engine for both pipes is stable at 4000 rpm, the smaller pipe with the higher velocity is not good because the exhaust has a higher velocity. The higher velocity is simply because the engine is pumping the same volume of exhaust through a smaller orifice. The total volume of exhaust moved per minute in both scenarios is the same. HOWEVER, the engine that has to pump through the 1.0" exhaust is likely under greater load due to the restriction caused by the smaller diameter plumbing (remember, not considering exhaust scavenging which is a completely separate variable from back pressure. The two do not have a relationship). Remember, In both scenarios, the engine maintains 4000 rpm. The total volume of exhaust gasses moved stays the same.

Read a single link I posted, otherwise you are intentionally being thickheaded and choosing to not learn something. People have tested this and provided data.

Now do exhaust valve overlap

 

[Cz_Ziemniak]

Now do exhaust valve overlap

I can almost guarantee that you are just reading off of Chat GPT, or Google AI, or whatever else.

"Stock backpressure is around 16 psi in a GSR. Good aftermarket exhausts yield 2-5 psi backpressure. "Bolt-ons only" engine packages, in the past, used exhausts with some backpressure, since there is this incorrect belief that having a little backpressure prevents the fresh air/fuel from shooting into the header at cam overlap (when both the opening intake valve & the closing exhaust valve are simultaneously, partially open). The backpressure supposedly "pushed" the fresh air/fuel back into the combustion chamber rather than having it go into the header. This shooting of fresh air/fuel from the intake manifold and intake port into the header cannot happen at cam overlap, since the pressure inside the header is already much higher than on the intake side , even when there is zero backpressure.

In reality, having more backpressure reduces the difference between the higher pressure in the head's exhaust port and lower pressure in the header and cat. You need this difference in pressure going from the head to the exhaust system or "pressure gradient" to keep the exhaust flow speed or energy at a high level. Having some backpressure during cam overlap and the exhaust stroke means that the exhaust gas must now push against something and therefore, this backwards force slows exhaust gas down.

This need for backpressure no longer exists when you have a properly tuned (timed) engine and a good stepped header. In fact, increased backpressure may lead to backwards flow or "reversion", where the exhaust gas travels backwards into the combustion chamber and dilutes the fresh intake charge at cam overlap. At the very least, it slows exhaust flow velocity or energy and prevents the creation of a vacuum for scavenging. "

Lets try another one
"

QUOTE: Back-pressure is useful to make torque in both NA and FI cars that have valve overlap at low rpm... but ultimately restrictive on the top end. What the OP has completely missed in a generic sense (as the N54 has VANOS and may or may not have overlap at lower rpm), is that traditionally, performance cars have a period of valve overlap where the exhaust valve is closing (but not closed) while the intake valve is opening and filling the cylinder with the new fresh air charge. At low rpm, there is nothing keeping (some of) the fresh air charge from escaping out the closing exhaust valve. When this happens you have less than ideal cylinder fill, and less torque at low rpm. Having smaller pipes or restrictive catalytic converters can create a backpressure that keeps the fresh air charge from exiting the closing exhaust valve as easily. This can be felt as more low-end torque as the cylinder is filled more fully with fresh air. At high rpm all you would feel is the restriction of torque by the cats/small pipes as the engine is working efficiently enough to fill the cylinders and then some (intake manifold positive pressure). This works two ways on a turbocharged car.... the low rpm backpressure helps create engine "load" as better cylinder fill makes for higher energy exhaust gases, which would theoretically feel like faster spool up. However, the backpressure works against spool as the turbocharge can not spin up as freely as its pushing against this backpressure. This conversation may or may not be moot depending on how restrictive a turbo(s) exhaust side is to begin with....

RESPONSE: You are completely wrong concerning turbo cars, and somewhat right for the wrong reasons concerning NA cars. Turbo spool up with regard to exhaust plumbing is primarily determined by the pressure differential across the turbine. If you want better spool at lower rpm, you can either decrease pressure in the downpipe, or increase pressure in the exhaust manifold. Increasing pressure in the manifold hurts higher RPM performance, while reducing pressure in the downpipe continues to help at higher RPM.

On NA engines, the effect is almost entirely due to pressure wave tuning. Smaller/longer header primaries/secondaries line up low pressure pulses with valve events at low RPM, while larger/shorter pipes time the low pressure pulses better at higher RPM. During the valve overlap period, a well timed low pressure pulse in the header primary will cause the cylinder pressure to drop further below what piston action would naturally cause, which will allow more air from the intake to fill the cylinder. This pressure wave tuning also works for the intake manifold. The intake is not inherently higher pressure at high RPM as you suggest, rather at the higher flow rates, the pressure is lower.
."

Heres a great one:
"
Back pressure is the basically resistance to the flow of exhaust gas from the cylinder to the exhaust system, this pressure has to be overcome by the piston to push the gas out and it robs the engine of potential torque (part of the parasitic/pumping losses you may have read about). If you have 5 psi (gauge), a piston diameter of 4" and a stroke of 3", that means the force on the piston is 62.8 lbf (piston are times pressure) and a peak torque load of 94 lbs.ft (force times crank throw - half the stroke). As the pressure in the exhaust ports of turbo-charged engines can be twice the boost pressure, or worse for restrictive housings, you can see how that can rob you of a LOT of potential.

That same back pressure can also reduce the amount of incoming fuel-air charge at the top of the stroke, when there is overlap, and can actually pass exhaust gas into the intake ports - with carb's cars with lumpy camshafts this can be seen as fuel stand-off, which is a mist of fuel around the intakes caused by the air in the intake being pushed out throught the carb and it causes a very rich condition (part of the incoming air passing through the venturi three times!). With fuel injection it isn't as critical, but can still cause issues with, especially, MAF based systems.

By this point, you're probably wondering why some people swear engines need back pressure? It comes down to the engine breathing characteristics and, especially, how the high and low pressure pulses, or waves, are moving in the ports. With a NA engine, especially, careful design can 'tune' the exhaust so a low(er) pressure is at the exhaust valve as the engine is around TDC to help draw the charge into the engine - old farts like us sometimes call this coming onto the pipe, coming on song, coming onto the cam, and you can usually hear it clearly. That sounds great but at different rpm you can have a higher pressure pulse there which you DON'T want - so, what to do? Most OEM manufacturers will opt for exhaust designs that either/or dampen these pressure waves or move them outside the operating range so they have less affect on the engine.

So, what happens if you make a change to the exhaust to lower the back pressure? It changes the breathing, especially around overlap, and if this isn't catered for, with fuelling corrections, there will often be a power loss and so the ignorant will say - you need back pressure... The truth is you would make the best torque/power if the exhaust was connected to a vacuum - BUT the engine will need to be designed and tuned for it.

Get the intake and exhaust tuning (where the term originated - you 'tune' the lengths of the pipes, and it dates back to early steam engines...) right and you can get amazing efficiencies - the bike and F1 racing engines are/were approaching 160%, while a normal NA 4 valve road car is around 85-90%."

Final question:

If you didn't eat breakfast this morning, how would you feel?

 

[Zig]

I can almost guarantee that you are just reading off of Chat GPT, or Google AI, or whatever else.

"Stock backpressure is around 16 psi in a GSR. Good aftermarket exhausts yield 2-5 psi backpressure. "Bolt-ons only" engine packages, in the past, used exhausts with some backpressure, since there is this incorrect belief that having a little backpressure prevents the fresh air/fuel from shooting into the header at cam overlap (when both the opening intake valve & the closing exhaust valve are simultaneously, partially open). The backpressure supposedly "pushed" the fresh air/fuel back into the combustion chamber rather than having it go into the header. This shooting of fresh air/fuel from the intake manifold and intake port into the header cannot happen at cam overlap, since the pressure inside the header is already much higher than on the intake side , even when there is zero backpressure.

In reality, having more backpressure reduces the difference between the higher pressure in the head's exhaust port and lower pressure in the header and cat. You need this difference in pressure going from the head to the exhaust system or "pressure gradient" to keep the exhaust flow speed or energy at a high level. Having some backpressure during cam overlap and the exhaust stroke means that the exhaust gas must now push against something and therefore, this backwards force slows exhaust gas down.

This need for backpressure no longer exists when you have a properly tuned (timed) engine and a good stepped header. In fact, increased backpressure may lead to backwards flow or "reversion", where the exhaust gas travels backwards into the combustion chamber and dilutes the fresh intake charge at cam overlap. At the very least, it slows exhaust flow velocity or energy and prevents the creation of a vacuum for scavenging. "

Lets try another one
"

QUOTE: Back-pressure is useful to make torque in both NA and FI cars that have valve overlap at low rpm... but ultimately restrictive on the top end. What the OP has completely missed in a generic sense (as the N54 has VANOS and may or may not have overlap at lower rpm), is that traditionally, performance cars have a period of valve overlap where the exhaust valve is closing (but not closed) while the intake valve is opening and filling the cylinder with the new fresh air charge. At low rpm, there is nothing keeping (some of) the fresh air charge from escaping out the closing exhaust valve. When this happens you have less than ideal cylinder fill, and less torque at low rpm. Having smaller pipes or restrictive catalytic converters can create a backpressure that keeps the fresh air charge from exiting the closing exhaust valve as easily. This can be felt as more low-end torque as the cylinder is filled more fully with fresh air. At high rpm all you would feel is the restriction of torque by the cats/small pipes as the engine is working efficiently enough to fill the cylinders and then some (intake manifold positive pressure). This works two ways on a turbocharged car.... the low rpm backpressure helps create engine "load" as better cylinder fill makes for higher energy exhaust gases, which would theoretically feel like faster spool up. However, the backpressure works against spool as the turbocharge can not spin up as freely as its pushing against this backpressure. This conversation may or may not be moot depending on how restrictive a turbo(s) exhaust side is to begin with....

RESPONSE: You are completely wrong concerning turbo cars, and somewhat right for the wrong reasons concerning NA cars. Turbo spool up with regard to exhaust plumbing is primarily determined by the pressure differential across the turbine. If you want better spool at lower rpm, you can either decrease pressure in the downpipe, or increase pressure in the exhaust manifold. Increasing pressure in the manifold hurts higher RPM performance, while reducing pressure in the downpipe continues to help at higher RPM.

On NA engines, the effect is almost entirely due to pressure wave tuning. Smaller/longer header primaries/secondaries line up low pressure pulses with valve events at low RPM, while larger/shorter pipes time the low pressure pulses better at higher RPM. During the valve overlap period, a well timed low pressure pulse in the header primary will cause the cylinder pressure to drop further below what piston action would naturally cause, which will allow more air from the intake to fill the cylinder. This pressure wave tuning also works for the intake manifold. The intake is not inherently higher pressure at high RPM as you suggest, rather at the higher flow rates, the pressure is lower.
."

Heres a great one:
"
Back pressure is the basically resistance to the flow of exhaust gas from the cylinder to the exhaust system, this pressure has to be overcome by the piston to push the gas out and it robs the engine of potential torque (part of the parasitic/pumping losses you may have read about). If you have 5 psi (gauge), a piston diameter of 4" and a stroke of 3", that means the force on the piston is 62.8 lbf (piston are times pressure) and a peak torque load of 94 lbs.ft (force times crank throw - half the stroke). As the pressure in the exhaust ports of turbo-charged engines can be twice the boost pressure, or worse for restrictive housings, you can see how that can rob you of a LOT of potential.

That same back pressure can also reduce the amount of incoming fuel-air charge at the top of the stroke, when there is overlap, and can actually pass exhaust gas into the intake ports - with carb's cars with lumpy camshafts this can be seen as fuel stand-off, which is a mist of fuel around the intakes caused by the air in the intake being pushed out throught the carb and it causes a very rich condition (part of the incoming air passing through the venturi three times!). With fuel injection it isn't as critical, but can still cause issues with, especially, MAF based systems.

By this point, you're probably wondering why some people swear engines need back pressure? It comes down to the engine breathing characteristics and, especially, how the high and low pressure pulses, or waves, are moving in the ports. With a NA engine, especially, careful design can 'tune' the exhaust so a low(er) pressure is at the exhaust valve as the engine is around TDC to help draw the charge into the engine - old farts like us sometimes call this coming onto the pipe, coming on song, coming onto the cam, and you can usually hear it clearly. That sounds great but at different rpm you can have a higher pressure pulse there which you DON'T want - so, what to do? Most OEM manufacturers will opt for exhaust designs that either/or dampen these pressure waves or move them outside the operating range so they have less affect on the engine.

So, what happens if you make a change to the exhaust to lower the back pressure? It changes the breathing, especially around overlap, and if this isn't catered for, with fuelling corrections, there will often be a power loss and so the ignorant will say - you need back pressure... The truth is you would make the best torque/power if the exhaust was connected to a vacuum - BUT the engine will need to be designed and tuned for it.

Get the intake and exhaust tuning (where the term originated - you 'tune' the lengths of the pipes, and it dates back to early steam engines...) right and you can get amazing efficiencies - the bike and F1 racing engines are/were approaching 160%, while a normal NA 4 valve road car is around 85-90%."

Final question:

If you didn't eat breakfast this morning, how would you feel?

Bolt on or raw build requires math

 

[Cz_Ziemniak]

Bolt on or raw build requires math

If you didn't have breakfast this morning, how would you feel?

 

[Zig]

I can almost guarantee that you are just reading off of Chat GPT, or Google AI, or whatever else.

"Stock backpressure is around 16 psi in a GSR. Good aftermarket exhausts yield 2-5 psi backpressure. "Bolt-ons only" engine packages, in the past, used exhausts with some backpressure, since there is this incorrect belief that having a little backpressure prevents the fresh air/fuel from shooting into the header at cam overlap (when both the opening intake valve & the closing exhaust valve are simultaneously, partially open). The backpressure supposedly "pushed" the fresh air/fuel back into the combustion chamber rather than having it go into the header. This shooting of fresh air/fuel from the intake manifold and intake port into the header cannot happen at cam overlap, since the pressure inside the header is already much higher than on the intake side , even when there is zero backpressure.

In reality, having more backpressure reduces the difference between the higher pressure in the head's exhaust port and lower pressure in the header and cat. You need this difference in pressure going from the head to the exhaust system or "pressure gradient" to keep the exhaust flow speed or energy at a high level. Having some backpressure during cam overlap and the exhaust stroke means that the exhaust gas must now push against something and therefore, this backwards force slows exhaust gas down.

This need for backpressure no longer exists when you have a properly tuned (timed) engine and a good stepped header. In fact, increased backpressure may lead to backwards flow or "reversion", where the exhaust gas travels backwards into the combustion chamber and dilutes the fresh intake charge at cam overlap. At the very least, it slows exhaust flow velocity or energy and prevents the creation of a vacuum for scavenging. "

Lets try another one
"

QUOTE: Back-pressure is useful to make torque in both NA and FI cars that have valve overlap at low rpm... but ultimately restrictive on the top end. What the OP has completely missed in a generic sense (as the N54 has VANOS and may or may not have overlap at lower rpm), is that traditionally, performance cars have a period of valve overlap where the exhaust valve is closing (but not closed) while the intake valve is opening and filling the cylinder with the new fresh air charge. At low rpm, there is nothing keeping (some of) the fresh air charge from escaping out the closing exhaust valve. When this happens you have less than ideal cylinder fill, and less torque at low rpm. Having smaller pipes or restrictive catalytic converters can create a backpressure that keeps the fresh air charge from exiting the closing exhaust valve as easily. This can be felt as more low-end torque as the cylinder is filled more fully with fresh air. At high rpm all you would feel is the restriction of torque by the cats/small pipes as the engine is working efficiently enough to fill the cylinders and then some (intake manifold positive pressure). This works two ways on a turbocharged car.... the low rpm backpressure helps create engine "load" as better cylinder fill makes for higher energy exhaust gases, which would theoretically feel like faster spool up. However, the backpressure works against spool as the turbocharge can not spin up as freely as its pushing against this backpressure. This conversation may or may not be moot depending on how restrictive a turbo(s) exhaust side is to begin with....

RESPONSE: You are completely wrong concerning turbo cars, and somewhat right for the wrong reasons concerning NA cars. Turbo spool up with regard to exhaust plumbing is primarily determined by the pressure differential across the turbine. If you want better spool at lower rpm, you can either decrease pressure in the downpipe, or increase pressure in the exhaust manifold. Increasing pressure in the manifold hurts higher RPM performance, while reducing pressure in the downpipe continues to help at higher RPM.

On NA engines, the effect is almost entirely due to pressure wave tuning. Smaller/longer header primaries/secondaries line up low pressure pulses with valve events at low RPM, while larger/shorter pipes time the low pressure pulses better at higher RPM. During the valve overlap period, a well timed low pressure pulse in the header primary will cause the cylinder pressure to drop further below what piston action would naturally cause, which will allow more air from the intake to fill the cylinder. This pressure wave tuning also works for the intake manifold. The intake is not inherently higher pressure at high RPM as you suggest, rather at the higher flow rates, the pressure is lower.
."

Heres a great one:
"
Back pressure is the basically resistance to the flow of exhaust gas from the cylinder to the exhaust system, this pressure has to be overcome by the piston to push the gas out and it robs the engine of potential torque (part of the parasitic/pumping losses you may have read about). If you have 5 psi (gauge), a piston diameter of 4" and a stroke of 3", that means the force on the piston is 62.8 lbf (piston are times pressure) and a peak torque load of 94 lbs.ft (force times crank throw - half the stroke). As the pressure in the exhaust ports of turbo-charged engines can be twice the boost pressure, or worse for restrictive housings, you can see how that can rob you of a LOT of potential.

That same back pressure can also reduce the amount of incoming fuel-air charge at the top of the stroke, when there is overlap, and can actually pass exhaust gas into the intake ports - with carb's cars with lumpy camshafts this can be seen as fuel stand-off, which is a mist of fuel around the intakes caused by the air in the intake being pushed out throught the carb and it causes a very rich condition (part of the incoming air passing through the venturi three times!). With fuel injection it isn't as critical, but can still cause issues with, especially, MAF based systems.

By this point, you're probably wondering why some people swear engines need back pressure? It comes down to the engine breathing characteristics and, especially, how the high and low pressure pulses, or waves, are moving in the ports. With a NA engine, especially, careful design can 'tune' the exhaust so a low(er) pressure is at the exhaust valve as the engine is around TDC to help draw the charge into the engine - old farts like us sometimes call this coming onto the pipe, coming on song, coming onto the cam, and you can usually hear it clearly. That sounds great but at different rpm you can have a higher pressure pulse there which you DON'T want - so, what to do? Most OEM manufacturers will opt for exhaust designs that either/or dampen these pressure waves or move them outside the operating range so they have less affect on the engine.

So, what happens if you make a change to the exhaust to lower the back pressure? It changes the breathing, especially around overlap, and if this isn't catered for, with fuelling corrections, there will often be a power loss and so the ignorant will say - you need back pressure... The truth is you would make the best torque/power if the exhaust was connected to a vacuum - BUT the engine will need to be designed and tuned for it.

Get the intake and exhaust tuning (where the term originated - you 'tune' the lengths of the pipes, and it dates back to early steam engines...) right and you can get amazing efficiencies - the bike and F1 racing engines are/were approaching 160%, while a normal NA 4 valve road car is around 85-90%."

Final question:

If you didn't eat breakfast this morning, how would you feel?

You still haven’t explained why we aint just running huge pipes, big block small block big difference

 

[Cz_Ziemniak]

You still haven’t explained why we aint just running huge pipes, big block small block big difference

I have, you've just chosen not to read a single thing I have posted, wrote, or replied with beyond what you found to fit your criteria.

 

[Zig]

I have, you've just chosen not to read a single thing I have posted, wrote, or replied with beyond what you found to fit your criteria.

and you said but i’ve got a feeling you may guilty of the accusation…

I can almost guarantee that you are just reading off of Chat GPT, or Google AI, or whatever else.

 

[Cz_Ziemniak]

I'm just going to start quoting things I've already wrote man. I'm making references from both my engineering background, as well as other sources which have literally tested and posted results to the hypothesis. Heres your answer, and I'm leaving it at this. If you can't be convinced by the abundance of information on the topic, then its your loss.

Testing Data:
https://motordyneengineering.com/scavenging-and-the-exhaust-backpressure-myth/

My Previous Response:
"So the great thing about bernoullis equation is that when calculating constant flow, both sides equal eachother depending on what you are calculating for. Increasing pressure on the end of the hose increases velocity at the kink, but does not increases the total volume of water through the system. In the real world, it actually decreases the total amount of water, since there is a restriction on the system, and typically the load cannot be overcome fully.

We calculated examples of this for three months in Advanced Fluid Dynamics.

Just because the velocity at the end of the hose is increased does not mean that the velocity behind it is increased. The velocity increase at the end is simply a result of the system needing to evacuate the water when it is flowing at a constant volume at X time. All you are doing is increasing the load at the source of the system. The source (In this case being our engine) has to work harder to maintain a constant flow because of the restriction

If you have 10 gal/min of flow, and you put a thumb over the hose, you do not suddenly have 11 gal/min of flow, rather you have 10 gal/min of flow at a higher velocity AT THE END of the hose. The source of the flow is not also flowing faster.

Lets propose a scenario where we do not factor in scavenging. Scavenging in this example does not exist, period. If you are pumping out exhaust at, say, 100 m/s with a pipe thats 3", and 300 m/s with a pipe thats 1.0", and the engine for both pipes is stable at 4000 rpm, the smaller pipe with the higher velocity is not good because the exhaust has a higher velocity. The higher velocity is simply because the engine is pumping the same volume of exhaust through a smaller orifice. The total volume of exhaust moved per minute in both scenarios is the same. HOWEVER, the engine that has to pump through the 1.0" exhaust is likely under greater load due to the restriction caused by the smaller diameter plumbing (remember, not considering exhaust scavenging which is a completely separate variable from back pressure. The two do not have a relationship). Remember, In both scenarios, the engine maintains 4000 rpm. The total volume of exhaust gasses moved stays the same.

Read a single link I posted, otherwise you are intentionally being thickheaded and choosing to not learn something. People have tested this and provided data. "

As for this:

and you said but i’ve got a feeling you may guilty of the accusation…

The fact I am literally quoting sources should clue you in that I'm not.

 

[Zig]

I'm just going to start quoting things I've already wrote man. I'm making references from both my engineering background, as well as other sources which have literally tested and posted results to the hypothesis. Heres your answer, and I'm leaving it at this. If you can't be convinced by the abundance of information on the topic, then its your loss.

Testing Data:
https://motordyneengineering.com/scavenging-and-the-exhaust-backpressure-myth/

My Previous Response:
"So the great thing about bernoullis equation is that when calculating constant flow, both sides equal eachother depending on what you are calculating for. Increasing pressure on the end of the hose increases velocity at the kink, but does not increases the total volume of water through the system. In the real world, it actually decreases the total amount of water, since there is a restriction on the system, and typically the load cannot be overcome fully.

We calculated examples of this for three months in Advanced Fluid Dynamics.

Just because the velocity at the end of the hose is increased does not mean that the velocity behind it is increased. The velocity increase at the end is simply a result of the system needing to evacuate the water when it is flowing at a constant volume at X time. All you are doing is increasing the load at the source of the system. The source (In this case being our engine) has to work harder to maintain a constant flow because of the restriction

If you have 10 gal/min of flow, and you put a thumb over the hose, you do not suddenly have 11 gal/min of flow, rather you have 10 gal/min of flow at a higher velocity AT THE END of the hose. The source of the flow is not also flowing faster.

Lets propose a scenario where we do not factor in scavenging. Scavenging in this example does not exist, period. If you are pumping out exhaust at, say, 100 m/s with a pipe thats 3", and 300 m/s with a pipe thats 1.0", and the engine for both pipes is stable at 4000 rpm, the smaller pipe with the higher velocity is not good because the exhaust has a higher velocity. The higher velocity is simply because the engine is pumping the same volume of exhaust through a smaller orifice. The total volume of exhaust moved per minute in both scenarios is the same. HOWEVER, the engine that has to pump through the 1.0" exhaust is likely under greater load due to the restriction caused by the smaller diameter plumbing (remember, not considering exhaust scavenging which is a completely separate variable from back pressure. The two do not have a relationship). Remember, In both scenarios, the engine maintains 4000 rpm. The total volume of exhaust gasses moved stays the same.

Read a single link I posted, otherwise you are intentionally being thickheaded and choosing to not learn something. People have tested this and provided data. "

As for this:

The fact I am literally quoting sources should clue you in that I'm not.

Have you done any of this or just played on paper?

 

[Cz_Ziemniak]

Sorry, didn't realize that calculating equations is just playing on paper. My bad G, let me just huff some glue and get on your level.

No, I have not intentionally put restrictors on my exhaust under the assumption that it will allow my car to make more power. I simply put whatever has been proven to work, typically for better scavenging.

Back pressure is not advantageous, champ.

 

[Zig]

Sorry, didn't realize that calculating equations is just playing on paper. My bad G, let me just huff some glue and get on your level.

No, I have not intentionally put restrictors on my exhaust under the assumption that it will allow my car to make more power. I simply put whatever has been proven to work, typically for better scavenging.

Back pressure is not advantageous, champ.

Try taking the cats off

Sponsored