[EvoRK]

Only takes a small amount of back pressure to make a big difference in low end torque.

Ahh the old back pressure myth again

 

[Shunned]

Ahh the old back pressure myth again

A common example of backpressure is that caused by the exhaust system (consisting of the exhaust manifold, catalytic converter, muffler and connecting pipes) of an automotive four-stroke engine, which has a negative effect on engine efficiency, resulting in a decrease of power output that must be compensated by increasing fuel consumption.

copy and pasted

 

[JLR]

Shunned you are a one track mind kind of stupid. Do you think racing is all at wot and short runs? I have built and tuned many racing engines, all successful. They did not need rebuilding after a few runs. Yes some were drag racing, but most were circle track. Now sharpen up on your building skills and you won't be rebuilding every week.

You can restrict the exhaust flow on your engines if you want, I'll get mine tuned.

Jeez

 

[Shunned]

jlr you have proven you are a waste of my time. Trying to compare a water cooled v8 to a air cooled v twin is what is stupid. Whether you ever get it figured out or not, I could care less.

 

[JLR]

They were all motorcycles except the V stock NHRA national record holder I prepped the block on. Lots of 2 stroke experience too. One of my favorite Smokey Yunick quotes is: an engine doesn't know what name is on the valve cover. I doubt you have the experience or the mind to comprehend that though.


"All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919.

 

[Shunned]

They were all motorcycles except the V stock NHRA national record holder I prepped the block on. Lots of 2 stroke experience too. One of my favorite Smokey Yunick quotes is: an engine doesn't know what name is on the valve cover. I doubt you have the experience or the mind to comprehend that though.


"All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919.

if your trying to impress, u might pick somebody else.

edit,
last attempt at explaining what I think is quite simple....
You take a stock engine and remove the stock exhaust. Then you install a new exhaust that is straight through, no baffles, no restriction. instantly you can feel the loss of torque taking off from a stop.

Now you might want to have your bike tuned to the open exhaust but if your going to increase the exhaust flow it would only make sense to get a high flow air filter. Now you have a stage 2 and need to have your bike dyno tuned to add fuel to a lean running engine.

Adding a small amount of back pressure to the exhaust takes the engine back to how it was designed to operate from the beginning. Still at a stage 1 with stock air filter and a exhaust that sounds 10x better than a open pipe, better than the stock exhaust, plus it gives you back that bottom end torque you lost as soon as you changed to a open pipe. See? Simple. lol

 

[slingshot383]

A properly tuned exhaust system on a motorcycle would look really strange and out of place, so they become a compromise of looks and performance.

 

[Shunned]

Back on my wrecked bike when it had drag pipes, I used those inserts in the end to bring back the low end (bike had straight pipes when I got it and I couldn't afford a new set of pipes at the time). The ones that go in the end of the pipe. When you say torque cones, for a second I thought you were talking about the snake oil inserts that go up by the heads (those don't do anything).

The lollipop baffles in the end of the pipe work, depending on the pipe. There's two things at play, one is the harmonic reversion you mentioned (which could be remedied by as little as a screw or bolt in the end). The big thing these particular inserts do, is increase exit velocity. As soon as exhaust hits the air outside of the end of the pipe, slows way down, which causes a build up in the pipe that has to be overcome (the engine has to push it out, which is why it's more a problem at lower RPM). It's a problem with larger diameter pipes because although more free flowing (good at high rpm), they have a lower velocity (which is why the exit slow down is a bigger problem). The lollipop increases velocity just before where it would slow down as well as increases scavenging in the end of the pipe, helping to prevent that pressure build up.

The result is a smoother bottom end and eliminating some of the low-end sag (assuming it's caused by an exhaust that's too big for the engine and rpm range).

"As soon as exhaust hits the air outside of the end of the pipe, slows way down, which causes a build up in the pipe that has to be overcome "

What would you call that "build up"?
However it is explained, it's nice to see someone else that has "actually" tried it has seen the improvement of low end torque. It works the same with baffles, torque plates, lollipops or what ever restricts the exhaust flow at the end of the exhaust. Might be the reason torque plates come in 3 sizes. A small insert in a big pipe will have little to no effect. You have to literally restrict "some" of the exhaust flow with the cone.

 

[EvoRK]

I’m now just here for the entertainment. Trying to figure out how to get more back pressure

 

[Pred8er]

I’m now just here for the entertainment. Trying to figure out how to get more back pressure

Fall for it...lots of back pressure.

 

[Pearl White]

Back in the day a washer was welded to a bolt and attached the same as the cone inserts (lollipops). Did the exact same thing for bottom end torque improvement. This works on jap bikes with gutted baffles just the same. Some people cant comprehend the difference in a race engine vs a street engine. Race engines go straight to WOT to the end of the track, stock, modified engines need to use as much of the available rpm band and gear ratios for street driving. A race engine would not be worth a shit on the street with stop lights, traffic and just dependability. Race engines are not built to go 100,000 miles, they are built to make it to the end of the track then get rebuilt after a few number of runs.

I agree. There are a lot of variables to consider beyond what "racers" do on a street machine that will rarely run at full throttle. Physics is not always user friendly. I used to teach physics and physics plays a large part in my current employment. Test and verify is the only answer. I felt DK documented their test and verify of this product with a healthy amount of dyno runs. Even then I do not preach the power numbers and kerp it to the reason I purchased the inserts. To control the decell popping and improve the sound. Which they did fantasticly. If I am getting more torque its a bonus. Thanks for your reply.

 

[Shunned]

I agree. There are a lot of variables to consider beyond what "racers" do on a street machine that will rarely run at full throttle. Physics is not always user friendly. I used to teach physics and physics plays a large part in my current employment. Test and verify is the only answer. I felt DK documented their test and verify of this product with a healthy amount of dyno runs. Even then I do not preach the power numbers and kerp it to the reason I purchased the inserts. To control the decell popping and improve the sound. Which they did fantasticly. If I am getting more torque its a bonus. Thanks for your reply.

Your welcome. The torque inserts have their own site where they explain how you can also adjust the position of the plates to change the tone or to help with low end torque the most. I can only go by what I have experienced myself and if others do not agree it's no loss to me. They are called "torque inserts" not sound inserts but they do help on both.

Edit , I found the site that helps to explain the benefit of the torque inserts. Maybe it can help.

Performance Motorcycle Exhaust Back Pressure Explained

Trying to gain horsepower in your bike? Learn more about back pressure in your motorcycles exhaust & how to really gain the horsepower you want.

www.tabperformance.com

 

[EvoRK]

Think I’ll pass on reading anything from tab as they are one of the worst performance exhaust you can buy

 

[sardonicus87]

Think I’ll pass on reading anything from tab as they are one of the worst performance exhaust you can buy

Never mind that they call it "back pressure".

To oversimplify it, you get better performance in various RPM ranges based on diameter and length. For street riding, if you put a too high output exhaust, that's where you lose power through the loss of scavenging and velocity, not back pressure.

And to be clear, these inserts don't give you more torque, you can't just slap them in any exhaust for more torque, they just give you back some of the loss when you have the wrong exhaust pipe (usually too big diameter) for the engine/cam setup for your application, which is really only a bandaid on the problem. But they aren't really creating back pressure, they're sort of correcting oversizing (for the intended RPM range and cam) and helping with some scavenging. It's more like what stepped headers do: not add back pressure, but add scavenging. That's why they go at the end of the pipe, where the everything has lost the most velocity. And it goes without saying, the proper exhaust for your setup would produce more power than a modified wrong exhaust.

Exhaust isn't that complicated to understand the basics. Yes, they can get complicated and there can be a lot to them, but...

"The reason why some old timers have said things like 'you need some back pressure to make power and torque' in the past was... well if you have like a really huge, way oversized exhaust, you lose your gas column inertia..." (key part here being "oversized exhaust"). Also "the trick is to get as much velocity through the pipe with as little back pressure as possible, a lot of that is in the correct size tubing for your engine":

 

[EvoRK]

Never mind that they call it "back pressure".

To oversimplify it, you get better performance in various RPM ranges based on diameter and length. For street riding, if you put a too high output exhaust, that's where you lose power through the loss of scavenging and velocity, not back pressure.

And to be clear, these inserts don't give you more torque, you can't just slap them in any exhaust for more torque, they just give you back some of the loss when you have the wrong exhaust pipe (usually too big diameter) for the engine/cam setup for your application, which is really only a bandaid on the problem. But they aren't really creating back pressure, they're sort of correcting oversizing (for the intended RPM range and cam) and helping with some scavenging. It's more like what stepped headers do: not add back pressure, but add scavenging. That's why they go at the end of the pipe, where the everything has lost the most velocity.

Exhaust isn't that complicated to understand the basics. Yes, they can get complicated and there can be a lot to them, but...

"The reason why some old timers have said things like 'you need some back pressure to make power and torque' in the past was... well if you have like a really huge, way oversized exhaust, you lose your gas column inertia..." (key part here being "oversized exhaust"). Also "the trick is to get as much velocity through the pipe with as little back pressure as possible, a lot of that is in the correct size tubing for your engine":

Thanks Kyle for taking the time to correctly explain it Im just over the back pressure sh&&t

 

[sardonicus87]

If you got too much exhaust for your engine, rather than modifying the exhaust to work, just get more engine.

 

[slingshot383]

Ahh, the reason to go with the S&S Grand Nationals instead of the 4.5" Monster Rounds on a stock motor!

 

[Shunned]

Never mind that they call it "back pressure".

To oversimplify it, you get better performance in various RPM ranges based on diameter and length. For street riding, if you put a too high output exhaust, that's where you lose power through the loss of scavenging and velocity, not back pressure.

And to be clear, these inserts don't give you more torque, you can't just slap them in any exhaust for more torque, they just give you back some of the loss when you have the wrong exhaust pipe (usually too big diameter) for the engine/cam setup for your application, which is really only a bandaid on the problem. But they aren't really creating back pressure, they're sort of correcting oversizing (for the intended RPM range and cam) and helping with some scavenging. It's more like what stepped headers do: not add back pressure, but add scavenging. That's why they go at the end of the pipe, where the everything has lost the most velocity. And it goes without saying, the proper exhaust for your setup would produce more power than a modified wrong exhaust.

Exhaust isn't that complicated to understand the basics. Yes, they can get complicated and there can be a lot to them, but...

"The reason why some old timers have said things like 'you need some back pressure to make power and torque' in the past was... well if you have like a really huge, way oversized exhaust, you lose your gas column inertia..." (key part here being "oversized exhaust"). Also "the trick is to get as much velocity through the pipe with as little back pressure as possible, a lot of that is in the correct size tubing for your engine":

Exhaust back pressure? (The answer is found) - Belle Haven Shell

Definition. Engine exhaust back pressure is defined as the exhaust gas pressure that is produced by the engine to overcome the hydraulic resistance of the exhaust system in order to discharge the gases into the atmosphere. First, pressure is a scalar quantity, not a vector quantity, and has no...

belleshell.com

Link where your youtube was posted. For those who care I have always said " a small amount of back pressure"
For those who do not want to open the link and learn something it says....
.
"Do you need back pressure in an exhaust?

As the pulses move along, they generate an exhaust flow. If you have a restrictive exhaust system, it can generate back pressure that works against the positive flow of the exhaust gas that’s trying to exit your vehicle. However, a little back pressure is a good thing. In fact, it helps."

Its a good read if anyone is open minded enough to learn. I learned from it myself.