? For exhaust guru's

[EasTexRIII]

I think that the low pressure area you are talking about at the exhaust exit compared to the exhaust charge would be like comparing a fart to a Hurricane

My wife says my farts compare purty well, thank ya

 

[Paul Bryant]

Hi Paul,
Thanks. Perhaps I used the term too loosely as you say. My reasoning was that in flow measurement of liquids a more stable flow at lower volumes is obtained if discharging against a nominal back pressure. It helps the liquid amass momentarily then exit more consistently and as you say draws the liquid out which I guess is what your returning shock waves do. The one think that always baffles me (no pun intended) is why do some tuners vent through short, open cut pipes?

It helps the liquid amass momentarily then exit more consistently and as you say draws the liquid out.
Quite correct.

Why do some tuners vent through short, open cut pipes?
This is where headaches are generated, if one starts to over think stuff to much.
Take Bob Carpenters headers for example, very short headers, at the other end of the scale CES have long headers, we know that they both work very well, how can that be
Of coarse Super Charged Engines are whole different ball game, Top Fuelers for example, the Blower is stuffing as much A/F in there as it possibly can, the Exhaust headers are purely directing the spent charge away from the ground.

 

[1olbull]

It helps the liquid amass momentarily then exit more consistently and as you say draws the liquid out.
Quite correct.

Why do some tuners vent through short, open cut pipes?
This is where headaches are generated, if one starts to over think stuff to much.
Take Bob Carpenters headers for example, very short headers, at the other end of the scale CES have long headers, we know that they both work very well, how can that be
Of coarse Super Charged Engines are whole different ball game, Top Fuelers for example, the Blower is stuffing as much A/F in there as it possibly can, the Exhaust headers are purely directing the spent charge away from the ground.

Please continue . . .

 

[mr hunt]

I think that the low pressure area you are talking about at the exhaust exit compared to the exhaust charge would be like comparing a fart to a Hurricane

Ok..science AND fart jokes in the same thread ....

I can see what you mean about relative pressures re atmosphere outside the pipe versus charge inside. I guess I just can't see how at say 3000rpm with a frequency around 50Hz the pulses aren't banging into each other causing attenuation and an evening-out of pressure in the pipe. (Of course I understand that just because I can't get my head around it doesn't mean it's not true )

 

[barbagris]

Take Bob Carpenters headers for example, very short headers, at the other end of the scale CES have long headers, we know that they both work very well, how can that be

It's only maths. Of course the next aspect is VOLUME which flattens the torque curve. My understanding is that the higher the volume the less evident full blown shock wave resonance scavenge is.

 

[mr hunt]

...and the highest performance engines use zoomies so does that mean its the legal requirements for adequate muffling that dictate exhaust tuning as a compromise?

 

[rocketjohn]

It's best not to overthink exhaust.....but think of it in terms of what the factory gave you. It works because it's tuned for the way the engine is set up. If you change the exaust without changing the engine tuning, you will mess it all up. That's all one needs to understand. If you change one, change the other. "nuff said.

 

[Paul Bryant]

It's best not to overthink exhaust.....but think of it in terms of what the factory gave you. It works because it's tuned for the way the engine is set up. If you change the exaust without changing the engine tuning, you will mess it all up. That's all one needs to understand. If you change one, change the other. "nuff said.

It's best not to overthink exhaust..... on the nail there John.
As I said re the Bob Carpenter V CES pipes, all the science/maths etc should add up to the same thing, but in the real world it doesn't.
Too many variables.
Sure to a point you need to do some maths, but when you get all carried away with yards of Science, ya get one hell of a headache, for what end result ?

 

[1K9]

Most small airplane engines just have a header and short pipes out the cowlings. The old radial engines just had headers. Have you seen a P51 Mustang's engine up close. I guess it is about design. Bikes need to be muffled with mufflers to reduce noise pollution. I'm sure there are some complex physics to quiet engine design so EPA approves them for civil use. Changing the intake/power/exhaust power formula without damaging the engine is an art. We thank the racers and Harlistas for throwing the EPA out the window along with their bike's silencers.

Can you imagine what would happen if at the yearly vehicle inspection stations that enforced decibel levels at our exhausts? There would be a few pissed off Mustang and bike riders.

 

[IMFASTTOO]

...and the highest performance engines use zoomies so does that mean its the legal requirements for adequate muffling that dictate exhaust tuning as a compromise?

NO the zoomies are used on supercharged nitro engines

It's best not to overthink exhaust..... on the nail there John.
As I said re the Bob Carpenter V CES pipes, all the science/maths etc should add up to the same thing, but in the real world it doesn't.
Too many variables.
Sure to a point you need to do some maths, but when you get all carried away with yards of Science, ya get one hell of a headache, for what end result ?

YES a lot of trial and error goes into making an exhaust to get the desired performance and looks its not easy thats why none of the home made pipes make good HP CARPENTER makes several different sytems and then we test them on the street and at the Drag strip I know Im the road tester I take the modded bikes out and ride thousands of miles in real world conditions