Is there a general rule about pipe volume??

[Sean Bowf]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

 

[Joe Warren]

Sean....... Fat vs Skinny pipes. I run the same lengths. Smaller pipe (skinny works best in Good Quality air it revs harder & will tune More RPM. Fat (bigger) Pipe is best in poor quality air.(hot humid air or high elevation) What size boat are you working on. Finding the Best baseline pipe & prop is most important. jw

 

[Jim Allen]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

 

[Martin Hamilton]

On the .21 pipes that i make they are 30 X engine capacity with small stingers and smaller headers. A lot of commercial pipes from just a few years ago were only around 24X engine capacity also with large diam stingers and headers. Regards Martin.

 

[Michael Costanzo]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

hi,jimmy,could you tell me were to buy one and were is it supposed to be placed to be checked at WOT? next question is if the stock pipe is not up to specswhat part of the pipe is modified? thanks,mike.

 

[Sean Bowf]

Sean....... Fat vs Skinny pipes. I run the same lengths. Smaller pipe (skinny works best in Good Quality air it revs harder & will tune More RPM. Fat (bigger) Pipe is best in poor quality air.(hot humid air or high elevation) What size boat are you working on. Finding the Best baseline pipe & prop is most important. jw

Joe, not really about any boat in particular, but I have been playing with .21 pipes on my RTR lately. I used a .12 pipe on a .12 rigger I built. It seemed to hit the pipe really moved when it did. That boat had a buggy OS CVR engine in it. So started to think the pipes I use on the RTRs (which never acted like the .12) were too large. My RTR has a .18 cvrm engine in it (so pretty much a marine version of the CVR). So I got a smaller pipe and really could not get the boat to hit the pipe as well as it did with the larger pipe. I did try a little longer, and a little shorter, but not much from where I had the larger pipe (probably within +/- a quarter inch from the larger pipe).

So, really just trying to figure it all out I guess. Figure out if I need to spend more time with the smaller pipe, or move on to some other idea.

Thanks to everyone for your inputs,

Sean

 

[Jim Allen]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

hi,jimmy,could you tell me were to buy one and were is it supposed to be placed to be checked at WOT? next question is if the stock pipe is not up to specswhat part of the pipe is modified? thanks,mike.

Look on line to purchase a gage at a good price. A 1/8 ID line can be tapped from your pressure line if you are using one at the mid point of the pipe. I have also checked it at the header, but the temperature is much lower at the mid point. There is no difference in the readings at either point. If the stock pipe is not working up to specs, you will probably have to make your own pipe from steel or aluminum. Baffle & difuser angles, diameters, plus the length of sections determine pipe characteristics, therefore modification is usually very difficult.

Jim Allen

 

[dwilfong]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

hi,jimmy,could you tell me were to buy one and were is it supposed to be placed to be checked at WOT? next question is if the stock pipe is not up to specswhat part of the pipe is modified? thanks,mike.

Look on line to purchase a gage at a good price. A 1/8 ID line can be tapped from your pressure line if you are using one at the mid point of the pipe. I have also checked it at the header, but the temperature is much lower at the mid point. There is no difference in the readings at either point. If the stock pipe is not working up to specs, you will probably have to make your own pipe from steel or aluminum. Baffle & difuser angles, diameters, plus the length of sections determine pipe characteristics, therefore modification is usually very difficult.

Jim Allen

Jim I am most interested in your finding about pipe pressure. How do you obtain the readings . I assume you get the readings while running on the Dino. Is their any other way to get good readings for those of us that don't have a Dino.

David

 

[Jim Allen]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

hi,jimmy,could you tell me were to buy one and were is it supposed to be placed to be checked at WOT? next question is if the stock pipe is not up to specswhat part of the pipe is modified? thanks,mike.

Look on line to purchase a gage at a good price. A 1/8 ID line can be tapped from your pressure line if you are using one at the mid point of the pipe. I have also checked it at the header, but the temperature is much lower at the mid point. There is no difference in the readings at either point. If the stock pipe is not working up to specs, you will probably have to make your own pipe from steel or aluminum. Baffle & difuser angles, diameters, plus the length of sections determine pipe characteristics, therefore modification is usually very difficult.

Jim Allen

Jim I am most interested in your finding about pipe pressure. How do you obtain the readings . I assume you get the readings while running on the Dino. Is their any other way to get good readings for those of us that don't have a Dino.

David

You will need to find a way to run the engine on a test bench with a load (propeller) that gives approximately the same rpm as when running in the water.

Jim

 

[Sean Bowf]

I wonder if someone makes a pressure gauge that has a "max pressure" needle that stays at max pressure until reset... Then it could be run in the boat and checked after the run.

Just an idea.

Sean

 

[camaroboy383]

and a good idea sean,,,need some kinda schrader valve,,, just like a compression gauge...

alden

 

[glenng]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

Good topic, Jim -how are you measuring volume? I used to have a nice glass burrette but gave it away when I quit playing around with cylinder heads. I do still have a hydrometer I can fill and measure and calculate volume using algebra and convert C.I. to cc's.

Thanks,

Glenn

 

[Jim Allen]

If I change pipes on an engine to one that has a larger volume, or smaller volume, is there a general rule of thumb about pipe length?? From what one person said, I am understanding that a smaller volume needs a longer length, but don't know if this works, if I am over thinking what he said, or if length has no relation to volume at all.

Just trying to save some time when trying different pipes.

Thanks in advance for your input,

Sean

Sean,

Dyno testing of pipes for .40 to .90 size engines indicate that pipe volumes should be 25 to 30 times engine displacement. This allows the use of longer, smaller diameter stingers. The end results are pipe pressures in excess of 100 inches of water at WOT. Most stock pipes tested would only produce 80 inches of water. Pipe pressures can easily be tested with a Wika type gage that reads 0 to 200 inches of water. Higher pipe pressures give a greater boast, higher HP & more Heat.

Jim Allen

Good topic, Jim -how are you measuring volume? I used to have a nice glass burrette but gave it away when I quit playing around with cylinder heads. I do still have a hydrometer I can fill and measure and calculate volume using algebra and convert C.I. to cc's.

Thanks,

Glenn

I place a small rubber plug in the stinger & fill the entire pipe including the header with alcohol. Carefully pour this into a graduated cylinder. With new pipes I'm building, the volume is calculated mathematically during the design phase.

Head volumes are also calculated mathematically because of the surface tension problem that exists when using liquids.

Jim