how to choose the right pipe and header
01-01-2009, 08:49 PM
#1
how to choose the right pipe and header
Hey guys, I'm not really a big fan of buying and not getting what I was hoping for. I know that the right pipe can take a engine and totally change what you get.
Mostly, I have been looking for a pipe that gives the low end boost. So I go buy others experience or what the manufactures say. But I am still a bit confused about the headers. Short is better for high end, and long is better for low end right? So whats the deal with a "C" shaped versus a "L" shaped header ????
Mostly, I have been looking for a pipe that gives the low end boost. So I go buy others experience or what the manufactures say. But I am still a bit confused about the headers. Short is better for high end, and long is better for low end right? So whats the deal with a "C" shaped versus a "L" shaped header ????
01-01-2009, 09:55 PM
#4
Hey guys, I'm not really a big fan of buying and not getting what I was hoping for. I know that the right pipe can take a engine and totally change what you get.
Mostly, I have been looking for a pipe that gives the low end boost. So I go buy others experience or what the manufactures say. But I am still a bit confused about the headers. Short is better for high end, and long is better for low end right? So whats the deal with a "C" shaped versus a "L" shaped header ????
Mostly, I have been looking for a pipe that gives the low end boost. So I go buy others experience or what the manufactures say. But I am still a bit confused about the headers. Short is better for high end, and long is better for low end right? So whats the deal with a "C" shaped versus a "L" shaped header ????
Regarding C vs L bend, waves like the smooth bend of the C-shape, not abrupt changes in direction you get from an L-bend.
Read on...
chunk t
...Like I said earlier, the engine is a pump & wave generator
...the first port to be exposed is the exhaust port. Depending on when & how long this port remains open, and the RPM range you want the tuned exhaust to "come on", will affect the header and pipe lengths
...When the piston lowers enough to expose the next set of ports –the transfer and boost ports- the expanding wave of pressure in the cylinder will have blown through the end of the header.
...When the piston completes it's journey to the bottom of the stroke the crank case and combustion chamber pressures will have equalized and the fresh fuel/air mixture will have forced most of the burnt gasses out of the cylinder and into the header, but not all of the burnt gasses. (This is when the header goes to work.)
-THE HEADER… when the exhaust port opens the gasses will rush into the header as a pressure wave attempting to equalize the pressure between the cylinder & the header. This wave will travel though the header until it reaches the divergent cone; the beginning of the pipe (narrow to large cone). Make note, that as the pipe’s diameter increases, the volume is increasing as well. This increase in volume generates a negative (low pressure) wave and sends it back to the engine. The negative header wave will return to the cylinder and scavenge (suck) the remaining burnt gasses out of the combustion chamber. The abruptness of the change in volume by the divergent cone will affect how strong the pipe comes on and how broad of a power band will be available. Depending on timing and volumetric change of the divergent cone, the negative wave can be strong enough to fill about 20% of the header with FRESH fuel which can be “packed” back into the combustion chamber.-
-THE PIPE… While ALL of this has been going on, the wave that was generated when the exhaust port opened has now reached the convergent cone (big to little) at the end of the pipe and has been reflected back toward the engine. This returning positive pressure wave will pack the extra fuel from the header, back into the cylinder; providing a supercharger type of effect. If the wave arrives to soon, it blows through the cylinder and into the open transfer ports pressurizing the crank case, reducing the forcefulness of the induction (where I began the cycle). If it arrives too late, the piston will have sealed off the port and the wave will never have a chance to pack the extra fuel from the header.-
So how do you make your engine & pipe run their best???? You need to know your engine's timing specs, operating temp and desired RPM range to have the pipe "stage". This info can get you in the vacinity of where you want to be. Tweeking the length of the header/pipe coupler, plug temp and needle will need to be adjusted for the day's conditions...
01-01-2009, 10:21 PM
#6
where did this come from chunk ??? i like it . trial and error overcomes much of the math , volume , wave , scavenging effects , etc. , etc. . it is great info to keep in your head and use in attempting to properly choose the right combinations of exhaust header and pipe .
I've found a lot of companies to market their headers and pipes based on RPM range and leave it to the driver to choose what they think is best. I was PM'd by another poster & here is a portion of a PM I sent to them. I hope this helps you out.
Regarding C vs L bend, waves like the smooth bend of the C-shape, not abrupt changes in direction you get from an L-bend.
Read on...
chunk t
...Like I said earlier, the engine is a pump & wave generator
...the first port to be exposed is the exhaust port. Depending on when & how long this port remains open, and the RPM range you want the tuned exhaust to "come on", will affect the header and pipe lengths
...When the piston lowers enough to expose the next set of ports –the transfer and boost ports- the expanding wave of pressure in the cylinder will have blown through the end of the header.
...When the piston completes it's journey to the bottom of the stroke the crank case and combustion chamber pressures will have equalized and the fresh fuel/air mixture will have forced most of the burnt gasses out of the cylinder and into the header, but not all of the burnt gasses. (This is when the header goes to work.)
-THE HEADER… when the exhaust port opens the gasses will rush into the header as a pressure wave attempting to equalize the pressure between the cylinder & the header. This wave will travel though the header until it reaches the divergent cone; the beginning of the pipe (narrow to large cone). Make note, that as the pipe’s diameter increases, the volume is increasing as well. This increase in volume generates a negative (low pressure) wave and sends it back to the engine. The negative header wave will return to the cylinder and scavenge (suck) the remaining burnt gasses out of the combustion chamber. The abruptness of the change in volume by the divergent cone will affect how strong the pipe comes on and how broad of a power band will be available. Depending on timing and volumetric change of the divergent cone, the negative wave can be strong enough to fill about 20% of the header with FRESH fuel which can be “packed” back into the combustion chamber.-
-THE PIPE… While ALL of this has been going on, the wave that was generated when the exhaust port opened has now reached the convergent cone (big to little) at the end of the pipe and has been reflected back toward the engine. This returning positive pressure wave will pack the extra fuel from the header, back into the cylinder; providing a supercharger type of effect. If the wave arrives to soon, it blows through the cylinder and into the open transfer ports pressurizing the crank case, reducing the forcefulness of the induction (where I began the cycle). If it arrives too late, the piston will have sealed off the port and the wave will never have a chance to pack the extra fuel from the header.-
So how do you make your engine & pipe run their best???? You need to know your engine's timing specs, operating temp and desired RPM range to have the pipe "stage". This info can get you in the vacinity of where you want to be. Tweeking the length of the header/pipe coupler, plug temp and needle will need to be adjusted for the day's conditions...
Regarding C vs L bend, waves like the smooth bend of the C-shape, not abrupt changes in direction you get from an L-bend.
Read on...
chunk t
...Like I said earlier, the engine is a pump & wave generator
...the first port to be exposed is the exhaust port. Depending on when & how long this port remains open, and the RPM range you want the tuned exhaust to "come on", will affect the header and pipe lengths
...When the piston lowers enough to expose the next set of ports –the transfer and boost ports- the expanding wave of pressure in the cylinder will have blown through the end of the header.
...When the piston completes it's journey to the bottom of the stroke the crank case and combustion chamber pressures will have equalized and the fresh fuel/air mixture will have forced most of the burnt gasses out of the cylinder and into the header, but not all of the burnt gasses. (This is when the header goes to work.)
-THE HEADER… when the exhaust port opens the gasses will rush into the header as a pressure wave attempting to equalize the pressure between the cylinder & the header. This wave will travel though the header until it reaches the divergent cone; the beginning of the pipe (narrow to large cone). Make note, that as the pipe’s diameter increases, the volume is increasing as well. This increase in volume generates a negative (low pressure) wave and sends it back to the engine. The negative header wave will return to the cylinder and scavenge (suck) the remaining burnt gasses out of the combustion chamber. The abruptness of the change in volume by the divergent cone will affect how strong the pipe comes on and how broad of a power band will be available. Depending on timing and volumetric change of the divergent cone, the negative wave can be strong enough to fill about 20% of the header with FRESH fuel which can be “packed” back into the combustion chamber.-
-THE PIPE… While ALL of this has been going on, the wave that was generated when the exhaust port opened has now reached the convergent cone (big to little) at the end of the pipe and has been reflected back toward the engine. This returning positive pressure wave will pack the extra fuel from the header, back into the cylinder; providing a supercharger type of effect. If the wave arrives to soon, it blows through the cylinder and into the open transfer ports pressurizing the crank case, reducing the forcefulness of the induction (where I began the cycle). If it arrives too late, the piston will have sealed off the port and the wave will never have a chance to pack the extra fuel from the header.-
So how do you make your engine & pipe run their best???? You need to know your engine's timing specs, operating temp and desired RPM range to have the pipe "stage". This info can get you in the vacinity of where you want to be. Tweeking the length of the header/pipe coupler, plug temp and needle will need to be adjusted for the day's conditions...
01-02-2009, 08:11 PM
#8
Houston, thanks.
Everyone may enjoy this link, it has pictures that match up with what I posted
http://www.vf750fd.com/blurbs/stroke.html
later,
Everyone may enjoy this link, it has pictures that match up with what I posted
http://www.vf750fd.com/blurbs/stroke.html
later,
puts an even more refined perspective on it though
01-03-2009, 06:50 AM
#11
Chuck, I posted your link in another forum. I also gave mention of your name as the provider. Hope you don't mind. Your info is right on the money and very useful.
01-03-2009, 11:10 AM
#12
Monty... if you do a search for tuned pipes you won't find the article. I stumbled across it when I was GOOGLING 2-cycle port shapes. 
go figure.
Greg... anything I post is free for the taking ...or ignoring
Tigger... I pipe an engine to match the engine's design. Some engines are laid out for RPM, some are laid out for low end grunt. THIS POINT ON IS ONLY MY OPINION... I try to enhance the engine's strengths rather than build up a short coming. If you find that your engine just doesn't deliver what you want for your track... you're running the wrong engine more so than the wrong pipe set-up. On my 2wd trucks I like to run an engine set up for RPM with a weak low end. My truck is light and can spin the wheels real easy if the engine has too much low end grunt. But then again, I may just favor this set-up 'cause I suck as a driver
go figure.
Greg... anything I post is free for the taking ...or ignoring
Tigger... I pipe an engine to match the engine's design. Some engines are laid out for RPM, some are laid out for low end grunt. THIS POINT ON IS ONLY MY OPINION... I try to enhance the engine's strengths rather than build up a short coming. If you find that your engine just doesn't deliver what you want for your track... you're running the wrong engine more so than the wrong pipe set-up. On my 2wd trucks I like to run an engine set up for RPM with a weak low end. My truck is light and can spin the wheels real easy if the engine has too much low end grunt. But then again, I may just favor this set-up 'cause I suck as a driver
01-03-2009, 12:25 PM
#13
Great info and post. Really good stuff going on there.
To hit your question... The OS engines had the OS 2050 and 2060 pipes designed for them. Luck has it that Losi did a smart thing. Their new RE-11 pipe is a clone of the OS 2050 that is was discontinued. They reinforced the stinger, made the nipple welded and facing forward and improved the coating significantly. They include it with a good header and mount hardware for $65. Smoking good pipe that makes great power without loosing run time.
I do run it on my VSpecs and have measured it for myself to make sure.
If not this then JP-4 or the OS pipes are your best bet. EB Mods makes one as well.
Good luck.
TEX
To hit your question... The OS engines had the OS 2050 and 2060 pipes designed for them. Luck has it that Losi did a smart thing. Their new RE-11 pipe is a clone of the OS 2050 that is was discontinued. They reinforced the stinger, made the nipple welded and facing forward and improved the coating significantly. They include it with a good header and mount hardware for $65. Smoking good pipe that makes great power without loosing run time.
I do run it on my VSpecs and have measured it for myself to make sure.
If not this then JP-4 or the OS pipes are your best bet. EB Mods makes one as well.
Good luck.
TEX
01-03-2009, 07:55 PM
#14
hey tex after reading your post about the losi pipe being a 2050 clone i had to check man i missed that one nice find, my 2050 is in pretty bad shape time for a new pipe
