exhaust cutouts
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From: Powder Springs, GA
exhaust cutouts
Anyone know where to get some good quality cutouts that will fit our stock exhaust piping? I've found some wing nut style ones in some caalogs but I really want the cable-controlled ones. Thanks!!
Jeff
Jeff
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From: Bay Area, California
every readily available cut out that i have seen that is controlled by a cable is too small for our piping. i think the biggest is 2 1/4". but if you dont want to get under the truck every time you want open the cutouts, there are electric ones that will fit. They are adjustable with a ****. Unfortunatly I cant find the web site where there at but if you do an internet search you may come up with something...that how i found them.
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From: Atlanta, Ga
The electric one is the mccord powerplate 2. I have one coming. i think the site is like http://www.mccordcg.com/mpp/mpp.htm
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From: Arizona
I was the one who installed the cutouts
I have JBA headers and then had a straight pipe run about 4-5in then put on the summit cutouts 2.5in. Hey everyone is whinning (you'll lose power) yes this is true, however, Im still working at it. If i can figure out the the fricken flow momentums out of my headers i might beable to fix the problem to an extent. I was racing tonight and i ran my best time with my cutouts open. you just have to launch from a MUCH higher RPM to make-up for the lowend toque lose because of insufficent back pressure (now for a quick talk about the mysteries of back pressure for those of you whom dont know exactly what it is (WARNING I DONT KNOW EITHER, this is all from what i know about dynamic flow through a tube.) If you dont care about back pressure I will tell you that i am not upset with my cutouts. I LOVE THEM. If im at a car show and some ricers start revving their engines with that crack a$$ soundsing muffler... i just get under my truck and about 2min later BLOW THEIR FRICKING MINDS..... on to exhaust theory
When dealing with flow in pipes the most important thing to try to understand is the idea of momentum of the air (also called inertia). Newton's laws tell a great story that I'm not going to make you read. First think of air sitting still in a tube. It is nice and happy. The pressure of this air is @ 1atm (atmosphere). THere is no force pulling the air in any direction. Think of what happens to that air when we push a little air in one end (the exhaust valve opening). All the air is pushed out the other end. As the air is pushed it gains momentum due to it's mass and now incressing velocity. That air (assuming that nothing is interupting it) would just keep on moving forever because of its aquired energy. But that is not the case here. There are two, general, forces acting on this flow of air.
One is the outside pressure (ambiant) of the air pushing on this outflowing air. It is pushing back on this air because the exiting gas wants to expand (it's at a higher velosity and the other air will push against it to establish equalibrium (kind of like a big pressure wave)).
The second force is the lack of air behind this moving flow when the exhaust valve closes. This lack of air wants to pull the moving air back to fill the void (the same forces that make the air want to go out the end of the pipe (high and low pressures) want to also pull some back in. That is the basics of what air wants to do.
Now lets look at what goes on in a stock exhaust. Then in my exhaust. And maybe if I dont pass out at my keep board Ill tell you how i plan on fixing it.
For the standard exhaust on our L's there are the progressive cast iron heads (progressive because each cylinder's outlet adds to the next (if you dont know what i mean go and look at them it will become clear). Note that there is very little increase in exhaust diameter per outlet, also notice the rear sweeping flow shape of each head. Shortly down the line there are the evil cats and then and other cat and etc... Now back to what happens at each stage (again I am not certain) Now say the cylinder closest to the front of the engine opens. I'm going to avoid general turbulance, scattering, and thermal issues for sake of time. That "shot" of moving air heads down the heads and loses just a little momentum to each of the heads it passes because it creates that same vacuum that I discused before. So by the time it reaches the first cat it will have some movement but not enough to force its way through the cats. Now notice what happens to that burst of moving air.... it's stopped dead in its track because it lost all inertia to the tiny foulings from the other heads. That is a good thing for torque because the next shot will experience the same thing. It will be allowed to expand into a pressure of aproximately 1atm. Since it's velocity can over come that 1atm with ease the flow is pushed out and comes to a stop.
As the shots continue to occure each mass of air pushes the one before it just a little (equal to it's displacement of volume) This again is good for torque because torque has to do with the raw power of the engine, yet it's not so good for HP because HP is basicly (please correct me if im in error) the engine's ability to turn the wheels really fast, the idea being that the less restriction the more HP. That is why removing restrictions will gain HP but not nessisarilly torque (ill explain why in a moment). The reason that HP can be gainned by removing restrictions the highers RPMs (where HP is at its greatest) can occur with less effort because the air's momentum it fast moving and with fewer restrictions that air can move without clogging exhaust gasses behind itself.
Now for the reasons why freeing up exhaust (esp to the point of cutouts 15" from the nearest cylinder as i have done) can cause a serious loss in toque if not couped with.
Now imagin that same flow of air going through a set of JBA headers. Each pulse goes down a long tube and then into an open chamber, then down a large pipe and right out into the 1atm. Each shot is not given sufficent restriction to slow down. IE it has alot of momentum and just tares ***** out of the whole system. At low end (where all the toque is) the entire trip out the end of the pipe can happen in less time than the next cylinder can open. Now with this blast of fast moving air that loses little momentum by the time it exits, can create a huge vaccuum. Now the result of the ambiant 1atm is to fill that vaccuum. So air goes rushing back up in the system. Note: all moving air takes power to move... esp if it's heading the WRONG way. Now as the next exhaust valve opens it is met, or shortly after is met, by a rushing flow of dense (it's cold so it's "heavier" air) heading the wrong way.... now this new haust gas can't push that on its own so it has to rely on the power of the piston behind it to even get the air moving the other way.... you can see why that's bad i hope.
Now the reason that this is not so much a problem on the top end (HP) is that the shots are much much closer together. So there is no time for the air to rush back up in and even if it did there would be 2-3 shots worth of high pressure air right there to kick it out of the way (plus the aerodynamics of the open face pointing away from the flow of the ambiant air would almost cause a sucking effect but it's a real mess underthere) So with ZERO restriction the air just goes right out. Now im sure that there is a better way probly involving the use of turbulance or high restirction but i work on things in vaccuums and high speed aircraft. Not cars.
Now after that total mess that I have created with that exhaust system here's how I am planning on fixing it.
Taking a break................. why did i type that?
Now the general idea to fix this is that i must find a way to break up the air flow. Not clog mind you (cats (not the animal), steel wool or anything like that). But something that will simulate the little pockets that the stock heads created. I need something that the fast air will run over and create just a tiny vaccuum large enough to throw the whole shot into a tumble and thereby disipate all its momentum onto itself and cause the whole mass to just stop (for the most part). This would have to be near the headers because the sooner the better because there will be less of a big vaccuum to deal with. So in the header's collection "cup" im going to put something (ill post a drawing later) that would be smooth at first but then will have many suddend gaps that would cause almost a "pop" to occur when the air tires to fill it and slams into the bottom of the pocket.
Another way to try and fix this (or take advantage) is launch from a much higher RPM. I tried launching from 1900 tonight and got very good results (compared to having my cutouts closed) with the high flow cats there is still a "back draft" effect but not nearly as bad. So either way ill have to put the "Diode" in there on my own. This diode is already (or i at least hope it is) in the long tube headers. If you look at the top fuel and alcohol funny cars and at their headers they all come together into a can looking thing. In that large can is where the diode is placed (in the middle of the four pipes) and the large chamber allows for the air to sit long enough to create the back pressure and then it is open enough (notice the nozzle shape to maintain back pressure) to allow the next shot to just throw out the slow air.....
I hope this helps alot of the exuhaustly confused people out there. If there is anything wrong with this please just post it and ill make corrections later.
Thank you again
Mark
When dealing with flow in pipes the most important thing to try to understand is the idea of momentum of the air (also called inertia). Newton's laws tell a great story that I'm not going to make you read. First think of air sitting still in a tube. It is nice and happy. The pressure of this air is @ 1atm (atmosphere). THere is no force pulling the air in any direction. Think of what happens to that air when we push a little air in one end (the exhaust valve opening). All the air is pushed out the other end. As the air is pushed it gains momentum due to it's mass and now incressing velocity. That air (assuming that nothing is interupting it) would just keep on moving forever because of its aquired energy. But that is not the case here. There are two, general, forces acting on this flow of air.
One is the outside pressure (ambiant) of the air pushing on this outflowing air. It is pushing back on this air because the exiting gas wants to expand (it's at a higher velosity and the other air will push against it to establish equalibrium (kind of like a big pressure wave)).
The second force is the lack of air behind this moving flow when the exhaust valve closes. This lack of air wants to pull the moving air back to fill the void (the same forces that make the air want to go out the end of the pipe (high and low pressures) want to also pull some back in. That is the basics of what air wants to do.
Now lets look at what goes on in a stock exhaust. Then in my exhaust. And maybe if I dont pass out at my keep board Ill tell you how i plan on fixing it.
For the standard exhaust on our L's there are the progressive cast iron heads (progressive because each cylinder's outlet adds to the next (if you dont know what i mean go and look at them it will become clear). Note that there is very little increase in exhaust diameter per outlet, also notice the rear sweeping flow shape of each head. Shortly down the line there are the evil cats and then and other cat and etc... Now back to what happens at each stage (again I am not certain) Now say the cylinder closest to the front of the engine opens. I'm going to avoid general turbulance, scattering, and thermal issues for sake of time. That "shot" of moving air heads down the heads and loses just a little momentum to each of the heads it passes because it creates that same vacuum that I discused before. So by the time it reaches the first cat it will have some movement but not enough to force its way through the cats. Now notice what happens to that burst of moving air.... it's stopped dead in its track because it lost all inertia to the tiny foulings from the other heads. That is a good thing for torque because the next shot will experience the same thing. It will be allowed to expand into a pressure of aproximately 1atm. Since it's velocity can over come that 1atm with ease the flow is pushed out and comes to a stop.
As the shots continue to occure each mass of air pushes the one before it just a little (equal to it's displacement of volume) This again is good for torque because torque has to do with the raw power of the engine, yet it's not so good for HP because HP is basicly (please correct me if im in error) the engine's ability to turn the wheels really fast, the idea being that the less restriction the more HP. That is why removing restrictions will gain HP but not nessisarilly torque (ill explain why in a moment). The reason that HP can be gainned by removing restrictions the highers RPMs (where HP is at its greatest) can occur with less effort because the air's momentum it fast moving and with fewer restrictions that air can move without clogging exhaust gasses behind itself.
Now for the reasons why freeing up exhaust (esp to the point of cutouts 15" from the nearest cylinder as i have done) can cause a serious loss in toque if not couped with.
Now imagin that same flow of air going through a set of JBA headers. Each pulse goes down a long tube and then into an open chamber, then down a large pipe and right out into the 1atm. Each shot is not given sufficent restriction to slow down. IE it has alot of momentum and just tares ***** out of the whole system. At low end (where all the toque is) the entire trip out the end of the pipe can happen in less time than the next cylinder can open. Now with this blast of fast moving air that loses little momentum by the time it exits, can create a huge vaccuum. Now the result of the ambiant 1atm is to fill that vaccuum. So air goes rushing back up in the system. Note: all moving air takes power to move... esp if it's heading the WRONG way. Now as the next exhaust valve opens it is met, or shortly after is met, by a rushing flow of dense (it's cold so it's "heavier" air) heading the wrong way.... now this new haust gas can't push that on its own so it has to rely on the power of the piston behind it to even get the air moving the other way.... you can see why that's bad i hope.
Now the reason that this is not so much a problem on the top end (HP) is that the shots are much much closer together. So there is no time for the air to rush back up in and even if it did there would be 2-3 shots worth of high pressure air right there to kick it out of the way (plus the aerodynamics of the open face pointing away from the flow of the ambiant air would almost cause a sucking effect but it's a real mess underthere) So with ZERO restriction the air just goes right out. Now im sure that there is a better way probly involving the use of turbulance or high restirction but i work on things in vaccuums and high speed aircraft. Not cars.
Now after that total mess that I have created with that exhaust system here's how I am planning on fixing it.
Taking a break................. why did i type that?
Now the general idea to fix this is that i must find a way to break up the air flow. Not clog mind you (cats (not the animal), steel wool or anything like that). But something that will simulate the little pockets that the stock heads created. I need something that the fast air will run over and create just a tiny vaccuum large enough to throw the whole shot into a tumble and thereby disipate all its momentum onto itself and cause the whole mass to just stop (for the most part). This would have to be near the headers because the sooner the better because there will be less of a big vaccuum to deal with. So in the header's collection "cup" im going to put something (ill post a drawing later) that would be smooth at first but then will have many suddend gaps that would cause almost a "pop" to occur when the air tires to fill it and slams into the bottom of the pocket.
Another way to try and fix this (or take advantage) is launch from a much higher RPM. I tried launching from 1900 tonight and got very good results (compared to having my cutouts closed) with the high flow cats there is still a "back draft" effect but not nearly as bad. So either way ill have to put the "Diode" in there on my own. This diode is already (or i at least hope it is) in the long tube headers. If you look at the top fuel and alcohol funny cars and at their headers they all come together into a can looking thing. In that large can is where the diode is placed (in the middle of the four pipes) and the large chamber allows for the air to sit long enough to create the back pressure and then it is open enough (notice the nozzle shape to maintain back pressure) to allow the next shot to just throw out the slow air.....
I hope this helps alot of the exuhaustly confused people out there. If there is anything wrong with this please just post it and ill make corrections later.
Thank you again
Mark
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Joined: Oct 2001
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From: Powder Springs, GA
Dang Mark, now that's an explanation
Btw, what kind of exhaust are you running when you don't have the cutouts open and have you tried/have an x-pipe? Thanks!
--Jeff
Btw, what kind of exhaust are you running when you don't have the cutouts open and have you tried/have an x-pipe? Thanks!--Jeff
Last edited by JLightning; Feb 28, 2002 at 12:31 PM.
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Joined: Sep 2001
Posts: 180
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From: louisville-Ky
i have cutouts before my magnaflow.
open they are louds as hell @ WOT.
my truck is a daily driver and they are capped off because it will gave you a headache after a while
and if you go through a drive through you have to shut the truck down.
open they are louds as hell @ WOT.
my truck is a daily driver and they are capped off because it will gave you a headache after a while
and if you go through a drive through you have to shut the truck down.
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Joined: Oct 2001
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From: Powder Springs, GA
hey kylightning, what kinda magnflow are you running? I'm pretty much set on doing a setup like yours, I want something with a nice smooth rumble fo daily driving, but freakin mean and loud as hell when I want. I'm considerig the 12468, seems like the best compromise...
--Jeff
--Jeff
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Joined: Sep 2001
Posts: 180
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From: louisville-Ky
jlightning-
i have a 12468. i like the sound and it is good for daily driving.
one day i will have some long tube headers and replace the cutouts with a x pipe, but i want to hear
them in person first.
i ordered my cut outs from summit 2.5inch about $26 each
good luck
kevin
i have a 12468. i like the sound and it is good for daily driving.
one day i will have some long tube headers and replace the cutouts with a x pipe, but i want to hear
them in person first.
i ordered my cut outs from summit 2.5inch about $26 each
good luck
kevin
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Joined: Feb 2002
Posts: 195
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From: Cincinnati
Wow - sounds like the Spade man had the marble rolling around pretty fast....
Understood the exhaust issues perfectly... now, how about this idea.
A one way valve...
so if air (exhaust) travels right to left (front to back) and goes through a one way valve, it cannot get 'sucked' back toward the engine because the air movement the opposite direction would close the 'flap'
I've made an illustration... go ahead and laugh, but I think it shows what I'm trying to state - why doesn't someone make one of these?? <see attached file>
Email me if you want to brain storm...
Peace,
the John
hotelishome@onebox.com
Understood the exhaust issues perfectly... now, how about this idea.
A one way valve...
so if air (exhaust) travels right to left (front to back) and goes through a one way valve, it cannot get 'sucked' back toward the engine because the air movement the opposite direction would close the 'flap'
I've made an illustration... go ahead and laugh, but I think it shows what I'm trying to state - why doesn't someone make one of these?? <see attached file>
Email me if you want to brain storm...
Peace,
the John
hotelishome@onebox.com
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Joined: Jul 2001
Posts: 286
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From: Arizona
PWR wheels,
THat's a good idea however there are many draw backs to the idea. Everything built, cars trucks, engine, even legos will someday break. It's called a fatigue test and a metal flap that opens and closes with the momentum of hte air will break rapidly. In theory that's a good idea (can't say that the idea had even occured me me
) but something that large would not be able to open and close fast enough even if you were to shape the valves like the valves in your heart (3 little things opening and closing) But I like it. Give it some thought you might be onto something. However in time that will break none the less. The little diode thing is just a stationary object that will barely effect the HP and will slow the air for the torque...
THat's a good idea however there are many draw backs to the idea. Everything built, cars trucks, engine, even legos will someday break. It's called a fatigue test and a metal flap that opens and closes with the momentum of hte air will break rapidly. In theory that's a good idea (can't say that the idea had even occured me me
) but something that large would not be able to open and close fast enough even if you were to shape the valves like the valves in your heart (3 little things opening and closing) But I like it. Give it some thought you might be onto something. However in time that will break none the less. The little diode thing is just a stationary object that will barely effect the HP and will slow the air for the torque...
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Joined: Jul 2001
Posts: 286
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From: Arizona
https://www.f150online.com/forums/sh...threadid=62089
there's a bunch of pics of my exhaust now
to the web master... i sure am glad that i was able to search for that... bc otherwise it would have taken me about 30min just to find the post
there's a bunch of pics of my exhaust now
to the web master... i sure am glad that i was able to search for that... bc otherwise it would have taken me about 30min just to find the post