"Delete Loop" pipe safe for Pentestar?
08-10-2014, 04:27 PM
#11
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I went to a muffler shop to have my y-pipe crossover moved back to make more room for the front driveshaft to droop. This shop has been in business since the 70s and is the best in my area (okay, that's my opinion). When my rig was on the lift, I pointed out the loop to the owner. He said that was the stupidest design he has ever seen. I responded that it makes the right and left bank pipes equal length to control back pressure. He laughed. He said that if one side is moving faster than the other, the faster side will "draw" the slower side to equal pressure when it passes through the y-pipe and merges. He figures they put that there to control resonance (sound).
Take out of that what you will.
Take out of that what you will.
08-10-2014, 04:44 PM
#12
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08-10-2014, 04:53 PM
#13
JK Junkie
AFE makes a y-pipe that deletes it. Generally speaking, a well known exhaust company won't make a product that would have negative repercussions.
Note that the AFE pipe only works on a 4 door. Not only do the engineers have to make it work, but it has to be done at scale (meaning, for every wrangler model). There are alternatives.
Note that the AFE pipe only works on a 4 door. Not only do the engineers have to make it work, but it has to be done at scale (meaning, for every wrangler model). There are alternatives.
08-10-2014, 05:07 PM
#14
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I agree with the premiss that a motor is just a pump. Put in as much air and fuel as fast as possible,,, and get it out as fast as possible. It seems to me the "Tuned" exhaust is more applicable to a race motor where the HP output is stupid high, and squeezing out every last infinitesimal amount of power is the difference between winning and loosing. On our motor you may very well loose Maybe 1 HP by deleting the pipe loop, But you will not notice it, and you could easily get it back with less restrictive intake and muffler. Bottom line,,, the difference is negligible!
08-10-2014, 05:47 PM
#15
JK Super Freak
I went to a muffler shop to have my y-pipe crossover moved back to make more room for the front driveshaft to droop. This shop has been in business since the 70s and is the best in my area (okay, that's my opinion). When my rig was on the lift, I pointed out the loop to the owner. He said that was the stupidest design he has ever seen. I responded that it makes the right and left bank pipes equal length to control back pressure. He laughed. He said that if one side is moving faster than the other, the faster side will "draw" the slower side to equal pressure when it passes through the y-pipe and merges. He figures they put that there to control resonance (sound).
Take out of that what you will.
Take out of that what you will.
It's a timing thing, tuned headers and exhausts are tuned for optimal scavenging at specific RPMs where they assist in cylinder filling by drawing exhaust gasses out with a reduced back pressure pulse at the right time and point in the exhaust. You can tune different points by tuning different parts of the system to give a broader more balanced torque curve that is higher in many areas. Then you tune the intake to help. The OEM is looking for a flat torque curve with little or no dips in it, so yes you can get rid of the loop, but it will affect efficiency and may cost you power and increase fuel consumption. With a V6 firing every 120 degrees you have exhaust pulses coming pretty quick as RPM builds. Mess with the timing, exhaust pressure spikes will be felt at the valve at the wrong times and you are fighting to get the cylinder emptied and allow more clean air in for combustion.
08-10-2014, 11:43 PM
#16
I went to a muffler shop to have my y-pipe crossover moved back to make more room for the front driveshaft to droop. This shop has been in business since the 70s and is the best in my area (okay, that's my opinion). When my rig was on the lift, I pointed out the loop to the owner. He said that was the stupidest design he has ever seen. I responded that it makes the right and left bank pipes equal length to control back pressure. He laughed. He said that if one side is moving faster than the other, the faster side will "draw" the slower side to equal pressure when it passes through the y-pipe and merges. He figures they put that there to control resonance (sound).
Take out of that what you will.
Take out of that what you will.
Suction happens when the flow is fast enough, and the diameter of the pipe which is 'sucked from' is small enough at the connection between the pipes.
Link -- Venturi effect - Wikipedia, the free encyclopedia
The diameters of the the two exhaust pipes are similar, so there can be no suction.
Unequal pressures at the Y junction would create turbulence which slows the flow.
However, the effect on the power or torque spread over the r.p.m. may be too small to notice.
Last edited by GJeep; 08-10-2014 at 11:59 PM.
08-11-2014, 12:57 AM
#17
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**** it, just run straight pips up through your hood directly off the headers like semi stax, make sure you put flappers on top so when parked rain doesnt get in.
08-11-2014, 06:17 AM
#18
JK Junkie
I was just regurgitating. I am by no means an expert.
Just curious. Did your exhaust note get louder? That would support what the muffler shop said if so.
He didn't say it was there for nothing. He thinks it is there to quiet the exhaust note.
Both good points. I tend to agree with you.
If one side has more restrictions then theoretically it would move slower. I do know that bends can cause restrictions. Just look at any dryer exhaust instructions. They detail how many 90 degree turns can occur within a specific length before the exhaust fan can no longer overcome it. The exhaust loop is basically four 90 degree bends. If the exhaust ran down the passenger side instead of the drivers side I suspect the loop would be on the passenger side. Again, I'm not an expert and this is simply conjecture.
Edit: I did some reading on this and what I found was that the length of the pipes being equal allows the same tuning to be used on all cylinders. If the pipes are different lengths then each cylinder must be tuned separately. Based on that, I would not remove the loop.
AFE makes a y-pipe that deletes it. Generally speaking, a well known exhaust company won't make a product that would have negative repercussions.
Note that the AFE pipe only works on a 4 door. Not only do the engineers have to make it work, but it has to be done at scale (meaning, for every wrangler model). There are alternatives.
Note that the AFE pipe only works on a 4 door. Not only do the engineers have to make it work, but it has to be done at scale (meaning, for every wrangler model). There are alternatives.
If one side has more restrictions then theoretically it would move slower. I do know that bends can cause restrictions. Just look at any dryer exhaust instructions. They detail how many 90 degree turns can occur within a specific length before the exhaust fan can no longer overcome it. The exhaust loop is basically four 90 degree bends. If the exhaust ran down the passenger side instead of the drivers side I suspect the loop would be on the passenger side. Again, I'm not an expert and this is simply conjecture.
Edit: I did some reading on this and what I found was that the length of the pipes being equal allows the same tuning to be used on all cylinders. If the pipes are different lengths then each cylinder must be tuned separately. Based on that, I would not remove the loop.
Last edited by 14Sport; 08-11-2014 at 07:38 AM.
08-11-2014, 08:28 AM
#19
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It has nothing to do with pressure... It has to do with the pulses of the exhaust and timing them so that you dont create turbulence (as previously mentioned). Exhaust is not free flowing like water is in plumbing, it pulsates with each cylinder when it expends the exhaust out of the manifold. With each pulse comes a slight vaccuum which allows the engine to work less in order to expel the exhaust with the next pulse. If you create turbulence, the pulses will cause the exhaust to send negative pressure waves back up the pipe till it robs power from the engine (as it now has to work harder to overcome the exhaust pulses coming at it).
Now... in our engines, it is VERY slight as we are not high horsepower/high compression engines. You can remove the loop without really noticing any immediate affects but there will be a slight change and you should notice a small decrease in MPG. The reasons we have these loops is the engineers are tasked to create as much power, torque and fuel efficiency as possible and timing the exhaust pulses was worthwhile to them.
If we had the room, a straight double exhaust would be the best.
Now... in our engines, it is VERY slight as we are not high horsepower/high compression engines. You can remove the loop without really noticing any immediate affects but there will be a slight change and you should notice a small decrease in MPG. The reasons we have these loops is the engineers are tasked to create as much power, torque and fuel efficiency as possible and timing the exhaust pulses was worthwhile to them.
If we had the room, a straight double exhaust would be the best.
08-11-2014, 08:45 AM
#20
It has nothing to do with pressure... It has to do with the pulses of the exhaust and timing them so that you dont create turbulence (as previously mentioned). Exhaust is not free flowing like water is in plumbing, it pulsates with each cylinder when it expends the exhaust out of the manifold. With each pulse comes a slight vaccuum which allows the engine to work less in order to expel the exhaust with the next pulse. If you create turbulence, the pulses will cause the exhaust to send negative pressure waves back up the pipe till it robs power from the engine (as it now has to work harder to overcome the exhaust pulses coming at it). Now... in our engines, it is VERY slight as we are not high horsepower/high compression engines. You can remove the loop without really noticing any immediate affects but there will be a slight change and you should notice a small decrease in MPG. The reasons we have these loops is the engineers are tasked to create as much power, torque and fuel efficiency as possible and timing the exhaust pulses was worthwhile to them. If we had the room, a straight double exhaust would be the best.