The Truth Behind Quad Setups. Seperating Fact and Fiction.
05-17-2010, 11:51 AM
#21
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My Ride: A Car faster than yours.....
I know everyone here states that quad setups will lose horsepower and based on common knowledge of exhaust system backpressure, I can understand how you'd lose low-end power, which everyone talks about, however how about the top-end? In theory wouldn't the quad setup provide better top-end performance than a more restrictive single-sided exhaust system with higher backpressure? Does anyone have empirical data to support that a quad setup would indeed impair performance throughout the entire power band?
Also, couldn't one achieve the same or close to stock backpressure by using different exhaust tube diameters and lengths to create the backpressure needed to retain low-end performance? It just seems that it is quite a bold statement to say that with any quad setup, you'll lose power. Personally it sounds like there just hasn't been a quad setup that has been developed correctly, unless of course we have data to support these claims.
Anyone?
I am looking to do a quad setup soon so I'd really like to hear what efforts have been made to prove that a quad setup will indeed impair performance. And please don't post "Butt Dyno" results, as there are so many various conditions that can play a role in how your engine performs between not having quads and having quads.
Looking forward to hearing from the crowd!
Also, couldn't one achieve the same or close to stock backpressure by using different exhaust tube diameters and lengths to create the backpressure needed to retain low-end performance? It just seems that it is quite a bold statement to say that with any quad setup, you'll lose power. Personally it sounds like there just hasn't been a quad setup that has been developed correctly, unless of course we have data to support these claims.
Anyone?
I am looking to do a quad setup soon so I'd really like to hear what efforts have been made to prove that a quad setup will indeed impair performance. And please don't post "Butt Dyno" results, as there are so many various conditions that can play a role in how your engine performs between not having quads and having quads.
Looking forward to hearing from the crowd!
Can you explain what backpressure is and if there is even such a thing?
05-17-2010, 11:54 AM
#23
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would either of these mufflers:
http://cgi.ebay.com/ebaymotors/Magna...Q5fAccessories
http://cgi.ebay.com/ebaymotors/Magna...Q5fAccessories
work with these tips:
http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT
and the shop can do the rest
http://cgi.ebay.com/ebaymotors/Magna...Q5fAccessories
http://cgi.ebay.com/ebaymotors/Magna...Q5fAccessories
work with these tips:
http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT
and the shop can do the rest
05-17-2010, 12:03 PM
#24
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The two resonators are actually your cats if I remember correctly - they just look like resonators. Man I wish I still had the pics from our 545i build.
The 10425 is a 2.25" resonator. You should be running 3.0". That muffler is going to be an odd fit as well.
You should have them reverse merge into 3.0" from the factory 2.5" and then run a a single 3" resonator and 3" high-flow cat a magnaflow muffler.
The 10425 is a 2.25" resonator. You should be running 3.0". That muffler is going to be an odd fit as well.
You should have them reverse merge into 3.0" from the factory 2.5" and then run a a single 3" resonator and 3" high-flow cat a magnaflow muffler.
The parts they are installing are as follows:
1 Magnaflow Muffler part number 11385
2 Magnaflow Mufflers part number 10425
The shop has been guided to leave the Exhaust manifold(integrated cats) and two resonators alone. Everything after the resonators will be replaced. Each of the two resonators will run into one inlet of a dual-inlet, dual-outlet Muffler (11385) which contains an internal crossover pipe. Each outlet of the 11385 will run into one of the two 10425 Magnapacks, then out to the bumper where they will terminate with dual tips. The stock pipe diameter leaving the two resonators will be used throughout. All pipes are not stainless, but they will be using mandrel bends.
Here are a couple videos:
Pull1:
http://www.youtube.com/watch?v=839-fGIiaBg
Pull2:
http://www.youtube.com/watch?v=mgYJ9VEHj_A
1 Magnaflow Muffler part number 11385
2 Magnaflow Mufflers part number 10425
The shop has been guided to leave the Exhaust manifold(integrated cats) and two resonators alone. Everything after the resonators will be replaced. Each of the two resonators will run into one inlet of a dual-inlet, dual-outlet Muffler (11385) which contains an internal crossover pipe. Each outlet of the 11385 will run into one of the two 10425 Magnapacks, then out to the bumper where they will terminate with dual tips. The stock pipe diameter leaving the two resonators will be used throughout. All pipes are not stainless, but they will be using mandrel bends.
Here are a couple videos:
Pull1:
http://www.youtube.com/watch?v=839-fGIiaBg
Pull2:
http://www.youtube.com/watch?v=mgYJ9VEHj_A
05-17-2010, 12:24 PM
#25
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a quad exhaust can be made to produce power. the only problem is the R&D. after all is said and done i doubt most of you guys will be willing to pay for a power producing quad exhaust $$$$.
05-17-2010, 12:56 PM
#26
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My Ride: A Car faster than yours.....
The two resonators are actually your cats if I remember correctly - they just look like resonators. Man I wish I still had the pics from our 545i build.
The 10425 is a 2.25" resonator. You should be running 3.0". That muffler is going to be an odd fit as well.
You should have them reverse merge into 3.0" from the factory 2.5" and then run a a single 3" resonator and 3" high-flow cat a magnaflow muffler.
The 10425 is a 2.25" resonator. You should be running 3.0". That muffler is going to be an odd fit as well.
You should have them reverse merge into 3.0" from the factory 2.5" and then run a a single 3" resonator and 3" high-flow cat a magnaflow muffler.
BTW, the 545 has two 2-2.25" tubes going into a single 3". The 550 has a similar going into 3.25" tubing to the muffler.
In the end, why not just get an M5 if you want a car that was made to have a quad exhaust? you can pick them up at bargain prices since the resale value blows.
05-17-2010, 02:58 PM
#29
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Velocity of fluid (gas or liquid) in pipe is inversely proportionate to the square of the exhaust diameter. You've got exhaust gas spewed from a (i forget the actual number) but a 1-2 inch exhaust port, which then hits a 2 1/4 header pipe. The 'step' from 1.5ish to 2.25 inches results in a change to a lower velocity; this change in velocity becomes a problem at higher RPM's where the larger cross-section can't make up for the lower velocity in terms of volume of exhaust moved and the gas builds up (backpressure). Now, imagine that a we use 2.5inch headers. The velocity difference is even greater, and now teh exhaust can't even get out of its own way at low-rpm because its'heading out of the port so much faster than teh speed with which it travels down the tube. At higher RPMs the larger cross-sectional area makes up for the reduced speed, allowing the exhaust to get out of the way(reduced backpressure).
Velocity is also inversely proportionate to the pressure exerted against the tube walls. This pressure can resul in turbulence, causing backpressure. The faster the stuff moves, the less rpessure it exerts on the walls. The lower the velocity, the greater the pressure. Thusa 2.25 inch exhaust as lower tube wall pressure than the 2.5 inch exhaust.
Each section dealt with a different 'cause' of backpressure. One effect predominates at lower RPM, while one predominates at higher RPMs. Exhaust velocity (or lack thereof) contributes to backpressure at lower speeds; this effect is seen by the lower TQ numbers of a 2.5 inch exhaust (lower velocity) at low rpms while the smaller exhaust had higher TQ numbers because it wasn't a RESTRICTION. In this case, the limiting factor was exhaust velocity; how fast it travels in teh tube versus out the port.
At higher RPM's the limiting factor isnt' port velocity but how much volume can be moved in a certain amount of time (total flow, cfm, lbs/hr, just liek a carb, or injectors, or a TB.) In this instance, teh lower voluem 2.25 inch pipe simply can't hold as much exhaust as the 2.5inch pipe, thus the smaller pipe exerts backpressure, a RESTRICTION.
So what results in HIGH RPM backpressure results in low RPM torque cuz there's no backpressure at low rpms
While LOW RPM backpressure makes high rpm breathign easier.
The exhaust that does better in iether situation is the one with the elast backpressure FOR THE SITUATION (RPM)
Velocity is also inversely proportionate to the pressure exerted against the tube walls. This pressure can resul in turbulence, causing backpressure. The faster the stuff moves, the less rpessure it exerts on the walls. The lower the velocity, the greater the pressure. Thusa 2.25 inch exhaust as lower tube wall pressure than the 2.5 inch exhaust.
Each section dealt with a different 'cause' of backpressure. One effect predominates at lower RPM, while one predominates at higher RPMs. Exhaust velocity (or lack thereof) contributes to backpressure at lower speeds; this effect is seen by the lower TQ numbers of a 2.5 inch exhaust (lower velocity) at low rpms while the smaller exhaust had higher TQ numbers because it wasn't a RESTRICTION. In this case, the limiting factor was exhaust velocity; how fast it travels in teh tube versus out the port.
At higher RPM's the limiting factor isnt' port velocity but how much volume can be moved in a certain amount of time (total flow, cfm, lbs/hr, just liek a carb, or injectors, or a TB.) In this instance, teh lower voluem 2.25 inch pipe simply can't hold as much exhaust as the 2.5inch pipe, thus the smaller pipe exerts backpressure, a RESTRICTION.
So what results in HIGH RPM backpressure results in low RPM torque cuz there's no backpressure at low rpms
While LOW RPM backpressure makes high rpm breathign easier.
The exhaust that does better in iether situation is the one with the elast backpressure FOR THE SITUATION (RPM)
05-17-2010, 03:08 PM
#30
Senior Members
Car on the lift:
Here are the resonators (I think crmb is calling these cats) where they cut the old exhaust and began tacking in the new one. The new piping is the same diameter as the old stuff:
Here you can see the center muffler which contains the internal crossover:
They did not finish the car today because they needed to order an exhaust hanger. As you can see this is the driver side hanger:
...and this is the current passenger side hanger (none- and it won't be here till tomorrow):
The two resonators are actually your cats if I remember correctly - they just look like resonators. Man I wish I still had the pics from our 545i build.
The 10425 is a 2.25" resonator. You should be running 3.0". That muffler is going to be an odd fit as well.
You should have them reverse merge into 3.0" from the factory 2.5" and then run a a single 3" resonator and 3" high-flow cat a magnaflow muffler.
The 10425 is a 2.25" resonator. You should be running 3.0". That muffler is going to be an odd fit as well.
You should have them reverse merge into 3.0" from the factory 2.5" and then run a a single 3" resonator and 3" high-flow cat a magnaflow muffler.
The 10425 has the same inlet diameter as the factory piping. No connection issues or need for size adapters.
