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Discussion Starter #1
I took my car to a custom exhaust shop near my house for a suggestion and an estimate.

The owner of the shop is almost 60 years old and has been doing custom exhausts for about 40 years.

He had never seen an RL before so we put it up on the lift so he could have a gander. He LOVED how the exhaust was layed out. He said the only thing he'd do it is step up the last stretch of pipe right before the muffler (it's stepped down a bit from factory) and put a free flowing muffler on it (Magnaflow to be exact).

He said it was pretty damn good the way it is and it's a pretty straight forward exhaust system that didn't need much more.

The cost? He said a couple of hundred should be all for parts and labor and a 5 to 7 hp increase as well as bumping up the torque.

I don't know jack shit about exhaust systems but he's been in the biz a while and pretty much liked what he saw on the stock RL.
 

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JPK said:
I took my car to a custom exhaust shop near my house for a suggestion and an estimate.

The owner of the shop is almost 60 years old and has been doing custom exhausts for about 40 years.

He had never seen an RL before so we put it up on the lift so he could have a gander. He LOVED how the exhaust was layed out. He said the only thing he'd do it is step up the last stretch of pipe right before the muffler (it's stepped down a bit from factory) and put a free flowing muffler on it (Magnaflow to be exact).

He said it was pretty damn good the way it is and it's a pretty straight forward exhaust system that didn't need much more.

The cost? He said a couple of hundred should be all for parts and labor and a 5 to 7 hp increase as well as bumping up the torque.

I don't know jack shit about exhaust systems but he's been in the biz a while and pretty much liked what he saw on the stock RL.
This is good to know. The first, and most obvious thing to do right after we get our SCDYNE headers is to modify the rest of the exhaust system. I haven't gone to a shop to get an opinion yet, but will let everyone know when I do. Any word on how big the pipes might be that he will use? 3 inch? I have a friend telling me to go with three inches, but I don't know if that much is necessary.
 

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JPK said:
I took my car to a custom exhaust shop near my house for a suggestion and an estimate.

The owner of the shop is almost 60 years old and has been doing custom exhausts for about 40 years.

He had never seen an RL before so we put it up on the lift so he could have a gander. He LOVED how the exhaust was layed out. He said the only thing he'd do it is step up the last stretch of pipe right before the muffler (it's stepped down a bit from factory) and put a free flowing muffler on it (Magnaflow to be exact).

He said it was pretty damn good the way it is and it's a pretty straight forward exhaust system that didn't need much more.

The cost? He said a couple of hundred should be all for parts and labor and a 5 to 7 hp increase as well as bumping up the torque.

I don't know jack shit about exhaust systems but he's been in the biz a while and pretty much liked what he saw on the stock RL.
What size piping? 3inch and is it Mandrel Bent tubing?
 

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Discussion Starter #5
I'm not going 3". He just wants to step it up to all the same diameter (2.5 I believe he said it was) which is only consists of a small section right before the muffler. I think I remember him saying that the cat was good and he didn't really feel the need to change it. He liked the resonator as well and wants to leave that stock. He said he would even use the stock tip.

He said it's gonna look like the stock system except for the Magnaflow.


It's not like I went in there and said, "I only wanna spend X amount of cash, what can you do?" I went in there and said, "Take a look under there and tell me what you think needs to be done." and that's all he felt it needed.
 

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If the guy is good like the guy ive used around here then he will do hand bends and they will be just as good. Im also using a magnaflow my dad put it on his and there was a nice kick in the pants from it. He also did a custome dual exhaust setup, reeeeaaalllyy nice.
 

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still need to catch up to barry to check that out so I dont screw mine up.
 

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Discussion Starter #9
Redlinekid_04 said:
If the guy is good like the guy ive used around here then he will do hand bends and they will be just as good. Im also using a magnaflow my dad put it on his and there was a nice kick in the pants from it. He also did a custome dual exhaust setup, reeeeaaalllyy nice.

Yeah, I've seen pics of your dad's dual set up. It looks kick ass!

I trust this guy. Like I said, he's been in the business long enough to know what he's talking about. I also like that fact that he's not trying to sell me on a bunch of stuff that he knows I don't need.
 

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JPK said:
I'm not going 3". He just wants to step it up to all the same diameter (2.5 I believe he said it was) which is only consists of a small section right before the muffler. I think I remember him saying that the cat was good and he didn't really feel the need to change it. He liked the resonator as well and wants to leave that stock. He said he would even use the stock tip.

He said it's gonna look like the stock system except for the Magnaflow.


It's not like I went in there and said, "I only wanna spend X amount of cash, what can you do?" I went in there and said, "Take a look under there and tell me what you think needs to be done." and that's all he felt it needed.

The whole is exhaust is 2.25in Diameter. I'd suggest stepping up to 3 inch. You'd see much more power gains. The Cat should be good it is from a GM Truck so it'll flow good.
 

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Discussion Starter #11 (Edited)
Aeain said:
The whole is exhaust is 2.25in Diameter. I'd suggest stepping up to 3 inch. You'd see much more power gains. The Cat should be good it is from a GM Truck so it'll flow good.


I'll suggest that when I call him tomorrow.


I've ordered the SCdyne header too. That should be here within the next week or two. I know that it was designed to fit on the stock RL. Will going to a full 3" setup call for an additional mod to get the header on once I recieve it?
 

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Im not really sure about how beneficial three inch exhaust would be for our car. Ive heard that it works well with a turbo setup ,but with supercharger ive been told to keep it to like 2 1/2 to keep some back pressure. I dont think we will need 3 inch until we start seeing higher horsepower output. I just dont want to lose power by putting in 3 inch.... :( Then again we will never know till someone goes out and trys it!
 

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Discussion Starter #13
I'm thinking just go with John's suggestion at the exhaust shop.

If I feel the need for a 3" in the future, I can always have it done later. Right now, with the magnaflow and header, I think it'll do just fine.
 

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Redlinekid_04 said:
Im not really sure about how beneficial three inch exhaust would be for our car. Ive heard that it works well with a turbo setup ,but with supercharger ive been told to keep it to like 2 1/2 to keep some back pressure. I dont think we will need 3 inch until we start seeing higher horsepower output. I just dont want to lose power by putting in 3 inch.... :( Then again we will never know till someone goes out and trys it!
All boosted 4 cyls benefit from a 3inch exhaust. You lose some of the bottom end, not much though, for some more mid to top end power. Might see some gains on the bottom end though. Since no Red Line owner has done it yet who knows.
 

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Redlinekid_04 said:
Im not really sure about how beneficial three inch exhaust would be for our car. Ive heard that it works well with a turbo setup ,but with supercharger ive been told to keep it to like 2 1/2 to keep some back pressure. I dont think we will need 3 inch until we start seeing higher horsepower output. I just dont want to lose power by putting in 3 inch.... :( Then again we will never know till someone goes out and trys it!
I thought backpressure = bad? Why would you want to keep some?
 

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in order to have any low end on a small displacment engine you need some back pressure. Back pressure will affect the top end though. Its a sacrafice either way. Im building my car for all top end to 3 inch will be for me.
 

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goofyguy said:
in order to have any low end on a small displacment engine you need some back pressure. Back pressure will affect the top end though. Its a sacrafice either way. Im building my car for all top end to 3 inch will be for me.
Destroying a myth.



Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

Modern BMWs don't have to worry about the effects described above, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust gas out the tailpipe to propel the car forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum flow rate and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

- Adapted from Thomas V.
 

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on all of gm's supercharged ecotec powered show cars (cobalt ss w/ 272hp, s/c cavalier w/263hp, etc...) they used 3 inch exhausts. take that for what its worth.
 

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backpressure argument/myth aside, that myth is only remotely applicable for NA applications anyways

3" would be ideal imo, and the opinion of lots of friends I have that so crap like for a living, especially if you plan on moding more than just the exhaust
 

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northeast214 said:
on all of gm's supercharged ecotec powered show cars (cobalt ss w/ 272hp, s/c cavalier w/263hp, etc...) they used 3 inch exhausts. take that for what its worth.
I think this is a good clue. . .
 
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