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Discussion Starter #1 (Edited)
WTB Catless downpipe or hf catted dp GXP

Looking for a catless downpipe or a high flow catted dp for GXP.

Post or PM.

Thanks.
 

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I don't know of a catless vendor offhand but any of them (DDM, Werks) could probably fab you one pretty cheaply. A local muffler shop or performance shop could also and it shouldn't be very expensive.

I know Madmods built his own, cutting the flanges off the stock and welding them to an ebay high flow cat (for the 2.4 but the same principal).
 

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Discussion Starter #3 (Edited)
Yeah I was hoping someone had a werks or solo thats been sitting around for the gxp. If not I'll pick one up new this winter sometime because it won't get installed until I am ready to tune this spring anyway.
 

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talk to me around spring when you are thinking about doing it and i will likely trade you strait up. I have a catless and I don't really like how loud it is. i moved to a place where i am closer to neighbors and it is LOUD on a cold start.
 

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talk to me around spring when you are thinking about doing it and i will likely trade you strait up. I have a catless and I don't really like how loud it is. i moved to a place where i am closer to neighbors and it is LOUD on a cold start.
If your only issue is the cold start up, all you have to do is turn off cat warm up with HPTuners. I did so myself for the same reason. The cold start up with a cat-less down-pipe is pretty "aggressive". Now it just starts up and idles. None of that unnecessary high idle cat warm up garbage. Keep the 30hp, and get rid of the noise.:thumbs:
 

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Not sure where anyone thinks they get 30 hp from removing the cat, I had the Solo high flow and the car was tuned for it, then installed the straight cat, all I really noticed was a loss of low end torque and this was after the car was tuned for no cat. I am just to lazy to put the cat back. I did get my low end torque back with a anti-reversion cone Solo made for me. This is an old Harley trick, everyone wants loud pipes on a Harley, so they run straight pipes no muffler, now they have no low end torque but the bikes runs like a bat out hell up top. You need a certain amount of back pressure to get decent low end torque. Jeff at Solo (also a Harley Owner) knew exactly what I was talking about and made one that goes at the end of the downpipe, it basically breaks up the the exhaust when it tries to go back up the pipe.

Here is s more dynamic if lengthy explanation, I learned a lot about exhaust tuning building my Harley, it has roughly the same horse power as a stock Solstice N/A

Exhaust Scavenging and Energy Waves
Inertial scavenging and wave scavenging are different phenomena but both impact exhaust system efficiency and affect one another. Scavenging is simply gas extraction. These two scavenging effects are directly influenced by pipe diameter, length, shape and the thermal properties of the pipe material (stainless, mild steel, thermal coatings, etc.). When the exhaust valve opens, two things immediately happen. An energy wave, or pulse, is created from the rapidly expanding combustion gases. The wave enters the exhaust pipe traveling outward at a nominal speed of 1,300 - 1,700 feet per second (this speed varies depending on engine design, modifications, etc., and is therefore stated as a "nominal" velocity). This wave is pure energy, similar to a shock wave from an explosion. Simultaneous with the energy wave, the spent combustion gases also enter the exhaust pipe and travel outward more slowly at 150 - 300 feet per second nominal (maximum power is usually made with gas velocities between 240 and 300 feet per second). Since the energy wave is moving about 5 times faster than the exhaust gases, it will get where it is going faster than the gases. When the outbound energy wave encounters a lower pressure area such as a second or larger diameter section of pipe, the muffler or the ambient atmosphere, a reversion wave (a reversed or mirrored wave) is reflected back toward the exhaust valve without significant loss of velocity.

The reversion wave moves back toward the exhaust valve on a collision course with the exiting gases whereupon they pass through one another, with some energy loss and turbulence, and continue in their respective directions. What happens when that reversion wave arrives at the exhaust valve depends on whether the valve is still open or closed. This is a critical moment in the exhaust cycle because the reversion wave can be beneficial or detrimental to exhaust flow, depending upon its arrival time at the exhaust valve. If the exhaust valve is closed when the reversion wave arrives, the wave is again reflected toward the exhaust outlet and eventually dissipates its energy in this back and forth motion. If the exhaust valve is open when the wave arrives, its effect upon exhaust gas flow depends on which part of the wave is hitting the open exhaust valve.

A wave is comprised of two alternating and opposing pressures. In one part of the wave cycle, the gas molecules are compressed. In the other part of the wave, the gas molecules are rarefied. Therefore, each wave contains a compression area (node) of higher pressure and a rarefaction area (anti-node) of lower pressure. An exhaust pipe of the proper length (for a specific RPM range) will place the wave’s anti-node at the exhaust valve at the proper time for it’s lower pressure to help fill the combustion chamber with fresh incoming charge and to extract spent gases from the chamber. This is wave scavenging or "wave tuning".

From these cyclical engine events, one can deduce that the beneficial part of a rapidly traveling reversion wave can only be present at an exhaust port during portions of the powerband since it's relative arrival time changes with RPM. This makes it difficult to tune an exhaust system to take advantage of reversion waves which is why there are various anti-reversion devices designed to improve performance. These anti-reversion devices are designed to weaken and disrupt the detrimental reversion waves (when the wave's higher-pressure node impedes scavenging and intake draw-through). Specifically designed performance baffles can be extremely effective, as well as heads with D shaped ports. Unlike reversion waves that have no mass, exhaust gases do have mass. Since they are in motion, they also have inertia (or "momentum") as they travel outward at their comparatively slow velocity of 150 - 300 feet per second. When the gases move outward as a gas column through the exhaust pipe, a decreasing pressure area is created in the pipe behind them. It may help to think of this lower pressure area as a partial vacuum and one can visualize the vacuous lower pressure "pulling" residual exhaust gases from the combustion chamber and exhaust port. It can also help pull fresh air/fuel charge into the combustion chamber. This is inertial scavenging and it has a major effect upon engine power at low-to-mid range RPM.

There are other factors that further complicate the behavior of exhaust gases. Wave harmonics, wave amplification and wave cancellation effects also play into the scheme of exhaust events. The interaction of all these variables is so abstractly complex that it is difficult to fully grasp. There does not appear to be any absolute formula that will produce the perfect exhaust design. Even super-computer designed exhaust systems must undergo dyno, track, and street testing to determine the necessary configuration for the desired results. Last but not least, the correct choices and combinations of carburetor, air cleaner, cam shaft, ignition, and exhaust used in the proper relationship to each other for the intended riding application will always produce the finest quality results. Most important of all, is to do your research prior to purchasing the combination of products and equipment best suited to your individual style of riding.[/font]
 

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Not sure where anyone thinks they get 30 hp from removing the cat, I had the Solo high flow and the car was tuned for it, then installed the straight cat, all I really noticed was a loss of low end torque and this was after the car was tuned for no cat. I am just to lazy to put the cat back. I did get my low end torque back with a anti-reversion cone Solo made for me. This is an old Harley trick, everyone wants loud pipes on a Harley, so they run straight pipes no muffler, now they have no low end torque but the bikes runs like a bat out hell up top. You need a certain amount of back pressure to get decent low end torque. Jeff at Solo (also a Harley Owner) knew exactly what I was talking about and made one that goes at the end of the downpipe, it basically breaks up the the exhaust when it tries to go back up the pipe.

Here is s more dynamic if lengthy explanation, I learned a lot about exhaust tuning building my Harley, it has roughly the same horse power as a stock Solstice N/A

Exhaust Scavenging and Energy Waves
Inertial scavenging and wave scavenging are different phenomena but both impact exhaust system efficiency and affect one another. Scavenging is simply gas extraction. These two scavenging effects are directly influenced by pipe diameter, length, shape and the thermal properties of the pipe material (stainless, mild steel, thermal coatings, etc.). When the exhaust valve opens, two things immediately happen. An energy wave, or pulse, is created from the rapidly expanding combustion gases. The wave enters the exhaust pipe traveling outward at a nominal speed of 1,300 - 1,700 feet per second (this speed varies depending on engine design, modifications, etc., and is therefore stated as a "nominal" velocity). This wave is pure energy, similar to a shock wave from an explosion. Simultaneous with the energy wave, the spent combustion gases also enter the exhaust pipe and travel outward more slowly at 150 - 300 feet per second nominal (maximum power is usually made with gas velocities between 240 and 300 feet per second). Since the energy wave is moving about 5 times faster than the exhaust gases, it will get where it is going faster than the gases. When the outbound energy wave encounters a lower pressure area such as a second or larger diameter section of pipe, the muffler or the ambient atmosphere, a reversion wave (a reversed or mirrored wave) is reflected back toward the exhaust valve without significant loss of velocity.

The reversion wave moves back toward the exhaust valve on a collision course with the exiting gases whereupon they pass through one another, with some energy loss and turbulence, and continue in their respective directions. What happens when that reversion wave arrives at the exhaust valve depends on whether the valve is still open or closed. This is a critical moment in the exhaust cycle because the reversion wave can be beneficial or detrimental to exhaust flow, depending upon its arrival time at the exhaust valve. If the exhaust valve is closed when the reversion wave arrives, the wave is again reflected toward the exhaust outlet and eventually dissipates its energy in this back and forth motion. If the exhaust valve is open when the wave arrives, its effect upon exhaust gas flow depends on which part of the wave is hitting the open exhaust valve.

A wave is comprised of two alternating and opposing pressures. In one part of the wave cycle, the gas molecules are compressed. In the other part of the wave, the gas molecules are rarefied. Therefore, each wave contains a compression area (node) of higher pressure and a rarefaction area (anti-node) of lower pressure. An exhaust pipe of the proper length (for a specific RPM range) will place the wave’s anti-node at the exhaust valve at the proper time for it’s lower pressure to help fill the combustion chamber with fresh incoming charge and to extract spent gases from the chamber. This is wave scavenging or "wave tuning".

From these cyclical engine events, one can deduce that the beneficial part of a rapidly traveling reversion wave can only be present at an exhaust port during portions of the powerband since it's relative arrival time changes with RPM. This makes it difficult to tune an exhaust system to take advantage of reversion waves which is why there are various anti-reversion devices designed to improve performance. These anti-reversion devices are designed to weaken and disrupt the detrimental reversion waves (when the wave's higher-pressure node impedes scavenging and intake draw-through). Specifically designed performance baffles can be extremely effective, as well as heads with D shaped ports. Unlike reversion waves that have no mass, exhaust gases do have mass. Since they are in motion, they also have inertia (or "momentum") as they travel outward at their comparatively slow velocity of 150 - 300 feet per second. When the gases move outward as a gas column through the exhaust pipe, a decreasing pressure area is created in the pipe behind them. It may help to think of this lower pressure area as a partial vacuum and one can visualize the vacuous lower pressure "pulling" residual exhaust gases from the combustion chamber and exhaust port. It can also help pull fresh air/fuel charge into the combustion chamber. This is inertial scavenging and it has a major effect upon engine power at low-to-mid range RPM.

There are other factors that further complicate the behavior of exhaust gases. Wave harmonics, wave amplification and wave cancellation effects also play into the scheme of exhaust events. The interaction of all these variables is so abstractly complex that it is difficult to fully grasp. There does not appear to be any absolute formula that will produce the perfect exhaust design. Even super-computer designed exhaust systems must undergo dyno, track, and street testing to determine the necessary configuration for the desired results. Last but not least, the correct choices and combinations of carburetor, air cleaner, cam shaft, ignition, and exhaust used in the proper relationship to each other for the intended riding application will always produce the finest quality results. Most important of all, is to do your research prior to purchasing the combination of products and equipment best suited to your individual style of riding.[/font]
Did you actually read any of that or just copy and paste it directly? Where in any of that does it discuss how removing a restriction like a catalytic converter would not increase performance?

All I read was some complaining your catless downpipe didn't yield the results you wanted, so that means it must not give gains, then a copy and paste of some discussion of wave disrupting in the exhaust and how a lot of factors are at play. I don't see where it goes on about catalytic convertor free exhausts not making more power.:lurk:
 

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Ask Dave at DDM what he thinks of all the false claims about the downpipe adding horse power, and he doesn't sell down pipes or high flow cats. The POINT that you seem to miss is that less restriction, ie removing the CAT can actually reduce performance, open pipes work great at high end but most of us don't use our cars as dragsters. I have the results I want from my car it makes over 300 hp with the stock turbo and torque which is the more important of the 2 is crazy up over 350. I was at a dyno shootout between 5 different Solstcie GXP's all of them tuned by Westers with different exhausts some high flow cats some stock and one catless. Guess who made the most torque, the one with the stock cat and even stock exhaust, he did not make the most horsepower. That was when I started reading.
 

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Discussion Starter #10 (Edited)
I don't mind that this turned into a conversation, but FWIW I AM STILL INTERESTED IN A CATLESS/HF DP for anyone that comes across this thread. Only reason I would consider a high flow is to keep noise down...though I am more interested in power. That being said:

Say I lose a little low end grunt with a catless dp...What is considered low end power 2k? 3.5k? What is considered high end 6k? 8k? I only plan on revving out to 67-6800 tops, though I find myself running the rpms well over 6k most of the time and I feel as though I am running out of power at that point(butt dyno mind you) and I love running 3rd and 4th gear out when I have the space. I would think the catless dp gets you a broader power band and that would be ideal for my driving habits. Extra low end torque would be nice but if it drops off so bad above 5k I'll still yearning that extra bit top end.
 

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Solo High Flow Cat

I have had my Solo High Flow cat on for about a year and love it. I did see performance increase and I love the sound my exhaust makes.:)
 

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I have a Solo hi-flow cat (told it was new, but there is evidence of having been on the car- no new gasket or hardware) and a "test pipe" for the GXP. Both are available. $300 shipped for cat, $150 for pipe (not to Romania!).

Any more specifics, we'll see if Spikey can answer them;)
 
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