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Sedans Dodge Charger Dodge Charger: Aftermarket Accessories & Performance Mods
74 messages, Last post on Nov 05, 2009 at 6:44 PM
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Replying to: rayban (Jun 11, 2006 10:31 am)
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Replying to: losski (Jun 14, 2006 10:58 am) |
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How is it that so many people (on this and a few other forums) are saying that they are losing performace and mpg with upgrades such as exhaust and intake?  I thought that exhaust and intake could only make and engine better, as my dad always said, "more air in, more air out"...  I think it could be because your not going all the way, perhaps if one were to install headers all the way thru to true cat-back dual exhaust... with cold air intake then the performance would surface?  I don't know... any thoughts? I personally am looking forward to installing duals and intake but now I am all
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Replying to: lividlizard (Jun 13, 2006 12:34 pm) 1 is that most aftermarket manufacturers don't go through the rigorous development and testing that the car's manufacturer does when designing the exhaust and intake. therefore, an aftermarket part is not always better than stock. 2 is that bigger is not always better. When you are dealing with an NA engine, a certain amount of backpressure is needed for the engine to operate optimally. If the exhaust is TOO free flowing, then you are not getting enough back pressure for the engine to burn the fuel efficiently. And for the intake side, it needs to be designed for optimal airflow and keep out as much engine heat as possible. Again, not all aftermarket systems are designed properly. |
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| Hey I'm considering purchasing an 06 Charger. I want to add exhaust but I'm torn between Borla and Magnaflow and does anyone know much about rims? I want to go with 22 inch wheels but I've heard that they can scratch when you take sharp turns, does anyone know anything about this? If that's the case what about 20 inch wheels? Thanks... | |
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Replying to: msanders (Jun 13, 2006 3:39 pm) |
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Replying to: msanders (Jun 13, 2006 3:39 pm)
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Replying to: losski (Jun 14, 2006 10:56 am)
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Replying to: xtec (Jun 15, 2006 2:36 pm) 
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While I haven't studied the any of the four engines that DC is putting into the Charger and its siblings, I do have a considerable amount of research history to offer an opinion as to why a large free flowing exhaust system can in many cases yield lower fuel economy and lower power at any given throttle setting. 1) Exhaust system harmonic resonance. This is a huge issue in 2-Stroke engines, and manufacturers spend considerable resources to tune the exhaust system such that the shock wave inside the header rebounds in such a fashion to actually aid in cylinder packing (volumetric efficiency). As any of you 2-Stroke dirt bike riders can attest, there is usually a fairly narrow "Sweet Spot" in the power curve where the power spikes. Said power spike is usually caused in these engines by the shock wave of the exhaust pulse rebounding off the back side of the exhaust chamber and then "pushing back" toward the exhaust port. As the intake port is almost always open before the exhaust port is fully closed, the combination of the pressurized intake charge and the rebounding shock wave leads to greater cylinder packing. 2) In 4-Stroke engines it was long ago found (like in the 1920s or 1930s) that engine efficiency (via better scavenging) was improved by opening the intake valve before the exhaust valve was fully closed, thus using the intake charge to help "Push" the remaining exhaust out. This technique is commonly referred to as "Valve Overlap", and my guess is that all of the Charger engines are so designed. 3) Assuming the Valve Overlap scenario holds true for the Charger engines, then by replacing the stock intake and exhaust system with "Better breathing" hardware, you will most likely find that the larger intake charge meets far less resistance in the combustion chamber during the period of overlap because the better breathing exhaust system is allowing too much scavenging. Said another way, with better breathing, you are effectively pumping a higher than optimal percentage of your unburned intake charge right out into the exhaust system before the exhaust valve closes. Regardless of how the engines are designed, the bet is that DC has tuned the harmonics of the intake and exhaust to match as best as possible the rest of the engine. To the best of my knowledge, the only way to successfully utilize a freer flowing intake and exhaust system is by installing a cam specifically designed to compliment the new plumbing (i.e. given the better intake flow and the better scavenging, the new cam will provide for a shorter period of overlap, or even eliminate the overlap all together). Once again, I have not researched these engines enough to know if my theory is true, so please don't quote my brief thoughts as fact. Let the discussion begin. Best Regards, Shipo
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