hsitko

Firstly, having exhaust in the combustion chamber does not mean it will displace oxygen and fuel. Like i said a compression ratio is only a best case scenario. VERY BEST CASE. It is truthfully dependent on a lot of things. So keep in mind that when your engine is running its not running to its full potential almost ever. So having some exhaust in the chamber because of high back pressure means one thing basically. A leaner mixture in certain rpm ranges. You do know what a leaner mixture will do right? It will increase torque. This might be a different story if this car had a wideband stock that the ecu could add fuel with if it saw a leaner than normal mixture. But it cant. It only reads grams per second of oxygen which will not change if you dont expel all your exhaust and run lean. Keep in mind i'm not talking massively lean here. Only a little. And like i said. Its a small amount of torque and a small amount of horsepower i'm talking about here. Seriously less than 5 on average. An engine does not fill the combustion chamber to its maximum potential while the engine is running and thats a fact. Truthfully exhaust velocity is probably the biggest factor here. There are some fancy systems that have variable exhaust runner systems. One for high velocity at low rpm's and then one that opens up at higher rpm's to keep the velocity up with the increase of flow. Ceramic coating also helps. This is an interesting conversation i think. Good exhaust velocity will cause a good scavenging effect for sure. I really wonder how much time header producers spend on making a well engineered header. If you look at companies that make header parts like collectors there is some really fancy exhaust parts that you almost never see on name brand headers. Makes me kind of want to experiment on making my own.