A lengthy explanation is due here;
You don't need two Catalytic converters. The only reason Hyundai utilizes two, is to meet ULEV standards. Catalytic converters are strictly to meet hydrocarbon emission standards and are a bottle neck to any exhaust system. This is why most engine builders omit them as quickly as they can. Yes there are high flow cats but they are still a restriction to the overall exhaust system.
Sorry, but I totally disagree with your assessment regarding back pressure. All turbos produce back pressure. On non-turbo engines back pressure is a single issue, the pressure in the exhaust system, but on a turbo engine its actually two issues, pressure in the post-turbo exhaust system, and pre-turbine back pressure in the exhaust manifold. The best exhaust for a turbo is no exhaust, Simply an exhaust dump as is use on many turbo applications including motorcycles. A larger down pipe is a must to provide enough scavenging and exhaust pulse which comes from the combustion chamber.
Pre-turbine back pressure is one of the biggest, yet totally invisible, killers of tuned turbo engines, and is also a massive reason certain engine setups don't make the power they're hoped to either. Pre-turbine back pressure is inevitable, it's just a turbo engine thing, one of the things that spools your turbo, and a worthwhile exchange for acceptably fast spool up for your application. Unfortunately, too small a turbine, be it the wheel, housing, or both, can cause too much back pressure, which in turn means exhaust gas struggles to leave the cylinders, huge EGTs, higher cylinder temps, diluted fuel/air mix in the cylinders, and so on, which in turns means hugely more susceptible to engine-killing detonation , not to mention general reliability issues and power restriction.
Turbos have come along way from the past but smaller turbo applications in todays engines with less spool up time, are now becoming a in issue in other ways. There are very few engines today that utilize 11:1 compression ratios and small turbo setup. The Kona 1.6Tis one of these and is primarily to reduce spool up times and produce more useable torque much lower in the RPM range for everyday driving.
In the real world, most engines can be expected to have up to twice the back pressure as boost, but more than that, and some engines do have a LOT more than that due to peoples obsessions with tiny turbine housings (and a great many badly specced turbos with overly small turbine wheels compared to compressor size), which causes a lot of reliability and performance issues, and with no way to know what back pressure they've got, most don't even realize this is the main culprit!
You often find that if your pre-turbine back pressure is more than about twice what the boost pressure is (and some engine setups can be 3 times or more!), changing to a bigger turbine housing, or ideally a bigger turbine wheel, will not only drop the back pressure, but hugely increases power and reliability per psi boost, and actually not slowing your spool up at all despite the bigger turbine; in fact in some situations it speeds it up as it was so strangled beforehand.
The only way to optimize back pressure, is to go with a bigger turbo and use a back pressure gauge to see how much your application is actually strangling your engine. This is why you have to direct your attention to both aspects of the intake and exhaust first and dyno tune, tune, tune.! However, there is only so much you can do with the tiny OEM turbo the Kona 1.6T Gamma engine has. So it's always going to be a limiting factor for the engine until you change that puppy out for a larger one. There is only one larger kit available right now which produces well over 350 whp. Don't recommend it unless you; gut the con rods and pistons for lower compression and stronger units, mill the heads for a copper o-ring seal for higher boost pressures, which will amount to well over 35 psi.
Been dealing with turbos for decades in all types of applications from; MB4-2 aircraft tow tractors, semi tractors, cars, motorcycles etc. There's nothing like a big turbo to optimize back pressure. without some back pressure a turbo application just doesn't work well.:wink::smile:
Blessings and Peace
as it's not approved by Hyundai." However, he's a performance nut like some of us. So what he doesn't know about won't effect anything, as he stated.
