Back in Volume 86, Hypertune reader, Sean, provided us with a Power Pages story on his own car, a CM5 Honda Accord. To date, Sean’s installed an Unorthodox Racing underdrive pulley kit, a Hondata intake manifold gasket, a HKS Hi-Power muffler, a stainless steel catalytic converter from Hot Bits and a Cusco oil catch tank.
In his last Power Pages installment, Sean fitted a set of Skunk2 camshafts and a GReddy E-Manage Ultimate, which was tuned by Jackie of JC Racing. Before the cams and the E-Manage, Sean’s Accord was pushing out a respectable 124.51hp and 15.4kg/m of torque. After the cams and the E-Manage were fitted, the humble K20A3 gained a total of 12.16hp and 0.04kg/m.
Sean had the right recipe going; he’d sorted out the intake, the back portion of the exhaust, a little bit of headwork and taken care of the air/fuel ratios. The only thing remaining was what most would argue is one of the most important aspects which needs to be addressed in a naturally aspirated engine: the notoriously restrictive, factory issue exhaust manifold.
Many do not realize that a good exhaust manifold, or extractor or header, is a key part when it comes to extracting power from a naturally aspirated engine. If designed right, a header will have scavenging properties, which is to say, that the header actually helps to suck the exhaust gas out of the exhaust ports, therefore improving exhaust gas flow and increasing power.
A properly designed header isn’t just a mish mash of bent steel pipes, each runner has to be designed properly, each bend and curve has to be taken into account to ensure the header does its job properly. How the runners combine into the collector also needs to be thought out carefully, as each pulse of exhaust gas from every cylinder could interfere with the following pulse of exhaust gas, therefore disrupting the flow of exhaust gas in the header.
Sean ordered a header from DC Sports, a well known and popular American company specializing in aftermarket performance parts. Sean’s DC Sports header is a two piece header with a 4-2-1 configuration, and is made of mild steel with a corrosion resistant ceramic coating.
If you look at the stock exhaust manifold and compare it to the DC Sports header, you’ll see that both designs are completely different. The K20A3’s exhaust manifold looks nothing like and no where near as free flowing as the DC Sports header with its stubby runners.
Sean took the DC Sports header back to JC Racing to be installed. Of course, after the header was installed, the Accord was strapped to the dyno once again.
The last time the Accord was dyno’d, she churned out 136.67hp and 15.44kg/m of torque. With the DC Sports header, she pulled 143.34hp and 16.1 kg/m of torque. That’s an impressive increase of 6.67hp and 0.66kg/m of torque, from only a header.
DC Sports Ceramic Coated 4-2-1 header