Header Dyno Testing & Comparison, Tri-Y and 4 -Into-1

The mounting flange used to join the upper and lower portions of the tri-Y design features heavy-duty construction and O-ring seals, not unlike the two-piece factory manifold.

What better way to demonstrate each design's tuning effect than to compare them on the same engine? To properly test not just the tri-Y and 4-into-1 header designs but also the stock exhaust manifold, we assembled a B16A test mule. The 1.6 liter was chosen for its availability because the B16A is obviously much more prevalent than any B18C mill. A healthy engine was in order. Something both powerful yet representative of what might be run on a typical street car. The short-block's modifications are minimal and consist of stock replacement, forged Probe Racing pistons and matching forged connecting rods. The rod and piston upgrade allows us plenty of latitude in terms of engine speed potential and even gives us the ability to add nitrous at a later date. Though the stock short-block will withstand plenty of abuse, we wanted the security of the forged internals during seemingly endless hours of dyno testing.

Both the tri-Y and the 4-into-1 headers feature a dedicated mating flange for connecting to the catalytic converter or cat-back exhaust. Note the use of the stock-type, multilayer donut gasket.

The beefed up block was topped off with a hand-ported and slightly milled cylinder head, along with a set of Crane Stage 1 camshafts. The Stage 1s offer 242 degrees of intake duration and 230 degrees of exhaust duration. The lift values check in at .457 of an inch on the intake and .425 of an inch on the exhaust. These represent a healthy jump over the stock B16A pieces. The Crane cams are optimized using a set of the company's adjustable camshaft sprockets. A Holley 68mm throttle body is used to supply airflow to the B16A intake manifold while the fuel system is composed of a modified AEM fuel rail housing a set of 30 lb/hr injectors. An Aeromotive adjustable fuel pressure regulator is relied on to control the fuel pressure on the engine dyno and a Hondata programmable ECU is employed to dial in the air/fuel and timing curves. The dyno exhaust consists of a 2.5-inch section of tubing connected to a 3-inch, 90-degree elbow and finally out to a 6-inch evacuation tube. For testing purposes, each header, including the OEM exhaust manifold, were run through this same exhaust system.

Like any good header, Airmass pieces feature precision-welded seams and flanges.

The first order of business was to run the B16A test engine equipped with the stock exhaust manifold. The factory B16A exhaust manifold consists of a cast-iron upper section bolted to a tubular lower section. Though cast iron, the stock exhaust manifold closely resembles a typical tri-Y header. Like many tri-Y headers, the stock manifold pairs runners one and four and runners two and three. The paired runners then merge into a single collector to form the final Y section. After tuning camshaft timing, the air/fuel mixture and ignition timing curves, the B16A produced 195 hp at 7,700 rpm and 139 lb-ft of torque at 7,200 rpm. Thanks in part to the torque-producing nature of the tri-Y design, the little B16A produced over 130 lb-ft of torque from 5,200 rpm (our VTEC engagement point) to 7,900 rpm. Our mildly modified 1.6L B16A was pumping out as much power as a 1.8L ITR engine, and with the stock exhaust no less. We could hardly wait to get the Airmass piece on because we just knew we would break the 200hp barrier.

The 4-into-1 header features stepped primary tubing. The tubing exiting the port measures 1.5 inches, stepping up to 1.625 inches approximately 7.5 inches away from the mounting flange.

In addition to offering improved flow potential and true scavenging, the Airmass headers also reduced curb weight by some 15 pounds. Honda's cast iron manifolds aren't exactly light.

Some header applications include oxygen sensor relocating provisions. For those that don't, these sensor relocation kits make installation easy.