The D-series recipe featured here may not be suited to everyone's taste. It is by no means the most powerful D-series ever built and it certainly isn't the easiest to put together. What it is, though, is a combination of parts assembled to make the most power possible within a specific set of rules. The motor was built a few years ago and to our knowledge is the only one of its kind. Its relevance to us is that while there is a good deal of machine work involved, the parts required are reasonably inexpensive. This could be the ultimate D-series sleeper motor.
The engine was built to compete in NASA's Honda Challenge H1 hybrid class. In 2005, the rules were adjusted so that cars attempting to compete with a D-series engine could weigh 400 pounds less than the class-dominating, K20-powered cars. Additionally, while the K20 motors had to be basically stock, the D-series motors were allowed modest modifications. They were allowed to use any OEM Honda parts they wanted in the bottom end. Additionally, aftermarket parts were permitted in the valvetrain along with unlimited head preparation.
Everyone knew that the little motor could never match the power of its competitors. But, nobody was really sure if it could get close enough to take advantage of its lower minimum weight. The person who set off to find out was Bernardo Martinez of Redondo Beach, Calif. An accomplished H4 and ITA class racer, he already had a healthy collection of D16A6 motors ready for surgery. He laboriously tore them down and pieced them together with other parts until he found a combination that worked. Rival hybrid class competitors named his concoction the "inbred motor" but he always referred to it as the "Super D."
Super D Engine BuildThe foundation of any powerful race engine is the bottom end. This started with a well-used D16A6 aluminum block from an '88-91 CRX Si. The block was cleaned and then inspected for cracks and other potential defects. Next, the casting flash was removed and sharp edges were deburred with a die grinder. The block was then bored for the factory oversized pistons from a natural gas powered '04-05 Civic GX. These pistons are domed for higher compression but need to be notched for valve clearance. Their wristpins are located to match the stroke of a D17 crank. However, they are still slightly in the hole at top dead center. To maximize compression the block was decked by 60 thousandths of an inch.
To increase engine stroke, a D17A7 crankshaft from an '04 Civic with a 94.4mm stroke replaced the D16A6 version, which only had a 90.0mm stroke. This bought the engine an extra 78cm3 of displacement. With the longer stroke, however, the rods interfered with the block and main bearing girdle. Both required the removal of some material for adequate clearance.
Upon assembly, D17 rods were fitted onto the crankshaft with high-strength ARP rod bolts. The D17 crank required the use of a D17 oil pump, which in turn, was only compatible with the D17 oil pan. A D17 oil pickup and main cap seal were also needed to make things fit. The final fitment issues with the D17 crank were with its larger snout diameter. The timing belt pulley from the D17 needed to be used but first the crank trigger wheel needed to be machined off. Lastly, the D16A6 crank pulley had to be bored and re-keyed to match the D17 crank's snout.
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