Project S13 Silvia
Taking 2 Pounds off the Bouncy Bits!
by Dave Coleman
The last installment of Project Silvia was a story of tragedy. A tempting, but ultimately unnecessary attempt to broaden my powerband, coupled with a string of bad luck, and my own staggeringly shortsighted outdoor storage strategy had reduced my stone-reliable SR20DET into a worthless, rusty mess.
|This is what your cylinder walls look like if your idea of block prep is WD40, duct tape, and a year of neglectful indifference.|
So at the end of the last installment, I changed my strategy. Instead of a simple S13-to-S14 head swap, this was now a full balls-to-the wall rebuild to get the most output from this engine I possibly could. The most, with three very important caveats.
When I built Project Silvia the first time, there was an opportunity to install a race gas map. Clark Steppler, the Nissan ECU mastermind at Jim Wolf Technology, had rigged up a way to switch between 4 different fuel and timing maps on a stock Nissan ECU. We could easily have tuned one map for the recently-introduced 91-octane distilled bum sweat we run our cars on in California, and another for 100-octane unleaded. But I was never even tempted by this idea. The thought of paying for a full tank of $5/gallon race gas was just too outrageous!
A few months ago, 87 octane was $5/gallon (its dropped nearly a dollar since then), so it should come as no surprise that race gas is still off the menu. So that's caveat #1: This engine will be built around a diet of 91 octane. That means we'll be doing everything possible to keep this thing from knocking, and we'll be looking for power in places that don't require higher cylinder pressures–like friction reduction.
#2 is simple. I am a mammal, and as such, I'm smart enough not to shit on my own dinner plate, or to poison my own air. Well, at least not any more than is absolutely necessary to keep myself entertained. So this engine will breathe through a cat.
And finally, #3 is is that we must define “the most” very carefully. Getting the most out of this engine does not mean making the biggest peak power number. It means a big, wide, useable powerband. If peak power must be sacrificed to improve responsiveness and torque, I just might do it. The crude VVT system on the S14 head should make that unnecessary, though.
|This is me, actually machining a Miata cylinder head with a file. This is why.|
Ok, so now that we all understand the goals, how the hell am I going to pull it off? Every time I touch this engine, I'm overcome by an urge to machine it with a file, or weld some Mexican Dodge parts to it. My instincts are so thoroughly ghetto, I'm not sure I can trust myself to go full Kojima on this thing. So I've assembled a team of detail-obsessed nerds to look over my shoulder and slap my hand every time I reach for the zip ties.
Clark Steppler has been my go-to Nissan nerd for years. I always turn to Clark first for advice on nonsense like this, and one of his first pieces of advice on this engine surprised me. “Don't assemble it yourself.” The thought of not building it myself never even crossed my mind. I always build my own engines (for better or worse), but perhaps Clark knows me better than I know myself. Instead, he suggested I turn to Nick Hunter at 5523 Motorsports to screw it together. My initial hesitation evaporated as he started telling me about Nick's attention to detail, including strange little tricks like how he hand cuts oiling grooves in the main bearing support to bring SR20s up to the same spec as the rare Pulsar GTi-R engines. My engine could use a bit of that obsessive attention to detail, and it sure isn't gonna get it from me!
Nick is also the guy who heroically built a backup VQ35DETT for Dai Yoshihara's drift car on only 3 days notice, in his living room, when the original engine blew a head gasket during demo runs in Abu Dhabi and had to be running again a few weeks later in Qatar. Yeah, Ok, I like this guy… Mine will be one of the first batch of engines built in 5523 Motorsports' fancy new clean room, so we won't have to worry about getting silver engine paint on his La-Z-Boy.
The third member of my ghettocharging recovery support group is MotoIQ's own Chuck Johnson. Chuck's day job at JE Pistons focuses his nerdly obsession at the bouncy bits, and that's where this project finally gets going. Parts catalogs are an engineer's best friend, and it was reading his favorite parts catalogs a few years ago that Chuck figured out the Honda H22 long-rod trick that has spread through the MotoIQ garages like a virus.
Squeezing a longer connecting rod into an engine is a relatively common trick for extending the rev range of an engine. The benefits of longer connecting rods are simple, if a little tricky to grasp at first blush. There are several things going on when you change the length of the connecting rod. Most of them are subtle, and some of them are good.
Less friction: Look at this diagram of a reciprocating group with the crank at 90 degrees. When there's some force pushing down on the piston, the angle of the connecting rod ensures there will be a reaction force shoving the piston into the cylinder wall. A longer connecting rod will result in a slightly shallower connecting rod angle. Shallower angle means less side load, which means less piston to wall friction.