What the Hell Happened to Project Silvia?

,

Finally, after something like 18 months, it was time to get to work finishing the swap! When I started this swap, it was supposed to take less than a month. I had removed the head in the middle of a dry summer and had simply sprayed the cylinder bores with WD40, stuffed oily paper towels on top of the pistons to catch any grit or dust that might try to find its way between the piston and bore, and then sealed the top of the block with the best Nashua 557 duct tape money can buy. WIth light finally visible at the end of this head swap’s tunnel of dispair, I finally peeled back the duct tape only to find the 18 month delay had far surpassed the sealing abilities of duct tape. 

 Shit…

The duct tape had sealed well enough, in fact, to let some moisture in and then lock it in place where it could make collossal, bottom-of-the-ocean rust formations in the cylinder bores. This was not gonna be easy to fix…

This was the condition of the bores when I took the head off. In spite of untold mileage in Japan, and thousands of hard, abusive track miles since it was potato-charged, the bores looked nearly perfect.

Oh well…

The corrosion is way beyond fixable with something simple like a hone job. The block will actually have to be overbored to get rid of the pitting. Science is out of the window, then. Time to step back and turn this into a full-Kojima engine build.

The New Plan:

So, instead of a simple A-to-B S13-to-S14 head swap, its time for a full modernization of Project Silvia’s powerplant. Here’s the design brief: This is still a street-driven track car, and I’m still too cheap to dump $7/gallon on race gas, so the engine will have to be built for maximum performance on 91 octane crap. And because I like puppies and breathing, it will have to breathe through a cat. Those are the ground rules, and maximizing performance with those restrictions points right back to where I was trying to get in the first place: the widest powerband possible. It’s rare to get too far past 300 hp on 91-octane, but we’ll try to push the knock limit back as far as possible. Still, with a finite horsepower cap, the smart money is on broadening the area under the torque curve. Flexibility makes you faster than a nasty spike in power every day.

The big stick for this goal will be a twin-scroll Borg Warner EFR turbo. A twin scroll turbo can actually have a substantial influence on the knock limit of an engine. By keeping exhaust pulses from adjacent cylinders from interfering with each other, just like a 4-2-1 header, a twin-scroll turbo can make a huge improvement in exhaust flow. This means less hot residual exhaust gasses left in the cylinder, and this can dramatically lower combustion temperature. Lower combustion temperature means less knock, which means you can run more boost or more advance, either of which will give you more power. 

Twin scroll turbos also happen to do a better job at collecting pulse energy, so you don’t have to choke down the A/R of the exhaust housing to get the turbo to spool. A bigger exhaust housing means less backpressure. Less backpressure means better exhaust flow and once gain, lower combustion temperatures and more power.

Running a twin-scroll turbo on an SR20 pretty much requires using a Full Race exhaust manifold, but that’s no bad thing. Full Race’s smooth, large diameter, relatively long runners will dramatically improve exhaust flow compared the cramped cast iron stock manifold. And that will, say it with me, lower combustion temperatures, raise the knock ceiling, and let us make more power on crappy 91-octane gas.

Since we have to bore the block, new pistons are required. This opens up an opportunity, though. JE Pistons and K1 Technologies are working together on a long-rod piston and rod combo for the SR20. If we can free up a little power by reducing piston side loading and the resulting friction, that’s free power that isn’t going to be octane limited at all. The pistons and rods are nearly ready now, so we should have details soon.  

Forgotten about Project Silvia? Jog your memory here.