Nitrous Optimization Part 2 - Go, Baby, Go!
13 The Zex blow-down kit...
13 The Zex blow-down kit comes with two bottle fittings that hold a 3,000-psi burst disc in place between the fitting and the bottle: one for bottles with an internally threaded disc assembly, and one for those with external threads. Be sure to empty the bottle before trying to remove the disc.
14 Once the burst-disc fitting...
14 Once the burst-disc fitting has been screwed in hand-tight, you’ll need to torque it to 30 pounds; since the disc is being clamped into place by doing this, any more or less could compromise its integrity.
15 Final assembly of the...
15 Final assembly of the blow-down: The burst disc fitting points up, and the feed for the nitrous system points down.
Prior to assembling the hose, I'd watched instructional videos online, as well as read Mark Stielow's excellent book, Pro Touring: Engineered Performance, where he describes the process. The short version is, insert the hose into the outer fitting, then screw in the inner fitting. In my experience, assembly lube and the proper vise jaws make a world of difference. Thread sealant and a proper aluminum wrench don't hurt either.
Intent on keeping the blow-down as low-profile as possible, I drilled a hole on the rear deck between the storage tray and the front lip, so the hose could pass down into the storage area. I then bored another hole in the bottom of the storage area for the bulwark fitting. Since I get nervous anytime I'm bolting metal through fiberglass, I trimmed down a pair of 1/8-inch-thick rubber washers and used them on either side when I screwed down the bulkhead fitting.
16 The purge is basically...
16 The purge is basically a valve in front of the nitrous solenoid that allows you to clear the system of any excess air, ensuring there’s nothing but nitrous in the line. To do this, install an inline fitting at the nitrous solenoid. The line coming off the fitting goes to a separate solenoid that opens when you hit the purge button.
17 The purge solenoid goes...
17 The purge solenoid goes together much the same as the nitrous and fuel solenoids, and is wired the same. There’s a braided-steel line going into the inlet, and, on the outlet, a pipe fitting that holds the tube through which the nitrous exits. A small, crushable sleeve inside the fitting fits over the tube, compressing around it when the nut is tightened.
18 After mocking up the location...
18 After mocking up the location of the purge tube, I cut it to length. I then used vacuum tubing to sleeve it, and a slit piece of fuel line to locate the tube in the fender vent without scratching the paint. I also used flat-black paint on the steel tube to keep it from rusting.
Similarly, although I wanted to install a purge system to get the air out of the lines before hitting the "go" switch, I had no interest in festooning the outside of the car with pipes and lights to announce it. Instead, I mounted the purge solenoid to a vacuum canister located behind the driver-side front wheelwell, just inside the fender vent. Being careful to mock it up so that I got the right dimensions, I carefully bent the hard tube and cut it so that it would exit the fender vent flush with the outside. I also painted the tube flat black to deter rust, sleeved it with vacuum hose so it wouldn't scratch the paint where it bears against the inside of the fender vent, and used a slit piece of fuel line over that to locate the tube.
Wiring it up was straightforward: I spliced into the power going to the arming switch and ran that through the included mini-fuse to the solenoid, then grounded the solenoid to the engine block. While the purge kit came with a perfectly good momentary pushbutton switch, I ordered one from Vehicle Wiring Products, out of England, that looked more period-correct for the car.
19 Once painted and sleeved,...
19 Once painted and sleeved, the tube is ready to be installed in the solenoid. Do so by pressing it into position and tightening the fitting down around it. Next, replace the fender vent, using your fingers to guide the tube into the right position, and bolt the vent back into place.
20 There are two main purposes...
20 There are two main purposes for a purge: to clear the lines of air, and to advertise that you’ve got nitrous. You can guess which of those I’m more interested in.
21 This switch plate was...
21 This switch plate was CNC machined by Tray Walden of Street Shop, Inc (www.streetshopinc.com). As a specialist in high-performance chassis for ’53-’82 Corvettes, Street Shop manufactures many of its components in-house using CNC equipment.
By now, you've figured out there are a fair number of switches, buttons, and lights involved in this process, and not a lot of places to put them. I was talking with Tray Walden of Street Shop, Inc., about this when we were at the Sevierville (Tennessee) Corvette show last fall, when he casually mentioned he could do it on his Haas CNC mill. "How long would it take to draw something like that up?" I asked. He simply turned around his laptop and showed me the one he'd been designing while we talked. After I got him the dimensions, he made the plate and cut in the labels for the switches, leaving them silver against the black anodizing. While I didn't intend for the plate to look "correct," the goal was to make something that would still look right for a chrome-bumper shark, and Walden did an excellent job of turning that idea into a piece of machined metal.
With the switch plate in hand, it was time to measure, then slit, file, and grind out the center console and its metal supports to fit the switch plate in place. I could then wire up all the switches, some of which required ground wires. Installed, the plate has a switch and indicator for the driving lights (which are coming soon), as well as the purge button, low-fuel-pressure light, and a covered toggle switch to arm the nitrous system. Another item I ordered from the UK (this one from Stafford Vehicle Components), the toggle has a small red LED in the end that lights up when the switch is on. If you somehow arm the system by mistake, you'll know it--especially at night, when the LED makes the red plastic cover glow red.
22 Here, the console has...
22 Here, the console has been cut from the top to fit the underside of the plate, and the structure underneath it ground out to accommodate the switches. The switches and lights are all wired up, and it’s time to mount them in the plate and install it into the console. This is much easier to do with the shifter console removed.
23 The switch plate after...
23 The switch plate after final assembly. The switch and indicator on the left are for driving lights—stay tuned—and the nitrous controls are on the right. The covered toggle switch is the arming switch. The latter has a red LED in the end, so when it’s on, you know it.
24 In an effort to conceal...
24 In an effort to conceal the nitrous-pressure gauge, but still have it visible to the driver, I disassembled the ashtray assembly, took out the removable tray, and replaced it with a gauge fitting I machined from UHMW, a plastic. Since the chrome inside the tray was in poor condition, I sprayed it flat black.
One of the other controls I chose to install was a nitrous-pressure gauge in the cockpit. While I'd previously had one on the bottle--which is the preferred location--you can't always see that from the driver seat. Instead, I removed the ashtray assembly and measured the opening in which the removable tray fits, then machined a plate from UHMW, an industrial plastic. This plate would fit into the opening and hold a liquid-filled nitrous pressure gauge from Zex. While the gauge screwed nicely into an inline fitting, the 15 or so feet of -4 AN line that Zex sends with the kit uses a smaller outside diameter than regular AN line, and therefore won't accept a standard two-piece hose end. While I could have ordered pre-made AN lines from Zex to go from the bottle to the gauge--and from the gauge to the solenoid in the engine compartment--the company didn't offer the lengths I needed.
As an alternative, I bought a coil of -4 AN line from Summit, measured to length, and installed Earl's straight swivel hose ends with the appropriate adaptor that let me screw them into the fitting for the nitrous-pressure gauge. Cutting to length also removes any "dead air" in the system, but be forewarned that cutting braided-steel hose so it will go in the fittings later is devilishly hard. When you measure, figure in some extra length, because you may well have to make that cut twice.
25 To connect the gauge,...
25 To connect the gauge, I mounted it with an Ano-Tuff inline fitting from Earl’s, and built up a hose that went from the gauge to the bottle in the back of the car. Another ran from the gauge to the nitrous solenoid in the engine compartment. Notice that the fitting is clocked to one side to clear the cigarette lighter, which is still functional.
26 Because the supplied braided-steel...
26 Because the supplied braided-steel hose could not accept the usual aftermarket hose ends, I had to make AN lines in order to use the inline fitting for the pressure gauge. This required -4 AN hose, hose ends from Earl’s, vise jaws to hold the fittings during assembly (they tend to “roll out” of flat vise jaws), a non-marring aluminum wrench, and lube/sealant.
27 The finished product:...
27 The finished product: The liquid-filled gauge fits in the ashtray with enough clearance for the lid to slide open and closed, and the lighter remains functional for cell-phone chargers, GPS, and so on.
While getting it all bolted together inside the console is a real challenge, the finished gauge hides nicely underneath the sliding door for the ashtray. It'd be downright low-key if it weren't for the switchplate and the bottle bolted to the back deck.
With everything installed, it was time for a trip to Balanced Performance, to put the car on the chassis dyno and see what sort of numbers the engine produced with and without the nitrous. Unfortunately, the initial dyno pull revealed a significant engine problem, which put further testing on hold until we can get it resolved. Stay tuned.
Special thanks to Jimmy from O'Reilly Auto Parts; Dave Emanuel of Random Technology; Tray Walden of Street Shop, Inc.; L.W. Precision Tools; and N. Ga. Hydraulic.
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