Mash the throttle at 4000 rpm under the same conditions and full boost takes only a second
POWER BOOST CONTROLLER
Now, to achieve consistency. When we first cranked the boost on our SR20DET, we did it by stuffing an $11 ball valve from McMaster-Carr into the wastegate line. We later upgraded to an adjustable bleed valve from Jim Wolf Technology that was slightly less prone to boost spikes, but still mechanical and still inexpensive. The problem with a passive, mechanical system like either of these boost controllers is that when the conditions affecting the turbo's performance change, the controller can't change to adjust for them.
Day and night are the most obvious examples of this phenomenon. We first adjusted our bleed valve to reach 15 psi of boost on a mild afternoon in San Diego.
Now, on a blazing L.A. summer day when the air is thin, it only makes 13 or 14 psi, but spikes over 18 psi in the cool, dense night air. This is only mildly annoying, and actually makes the car really fast at night, but it will be dangerous as we push closer to the limit of the SR20 and our 91-octane gas. If we tune to the ragged edge at 17 or 18 psi and suddenly the car starts spiking to 21 psi, things could get ugly. It's time to call in the electrons.
When we did our boost controller comparison test back in July 2002, the GReddy Profec B stood out as the simplest, most easy-to-use controller. It worked with just two knobs-one to adjust boost, one to control how quickly it spooled up-and no unnecessary complexity. It was the easiest to set up, took the fewest test runs to reach the target boost and worked very consistently.
The constant, switched, and illumination power wires were sourced from behind the instrume
Ironically, we are not using a Profec B on Project Silvia. The Power Enterprise Power Boost Controller we did settle on takes the Profec B's two-knob simplicity and adds one key extra feature. It's built into an analog boost gauge. That means there's one less magic box to mount in the car, and several fewer wires we have to chase through the dash.
Both boost controllers work by reducing the pressure signal to the wastegate actuator. The bleed valve does it by poking a carefully calibrated hole in the wastegate line. The Disco Potato turbo's wastegate actuator is designed to open at 11 psi, so setting the bleed valve to 15 psi means opening up that hole until 4 psi leaks out.
The Power Enterprise boost controller (and most electronic boost controllers, really), uses a solenoid valve to completely block the signal to the wastegate. When the boost target is approaching, the valve can slam open, letting the pressure open the wastegate, then quickly cycle between letting boost in and burping it out to keep the wastegate opened just so. The magic of electronics means it can watch the rate of boost climb and anticipate if it has to open early to keep from overshooting the target.
Indeed, when we compared the two controllers in cool evening air, the bleed valve caused substantial boost spiking when we slammed the throttle open at 4000 rpm. The Power Enterprise controller saw how quickly boost was rising and managed to prevent the spike.
Like the power fan controller, the instructions for the power boost controller are a little tough to interpret, but the controller is actually easier to figure out than the fan controller is. Our only design gripe is that the gain knob (the one controlling how fast the turbo spools) is on the back of the gauge, forcing you to remove the gauge if it needs adjustment. In reality, the gain adjustment is just used to prevent boost spikes, and even with the adjustment maxed out, there was no spiking at 15 psi of boost.
We mounted both the Power Enterprises gauges, plus an A'PEXi EGT gauge salvaged from Project Matrix in a CarbonTrix gauge pod we salvaged from the same car. The pod is mounted to the windshield using the same double-stick tape used to hold on body kits. The pod has never threatened to fall off the windshield, even in the kind of heat that melts flesh.
Wiring the gauges is no harder, or easier, than any other. All three need power, ground, switched power and illumination wires, so we ran just those four into the pod, then split each three ways inside the pod. Jamming all these plus the signal wires for the three gauges, and their sometimes bulky connectors through the tiny hole in the back of the gauge pod is one of the biggest challenges, exceeded only by figuring out how to get the wires down into the dash and through the firewall.
The difficulty of this unusual mounting arrangement is, as usual, all for good reason. Mounting the gauges high puts them closer to the driver's line of sight. Mounting them on the windshield puts them as far away as possible, reducing the amount of refocusing the driver's eyes have to do. And mounting them all on the same plane, rather than staggered up the A-pillar, means you can take it all in one glance. Meaningless details? They don't feel meaningless when you're sideways at 100 mph.
COMING SOON: MORE POWER
What do they call a bigger radiator, an oil cooler, bigger brakes and more power? On my sweet Chevy van they called it a towing package. Great, we now have the ultimate flat-black tow vehicle. Now it's time to get back to the business of making power. We'll start turning those knobs next time.
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We mounted the map sensor and boost control solenoid to one of the air filter box mounting
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The information coming from the EGT, temp and boost gauges is too important to hide down i
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What do you call a more robust cooling system, more power and better brakes? You call it a
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Power Enterprise
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AEBS
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Brits Inc.
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