mgmshar
02-14-2004, 07:29 PM
Stock Wastegate Control and Dual Wastegate Solenoids
Are you tired of burning your knuckles and testing your strength whenever you take your car to the track and crank-up the boost? Many of us with street cars run a lower boost level on pump gas. When we get to the track, we go through our ritual of shortening the actuator rod, followed by the “test of strength” required to hook the shorter rod over the wastegate puck. However, there is a way make that job a little easier: dual wastegate solenoids.
In a stock boost control system, the boost is controlled by the wastegate actuator, the wastegate puck, and the wastegate solenoid. The wastegate actuator keeps the wastegate puck closed by using force from a heavy spring inside the actuator. As boost builds, pressure from the outlet of the turbo is routed via the Y-hose to the actuator canister. The pressure inside the actuator canister opposes the spring and tries to force the wastegate puck open. When the exhaust gas pressure inside the turbine housing and the boost pressure inside the actuator canister reach a certain level, the wastegate puck is forced open against the spring. The exhaust gas bypassing the turbine and escaping through the wastegate limits the amount that the turbo spools, and boost is controlled.
The wastegate solenoid works by venting some of the boost pressure that is being routed to the actuator canister. The ECM rapidly cycles the solenoid on-and-off under boost conditions. When the solenoid is “on”, the solenoid is open and allows boost pressure to vent. The more time the solenoid is left “on” during the rapid cycling (a.k.a. “duty-cycle %” or “DC%”), the more boost pressure is vented before it reaches the actuator canister. The more boost pressure that is vented, the more boost the turbo will have to generate before the wastegate puck is forced open.
In order to increase boost, one of two things can be done: the spring tension can be increased, or more boost pressure can be bled-off before it reaches the actuator canister. Shortening the actuator rod effectively increases spring tension, so it is the most common method. Increasing the wastegate solenoid duty cycle will bleed-off more boost pressure, but can only be done by re-burning the PROM chip. Dual wastegate solenoids work by allowing more boost pressure to be bled-off, even with the same wastegate duty cycle being commanded by the ECM. When a second solenoid is added, the boost pressure coming from the turbo has two possible vent paths, so more of the pressure is vented-off. This is an effective way to raise boost quickly and simply.
On my car, I leave only one solenoid plugged-in when I’m on the street. This keeps the second solenoid closed, which means it does nothing to vent boost pressure. When I’m at the track, I simply plug-in the second solenoid. On my car, the boost will increase about 3 to 4 psi with no other changes. This means that I only have to tighten the actuator rod a few turns to get the boost I want, instead of having to turn it in almost until it bottoms. This makes re-hooking the rod over the wastegate puck MUCH easier.
There is one other benefit, for those who have adjustable boost controllers (like the Boost Command). The range of boosts that can be reached with the adjustable controller can be almost doubled with dual solenoids. For example, if the range of boosts that can be reached on a typical car is about 5psi (say from 15psi to 20 psi), a properly installed second solenoid will increase that range to 10psi (say from 15 to 25psi). A side-effect of this is that the sensitivity of the adjusting dial will also double, so care must be taken when making boost changes.
Wastegate solenoids can be purchased from many Buick vendors for about $25-$35. The “plug-and-play” wire harness adapter shown in the photo can be purchased from Caspers Electronics for about $30, or the wiring can be easily done with splice connections. Note that the two solenoids need to be wired in parallel, not in series. This is a relatively inexpensive way to prevent unnecessary burns and embarrassment when cranking-up the boost!
Are you tired of burning your knuckles and testing your strength whenever you take your car to the track and crank-up the boost? Many of us with street cars run a lower boost level on pump gas. When we get to the track, we go through our ritual of shortening the actuator rod, followed by the “test of strength” required to hook the shorter rod over the wastegate puck. However, there is a way make that job a little easier: dual wastegate solenoids.
In a stock boost control system, the boost is controlled by the wastegate actuator, the wastegate puck, and the wastegate solenoid. The wastegate actuator keeps the wastegate puck closed by using force from a heavy spring inside the actuator. As boost builds, pressure from the outlet of the turbo is routed via the Y-hose to the actuator canister. The pressure inside the actuator canister opposes the spring and tries to force the wastegate puck open. When the exhaust gas pressure inside the turbine housing and the boost pressure inside the actuator canister reach a certain level, the wastegate puck is forced open against the spring. The exhaust gas bypassing the turbine and escaping through the wastegate limits the amount that the turbo spools, and boost is controlled.
The wastegate solenoid works by venting some of the boost pressure that is being routed to the actuator canister. The ECM rapidly cycles the solenoid on-and-off under boost conditions. When the solenoid is “on”, the solenoid is open and allows boost pressure to vent. The more time the solenoid is left “on” during the rapid cycling (a.k.a. “duty-cycle %” or “DC%”), the more boost pressure is vented before it reaches the actuator canister. The more boost pressure that is vented, the more boost the turbo will have to generate before the wastegate puck is forced open.
In order to increase boost, one of two things can be done: the spring tension can be increased, or more boost pressure can be bled-off before it reaches the actuator canister. Shortening the actuator rod effectively increases spring tension, so it is the most common method. Increasing the wastegate solenoid duty cycle will bleed-off more boost pressure, but can only be done by re-burning the PROM chip. Dual wastegate solenoids work by allowing more boost pressure to be bled-off, even with the same wastegate duty cycle being commanded by the ECM. When a second solenoid is added, the boost pressure coming from the turbo has two possible vent paths, so more of the pressure is vented-off. This is an effective way to raise boost quickly and simply.
On my car, I leave only one solenoid plugged-in when I’m on the street. This keeps the second solenoid closed, which means it does nothing to vent boost pressure. When I’m at the track, I simply plug-in the second solenoid. On my car, the boost will increase about 3 to 4 psi with no other changes. This means that I only have to tighten the actuator rod a few turns to get the boost I want, instead of having to turn it in almost until it bottoms. This makes re-hooking the rod over the wastegate puck MUCH easier.
There is one other benefit, for those who have adjustable boost controllers (like the Boost Command). The range of boosts that can be reached with the adjustable controller can be almost doubled with dual solenoids. For example, if the range of boosts that can be reached on a typical car is about 5psi (say from 15psi to 20 psi), a properly installed second solenoid will increase that range to 10psi (say from 15 to 25psi). A side-effect of this is that the sensitivity of the adjusting dial will also double, so care must be taken when making boost changes.
Wastegate solenoids can be purchased from many Buick vendors for about $25-$35. The “plug-and-play” wire harness adapter shown in the photo can be purchased from Caspers Electronics for about $30, or the wiring can be easily done with splice connections. Note that the two solenoids need to be wired in parallel, not in series. This is a relatively inexpensive way to prevent unnecessary burns and embarrassment when cranking-up the boost!