Join Date: Sep 2018
Feedback Score: 0 reviews
Wow, sooo much misinformation...
First of all, the wastegate is on a turbocharger to limit turbine speed (to prevent turbocharger over-speed), and as a result, limit maximum boost pressure.
Removing or blocking off the "red" line to the wastegate actuator is never a recommended practice. The wastegate actuator on a GT38 (stock) turbo will only hold between 6-8 psi before actuating. Even when the shaft/spring is cranked down, they are not designed to allow excessive boost. That is precisely why there is a solenoid valve in the boost control/wastegate circuit (more on that below...). In addition, since the diaphragms are relatively small (in diameter) and the springs are a bit weak, the actual wastegate itself can "blow open" under high drive-side (exhaust) pressure situations. And, believe me... the wastegate only has to "crack" open to lower the exhaust-side pressure, and drop the drive speed and boost pressure.
Even the actuators on the Ball-bearing GTP-38R turbo (rated for up to 40 psi boost) are "factory" set for, and will begin to open at only 6-8 psi. (I have tested them).
Since the actuator operates at such a low pressure, the wastegate solenoid valve was put in.
The wastegate solenoid valve is normally open, and bleeds the boost signal from the intake Y-spider (red line) back to the intake boot (through the green line). When the PCM commands less boost (via the MAP sensor signal), the wastegate solenoid is commanded shut to direct the boost signal directly to the actuator (the solenoid valve closes, reducing the bleed to the intake, and redirecting the signal to the red line/actuator), thus limiting turbo speed and boost pressure.
I personally run the Banks "Bighead" actuator (it was on the truck when I got it). This one has a larger diameter diaphragm, and much heavier (yet adjustable) spring, which prevents "blow open" of the wastegate. I also run the 38R turbo. I bench-set my BigHead (with compressed air, using an accurate gauge and pressure regulator) to begin opening right at ~39-40 psi. That way I'm assured of max boost potential without over-speeding/over boosting (beyond the recommended limit of the turbo).
I believe there are a couple of companies offering "aftermarket" wastegate actuators, similar to the Banks unit. So any that have a larger diaphragm and spring, and allow you to set the desired opening pressure should work fine. If you're running a stock GT38 turbo, I would set the gate to open at no more than 25 psi. That's the max pressure they should run at, and last.
I highly recommend testing and pre-setting the actuator cracking pressure on the bench, BEFORE the turbo is installed (or in the truck, if the turbo's still installed). This will assure proper operation. Unfortunately, it's a b!tch to do it if it's in the truck, and buried back under the firewall! LOL. But it can be done...
So I'd say Banks, but only because I have personal experience with them. I can't speak to the others... but I definitely would replace the stock one! The Banks stuff is a bit over-priced in my opinion, but it is of good quality.
Al in SoCal
AFE Intake; Garrett 38R; DieselSite Turbine Jacket
HPS Hi-Temp CAC Boots; Banks Big IC, Banks Engine Brake
External Oil cooler & Remote filter; Stealth 4-line Twin HPOP, Melling LPOP
Swamp's: 160cc/30% Injectors & HVHF IDM; DP-Tuner F5; Fluidamper Balancer
Custom Full Reg.-return Fuel System, Pre-& Post-pump filtration
Mishimoto Radiator & Exp. Tank; T444 Water Pump w/Filtration
Bellowed S/S Up-pipes; 4" Turbo-back Custom Exhaust into Twin Stacks
SouthBend D-D Clutch; ZF 6-spd w/CoreShifters Short-throw Stick
GearVendors O/U Drive
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Last edited by Calico5; 01-17-2019 at 12:06 AM.