We continue to break new ground on our 2015 Mustang EcoBoost, Project 5-Liter-Eater. We’re finding out what works well, and what does not on the latest Mustang engine combination and chassis. Recently, the guys over at Turbosmart sent us one of their Kompact Blow Off Valves, which we tested. The results were pleasantly surprising and gained tremendous amounts of torque over the OEM electronically-controlled part.
Helping us round out the next part of our boost equation, Turbosmart recently sent us one of its new internal wastegate actuators (IWG75), part number TS-0622-8102. Designed as a direct replacement for the OEM EcoBoost wastegate actuator, this part comes with the promise of additional gains in horsepower and torque, and is another part that should be easy for any enthusiast with hand tools to install.
A New Can
The OEM actuator is a softly sprung part made from stamped steel. It’s economical, and it works for a stock application, but it has several drawbacks. -Marty Staggs, Turbosmart
“The OEM actuator is a softly sprung part made from stamped steel. It’s economical, and works for a stock application, but has several drawbacks,” Staggs says. According to Staggs, the OEM wastegate actuator has around 7 psi of base spring pressure, “The OEM unit is also massively preloaded to increase the spring load.” This limits the amount of total travel for the wastegate actuator and the weaker spring allows high exhaust drive pressure to crack the gate open at lower rpm. The result is a very ‘soft’ boost curve that can also be a bit inconsistent.
“The Turbosmart IWG75 wastegate actuator is designed to operate with 2mm, or approximately 3/16-inch preload, while the OEM wastegate actuator has a half-inch or more of preload.” According to Staggs, using less preload gives the wastegate actuator a wider window to operate in providing better boost control, “With the Turbosmart IWG75, the operating range of the actuator is significantly increased, allowing more precise management of the valve itself. The result is much quicker spool-up, turbo response, and more consistent boost pressure throughout the RPM range.”
Turbosmart constructs its wastegate actuators using a billet aluminum shell, as opposed to the stamped steel of the OEM part. The high-temperature silicone diaphragm features Nomex reinforcement for high heat resistance. The locking collar cap allows owners to change springs out quickly and easily for fine-tuning the performance for their particular application.
We ordered our wastegate actuator with a 10 pound spring. “We designed our internal wastegate actuators to use the same springs as our external wastegates so users can easily switch springs to tune their combination further.” Staggs said there are a few advantages when switching to a higher base spring pressure and the lower preload, “There is more mechanical leverage to keep the wastegate valve closed longer at higher exhaust drive pressure.” As a turbocharged engine accelerates, exhaust drive pressure also rises. On our EcoBoost, a computer-controlled vacuum solenoid activates the wastegate actuator, signaling it to open by varying percentages and reducing the amount of exhaust flow (drive pressure) to the turbo, thus reducing boost. At the same time, as drive pressure on the turbine side increases the pressure will eventually overcome the spring pressure and preload of the wastegate actuator, causing it to crack and open. When the wastegate cracks under high drive pressure it causes a drop in exhaust drive pressure, diminishing turbine speed and boost pressure, resulting is less power.
According to Staggs, the higher spring pressure of the Turbosmart wastegate actuator will extend the point where our wastegate cracks open, resulting in higher mechanical leverage. This provides more operating rpm on the turbo, and should improve horsepower and torque. What we are concerned with for this test is torque and power under the curve. “We are not specifically looking to make more total boost here. It is more about optimizing how fast the engine gets into boost, and having it stay there longer,” Staggs says.
Bring on the Boost
With our wastegate actuator in hand we headed to London Chassis Dyno where Chad Epperson helped complete the install and testing of our new Turbosmart hardware. With the engine cooled down sufficiently, we made a baseline dyno pull on a hot and humid Kentucky morning. Running the car using the dyno’s tachometer, our test window is 2,500-5,600 rpm, and we mat the throttle to wide open at 2,200 rpm to get boost pressure building as the window opens. Our baseline numbers were 300.2 hp and 421.2 lb-ft of torque. We averaged 260.1 hp and 328.2 lb-ft of torque for that baseline. With temperatures already climbing into the mid-80s and humidity at 60 percent, the dyno was showing a weather correction factor of over seven percent. With terrible air we were a little down on peak horsepower over previous runs in better weather.
After our baseline dyno we cooled the car down using fans until we could handle the hardware surrounding our turbo. The Turbosmart wastegate actuator is easily installed. We do recommend some caution as the high preload of the stock actuator will cause it to move suddenly once the rod is released from the wastegate. The entire installation is a direct bolt-on affair requiring rudimentary metric sockets and a ratchet. The most difficult step is removing the turbo heat shield so the installation can take place.
Breaking Down The Power
We ran into an issue between our dyno runs. After our baseline and installation our car’s Advancetrac system had a freak-out moment and would not allow us to make a dyno run as it kept applying the rear brakes. Normally the system stops this by 30 mph. To remedy the problem we ultimately had to reset our tune to stock and then reflash it again. While this doesn’t make any programming changes to the car, and it cleared the malfunction, the adverse effect is that it cleared our adaptive strategy. This means the computer is not selecting the most aggressive profiles available, which it likely does given our driving style. Given more time, it would be interesting to see if horsepower or torque increases as we drive the car for a few hundred miles and allow the computer to “learn” our driving habits again. Our peak and even our power under the curve numbers could potentially be higher once the computer adjusts.
The peak gains from our test are somewhat deceiving. Peak numbers are great for bragging rights, power under the curve, and average power is what a serious enthusiast understands as important. It is average horsepower and torque along with power under the curve we’re most interested in. This is where the engine will spend most of its time on the street, and in our case at the autocross and drag strip. Average horsepower and torque improved to 275.2 hp and 347.3 lb-ft of torque an improvement of 15.1 hp and 19.1 lb-ft throughout the test window over the baseline test from earlier in the day.
We can also break the data down further. Overlaying the dyno graphs it becomes obvious that our EcoBoost is making significantly more torque and horsepower across our test window. Taking a glimpse at 3,500 rpm, an area we often find ourselves shifting at, offers the best insight into what the Turbosmart IWG75 wastegate actuator is doing for us. During our baseline dyno pull from that morning at 3,500 rpm, the engine was making 222.3 hp and 335.1 lb-ft of torque. At the same RPM with the Turbosmart IWG75 wastegate actuator installed, and no other changes to our car, the engine was making 254.1 hp and 382.2 lb-ft of torque. This represents a gain of 31.8 hp and 47.1 lb-ft in an area of the engine’s operating range where we do most of our driving.
According to Staggs, this improvement is made possible through better management of our turbo with the Turbosmart wastegate actuator. While the total amount of additional boost is minimal, the Turbosmart actuator is allowing our turbo to make slightly more boost earlier in the RPM range. Even though we are only making about 1 psi more, we’re reaching maximum boost faster. This verifies what Staggs says about this product not being about the peak boost number, but rather getting to that boost level and maintaining it, as well as drive pressure not overcoming the wastegate and cracking it.
We are not specifically looking to make more total boost here. It’s about optimizing how fast the engine gets into boost and having it stay there longer.” -Marty Staggs
For now, on the street and the autocross, we can tell you that the addition of nearly 32 hp and 50 lb-ft of torque in the low RPM band is noticeable. The car takes off from a stop, acceleration is greatly improved, we can disable the traction control, and kick the tail of our car out much easier when we want to (in a controlled environment of course), and high-speed acceleration like interstate merging is vastly improved. There is a marked improvement in the car’s behavior throughout the low rpm range.
With a street price well under $200, the Turbosmart IWG75 wastegate actuator for the 2015 Mustang EcoBoost is another high-value modification that brings a lot more punch to our project car for a relatively small cash outlay.