Now would be a good time to talk about just how far a wastegate's valve opens, and how that helps or hurts things. When a wastegate is unable to bypass a large enough volume of exhaust gases, excessive boost will occur. This is known as boost creep. The common fix is to fit a wastegate with a larger valve and exhaust opening to the turbo. While the larger valve fix works, it doesn't really get to the core of the problem, and in turn, it can actually create an entirely new problem. Large-valve wastegates will consistently regulate and prevent over-boost, but once boost is stabilized they tend to release too much exhaust gases and waste what could be used for additional turbine spin. More power lost here. The Synchronic wastegate uses a self-centering piston instead of a diaphragm. The piston reacts more quickly and also allows tuners to swap springs for different rates while keeping boost levels the same. This means you can adjust how fast the valve reacts per pound " of boost. The Synchronic wastegate's billet aluminum piston negates the need for a valveguide, and also allows the valve to spin. There are two benefits here: first, eliminating the valveguide ensures against any binding or sticking when the wastegate gets older and exhibits some corrosion, and second, it allows the valve to spin 360 degrees for even wear on the valve and seat. Conventional wastegate valves don't spin, so hot spots and wear usually build up in certain places, causing just a leak at best.
One feature that makes the Synchronic wastegate unique is its interchangeable valve seats. Synapse offers different sized seats, each effectively changing the wastegate's inlet diameter and ultimately the volume of air that will pass through it. This allows users to fine-tune even further, not having to compromise with what the existing diameter of the wastegate is. Altering the power curve is easy when seat sizes can be switched as flow characteristics for different sized engines and different sized turbines will require varying amounts of exhaust gas bypass. The wastegate includes various sized seats, including 39mm and 50mm ones, which means you won't have to pay for any upgrading as far as wastegates go when you turn up the boost significantly.
Conventional wastegates exhibit very low valve lift. It's not necessarily the size of the
The Synchronic wastegate's valve housing is manufactured of 304 stainless steel, not 347 stainless steel or 254 alloy like most wastegates. Alloys like 347 and 254 have a high nickel content, which contributes to thermal expansion. The 304 alloy has a more balanced nickel and chromium level, which doesn't allow for such levels of thermal expansion and, in turn, helps fight off boost creep from warping and fatigue. The 347 and 254 alloys are stronger from a structural standpoint, but since the wastegate doesn't carry a structural load it doesn't matter here. The Synchronic's valve and valve seat are also rather unconventional in their materials. For example, 400 stainless steel was selected here instead of the more common Nitronic stainless steel alloy. The 400 alloy's high chromium content helps stabilize the valve's steel at high temperatures, unlike Nitronic alloys that are high in Nickel and allow for thermal expansion, resulting in valve sticking under extreme temperatures.
The Synchronic actuator consists of four varying-sized surface areas inside, not two equal ones like conventional wastegates have. As boost pressure is applied to a surface area, a force is applied and the spring compresses, thus lifting the valve. The Synchronic wastegate's varying surface areas and ports make for a number of different boost combinations that can be applied without the need for a controller. All that's required is splicing the lines together and routing them to a pressure source on the engine. This all controls how far up the valve moves, not just how many pounds of boost the turbo will produce. The conventional wastegate is also different in this respect. Rates can be changed by swapping springs but remain dependent on the amount of preload. Also, as spring rates increase here, and more boost is made, the diaphragm has to stretch more, resulting in a valve that doesn't lift as much and possible boost creep. This all determines when the wastegate will open and just how much boost the engine will see, so it's got to be right. With the Synchronic wastegate, users can adjust spring preload and spring rate interdependent of one another as well as control how the valve rises, and how high it rises, as boost climbs. This increases response time and wastegate flow characteristics and should be tailored for individual engines.
One of Synchronic's add-on valve seats. It's really easy to pop out existing seats once th
So how does it work? We tested the Synchronic wastegate on an Integra GSR engine making around 430 hp at 14 psi. The B18C1 was fitted with a competitor's conventional wastegate that uses a 40mm valve. Pushing the engine past 14 psi created much more boost than we needed since the conventional wastegate's valve had minimal lift, which resulted in boost creep. In order to replicate the situation as best as we could after switching wastegates, we kept the GSR's boost level at 14 psi with the Synchronic wastegate installed. If we had " more time, we would have liked to have retuned the AEM engine management and cranked up the boost with the new wastegate. Instead, we performed some comparison tests at low boost and got ourselves comfortable with the new wastegate. Without any other changes, the Synchronic produced more torque and horsepower after 6500 rpm. We can attribute this to the fact that we were able to tailor the valve seat size that worked best for our combination. The Synchronic allowed us to relieve just the right amount of exhaust pressure to stabilize 14 psi. If we simply bolted on the biggest wastegate we could have found, we likely wouldn't have seen increases at the top end since too much exhaust gases would bypass the turbine. Sure, boost would have been controlled either way, but at the expense of lost exhaust gases that we could have used. And we know that the smaller wastegate wasn't working since boost creep was inevitable at higher pressures.
The variables of the Synchronic wastegate seem almost endless. Between valve seat diameter changes, spring preload and rate adjustments, and port/chamber configurations, there is a setting to suit just about any powerplant we've ever come across. Maybe now the word wastegate will finally be added to the dictionary.