You won't find the word "wastegate" in the dictionary. It's a bit troubling. Especially for us. This entire magazine is based off of a concept that, officially, doesn't exist-at least according to Webster. But for the most part, we all know what a wastegate is and what it does. It's possible Webster hasn't had time to do some updating in a while. Maybe we can help:
waste·gate ('wAst·'gAt), n. 1. An exhaust bypass valve employed by turbocharged engines used to control boost pressure by means of alternating exhaust gas flow either to or away from the turbine.
There. That wasn't so hard, was it? You can thank me later, Webster.
We tested Synapse Engineering's...
We tested Synapse Engineering's new Synchronic wastegate on an Integra GSR engine. At 14 psi, the B18C1 produced 427 hp on Do It Dyno Performance Center's Dynojet. The car makes upwards of 630 hp, but there are two reasons we conducted our tests at low boost: first, traction limits on the dyno limits our accuracy, and second, 14 psi is about the maximum where the conventional wastegate used wouldn't produce creep.
Major breakthroughs in wastegate design and engineering have been few and far between as of late. Yes, valve and valve seat materials have been tested, changed and patented, diaphragms have been toughened up, and of course aesthetics have been played with, but the simple yet effective principles of the conventional actuator-type wastegate remain just that-simple and unchanged. But there are always those who have to go and make a simple thing more complex. And so is the case with the engineers at Synapse Engineering, the company responsible for redesigning the conventional wastegate.
The wastegate gets its name from the fact that it does its job by wasting a portion of the engine's exhaust gases. For a wastegate to work, all it has to do is bypass a determined amount of exhaust gas destined for the turbine to some other place. This, in turn, controls the turbine's shaft speed, which determines how much boost the engine sees. Since a turbo system is sort of self-feeding (the more boost that's made the more exhaust gases are made) both variables are regulated by manipulating just one, boost, through exhaust flow. The higher volume of gas the wastegate bypasses, the slower the turbine spins. The opposite is also true. There are a number of problems associated with the conventional wastegate design, but the biggest is that it wastes exhaust gas energy to do its job. Wasting something to get something isn't always the best way to get a job done, but it's unavoidable when dealing with wastegates. There's nothing we can do about that. At least not for now.
The Synchronic wastegate does...
The Synchronic wastegate does not have a rubber diaphragm, so there's not much here that can wear out. At full valve lift, you can see the four individual chambers and surface areas of the wastegate. Each chamber is sealed off from the rest of the wastegate with o-rings and grease, both proprietary to Synapse.
But there are other problems inherent to traditional wastegates that can be fixed. One such problem has to do with valve lift, and is one that Synapse has actually improved upon with its Synchronic wastegate. A conventional wastegate valve begins opening much earlier than we'd actually like it to. This way, they do their job at, say, 20 psi by beginning to open at, say, 10 psi. Even though we don't want it to open at 10 psi, or tell it to open at 10 psi, it does anyways. If it didn't, we'd see more than 20 psi at the top. The point at which the valve initially opens is referred to as its cracking pressure-our 10psi point in this example. Cracking pressures for most external wastegates are generally about half of whatever maximum boost is. As soon as the valve is cracked open, exhaust gases that would otherwise continue to spool the turbine until maximum boost is reached are wasted. This will either make it take longer for the turbo to reach maximum boost or not let it reach that point at all. Either way it's bad for power curves and for performance.
Conventional wastegates aren't complex. The design consists of two separate housings, one of which houses the valve, which the exhaust gases flow past. The other side contains a spring that preloads itself against the valve to keep it closed. This is also the side that receives the boost pressure signal. A plate and rubber diaphragm are fitted beneath the spring and fixed to the top of the valve. The spring applies pressure to keep the valve closed, but when boost pressure exceeds spring pressure, the diaphragm and plate force the spring to compress and open the valve. A spring that, when compressed, exhibits 15 pounds of force will open the exhaust bypass valve once that amount of pressure is exerted onto the diaphragm ... sort of. The problem with conventional wastegates is that the rubber diaphragms stretch, can tear, and exhibit durometer changes as temperatures change. Pressure is wasted on stretching the diaphragm before the valve is even opened. This is bad for boost control. Besides the fact that rubber diaphragms eventually wear out, tear, get softer or harder, even in new condition they're designed to stretch. This means that boost pressure diverted into the wastegate must stretch the diaphragm before the valve can even begin to move. It makes for slow response time when it comes to boost control, and as temperatures change, it can actually respond differently to equal boost pressures. In other words, as temperatures rise, it can take longer to stretch the diaphragm and open the valve. And, at the very least, it's unpredictable. In the amount of time it takes the conventional wastegate to fully stretch the diaphragm and begin to crack the valve open, the Synchronic's valve is fully opened. This is because the Synchronic wastegate says goodbye to the rubber diaphragm. It says goodbye to the wastegate as we know it.
Valve-to-valveguide binding is not an issue with the Synchronic wastegate since there is no valveguide or metal-to-metal contact. The valve remains centered in its bore by the piston attached to its other end. Pressure is equally exerted on the piston, which keeps the valve centered properly.
Synchronic wastegates are...
Synchronic wastegates are shipped with varying sized valve seats. Seats can easily be swapped for larger or smaller ones based on flow requirements. Upgrading to a larger wastegate is no longer necessary. It takes less than five minutes to remove the V-band-clamped wastegate and exchange seats.
Each port controls a separate...
Each port controls a separate chamber inside the wastegate. By combining ports/chambers, various boost levels can be reached without a boost controller. Hooking up all three ports shown here will result in the lowest boost level possible. Each port/chamber has its own distinct surface area, which must be reacted against. Different port combinations mean different boost.