I posted this info in the EvoM Newbie section today and thought it might be useful here. It's not really newbie info as I go fairly in depth in to how wastegates, actuators and boost controllers work.
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You cannot upgrade only the wastegate on a stock Evo.. The turbo uses an internal wastegate.
You can upgrade the wastegate actuator. This is mainly to allow the turbo to flow close to it's maximum capacity at high RPM where the stock actuator isn't strong enough to hold itself closed.
If you are unsure as to what the wastegate itself does, it is the one mechanical part that can directly adjust the amount of exhaust gases that pass to the turbine of the turbocharger. The wastegate vents gases away from the turbine to regulate turbine speed and therefore boost pressure. Less flow to the turbine means lower turbine speed and less potential flow/boost on the compressor side of the turbo.
The wastegate is loaded with a spring (or a spring loaded actuator) that will hold the wastegate closed until the exhaust flow overcomes that spring pressure and forces it open. This spring tension is usually fairly low in stock applications.
Wastegates also operate on manifold pressure that aids the spring in maintaining boost level. A boost controller regulates pressure going to the wastegate and thats how they help control your boost level.
Wastegates can be internal (in the turbine housing itself) or external (mounted to the exhaust manifold before the turbo). The designs work slightly differently but serve the same purpose. Most aftermarket turbo setups utilize an external wastegate, where most stock applications have an internal wastegate.
- Quote :
- that's where you're wrong... Forge Performance has an upgraded wastegte actuator for sale. Yes it's an intregal wastegate, but theirs is stronger, holds the boost better and if you want to up the boost just get a hallman MBC
Did you read what I Posted? Look at the second paragraph ...
"You can upgrade the wastegate actuator. This is mainly to allow the turbo to flow close to it's maximum capacity at high RPM where the stock actuator isn't strong enough to hold itself closed."Upgrading the actuator is not upgrading the wastegate. The stock wastegate has lower spring tension than the Forge replacement and the Forge holds more boost up top because it can hold the wastegate flapper closed at high RPM.
No MBC will help you hold boost if the wastegate can't hold closed. You reach a point where the compressor side can't keep up with the exhaust turbine and boost begins to fall off. This happens because the pressure from the manifold and the spring tension in the wastegate actuator together still can't hold the flapper shut. At this point, the turbo can't spin any faster because the exhaust flow it needs is flowing out of the wastegate port and not around the turbine.
The only way to help this situation is to increase the actuator spring tension since
a boost controller can't increase the pressure in the system ... only limit it.This is why removing the boost source from the wastegate will make you run the maximum boost that the turbo is capable of. The wastegate will stay closed as long as it can and then begin to bleed off as exhaust flow increases.
In short: An upgraded wastegate
actuator will help the stock turbo build more boost at high RPM when the wastegate tries to stay completely closed.
A boost controller will help you control the boost pressure only up until the exhaust gases out flow the compressor.
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