Does Supercharger Need Blow Off Valves? ( Vs. Wastegates)

Generally, a supercharger does not need blow off valves or wastegates.

A supercharged engine is powered by the car’s engine and uses forced induction that redirects pressure to the combustion system. It, therefore, does not need a blow off valve to reduce excess pressure. 

Although some supercharger like Centrifugal superchargers can use blow off valves because they work similarly to a turbocharger.

Personally, I have had a supercharger installed on my car and observed an increased horsepower at a low rpm boost. I must say it is pretty awesome! It gives my vehicle consistent power with no lag.

People looking to have their engine supercharged have a common question: Do superchargers need blow off valves? I hope to clarify some myths and truths about superchargers in this article. Do have a great read!

Blow off valves are not required for a supercharger, except when used with a centrifugal supercharger. For any other supercharger, blow off valves are unnecessary and can be avoided.

Superchargers have an incorporated bypass system that helps them regulate pressure. The bypass system redirects air around the Supercharger while the car is running, which is reliable and improves fuel economy.

In addition, with the supercharger bypass system, when power is needed, all you need to do is step on the throttle, and the bypass closes, which gives you the extra power it needs.   

It is essential to know that if you are using a centrifugal supercharger with a blow off valve, it is crucial to have a mass air meter installed in your vehicle.

If your centrifugal Supercharger does not have a mass air meter while using a blow off valve, your vehicle may have a problem performing.

The mass air meter has a sensor that helps vehicle owners determine the airflow rate into the combustion chamber.

Although it is unnecessary to have a blow off valve on a supercharged engine, it is possible to have a blow off valve on superchargers.

You have to have a supercharged engine for this to be possible. This type of supercharged engine is similar to a turbocharged engine; this is why it can accommodate a blow off valve.

On regular superchargers, blow off valves are completely unnecessary and cannot be installed.

Centrifugal supercharger work similarly to a turbo and can use blow off valves.

You can only adjust blow off valves installed on a centrifugal supercharger. Below is a list of steps to adjust a blow off valve mounted on a centrifugal supercharger engine:

1. Start with adjusting the blow off cap. This will enhance the spring force on the piston.
2. Turn the cap in a clockwise position as instructed on the cap of the blow off valve. 
3. To reduce the spring force, you can turn the cap of the blow off valve anti-clockwise.

The bypass valve is not required for a supercharged engine but can also be used if you feel it is needed. 

Note: I am talking about bypass valves here (not blow off valves). Don’t confuse them.

Supercharged does not necessarily need a bypass to function, but it could greatly benefit installing one in your vehicle. The bypass valve is also known as the pressure relief valve and can be a part of the oil filter. 

Also, the bypass valve serves the primary function of preventing oil clog or oil thickening. When the oil begins to clog or become too thick, it gives way to bypassing the oil filter using a center tube. The oil is then directed to the engine for proper use.

You can test a supercharger bypass valve by carrying out the following steps:

1. Detach the vacuum hose from its nipple
2. Find a 4mm vacuum hose
3. Connect the new vacuum hose to the nipple
4. Try blowing and sucking air into/from the valve
5. If you succeed, then the bypass valve is faulty.

The bypass test ensures that the bypass control opens immediately after the inlet valve expander closes. If the test fails, the vehicle can not receive optimum control response from the bypass valve. 

The expander shutdown can affect the pressure at the regenerator outlet, affecting the supercharger and then the engine itself.

The Supercharger does not require a wastegate to function correctly because there are no exhaust gases involved. 

In turbos, the wastegate gives way for the exhaust to bypass the turbine wheel, which serves as a regulator to the charger. 

It is not needed in a supercharger; this is because the Supercharger makes use of a crank pulley and has no exhaust system, which makes the wastegate system of no use to the Supercharger.

Although, there have been some successful applications of wastegate on the Supercharger, especially the centrifugal Supercharger.

Wastegate is not required for superchargers. It’s primarily used for turbos.

A wastegate can not be used on a supercharger as the superchargers do not need a wastegate to run. 

Also, there is no way a wastegate can be mounted on a supercharged engine. A wastegate is useless to a supercharged engine because it does not use exhaust gases. 

Superchargers compress air from the atmospheric pressure; this allows more air into the engine. On the other hand, the turbocharger uses exhaust gases made from combustion. 

The wastegate is another medium put in place to regulate pressure in the engine. It is done by bypassing an excess amount of exhaust gas from the turbine wheel. 

How does this work? The wastegate is like a disk-like object that closes against the excess gases, thereby redirecting these gases to the exhaust flow.

The wastegate disk is closed, and the engine can reach an enhanced potential. The wastegate is best suitable for turbochargers, but people have found ways to maneuver the wastegate system to best fit their Supercharger.

The wastegate is of two types, the internal and external. The internal, as the name implies, is located within the turbocharger. It redirects exhaust gas to the exhaust flow before passing through the turbine.

In contrast, the external wastegates are separate from the turbocharger. What this does is that it links gases to flow down the exhaust pipe, which can also increase the turbine’s performance.  

The blow off valve looks similar to the wastegate, but they both have different jobs. They are both located in different parts of the turbocharger.

Blow off valve is located at the intake part of the turbo pipe, although just like the wastegates, the blow off valve can open and close to let out pressure from the turbocharger. 

The primary job of the blow off valves is to make sure the intake part of the turbo plumbing tract does not back up; if it does, it may cause a malfunction in the compressor anytime the speed of the engine changes instantaneously. 

Although, the wastegate is of two types, which has been previously mentioned as the internal and external wastegates. The external wastegate can be found at the exhaust port of the turbo pipe, also called the hot part, which is at the middle of the exhaust manifold and the turbocharger turbine wheel. 

The blow off valve and wastegate are both made to work perfectly with the turbocharger. It is also to note that not all turbochargers require the wastegate.

The same applies to the blow off valve; not all turbocharged engines may require a blow off; some use bypass, also called the diverter or recirculating valve.

Most turbocharged engines come with a blow off valve.    

Read: Which Is Better: Supercharger or Turbocharger?

I conclude by saying that the supercharger is a great way to increase your car’s horsepower and boost its performance. However, they do not necessarily need a blow off valve. 

Blow off valves are not required for a supercharger, except when used for a centrifugal supercharger. It is unnecessary and can be avoided.