Blower Porting Theory

Blower Porting Theory

Here are some things to consider when porting your blower. This article was brought to you by Jokerz Performance.

Supercharger porting

In February of 2015 I made a post on rotor entry porting. In todays post I am going to clear up how port work effects your supercharger in clarity so that way communities understand fully what is going on.

This post is not guidance , advice and is not applicable to your build at hand. It is a personalized perspective that we formed in order to inform our customers and others about porting in a generalized format. Please contact your tuner, builder, or shop for details on your build.

Why do you port? 

You port to increase the amount of air an item can move or flow. When porting a supercharger the way to increase flow to the rotors consists of two parts. Volume and rotor entry duration. This ends in a hp gain and torque gain to the read wheels

Volume porting 

Volume porting is basically enlarging the inlet housing and creating a larger mass of air between the throttle body and rotor bearing cup. This method of porting is an important part of the port because it helps and supports the second stage of porting at the rotor face. In order to fill the entry point of the rotors you need the mass of air behind the entry point.

Rotor entry porting

Porting at the rotor face is the most crucial part of your port. Coupled with the volume side of the port the amount of material and the shape you provide will effect the power band your supercharger will produce. The profile you choose will determine the powerband you wish to produce. Lots of rotor face duration will create a higher hp level in the higher rpm band sacrificing low end torque. Less rotor face porting creates a better low end power band with a little bit of high end. A proper port designed with both considered will work best when coupled with the superchargers efficiency map, blower rpm range and most users applicable power band. Profile shape will determine how the rotor wash out is controlled. As air enters the rotors the air is deflected by the rotor face and how your rotor face is designed will effect the wash out. So entry into make a HUGE difference in your port work.

Outlet porting

Proper outlet duration porting in relation to the inlet can help move air out of the rotor pack sooner allowing more air to fill into the rotor before inlet has closed itself off. To little is insignificant to much can be detrimental to the power band.

Porting effects on powerband

Im going to try and explain this as simple as possible while trying to be technical and correct in my statements. As mentioned above volume porting is great for all applications as this is just making the housing up to the rotors as efficient as possible. This will seperate most ports as this is the most time consuming part of the port. This will supply the air needed for the rotor entry to do its part. Now for rotor entry portion. Rotor entry porting basically controls the power band you wish to shoot for. As mentioned above rotor entry more or less controls the power band. There is however a crucial side effect of this. By controlling the power band you need to take into WHEN that port starts making power and how much blower speed is needed to get to that power band. For example if You have a standard port then redesign that standard port for a higher hp application when does that new port seperate itself from the base. This is a very very crucial part of the port. The amount of material you remove from the face will effect the amount of power your motor will have to supply in order for you to make hp at x Engine rpm. What we are talking about here is useable and operable power band. If the port only produces a better power band for 500 rpms then port is not done correctly. Now this can be overcome. By spinning the blower harder you can bring that range of power back Into a useable range. Smaller uppers and larger lowers this solves this issue. It also however creates more load which becomes more parasitic on motor. This also becomes a factor for the cooling system but we will get to that later. If you increase blower speed and port duration then you need to supply the air. You can do this with cold air intakes, throttle bodies, and volume style porting. Lets get something straight rotors will move All the air as long as it can be supplied. The problem is we are stuck with inlet shapes, cold air intake shapes, throttle body sizes limited by electronics, the list goes on and on. These all need to be incorporated into a port design because the rotor entry profile you choose has an rpm band that needs to match all those mentioned. Without it all considered you could make hp and tq but how much of that power band is being Used. 500-1000-4500 rpms? All the above effects a power band. We can dial in all of ports within 500 rpm of your shift point making a full useable power band to the application at hand.

Additional effects of porting

Most porting of superchargers requires additional pulley in order to see gains. However a properly designed port will make power from stock rpm to about 10-20 percent increase in blower rpm where from there you choose a more aggressive port in order to finish out the capabilities of the applications power band. You can add More pulley but you will have considered heat and cooling. From there you would max out the inlet per the application limitations as mentioned above with the cold air intakes, volume of inlet, and throttle bodies should effect your port profile. After you consider all that how does your cooling capability apply? Well just because you cool air does not mean the boost produced is efficient. A supercharger needs to operate in its best potential efficiency range in order to make the most hp at x amount of rpm while the cooling system has the ability to cool that efficient air. This makes the supercharger system optimized giving you a full powerband to use and the supercharger should get close to maxing out at your shift range. Failure to do everything above will result in high iat2, broken belts, loss of power down low and up top.

Porting effects on structure 

Porting removes material. How does this effect the surrounding structures. Leaving castings in place will retain the best structural support for long term use. Modifying housing with epoxy and welding have an effect on load capabilities during operation and rebuilding. These structures and their support will be effected by rpm heat and pressure. Not saying failure is imminent but every blower has casting tension and when material is removed completely it can cause case flex in bad places. This is why we try to remain on the cautios side and make as much power with what we are supplied. It has worked for many applications down to 8 seconds.

I hope you enjoyed this post about port work. This is just a generalized post about how we approach our port work at Jokerz. Please consider your port style on your build application.

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