Looks like I am getting Somewhere!

By Clinton HulleyVW Polo Classic Project Car
Great idea
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The Polo was standing for about a week now. I was looking for ways to get to the boost levels I initially saw before the belt rip itself to pieces. 2 bar gauge boost made me very excited about the project. This meant I could get decent power if I can get it right. At this stage, I knew more boost is more power but did not know how much more power.

How do other people do it?

I did some research on how the supercharged V8’s in drag cars drive there superchargers and saw that they run tooth belts. So I started to scheme how I am going to drive the supercharger with a toothed belt. I got a belt spec S8M by 30 millimeters wide. The next step was to get pulleys made, I got some pulleys made by a local machine shop. This was a nightmare by itself as I had to wait like 5 weeks for the pulleys to be made. When I got the pulleys I was a bit disappointed as the pulleys were extremely heavy. The crank pulley was heavy enough that you could use it as a flywheel.


The next Saturday I whet to my friend’s house to go fit the new pulleys and belt. It was a few hours of work. The supercharger had to be stripped out to be able to change to the toothed pulley. Got everything back to where It was the night we first started the car with the supercharger on.

Not working like I thought it would…

I started the Polo, put the belt on the supercharger was screaming. The groove profile on the pulley wasn’t machined accurately. The teeth of the belt were rubbing as it entered the groove on the pulley. It was making a terrible noise. I revved the engine a few times and I got the 2 bar boost on a good rev up. The car had a really unique sound to it. I had the car idling for a bit and just heard a clapping sound. Suddenly the car sounded like a standard car again. The whining sound stopped and the air blowing sound was also gone. I quickly switched off the car and found that there was nothing left of the toothed belt.


I felt the teeth on the pulleys and they were as sharp as knives, no wonder the belt didn’t survive. It was so disappointing that the fix that I waited for so long did not do the trick. I decided to give up on the supercharger setup, so I stripped all the supercharger bits out of the car and threw it into a box. The head came off and I reverted the compression back to standard. I also fitted the 298 deg cam back into the engine. Now the car was back to original throttle body spec. I am not someone that easily gives up so I started to think again about what I did go wrong.

Back to the drawing board!

I did some research again on supercharger setups on the internet. There I found a document on the G60 charger set up on the old Volkswagen Scirroco’s. They had a bypass valve on the throttle. When the engine throttle is closed the bypass valve is open. The boost just bypasses back to the intake of the charger. This unloaded the charger and basically unloaded the belt.

I designed a nice plenum box that could bolt onto the front of my throttle bodies. This box had a nice volume to it. On the side of the box, I mounted an electronic throttle body. Not being in a hurry I slowly started assembling the parts I needed. I decide the ratio I was trying to run with the charger is just insane, it will never work. The SC14 is a nice little charger but spinning them to fast the drag and losses on the charger is just insane. It gets to a point that the power you gain just gets consumed by the load of the charger. In the end, you don’t gain anything. You may even sit with less power than you started with.

Fitting the supercharger clutch back on?

I took the standard Clutch pulley for this supercharger and machined extra grooves into it. The standard pulley was for a PK5 multi-groove belt. I changed the pulley so that it could take a PK8 Multi groove belt. I fitted the clutch system and pulley back on the supercharger. Now I could run the standard crank pulleys on the engine and run the supercharger with a PK6 Multi groove belt.

The next weekend I took the head off once again and fitted the thicker head gasket on the car and also the 272 deg cam. I got the car running as smoothly as it could with the throttle body setup. So now I would drive the car with the 272-cam and the lowered compression. The car was a bit underpowered but this gave me a chance to develop the supercharger system.


I made an intake pipe for the supercharger so that the electronic throttle meets up with it again. If the supercharger is switched on and bypass throttle open, the air would just bypass back to the intake of the supercharger. So it recycles the air. At this stage, I assembled all the mechanical bits on the car and the car drove really well with the supercharger switched off. Now I had enough time to look for a solution to control the supercharger and the electronic bypass valve.

It felt that I achieved something as the belt was staying on the pulleys and the car was quiet. It was the perfect sleeper. Now it was just sorting out the electronics.


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