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I was very excited about getting the supercharger system to work properly. The next step was to get the engine management sorted out. I have set up the car to run off the map sensor. As I was running the 272 deg cam with the throttle bodies the map signal was a bit unstable. It was jumping around a bit. This made it difficult to change maps in the right places. You could not see what map site you were actually on. I took a piece of rubber pipe that fits over the vacuum pipe that went to the map sensor and the fuel pressure regulator and added a piece of sponge in that line. This acts as a signal filter to dampen the pulses to the MAP sensor.
The sponge fix was a delicate fix. Too little sponge and the signal is unchanged, too much and the reading is to slow again. I had to play around with the sponge unit until I got a good result. Not to slow reading and not too jumpy. I took the car to the guy that installed the local aftermarket management. He was very good at doing base maps. I did not have a clue what is what on the ECU. I tried to work things out for myself but as I didn’t have the right tools for the job, I just couldn’t get it right.
First, drive as a Supercharged Polo!
After the car spent a day at the tuner I got the car back. This was the first time I could drive the car with the supercharger setup. I was amazed at how strong the car pulled. The car sounded well too. This was a nice sleeper now. If you drive the car normally it sounded like a standard Polo. When you put your foot down the charger kicks in and takes over. What made the system even greater was with the electronic bypass valve I could control the boost with my foot. The boost came in gradually and it felt so linear. Besides the added sound it felt like I was driving a large naturally aspirated car. This is now once again a fun car to drive.
What did the dyno say!
Obviously the next step was to get the car on the dyno. So I could see in numbers what I was feeling driving the car. I took the Polo to one of the local dyno shops that had the most accurate and repeatable dyno’s in Cape Town. They strapped the Polo down on the dyno and did the run…The Polo made 132kW and 243Nm of torque. At this stage, there weren’t that many high power cars around. This was really good power and torque for the setup. Now I was happy!
Having another issue.
I drove the car for a few months like this and the car was very reliable. There were no belt issues, the car was fairly light on fuel when I drove it like an old man :). The winter came and so did the rain. I drove to work one morning in the rain and had to overtake a truck. I put my foot down and the charger kicked in but there was no power gain. The car sounded funny.
I got to work and checked under the bonnet, could not see anything funny. Revving the car the supercharger kicked in as it should. What I found was the bypass valve did not close at all, it just stuck open. I switched the engine off and took the pipe off the bypass valve so that I could see what it was doing. It stood open, I moved the throttles open and closed a few times and it responded again. The next moment it stood open again. I put everything back together and decided I will have a look at it later.
What is the cause, how to fix it!
That afternoon it was nice and sunny and the day warmed up a bit. When I drove home with the car everything was back to normal again, everything worked. The next morning was the same thing again. I found out that the controller I had for the bypass valve was a bit unstable. When there is too much moisture in the air the controller started messing around. I got my friend involved who built the little black box for me. He sprayed the Vera broad that the circuit was built on with an electric sealing spray. Now the tracks are sealed off from one another and can’t short with the moist in the air. That solved that problem.
The biggest problem driving a boosted car is you get used to the power very quickly. It is not long and you start to wonder what can I do to get more power…
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