Fitting a Cross flow head with crazy Individual Throttles!

By Clinton HulleyVW Polo Classic Project Car
VW 8 Valve cross flow head
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One day I was on a dyno day at one of the performance shops not far from where I stay. I saw a BMW E36 M3 going onto the dyno. When they opened the bonnet that was the first time I saw individual throttle bodies in a car. Till now everything was Weber side drafts. If you wanted power out of your little 4-cylinder as most golf’s. You needed to through in a 288 deg billet cam and put on a set of Weber side drafts. The mark 1 Golfs running this setup usually made good power and they also did really well on the 1/4 mile.


My mind started wondering….what if I could fit a set of throttle bodies on my Polo? Theoretically, the throttle bodies should be able to make more power than Weber side drafts. The carbs have a choke ring that the throttle bodies don’t have. I was looking to get a set of the BMW M3 individual throttles. They were not easy to obtain and very expensive.

Where to find individual throttles…

After doing some research I found out the Toyota 1600 RXI(43mm butterfly’s) and 1800 RXI(45mm butterfly’s) engines also came out with individual throttle bodies. I found a shop that had a lot of import Toyota motors that was willing to strip off the intakes.

As there were a few of these engines around at that stage a got the throttles for a good price. The next step was how am I going to fit these on my 8 valve U flow head. I thought by myself I am not going to rush into this and I am going to do my homework. Here I wanted to do something special but nothing wanted to go my way. I didn’t want the throttles to be so close to the exhaust manifold.

What to do??

After some more research, I found out that Volkswagen did a Crossflow head on the new generation Volkswagen Beetles. The issue was to get hold of one. There was not that many around and the New Beetle has not been on the roads that long. I found a guy that had one of these head. He didn’t really want to sell the head, but I stayed on his case until he agreed to let the head go.

Can I buy an intake manifold?

Now the next step was to get hold of an intake manifold. I came across a company that did cast manifold in Cape Town and I contacted them. They said that they just completed the side draft intake manifold for one of these heads. I went to them and bought one of the intake manifolds. They had a machine shop so I asked them if they could machine injector ports into the manifold. They were very helpful. So now I had a side draft manifold with injector holes.

I took a piece of 12-millimeter Aluminium plate and machined 4 flanges for the Toyota throttles. I took the cast manifold and machined off the side draft flanges. The newly machined flanges were then welded to the intake manifold. As I am someone that likes to have an engine that looks nice I had the intake manifold polished. You could not even see that it was a welded assembly. Now I had my intake for the throttles. I made the original throttle linkage work on the throttles. I also had to make a fuel rail as I didn’t have a rail for the intake.


The next part was what to do with the head. I took it apart and match ported and flowed the ports. The intake ports on this head is a bit bigger than the standard U flow heads. The head cleaned up very nicely. I took the head to an engineering shop to convert it to a big valve head. The head was at the shop for approx a week.

What happened to my Crossflow head?

One afternoon I got a call to tell me that the head was completed the morning but someone walked into the shop and took the head. Yes, the head was stolen. I was beside myself. How could anyone just walk into a shop and walk out with a head without someone seeing anything? Later that day the owner of the shop phoned me again. He said that he has found another head and I could collect the head to do the porting. The Monday morning after the head is returned he would do all the work again as quickly as possible. From memory, it was about a week and a half later and I had my newly rebuild crossflow head.

I spoke to a guy at the shop where I bought the intake manifold. He told me that he had an 8 valve cam for sale. It was a genuine Volkswagen Polo Cup 298 Deg cam and it was still in perfect condition. I told him that I would bring the money later that day. Stuff was starting to come together. Now I had the head, intake, and throttle bodies. I had a set on ram rubes made by a guy that made beautiful ram tubes for side drafts.

How will I control the engine?

One thing I didn’t think about is what management I am going to run. As the throttles will not work with the MP9 OEM ECU. As I didn’t have that big of a budget I was looking for one of the local Managements in South Africa. I came across an ECU called Mr. Turbo and I bought one of those. I also bought a set of 270 cubic centimeter injectors. I didn’t know if the standard injectors would be big enough. After buying all the gaskets I needed I had everything to do the conversion.

The Friday after work I went to my friend’s house. He lived on a smallholding not far from where I lived. We usually went to his house to work on cars. He had more than enough space to work on cars. There we started stripping the head off the 2-liter sub-assembly. We got everything ready and started to assemble the new goodies on the engine.

More Aggressive cam…More compression?

Because of the 298-cam, I decided to just run a standard head gasket. I would be back close to the 11 to 1 compression ratio. Having the ability to map the engine the high compression is less of an issue than with the MP9 System. I did all the wiring and look at the maps after the engine was fully assembled. Look at it now I didn’t really know what I was doing. I needed to run the Throttle position sensor as the load input. The ECU didn’t want to allow me to do that, it kept on defaulting to manifold pressure input.

I hooked up a tube to each intake runner and connected it to the MAP sensor on the ECU. After a few hours of battling, I got the car running. The engine did not run very well but I could drive it. I drove the car home and thought to myself, what did I do, the car runs really bad. At first, I thought maybe the cam is just way to wild for what I want to do with the car…

Polo running badly…

I took the car to the tuner not far from where I stayed. He said I must leave the car with him and he will see if he could sort the car out. It was about 2 hours later and the guy phoned me back. He said that the Mr. Turbo ECU is just not going to do the job. Contacting the supplier of the ECU did not help either.


The next step was to throw the Mr. Turbo ECU out. Fit a Gotech ECU and get it running. They were a bit more expensive, still a local ECU but they just worked. A lot of people were running the Gotech ecus at this stage. Later that day the tuner phoned me and said I could come to collect my car. He did a base map on the car. The car still needed to be turned on a dyno, but the car is driveable.

Happiness!!

I went to collect the car. The car sounded like a standard car idling, I could not believe it is the same car. Driving the car home was a pleasure. The first time I put my foot down the car had a nice roar. Acceleration in this car was just amazing. This became a really fun car to drive. I was well impressed with the sound and performance of the car. I booked a dyno so that the tuner could finish the mapping in the car. After mapping was completed they did a power run and the car made 121kW and 220Nm of torque. This car was all about fun…


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