Skoda Rally Blog

If you’re not familiar with the technicalities of motorsport, it’s easy to think that you can “tune” your car any way you like – most rally cars you see seem to have a ‘full on’ engine and the owners have spent a considerable amount of time and money on getting them to the point where they are. For many local and national events, this may be true.

However, for International motorsport the FiA decided that car specifications need to stick to a tightly-defined set of rules, and parts must be largely original or ‘performance’ ones which have been supplied by the manufacturer at some point (it’s more complex than this in reality). When you’re a works team with a large budget, this is no problem – parts supply is no problem. But a few years down the road some of the parts needed to be legal become very rare and therefore expensive. And as technology improves, older cars get left behind with a fixed specification that cannot be changed. And that’s one of the main issues with running the Felicia; the engine which is in the car was old technology even when the car was introduced in 1995, dating back to the mid-1980s (and its heritage goes back a LONG way before then), so it’s relatively unsophisticated (a good thing) and low powered (not a good thing). This would be fine if you had carte blanche to modify the engine as you see fit, but alas this isn’t the case if you wish to compete internationally; major components that you would normally change when tuning the car (such as the inlet manifold) have to be the ones specified in the car’s papers.

Which leaves me with very few truly performance options. So, I need to make the best of what I can use, which in this case is the standard manifold setups that Skoda used and homologated (i.e. had inspected by the FiA). I ran the car with an MPi manifold (standard, from the later cars) last year, and it ran fairly well, but certainly wasn’t quick. And now it’s time to go faster, so all options need to be checked. But checking this is difficult without specialist tools, and it’s expensive to get others who have them to do this checking for you as every possible permutation needs to be tested!

Handily, the internet is full of lots of people with crazy/stupid/brilliant ideas, and one of them is a guy called David Vizard, who I would describe as an old-school tuning guru. His name is synonymous for many with car tuning, and he’s written many books on the subject. I’ll cut to the chase; he outlined a way of measuring the amount of resistance to airflow that components present, for about £20 or so. So I headed off to B&Q, bought the things I needed and then built it. Essentially, you attach your cylinder head to a vacuum cleaner, and measure how much pressure drop there is – the more drop, the more resistance there is.

David Vizard-inspired head flow setup

Here you can see the box (with black pipe to connect to the hoover at the bottom), and the cylinder head, manifold and inlet. The clear pipe goes from a spark plug to a manometer…

Manometer made up to measure pressure change

which shows how much pressure change there is – the more reading on here, the more the flow is restricted into the head.

While this is in no means an accurate, calibrated flow bench, it did show up something very interesting; I have two cylinder heads, and both of them showed no difference when just the bare heads were tested – I was disappointed as one is a very nice job, and the other is near standard. But as soon as the manifold went on, things changed dramatically – the ‘nice’ head showed far less of a loss when putting the manifold on; I can only attribute this to the ports on that head needing to be fed the air the way the manifold does it, as any other changes (such as adding the inlet duct) made the same difference on both setups.

The next step is to make the setup read more accurately; as you can imagine it’s rather course (although the info it has provided has been invaluable), and a piece of equipment to do this accurately is quite expensive (around £400, minimum), so my options are limited at the moment. Just thought I’d share my top quality piece of engineering with the world.