|V8 Tuning.....The Inlet|
The inlet system...For tuning this is one
of the most important details of an engine for more power. The inlet is even
more important than the outlet. The amount of air and fuel drawn in at the inlet
stroke determines the amount of power that can be produced at the power stroke.
So what determines how much air and fuel can be drawn in? The engine can only get in an amount of air which equals its capacity..right?? Well not entirely so. It is usually a bit less. There is always some resistance in the inlet piping which increases with engine speed. A good engine usually gets about 70% to 90% of its capacity. The ratio between the theoretical amount of air/fuel and the amount in reality is called volumetric efficiency. So if you add a turbo or supercharger you can put in more air/fuel than the engine's capacity and thus get a volumetric efficiency which is higher than 100%.
As you can see this is quite a list. And a lot to go wrong and thus to be improved upon. Let's see how it works with our SD1.
The inlet opening
The inlet piping to the air filter
Another important point is the way the inlet is formed. When using a straightforward inlet the air will contract while entering the inlet system. If a concave inlet shape is used the contraction will be less or reduced all together.....giving a lot less resistance
The airfilter housing
How much can be gained with a K&N filter? Well the diagram shows
that the K&N filters flow significantly better than standard items. Be careful when replacing
your standard filter for a K&N one. Because the resistance is less the vacuum in the
carburettor will be less at the same air speed then before. As a result your engine
will run leaner. So you have to adjust your mixture. Check the plugs! (see maintenance page).
But this is not all. Because the inlet resistance is less the volumetric efficiency of your engine rises. This means a higher effective compression ratio than before. In the page about basic tuning we already mentioned that flame speed increases with the compression ratio. So decreasing inlet resistance also means increasing flame speed. As a result your ignition can do with less advance. See the ignition page for more details (not up yet).
So you can see just bolting on a K&N isn't all to it. The rest of the engines systems must be altered too to get the most performance. Only with these adjustments can K&N filters give the advertised 5 to 10 hp increases.
Any comments, or do you want to ask or give additional info or do you have questions, just let us know!!