In a forced induction engine (turbos, superchargers and twin chargers) and to some extent a NASP engine with a high compression ratio you have the ever present risk of detonation. This is where the fuel prematurely ignites typically causing major engine damage.
When adding or increasing the amount of air going into the engine you have an icreased risk of detonation. One solution is to use a higher octane fuel because it will be more resistant to "knock".
More professional engine buildings are looking to the benefits of water injection. Simply put the water dampens the fuel air mix allowing it to resist detonation for a longer duration.
Ehtanol/water mixes are sometimes used but for the purpose of this article we shall focus on water injection.
Water can be injected at any stage along the intake. Some proponents of water injection insist that it is better to spray this before the compressor and allow the water to better vapourise, some insist that it is sprayed just after the turbo and there are also fans of direct injection at the point of fuel delivery.
Each system has is merits and drawbacks and depends to a large extent on the engine.
A crude setup can deliver a set amount of water each time but ideally you will need some form of engine management to match the fuel and water delivery to allow for the optimum settings and benefits to be obtained.
A water injection kit can be purchased now from many motorsport retailers and these typically come with everything you need.
Some water injection systems use your screen wash reservoir but ideally you should have a separate water reservoir with a level warning device fitted as some screen washes contain undesirable elements to be spraying into your engine.
Water can cause corrosion so it becomes essential to properly maintain your engine and the intake will ideally need to be periodically removed for inspection.
If the water reservoir dries up then you will risk engine damage unless the fuel and air mixture is reduced.
In addition to the extra detonation resistance water injection will provide a cleaning action and help to remove carbon deposits from the engines valves and cylinders keeping the egnine in peak condition.
I have yet to be fully conviced that the merits of water injection outweight the potential problems. Considering a properly designed and built engine with lower compression pistons will suffice it does seem a bit of a bodge. However in high stress ultra high performance settings it gives an opportunity to release a little extra power from the engine.
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