What does water injection actually do?


Pro Tuner
Staff member
2002 Clio 172
I've been wondering about water injection.

People add it to their projects, but what does it do? Surely water doesn't mix well with fuel or even burn?

I can see why you'd spray it on an intercooler for example but why on earth would you inject water into your engine?

It is a thing @Lunchmoney

Water injection slows down the burn, so it can reduce the risk of knock in highly tuned engines. It's similar to running higher octane fuel in it's effectiveness.

In my opinion it is a bodge, a good knock sensor, setting the correct compression ratio and adequate boost.

If you are injecting water and methanol it makes sense as this can help raise power, again you need to keep the mapping spot on.
IMO water injection can be dangerous IF there is a leak in the system or if it became faulty over time and failed to switch off or leak when parked as we all know water can't be compressed and could lead to costly repairs.

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