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Discussion Starter · #1 · (Edited)
So I ventured out the 900 workshop into the performance forum, where I don't have any business being, of course.

And I'm reading and I find out about the BOV thing and this water injection thing...

Silly question #1: What is a BOV and Water Injection?
Silly question #2: What are they used for?
 

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There is no silly questions, only silly answers :D

BOV= Blow off valve! - Has the same funktion as your by pass valve! It lets over pressure from the turbo out, when you close the throttle! So the pressure dont back fires in to the turbo!
A BOV is an open one. You will hear the turbo boost get out!

Water injetion is to get more proformance out of your air/fuel! It helps compress the air and fuel more! = Better fire!
 

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Injecting an atomised mist of water into the inlet removes heat. Since the heat is removed when the water phase changes (changes state, ie: water to gas), the location of the water nozzle determines what exactly is cooled.

Fit the water nozzle before the intercooler, and the water will phase change in the IC, thus mostly removing heat from the charge air. Inject water after the throttle-plate and the change will occur mostly in the combustion chamber, thus removing heat from there.

Alex used to run his car without an intercooler (and still got 240BHP :lol: ) but with water being injected just after the turbo compressor outlet. The water changed state in the inlet tract, mostly removing heat from the charge air.

Most OE fuelling systems inject more fuel at high engine loads and speeds. The fuel is used to cool the combustion chamber. However, fuel changes to a vapour at a much lower temperature than water. That means it's less effective at removing heat from the combustion chamber than water.

That fuel-rich condition reduces power because a rich air/fuel mixture burns slower than a lean mixture.

The result of injecting water allows us several benefits:
  • A cooler combustion chamber and charge air, which means less chance of knocking or pre-ignition. This allows us to raise boost levels (providing the turbo compressor is still efficient at that elevated boost level) and/or to advance ignition timing.
  • We can safely lean out the air/fuel mixture a touch, giving better torque and thus power.
  • We get more torque and power anyway because the charge air is more dense since it's cooler.
The benefits really are cyclical. Since the charge air is cooler, it's also more dense so we have more oxygen to burn, which needs a dash more fuel. How you use the benefits depends on the car's setup and your performance goals.

You could use water injection to give you a safety threshold against knock and pre-ignition, or to push performance of the engine further without that safety net.

Phew... I've never had to explain water injection before, and TBH my knowledge is only that of a novice so apologies for any mistakes ;)

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