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Old 04-12-2017, 11:17 PM
rotrex rotrex is offline
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Join Date: Jan 2014
Location: Germany
Posts: 187
Default Re: E46 M3 WMI Design

Sorry,
but i'd not add 60% power without retuning.

50:50 mix by weight is the easiest to tune.
You nozzle locations will work. Just place them dead on top of the little runners in line with the fuel injectors.

Regarding injector size, Richard's rule of thumb works well. Inject some 1.5ml/min per HP. For you that ends up at some 1000ml/min at full chat.
The Aquamist 0.5mm checkvalve jets should work well.

Knock suppression happens to a significant part through mist being present near the edges of the combustion chamber. This is where it knocks the most as shockwaves hit their reflection from the cylinder wall leading to peak pressures. If the mist is non-uniformly introduced into the chamber, it does not get to all the edges, especially front and back of the cylinder well. The spray direction and location should resemble that of the fuel injectors. As you cannot point towards the intake port like a fuel injector, spraying perpendicularly downwards works well enough.

This picture illustrates a typical fuel flow from a port injection engine. Fuel nicely spreads over the front and rear portion of the intake valves. you need to maintain that balance.
Injection from the bottom or the side causes the spray to only partly fill the chamber. Only from the top, the spray has to take the least turns and covers the intake valves in the most uniform way.



The rest of the fine mist helps reducing peak temperatures during the compression cycle and while the flame front runs across the combustion chamber.

Ignition timing will have to be significantly increased with that amount of mix being injected. With pure water even more so. Flame initiation and flame propagation speeds are reduced in the presence of water.
Higher boost will partly compensate for this.
You will also have to pull some fuel injecting significant amounts of 50:50 mix.
The engines commonly like to run at lambda 0.75 to 0.9 under water. Any richer than 0.75 and often achievable power drops.

If you inject much less, it also has much less effect.

These numbers of 100% water to fuel came from WW2 experiments. The tractor pulling guys use it, but for the road, it is impractical. It would only be worth the trouble if you would run way more boost than what you anticipate, e.g. 45 PSI or higher.

Regarding the numbers and their cooling capacity. These numbers are only realistic if all the fluid evaporates. Water evaporates really slowly, even in a combustion chamber. Droplet lifetimes exceed 10s of milliseconds in a cylinder once the droplets are bigger. This is why direct port injection with a good injector position works so well and why nozzles in front of a curved intake manifold have so little effect. The droplets hit the walls in the turns and form a stream of fluid. This passes right through the engine.

The Aquamist failsafe systems with flow sensors work really well. You can have the HSF controller open the boost control valve of the waste gate dropping boost to spring pressure.


Just read the thread "Questions on my direct port meth setup" a few posts down. He applied some of the above with great success (=power) in a Mitsubishi Evo in Singapore.
He gained 132HP at the wheels and has now more than 620HP a the crank. He runs 30PSI on track. 4x 0.5mm jets.

http://www.youtube.com/watch?v=uD8Xq8RF_qM

Your engine is pretty much a 50% bigger version due to 2 extra cylinders. But you have to tune. Going untuned from 500HP to 800HP will very likely blow your engine.

Last edited by rotrex; 05-12-2017 at 12:05 AM.
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