Subpage of MembersPage/MarcellGal/PowerAndTraction

We want water injection on this engine.

I filled a 8L pressure tank (rated for 8bar, -10C .. +99C) with water. It fits easily in the empty space of audi's original air-filter. Flowrate will be controlled with PWM valve, using the boostalt output (1.1.50 firmware).


My proposal is to use empty tank(7.5 or 10kg) for lpg(propane/butane) for home.


Fill 80% of tank with water/methanol and add 10-20g of LPG(propane/butane). You can do that as connecting tank with water to tank with lpg(tank is upside down) and opening valve for 1-2s. So you will have pressure depending only of temperature


Just add 3-5bar regulator(not circulate regulator like gasoline regulator on engine) and petrol injector(many injectors can work with methanol).

Only problem with this solution is max tank temperature(100C is max), so engine bay isn't good place for tank.

What do you think?

Sounds good.

For the tests we want to use engine bay, and filling with 6 bar before dragrace is perfect. We should see significant difference soon with warm airtemp, engine should tolerate more ignadv (at least with 95 RON gasoline) with water.

Water level sensing

A system that wants to be foolproof (it won't be) absolutely needs H2O level protection.

First, this system will likely use pressurized tank with pressure sensor. Pressure sensor is good anyway, for compensation (flowrate is normally proportional with sqrt(pressurediff)

Getting water pressure seems to be the expensive part of WI. Not just expensive, but also other sources of risk. The pressurized tank is cheap and failure rate is relatively low.


Wikipedia writes that besides some alcohol antifreezer, some oil is often mixed (emulged) into the water (not always easy, ultrasonic mixer ?), for anti-oxidant effect to protect injectors

Pressurizing water or windshield washer liquid even away from home

If you find a small 10bar electric pump, let me know


Filling the pressure water tank

Pressure is up to 4.8bar at the moment (the pressure tank is rated to max 8bar). For some reason it's not even half-filled at this point (can be measured on a baby scale).

I experienced that it cannot be filled via the reverse osmosis filter, because the reverse osmosis filter needs 1.7 bar pressure across it ( 2.8 bar pressure always enough with appr 10L/h according to it's book)

But the simple 20um + carbon + 5um water filter should flow sqrt(pressure diff). Maybe I just didn't wait enough.


I'll need to do flowrate measurements with nozzle, knowing pressure diff and PWM. And VBATT, as VBATT matters at low PWM duty. VBatt makes no diff at 100% PWM duty

TODO: upload image to

The cooler is not ordered yet

To get water into the engine reliably, one needs


There are 2 ways to pressurize the system


Good nozzles are essential to

Nozzles must inject water after the charge cooler, but before the throttle.

It is generally a bad idea to inject water before the charge cooler. Because water cools the charge, injecting water before the charge cooler makes the delta-T smaller, thus the charge cooler can release less heat (bigger charge cooler needed for same effect).

While it is a good idea to spray water to the outside surface of the charge cooler, it is dumb to spray water to the inside surface. So we will certainly inject after the charge cooler.

Number of nozzles

Water mass - compared to fuel mass (or is the literature usually volume/volume?)

10..15% is the minimum, up to 30% might make sense

I have appr 180L/hour available total fuel injector capacity (with 200+ L/h fuelpump). So 20..40L/h water would make sense

Not sure about optimum though (not possible to fine-adjust anyway)... a 0.35 and a 0.45 mm nozzle would probably do it. TODO: more investigation