In order to maximize of effect of water/methanol injection, the rate of delivery should be closely related to the real time engine operating parameters. The first objective is finding a signal that is comparable to the engine's cooling/octane demand at the exact moment in time.
Finding the signal to match engine's demand:
Load sensors such as throttle position, mass air flow and MAP sensor are a prime signal source of engine load. But without RPM reference, these sensor are only representing only a two dimensional impression. For example, MAF sensor without RPM reference only measures air consumption, regardless of gearing or boost pressure. The engine could be cruising at high speed (less stress) or it can be travelling at 20mph in the rally stage under extreme load and high temperature stress. The same chuck of MAF signal cannot represent the engine running conditions.
Why tracking fuel injector duty cycle:
With the help of the modern engine management system, the same chunk of MAF signal, coupled up with a bunch of signals gathered from sensors such as air temperature, coolant temperature and EGT (interpreting the lambda probe's heater element) and of course, engine speed. It will make an informed judgment when to add or trim fuel depending on the real-time operating environments. The final decision made by the management will be reflected by the duty cycle of the fuel injector. The HFS-6 uses this IDC signal to meter flow.
Picking the correct delivery method and hardware to complete the task:
We have ruled out the variable pump-speed delivery system for a numbers of reasons. Due to the inertia of the rotating mass, variable pump-speed system is not responsive to the fast changing engine load at various throttle openings and engine speed changes, especially during gear shifts. Flow range is narrow due to limited pressure span. It requires 4x the pressure change to produce twice the flow change. Poor atomisation and pulsation system pressure at low pump speed is an inherent characteristic of such a system. Consistent droplet size is vital to inlet cooling and even cylinder distribution.
HFS-3 chooses the well established method for fluid delivery:
Decision was made to employ the tried and tested delivery system similar to a fuel injection system to meter fluid flow. A 150W heavy duty pump is made specially for us by Shurflo USA. Equipped with three 125psi internal by-pass valves provides the system pressure. A surge arrestor/accumulator refines the low-ripple further. A high-speed stainless inline valve completes the line up. The valve is capable of flow over a litre of fluid at 125psi. A dedicated controller reads the fuel injector's duty cycle % and channels it to the inline valve.
A dash gauge displays the flow information from a digital turbine flow sensor:
Failsafe is serviced by the Aquamist's proven DDS3 module, designed to detect clogged nozzle and cut hose. Two switched outputs provide the necessary interface with device such as boost control valve and map switch equipped engine controllers.
HFS-5 meets all criteria of a reliable and highly precise fluid delivery system:
We believe the HFS-5 is the only fluid delivery system that meets the minimum requirement for achieving full integration into your tuning programme with absolute precision, tracking the fuel delivery is the most reliable method to meter your water/methanol flow accurately under the whole engine operating range. Anything short of this means having to tailor your fuel map to compensate the irregular fluid quantity ingested into the engine.
Should you decided not to mirror the fuel flow in your future upgrade programme, the HFS-5 system can read a PWM output from a third party engine management controller so a custom water/methanol map can be created.