[Richard L]

Hello John,

I like to point out the conclusion of the HSV not handling the frequency is quite misleading, here is my approach to the situation. The HSV's frequency response is almost identical to the WRX fuel injectors, if not slightly faster and higher flow.

Your WRX, an unusual approach to the norm - EMS-T3 is a complete takeover as I can see . Most people will be happy to buy a read-made (utec) or semi-made (reflash) package using existing downloadable map or asking a tuner to map it for them. Unfortunately 99.9% of the tuners out there are not adventurously enough to approach WI head-on, some use it as a safeguard for bad fuel and some just dis-approves it outright.

Injector speed: all 16 ohm fuel injector (wrx/sti) has an average opening and shutting time of around 2ms at 12V, the aquamist HSV is no different -this is not a design fault - it is to do with limited energy feeding into the coil to perform a mechanical action. The amount of energy applied to the valve is limited by voltage and coil impedance (resistance). As energy is power over time (V^2/R).

Assuming your are tapping into one cylinder of the T3, running sequential injection. At 6000RPM (100Hz), one of your fuel injector is firing at every two engine revolutions or an interval of 20ms (50Hz). The control-able range is between 2-28ms (taken into account of opening and shutting time). I cannot see any problems for the HSV or your injectors to run out of injection time. So far so good.

The main perceived problem is not the HSV unable to run fast enough but out-of sequence of the induction phasing intervals. In other word, the HSV is firing in phase with one injector and no water for the other three cylinders. This conclusion may hold true if the water jet is close to the inlet valve of the plenum chamber.

Let say if you place the water injector before the intercooler and immediately after it, the water droplets will take sometime to arrive at an individual cylinder, after passing through the satellite distribution chamber. The "no-water" gap is no longer clearly definable. Further factors such as rate of evaporation of drop size travelling at different speeds, rate of evaporation in the inlet tract and some speed reduction of the drop hitting the wall of the inlet tract. My conclusion is that it will not be a problem triggering the HSV with pulse from one injector. If you are still concerned about cylinder distribution, place two small water jets at few inches apart so that it will have the same effect of "filling-up" the gaps. One good method is placing another small jet in front of intercoolern and one after.

Your second choice of using the GPO - no problem at all - run at a fixed frequency of 32Hz or 64Hz, the HSV will deliver water effectively and evenly across the entire RPM range.

Why not running both (your suggestion) if you still have concerns, two HSV firing at opposite cylinder phase- intervals - cheaper to phase the mechanically (not bad) than electronically.

We need to talk about the faulty diagnostic functions you can perform with the GPIs later. If you are happy with my reply and would like to add some comments.

Even at 8000RPM, the inteval of the fuel injection pulse is approximately 14ms. The HSV will handle that with ease.