[leman_opc]

Did some field testing last days.

A couple of words on the car setup: 2.0 lt engine with K04 based stock turbo, boosting 1,5 bar (midrange) and gradually decreasing to 1,2 bar on the redline (presumably due to turbo maxxed out flow-wise). WMI installed some months ago for knock suppression primarily, the map I have on the car (an I'm not able to tweak it unfortunately) appears to be pretty aggressive with 0,9 lambda (13,3 AFR) in midrange (which is also peak torque range obviously) and 0,8 lambda (11,8 AFR) in higher revs. Without WMI I have ignition retards of up to 12 degrees, with a single 0.9mm jet post-IC the retards become sporadic and mostly up to 4 degrees, which I reckon is acceptable. I inject 40% ethanol, 60% water.

The idea is to reallocate some injection to preturbo jet so that the effects on (i) knock suppression effectiveness may be tested (pre-turbo vs. post IC) and (ii) claimed increase of turbo capacity may be estimated.

I made test runs in 3 different setups:
1. Single 0,9 mm jet post-IC. Result: max. air consumption 790 kg/h, ignition retards up to 4 degrees;
2. 0,3 mm jet preturbo, 0,5 mm jet post-IC. Result: max air consumption 789 kg/h, ignition retards up to 8 degrees;
3. 0,5 mm jet preturbo, 0,3 mm jet post-IC. Result: max air consumption 791 kg/h, ignition retards up to 9 degrees in 1st run and up to 12 degrees in the second.

In twin jets setups (2 and 3) the 15psi checkvalve has been attached to the preturbo jet water line, the line to preturbo jet from the tee is also much longer. I verified both jets were flowing normally (controller in the test mode) but would expect in real life preturbo jet starts spraying with a delay compared to post-IC.

Based on above I may say that no turbo efficiency gain have been seen yet, however the detrimental effect on the knock suppression from shifting the injection to preturbo is pretty obvious. It would seem logical to increase the injection post-IC to fight the second (e.g. 0.5mm jet pre-turbo and 0.5mm or 0.6mm post-IC), I will further test this.

I have also encountered that the flow on the twin-jet setup was strange. After a periods of low load (car running but no water injection) when the WMI kicks in I get high flow for a second or so (up to 5 or 6 bars on the gauge), then it gets down to 3 bars and keeps like this to the redline. With a single 0.9mm jet I had generally linear flow increase up to 7 bars with the same SC setting. I will have a look into this as this may obviously affect the results.