[PuntoRex]

Been using the pre-compressor jet installation for a while, I did suffer from the surge problem in higher gears, especially 5th in the mid rev range on the highway. Tuning up the injection point (10psi to 12) helped some, but would suffer from the other problem - midrange det.

The weather was chilly these days, and my car det! It never act like this. I suspect that maybe the partially vaporized water from the compressor oulet condenses back to liquid within the cold IC, then the heat is back. And the liquid water in the thin IC passages is definitely not a good thing. While slightly later injection point provides insufficient in-cylinder cooling after all these chaos. It's just not right on time, especially in this fixed w/f 2D system.

So, pre-compressor WI should not be too early & too much. Especially with an upgraded compressor wheel or bigger turbo. I think this is for sure.

I managed to make a system which turns on pre-compressor jet a little later than the main (the pre-throttle) one, and one additional jet also on pre-throttle for slightly larger w/f ratio at the first injection stage. (as above)

Using the 2D's injection duty cycle voltage output as the switch reference, i.e. 3V as 60% IDC. I think this is a good point for my car which rushes to 80% at red line.

By a comparator circuit, I compare the IDC related voltage with a pre-set 3V reference, then drive a 3way/2position solenoid valve to guide the flow.

There're 3 jets:
A- main jet, running full time, pre-throttle
B- mid-load jet, pre-throttle
C- high-load jet, pre-compressor

My car is running at 20psi boost max. At the 1st stage, begins at 8psi (about 40% IDC on my car), A+B are working, for maximum in-cylinder cooling. 2nd stage, begins at 60% IDC, A+C are working, for improved compressor efficiency & less det control needs.

By doing this, it avoids the surge line on the midrange operation & stretched the choke line on the hi-load/hi-flow situation. Effectively, it extends the overall area of the compressor map, I believe.

I just got it done today (2:30 am). It's running very well in the first impression. Earlier injection point makes the car livelier on part throttle acceleration & eliminates the midrange det. 5th on highway speed is now smoother on small throttle inputs. WOT to the red stays perfect as the previous full time pre-compressor jet setting. It's running in a stretched compressor map. What a treat!

It's a good mod, worths a try.

Next, I'll try fine-tuning the stage 1-2 switch point & several different jet sizes to play with a two stage w/f ratio map....