WI on a Saab 9K Aero

[Robert Davis]

Application: '95 Saab 9K Aero (U.S.-spec T5) with aftermarket ECU, 3" exhaust system, and K&N internal filter (stock replacement). Everything else is stock.

I've purchased a WI system, installed it, and am getting mediocre results. It contains a Shurflo 140-psi pump, 1-10 psi pressure switch, Aquamist 0.7 nozzle, anti-drain-back solenoid, relay, LED light for dash, and an in-dash switch for disabling the system.

The problem is that performance is little or no better in its best behavior and worse (lower boost and light misfiring) if the spray is activated too early. At this point I have it set for 10 psi and the performance level is about equal to no WI at all.

I'm getting a very good spray pattern from the Aquamist .7 nozzle, and the system is working very well. In winter the car is a race horse, achieving >20 psi with no trouble at any time, with no WI.

The problem is that the WI is not improving boost at the times I really need it, during summer months when temperatures here in Louisiana are 90?+ with high humidity. If I accelerate from low RPM (~2000) when it has just achieved operating temperature, as when the thermostat begins to open, I get decent boost, sometimes approaching 15 or more psi. At other times when detonation sets in it will boost to perhaps 13 psi, then back off to 11 or 12, presumably a reaction to detonation. It is not very consistent in this regard, but one thing is for sure--when ambient and engine temperatures are hot, boost is radically reduced. Whether or not WI is working seems irrelevant, as I can disable it at will using a swtich on the dashboard, and there is little or no difference on or off. I am using 93-octane (R+N/2) gas, the highest available here, and have tried different brands with no variation.

The WI nozzle is about 12" from the throttle body and is angled about 45? with the air flow. The Saab Trionic system regulates detonation using an ion-discharge knock sensor integrated with the spark plugs, but why doesn't the cooling effect of the WI affect this?

With the installation of the WI I was really expecting boost to climb to near-winter levels (>20 psi) even in the hottest weather, but I'm getting almost no benefit from this addition. What about adding some WSW fluid or alcohol to the mix? Any ideas would be appreciated.