Moronic Tuning "Advice" WARNING! (Related to RX7Club)

NoDOHC · 03-20-2011, 07:50 AM

A couple things to mention:

Water and air are both fluids, but the water has much higher density, thus if it remains in liquid form, it will tend to puddle at any change in direction (you will see fuel do the same thing).

The advantage of injecting before the turbo is that the turbo does a lot of the mixing of the water with the charge, also enabling it to evaporate as it leaves the turbo. The goal here is to have the water evaporate, taking heat out of the charge air.

The advantage of injecting post-intercooler is that the intercooler will do much more cooling (as the temperature difference between the charge air and the surroundings is higher than if the water had already been injected). This means that less water is required to achieve the same IAT, meaning that the water vapor displaces less of the oxygen in the intake air and thus more power can be obtained at the same boost level (the volumetric flow rate will remain equal, but the flow rate of oxygen will increase).

I have not seen a study done, but I wonder if injecting pre-turbo does the compressor any harm (high-speed blade contacts water droplet, causing deformation of the blade, resulting in fatigue failure over time).

I know back in the carb days, the blow-through carbs were preferred, as the fuel would erode the compressor over time.

For what it's worth Peter, I prefer technically informative posts over name-calling. It doesn't seem to help anyone's knowledge on the topic to learn about your opinion of the people who posted the information. Let the evidence stand for itself and let people form their own opinions.

03-20-2011, 07:50 AM	#11
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	A couple things to mention: Water and air are both fluids, but the water has much higher density, thus if it remains in liquid form, it will tend to puddle at any change in direction (you will see fuel do the same thing). The advantage of injecting before the turbo is that the turbo does a lot of the mixing of the water with the charge, also enabling it to evaporate as it leaves the turbo. The goal here is to have the water evaporate, taking heat out of the charge air. The advantage of injecting post-intercooler is that the intercooler will do much more cooling (as the temperature difference between the charge air and the surroundings is higher than if the water had already been injected). This means that less water is required to achieve the same IAT, meaning that the water vapor displaces less of the oxygen in the intake air and thus more power can be obtained at the same boost level (the volumetric flow rate will remain equal, but the flow rate of oxygen will increase). I have not seen a study done, but I wonder if injecting pre-turbo does the compressor any harm (high-speed blade contacts water droplet, causing deformation of the blade, resulting in fatigue failure over time). I know back in the carb days, the blow-through carbs were preferred, as the fuel would erode the compressor over time. For what it's worth Peter, I prefer technically informative posts over name-calling. It doesn't seem to help anyone's knowledge on the topic to learn about your opinion of the people who posted the information. Let the evidence stand for itself and let people form their own opinions. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)