Volume 2 Issue 3 - Diesel Articles

Pre-Turbo Diesel Water Injection

Snake Oil And Water Don’t Mix

Terms like Nitrous, Super-Charging, Wastegate and other hormone-inspired phrases, leave the topic of Water-misting a little... dry; uninspiring to say the least. Water is not a fuel. By itself, water does not burn, dissociate, or otherwise directly increase engine power or fuel economy. But perhaps water does increase engine efficiency and fuel economy when it is used to eliminate or reduce waste heat processes that convert otherwise useful engine power into non-useful heat. Trust me, this heat, wherever it is created, has pump fuel as its origin energy source. That heat is fuel wasted that might otherwise go to propulsion.

The turbo is a major source of this heat. Whatever we can do to reduce heat manufacture during turbo compression will result in better fuel economy and lower exhaust gas temperatures (EGT). No snake oil claims here, just simple thermodynamic facts of life.

In this article, we will look at the facts behind the merits of pre-turbo diesel water injection (PTWI) as a pre-emptive cooling mechanism: a means to tame that waste heat mechanism and direct that energy to the wheels.

The Power of Disappearing Water

Your body is an engine: an organic power plant. How quickly a large room goes up in temperature when a crowd of people pile in. Water is our coolant. If we could not sweat, our temperature would never be held down to 98.6ºF. Water is essential to heat control for all life and living things. So how about applying this power to an overworked diesel engine?

One day, I was towing on an eight percent grade, headed for a downpour. I was listening to my fan roar and watching my coolant temperature rise. The rain lasted maybe 30 seconds, but 15 seconds in, I noticed a funny thing. My fan had quit running and my temperatures were near normal. Sure enough, as I exited the shower, the fan and the temperature spikes all began again. There was no question that the rain had effectively cooled my engine – if only for its brief duration.

Something similar happens to my body when I cycle in the desert. With its eight percent humidity, outdoor desert activity at 112ºF is lip blistering. Heat stress can quickly turn into fatal heat stroke as quickly as four hours after the onset of heat stress symptoms. On non-monsoon days, I pedal through this near lack of humidity and 112ºF in a white absorbent cotton long sleeve shirt. I carry two liters of water on my back and I can go through most of it within two hours. At the first sign of nausea or weakness, I get wet, no delay. Air conditioning on the fly: and it is amazingly effective.

I was deep into the Sonoran Desert on my mountain bike at 108ºF when a monsoon storm came in from the East. In the distance, a wall of dirt could be seen advancing toward South Mountain and the breeze was whipping up.

“This should be a treat,” I thought to myself.

I had seen it many times, but usually from the radar display. This time I was caught out. Soon, wind-driven dust filled my eyes. The wind eventually gave way to rain: it came down so hard it hurt. I circumnavigated the lower relatively dry washes – which were filling up fast – and narrowly escaped being stranded; getting across the main wash before it flooded. By the time I drove through the final mile of water crossings, the storm had nearly passed.
Prideful and tattered, I arrived home to see my neighbors looking skyward from safely inside their open garages.

“But it’s a dry heat!” I yelled sarcastically, with arms spread like a stage win at the Tour de France.

“Experimenting with the meds again?” they replied.

I stepped into the shelter of my house to ponder the cooling power of water that I had just witnessed firsthand. When I had started my ride, it had been 112ºF, intolerable except for the water I had ported with me: now it was 86ºF and I was shivering. A 26ºF drop in less than one hour. Why?