reply to post by h3akalee
I had a water intercooler button on my Subaru WRX STI. It shot water into the turbo when i pressed the button increasing the power of the vehicle. In
basic term's i beleive the water hit the turbo evaporated creating a pocket of much more dense air that was then forced thru the turbo.
I was not there. I should not doubt it was as reported. But I have gone to the Subaru website to find information on this feature. The factory
installed water injection for the WRX Boxer Master 4 engine. It was not mentioned there. To see more on the WRX engines go to a Japanese website:
CONCLUSION. The WRX engines offer both turbo charging and genuine supercharging via a positive displacement compressor most notable here in the Rootes
type employed by Detroit Diesel for nearly a 100 years.
Some turbo chargers use oil cooling and others use water. This relates to the impeller which in a turbo may spin in the 70,000 rpm range. When the
engine is shut down, some time may pass before the impeller stops turning. The torus - the spinner part of the impeller is in the exhaust system - and
gets very hot. It turns the turbine (other part of the impeller) which is in the fresh air system. During the slow down time period the turbo’s
bearings are put at risk for overheating. Therefore, some means of cooling the turbo’s bearings after engine shut-down is desirable. Usually water
or oil is used. See Note 1.
This heat control technology is not required in the case of compressors - a supercharger as opposed to turbo charger - because those stop running when
the engine stops. Eaton makes a lot of that type here for use by Ford and GM. Another PD supercharger was made for the truck engine by Detroit Diesel
- GM - which began life as a 2 cycle engine. To make it go, it employed a Rootes type PD - positive displacement - supercharger. That featured 2
closely fit rotors or meshing blades and was powered by belt drive off the crankshaft.
Various sizes were made and are known by the engine size they were first meant for, 6-71, 8-71, or 6-91 and 8-91, which mean the number of cylinders
and displacement per cylinder. Detroit Diesel also made a V type engine, as in 6V-71 or 6V-91. The “V” referring to the engine layout as opposed
to the in-line engines without designation. Thus a 6-71 displaced 426 cubic inches (7 liters) and a 12V-91 had 1,092 cubic inches (18 liters).
As for water injection. The proud owner of the very handsome WRX Subaru who favored us with pictures, did not mention if he had to periodically
re-fill the water tank for the turbo charger. If that was not required then regardless what the dash mounted push-button says, there was NO water
injected into the airflow of his car.
Water injection has been around since Mr Otto invented the 4 cycle engine but it has never lived up to the claims made for it by its proponents.
“Keep it simple, stupid” is one rule in mechanics that is hard to beat.
Note 1. Some cars operate on very high pressure water cooling system. Many will use an electric fan to cool the radiator after engine shutdown. This
is meant to avoid the sudden release of superheated steam from the cooling system.