reno808

I have a question. My friend has a WRX STI and he put a Water sparyer for his intercooler he says it makes all the difference in the world. i dont beileve so. Does any one reallly know about sparying water into a stock intercooler and make a noticeable difference.
THANKS

911pcars

In the May '05 issue of Excellence, the "250 mph 911" article describes the engine having several cooling systems. The main cooling is from water-circulation for both the intercooler and engine. It also goes on to describe a separate water-sprayed front intercooler and intake manifold.

Many WRC cars use water spray systems for their intercoolers. In our tests, water spray reduces air temperature approximately 18-20ºF, no matter what the cooling application (intercooler, oil cooler, coolant radiator or brakes).

Sherwood

hatchy

I have a WRX STI too and the intercooler sprayer is a marketing thing. Doesn't work/make a difference.

Sameer

In my opinion, the water does help cool the air going into the intercooler. I'm sure the Prodrive gys put it there for a good cause. Also a turbocharged car would feel quicker in the night because the air is cooler or even when it rains, the car would feel quicker, reason being, cooler air going in.

hatchy

The Prodrive system is nothing like the ones that come in street cars; The street cars use what is basically a windshield sprayer pump, spraying the water at very low pressure--the water just rolls off the intercooler. For the system to work well, the water must be sprayed at high pressure with a very fine nozzle to atomize the water. My STI, with the stock intercooler and 91 octane fuel had a very bad habit of pinging at a certain RPM range (partly due to too much timing + too much heat in the intake air temp). After emptying nearly half the tank of water on it, it still pinged. At least for me, it didnt do any good.

JBH

The pinging is due to a lean condition. Cooling the air brings more oxgen to the engine so wouldn't that make it ping even worse?

911pcars

"The pinging is due to a lean condition. Cooling the air brings more oxgen to the engine so wouldn't that make it ping even worse?"

Pinging (detonation) is caused by uneven burning of the a/f mixture. The usual causes include:
- ignition timing too advanced
- too low fuel octane rating
- lugging the engine
- more basic would be too high compression ratio, poor combustion chamber design

A lean condition can lower the detonation threshold by increasing combustion chamber temperatures which in turn creates hot spots that tend to pre-ignite the mixture - sorta the same result via a slightly different means. Both detonation and pre-ignition create sudden and unusually high pressure spikes inside the chamber which can break and/or overheat engine parts and accelerate metal fatigue.

Lowering the air temperature (external cooling) doesn't change the oxygen content of the air. It promotes better heat transfer (heat goes from hot area to cooler area). Reducing the temperature of the incoming a/f mixture, however, increases the density of the air, so more air AND fuel can be packed into the chamber (increases volumetric efficiency). It also lowers the combustion temperature and reduces the tendency to detonate.

Turbochargers or superchargers normally increase the charge temperature as a byproduct of pressurizing (boosting) the mixture. That's why intercoolers are so important in removing heat from the intake charge and thus reducing the tendency to detonate.

Hope this helps,
Sherwood

Sameer

hatchy,

The Seine systems water spray is a high pressure and sprays in a mist form.

Product Description:
Seine System's MPC misting kit is a multi-purpose water mist delivery system for localized component cooling. The high pressure pump/pressure accumulator and non-clogging nozzle system produces 55 micron-size water droplets that quickly evaporate to absorb heat and lower air temperature 15-20ºF. Applications: Reduce underhood temperatures, increase efficiency of intercoolers, oil/coolant radiators, brakes, etc.; also create comfortable, environmental cooling for any mobile application with a 12-volt battery.

JBH

Bad me...I should have said, if the pinging is due to a lean condition, wouldn't cooling the charge air make it worse?

I suppose the answer is maybe because there are two conflicting effects to increased charge air cooling:
(-) increased air density increases the oxygen content of the air/fuel mixture thus making the mixture leaner
(+) the decreased charge temperature reduces the tendency for detonation.

Does #2 outweigh #1 or am I still confused about the role of the intercooler?

911pcars

"I suppose the answer is maybe because there are two conflicting effects to increased charge air cooling:
(-) increased air density increases the oxygen content of the air/fuel mixture thus making the mixture leaner
(+) the decreased charge temperature reduces the tendency for detonation.
"

Jeffrey,
I think you're correct in both statements, but not conflicting.

A change in air density changes the a/f mixture and you must compensate. This is most telling when driving at different altitudes. Assuming the a/f mixture is correct at sea level, increasing altitude will cause the mixture to go rich. Modern EFI systems can automatically compensate for changing air pressure/density.

Decreasing charge temperature does reduce tendency to knock (detonate). If you lower the temperature enough, one can, in a boosted engine for example, increase boost pressure for more power before the onset of detonation. Some do this by adding more fuel, some with water spray, some use a little of both.

If the fuel system does not automatically compensate from a factory-stock configuration, you must monitor and modify as tuners do with various a/f ratio, cylinder head and exhaust temp. meters.

Sherwood

Dark Lightning

Correct me if I'm wrong but most tracks frown on the use of external water sprayers, correct?

911pcars

"Correct me if I'm wrong but most tracks frown on the use of external water sprayers, correct?"

I can't speak for most tracks. That would be up to the race organization and class rules. Some rules allow water spray, some don't.

These cars can:
http://www.seinesystems.com/MPC-BrakeCool.htm
http://www.seinesystems.com/MPC-BrakeCool-Jag.htm

Sherwood

JadedSilver

Intercooler water spraying systems are real iffy in how/when they work. I've heard stories of how people say it's the best thing since slcied bread while others say it's not worth the time. Personally i think it really depends on the intercooler design, as most people who say it works tend to have aftermarket bar and plate intercoolers with better thermal transfer anyway. I have also heard of people substituting rubbing alcohol in place of the water, but i'd be wary of heat/sparks around that.

Now water/alky/meth injection systems are totally different and in my opinion are well worth the money spent........on high output/tuned motors. But again, another thing 99% of the daily drivers out there really won't need if properly tuned.

911pcars

The term "water spray" has different meanings and produces different results. Water droplet size and system pressure has everything to do with the ability to quickly vaporize the liquid so it can absorb heat. Folks have used windshield washer nozzles to purpose-built water misting nozzles at various levels of pressure. Performance varies depending on which end of the hardware spectrum from which you squirt.

Someone posted this comparison recently:

Latent heat of evaporation (CRC Handbook)
Alcohol, ethyl = 364 Btu/lb
Alcohol, methyl = 474 Btu/lb
Alcohol, propyl = 335 Btu/lb
Water = 970.3 Btu/lb

Sherwood

JadedSilver

Makes you wonder why all those "tuner" kids are using Co2/Nitrous oxide to spray on their intercoolers. I can hear them now.."But it's frozen, it's gotta work better than water." Aye aye aye. Effective?...maybe to a certain extent but not worth the hassle in the end.

I prefer just to build and tune a motor that works on it's own and doesn't rely on "bandaid" tricks to control an issue. Just one more thing to go wrong during a race and get you in a bind. Just my opinion on the subject. Still a good topic to discuss none the less.