View Full Version : Water-cooled Intercooling.....

29th July 2000, 09:28

As some of you know, I have been looking to improve the intercooling on my 94 WRX Auto for a while and I am now experimenting with an air/water IC.

I have managed to source a RS Legacy (Liberty) heat exchanger and fit it to my car. As it is an early model WRX, it is a bolt-on replacement. This was sourced from a Subaru breaker in the UK for 60+VAT.

In addition, I have bought a Jabsco "Water Puppy" electric pump (I don't make the names up http://bbs.22b.com/ubb/wink.gif ) and Mocal 25-row oil cooler along with the hoses/fittings etc.

The current volume of water is not high (circa 4 litres) so I have ordered a water tank from Forge Motorsport (http://www.forgemotorsport.co.uk) to add a 5 litre aluminium reservoir.

With the present volume, the water holds the charge heat for much longer than the Original Equipment (OE) one but it takes more time for the intake air to increase over the original "slanted" air/air unit I had. This should be improved with the increased capacity of water in the tank. Heat buildup when stationary or at low speed also seems to be reduced significantly - even compared with the OE air/air unit with fans mounted on the underside drawing cool air in.

The pump was initially very noisy when bolted to the inner wing but some "Dynamat-type" stuff and rubber feet has reduced the sound level.

The pump is wired through a relay to run whenever the ignition is on. The Jabsco pump is very well-built (brass body - weighs 3Kg) and is rated for continous operation at 31.7 litres per minutes (over double the flow of the OE RS Legacy unit). It can also be rebuilt when required.

I've also got some Water Wetter ready to try to add to the coolant.

I want to reverse the bonnet scoop and was curious whether the OE one can be turned around or a new one needs to be sourced ?

I was also wondering if anyone else has converted their car in a similar way (or have an OE cooler in their Legacy, GT4 etc) and if they had any pointers to better efficiency?

Total cost (including the tank) will be circa 450.



PS. I also found a free article on Autospeed which may be of interest: The Complete Guide to Intercooling - Part 2 (http://www.autospeed.com/C_articles/A_0090/P_1/article.html)

[This message has been edited by GavinP (edited 29 July 2000).]

30th July 2000, 11:18

Interesting setup.

You are using the Oil cooler as the water/air cooler (radiator) for your system ?

If so, they arent really effecient enough.

Here we go again.... I had a charge cooler designed for my previous scoob.. was done by Pace.

They fitted a big radiator up front... a lot larger than a mocal oil cooler.

Another suggestion would be to fit a resistor and pressure switch to drop the load donw on the pump.

I have used "continous running" pumps before.. and these have a finite life shorter than stated. The trick to extending the life is to use the resistor and drop the load to them off boost... and on boost (pressure switch) bypass it.. and make the pump go full speed.

Where will you locate the tank ? One main problem is still heat soak. Try and mount the tank in the boot, inplace of the spare wheel. But chances are your pump wont be strong enough to cope. Or at least away from the engine. Inner wing ?


30th July 2000, 14:51

Thanks for the reply.

Yes, the Mocal cooler is acting as the "radiator" and a bigger one is planned or additional cooler(s) used in series.

Space is the problem as I have another Mocal cooler in the gap near the number plate for the auto trans fluid.

The pump currently lives on the other side of the inner wing (i.e. near the air intake resonator pipe) and the tank I was planning to fit in front of the air filter. Swapping them over may be a better bet http://bbs.22b.com/ubb/smile.gif

I was also thinking about heat soak for the water tank - and the heat generated from the pump (the casing gets very warm!).

The boot-mounted tank is a good idea although it would require a lot of work and another pump as you said.

I understand that you have a front-mounted IC from Moray's questions in the past http://bbs.22b.com/ubb/wink.gif - have you reversed the bonnet scoop or left it as is ?