water to air intercoolers

I would definately agree..

Where does the water suply come from and how do you cool it????

PeterD

AGAINST -

Complexity & Cost. You need a second radiator, water pump & preferably some form of pump speed control, 2 speeds will do the trick. They are much harder to size, this is why we have pumped hundreds of hours into data logging & creating a sizing spreadsheet programme. Under the same circumstances, drive in/out will be approx. 20 to 60% dearer.

It also became apparent after a couple of years testing that I had to down grade my initial cooling estimates of air/water intercooling, which is a disappointment, but necessary. I thought that I could design a system that at speed, would cool the charge air within 4ºc of a front mount - both systems being equally engineered. It appears 8 to 12 ºc is a real world figure. Please put this into perspective. A 'front mount' car - Skyline GTR, 180 - 200 Sx, Supra etc. will give results on a 25ºc day of 31 - 36ºc into the plennum. An air/water setup will give 42 - 48ºc under the same circumstances, but a 'non front mount' car - Skyline GTS-t, VL Commodore, Subaru - any car that doesn't have a front facing throttle body towards the radiator support - will give similar temps. due to heat soak in the long return pipe from under bonnet heat - approx 70 + ºc, even though the charge air in both air/air setups, exits the 'cooler at 31 - 36ºc.

FOR --

Now, the above paragraph is the only time a front mount will out perform an air/water if both are set up properly - at speed . Stop/start, drag racing, towing, 4 x 4 offroad etc. all gain from air/water. The charge air temps. into the engine are also much more stable with logging showing a spread of 35 to 40ºc around town & 35 to 50ºc laden in soft sand, 2nd gear low range, whereas, front mounts have logged 30 to 65ºc around town & 30 to 95ºc in sand. This is with turbo outlet temps of 140ºc as for a top mount, 38ºc c to 116ºc have been recorded ! When you have your foot right into it at slower speeds is when detonation is most likely to happen, air/air intercooling is performing at it's worst efficiency. A very big fan under a top mount will make a fair difference & to a lesser extent, behind a front mount, but none can get near the fact that water 'holds' heat 37 times better than air & a thin radiator at the front of a vehicle cools better than a thick intercooler (air flow), & also has much less effect on the volume of air flow too the engine radiator - very important with some vehicles - eg. 70 series Landcruisers. Take a Toyota MR2 & they have no opposition really. Also, this small heat spread allows safer 'set it on kill' tuneups, if that's your need. It also in a small way, helps engine component longetivity with head gasket, top piston rings & valve seats benefiting most.

Another big plus is is with the length of the inlet track. Some cars have a bunch of pipes to get from the turbo to the front & then back to the throttle body - Subaru WRX springs to mind. It's not so much turbo lag as, filling the volume lag. Sometimes big holes have to be cut in the inner panels for these pipes, so when you go to sell the car, you have to leave the intercooler on as the holes give it away. Two 25mm hoses can be routed to the front so when they are removed, no evidence exits of a performance enhancement being fitted - higher trade in ?, & your air/water setup could be sold for maybe a 50 % return.

Add an engineered ( or even a simple ice bucket) ice water chiller & the results of air/water intercooling over air/air are undeniable. 1 to 1.25 % power increase for every 10 deg. Farenheight decrease, is the possible horsepower gains - note the imperial measurements. If you have an all out engine combination, this can give you the winning edge - safely ! If you are making 600 hp with 150 deg f charge air temps & an air/water setup reduces this to 70 deg. f. - then a power gain of 60 hp is possible. I buy most the turbo magazines from around the world every month & have done for 6 years. Over the past 2 years I notice that 85% of featured new drag cars are fitted with air/water intercooling now. It is the only legal way of getting the charge air temperature down near or below ambient air temperature, running petrol. Methanol as a fuel can get reasonably close, & as an injected additive does a good job, but watch the corrosion. Water sprays can be banned at Dragstrips & some Dyno competitions, although fine for the street.

Sorry I was thinking of ON HWY Running as opposed to Low range 4WD work with my comment.