Oil Cooling - Air/oil Or Water/oil? Which Would You Use?

[Chris H 10]

I'm in the process of putting together an XU5 rally engine which should be putting out about 150bhp.

 

At the moment i have a std xu5 with no oil cooler but plan to fit one.

 

I have 3 options.

A -Fit a std OE type air/oil cooler, i have a brand new cooler (the one that bolts in the fan housing) and good 2nd hand pipework.

 

B - Fit an aftermarket air/oil cooler, i have a mocal sandwich plate but nothing else yet (but all bits easy enough to source)

 

C - Use a water/oil cooler as fitted to a 309 gti, i have a good modine cooler and top hose from my old 309 gti which i expect would fit ok in a 205.

 

What would you use and why?

 

[Tom Fenton 1,542]

In my experience even hard road use can see the oil temperature overwhelm the water/oil exchanger, so for competition use I would rule that out straight away.

Personally I would not want to risk a s/h standard oil/air cooler that could have debris in it on an expensive newly built rally engine.

So therefore I'd buy a good quality oil rad and new hoses to go with your sandwich plate.

[welshpug 1,661]

D-thermostatic air-oil cooler.

 

E-oil-water heat exchsnger plus air-oilcooler as per Citroën & Peugeot sport builds.

[Biggles 65]

I ran a Modine type oil/water cooler on my EW with somewhat more bhp than you're looking at (the one off a 406 Coupe I believe, the biggest Peugeot do) and oil temperature was never really the issue. I swapped to an oil/air type due to a water temperature issue. Sadly, as I changed the rad header tank at the same time, I don't know whether the water temp issue was due to insufficient water cooling capacity due to my small rad or what I thought might be an aeration issue caused by the old header tank.

If your water cooling system has sufficient capacity, then a big oil/water cooler should be fine. (As a rule of thumb, going oil/water adds 25% to the heat the water system needs to reject.)

[pug_ham 244 3 Cars]

What Tom said, I used to run an oe late spec oil/water exchanger on my occasional track day car & doing this cut my sessions shorter than it would've running with an air oil type.

 

I plan to fit an after market thermostat control air oil cooler when I eventually get the car rebuilt.

 

g

[Chris H 10]

I always thought the oil/water cooler on my 309 worked fine even with a 185bhp mi16 but maybe the 205 has a less efficient cooling system so probably the air/oil is the way to go if i can fit one in.

 

I was wondering whether the warming up of the oil with a water/oil cooler was much of an advantage to get everything up to temp better?

 

Is the std 205 gti oil cooler set up any good or marginal with any modifications?

[Biggles 65]

With the oil/water mine warmed up quite quickly, with oil/air it takes ages to get the oil to a sensible temp. The oil/water kept the oil at a much more even temp too. Is that a benefit on a competition car ? Hard to say as once you get it warm, it tends to stay warm, if you get my drift. I don't run an oil 'stat which probably increases warm-up time but again, on a competition car, once it's warm ...

[allanallen 528 2 Cars]

The standard air/oil cooler is pretty crap, marginally bringing temps down but nowhere near enough. My standard 8v ended up with a 16row air/oil cooler which worked very well. A combination of sump guard and short gearboxes can get engines very warm very quickly in my experience!

[ALEX 98 1 Cars]

It might be worth to note that I've had 2 brackets snap on me that supports the standard remote oil cooler from the gearbox (GTi with PAS).

So if your building a rally car this cast bracket might need updating