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Yesterday was a nice and cool day for assisting with testing a track car at Killarney Raceway in Cape Town.
This is an Audi R8 Replica. It is basically a Motorsport frame that the standard Audi R8 tub bolts to and all the standard lights and bodywork. This car has been in development for a while now. There were issues with the dry-sump system having pressure dropouts. After that was fixed and the car could be driven in anger the car had an overheating problem. The car has not been able to compete in races because of these issues.
On a previous test the car went out for one full-throttle lap and the coolant temp as at 125 Deg C. The cooling system pressure would spike to 2 bar pressure relieving the pressure at the reservoir cap. This was no good! After the Audi R8 came in from the one lap and we inspected the radiators they were cool. Although the system temp was at 125 Deg C. Something was off. The engine was running 2 Craig Daves EWP 150 liter per minute pumps in a push-pull setup. The radiators are sitting in the nose of the car. This makes the piping from and to the engine quite long.
What was the issue?
After inspection, we found that the two of the silicone bends in the cooling system was sucking flat. This indicated that there is a huge restriction over the radiators. That was really funny as the car was running the standard 3 radiator cluster plus an extra radiator in series to that. As you may note this temp issue has been around for a while. A second radiator to the standard cluster has been fitted with no luck of getting the temps down.
It was decided that all the silicone bends will be replaced with hard aluminum bends. The problem only occurs when the coolant gets to temp. This is where it started getting interesting. It was also decided that the radiators will be removed to be inspected. There should not be any issued with them as they were basically brand new. Guess what was found? The radiator was badly blocked up with some type of crystals. Most probably from that additive that get thrown in the tap water for cleaning the water.
How was the issue resolved?
There and then the complete radiator setup got thrown out. A single big radiator was fitted to the R8. This radiator had a core thickness of 70 millimeters. So this is one huge radiator, but still lighter than what was in the car. This radiator should, in theory, have a lot less restriction than a standard radiator. This is a good thing! The electric water pumps do not like restriction and the flow rates get reduced dramatically when restricted.
So yesterday the car went out for the test after all the mods were done to the cooling system. The car went out with anger and it stayed on power for most of the 2 laps it did. After the 2 laps, the car did a “cool down” lap to reduce heat soak and the car came into the pits. The coolant temp was stable at 80 Deg C and the coolant pressure was on 0.6 bar. By fixing the cooling the system pressure was also behaving itself.
This was a good day at the track and now the car is ready to compete in a race.
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