Finally some useful thermocouple (cooling) data?

[Daves]

The other day when we tuned our F4i engine on a Dynojet dynamometer, we placed a J-type thermocouple in the radiator inlet, a J-type in the radiator outlet, and a J-type in the ambient atmosphere. For coolant we used 3/4 gallon of distilled water with 2 capfuls of Royal Purple stuff. We had trouble getting the engine above 180?F (the temp at which our thermostat opens), but after revving it to around 13,000 rpm, we saw a peak radiator inlet temp of 194?F. Ambient temperature was about 90?F. Our results showed an average temperature differential of 9.6?F through the radiator. The differential values varied from 5?F to 15?. Is it a correct assumption that the higher inlet temp values would provide a higher temperature differential through the radiator, hence the higher 15? values?

Also, can anyone confirm temp. differential values of around 10?F with similar conditions? I can show a graph if you like.

[raska]

Your lucky the engine likes to stay so cool. We see at least 10F between the radiator outlet and the center of the head. Unfortunatly we have no data of the total temperature drop across the radiator for you. What type of composition is that Royal Purple stuff? ie. is it legal?

[Daves]

I am not sure what is in the Royal Purple additive, but at competition we will be using Water Wetter, which the FSAE Rules Committee deems is permissible as a rust inhibitor.

[Rob Davies]

Does those kind of coolant additives (water wetter etc...) improve performance over distilled water with a touch of corrosion inhibitor?

Ive heard differing views on the subject although there is no doubt that they reduce corrosion.

Thanks, Rob

[jonno]

yeah, a higher inlet temp will give higher temp drop across the core because of the higher temperature difference (delta T) to atmosphere. Presumably royal purple (???) and water wetter increase the specific heat capacity so the delta T of the coolant is less, therefore in the hotter engine it remains relatively cooler pulling more heat from the engine, and in the heat exchanger the coolant won't cool as fast keeping the delta T to atmosphere higher therefore rejecting more heat???