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The car is running a Garrett GTX3576R making 590hp on Church’s Dynapack dyno at 28psi of boost. E85 is the fuel burned, so that’s roughly 61lbs/min of airflow (give or take a few). Looking at the compressor map for a GTX3576 at 3.0 pressure ratio (28psi of boost plus an estimated 2psi of pressure drop through all the piping) and 61lbs/min, the compressor has an efficiency of 70%. So the calculated compressor outlet temperature of 516K (that’s degrees Kelvin, doing calculations in Kelvin is so much easier) is based on our measured compressor inlet temperature of 336K. The temperature we measured on the charge pipe was only 474K. Remember our measurement point was about two feet down the very hot aluminum charge pipe. So it appears a fair amount of heat escaped from the pipe. Remember, heat transfer is driven by temperature differential. The engine bay was about 180K, or 324F, cooler than the air in the charge pipe. Yup, a few hundred degrees of temperature differential will drive some heat transfer. Going back to the electrical circuit analogy, temperature differential is the voltage. Anyway, look back at the picture showing the charge pipe and notice the hydraulic line to the damper remote reservoir is wrapped in insulation as it’s touching the hot charge pipe. That’s what I call a good idea.
My old heat transfer prof was fond of saying, “at the end of the day”. So, at the end of the day, the number that really matters is the temperature of the air going into the engine relative to the ambient air temperature. On a turbocharged car, two major factors affecting engine air inlet temperature are turbo air inlet temperature and intercooler efficiency. Our simple little test with only four locations for temperature measurements has shown us there is some room for improvement. Keep an eye out as we’re going to tweak the setup a bit to improve performance.
