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Old 01-11-2013, 09:09 PM   #22 (permalink)
Tesla
Master EcoModder
 
Join Date: Feb 2012
Location: Australia
Posts: 355

The Truck - '02 Nissan GU Patrol ST
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Still interested in this and others experiences, mine being a turbodiesel achieved benefits in power, throttle response & economy. My setup is basically a plenum created between the bullbar (push bar) and the engine bay, sealed all around so the only inlet is front and lower centre of bar and only outlets are radiator and engine intake. At cruise I get 20-25mm suction in the airbox which used to be between 60-80mm before the mod, it was worth about 1mpg in the economy stakes. Coasting in neutral, engine at idle at 100km there is about 10mm positive pressure in airbox, I'd like to get to 0 suction at cruise on the flat and maybe 30mm pressure when neutral coasting.
I am currently looking at shrouding rear of radiator to control airflow there, so only as much air as required for cooling goes through leaving a higher pressure in the plenum for the intake. The mock up shroud I have works well with angled top and sides directing air to the lower half of engine bay to exit underneath and to front wheel wells. This is where I plan to mount a thermo fan for those specially hot occassions stuck in traffic, I am currently running no fan and when temps get up like above 35C I get just a little nervous watching the coolant temp gauge, note that the factory gauge has never gone above half, usually sits about 1/3. It was better when I had the back of radiator fully open, even when stationary, natural thermals seemed to keep temps lower even when stationary, anyway I digress.
One of the things I noticed with the manometer (home made) when doing testing is there is about a 10mm drop in pressure at front of vehicle when travelling in a line of traffic, at a good safe distance not tailgaiting vs open road with no one ahead for at least 100m so this confirms the idea of better economy travelling in a line of traffic rather than being up front.
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