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Old 06-29-2020, 10:45 AM   #10 (permalink)
Join Date: Mar 2020
Location: Quebec Qc Canada
Posts: 52

AcuraMatata - '99 Acura EL Base
90 day: 42.17 mpg (US)

Le Vehicle - '12 Dodge Gran Caravan SE
90 day: 22.35 mpg (US)
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Front upper invisible grille block

This is my second attempt at an upper grille block as I am working under aesthetical constraint from my 42 years partner: "the car has to look good or you can't do it or you will have to remove the ugly modification".

The bottom spoiler is tolerated on promise that I will remove the fabric tape and finish it shiny when the body filler goes on special.

So, instead of my first work at an external grille block that hid the grille and the Acura crest (picture), I went around and blocked the grille from behind with black choroplast held by some "big monkey" fabric tape (picture).

I suppose the aerodynamics effect of having the grille blocked from the back rather than the front is not that much. I suppose a boundary layer builds up at the surface of the grille features and serves the same purpose as attaching some solid material in front of the grille to block it. So air flows up the grille area "sliding" on the boundary layer.

A mask on the top wide slot under the upper grille where the licence plate should sit adds to the air blockage. Invisible to the left of this blocage is the air intake mouth that collects air for the engine (more on that later).

These grille blockages give pretty much the same results for the engine coolant temperature as the previous in front of the grille blockages. The previous and actual grille blocks cover the same areas. So the coolant temperature on highway gets from 82 to 95 Celsius when outside temperature ranges from 16 to 36 Celsius (180 to 203 F when outside temp from 60 to 97 F). The cooling fan kicks in at 97 Celsius (208 F). Going up a hill or with an heavy load at speeds under 70 km/h makes the coolant temperature go up to turn the fan on. Generally on highway the coolant temperature is maintained between 90 and 95 Celsius (194 to 203 F) which I read somewhere is the ideal temperature window for complete combustion.

As the belly pan works with the grille block to maintain a certain temperature in the engine compartment, the front of belly pan stops about the oil pan and in front of the wheels shafts and direction links. Before the second part of the belly pan, a belly wide opening is left for the air warmed in the engine compartment to exit under the car as it was initially engineered. The outsides of the middle pans are attached up to OEM side skirts with self taping screws and the front and inner sides are attached with zipties wherever there is a solid attachment point allowing.

Coolant temperature data is read from the car computer (ECU) through an OBD2 Bluetooth adapter and the data is logged on an Android phone or tablet. Coolant grade is good for up to 115 Celsius (240 F) and engine oil is synthetic 0W20.

On the aerodynamics side, the grille block was not evaluated separately from the belly pan, the in front of the rear wheels deflectors and the 45 PSI inflated tires. The preliminary combined result of drag reduction for the all these mods is 32,6%. The 45 PSI inflated tires were later compared to the Honda recommended 32 PSI inflated tires to yield a 12% drag reduction with the latter.
Attached Thumbnails
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Last edited by ACEL; 06-29-2020 at 11:39 PM.. Reason: To complete
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