Nissan Maxima Aerodynamic Modifications

Maxima Aerodynamics Modifications

This page chronicles the Aero modifications made to Warren's 1998 Nissan Maxima SE.

July 2008
I blocked the upper and middle grill with 1/4" foam covered in black duct tape. It is not very noticeable visibly, and even in the hottest temperatures (100 degrees plus), the car water temperature is not adversely effected. Duct tape becomes wrinkled quickly.

At the time I did not have any way to measure the mileage other than per tank. Depending on conditions, the highway mileage was between 27 and 32 MPG.

July 2009
I finally obtained a Scangauge, so now I can more accurately measure the effects of the changes I make. Also with the Scangauge I found that the car shuts off the fuel injectors when coasting (automatic transmission), but if you put the car in neutral and coast the injectors have run to keep the engine turning. This means it's more economical to leave the car in gear when coasting. Go figure...

I'll start with the blocked grill as the starting point. This gives 29 MPG at 65 MPH on flat road and no wind. I will remove the mudflaps and rear spoiler to see if that has an effect. I have 2 sheets of 4mm Coroplast corrugated plastic which I will use next to fair the underside of the car.

Vehicle	Speed	Modification	MPG	Change	Temperature
1998 Nissan Maxima	65 MPH	Partially blocked grill	29.0	-	80 degrees F
1998 Nissan Maxima	65 MPH	Fully blocked grill, remove mudflaps, 4ft square of belly pan.	31.0	+2MPG	55 degrees F
1998 Nissan Maxima	65 MPH	Remove rear spoiler
1998 Nissan Maxima	65 MPH	Full belly pan

November 2009
Got some aero mods done over the past several months.

The front air ducts are now blocked.
Moved the front license plate to under the bumper (in front of the big lower duct).
Removed the front mud flaps.
Added a 4 ft square of Coroplast under the rear of the car. It's a start!

Driving around in-town doesn't give a great idea of any mileage changes made by these mods, so I was looking forward to driving home for the Thanksgiving holiday. On the way to my Mom's house it was rainy with temps in the low 40s. I ended up with 28.3 MPG for the trip down, and was disappointed, but temperature effects mileage so I did not give up hope. The way home was sunny and about 55 degrees, and I mad it home with 31 MPG. That's 2 MPG better than I have seen before on this trip so I am on the right track.

With all the vents blocked (except the small strip in the leading edge of the bumper), the engine temps remain normal. The under-hood temp sensed by the Scanguage (intake air temp) does go over 100 degrees after driving for a while in stop and go traffic, and because of this I need to add an LED to my dash to show me when the electric fans are running, Also I will probably need to either add variable vents or remove the big lower grill block during the summer.