96 Geo Tracker Upper Grill Block

[alohaspirit]

I get 23-24 mpg driving the way I do.
(decent mileage for a 4 door auto)
I live on a two mile hill so driving anywhere means driving that hill
Each and every week for a year Id say,
I gas up on the same day at the same place at roughly the same time.


I decided to make an upper grill block using rigid cardboard spraypainted with leftover car paint. Then I used electrical tape to attach to the car. I chose to go OVER the grill instead of behind it in an effort to maximize air flow. I left the bottom grill uncovered.


After 7 days, my results were relatively inconclusive. The aerodynamics didnt make driving any smoother. Mileage was clocked at an unimpressive 22.8mpg. And to make matters worse, it felt like it was running hotter and the shift points changed to a higher rpm. (albeit slightly in both cases, which probably attributed to the mpg) The grill block stayed on well enough. The spray paint made it water proof enough for 2 days of rain. If it wasnt for the rain I would think it would last a few months as is.


I wish I had a scanguage to fully check mpg and temp changes but perhaps later I will get one. For now, the grill block is off and things have returned to normal.


Input?

[jimepting]

Problem is, even with a ScanGauge it is pretty tough to accurately measure the effects of small changes in aerodynamics. It is hopeless when you are only testing tank to tank improvements. The grill block will help a bit, perhaps .4-.8 MPG, but that increase is almost within the noise of even the most carefully conducted ScanGauge testing. I did some testing on fender skirts on my Echo and was able, after several testing false starts, to determine that the improvement was .6-.8 MPG. Pretty small, but when one adds several improvements like grill blocks, fender skirts, smooth hub caps, underbelly, mirror removals, antenna removals, windshield wiper removals, etc. the total effects begin to add up. Most folks think that grill blocks are most effective at lowering warmup times, though there is a small aero improvement if well designed.

[alohaspirit]

That is perfectly understandable.

I can also imagine that it would help more if I were
someplace colder instead of being in a warm climate.

[aerohead]

Aloha,GM/Suzuki did a pretty good job of minimizing grill area for the Tracker as it appears in standard form.To reduce it beyond that may require a completely air-tight duct between the grill and radiator so that stagnation pressure doesn't bleed off before the air can get to the radiator.If that passageway is open to the bottom right now,there may be no way to keep it cool.-------------------------------------------------------------- Also,constant steady highway driving is the only place the benefit of a grill-block is going to show up.And if it's raining enough the that the Tracker leaves "tracks" in the wet road,it's too wet for testing.---------------------------------------------------------- I'd make sure you have an air-tight duct before you constrict the passageway.

[alohaspirit]

good point aerohead


been another week
filled up same spot, same day, roughly the same time
got 23.6 mpg

o.O

[hummingbird]

Alohaspirit, given your climate, you should probably stick to coroplast for all your mods, to make your time investment worthwhile. I would hate it, if my day's toil is literally washed away in a strong downpour in the evening.

[alohaspirit]

i agree hummingbird

if i were making a permanent block i would have used coroplast

but since it was a test, i was able to make a cardboard block in 10 minutes


in Hawaii, I feel the temperature and the lack of true highway driving are good factors
its ok to block the grill when its 40F
but you might want to think about it when its 80F
plus almost 90% of my driving is within 10 miles

[hummingbird]

When you use EOC, I don't think grill block is an issue even at 80F. You are using the engine only at about .25 duty cycle. The thermal inertia of the engine block will be enough to guarantee temperatures don't overshoot. (half the justification for the grill block is lost though)

Your use is not on flat land, so maybe it differs slightly there (going uphill part).

BTW you are very close to my typical use - 3 miles per leg, ~ 10 miles /day, except weekends.