Project: Geo Metro boat tail prototype - 15% MPG improvement @ 90 kph / 56 mph

[Sorrow Six Star]

that's awesome!

but not as awesome as the vortex gun...

just noticed the mini eclipse headlights nice touch!
^^ oops *tail lights

[Piwoslaw]

Nice job Majestic
Now, why does it remind me of Darth Vader?

[Rokeby]

It somewhat resembles an aardvark's head, without the ears, of course:



Aardvarks sometimes suffer from self image issues:

[thatguitarguy]

Originally Posted by Rokeby

In a smaller size, camouflaged as a tail pipe, it would be very useful to
express displeasure to tailgaters.

Smaller?!? I think it would make the perfect substructure for a boattail as it is!

[Cd]

Originally Posted by majestic

This is the best implementation of a boattail I have seen yet.

I would love to see you make a more permanent version, so I did a little photoshop, hope you don't mind!

YKYAEM when you have this as your desktop wallpapaer.

[MetroMPG]

majestic: thanks for that image. The eventual permanent/removable version won't look that nice!

---

Did some testing today. Several significant disclaimers follow...

The chart shows speed vs. MPG in bi-directional runs on the same stretch of road.

Green line was a "baseline" for the car (included partial grille block & rear skirts),

Yellow/orange after installing the transmission with the taller final drive,

Blue = boat tail



Disclaimers: Also, the fuel use offset I'm using on the ScanGauge now is higher than those 2 tests (I don't think I recorded it then, actually), so all else being equal, my displayed MPG is actually slightly less now than it would have been then.

• The 3 tests aren't strictly comparable for a bunch of reasons, not the least of which is weather conditions (temp) differing a lot

• Ethanol in fuel now (5 or 10%, I forget which), but not when the first 2 tests were run

• Cruise control was used for the previous testing, but I used my foot today. Even though I managed to keep the average speed dead on for 9/10 one-way runs (one run was off by 1 mph), the average doesn't tell the whole story - it's no where near as precise/consistent as cruise control.

• The car is older, different weight oil in the engine, tires are more worn, spark plugs are probably worn more, etc. etc.

So take this as an "actual mileage may vary" comparison. The relative comparisons are not really accurate. But there's no doubt the absolute figures are satisfying, and they should get even better when I stick the undertray back on.

I'm going to try to do the A-B-A one day this week - its results should be a bit more accurate for relative numbers.

[gone-ot]

...it's interesting (??) to note the little "bump" in milage at 70 km in both the original (green) and new trans (yellow/orange) data.

...intake or exhaust "tuning" coming into play maybe?

[MetroMPG]

Yes, it's weird. But since it's a single data point (average of 2 bi-dir runs) for each speed, I wouldn't read too much into any outliers.

[MetroMPG]

Originally Posted by Nerys

so your getting 70mpg highway? ?? how exactly are you doing that?

Driving relatively slowly & attentively in a car with lots of mods!

[gone-ot]

...I'm just saying that "coincidence" it's probably NOT, especially in light of being both averaged and repeated in different configurations.