Vibe mods: One man's quest to better 40mpg.

[Tango Charlie]

Thanks, guys. I'm gonna cut bigger holes in the lower grille block and reinstall it during my lunch hour and see what it does on the way home tonight.

It's amazing what you can learn with a little feedback. On my little excursion out of town last weekend, I couldn't figure out at first why my new little fan indicator LED was staying on. Then I realized that I had defrost selected.
Defrost=AC=fan running constantly. I knew that, just needed the little red LED for the dope-slap upside the head.

[Tango Charlie]

I elongated the holes in the lower grille block so they're both about eight inch long ovals. It was around 70F ambient on the way home last night, and the fan didn't kick on at all. Then, this morning with the ambient around 62F, coolant temps reached 196F, well below the fan activating temp of 204F. I'll keep monitoring it as the weather gets warmer. I might have to enlarge the holes just a tad more, but we'll see.

I'm wondering if version 3 of my lower grille block should have longer (horizontally) and more narrow (vertically) "slots", instead of oval holes.

[Istas]

I still think that from a fluid resistance viewpoint, a single opening as close to a circle as possible would provide the least resistance to flow. Since this is the front of a car, though, you also want to aim for the area of highest pressure on the front of your vehicle, which might be a bit difficult to assume on that Vibe.

It might be where you have them now, because the front's slanted back a bit. It might be further up, closer to the center of the main blunt front of the car. It might even be over on the sides, next to that part of the bumper jutting out, where the air might be being squeezed against that outcropping. You might be able to do some testing of that using a pressure gauge, a looong thin length of plastic tube, some tape, and a shot of tuft-testing of the area (from the article I read, I believe it was from autospeed.com somewhere though I don't have the link on me... anyway, the opening at the end of the plastic tube should be perpendicular to flow I think it said?) Even tuft testing would give you a decent idea of where the highest pressure area is (though use short strings, and lots of them, for high resolution).

I think you're going in the right direction with horizontally-enlongated openings, at any rate.

[Istas]

Your rims definitely look like they could use a pizza-pan treatment of some sort, especially in the front. And is there any way you can completely remove the roof rack, not just the cross bars?

[beatr911]

You have the holes in the highest pressure area already, well smack in the middle is the highest actually. By looking at those computer model pictures that show air pressure on the front of vehicles you've got the location about right. Check for leakage so that all the air that passes through the hole actually goes through the radiator.

Ajohnmeyer if he is still around, had a cable acuated swinging door where he could adjust the airflow while driving. Cool weather and high speed close it down, warmer weather open 'er up. He was cutting it pretty fine and went to the dark side with an alternator-less system as well as a host of many other more budget friendly mods. Hope all is well with him.

Coroplast under trays next? BTW coroplast can be ordered in black. When the paint begins to chip off you may consider this as a more permanent solution. I am.

[Tango Charlie]

Originally Posted by Istas

I still think that from a fluid resistance viewpoint, a single opening as close to a circle as possible would provide the least resistance to flow...

I agree, Istas, as I've always admired LoPresti's aircraft cowlings with the distinctive round inlets. They're much more efficient than the OEM cowling designs. However, I'm not sure if a flat sheet of coroplast with a round hole cut in it really emulates a LoPresti cowl inlet.

Originally Posted by Istas

Your rims definitely look like they could use a pizza-pan treatment of some sort, especially in the front. And is there any way you can completely remove the roof rack, not just the cross bars?

I haven't applied my brainpower to discs yet. Have patience...

Removing the roof rack on a Vibe is problematic, in that it is integrated into the roof to the point that when removed, it leaves a gaping hole on either side of the rear lift gate. Not an impossible obstacle, it'll just take some concentrated effort to 'git er done'. I'm thinking some hardwood rails carved down into a low profile and screwed down in place of the current rails. Then sealed with some polyurethane and buffed to a high shine so it looks like an America's Cup racer. But that's for another summer...

[Tango Charlie]

Originally Posted by beatr911

...Check for leakage so that all the air that passes through the hole actually goes through the radiator...

Coroplast under trays next? BTW coroplast can be ordered in black. When the paint begins to chip off you may consider this as a more permanent solution. I am.

I have installed some coroplast 'boxing' around the radiator, but I do need to go back and basjoos the heck out of it.

Yup, undertray is the next big mod. I've heard that the black coroplast is 'softer' than the other colors, so I'll stick with white. Can't see it under the car, anyway. For the smaller stuff, I'm using from my Rensburger stash. Haven't even made a dent in it yet. If anyone is traveling through northern Indiana and needs a couple pieces, let me know.

[Istas]

Use sheet metal! Uuuuusssseee sheeeeeeeet meeeeeetallllllll....

*maniacal laughter*

[Daox]

Originally Posted by Tango Charlie

Yup, undertray is the next big mod. I've heard that the black coroplast is 'softer' than the other colors, so I'll stick with white.

I have white and black and there really doesn't seem to be any difference.

[Tango Charlie]

Good to know, Daox. Thanks.

Istas, I didn't understand where you were coming from until I saw your thread! Ha ha! Nice work on that, by the way.

Well, I've removed the lower grille block. On a warm day with the AC used sparingly, the coolant hovers around 187F. Any kind of additional blockage puts the coolant temp higher than what I'm comfortable with (~190F).

With my latest fuel log entry, I'm at 40.35mpg on my 90 day average! Yay! I've reached my first goal by successfully bettering 40mpg. Thank you, thank you very much. Couldn't have done it without this forum.

So what's next? Well, I would really like to cruise at 60mph with a 30% load indicated on the Scangauge. That would net me around 46-50 mpg (instantaneous), I believe. I'm going to try and get there primarily with aero mods. Belly panel, fog lamps, roof rack, and side mirrors will all receive attention. Discs, skirts, and kammback will be considered.
Stay tuned. It should be fun.