Several Mods + VGs = 9.66mpg Increase - Fuelly Forums

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Old 11-17-2007, 12:10 PM   #1
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Several Mods + VGs = 9.66mpg Increase

Best previous mpgs was 42.1. Today reached 52.19.

Mods were: grill block, delete muffler, tidy up the splash guards under nose, replace fuel filter, and add vortex generators.

The grill block completely covered the bottom lip all the way across flush. The top opening was slightly recessed, with a 6" opening behind the license plate for air to get to the radiator.

The muffler was hanging down into the slipstream. Ten seconds with the sawsall wrench fixed that. I cut off the available piping and routed the exhaust out the back right side. It sounds like a f*rt can, but without the cost.

The splash guards were hanging down into the wind. Fifteen minutes in the spare fastener bins and a socket set has them back up where they're supposed to be.

I doubt if the new fuel filter added anything, but it was one of the things I did that may/may not have changed things.

I made the vortex generators last night out of 3/4" angle aluminum. Delta wing shaped. 19mm by 39mm. Painted to match. I figure they were good for about .2mpg to .6 of the 9.66 increase.

First trip this a.m. No wind. 38*. Skys clear. Traffic not an issue. 60 to 65 mph.
100.076 miles. 1.94gal. 51.58mpg.

Trip two at late morning. Added vortex generators. No wind. 55*. Skys clear. Traffic not an issue. 60 to 65 mph.
104.9 miles. 2.01 gallons. 52.1902mpg. .61mpg increase.

Driver/vehicle/gaspump combo fairly consistant. Prior repeated trip of 165/166.7 miles on two consecutive days was different by .43mpg even though the pump shut off at the exact same 3.86 gallons.

Comments: The VGs were easy to make. Used tin snips & double sided tape. Placed 5 on each side of middle, 3" forward of the hatch opening, 15-ish degrees to normal flow. I can only justify .2mpg increase, but could be more. Not worth buying but look cool.

Big increase for grill block and muffler delete. Thoroughly tickled. The muffler was acting like an anchor the way it was hanging down. I had a good long look at the belly of the CRX and it's pretty darn flat already. The only other thing I could do would be to add a shield at the very back between the bumper and the suspension mounts.

Happy at the returns a few simple mods made.
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Old 11-17-2007, 12:19 PM   #2
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I wouldn't trust such small fillups.

Pictures of the VGs?
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Old 11-17-2007, 12:28 PM   #3
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Quote:
Originally Posted by SVOboy View Post
I wouldn't trust such small fillups.

Pictures of the VGs?
Yup! Your results will have more statistical significance once you have a better data spread. Watch for a trend over several tanks (3 or more), that'll be more accurate as to the benefit gained.
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Old 11-17-2007, 02:45 PM   #4
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I concur with further extrapolation. Still, it's hard to not be intrigued by that much difference. Even if it's 90% accurate, that's a bundle of betterment.

VG pics soon. But, they pretty much look like all the rest...

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Old 11-17-2007, 03:52 PM   #5
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With out FE instrumentation it really hard to tell what's going on. You would be surprised how just having to stop at a light you usually make will effect the FE for the trip. My grill block netting about 3% increase ( I think Metro had about the same) in FE and there is really no data for the VG's but maybe around 1% or so. Everything that improves the FE is good. Just keep plugging along and working on driver techniques and you'll be there in no time.

Love the paint job. What's that on the back of the hatchback? It looks very un aero.
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Old 11-17-2007, 05:10 PM   #6
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Quote:
Originally Posted by Mr Incredible View Post

But, they pretty much look like all the rest...


A piece of taught string is a VG too Sticking your hand out into free stream flow can be considered a vortex generator (just trying to point out that a commercial product version of something doesn't define the concept ).

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In any case... Get multiple full tank fill ups, use the same fuel pump and do your best to drive consistently
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Old 11-17-2007, 06:25 PM   #7
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I've attached installed and in-progress photos. I don't think the VGs really did much, but they were dead easy to make. I think maybe the rear angle might be too steep, but it's pretty close.

Zpiloto, I know it's only 100 miles each trip and there's no instrumentation, but it was repeatable and consistant with prior efforts. I was probably as surprised as anybody that those few things gave me a 9mpg increase. I've been checking mpgs for some time, and this is in my acceptable figures range. I'm not selling anything nor applying for a grant, so it's good enough for me. I'll certainly come back if I find faults somewhere.

What's responsible for how much is hard to say, but the VGs didn't make enough difference to thrill me. But, since they only cost about three-fiddy, I don't mind.

I'm still agog that my humble vehicle would be in the 50mpg range. For me it's unbelieveable. Looking forward to my 10mpg truck for the winter really was depressing.

That very un-aerodynamic thing on the back is the wiper arm. The squirter doesn't work so I never use it unless by mistake. Winter's coming so I'll be using it for frost & snow and I'll leave it for now. I've never had one and I'd kinda like to play with it for a while.
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Old 11-17-2007, 07:10 PM   #8
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I was wondering about the weird reflection and then I remembered the woodland paint scheme



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Old 11-19-2007, 06:58 AM   #9
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Quote:
Originally Posted by Mr Incredible View Post
Comments: The VGs were easy to make. Used tin snips & double sided tape. Placed 5 on each side of middle, 3" forward of the hatch opening, 15-ish degrees to normal flow. I can only justify .2mpg increase, but could be more. Not worth buying but look cool.
Did you use oil drops or anything to test for actual air flow direction? You might be surprised by how it actually flows.

http://www.gassavers.org/showthread.php?t=1482
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Old 11-19-2007, 07:56 AM   #10
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Good results, but I agree you should do longer fill-ups. I generally try to almost run the car to empty to get the most accurate MPG results.
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