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Old 04-12-2011, 11:47 AM   #1 (permalink)
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Adela - '07 Chevrolet HHR 1LT
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HHR driver seeks to improve mileage

Hey everybody, I work at an engineering company in ann arbor and I want to stretch each $4 gallon of gas as far as it will take me because I'm also a poor student.

My problem is that I drive a 2007 Chevrolet HHR with every single aero-sucking option bolted on to it. It has the running boards, and the rear spoiler, and the roof rack with crossbars. Not a single other HHR I've seen in either Flint or A2 has all three. (or even roof rack and spoiler together!)

So lately I've been trying to adjust the nut behind the wheel, it's been going okay but you know you're starting from NOTHING if you consider 24mpg in mixed driving to be a good result.

In addition to further tweaking of the nut behind the wheel (perhaps some LARTing is in order as well) I'm going to hopefully get my hands on some scrap coroplast from campaign signs, for an upper grille block and rear wheel skirts. Maybe later I'll go into the crazy kammback and boattail things I've seen with aerocivic and MetroMPG. That's actually why I registered, I thought they were brilliant let crazy....

Let's see how this goes and If nothing else this will be a learning experience and so I don't drive so inefficiently.

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Old 04-12-2011, 01:05 PM   #2 (permalink)
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Welcome. Is it yours, or the company's? If it's yours, lose the roof rack for sure, the running boards if they're not a PITA, & the spoiler if you're good at body work.

Is it AT or MT? Equipped with the 2.2 or 2.4 L engine? In all cases, you're already beating the EPA combined fuel economy, but you can do significantly better. Keep your speeds down, and conserve momentum. Plan routes to avoid stops, drive 5-10 mph below freeway speed limits, and start coasting to lights and stop signs a couple of blocks in advance.
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Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
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49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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Old 04-12-2011, 01:48 PM   #3 (permalink)
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Adela - '07 Chevrolet HHR 1LT
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It's mine - if it were a company car I wouldn't mess with aero mods - , and I'm definitely going to frobnicate the crossbars tonight in the hope that I can figure out how to remove them. Losing the rails is definitely a body shop job though. I've got a split mind about losing the running boards - non-RB rocker panels aren't cheap and they're a PITA to install from posts on the HHR forums.
as far as the spoiler I'm going to talk to a body shop to see what they can do about it. It's bolted on so I'd need the holes filled. Even if I weren't going for efficiency I would still remove the thing, it's an ugly hoopthing that doesn't fit the lines of the car and it's cracked anyway from the weight of snow and ice this winter.

It is a slushbox 2.2 so I'm at a disadvantage there - the 2.4 actually gets better mileage because it's not straining like a cow in labour trying to move the car around. (yes, someone on the HHR forums compared the sound of the 2.2 under acceleration to a cow giving birth.)

Driving below speed limit on the expressway is not something that I have much experience doing... in fact when I don't look at my speedo I tend to plateau around 82-85 on an empty stretch of road. But at least I'm not my best friend that tends to hit the governor in her 2003 Cavalier.

ETA: just noticed you drive an xB. I was going to get a first gen xB but everything for sale around here when I got my car was manual transmission, and I'm not experienced enough to DD one.
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Old 04-12-2011, 04:25 PM   #4 (permalink)
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Moderate aero mods can help you tweak 5-10% FE improvement. Driver behavioral changes can make 30-40% improvement with an AT, 50-70% with a MT. So pick the low-hanging fruit first, by slowing down. You'll get low-mid 20 mpg at 80 mph, mid 20s mpg at 70 mph, mid 30s mpg at 60 mph, and high 30s mpg at 55 mph. If you have cruise control, set it to the PSL, stay in the right lane, and watch everyone get around you. Once you build up your confidence that, indeed, you won't die by driving the legal speed limit, drop to 5 or 10 mph below the PSL. The most dangerous place to be is in the high speed conga line of tailgaters going 75 mph with <1 second between cars.

Instead of keeping your foot on the gas until you're half a block from red lights and stop signs, start coasting to them (in neutral, when you're confident of your skills) 2-3 blocks ahead. Every time you slow to a stop from 35 mph, you're throwing away the same amount of energy they crash test cars with - in other words, you're throwing away enough energy to kill a person.
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Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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Old 04-12-2011, 07:10 PM   #5 (permalink)
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Adela - '07 Chevrolet HHR 1LT
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Today when driving home from work I reset my in dash MPG display and ended up at 29.7 when I pulled into my apartment parking space. I would have broken 30 but for the uphill driveway for my building.

-- coasting to lights (I can't time lights worth a crap, so I still did use my brakes a lot)
-- driving 62-65 on the expressway
-- shifted to neutral at red lights

And that's about all I did differently. Low hanging fruit indeed. Then again my commute is mainly eight miles down I-94 with only about five blocks of non-expressway driving.

I'll shoot for 30 average going to work and coming back, tomorrow.
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Old 04-12-2011, 11:16 PM   #6 (permalink)
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Alright! A >25% improvement just from adjusting the nut behind the wheel. Let us know how you do tomorrow. You've got a lot more low hanging fruit - 60 and 55 mph, turning the engine off at stoplights, etc. Get that 30 mpg barrier first .
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Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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Old 04-13-2011, 04:55 PM   #7 (permalink)
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Yeah, those aero-appendages are quite something else!

Kinda looks like a stinkbug on wheels....
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Old 04-13-2011, 07:15 PM   #8 (permalink)
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Adela - '07 Chevrolet HHR 1LT
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Quote:
Originally Posted by albyneau View Post
Yeah, those aero-appendages are quite something else!

Kinda looks like a stinkbug on wheels....
Hey now...

okay, I do actually agree with you somewhat.

btw, I got rid of the roof rack crossbars last night and made 29.9 going to work today. blasted red lights
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Old 04-13-2011, 07:52 PM   #9 (permalink)
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Adela - '07 Chevrolet HHR 1LT
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and...... 32.8mpg on the way home from work. I'm getting better at this whole driving efficiently thing.
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Old 04-13-2011, 08:35 PM   #10 (permalink)
Pishtaco
 
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32.8 mpg! That's awesome. Now if you could just find an alternate country road with a 45 mph speed limit and no stops .

Another low-hanging fruit is keeping your torque converter from slipping. When you're accelerating, try to keep your rpms around 2200. If the tach speed climbs to 2500 or 3000, you're throwing away fuel.

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Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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