Best MECHANICAL Mods
 

I am looking for the best MECHANICAL modifications to improve mileage. I have a 2008 HHR Chevy with the 2.2 engine. I bought it for better gas mileage and it fits my needs perfectly in most other areas to.
My question is: What can I do mechanically to improve the mileage? My thoughts are:
1. Slightly taller tires to lower RPM. Done
2. Lower car 2 inches all the way around. Done
3. Better Cold Air Intake. Done
4. Large exhaust and muffler to get rid of restrictive stock system. Soon.
5. Underdrive pulleys. Soon.
6. Front air Dam. Done.
7. Trifecta tune to correct fuel and timing curves. Soon.
http://i413.photobucket.com/albums/p...e/P9291296.jpg

I feel that by doing these things I should be able to get better mileage and performance. Sure the driver can make more of a difference but this thread is about mechanical improvements.

Any other ideas? Thanks in advance. Curly

You may find folks chiming in to say that opening up the exhaust may hurt your fuel efficiency. Search around for "back pressure" here to see the various theories.

The cold air intake may not help either, though it's debatable how much it will hurt, if at all.

Other than that, your list is decent.

Curly1 -

Welcome to EM! I am interested in your lowering + taller tires. My paranoia is that my "one size up from stock" tires would rub on the inside of my wheel well. When you got your HHR, did you have the impression that the wheel well had plenty of "room to lower", or ?!?!?!?!?

As already said, items 3 and 4 are debatable for FE. Another alternative to the Trifecta tune is a fuel controller. Here is one example (I am assuming this is compatible, you'd have to ask someone on an HHR forum) :

Apexi Digital Super AFC II - air/fuel controller - Apexi - $400
Here are their latest goodies :

A'PEXi U.S.A. - Products: Electronics

If I were "starting from scratch", this would be a serious option for me because I think it can also double as a ScanGauge.

CarloSW2

See here: 50+ Vehicle modifications for better fuel economy - EcoModder.com

They are all sorted into catagories and relative effectiveness.

Lowering
 

The car rides much better and handles better with the Goldline lowering springs. The stock HHR would get blown around badly in cross wind or at higher speeds (60 and up). Now it is much better.
I also went with taller tires at the same time and not sure how much it has helped. I was so amazed at how much better it rode that I put the stock wheels and tires back on to see if it handled and cornered better because of the lowering or the tires. I think most of the improvement in ride is due to lowering. The stock HHR sits up too high with too soft of springs so I do not know if you would get the same improvments from your vehicle.
The tires should have a 10% speedometer error but I have not been able to verify that with my GPS. Seems to be closer to 5%? and that does not make any sense. According to several tire web sites and it says a 10% error.
According to my DIC the mileage is about the same but if there is an actual 10% error then in reality I have a 10% improvement?
Bottom line is I like the lowering and tires but the improvements is hard to say exactly how much. Curly

Thanks
 

Thanks, I found that after I posted this. I will read it again and start making a list of things to try. Curly

Don't forget to inflate tires to max sidewall pressure!

I bet some rear wheel well covers would look good if you were to go that route. I saw a "base" HHR the other day. White in color and Panel Van in nature with the fact that there were only windows in the rear, doors and windshield of the vehicle. That one would've looked neat with wheel well covers in white!

Curly1 -

Thanks for the info. Some cars come with odometer error "built in", :o . That could be contributing to what you are seeing. If I had done things squeeky clean to begin with, I would have done a GPS check with my stock tires to have a baseline for my odometer. But, I wasn't as obsessed with MPG back then.

It's not a mechanical mod, but I agree with TomO regarding rear wheel/fender skirts. I know I have seen PT Cruisers with aftermarket fender skirts, so I would think the same would be available for the HHR.

CarloSW2

nice list and even nicer lip. It goes well with the drop.

Curly1:

Welcome to EM.

I'd recommend going back to the original diameter tires. That's one thing the factory generally gets right. Bigger diameter tires reduce MPG because oftheir higher rotational moment of inertia. Lots of pickup guys thouight bigger tires would help but once they correct their odometers, they find it got worse.

Smaller diameter wheels/tire aid the aerodynamics as well.

The tires have helped
 

The tires (or lowering?) have helped. I was looking back over my notes and testing and it defnatly has helped. For instance I have went from 29.4 MPG @ 70 to 32.25 @ 70 MPH and if you add in the 10% speedometer error then it is 35.47 MPG. Note my GPS is only showing about 5% error? and all the tire web sites says there is a 10% difference with those tires?
That is with the air conditioner on high (it is Texas!) and I try to do the same 150 mile test run and test mileage at several speeds both directions. I try as much as possible to eliminate me as a variable. I record weather, altitude, wind, put it on cruise at the testing speed then clear the DIC and make a 20 or 25 mile test run.
Went from 37 @ 60 to 38.4 MPG and if you add in 10% speedometer error it is 42.24. RPM has been lowered 100 to 250 RPM at highway speeds.
One of the reasons I tested at speeds up to 85 MPH is because I do not feel the lowering and front spoiler will make much difference at low speeds such as 40.
I have not done any real testing with the front spoiler yet and not sure if gains will even show but I do not think it will hurt anything.

I think aero dynamic mods will help more at higher speeds and horse power like underdrive pulleys and removing wieght will help more at the lower speeds. Actually I think (hope) the underdrive pulleys will help at all speeds.

Once I get the mechanical mods where I want them then I will try to learn more how to drive effeciently. I know speeds over 60 or 65 is not effecient but it was needed for my testing.

My goals may be a little different than many here. I want to get the best mileage possible with out giving up my creature comforts. It is often over
100* here and I am not going with out my air conditioner. I drive a car to get to where I need to be so I want to tune my car to get the most out of it at the speeds I drive 60-70.
I am trying to build a car that gets good mileage, looks good, comfortable and is fun to drive. So what I consider "good mileage" may not be very impressive to many of you. Curly

Latest results
 

The car is coming along nicely, mileage is getting better the car looks good in my opinion.
http://i413.photobucket.com/albums/p...e/PB291356.jpg

Soon I will do the Trifecta Tune and I think it will bring everything together for good performance and mileage.

Lately mileage has been down some I think due to Winter blend fuel and colder weather. My city mileage had been up to 26 and it is down around 21 now...... Should be (hopefully) a temporary thing.

I do not think the Apexi fuel controller works with the Chevrolet cars. That does appear to be an interesting addition though to fine tune the fuel ratio.

The Ecotoc only has the air conditioner and alternator running off of the crank so I do not think an underdrive pulley would help this car much if any.

Underdrive pulleys don't help much.. they're usually the first thing that ricers get for their cars thinking that they're going to get some magical horsepower increase from them, and they don't. To further aid the propaganda marketing that those companies use, the ricers don't SAY that they didn't get much or any gain.

On top of that, most times, the underdrive pulleys aren't tested for road use, will fail visual emissions checks (for some reason, or maybe not anymore) and aren't properly balanced, meaning they'll chew up your motor and spit it out, for a potential 1% increase in engine efficiency.

It's really not worth it. Spend the $100 on something that will actually get you somewhere.

I do believe the Apex'i SAFC is universal. The VAFC is not. It's designed to control fuel/ignition curves for Honda cars when in Vtec, also a worthless "tuning tool".

The SAFC can also be used as a ScanGauge, of sorts. Given that you're running OBD-2, you're more likely to be happy with a piggy-back system instead of standalone tuning. The problem with standalone ECU tuning is that it kills the "learn" curve of the ECU. The ECU can no longer be used in "learn" mode, as it will rewrite the tune based on core parameters, and revert to OEM specs over time. Also, if you disconnect the battery, or it goes dead, your tune is gone, b/c the ECU will lose it's "learned" information and revert back to core values.

I'm not sure about emissions laws in TX, but I know that if you're going to run a CAI, you should get a reputable one. They don't all do the same thing, regardless of what anyone tells you. A dyno sheet with a standard short ram intake and a full CAI shows the same HP increase across the board, except the CAI shows a spike at a given RPM range. That RPM range can be tuned by the manufacturer to give a spike at lower or higher RPMs.

AEM makes one of the best intakes there is, IMO (and in the opinion of several thousand street tuners, apparently). If you don't want to pay for an AEM intake, ICEMAN is the next in the line. They use a light, thermo-plastic resin that actually insulates the intake from engine bay heat soak.

K&N and other oil-soaked filters have been known to cause damage to your sensors, so probably best to stay away from them. It's already been discussed 1000's of times here and elsewhere that your air filter isn't a problem anyway, under normal driving situations.

Basically, you'll want to do anything you can to make more power with the fuel you're already using, if you're looking for more power and better mileage.

CFG83 - 215/55R16's on 16x7 wheels will fit under your car, even lowered slightly.

Mechanical is a taller top gear. Also a hotter thermostat. Some cars have 170 degree thermostat. Some engines like to run a little hotter and produce better numbers. As far as the Intake the stock one will be better for fuel economy. Reading from your posts you're more inclined towards performance than fuel economy so you might not get rid of that intake. My stock intake setup gave me 38-39mpg on the freeway. When I put an Injen intake my freeway number went down to 31mpg. So it might be hurting you more than you think.

What else...the apexi safc/vafc requires some dyno time and might not get you the results you want. I would advice getting a scanguage 2. You'll raise a couple mpg from that alone. I have been told people that have standalone ecu's only raise their mpg by 3. Might as well get yourself a scangauge 2 and put out the same if not better numbers and it's plug and play.

It seems like the rear wing would be hindering the airflow at the rear, since it appears to be slightly above the roofline. If you can cleanly take it off, it might be something to try.

Particularly for the winter, get rid of the CAI! You might even look into a WAI, taking warm air from somewhere hot in the engine bay like around the exhaust manifold. Less power, true, but you'll be reducing the pumping losses resulting from pulling air past a nearly-closed throttle plate at cruise.

Pump those tires up to the max number found on the sidewall. Lower rolling resistance is good!

Try ditching the wing. There's a good chance that will help.

Consider a belly pan.

Consider wheel skirts.

Consider a grille block, particularly with the cold winter weather. (OK, let me put that "cold" in quotation marks, as you folks in TX don't get much colder than we do in CA... ;) )

Do get a ScanGauge. That can let you make small changes to your driving which can improve your fuel conomy more than any mechanical mod you can hope to make.

-soD

As your vehicle has relatively tight wheel wells, flat wheel covers (Mooneyes) may be as effective as skirts and easier to live with.

I think I too suggested this in your other thread. ( was that you ? )
I can understand not wanting to mess up the looks of your vehicle.

If you put on some plain wheels with moon wheels and then stored the 'nice' ones in the garage, it would only take you 15 minutes or so to put the 'nice ' ones back on.

Here is what your HHR would look like with moon wheels : http://www.urbanracer.com/gallery/ar..._chevy/hhr.jpg

Try some side skirts to match your front air dam. Won't mess with the looks at all...might match well.

On taller tires if you go skinnier while going slightly taller you are usually better off. Go too tall and you definitely lose. You basically do not want to increase the weight of the tire at all or the width (or the rolling resistance).

Don't inflate to max sidewall pressure like someone said. That will reduce the life of the tires by causing uneven wear.

Can you latch onto the final drive gears from a Cobalt XFE?

Bud that is an unsubstanciated claim (Untrue) that has been disproved a dozen times in a dozen different threads on this site, so lets not rehash it on this one ...

I have never yet seen a tire that wore out in the middle before the edges. And I run mine 5 psi above the sidewall rating.

I have. Some do and some don't I guess.

I've seen both. Light truck tires w/ greater load capacity seem to be more likely to wear unevenly if over-inflated, while passenger car tires w/ lower load capacities seem to be more forgiving IME.