Does anyone know the Drag Coeffecient of the HHR? Anything that can be done to help it?
I lowered my car (2") and put a front air dam (4") on it and I think it helped the drag coeffecient but do not know for sure.
There is 3 different HHR rear spoilers that I know of, the standard HHR arch type spoiler, the flat SS type and a generic SS looking one sold on EBay.
Does anyone know if there is a aerodynamic difference in them and if so what is better with spoiler or with out and if so which one?
Thanks, Curly

I come here in search of infintite wisdom. Come on somebody knows something about Aerodynamics?
I am modifying my HHR but I want to be careful not to do anything that will make it worse even if it is just a tiny bit.
I will add a spoiler if I know that it will not hurt it aerodynamically. Thanks, Curly

curley there is a thread somewere on this place about the different wind resiance ratings of a few vehicles and it included the HHR but for the life of me I cant find it

I did some searching and found a few things out. Note These came from several different sourses so may not be exact.
1. The HHR is .354
2. The PT Cruiser is .39
3. The Scion xB is .32

I would have thought the PT would be best as the rear slopes down more and is more pointed in the front. I would have thought the Scion xB is the worst........ By the way one of the compairson sites basically said the HHR was better in every way than the PT. Better performance, mileage and comfort.

Now I would like to know how much it helps the Drag Coeffiecient by lowering the car 2 inches and adding a front air dam.?

Thanks, Curly

I did some searching and found a few things out. Note These came from several different sourses so may not be exact.
1. The HHR is .354
2. The PT Cruiser is .39
3. The Scion xB is .32

I would have thought the PT would be best as the rear slopes down more and is more pointed in the front. I would have thought the Scion xB is the worst........ By the way one of the compairson sites basically said the HHR was better in every way than the PT. Better performance, mileage and comfort.

Now I would like to know how much it helps the Drag Coeffiecient by lowering the car 2 inches and adding a front air dam.?

Thanks, Curly

Contract with a wind tunnel facility, put your car in it and post the results! :roll:

Seriously, I admire your tenacity in getting better MPG with the HHR, but you honestly tend to get off on tangents, often inspired by the proliferation of false or misleading advertising out there.

Sorry for being so blunt, but things like intakes and exhaust... The stock intake and exhaust on the HHR is VERY efficient, with very little loss at full power demands, let alone the very low demands at normal cruising levels.

Your best bet in your quest would be to listen to proven science, not advertising hype or the myth and lore out here on the internet.

1. Make sure that your car is properly maintained... Oil changes, filters, etc.

2. Observe proper tire inflation pressures and possibly increase them by a few pounds.

3. Read about "hypermiling"... You don't have to necessarily be a complete "nut" in this regard, but there are some useful ideas, that if followed, will result in considerable mileage increases, especially in stop and go travel.

4. Consider a "good" tune for your car. By "good", I mean from somebody who really understands these cars and can create a tune that will result in better mileage. This can also result in better performance, too. Many think that tuning is an either/or proposition, but that is not true, since the engine is operating in different areas of the tuning tables under cruise and full demand conditions. If you talk to a tuner, just make sure that they have given attention to attaining MBT (Mean Best Torque) timing values under cruise conditions. Not many have, nor have spent the time and effort here, but this is definitely a big gain in MPG if done properly. For example, my 2.4 LE5 with a supercharger and (bad for mileage) 235/40-18 tires can do 37.5 MPG on long trips. It's faster, too!!

Curly......

Remember, the drag coefficient, while calculated the same way is designed and computed for different goals. For example, the 2008 Corvette Coupe has a coefficient of .28. The 2008 Z06 has a coefficient .34 (notice how very close this is to the HHR).

So, the point is.....what YOU may believe is justified, may actually reduce the desired effect. But as Joe suggested, what you do is only as good as a wind tunnel report.

Anyone know any thing about which spoiler is best or if it is better with out one?

What I am trying to do here is give my car the best aerodynamic advantadges possible with out going to ugly wheel well covers etc. Trying to get the best mileage possible from my car.

Bruce, none of the spoilers will make a difference aerodynamically, it's all in what looks best to you. At the speeds you travel, a rear spoiler won't have any positive effect (downforce) or negative (drag). Proper maintenance & driving habits as others have said will be your best bet.

I want to modify it and get it to perform the best it can and leave it. Then concentrate on my driving. I agree with much of what you are saying and disagree with some.
Aerodynamics. Sometimes what looks good really is not. That is why I asked the question. For instance the Z06 Corvette looks much more aerodynamic than the HHR. I would have never thought they were so close.

I really do not pay much attention to advertising I try to put what worked on my drag racing car into my HHR. That is help the aerodynamics, save weight, reduce parisitic drag of alternator, air conditioning compressor etc. On my race car I looked at everything and removed it, modified it, lowered it or relocated it.

On the intake and exhaust I believe that opening it up some and tuning for it will improve performance, sound and mileage. I might be wrong as I have been wrong before. I will keep all of the stock junk in case I am wrong.

I do not think any stock vehicle is perfect for all needs and can be modified to work better for your needs. Curly

Highway speeds vs dragway speeds have little in common.

"Highway speeds vs dragway speeds have little in common."
In fact they do have a lot in common. Better aerodynamics helps performance AND mileage. Lighter weight helps performance AND mileage. Getting the most performance out of every drop of fuel is just as important to any racer as it is to someone trying for the best mileage.
It takes horsepower to overcome wind drag and weight. Period, that is with a drag car or an economy car. It takes gas to make horsepower, if you can reduce wind drag and make it lighter then it does not take as much gas to do the same work. Then get the most out of each drop of gas.
It goes much deeper than that. Most of the safety features and engine designs and body designs have strong roots in racing. That allows them to make a small 2.2 liter motor that easily moves our little cars. Curly

[I]Lighter weight helps performance AND mileage.

There's your answer. Leave off the rear spoiler to save weight.

http://chevyhhr.net/forums/showthread.php?t=17927&page=2

I am amazed by your tenacity also.
However Ill still stick to my tune+hypermiling theory. Everything else is probably a waste of time. I do wish you the best, but this is a serious uphill battle for limited gain that cannot be proven.

Er....ummmmm... wind resistence happens at low speeds. Hold your arm and hand out the window, hand flat/ parallel with the road first, then straight up.
Nuthin' right? Now do it a different speeds. That resistence feels a lot different at 0 mph as opposed to 100 mph or for that matter 35 mph. All testing done on a closed course by a professional driver to prove the hand out the window theory.


(Not enough of you voted for me so now I'm not the President Elect!)

It definatly can be done and aerodynamics makes a HUGE difference.
This guy here Mike on another forum http://ecomodder.com/blog/2008/01/17/basjoos-and-the-95-mpg-aerocivic/ gets something like 85 MPG @ 75 MPH out a basically stock drive train with aero mods to the car. Now I would never do anything like he has to my car but he has proven it can work and make huge improvements. He has also done many of the very things I was told here would not work.
It takes horsepower (gas) to overcome wind resistance and accelerate weight. Lose weight or improve wind resistance mileage improves. Thing is what looks aerodynamic is not always so.

He has also done many of the very things I was told here would not work.

Then quit asking us.

And you have a nice day to.

..reduce the size of the mirrors(or remove them)....close off the front grill as much as possible without affecting cooling(can be reducted from underneath)
apply front and side flexible skirts (along with lowering)figure out best milage
at cruise and gear accordingly....tune...open up exhaust system...leave intake alone(you want small intake runners to keep velocity high to ensure the best possible atomization possible)..remove all intake obstructions,including any odd shaped curves and such....really other then a tune theres not much you can do to these motors... could try cam timing(experiment)..regrind the cam...shave door handles...plexiglass fog lites to smooth opening....slightly flare out front edge of front fenders to help evacuate air from front areas(air from radiator has to go somewhere,better to exit then go under car)..anything else you need a wind tunnel to find.wanna go race?Do a ProMod rear spoiler...gets rid of the back vacuum while allowing more rear downforce(not that you would see it below 80mph)
All common sense backyard fixes..you gotta remember your driving A box...if the numbers are that close to a vette whats that tell you...it doesn't leave much room for improvement!Oh..heres another racer trick..vacuum pump on the motor..can see 7-15 hp easily(lets see the arguments on that!).Theres and old seat of the pants test on aero's...go 50mph,neutral,coast..log time to 25mph....make changes,retest..takes along time but eventually you may hit on something..run the skinniest tires you can get away with...belly pan..close up the rear area below the bumper fwdto axle...theres more but this got too long already.....all food for thought...after thought,lose evey bit of weight you can..including 100 lbs of stereo equip,spare,evrything...once sawa 70's cadillac with the bIG motor turn 11 sec 1/4's,of course it was so stripped it was unstreetable,,..but it proved a point about WT

And you have a nice day to.

LOL, don't let him get you down...lol, he's been grumpy since he's in dire need of a bigger "snail".

I am not saying i cannot be done, I'm saying that it has ALREADY been done. That what GM does for a living...make cars....they put alot of money into this. Many other manufactures do also. Name a car that has equal of more cargo space and gets 32 on the hwy? If you want to do useful aero mods, take a look at the prius, insight and volt. Get out a hammer and start pounding on your roofline. Get used to that shape, you'll be seeing much more of it in the future unless we discover more oil than the Saudis have in the gulf of mex. I mean if you do all the stuff to your car in the above post (not a bash just making a point) what gain do you think you'll see.....? 2 mpg maybe 4...lets get crazy and say 5. That's brings you up to 37 on the highway, and you car will look like @SS! You can do better , but probably with maximum effort and minimal gain.

Or just hypermile when you want to conserve (yes I know you don't have an SS) and drop the hammer on honda with a big wing when applicable :) No mods required. I pulled 37.4mpg driving from akron-canton airport in Ohio, to Mohican national? forest about 2 months ago. Trust me its hilly arond mohican, and i never went below 60mph. Thats over 80 miles. Maybe if i was tuned, upped the pressure in my tires to 39psi tried it agin, i'd get 40 even. That's plenty...do you agree?

There are things that work and I want to take advantadge of them with in limits. The Honda that Mike has made all of the aerodynamic changes to gets excellent mileage but it is NOT for me! I want a car that looks nice and performs best for my needs. He has proven beyond any reasonable doubt that it works but it is not pretty. IMHO
I realize small changes make small differences but I still want to be careful that I am always making improvements and not hurting my goals.
Removing mirrors would help some but that would defeat the purpose by making it more dangerous and less fun to drive. Not worth it.

Clevelandhhrss, I completly agree that hypermiling tecniques will make a big difference but will not start on that until my mechanical mods are done. I do not want to mess up my results or testing. After that I will try to learn more about hypermiling. Like Mike with the Honda aeromods you have proved driving makes a difference. There is more than one way to skin a cat as they say.
Where you and I differ on opinions is mechanical mods. I beleive that with the right changes I can improve mileage and do not accept that the car is perfect for all uses from the factory. We agree on driving but I am not to that stage yet. For me it is one step at a time to test and verify.