More MPG info...
 

For starters, check out this site: http://ecomodder.com/
Lots of tips, ideas and experimentation on how to get better MPG, if that's something you're interested in.

Now what about the low, cold weather, mpg with the HHR. I did some research and data collection. And this is what I found out:

1. The outside ambient (the one in the front bumper) sensor is just a thermometer. It's a convenience item and has nothing to do with the ECM.
The 2 temperature sensors that matter are the coolant and the one in the MAF sensor. The coolant sensor you can see on the readout. The intake sensor you cannot. Assuming the ambient sensor is correct (and often it is not due to direct sunlight or road heat on the front bumper) that is the temperature of the air going into the motor.

2. The problem is the coolant temperature sensor bottoms out at 5 F. So the computer doesn't "recognize" anything below that. The other problem is the computer does not "recognize" idling, at least not in the way you might think. Over 6 consecutive cold engine starts with a 5 minute (exactly) warm-up period, under various temperature differences (-6 to 27 F) and under various loads (all accessories off versus all accs on), the DIC shows nearly the exact same amount of gas usage every single time (only 0.8 to 0.9 percent). In other words, the HHR's ECM applies a fixed variable to idling.

What this would mean, to me, anyway, is you absolutely cannot rely on the DIC to provide a consistently accurate measurement of gas usage. Better to rely on your own calculations.

The obvious question: why so poor gas mileage in cold weather? There has been much testimony supporting this. I think now the short answer is: that's just the way it is. The tried and true ways to get better mileage? Think friction, weight, resistance, drag, O2 density, etc, etc. Visit the ecomodder site. They offer all sorts of advice. And they do some very radical stuff.

In the meantime, I guess I'll just have to accept the HHR is not the gas sipper I expected... orrr, keep tire pressure up, the filter clean, drive slow, live and work close to a highway and move to a warm, dry climate. One could also try to fool the ECM into accepting a leaner (less gas) mixture going in. But that's far from a guarantee one would get better MPG, no matter what or how you do it.

I hope this was helpful.

That is some very interesting data that you have gathered. Didn't catch the part in your post about what your actually mileage is and what you believe it should be.

And fwiw. My SS has the RPD that does give you the inlet temp. It will vary a few degrees from the ambient temp, depending on conditions.(yes, the picture is from back in warmer weather)
Attachment 15790

Here's his original mileage thread....

https://www.chevyhhr.net/forums/problems-service-repairs-42/2011-hhr-lt-poor-gas-mileage-49369/

Of course it almost goes without saying, but the most accurate mileage computations are still the ones you do with paper and a pencil.

Thanks Mike for the reference thread.
After reading it, it appears to me that really cold weather is just a killer as far as gas mileage is concerned for the HHR's. Don't know how you folks tolerate that cold stuff.:lol:

I'll just stay down here in the balmy South and get my 27-28 mpgs year round in my SS.

Yes, thanks to Mike for clarifying.

My point was to offer, possibly, some insight as to why - that's a big "why" - the HHR suffers poor gas mileage in very cold weather. I thought, maybe, that I would find a temperature point where my HHR's 2.2 would show a marked decrease in efficiency. Was I able to find that out? According to the DIC, no. Would accessories on/off make a difference? According to the DIC, no. Can poor, cold weather gas mileage be attributed to long(er) and more frequent idling? I would tend to think so. But according to the DIC, no.

So the question remains: why such a significant decrease in cold weather performance and efficiency? And can that be improved? Right now, who really knows. I'd like to try to find that out, though. In the meantime, it's do what I can to maximize mpg.

Why am I sooo concerned about mileage? Because I am suffering from a minor and temporary case of buyer's remorse. I'll get over it.

Finally, you may have thought "Well, didn't you check the EPA estimates?" Of course I did. But the operative word is "estimate". I know for a fact my wife's car gets significantly higher mileage than the EPA estimate. And I've read lots of testimony the HHR will achieve averages in the 30+ range. So, yeah, the "low" average I'm getting is frustrating.

One point.

If the ambient temp has nothing to do with the ECM, why does the OBDII report it?
Mine reports ambient and intake temps, they usually vary by about 20F after warm up. I'll go look up the PIDs if you want me to.

Another point.

The MPG computation is done mainly using the MAF and HO2 sensors, the computer knows what the air/fuel mixture is from the O2 sensors, then calculates the fuel usage from the actual air use. (incredibly simplified)

Every car I have ever owned that I cared about mileage on has gotten less fuel economy in the winter than in the summer. I typically lose about 3-4 mpg during the winter. I only remote start my car for less than 30 seconds, usually when I am walking up to it. My wifes 2010 V-6 Camaro is done 2-3 mpg also from the summer.

To be honest Don, I don't know anything about how an OBD2 shows efficiency (using the leanest possible mixture without significantly affecting performance). The OBD2, I believe, shows sensor faults. Is that correct? Again, I don't really know.

The question is, I think, how rich is my HHR burning? Is it burning "too" much? Can it burn less? And how? My test data shows there's no way to know simply by looking at the DIC. Changing the variables does not change gas usage on the DIC. It's always 0.8 - 0.9%, no matter what you do. And why is it that the coolant sensor only reads down to 5 F (have to wonder)? Also, on 1 of 6 of my 5 minute tests the ambient sensor reported 39 F while the actual air temp (and the coolant temp) were the same at 23 F. Did that change the outcome? Nope. According to the DIC, the result was (yes) 0.8 - 0.9%. Doesn't make sense to me. And without talking to the ECM engineers directly - no doubt they are bound by confidentiality - my questions are likely to remain a mystery. I think in the end it will be much experimentation
- unless I get bored first or give up.

The bottom line: I might be able to live with it. But there's NO way I'm going to accept 22.3 mpg (current reading, if it's correct) is the standard for a 2.2, cold weather or not.

I think you'll find that your fuel economy numbers will improve with the arrival of spring. All vehicles use more fuel in cold weather, you're up against increased rolling resistance, increased frictional losses, increased time spent in "Open Loop" operation until the engine reaches its optimum temperature, etc.

It's nothing to lose sleep over, and don't buy everything you see on various "Hyper Mileage" sites, some of their ideas fall straight into the realm of "crackpot science".

I have an old law school buddy who drives one of those Ford C-Max hybrids, he's a member of their forum and one of the members there went as far as clipping the little rubber nibs from the tire sidewalls in an effort to "cut drag".

Ryan did get a check from Ford when they got caught overstating the mileage on the C-Max cars, they sent him $450 to make up for the car's inability to break 42mpg when they said it would do 47mpg...guaranteed.

P.S. as I've said before in this discussion, and over the years, don't take the DIC mileage readout as gospel. A pencil and paper are more accurate.

A.) 14:1 is pretty much maintained, or at least sought at all times.
B.) another winter gas burner is that the defroster runs the A/C, as does the recirc.
C.) OBDII shows all of the data that the "computer" will let out.
D.) I have found the MPG calculation to be exactly the same as my Excel spreadsheet, taking into account my 215-60X16 oversize tires.

When I bought my 2.2 panel, I did so not to go fast but to look cool getting there. Decent fuel economy would have been nice though. I see the posts 30+ mpg and marvel at the possibilities. When I drive like Granny going to church on Sunday I get 29 with a pencil. So I usually drive it like I want and only fall to the 26-28 range. I may change my intake this year. Bloggers say that does make a difference.

Highway MPG i.e. all at 55 MPH should get around 30ish. Any traffic involved in your drive to church will drive that down to 26 ish.

Things are getting interesting and not in a good way. I filled up today with the DIC reading 21.9. When I did a manual calculation, 18.9! WHAT?! You gotta be kidding!

On to the next experiment: clean MAF and see what that does.

Maybe it's time for a survey. Anyone game for that? I hope so because I'd like to get to the bottom of this. If you would here's what I would like to know...

Year
Motor (2.0, 2.2, 2.4)
Transmission (auto, 5 speed)
Climate (cold, warm, wet, dry or various)
Driving (flat, hills, country, city or various)
Style (aggressive, easy or various)
DIC readout (what does it say right now)
Manual calculation (would be very helpful)

It would be fantastic if you volunteer. Please do not embellish or provide any other info.
Also stay with the format so we can get a clear understanding of what may be going on. Post
your stats here on this thread. With enough data we can spreadsheet this and see what
answers we can get. Thanks!

This type of survey has been done, informally, in ALL the threads and posts made regarding, "Help, I only get XX MPG at 110 MPH", "Somethings wrong I get 40 MPG in the city", etc. etc. You could read all those.

But seriously, you will gain very little accurate info, IMO....i.e., your city driving is different than my city driving, your 70 degree temperature day is different than my 70 degree temperature, your average highway MPH is different than my highway MPH.

That is why ALL manufactures use the same computer driven road course for city and highway mileage ratings. Although, the vehicles are "driven" (on dynos) by humans, the software indicates specifically when the driver is to accelerate, brake, coast, idle, etc. and for how long and the type of pedal pressure application. This was agreed on and mandated by the Federal Government. It brought increased uniformity, honesty and validity to the MPG ratings on the window sticker.

Oh, I forgot to indicate......the test dyno cells are in a barometric chamber, which controls temperature, humidity, pressure, etc.

we would have to correct for altitude, air density, squirrel fur on the bumper, bugs on the headlights all kinds of factors effect mileage, I just know its much better on the highway in the spring than stuck in snow and traffic in the city during winter.

Exactly Oldblue.
And mine stays pretty much the same year round because we don't have those extreme weather changes down here on the coast.
Well, except for those high humidity, 99 degrees summer days. :lol:

11, you're really overthinking this, there are too many variables to even make the data quantifiable.

I think that if you just relax a tad, and get to the warmer weather that is coming as spring draws near, you'll see your mileage improve once you break free from the Arctic temps you've been seeing.

HHR mileage can be all over the place, and as the EPA says when vehicles are given their fuel economy numbers, "You're actual mileage may vary".

^^^^^^^^:thumb:^^^^^^^

Obsessive would be more like it :lol:


Oh, and for what it is worth, your hypothesis regarding how MPG is calculated appears to be incorrect. I found this 2011 article on Edmunds.com after they found discrepancies in dash readouts and manual calculations. Make from it what you wish.

Roger Clark, senior manager of GM's energy center, explains that the fuel economy gauge makes a calculation by counting the number and duration of pulses made by the fuel injectors as they squirt gasoline into the combustion chambers of the engine. The onboard computer system divides the distance the car travels by this estimated fuel consumption.

Clark says the gauge is "dead nuts accurate" — if you consider all the variables at work during driving, including temperature, driving conditions and driving style. The biggest fluctuation occurs because ethanol, which is blended with gasoline in varying amounts, contains less energy.

"When you fill up, you are paying for a gallon of gas, but the energy in that gas varies significantly," Clark says. This means that while the car's computer assumes the gasoline is providing energy to drive a certain distance, the fuel might have less energy and not propel the car as far

Here's a link to the article in entirety.....

http://www.edmunds.com/fuel-economy/...s-fibbing.html

Today I did over 700 miles 98% at 72 MPH cruise control on ambient temp was in the 50s F. to my surprise I got 31.5 MPG. 2 weeks ago 700 miles at ambient temps in the single digits got 25 MPG.

This is the point exactly.

Where I am (Northeast USA), the temperature is up (40's) and so is my mileage. Nothing else has changed. I use the same gas, same gas station, same gas attendant, same gas pump. Same driving, same routes, same roads, etc. Nothing has changed except the temperature. I did clean the MAF at the beginning of the warm-up so I can't isolate the increase to temperature alone. Although I suspect the MAF cleaning didn't do a thing.

The survey is intended to try to isolate the cold weather, poor gas pattern in some way. Is it a particular year, motor, transmission, climate or a combination of things that is causing the loss in efficiency? Most importantly, is there a fix?

It's ok if there's not any interest in the survey. It does require a commitment.

Regarding being "obsessive". I disagree. Although maybe I have not been expressing myself correctly (Sorry, I'm not one to use emoticons).

For research sake a trip to southern Texas should get us 45mpg. Might be worth moving south...:propeller:

Yes I notice the extreme cold kills the MPG on this car. I normally get 29/30 on the highway, light hills 75mph, but when it is -9 like it is today I am lucky to get 24/25.

Also this car seems very sensitive to 10% ethanol blends. In MI we have 10% in our gas, if I travel to a state without that the MPG goes up. It is all relative.

Pretty well documented more ETOH=lower MPG.
Many localities change the percentage by season, that's what 843de keeps trying to tell people.

I still haven't figured out how the temp plays a roll, did it again today. One tank of gas all highway 120 miles at <20F got 25 MPG, return trip >32F got close to 30 MPG.
Maybe transmission fluid gets stiff? I did notice some odd shifting behavior today.

Could be the cold air is messing with our airflow sensor or the O2???

One would think cold air = denser oxygen rates right?!

The colder temps means the engine takes longer to heat up, remote starts cause 0 mpg and the heater is running to try and warm up the interior of the vehicle.

colder air to me should seem as to better performance, no car likes hot a$$ air being put through it confuses me a bit but who knows, shouldnt the colder weather be keeping everything like tranny oil, antifreeze and such cool to a good performing level?

Could be turning tranny fluid into molasses too. Who knows, just observations.

Another long highway trip today Fredericksburg,VA to Winston-Salem,NC. About 300 miles each way. Trip down starting at 3:30 AM ambient <40F ; 28.7 MPG. Trip back 8:00 AM ambient >60 ; 32.7 MPG!!!!! That is spreadsheet calculation, the DIC was lower.

This trip is all Interstate Highway except for 7 miles, did not get much traffic in the AM rush in W-S, only about 5 minutes slow traffic. AVG speed 65 MPH cruise control mostly set at 73 MPH.

Colder air is denser than warm air, so it is easier for the HHR to punch a hole thru warm air.

My HHR is the same as others, much better mileage when the temps rise. Don't forget added drag from stiffer grease in the wheel bearings too. Alternator bearings also.

As Snoopy alluded to earlier in this thread: the DIC MPG reading is always "dead nuts" correct. The amount of fuel injected into a cylinder is governed by pulse duration - the amount of time that the poppet in the injector is opened to allow fuel to pass the nozzle. This is always a precisely known quantity, because the dimensions of the passage in the injector is fixed, and the delivery fuel pressure is tightly regulated, so the flow rate is constant. Only the amount of time that the injector is open is variable. There is no question of how much fuel is burned when the engine is running.
If the outside diameter of the tires on the vehicle is the same as when the vehicle left the factory, then the distance the vehicle has progressed is a known quantity. Let's not get into tread wear, which decreases the diameter - it is too negligible to even be considered.
The ECM adds up the amount of fuel burned (whether moving or standing still), and it totalizes the distance traveled. Distance traveled divided by total amount of fuel burned is miles per gallon, or kilometers per liter, or whatever. There are no estimates, presumptions, or corrections applied. It's how much fuel you burned (not put in the fuel tank) and how far the vehicle has progressed (forward or backward).

The amount of fuel injected into a cylinder via electronic fuel injection is determined by a complex algorithm developed using inputs from various sensors. The objective is always maximum efficiency within acceptable exhaust gas chemistry parameters. Greater fuel consumption in cold weather has very little to do with the operation of the engine if all sensor inputs are within specification. There are dozens of variables not connected with engine operation which make decreased MPG inevitable, which is a whole other topic.

The ambient temperature sensor is definitely an input to the ECM. If you park your HHR and the ambient temperature is, say, 30 degrees, and you start the engine up some time later and the ambient temperature is 40 degrees, your DIC reading will still read 30 degrees until you drive a certain distance, and then the ECM will update the DIC display. If you park your HHR and the ambient temp is 30 degrees, and then start it later and the ambient temperature is 20 degrees, the DIC will show the correct ambient temperature immediately upon starting. This is done to prevent the engine running in an open loop mode due to a failed sensor input - very unlikely since the ambient temperature sensor is a precision thermistor that cannot be wrong unless the circuit has no power.

Thank you Kornellred. I didn't want to go into detail because people believe what people believe.....as illustrated by some of the posts to this and other threads. A lot of misconceptions here.

And as far as I know (limited admittedly), you are dead on.

Whoa, no one was saying that you or Kornellred or anyone else was wrong. Just some of us have anecdotal experience that cold air = poor MPG. We don't know why, we didn't state there was a reason, we just experience that.

I believe Kornellred is 100% correct, the DIC won't lie, it will tell you the mpg exact. That is if everything is working right. Don't forget that same DIC is telling me that I don't have any air pressure in my left front tire. But I believe that 99% of the time it is accurate.

So, his post does not refute any of the experiences we have had, I only use my DIC to calculate MPG and I can tell you that IT DOES confirm that cold ambient temps give me worse gas mileage.

Any thoughts?

Start at the beginning and read all the posts. You will probably understand what I have stated.

Oh that is like 3 pages ago... I have gone too far to go back to the beginning ;)

Not to mention the computer uses the data it is given; if your tires are different than it is placarded for, the output will me incorrect. My mileage is a bit off because I run 215-60X16 tires and the placard is 215-55X16.

G I G O!

For those who may care - and I do not think that there are many - I want to elaborate on my comment about the "dead nuts" accuracy of the DIC MPG figure. While my explanation of how most common fuel injectors work is basically correct, I stated that the flow rate of fuel through the injector is always a known quantity. That turns out to be true only if the fuel pressure is essentially a constant. In order for the fuel delivery pressure to be constant, a precision regulator would have to be employed, and there is no such apparatus in the fuel systems of the 2.2L and 2.4L Ecotec engines. There is an acceptable range of fuel pressure of 50 to 60 psig associated with the correct operation of the electric fuel pumps used in our HHRs. This means that the flow rate of fuel through the injector can vary somewhat depending upon fuel pressure, and that variation cannot be precisely measured (it need not be, either).
This seems to imply that the fuel consumption figure is a more complex calculation rather than a straight addition of known flow rates for time periods of specific duration.

The term ["dead nuts" accuracy] is a somewhat impolite colloquialism for a measurement that cannot be made any more precise. In terms of fuel consumption measurement accuracy with respect to DIC MPG readings, there may be room for improvement, but there is no reason to add the expense. The current level of accuracy is remarkably precise for all practical purposes.

Just sayin'......

I do it the old fashion way and calculate mpg. Rarely does the DIC match the calculated value. I will look at two DIC values: miles traveled and miles remaining and when they add up to 500, it indicates that I'm getting over 31 mpg. [( mt + mr)/16 gallons ] The DIC will read 29.

I don't collect DIC mpg data, but do collect the calculated values.

My overall MPG average (129,000 miles) has been 30.3 mpg with a standard deviation of 2.9 mpg.

Time for an update. A few weeks ago there was a brief but significant
warmup here in the NE, from the teens to the 50's. At the same time as this
warmup, I took a 2 hour road trip to get some batteries (for a solar/backup
power system I'm putting together). The trip was @ 85% highway.

To start, I filled up with gas, checked tire pressure and zeroed the numbers
on the DIC. To my delight MPG starting climbing immediately. And really
started climbing on the highway. Just shy of 1 hour of driving, about the half-
way point, the DIC went from 25.1 mpg to 31.8 mpg (!). And it was still
climbing when I pulled off the highway to get the batteries. So what was it?
If the DIC is "dead nuts accurate", then there has to be a reason why the
sudden increase. Was it temperature? Or was it highway?

I'm not convinced it was highway driving alone. It was mentioned earlier in this
thread that maybe cold wheel bearings or cold transmission oil could be the
problem. The HHR is "stiff" and being held back. I think that's a very good point
since I've noticed mine too has quite a stiff, sluggish feel for a good 10 minutes
into a cold drive. Certainly something to consider.

And now about the batteries. I threw into the back of the HHR about 300
pounds of batteries ( By the way, don't try this at home. The plastic decking over
the spare tire started to buckle. I caught it just in time before I did any
real and permanent damage). Then back onto the highway I went. You can
probably guess what happened next. The DIC immediately started trending
downward and lost nearly all the MPG gained by the time I got home. I was
down to 27. 4 when I pulled into the drive (bummer). Forget about temperature.
And forget about highway. The added weight was a killer.

So what have I learned. The HHR is NOT a truck. That's what I was driving previous
to the HHR, for about 6 years. Nothing effected that thing (old Ford Ranger). Cold,
heat, weight, no weight, good gas, bad gas, nothing effected it. But the HHR is, well,
sensitive. You have to keep it warm and its' burdens light. Do that and, occasionally,
you can drive it hard for satisfaction. Be kind and gentle, too. Take care of it and it
will take care of you.

Gee, where have I heard that before?

You were driving down hill on the way over and up hill on the way back. :lol:

I'll see similar mpg fluctuations. I'll drive north on I-95 through central Florida and will see 31 mpg, but on the way south, the mpg drops? :intresting:

Or wind... we basically have giant boxes with wheels, very poor aerodynamic properties on this car.