k - seems to me I read in a thread here that it is possible to 'recalibrate' (if that's the right term) an HHR automatic transmission so that RPMs of 2800 - 3200 occur at the speeds a driver most often uses.

This was easy to handle with my Toyota 5-speed, but this auto trans thing is really making my carbon footprint bigger!

Any thoughts?

Thanks!

If your that worried about a "Carbon Footprint" you should have bought a Prius. :D :lol: Atleast your not driving a new Chevy Suburban...

I never heard of that. Its an auto, I just let it do its thing. At 70 mph, mine is running ~ 2500 rpm. At 40 mph, mine shifts into lockup mode and 1500 rpm. I'm averaging 30.3 mpg since owning the car new, now 39.3K miles on the clock.

Well, this is a "company car" and I kind of HAD to buy it. White decals on my low-to-the-ground silver Corolla just wouldn't cut it. :D

(PS on the Prius - if it lasts over 100,000 k it will then begin to compensate for the huge carbon footprint created by its construction. No Prius for me!)

I just wondered if there was a way, that's all.... ;)

Try driving in "I", it keeps the rpms higher.

I'm confused. While running at a higher rpm MAY increase efficiency(BSFC) , it increases exhaust volume ( and fuel usage ),So whats to gain? This vehicle is so controlled the only real change you may see in "footprint" (not including tuned cars which will richen up at certain points) is the VOLUME of exhaust that it exhales.And the Prius thing,gee..you'd rather drive a 30mpg car instead of a 60 mpg car because of the way its built? Last I heard , all cars are built this way and you buying one more is not going to change anything in that aspect,as the manufactures usually set a production limit.Thats why there are always leftovers on the dealer lots. Wonder what he uses to heat his house? Forbid he has a fireplace. Sorry , its hard to understand what goes on in the green mind. The cruise rpms were set to minimize emissions,raising them counter acts this. Ever notice why the sniffer insp stations ran them up 2000-2500 rpms?(Wow.theres a thing of the past!)(Sigh)

the main thing that would help is to change the gear ratio , at highway speeds. if it could be calibrated to go through the gears faster-change at lower rpms- this may help a little in town. i wish i could change my top end gear , since i average 200 miles a day over 60mph , and most of that averages over 70 mph. i average almost 25 mpg -i calculate everyday- not by the display on the dash. but it ussually says about the same. i wish i knew how to get it up to 28mpg. i drive it easy and keep an average of 27psi (hot)in the tires. i pay for my gas and it really adds up very quick going at least 270 miles a day and some days 500 miles. proven suggestions are welcome. if gas stays at around $1.50/gal thats-3mpg x 60gal- at least $10 a week , and yes i need that $40+ per month.

Up the air pressure to 32-34. If you are on the highway @70 mph you should be running at 2500 rpm or so. If you accelerate slowly, my car goes into lockup at 40 mph. There are lots of hills in that part of NC, is your car down shifting getting around? I do lots of "coasting" when I'm on the road keeping away from bumper to bumper tailgating leaving lots of room in front of me (3 second rule).

Up the air pressure to 32-34. If you are on the highway @70 mph you should be running at 2500 rpm or so. If you accelerate slowly, my car goes into lockup at 40 mph. There are lots of hills in that part of NC, is your car down shifting getting around? I do lots of "coasting" when I'm on the road keeping away from bumper to bumper tailgating leaving lots of room in front of me (3 second rule).

i'll up the pressure, but it may be a little ruffer- i can take it but the suspension may wear a little quicker. if it saves me enough on gas that should offset the cost of parts-i use a lot of gas. eastern nc is not very hilly and ncdot did a good job leveling alot of the interstates-my routes are east of raleigh/durham. i allways coast whenever possible , and go over the speed limit down hill , and less than up most hills. my route starts at 4am so not in much traffic. i also only tailgate if i need to pass some one that is way below the limit. unfortunately i'm always over the limit-if i get just 15 mins behind i get stuck in mourning traffic-cost me anouther hour + gas- sitting and stop n go. it's kind of a catch 22. i have tried going slower to save gas , it just didn't work out. i believe a few mods will be worth it for me - if they really help.

http://chevyhhr.net/forums/showthread.php?t=18369

The thread above has similar discussion about this. Some was changing tire diameter to get better mileage.

I could be wrong but the gear change for your final drive is what you most likely need to change. The TCM or tansmission shift points can be adjusted for their shift point, however driving in "D" or "I" gear will do the same.

When I drove a stock car, we changed engine rpm by changing the size of both rear wheels and tires. This was a while back in the 70's.

http://chevyhhr.net/forums/showthread.php?t=18369

The thread above has similar discussion about this. Some was changing tire diameter to get better mileage.

I could be wrong but the gear change for your final drive is what you most likely need to change. The TCM or tansmission shift points can be adjusted for their shift point, however driving in "D" or "I" gear will do the same.

When I drove a stock car, we changed engine rpm by changing the size of both rear wheels and tires. This was a while back in the 70's.

thanks for that thread. i do not understand about the "d" or "i".

"D" in the HHR has the drive/overdrive, and the "I" is the lower gear under the Drive.

The "Drive" with the Automatics is mostly for the direct(3rd) and overdrive(4th). I know this has been discussed on the forum. The best known secret with the "Intermediate" drive(2nd) is shifting to "I" and full throttle will get you past the 108 Mph mark. (Disclaimer, Do not attempt this unless you are a professional driver under controlled conditions.)

The Prius does more longterm damage to the environment than a Landrover Discovery...

Just for reference my RPM with the taller tires is 2950 at 75 MPH.
2450 at 65. Do not remember what it was stock, I have it wrote down somewhere.......

I would like to know what the BSFC is for these motors if anyone knows?

Now on to mileage. With the stock car I was getting 31 MPG @ 70. Now I am getting 35 @ 70 and if you add in the 10% speedo error it is 38.5 MPG @ 70.
Mileage improvements appear to be the best in the 70-75 MPH range and have not changed as much faster or slower.
My city mileage has went from 21 to 26 with the exception on the last tank that went stupid?????

Note my mods have helped a little but do not expect full results until all mods are complete. Mainly the tune to calibrate the timing and fuel curves to the mods. Mods I have made so far:
1. Airiad intake filter
2. Lowered car 2 inches all the way around
3. Solstice wheels which are a little taller. 10% speedo error
4. Front air dam
5. 2.4 complete exhaust including down pipe and cat. Then added Cherry Bomb Vortex Muffler. Now it really breathes and sounds good.
6. 2.4 Intake manifold.

Upcoming mods
1. 2.4 Throttle body
2. trifecta Tune
3. Underdrive pulley.

The car breathes better now so the fuel curve is probably a little off as is the timing. Vince at Trifecta is going to help me get the perfect tune for this car and I will post the results. I have talked to him and let him know my goal is more mileage than performance. I fully believe and hope I can get the mileage up to 28 / 40 highway @ 70. And still have a car that looks good and even runs better than stock.

And for full disclosure I do not do mileage tests in strong wind or hills etc. The taller tires may help on level ground with no wind yet may hurt more up hill against the wind. That is a variable we do not know about but I can say the taller tires has helped some in my mileage tests.

Performance- my car is just as fast maybe a little faster than stock even with the taller tires. If I was to put the shorter stock tires on it she would run even harder.

It appears that my mods are working but until everything is complete it is difficult to say for sure and how much. Some have told me that the mods I have made will only hurt the mileage and if so I will be eating crow right here (hope it tastes like chicken!) How well the mods work or how the crow tastes I will post it here. Curly

Seems, if controlling RPM's at specific speeds is something you want, the five speed would have been a better choice.