RPMs and Auto Trans
 

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)

gears
 

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).

yep and nope
 

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.

https://www.chevyhhr.net/forums/fuel-economy-hypermiling-47/mileage-mods-strange-results-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.