Tested rpm-mpg
 

I ran a test for baseline and did it 3 times to verify.

57 mph on cruise on a 10 mile stretch with a couple decent climbs/descents.

6th gear= 2000 rpm and 49 mpg
5th gear= 2490 rpm and 44.5 mpg
4th gear= 3000 rpm and 39 mpg

Seems to show that less rpm is certainly better. I have room to go up on tire height but 27.5"-28" OD would be maximum. Current tires are 25.5" OD so around a 10% reduction in tire rpm will net how many less rpm's?

This shows the potential mileage that the manufacturers of all of those high cruising RPM MT cars are leaving on the table that could be attained via an inexpensive gear ratio change. Those 40mpg MT Fits and Yarisis could easily be 50mpg cars running in Prius and Civic hybrid mpg territory if they were geared properly for highway cruising and their engines would also last longer.

10%

When you change tire diameter, any vehicle specific MPG meters will be off as will the speedometer. You'll need to recalibrate or use a correction factor, 10%, to be able to compare with your baseline.

LATE THOUGHT: Rather than buying four new tires, buy one and a full-size rim. Then put it on a front and later rear wheel to test for interference. It is a lot easier to 'eat' the cost of one tire than four.

You can also get just a second tire and then put them on the drive wheels. Often this is enough to test your hypothesis about revs/mile and vehicle efficiency without having to put so much money into tires.

Bob Wilson

My odo is 2.8% low compared to my GPS anyway so recalibration would not be a problem.

10% would be a start as it shows every little bit helps.

Yeah, a lot of MPG is left on the table in the Honda manuals. I would love to know what my Element could do at, say 2300 rpm vs 3500 rpm when cruising...

is it a 4 or V6?
It will probably drop your rpms to 17-1800. Which could be a sweet spot for a 6. I don;t about the 4 bangers.

But given the potential drop in rpm, It would be worth it.

The v6 Sonata is gone as of the '11 model, replaced by the turbo 4.

But we also have the Garage for that sort of question ;).BHarvey's '11 Sonata

The CR-Z runs 2400-2500RPM at 60mph and it's only a 1.5L in a 2600lb car. Some of those guys are getting 40's to 50mpg tanks

Most manual 4 bangers run high 2000's to 3000RPM at 60mph. That leaves a lot of room for improvement and people are going complain to complain either way about these cars being underpowered :D.

my 29 year old car at 60mph (97ish kph) turns 4300rpm
and i still get high mpg's imagine wgat i would do if it had the power to turn lower rpm

cant wait till i put my fuel injection setup on, it'l be nice to get some waaay higher mpgs

I don't know why people complain about power, it will spin it up in first gear and start to in second, and this is with TC on!

The 92-95 Honda Civic VX and CX turn 1925rpm @ 60mph (2000rpm @ 100kmh). My CX when it had its original engine with 70 horsepower had enough power to maintain speed on all except for 3 of the uphills on the interstates in western NC. And on those few hills that it won't maintain speed on in 5th, well, that's what 4th gear is for.

...a very crude "rule-of-thumb" estimation of MPG for our Cruze LTZ seems to be:

MPG ~ 2000 / MPH

Exactly! Honda has been downright stupid with gear ratios since 1995. :( Exceptions were the HX which was ok but not great and the Gen1 hybrid but that had other stuff tacked on. Even now, the new Hf model they're advertising... automatic only.

Showdown: testing RPM vs. MPG at a fixed speed - MetroMPG.com
http://www.metrompg.com/posts/photos...-mpg-geo-x.jpg

Ugh, stop, you are bumming me out. My Element, with plenty of engine and plenty of torque, is geared so low. At 60 mph, I am running 3000 rpm. If it were properly geared, it looks like I could break 30mpg on highway tanks, vs the ~26 I get now. Sigh.

I find it also pays to get into top gear as soon as possible so you can get in early on the mpg savings from the gear lowered rpm.


My car will idle along in 5th gear without throttle at about 27mph 950rpm up gradual grades without issue, at idle. I think or expect this to be its top mpg cruising speed as it using the least fuel possible.

Guess I should be very SMUG with the fact my honda does 60 mph at 1700 or so rpms? :thumbup:

I find the speed of my sidekick isnt linear according to the odo. For example as I approach 45 mph it goes up to 5 mph off. As I approach 50 mph-60 its dead on, when I start to go to 70 its 5 mph faster. This is using a tomtom gps as a reference.

So, I slow to 40 in 45mph zones that have cops present, then go 5 over elsewhere. :thumbup:

Having a "radar MPH" on-the-vehicle would eleviate that problem.

Now I know what you guys were talking about with the talllllll gearrrrsss on the vx / cx trannies! I came from an lx manual to a vx, check my rpm / speeds (custom econo - light above 4500 rpm, not CEL above 5500 rpm)

BEFORE:

75mph, about 3000 rpm
http://rs1291.pbsrc.com/albums/b551/...0?t=1403493898

80mph, about 3100rpm
http://rs1291.pbsrc.com/albums/b551/...49.jpg~320x480



AFTER:

80mph, about 2600rpm
http://rs1291.pbsrc.com/albums/b551/...c2.jpg~320x480

about 71mph, about 2400rpm
http://rs1291.pbsrc.com/albums/b551/...0?t=1403493880
I'll put up a couple more speeds / mph's when they finally upload!!:thumbup:

I bet Honda is building the cars to do well in the epa testing and the average magazine road test. So the low gearing doesn't hurt the epa tests because apparently "highway" is not cruising along at 65mph, go figure, and road tests always show things like 0-60mph and not what rpms and gear changes it took to make it there. Vtech just kicked in yo!

vrmouseyd15b, whats the check engine light for? Some cases that can cause the computer to not allow lean burn if equipped and cause the fuel system to run at a default afr rate vs relies on the o2 sensor(s).

Think I do 2300 rpms at 70. Once you pass 70 the cvt starts to very the ratio and rpms start to flutter or float up and down. Need to reduce rolling and aero resistance or just lock the cvt ratio once merged into traffic.

Hersbird, thats what Ive said and the hybrids should be required to start the test with a dead as possible the car will let. It can take 7-14 miles to burn off a full charge on the gen 2 insight and I imagine a good bit more for the prius and so on depending on the vehicles battery size. In the mean time city mpg is artificially high.

Yes and their vehicles got bigger and heavier. I don't know if Honda had a change in management in the mid 90s or not? They seemed to have gotten away from what they once were.

No check engine light. that's my "lean burn indicator" / happy light. I'm on a jdm p2j series ECU. they should all have an "econo (lean burn)" light. I think it's at pin a30, and I'm sure it's a switched ground. I bring SWITCHED 12V POWER to one side of the bulb, and pin a 30 to the other side of the bulb. here's a shot with KEY ON, ENGINE OFF:

EDIT: When I said "they", I meant the p2j family of ecu's but - I'm not totally sure


http://rs1291.pbsrc.com/albums/b551/...0?t=1404096676

my "happy light / econo light" Is above 4500 rpm, Check engine light is above 5500 rpm. I hate seeing the check engine light because you are right, check engine light = no lean burn!

Sorry, I've been AWOL all day yesterday - road tripped into Cincinatti to pick up a second vx tranny from fellow ECOMODDER turbovr41991 !!

He's got one more VX 5spd transmission ready to go for $250 - http://ecomodder.com/forum/showthrea...ale-28931.html

Real cool dude- we met at Harbor freight by his house - and he brought me coupons!!
Thanks turbovr41991

This tranny ( and lean burn ) is how I broke 46 mpg doing 65 - 70 mph on the highway - no aero, no EOC, full interior, no kill switches or other cheating - power steering and a/c functional!

How profitable for honda and toyota are their hybrids compared to a bottom of the barrel fit/yaris?

I don't have any figures on this, but the fact that the gov't subsidizes them leads me to conclude they are extremely profitable.

Soichiro Honda (November 17, 1906 – August 5, 1991)

Japanese cars have gotten larger and US cars have gotten smaller over the last 30 years.