57.1 mpg in my non-hybrid

specter · #1 07-31-2006, 12:45 AM

I posted once here in an introduction thread and now that I picked my new vehicle I'm back. I bought a 2002 Chevy Cavalier 2.2L 5spd from Ebay for $3299 and have been using it to deliver pizza and just get myself around. It's rated 24/34 city/hwy. I was able to pull 42mpg from the automatic version (which I still own) so I was optimistic about what I could do with the 5spd. It's a good car and I like it. The only problem was that Chevy decided that it should idle at 900 rpm (0.4gph) and cruise in neutral at 1200 rpm (0.6gph) which was a huge waste of fuel. My auto with the same engine only idles at 600rpm. I suppose this is a driving aid to keep inexperienced drivers from stalling it.

The 57.1mpg I got was on a 12 mile circuit around my area. First, I took off the vacuum hose from the brake booster and blocked most of it with my thumb. The car's computer adjusted the idle air control valve to compensate and at that point, I unplugged the valve and put the hose back. The car's idle dropped to 490 rpm and shook a bit, but now only used 0.2gph when my foot was off the throttle. I also added an engine kill switch so that I could pulse and glide. I didn't want to wear out the starter so when I coasted to a red light or stop sign, I let out the clutch in 5th to get the engine going again. On continuous highway driving at 55mph, my car gets 43mpg, probably due to aerodynamic drag. If only I could eliminate the stop light idling, I think I could break into the 60's. Even if I don't, it's not too bad for a $3299 car with no batteries.

xcel · #2 07-31-2006, 02:40 AM

Hi Specter:

___How did you measure the FE over the 12 mile segment and what was your total tank including the short segment? My last tank was similar with a lot of work but I only needed to use NICE-On maybe 15% of the time and only when the 12V fell below 11.9 static under a FAS.

___Good Luck

___Wayne

Chuck · #3 07-31-2006, 08:20 AM

First of all, welcome to CleanMPG!

Those were impressive stats!

Ever since returning from HybridFest, I've been doing FAS approaching stops a lot more. It really saves a lot of fuel. Granted, not charging to a stop saves, having fuel-cut off and autostop helps more, but FAS takes it to a higher level.

lindermant · #4 07-31-2006, 09:57 AM

specter - excellent work!

andy · #5 07-31-2006, 11:14 AM

Quote:

Originally Posted by specter

The 57.1mpg I got was on a 12 mile circuit around my area. The car's idle dropped to 490 rpm and shook a bit, but now only used 0.2gph when my foot was off the throttle. On continuous highway driving at 55mph, my car gets 43mpg, probably due to aerodynamic drag. I

Um, ok...What do you have, a little gadget that shows instantaneous mpg based on inertia? How did you get a fuel flow rate? Not very scientific, and not very accurate, but I guess it gives the driver a good feeling if nothing else. 43mpg continuous IS impressive. What do you attribute this high mpg to?

The BEST way to measure mpg is over many tanks of fuel. Measure your actual miles (and don't assume your odometer is correct, because chances are it's not) divided by actual gallons of gas put in your tank. Do this for about 10 tanks, always refilling the tank to the same level. Then come back and tell us what you're getting for mpg.

If you want to figure out an odometer reading factor, use the highway markers. Start at any mile marker (mm), say mm 97 for an example, and note your odometer and trip meter reading. Drive many miles, a good 100 miles is a good distance. So, you should be at mm 197, right? Now, how many miles does your odometer (trip meter)say you went? Let's say it reads 103.4 miles. What you do next, is divide 100 by 103.4 which gives you .967118. This is your mileage correction factor, and whenever you drive a full tank of gas and fill up, I assume you reset your trip meter. Take you trip meter reading and multiply it by .967118. This will give you a true mpg, and something we can all compare our mpg to.

Andy

Chuck · #6 07-31-2006, 11:21 AM

That was not exactly the best way to make an intro

....hope the next post is more positive with a little info about your car, etc...

Spectre, it's still relatively speaking the best run you have had

tbaleno · #7 07-31-2006, 11:22 AM

I tend not to realy care if somones mpg is off by a few percent. Most people are competing with themselves and not others.

No need to get all scientific about getting it as accurate as possible. The idea is to just do better each time.

brick · #8 07-31-2006, 11:32 AM

Andy,

I don't know for sure, but I would bet that Specter is using a ScanGauge for his MPG information. That's what most of us use if we don't have a fuel consumption display (FCD) in our vehicles from the factory. It is very accurate once dialed in, a procedure that does involve comparing the ScanGauge's reading to miles/gallons calculations over the course of a few tanks.

Good point about the odometer, though. Something else that has been suggested is to use Google Earth route measuremets to calibrate the odometer. A "measured mile" is quite valuable but may be hard to find in some locations. The rest of the mile stakes tend to be mile-ish stakes, though I suppose they probably work just fine over a longer distance. Either way, good suggestion.

And welcome to CleanMPG! Care to post in the Intro section if you haven't done so already? Sounds like you have some experience keeping accurate records of your own fuel economy. There's loads of information on these pages. Odds are you will find as many others (myself included) that what we once thought was "the right way" tends to leave quite a bit of room for improvement. An open mind will prove to be a great asset

andy · #9 07-31-2006, 02:20 PM

Hey, I'm not trying to stir up the pot, but making claims of 57 mpg over a 12 mile circuit is bogus. Is this a feel good site or a scientific site? Looking down at a box that says your currently getting 57 mpg, or that last run was 57 mpg, is feel good.

How would you like it if I posted a number like 57 mpg, only to find out my odometer is off by 10%? What good is it if there is NO standard? Information on how to get better gas mileage is a good thing. How would you like it if I bought one of those things and did a run down a mountain, and posted my mpg? Wouldn't you be impressed with my high mpg? Gas mileage varies SO wildly while driving, it is not useful information, other than to the driver to know at that moment what his right foot is doing. You're talking miles per gallon, and 12 miles won't even come close to 1 gallon in his car. Is that useful information to us?

Information like: I have averaged 25 mpg over the last 10 tankfuls with a high of 29 and a low of 22. After incorporating this ONE change into my driving technique, AND another 10 tankfuls of gas, my mileage over those last 10 tanks was 31 mpg with a high of 33 and a low of 25. I can assume that my change in technique has accounted for a 6 mpg average increase.

I think this is a great site, and it has a lot of information. A few people have gone to the trouble of putting together a glossary for acronyms, etc. It would be nice to see standards on posting mpg, ie. minimum miles driven for that claim. Do you see my point?

Chuck · #10 07-31-2006, 02:52 PM

Quote:

Originally Posted by andy

Hey, I'm not trying to stir up the pot, but...

I'm glad you agreed to make your next post an intro so you won't be a stranger....people meeting face-to-face get acquainted before quibbiling - better chance of getting somewhere and more diplomatic.

As Tom said, our goal at CleanMPG is for self-improvement, so they don't require the precision you are suggesting. I might understand such exact measurements at the Tour de Sol or some other competive event.

I would be interested in knowing more about diesels like your TDI - assuming it's a diesel.