No load GPH
 

Well, I am not part of a challenge, but I was extremely intrigued by these numbers from both the ZX2 and the diesel. I had been looking at these numbers since I got my scangauge and this is what pushed me into EOC. I can see why a diesel can do very well coasting in idle. This makes sense.

Here are my numbers at 200-210 WTF and 130 IATF. Plus or minus .1 liter for my 2001 Saturn SL SOHC. I also put CO ZX2's numbers in parenthesis. A rough estimate is that power output decreases 3% for every 1000 feet increase in altitude. I will assume fuel consumption should decrease also. I am at about 2600 feet. That would explain some of CO ZX2's lower numbers but there is a bit more going on than that. I am not sure that it makes sense to use that estiimate when discussing no load fuel use where the loads are mostly friction and pumping losses. However every vehicle I have driven across Colorado got better fuel miileage at higher altitudes.

My last trip across Colorado on I-70 was in a Ryder truck that got almost 8 mpg from Colorado Springs/Denver west bound. From Boise to SLC it got only 6 mpg. That fits quite nicely with theory.

With my Scangage set to fast update one can quite certainly watch the computer in the rich/lean cycles about stoichiometric. I believe this can be observed both steady state in the mpg numbers or in a test like this in the liters/hour numbers. As for observing this on the road climbing a hill in fifth gear at about half throttle my Saturn will sometimes cycle between 28 and 30 mpg. At first I just thought is was random variation and then I was able to repeat this several times.

0750 rpm (0.13) 0.21 gph
1000 rpm (0.18) 0.29 gph
1500 rpm (0.29) 0.40 gph
2000 rpm (0.37) 0.53 gph
2500 rpm (0.50) 0.69 gph
3000 rpm (0.66) 0.85 gph
3500 rpm (0.77) 0.95 gph
4000 rpm (0.93) 1.08 gph

Enough rambling. A clean 2000 GLTDI with 90k sold locally for 8500. I thought that was a good deal. I was way too late on that one. Sort of like all the local VX cars one sees for sale. They are all sold by the time I call.

Ernie

Picture of no load fuel consumption.
 

I tried to put the different no load fuel consumptions in one place and make a graph. I thought it appeared that the gasoline engine fuel consumption was quite linear but the diesel was not as much so. If you double the RPM of the gasoline engines the fuel consumption doubles. The diesel is more complex. We all have a slight bend and 3000 rpm. It is much more pronounced with the TDI. With the ZX2 the bend probably does not excede experimental error.

It would be interesting to see the fuel consumption with each engine producing 15 hp at 2500 rpm.

Ernie

Attachment 399

I wonder if it has something to do with the turbo spooling up? Maybe once it running flat out on the TDI it smoothes out a bit? I really have no idea.

Power wise you can really feel the "pull" drop off about 3500rpm. I mean it still pulls but not as hard as it does from 1800-3000.

Off topic but what kind of RPMs are people running at 60 mph? I am about 2100. I am so close to installing a taller 5th gear, I have an option of either a 11% drop in RPM at 60 or a 13% drop. I am worried that with a 13% drop at idle I will be at 33 mph, since I drive at about 40 on the way to and from work.

Check out this thread. My Geo does 3000 RPM @ 60mph.

There were different gearing for the Metro and xfi in 94 with the xfi having a higher mpg rating due to a taller 5th gear but my old Metro 5 door was turning redline at 135mph. My xB turns 3050 at 60mph and runs ok - I don't think it would be as driveable with taller gearing.

2500
 

The 'Teg is slightly below 2500 RPM @ 60 MPH.

My Automatic variant has a taller final gear than the manuals, which are between 2500-3000 at the same speed.

RH77

The Element turns about 3000 rpm at 60mph. It needs a 6th gear and/or a taller FD big time.

I'm at the same. 2002 Saturn SL1 with an automatic. About 2400 RPM at 65 mph.

Brock-

Lovemysan gave me this thread for 5th gear swap on the 020 transmission. I am considering it for my Jetta when I get the time.

https://www.rpi.edu/~carabd/gearswap.pdf

Nice write up. BeeUU what is your 5th now? I think my stock is .75 I can go to the .68 or .65. I have been told the gassers like the old TDI 5th gear becasue it is lower then the gasser 5th, but not to low. I can get either of those gears for $325 from a couple of places and there is a TDI guru about 90 miles from me that has swapped about 20 so far and charges about $80 to do it.

Argh, sheesh. Why did Honda make so difficult? It would cost me about $1000 to do the same thing. No need to answer, just talking to myself...

I'd recomend the .68 gear. If you go too low you could end up spending more time in 4th gear, which defeats the purpose of a lower gear.
I went from a .74 ratio to .66 It's just right.

Brock-
Sorry about the late reply, I been out sick....

See the attached link for trans ratios...

https://www.techtonicstuning.com/trannyratios.asp

I beleive that I have the "CHE" transmission with a 0.80 5th and 3.67 final. I cant remember what my revs are at 60, I will have to check and get back with you. They a slightly high, higher than my Peugeot.

Friday edit - I drove the Jetta this morning. I noted 1700 RPM at 40 MPH so a calculated 2550 RPM at 60.

Thanks to lovemysan for the write up!!!

$80, what a deal.....I might have to drive out there to get it done!!!

What did I learn from my time (sentence) in the challenge?
That it isn't easy
That it takes constant diligence
That it takes forethought and planning
That it wasn't as much fun as just driving.
I haven't even looked at my mpg data since leaving and I don't mind a bit.
I'll see how much of a hit I take only when I fill up.

b.t.w. I had the Sonett out at a show this weekend. 60 mph indicated (about 58~60 calculated from mile markers) is 3400 rpm! 5k rpm is almost an indicated 90 mph.

Amen to the first three!!!!

For me at least, it has added an element of challenge to the commute which makes daily driving more interesting. The fun is when I catch a good coast, make the green light, get a good draft off the lead car and trickle into the parking lot of the store with JUST enough momentum. Or when coasting in freeway traffic when I nail the spacing just right for traffic, I have a good draft and then the silence becomes noticeable.

I find myself grinning from ear to ear. :D

I was having lots of fun until I tried EOC. In traffic. Bleah. I can imagine doing it on the open road, definitely.

And what happened when you tried it?

Every time I shut off the engine, someone conspired to kill my momentum and make me hit the brakes too soon. So I had waaayyyy more kills and restarts than I would consider acceptable. There is lots of screwy construction stuff going on that is messing up our flow. It is worth trying again when I can have more reliable traffic patterns.

Yes, that's the trick to EOC successfully. If you have to brake, then you might've been better off coasting in gear, which would scrub off speed while keeping the alternator turning and avoiding startup enrichment. I try to use EOC only when I can see far enough ahead so I can coast a good distance with little chance of hitting the brakes or needing to accellerate too soon.

I also find it stimulating to drive for good FE. OTOH driving for GREAT FE takes even more skill and attention. Sometimes I just need to relax, sometimes I need to shut off the brain and just live for the moment.

Ya, I can see when it actually be fun to do the EOC, and have been on some drives not too far from here where I could have coasted at least a mile.

I can tolerate a lot of coasting in gear, or pulse and glide, or whatever that would be called. I will keep doing that plenty.

I think my big disappointment was that if I could do EOC I think I could break 30 mpg (still bad, I know), and then they changed a bunch of stuff with construction and now I'm toast...

Scangauge ignorance helps?
 

Please tolerate me while I toot my own horn. I got 59+ mpg on this past month's fill-up, 1050 miles on 17 3/4 gallons. I'm a bit surprised since:
I didn't even check the on-board MPG display during this tank;
I didn't drive for economy;
I dropped the tire pressure from 44 back to 36 psi.
The semi-annual interval between defroster season and A/C season really helps.

Well, as we say down here, it's a sad dog that won't wag his own tail. Translation: Toot your horn all you want. Nice job.

Aerodynamics Rules
 

More and more I am amazed at the positive effect that simple aero mods can have on mileage. Even the simple things that I have done have pushed my steady state mileage almost 25% above highway epa.

Why aren't some of these things offered as an option from the factory?