My 2000 Jimmy challenge

[MetroMPG]

Originally Posted by Slow_s10

I really hope to pull off the ultimate mod on this truck early next year, which would be to just go ahead and jack up the radiator cap and roll a more efficent car under it.

That was funny - thanks for the chuckle!

[wmjinman]

Originally Posted by Slow_s10

Some s-series trucks/SUVs had a build in mileage gauge. I think what Roy was asking you was do you have the factory gauge also and if you do how accurate is it compared to the Scanguage.

For what it's worth I have an Oldsmobile Bravada that I have been trying to squeeze better mileage out of. It's basically the same as a Blazer or Jimmy but with AWD instead of 2wd or 4wd. I have done some little stuff and I have managed to get it from an average of around 14.5 up to over 19 but I am trying to keep the mods on the more mild side for now. Although I really hope to pull off the ultimate mod on this truck early next year, which would be to just go ahead and jack up the radiator cap and roll a more efficent car under it.

Oh, sorry Roy. No, my 2000 Jimmy does NOT have the built-in factory mpg readout. (at least, it's not working - some of my electronics are - weird. I think there should be a display somehwere on the dash - under the speedo, maybe? - that tells what gear I'm in, too. If so, it hasn't worked since I've owned the car. I look down at the console to see what the shifter is next to!! No "cruise" light comes on anywhere when I engage cruise control either, and I highly suspect there should be - - - at least every other car I've ever driven with cruise control has one!)

[Neen]

I'm not saying that 23 mpg average is impossible in a blazer/jimmy 4 door but DAMN!!!! That is almost too good. Wen I owned my 99 4 door blazer with 4.3 4wdand 3.42 gear ratio I think my best tank was maybe 20 all mountain highway. What gear ratio are you rocking and are you doing any neutral costing or PNG?

[royanddoreen]

Originally Posted by Slow_s10

Some s-series trucks/SUVs had a build in mileage gauge. I think what Roy was asking you was do you have the factory gauge also and if you do how accurate is it compared to the Scanguage.

For what it's worth I have an Oldsmobile Bravada that I have been trying to squeeze better mileage out of. It's basically the same as a Blazer or Jimmy but with AWD instead of 2wd or 4wd. I have done some little stuff and I have managed to get it from an average of around 14.5 up to over 19 but I am trying to keep the mods on the more mild side for now. Although I really hope to pull off the ultimate mod on this truck early next year, which would be to just go ahead and jack up the radiator cap and roll a more efficent car under it.

Exactly what i was thinking about that cap!!I'm just using the blazer in our business,since it's "Like a rock" I will just keep feeding it at $1.30 per litre. mpg is 14-18 bit awlful if you ask me.

[wmjinman]

Originally Posted by Neen

I'm not saying that 23 mpg average is impossible in a blazer/jimmy 4 door but DAMN!!!! That is almost too good. Wen I owned my 99 4 door blazer with 4.3 4wdand 3.42 gear ratio I think my best tank was maybe 20 all mountain highway. What gear ratio are you rocking and are you doing any neutral costing or PNG?

>
> edit: In case you're referring to the 23.68 mpg average below my name over on the left side, that was my first tank with the ScanGauge where I spent a great portion of the tank testing hypermiling techniques & mods out on the highway & very little "city driving" by comparison. Although, there were lots of stopping & turning around during those tests - and engine idling sitting still while I was installing the grille block with duct tape etc. For the life of my ownership of the vehicle though, I'm sure it's less - probably somewhere in the mid "teens" if I were to guess...
>
>

Well, that 23 mpg was a "trip average" per the ScanGauge on what was about a 20 mile trip WITH THE WIND, and with a net elevation LOSS (while towing the trailer). And I was cruising at 40 mpg (my best mpg speed). On the way back, I tried to "hypermile" even more, but into the wind and uphill, it didn't work - still ended up with 23 - - maybe even 22 or 21-something for the trip.

To answer your question(s), I don't know what the rear-end ratio is - I bought it "used". And I do "hypermile" when I can. Never learned the "pulse & glide" technique on level ground, so just engage cruise control at 40 or 41 if possible. On this particular trip, there is a small hill, and it's steep enough that I will throw it into "neutral" and end up going 70+ by the bottom while the engine's idling. It's fun watching the ScanGauge trip average steadily climb as I'm doing that!! I don't "engine-off-coast" in this thing too much, because being an automatic, and having an electronic speedometer, it screws with the odometer and the cruise, etc. In addition, I think turning the ignition switch on & off probably flashes the headlights, making people wonder what I'm doing, etc, etc,. I guess I should wire up one of those fuel injector kill switches like they talk about on here....

But around town, driving "normally" (as in, what other people would consider "normal"), I'm sure this thing would never get out of the low teens. I try to anticipate stops, let off the gas way ahead of them, etc. And I NEVER "floorboard it" (except when I have to going up the Sierras). It pisses people off how slow I start out, but that's just tough. They'll fly around be, exhaust gas shooting out like a jet's afterburner, and I'll watch them get wayyy ahead of me. Then brake lights for the next signal, and eventually I pull up alongside coasting in neutral. Sometimes I don't even have to stop because the light has changed and traffic is moving again by the time I get there....

On highway trips though, 22 to 23 mpg is normal for this thing if I drive near the speed limit (55 to 65 depending on the road - sometimes 75 on the freeway). And it's got a 4-wheel drive selector that lets me drive around in 2-wheel drive almost always. I've even considered un-hooking the front axles, but with winter approaching and needing to use 4-wheel drive on occasion, guess I'd better not. ;-)

[wmjinman]

Decided to go do some more "A-B-A" testing of fender skirts today. Headed up to my 4.4 mile course in Washoe Valley - elevation 5200 ft. and a bit of a west wind blowing (mostly a cross-wind to my course). Speed - 50 mph, cruise control regulated. ScanGauge "trip" reset at beginning of each section - northbound, then an "equal and opposite" southbound:

"A" tests... grille block, mirrors folded back, roof rack off, 60psi in the tires...
speed - n.bound - s.bound - avg.mpg
50 - - - 29.3 - - - 30.1 - - - 29.7
50 - - - 29.2 - - - 30.1 - - - 29.65
50 - - - 29.2 - - - 30.0 - - - 29.6
overall "A" avg. = 29.65

"B" tests... same as "A" tests, but with cardboard "fender-skirts" taped over back wheel openings...
speed - n.bound - s.bound - avg.mpg
50 - - - 29.0 - - - 30.0 - - - 29.5
50 - - - 29.2 - - - 30.2 - - - 29.7
50 - - - 29.5 - - - 30.3 - - - 29.9
overall "B" avg. = 29.7

"A" verification tests. Same as others with cardboard fenderskirts removed
speed - n.bound - s.bound - avg.mpg
50 - - - 29.4 - - - 30.2 - - - 29.8
50 - - - 29.4 - - - 29.7 - - - 29.55
2nd "A" avg. = 29.675

If I average all 5 "A" runs, I get 29.66mpg for a 0.04mpg improvement from the fender skirts. Wow - that's almost negligible. In fact, I tried a less rigorous test a couple weeks ago, and it showed the fender skirts actually DECREASING my mpg!!!!

So - - - how is this possible? Has anyone else done fender skirt tests that showed almost no, no, or even negative gains?

Confused & baffled?

[MetroMPG]

Originally Posted by wmjinman

Has anyone else done fender skirt tests that showed almost no, no, or even negative gains?

Yep.

See post #6 in this thread:

http://ecomodder.com/forum/showthrea...-camry-84.html

Nothing popped its head above the noise in testing skirts on a 2007 Camry Hybrid. Though I also admit to possibly poor testing (guessing that the car may not have been fully warmed up since the 2nd set of "A" runs was higher than the first set of "A" runs).

[wmjinman]

Originally Posted by MetroMPG

Yep.

See post #6 in this thread:

http://ecomodder.com/forum/showthrea...-camry-84.html

Nothing popped its head above the noise in testing skirts on a 2007 Camry Hybrid. Though I also admit to possibly poor testing (guessing that the car may not have been fully warmed up since the 2nd set of "A" runs was higher than the first set of "A" runs).

>
>
Thanks, MetroMPG. I read your whole thread and then looked back at my results. And although the second set of my "A" tests were *slightly* better mpg than the first (0.025), and maybe showing that "car warming up effect", I kinda doubt that can be taken too seriously (in my case), as I'm sure it's well within the margin of error.

But speaking of poor testing methods, my northbound run ends at the base of a slight hill where the mileage starts to drop and can drop 3 or 4 tenths of a mpg by the top. I try to catch it at a specific spot each time, and before "the change starts". But on my first set of "B" tests with the skirts, as I got to the end of my test section, I was distracted (the cell phone rang & I answered it, I think). Then it was "Crap - what's the trip average?!?!?" I caught it at 28.9 and dropping to 28.8, but I was also already past my end point and climbing the hill. So I wrote down 29.0, just guessing. All the "A" tests were 29.2 and 29.3, and the next 2 "B" tests were 29.2 and 29.5 for that nortbound run.

So, bottom line, maybe I should throw out the results of that first set. If I do that, the average of the remaining 2 sets is 29.8. Of course, that's a "small" data set of only 2 sets, too. - - and it only increases the "B" average one tenth of a mpg. Sooo...... (but it would move the improvement from 0.04mpg up to 0.14mpg, which is a huge difference there, I guess)

Another thing I noticed in your thread is it looks like you cut the cardboard & fit it INSIDE the wheelwell, making a more-or-less "flush" fit to the outside? In my case, I cut them a little oversized & just slabbed them onto the outer body surface with duct tape. That adds the thickness of the cardboard to the frontal area and also adds a rough "ridge" around the outline for the air to hit. So maybe those things tend to offset the gains from covering the openings? Gee, I sure wouldn't think so, but??????

I also read with interest the part about testing at higher speeds because the aerodynamic effect will be magnified. And I suppose the arguement could be made that unless I intend to drive around at 40 & 50 mph all the time permanently, a more "highway speed" test would even be more realistic for "real world" driving.

Bill

[oil pan 4]

The slower the drive the less I would worry about aero mods.

[MetroMPG]

Originally Posted by wmjinman

I also read with interest the part about testing at higher speeds because the aerodynamic effect will be magnified. And I suppose the arguement could be made that unless I intend to drive around at 40 & 50 mph all the time permanently, a more "highway speed" test would even be more realistic for "real world" driving.

I definitely agree with that. Higher speed testing is better, particularly when you're dealing with mods that may have a relatively small impact.