My 2000 Jimmy challenge
 

Ok, gonna document what I do here, and hope to get advice/suggestions/ideas from those "in the know".

Vehicle: 2000 GMC Jimmy SUV 4-door. Previous years were called the "S-15 Jimmy", same as Chevy's "S-10 Blazer". 4.3 liter V-6 engine, 4-speed automatic overdrive transmission, 4 wheel drive & about 160,000 miles. Tires are well-worn Uniroyal Liberators from Wal-Mart. Everything is "stock".

Instrument: brand new ScanGauge II just bought.

I was in such a hurry to get started, I didn't even wait for my 2nd fillup and the ScanGauge "calibration". First off was to run a "baseline" to see what it would do at different speeds. I only did one set of passes (one northbound and one southbound) per speed over a course about 4.5 miles long. Cruise control was set going into the first (northbound) leg, then "resumed" after turning around going into the second (southbound) leg. The results follow:

Speed - - MPG - - 2nd
35 - - - 30.65
40 - - - 32.2 - - - 32.4
45 - - - 31.4
50 - - - 29.6 - *30.9 with tires over 50psi - 32.38 with tires 50+ and grille block*
55 - - - 28.35
60 - - - 26.9
65 - - - 25.5
70 - - - 24.85
75 - - - 23.7
80 - - - 22.15

* after second day testing - added for comparison*

When I was done, I did another 2-way average at 40 mph to confirm. It actually went 0.2 mpg higher than the first time.

I then went and read MetroMPG's thread on proper testing, realized that these single sets weren't exactly "statistically relavent", nevertheless, I now think I have a good idea where my best MPG will be found at (40).

Needing to burn some more gas so I could fill up and "calibrate" my new ScanGauge, I decided to try a couple of things. First off, to get a better baseline, I did 3 sets of two-way passes. Also, to make it go a bit faster, and thinking it would show aerodynamic differences better, - and to "fit" in with traffic in the 45, 50, and 55 mph speed limits along this section of road, I chose 50 mph to test at rather than the 40 mph "best mileage speed" my earlier test showed. The results were:

speed - MPG (3 set average)
50 - - - 30.95
50 - - - 30.95
50 - - - 30.8
- - - - - - - - - - 30.90

OK, good, consistant data. Now to check something I've always been curious about - will "folding my mirrors in" improve mileage at all, and if so, how much? So, without turning off the engine or the cruise control, I "folded the mirrors" and did another 3 sets. The results were:

speed - MPG (3 set average)
50 - - - 30.95
50 - - - 31.05
50 - - - 31.05
- - - - - - - - - - - 31.02

Good, consistant data here, too. So - it appears to be worth about 0.1 mpg. Hmmm... But to be a "good boy", and check that the conditions hadn't changed, it was time for the second "B" in the "A-B-A" test.

speed - MPG
50 - - - 30.65

OK, back to "worse" with the mirrors back in "stock" position. Next to test my cardboard grille block. There were also 2 holes in the lower bumper/air dam for the tow hooks, so I covered them, too. I also used a couple pieces of "plexiglass" to continue the contour from in front of the grille across the headlight area to the side of the vehicle. Results:

speed - MPG (3 set avg.)
50 - - - 32.4
50 - - - 32.4
50 - - - 32.35
- - - - - - - - - - 32.38

So - grille block seems to be good for 1.5 mpg. However, it made the engine run hot enough to cause concern (I think) - 225 to 230 degrees. So I guess I need to come up with the smallest size "vent hole" now to keep the engine temp down a bit. Question: what temp is best for MPG?

I should have quit at that point, but decided to try the rear "fender skirts" next:

speed - MPG (2 set avg.)
50 - - - 31.85
50 - - - 31.6
- - - - - - - - - 31.725

Weird - mileage down!?!?! So, better do the final "B" test:

50 - - - 31.8

Hmmm.... But guess what? I'm now down to 1/4 tank. Tomorrow I can go fill it up & do the ScanGauge "calibration"! By the way, the engine and cruise control remained on and "set" the whole time, so each of thse runs were done under "non-human controlled speed".

The best temp is when your vehicle is at normal operating temp. You want it to be as hot as it can be without the fan turning on automatically at a set temp.
For example my car runs 186F with and without the grill blocks, Although now with the grill blocks in stop and go city driving i have seen as much as 200F.

Your themostat doesn't open until 195. Between 180 and 220 is normal operating temps.

The best speed for MPG is approximately 40mph; This is the minimum speed OD can be engaged at, if you were curious. With careful throttle management it's possible to maintain OD down to 35mph.

I am also doing some trialing for an EGR mod allowing greater EGR at cruise. This should provide a small increase in fuel economy at cruise and is easily done.

I have a 99 Blazer 4x4 2 door myself with some ecomods done on it. The dual mirror delete only has very marginal effects. I have an air dam, a battery relocation with a lighter battery, E-Fan, roof rack delete, and AC delete. I see high teen's to low 20's city and not much better on the highway.

The air dam.

http://i1180.photobucket.com/albums/...EA4C58AA53.jpg

Here you can see the mirror and roof rack removal.

http://i1180.photobucket.com/albums/...EA4251CBE0.jpg

I neglected to mention I pumped up the tires between the first "baseline" tests at different speeds and the tests yesterday. I attribute the 1.3 mpg improvement to that. Wow, now that I think about it, that's almost as much improvement as the grille block!! And it's not as though my tires were "low" before (all over 40psi and one of the the fronts almost 50). Before yesteday's tests, I put the fronts at almost 55, and the rears at 50.

When I saw my engine was getting hot (after the first set with the grille block), I used my roll of duct tape as a guide & traced out a 5" hole in the middle of the air dam to let air into the radiator. As I mentioned, I left the engine running the whole time yesterday, and when I put that cardboard up to the grille, it got "sucked" onto it, so I knew it was blocking airflow. Afterwards, the temp stayed around 228 -229, sometimes dropping to 224 F. - and it was "boiling over" and draining onto the ground after I got home & parked. And I needed to put more water in it once the radiator sucked the reservoir dry. So before starting it this morning, I enlarged the vent hole to 6 1/4" and will see how that works.

raylit20;

Thanks for that info confirming my 40 mph "best speed". One thing I noticed was that the RPMs seemed to be the same at 35 as 40. I thought maybe the "lock-up" torque converter just hadn't locked up or something. But not going into OD explains it, too.

Low 20s on the highway is what I would usually see, however the speed limits around here (depending on which road I take), can be up to 75 mph. My first day's test showed 23.7 at that speed, and that's probably about what I'd usually get.

Mine is a 4-door, though. Otherewise, they're probably about the same. I've also got the factory roof rack. Thinking about seeing what difference it makes taking it off, but I'm gonna guess it will be very little - similar to folding the mirrors back. However, I don't use it nearly as much as I use my mirrors! LOL!! Did you see any improvement when you removed yours?

More cool testing, wmjinman. It's fun, eh?

Please consider: Your Garage: [ Add new vehicle ] Also, it would be great if you giys kept fuel logs here too!

Thanks, MetroMPG!!

Yes, I love this sort of thing. Just never seemed to get around to being "serious" (seriously scientific) about it before.

I'm not sure how much I intend to "push it" on the Jimmy's MPG. Just had to have an excuse to play with the new ScanGauge until I got my "Gnat" (1999 Suzuki Swift) back for the SERIOUS mileage attempts. Hence, not sure if I should start an entry into the "garage" and then possibly just let it sit....

Same thing with the fuel log. Once I swap the Jimmy back for the Gnat, I don't see any way I can keep the fuel log with someone else driving it. Is there a fuel log "tool" here? I see some people have what i'm assuming is a "running report" on "best tank", "last 90 days", and "lifetime" MPG averages, so I'm guessing "yes". I would be interested in possibly doing that when I get my Gnat back.

Thanks again for having this site. I'm on it enough to piss-off my fiancee, so that must mean I really like it, huh?

when you enter a vehicle into the garage there is an option under your newly created vehicle data to add into the fuel logs

OK, I did it!!! Filled up ($65 - YIKES!!!) and did my ScanGauge calibration. It said (estimated) I used about a gallon less than I actually did. It also estimated my gas mileage for the tank was about 1 mpg better than it was (due to the estimate being "off", I suspect). Actual was 23.682 mpg and the ScanGauge estimate was 24.7 mpg.

So I entered the information in the "garage" and now am #81 for best pecentage above EPA (EPA=16 combined, 23.682 actual for 48% above). I can see how this can be contagious!! More tests, or just drive around at 40 mph with the grille block & mirrors folded in for a tank!! HAH!!

Oh, with the enlarged "vent hole" in the grille block, the temp didn't go above 188 deg on a 30 mile round trip including a hill. Maybe I should pump up my tires to 60 for this tank - gotta get on the first page of best % over EPA. HAH!! You've created a monster. Bwah-hahahaha!!!!!

So after reading the "roof rack delete" thread, I decided to go out and try my own "A-B-A" tests. This time, instead of Washoe Valley, I went out on US-50 east of Dayton. I had work to do out that direction, anyway. So I found a pretty straight, flat, 4-lane 3.8 mile section of road with easy turn-arounds past each end, and set my cruise control for 50. First, the "A" tests, grille block still on, roof rack on:

speed - E-bound - W-bound - average
50 mph - - - 27.9 - - - 33.6 - - - 30.75
50 mph - - - 28.2 - - - 31.1 - - - 29.65
50 mph - - - 28.2 - - - 33.5 - - - 30.85
overall average - - - 30.417

I noticed the mileage was a couple mpg less than the 50 mph tests in Washoe Valley a few days ago. Two possible reasons; 1) I "calibrated" the ScanGauge between those runs and these. It estimated less fuel use than actual, so I'm guessing the mileage is lower with the new "calibrated" readings. 2) Dayton Valley is probably close to 1000 feet lower in elevation than Washoe Valley, so that should mean the air is thicker = more drag?

There was a fairly stiff breeze blowing out of the east, so I attribute the difference between eastbound and westbound to that. Without turning off the engine or the cruise control, I quickly removed the roof rack & stashed it inside, then headed back out. Four sets this time:

speed - E-bound - W-bound - average
50 mph - - - 28.6 - - - 33.1 - - - 30.85
50 mph - - - 29.1 - - - 32.8 - - - 30.95
50 mph - - - 29.0 - - - 32.5 - - - 30.75
50 mph - - - 28.7 - - - 32.8 - - - 30.75
overall average - - - 30.825

Good deal! Looks like over 4 tenths of a mpg - and I hardly ever use that roof rack. Good riddance - exept, I need to do the final "A" test. Oh, the stiff east breeze was still blowing. OK, one last "A" test with the rack back on:

speed - E-bound - W-bound - average
50 mph - - - 28.7 - - - 31.7 - - - 30.2

When added to the first set of "A" averages, we get an updated 30.3625 mpg with the roof rack on. That makes it a 0.46 mpg improvement. I like it!!

One final observation; with the newly enlarged 6.25" diameter "vent hole" in the cardboard grille block, the engine temp. stayed around 193 deg.

See this:
GMC Typhoon - Wikipedia, the free encyclopedia

Interesting.

Thanks for posting another test.

OK, I'm getting addicted!! After re-reading some of the other posts, I'm seeing the wisdom of accumulating "small" improvements in addition to looking for the "low hanging fruit". So with folding the mirrors back yielding between 0.1 and 0.2 mpg on my initial test, then thinking about the roof rack delete yielding 0.4 to 0.46, I can't help but thinking the combined will be over 1/2 mpg. So I read-up on "mirror deletes" in the aerodynamics threads last night, and am now going to go see what I can find for inside mounted convex mirrors!!

Also starting to think about a partial belly pan from the bottom edge of the factory bumper/air dam to the front of the skid plate (which looks somewhat aerodynamic to me already).

Gotta get it up higher than 81st place for % over EPA in the "fleet". :-)

Re: the small improvements adding up, you've probably read around here: there's no magic bullet, but there is magic buckshot.

And... not to go too far off topic - when's your Suzuki going to be back in action?

Gotta finish using the Jimmy for hauling & towing, then trade back for the Gnat. Depends on how well I "get on the ball".

Speaking of hauling & towing, I finished one of those tasks today - delivered a 2000 lbs. car trailer (empty, thankfully) about 20 miles to my folks' place & was really worried it would hurt my tank's average. But surprisingly, I didn't do too bad - mileage still up around 25. Of course, I still had the grille block in place, the roof rack off, the tires aired up, and went ahead & folded the mirrors back. - and drove 40!

Earlier, I had to make a run to Reno (about 30 miles one-way), and started out driving 40. - Probably not the best idea on the freeway... I got honked at about 3 times, and could see in the mirror (sort-of with the outside ones folded back) that I was definitely impeding traffic. So I ended up speeding up a little at a time, and eventually settled on about 55 mph.

So now I'm trying to decide if future trips to Reno should be on the "old highway" where I could probably get away with going really slow (and impede traffic less), of just "bite the bullet" and take the freeway & go faster. The benefits of the freeway are more gradual hills and no stoplights. Drawbacks are probably more cops (who might suspect me of drunk driving at that speed) & more likelyihood of causing an accident if I insist on going slow.

So I had to deliver another trailer today, and was bummed that it would probably lower my mpg for the current tank. Sure enough, by the time I got it un-hitched, I had only tipped over 23 mpg momentarily per the ScanGauge, but then dropped back below it. Tried all the "tricks" I knew to "hypermile" back home, but had to go into a headwind, and ended up losing a little bit of my "tank average" by the time I was parked again.

But in trying to maximize mpg, I wanted to keep my mirrors "folded in". Trouble is, this particular trailer completely blocks the view through my inside rearview mirror. Thus, I was motivated to check the local auto parts place & see what I could do for convex mirrors I could put INSIDE, but still get a view back. Ended up buying an "el-cheapo" version for $2.99 and putting it on the passenger's side. But the folded-in stock mirror blocked part of the view, leaving me with just a "sliver" of visibility to the back & side.

Think I'll spring for another $2.99 and install a second one on the driver's side, though. Being closer to my eyes, I think I should get a somewhat wider field of view from that one. I noticed that when coming up behind someone going even slower than I am (not exactly sure how that's possible), that the standard glancing at my mirror and simultaneously moving into the next lane to go around doesn't work so well when the mirror's folded-in and I've got no field of view!! Then I'm forced to "convert gasoline into brake pad dust", as someone else so aptly posted on here somewhere.

interested to know if your jimmy has the built in mpg guage if so how accurate it is?

No, it's not a "built-in" mileage gauge. See my paragraph 1 above. I have an aftermarket "ScanGauge II" that I plugged into the car's computer diagnostics port under the dash & sit on (in) the instrument cluster between the steering wheel & the car's other gauges (speedo, tach, etc.)

As far as it's accuracy, when I filled up the first time after plugging it in, it was about 1 mpg "optimistic". BUT, it also "guessed" that I used about 1 gallon less on that tank than I actually did. So I went through the "calibration feature" on it at that fill-up, and we will soon see how accurate it is this tank, after "calibration". I expect it to be pretty good.

What I do is use the ScanGauge readings for "instantaneous" feedback on what current conditions are doing or using it's "trip feature" to see what my current "mod" is doing. But to get the "true" mileage for the tank, I still do it the old fashion way - - divide miles traveled by gallons used with a calculator.

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.

That was funny - thanks for the chuckle!

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!)

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?

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.

>
> 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. ;-)

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?

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 :confused:

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

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

I figured that out back when I was doing my Bonneville Salt Flats landspeed racecar. I had another car of the same model & year (almost - 2 years newer, but with the same basic body style, at least) that I'd go out and test different air dams & stuff. It was too old to hook a ScanGauge up to, so I'd do coast-down testing.

But knowing the mods would have greater effect, and the results would be easier to see at higher speeds, rather than doing it on the freeway where the speed limit is 75 and lots of traffic and cops, I'd go way out - probably 80 miles from where I live - to a particular stretch of fairly flat road way off the beaten track with extremely light traffic & still a 70 mph speed limit. Of course, I was trying to exceed 200 mph in the "real car" too, so I wanted the tests to be a little closer to the speeds I'd actually be dealing with.

So I set up a 1-mile test section for my two-way tests & marked the ends with orange traffic cones. Then I'd go out more than a mile past the end, turn around & punch it up to 112-115 mph, then throw it into neutral, trying to guage it so I'd be down to going 110 at the "start" cone (or near it). When it hit 110, I'd start my stopwatch & then let it coast down to 60 & write down the time. Then I'd go a mile past that end, turn around, & repeat. And I'd try to do 3 sets of those.

To try to reduce the other variables, I had the tires pumped up to 70 psi, and would pour a couple gallons of gas in the tank after each set to try to keep the weight the same. Wind will slow down a lighter car faster than a heavier one, all things being equal, right? Of course, that big 455 Buick probably burned even more gas than that. I didn't do the easy to gauge "fill it all the way up" trick, because, trying to maximize the aerodynamic effect, I tried to run it as lightweight as possible, so with the tank less than half full. But with a couple of exceptions (which I think were probably due to intermittent wind gusts), I was pretty pleased with the consisancy of the data, and I was definitely able to tell which air dam (if any) cut drag the most.

Like I said earlier, I just love doing this type of testing. :-)

Attempting to post image...

> Attempting to post image...

Looks like it worked. Neat old Riviera! What's the story?

Wow - you asked for it!!! I could write a book about me & Buick Rivieras.

Part of the story is in the post before the picture - #31. Here's some more:

It started in '65 when I was a kid & my dad got a '64 Rivi "almost new" (repossessed from the bank & auctioned off). I loved that car & then when I got my driver's license, was the car I was allowed to drive. Of course, I promplty learned 2 things; first, that it was almost impossible to hit 15 mpg with it on the highway (I went to college in Reno, 92 miles from my hometown, so had many "highway driving" opportunities). And second, it's top speed was 130 mph+. YES!!!!!

Meanwhile, in '72, when pulling into a parking lot, I saw this WILD car that I thought was the most beautiful thing I'd ever seen. Low, long & sleek. A huge hood that musta had a HUGE engine under it, and a super-futuristic "pointed rear window" with a set of louvers on each side. Gawd, I'd never seen anything like that before!! (I was, at that time, unfamiliar with the boattail Covettes they had in the mid 60's). Well, I just had to go "check out" this gorgeous piece of art disguised as a car, and as I approached, imagine my shock and amazement as I started to recognize the "Riviera" logos and "styalized 'R's" on the thing!!! Holy crap - this is a Buick Riviera - a make and model I was already convinced was amongst the best cars on the road!!

Back to college & driving my dad's car. I guess he didn't like my "rebellious teenager act" and for punishment, removed my driving rights to the '64 Riv. OK, screw it - I'll get the car I really want anyway - the '71 Riv. Eventually I did, and that was in 1976 (or maybe '77). I've had that car ever since, driving it off & on as my "cruiser".

As the new century (2000) was rolling in, I was hearing things about racing. My sister married a guy who does drag racing (which never appealed to me - I liked to be able to "enjoy the speed" for awhile, not just take off as fast as you can & then slam on the brakes & stop - what fun is that?). And I'd read about the Bonneville speed record events once in awhile in magazines, too. One time at work, they had us in Wendover, which is only a dozen miles from the Salt Falts, so I went and checked it out. Wow! My reaction was much like Burt Monroe's in the movie "The World's Fastest Indian" when he first saw it. Also, a guy who's office was across the hall from mine at work was a drag racing guy AND and engine builder & we'd talk about stuff. I always wanted my '71 to go faster than it did. - guess 130 just wasn't enough for me! ;)

Eventually, we decided to take my car out to Bonneville and run it for the "130 mph club", an event they had set up for licensed, street-legal cars to let "common folk" get a "taste of the salt". To get into the club, you had to make it to 130mph or more in one mile from a standing start - twice. And you had 5 tries. I knew my car could do 130, but I learned that it took more than a mile!!! So the challenge was on!! We started stripping weight, got headers, roller rockers, new manifold, several things like that. Then when I went up there, I ended up going 128.2 on my first run. On the second run, I blew the engine to smithereens (this was the second engine I'd blown in this car - the first, many years before).

When I got back home, which is a whole story in itself, since I DROVE up there ALONE in THAT car, we started talking. I wanted a new engine, built with some extra poop so I could go, maybe 150. Bob (my engine-building buddy) had other ideas. he said "screw the 130 club - let's built a REAL race car and go for an actual land speed record". And I wasn't too hard to persuade.

3 years and about $100,000 later, I'd blown 2 more Buick 455 engines, except this time, they were high-end race engines, and got up to an official 182.2 mph. - but NOT a record. Although, some of the guys in the Buick Riviera forums think I might well have the "World's Fastest Boattail Riviera".

But after the first RACE engine went away at 160 mph, we again needed a new engine. I happened to see the "green turd" (named after Robin Williams' rental motor home in the movie "RV") sitting in a vacant lot for sale. It was a '73 Riviera (the one year of the "boattail" models I liked the LEAST) & I thought, "Hey, that thing's got a 455 in it!!" So I bought it for $750 & drove it home. Now, from all outward appearances, it was a real P.O.S. It used to have a vinyl roof that was about 80% gone. Not 100% gone, mind you - that extra 20% of rags gave it a real "special" look! HAH!! Rust spots all over it, faded paint, missing door handle on the passenger's side, and it sounded horrible. The interior was all ripped up, the headliner was hanging down, holes in the carpet under your feet - full of dirt - you get the idea.

So I took it home and - bought ANOTHER engine for my '71, the race car - and so the "Green Turd" just sat there - for maybe a year. In the meantime, I was also wanting to try the "Silver State Challenge". This is a rally where they close off a 90 mile stretch of fairly straight highway in eastern Nevada and let sports cars scream through there (for a hefty price - entry fees cost you about $1000 by the time you're done). I think the record is 208mph average for that 90 miles. I was actually thinking of using the '71 for both Bonneville Salt Flats AND the Silver State Challenge. But, it was sitting there waiting for it's next high-dollar race engine and getting suspension & roll cage upgrades, and Bob said, "Well, how well does the 'Turd run?" Well, I didn't know... I drove it home that day I bought it, coughing and sputtering all the way, and never started it again.

So we checked compression and oil pressure & it actually looked good. I thought I remembered the guy I bought it from saying the engine had been rebuilt "30,000 miles ago", so if that was true, we might be in business. I put a new carburetor, distributor, coil, wires, & plugs on it, changed the oil, and it ran much better. Took it into a muffler shop & got the exhaust system fixed, and I'll be damned, it purred like a kitten!!! So I've maybe got the makings for the "ultimate sleeper" - a car that looks like ****, but runs like nobody's business.

We eventually took it to the "Silver State Challenge" and ran it in the 105 mph class (as "rookies", we had to enter a lower speed class the first time). But it performed like a champ - 90 miles down at 105, and then 90 miles back at 65-70 all on one tank. Adding in all the extra running around driving we did, by making it all on that single fill in the 20 gallon fuel cell, we had to have gotten at least 13.5 mpg. I was pretty impressed getting that kind of mpg with nearly half the trip at 105 mph & another several miles of it "city driving" - usually those big Rivieras don't get much better than that any time!!!

But the other half of the "Green Turd's" life - under my ownership - is as an aerodynamic research car for the salt flats project. After reading an article about sports car aerodynamics in "Hot Rod" magazine, I built a "snowplow" air dam for the salt flats car. This became a bit controversial with many people telling me it would ADD drag & slow me down. So off I went with the Green Turd to my testing area 80 miles away. First set of runs was with NO air dam - just the car's stock front end. Second set was with the little air dam I made for the Turd for "Silver State", the one in the picture. An improvement - GOOD!! Then came the "snowplow" air dam off the '71 Riv - the salt flats car. Guess what? That one WAS the best of the three configurations. I do have yet another air dam I'm making for the '71 that I think might be better yet, and when I get it done and recover a little bit from the financial devastation I've been in ever since the collapse of the economy, I'll go test that one head-to-head with the original "snowplow" air dam.....on the Green Turd, of course.

Oh, and one final post-script to the story; the 'Turd now has a Gear Vendors overdrive mounted behind the transmission, a new cam & new, ported heads, an improved oiling system (a famous weakness of those Buick 455s when you try to race them), a GPS speedometer, adjustable, lowered suspension, and about 130 horsepower more than it did when I first started playing around with it. It's nice having a sponsoring machine shop with both engine & chassis dynamometers available!!! ( I just hope they can stay in business through this "recession", too)

These two thumbnails show the "Green Turd" from the outside and then the engine compartment. As you can see, there's a bit of a difference. While the exterior was left "ratty", the mechanical parts were given quality treatment. "Work done" includes:

> Ported & flowed aluminum Edelbrock Buick "stage-1" heads
> Custom ground Erson cam designed around the "flow numbers" from these heads
> roller rockers - 1.67 lift ratio
> aluminum Edelbrock intake manifold - "port matched" to the heads
> rebuilt and recalibrated Quadrajet 820 CFM carburetor
> 1" phenolic spacer between carburetor & intake manifold
> TA Performance chrome headers, "X" crossover pipe, 2.5" dual exhaust
> Mallory "Unilite" electric ignition; distributor, coil, wires, "Hyfire-6" control module
> TA Performance timing cover/performance oil pump with adjustable regulator
> AM&P external oil filter and balance tube (feeding oil to the rear as well as the (stock) front of the main oil gallery)
> "Accu-Sump" oil accumulator (holds 3 quarts of oil in reserve under pressure & releases it to the main oil system if pressure drops)
> 20 gallon aluminum fuel cell with Mallory electric "pusher" fuel pump & regulator with return line
> battery relocated to the back - trunk area
> 17" aluminum wheels with Yokahama 55 series, "Z"-rated tires
> Home built fiberglass air dam, proven in coast-down testing to reduce drag in the 60 to 110 MPH speed range.
> "Moon-Eyes" aluminum "salt discs" on all 4 wheels
> Suspension lowered for 2" height reduction, new shocks
> All new steering & suspension neoprene bushings
> mechanical oil pressure & temp gauges, aftermarket tachometer and "Livorsi" marine GPS speedometer
> "Gear Vendors" overdrive on back of transmission (105 MPH = 1800 RPM)

A couple more views of the "Green Turd". Not too good for gas mileage, but really fun to drive otherwise.;)

The one with Bob & me was after our successful "Silver State Challenge" run, where we placed 6th in the "105 MPH class". In these classes, the goal is to come as close as possible to the target speed (105 MPH in this case). Due to a miscalculation by your truly, we missed it by almost 2 seconds (slow), putting us behind 5 others who came closer.

We were a little behind & Bob told me I'd better speed up & pick up some time in the last mile or so. I had it accelerating pretty good and saw the finish line coming up as he started counting down the seconds to our target time. For some reason, a few seconds before we crossed the line, I thought we were going to be too quick, so I took my foot off the gas. Well, that turned out to be not such a good decision. Oh well, for our first time ever trying that, I don't feel too bad. :-)

Since this is the 2000 Jimmy thread, maybe a picture of the Jimmy would help, eh? :rolleyes:

For some reason, I can't get any confirmed MPG improvement out of those rear fender skirts. I don't get it....how can they NOT improve it? But after a couple different tests, I'm getting nothing. :confused:

How fast are you driving?

The first couple times I tested it, I was doing 50. First time showed a net loss of a fraction of a MPG. Second time showed a net gain of a fraction (and I mean a SMALL fraction - like 0.0-something.... in the hundredths of a MPG. Then I tried doing it at all speeds to see if it started showing an improvement at higher speeds. Nope.

- Well, maybe... at 40 and 45, the numbers were a little less, but at 50 they were the same. At 55, it was a little less, but then at 60 through 80, they virtually matched the tests without them. But it was a different day, different "calibration" on the ScanGauge (more recent fill-up), etc. I was looking for a trend, but didn't really see any.... except for maybe the fact it was worse at 40 and 45 (where the change shouldn't be as evident) shows that the whole new "calibration" moved my mileage lower, so if adjusted for that, maybe the fender skirts DO improve it at 60 and above. (in other words, without them, maybe the whole second test would have been lower MPG instead of just the 40 & 45 MPH part)???

I guess this is another example of the importance of doing MetroMPG's standard of "A-B-A" testing for this stuff .... same day, same session, then return to "A" for a "check".

Me and my engineer talked about aerodynamic features changing how they act at different speeds in great depth, but never considered anything these low speeds and it was usually boundry layer stuff not whole structures.

This is kind of important to me since I would like to make real metal side skirts for the suburban that are removeable once I cut out and replace the bondo and fiber glass around the rear wheel wells.
I was planning on installing them for road trips since most of my usual driving was at or below 55mph.