4.3 economy

[Owly]

I just purchased a 2000 Safari 4.3 AWD Utility with a "knock in the engine" and 136k miles. I heard the knock and couldn't get my wallet out fast enough......... clearly a broken flywheel. I own a '97 2wd Chevy C 1500 with the same engine, and routinely make from 20-22 mpg highway with it. What I want to know is weather there's a snowball's chance in Guam of hitting these numbers with the Safari. I plan to do drop the drivetrain out...... an intimidating prospect, but I DO have the equipment to do it. While it's out I will build a selectable hot / cold air intake using exhaust heat, and I may install a water injection system to see if moisture in the air will enhance mileage. The theory of the heated intake is that on the highway you use almost no HP for cruise. This results in effectively lowered working compression ratio and reduced efficiency. By heating intake air, I can run with a wider throttle setting, and will have higher temps and pressures in the cylinder at TDC. I already know that my mileage is much better on hot days than cooler days. It also appears that moisture in the air helps.

In addition, I will be changing the oil in the transfer case which seems to have clutch drag......... enough that it is difficult to turn the front drive shaft with the rear wheels on the ground and the front elevated..... this is just wrong with the clutch type AWD which should be in the 2000 model year unless they used the viscous coupler transfer in the utility version........... Anybody know?? I'll go with the Royal Purple synthetic. I'll also knock the transfer down and put a case saver inside it, and in general make sure the clutch pack and stuff is OK.

Both axles will get light synthetic gear oil while I'm at it, and I'll pull all for brake rotors off and have them turned with a very slight wobble....... parallel faces of course, but perhaps .010 wobble to knock the brake pads back..... an old stock car racer's trick to reduce heating of the rotors. Heat = horsepower.

It will of course get a scangauge so I can monitor everything.

I don't know what else you can do for economy............ perhaps vortex generators fender skirts, air dams, etc...........but I'm a bit dubious about the advantages of these. Suggestions??

Howard

[Stroverlander]

How much time and money are you going to spend to maybe/possibly find a negligible gain? I just don't see the payoff.

These vans are bricks aerodynamically, you're not going to see 20+ mpg in an AWD Astro/Safari van.

I don't see that reducing a bit of drag in t-case is going to do much when all the parts attached to it are still rotating 100% of the time. All the later model electronic t-cases are the same NP or NV 136.

If I was going for ultimate fuel economy in an Astro, I'd make sure my van's mechanicals were all in tip-top condition, remove the roof rack (crossbars at minimum), run the most fuel efficient tire possible at or close to max inflation and then finish detail with a good sealant and call it day.

[photo_van]

You might see 20 mpg in a light cargo van on a flat freeway with a tailwind. Before I lifted and went with bigger tires I got 20 a couple of times in my passenger van. Now with a strong tail wind I can eek out 19 once in a great while. On a 6 week road trip this summer (mostly mountain roads), driving for efficiency, I averaged ~17mpg.

[mdmead]

My '96 AWD hi-top conversion (w/3.42 gears) used to pull down 20 mpg easily. It seems though, the newer the van, the harder time they have achieving this number. Not sure why that would be though. I think 20 is certainly attainable, and using synthetics is a step in the right direction. As mentioned, low rolling resistant tires pumped close to max inflation would help too. Best thing though is going to be a light, smart foot on the gas.

[Owly]

My '96 AWD hi-top conversion (w/3.42 gears) used to pull down 20 mpg easily. It seems though, the newer the van, the harder time they have achieving this number. Not sure why that would be though. I think 20 is certainly attainable, and using synthetics is a step in the right direction. As mentioned, low rolling resistant tires pumped close to max inflation would help too. Best thing though is going to be a light, smart foot on the gas.

The nut behind the wheel often is the deciding factor on mileage. I get well over 20 mpg on my 1997 C1500 extended cab 2 wd pickup with many hundreds of pounds of tools in it, but I don't have a lead foot, and I use a scan gauge. Most people with the same pickup seem to be making around 17-18, while I make 21-22 (hwy). This is a completely stock 4.3 Vortec engine. The ONLY mod is a lock up switch on the torque converter. I drove to Helena (Mt), and hooked the Safari AWD to a tow bar (pulled both drive shafts), and came home (150 miles each way), climbing over one mountain pass, and averaged 17.2 MPG for the trip. The 4.3 is a very impressive engine! This is the reason I opted for a Safari.

I actually prefer the AWD Aerostar except for the shitty tranny, and the engine that has head problems. They drive far better (like they are on rails), have more leg room, are easier to work on, and make better mileage. Those two are the only mini vans I would even consider, as both are built from pickup parts.

Getting max mileage is a personal challenge for me. I drive a LOT of miles. I need something that will go off road well, as I go into some extremely remote places, hence the AWD astro. I have to have some kind of four wheel drive. I currently drive a Subaru Legacy, which is kind of minimal for camping, but it will go almost anywhere. The narrow track is an asset.

Mileage mods:

Hot air intake selector
water injection
synthetic oils
disk brake mods
AWD lockout switch
Scan Gauge

Aerodynamic mods??

Semis use a side air dam under the trailers these days......... It obviously pays or they wouldn't do it
front and side air dams, fender skirts, flat disk wheel covers, vortex generators behind the windshield and at the rear of the van, grill blocker....... None of these things would likely have a dramatic effect, but taken together might gain a couple miles per gallon.

I intend to make gas mileage a "project" with this vehicle......... something I've been wanting to do for some time.

Howard

[Stroverlander]

My '97 AWD half passenger / half cargo - only one rear bench seat (special order company vehicle) with 3.42 gears did get slightly better fuel mileage than my fully optioned '04 AWD. So the lighter weight, gearing and passenger tires do make a difference but not enough in this instance for me to not drive what I want.

Owly, I like your TCC lockup switch mod.

It will be interesting to see your results and if any economically feasible gains can be achieved.

How many miles a year are you talking about?

[Owly]

My '97 AWD half passenger / half cargo - only one rear bench seat (special order company vehicle) with 3.42 gears did get slightly better fuel mileage than my fully optioned '04 AWD. So the lighter weight, gearing and passenger tires do make a difference but not enough in this instance for me to not drive what I want.

Owly, I like your TCC lockup switch mod.

It will be interesting to see your results and if any economically feasible gains can be achieved.

How many miles a year are you talking about?

Depending on how much I like the van, and what I use it for, it could easily amount to 20K a year

The TCC mod is an extremely valuable one for me. It has allowed me to pull very heavy loads without generating heat in the transmission. I use it in ordinary driving when pulling hills also. I flip the switch, and grab 3rd rather than letting the transmission unlock the TCC and run in 4th. It's far more efficient and runs cooler. Overdrive is a generally bad idea.... It reduces engine speed at the expense of running through gears instead of straight through power as in direct (3rd in a 4L60E). Add the torque converter losses running in 4th free, and that "shift" does little more than make more noise and burn up more fuel. It's only about a 20% split from 3rd to 4th, so trying to split that with the torque converter being used as if it were a gear is beyond absurd!! The unfortunate thing about these transmissions is that I can't simply program them to do what I want. If I had my "druthers", the transmission would always have the TCC in lock except in first gear, and momentarily during shifts, and there would be no pulse width modulated hydraulic pressure..... (an idiotic feature). I want a tranny that holds up.......not one that is "nice".

What kind of mileage are you getting on the highway?

Howard

[blitzin247]

Any updates on progress?