MILEAGEMAX Build Thread

[Frank Lee]

You didn't provide any cargo data but you have indicated all along you like boattails. Boattails in that configuration (not hanging off the rear as extra length) don't mix well with large interior volume requirements. You see, that is the reason I asked those questions.

If pulling a box trailer, a boat-tailed pickup cap is not going to provide the best aero. If not pulling a box trailer, a boat-tailed cap is what you want. A boat-tailed cap would also work well with a flat-bed trailer with low, heavy loads like a stack of steel I-beams, for example.

But I'm just shooting in the dark here yet because the function remains undefined.

A gaslog is practically a requirement too.

As far as the Rivi ad and aero: advertisements are not a good source for factual information.

[Rick323]

Have you asked Krusty what his average fuel mileage has been since? Going due east (tailwind) and dropping 900' in elevation over 82 miles, it is possible to get a high one time mpg reading. What did he get on the way back?

Personally, if you want better average fuel mileage get 3.08 or 2.73 gears, 6speed manual transmission in addition to the other stuff you want to do.

Just realize you can't just throw a bunch of parts on a vehicle, drive it like you always did and expect to get great fuel mileage. Drive it like there's an egg under the gas petal (that's the common saying in every diesel forum I've ever been on) for better fuel mileage. Good luck.

[gasstingy]

We took a 2004 Silverado 1500 on vacation in April 2007. 5.3L, 4 speed auto, power everything. Unlike Mythbusters, I know that a lowered tailgate helps. We drove more than 2000 miles at the posted speed limits everywhere we went {except 5 mph slower in the rain on the interstates}. Our trip average was barely over 20 mpg, best tank was a bit over 22 mpg. This was years before I knew what ecomodder was.

I think with a diesel and some mods, it's possible to get around 30 mpg, if you're doing it right. What's right just seems to vary a bit by vehicle, but it always includes lowering your speed, slowing your acceleration, and using your brakes less {by timing traffic lights and not tailgating}. Good luck with your efforts.

[JMPVW73]

These are the only transmissions available for the 6.6L engine. The manual is a 5 speed with a granny gear.

ZF S6-650 6-Speed Manual Gear Ratios
5.79:1 Low
3.31:1 First
2.10:1 Second
1.31:1 Third
1.00:1 Fourth
0.72:1 Overdrive

Allison 1000 Automatic Gear Ratios
3.10:1 First
1.81:1 Second
1.41:1 Third
1.00:1 Fourth
0.71:1 Overdrive
0.61:1 2nd Overdrive (2006+ models)

A 6 speed conversion is available for earlier model 1000's. It does not require any other modifications. $1648.00 +$500 core charge.
The cost of a stock 6 speed is compareable but I don't know if any other parts are needed to go that route.
http://www.suncoastconverters.com/gmc/gm_products.html


All 2500HD with 6.6L have an AAM 11.5” axel with 3.73 ring & pinion and Eaton G80 locking differential.

Available ratios
3.42, 3.73, 4.11, 4.56, 4.63, 4.88, 5.13

Ring and pinion sets start at $350
Shim and seal kits start at $80
Master kit w/ bearings start at $200


Stock tire size is 245/75R16 (30.5” dia.)


As previously stated 3.42 gear change will take place in near future and the 6 speed conversion or trans swap is a distant goal.

[JMPVW73]

Frank,
I do not have a specific regular load. The function has no clear definition. The truck is a jack of all trades, master of none. Most often load in bed is not taller than the bed sides. If load is larger top will be removed or possibly incorporate expanding like other top designs found on here.

See Post#4 again for trailer specs. I do not intend to haul a box. I think a boat tail is still possible with a goose neck but may not be best approach.
Typical loads range from a VW Beetle to a truck of the same size. Past loads include my ’66 Imperial Crown (has never seen double digit MPG lol) and Postal Jeeps. Any thing and everything that fits is a potential load.

The Riviera thing is a joke; not an example of efficient design.


Others,
I use good driving techniques when possible.
Krusty has not responded to my inquiry.

[Rick323]

How about a Gear Vendor's overdrive? I don't see one listed for your transmission but that doesn't mean they don't have one-give them a call. Gear Vendors aren't cheap but it might not be a bad alternative to new gears and transmission.

[Big Dave]

You need a baseline.

Set up a run that you can drive repeatably and long enough that filling error is minimized.

Throw some load in it. Have fidelity to the pickup community. A half-dozen 4x8s is the classic pickup mission.

If you don't go at it scientifically, you are just stabbing in the dark.

BTW. Weather warming up here on the frozen steppes and MPG coming up.

[slowmover]

I agree with establishing records. We're all lost without them (as individuals, first and foremost). Truck spec is important, but so is climate & terrain. Fuel burn, truck spec, climate plus terrain all give important contextual information; necessary, IMO, for the best threads. Then comes the actual use of the truck.

Looking forward to it.

And sounds like the Imp needs some TLC. A friends '67 Crown Coupe (42k survivor) used to regularly get 16 at 70 after some prudent tuning and minor mods. There's a build going on right now of a '68 Newport getting a Cummins heart transplant; very good read.

.

[JMPVW73]

Rick, Edited #14


Slow, I didn’t track the mileage. I’m sure it did better, not 16. I nearly bought a 68 Newport 10 years ago. Tell me where to read about it.
The Imperial is a 4 door w/ a 440 and lots of options. They didn’t sell many of those around here. I need a set of hubcaps; mine are wrong (70’s Cadillac).

I bought the Imperial from the family of the original owner 8 years ago. It is a good car but not a survivor by Texas standards. The dash name plate bears the doctors name. His wife drove the car to church and the grocery well into the 1990’s. I live about 20 miles from the estate and have been told a lot of stories about the car.

I love the car. It handles very well for a big 60’s car but the turning radius sucks.
I drove it for two years until 3rd gear started slipping. I drove it in town a bit longer. The top started cracking 2 years ago and I stripped that off. I will do a full restoration but have a few cars in line before it. It is the car people ask about most often after my VW Squareback; lots of word of mouth out about it.

The brakes ran dry when I drove it home, downhill!!! I topped it off the day before but it leaked out overnight. Not the best time to look for where the park brake is. It still has the single circuit.
Shortly after I got a set of tires and before I put them on I had one of the rears separated tread. I got the bumper up to eye level with the factory bumper jack and tire was still on the ground! I chickened out, went home and got a floor jack.
One time I was drinking gas like crazy and stopped to find fuel pump was squirting more on the ground than to the carb. A parts store was near by and I changed it in the parking lot.
I moved it from my house to the garage on a <16’ trailer w/ a 89 Chevy 1500. All the way to the front, head first it had way too much tongue weight and got to swaying bad at 45MPH. We drove the rest of the way at 35MPH on the Interstate. It’s a good thing it was past 1AM.

I like this book and web site.
Amazon.com: Imperial 1964-1968 Photo Archive (9781882256235): P.A. Letourneau: Books
Online Imperial Club (OIC) for Imperial, Chrysler Imperial, and Chrysler New Yorker Brougham Enthusiasts

[JMPVW73]

Many have asked for a towing or load control and studies of mileage with each.

I do not have a regular load for the truck such as a drop in or tow behind camper.
Nor do I have a boat, race car or lawn equipment that will be towed frequently and weigh the same each time.

I will pull less than 10000 pounds with an open dual axel car trailer between 16' and 20’ long across distances of no more than 1000 miles. I may eventually pull an open gooseneck trailer flatbed or incline.
I may eventually work on a nose fairing, wheel skirts and other aerodynamic improvements for the still to be acquired trailer and share those as well.

The car trailer is also not a constant as I currently loan one of several car trailers from friends and make short local trips. Such short trips are negligible in mileage studies.
In the event that I do pull a trailer across a notable distance I will not be repeating the same trip minus the trailer. It is possible that I will be loaded one way and empty another but test route needs to be a loop to be valid.

The only trailer I have full access to is a small 4x8’ mini van axel trailer I pulled with a mini truck. I will not be able to see it behind the 2500HD and it won’t hold very much weight (<1000lbs).
I could also pull a VW Beetle around with a tow bar and even add weight to it but I will also have a hard time seeing it.


I think a bed load would need to be at least 500lbs to work as a control. I could come up with something around 1000lbs to run around with.

As for repeatability I can try to limit driving strictly to commute for the work week and run one week with and another with out load for mixed driving mileage.
I’m toying with making loops down the interstate and back with and without load for Highway mileage. I won’t want to do this much more than 150 miles round trip.

If anyone wants to fund my research feel free to send a check. I’ll drive as far as you like.