Some deep thinking on getting Best MPG in a VAN

[ennored]

"That is my plan, pair it with my older OBDI PCM sharing most sensors."

Won't work. Has to be an engine processor at least used with an 8L90. Needs to speak in the right "language" across the CAN bus. It's not a simple matter of hooking up a few sensors.

"I note you say "The Chevrolet Performance crate 8 speed transmissions" so is there a non performance version??"

Chevrolet Performance being the only ones selling a "crate" 8L90 package. A service trans from the dealer won't have a harness or controller.

"Can you share more information on these Transmissions??"

Like what? They've been out a few years. Lots of info online about them.

This has some good info:
8 speed crate trans controller Instruction Sheet.

And you do realize the trans, a control kit, and an installation kit will run you about $7500, right? That's A LOT of gas. Heck, it'll probably buy you a decent van.

[racprops]

"And you do realize the trans, a control kit, and an installation kit will run you about $7500, right? That's A LOT of gas. Heck, it'll probably buy you a decent van."

I was planing on a Junk Yard parts, get the PCM and harness with the transmission, cross member and drive shaft.

You might have a point about using a PCM out of a car or truck with a CAN Buss system.

Will have to look into that.

Rich

[racprops]

OK Looking into this more:

While the top two cogs are overdrive gears on both the 8L90 and the 6L80, 8th is a 0.65 ratio in the new transmission, compared to 0.67 for the 6L80, and Chevy has paired it with 2.41 differential gears in non-Z51 2015 Corvettes (compared to a 2.56 ratio for the 6-speed auto) to reduce engine rpm by 8 percent at 70 mph.

First gear in the 8L90 is 4.56 as opposed to 4.03, and the closer steps between ratios mean improved performance as well as better fuel economy – Chevy is claiming 29 mpg highway, 0-60 in 3.7 seconds, and an 11.9 second quarter mile for the 8-speed LT1. Overall, there is a 7.0 ratio stretch between first and eighth gear.


It seems the transmission controller is NOT part of the PCM, but a stand alone part.

Also it looks like there are three modes of shifting, auto, manual and paddles...OR switches...


Now to find out if it even needs CAN BUS.

Rich

[racprops]

Check this out:

[freebeard]

That could work.

If you invest 10% of that cost into the aerodynamics, you could get as much in improved miles per gallon.

The topper has beveled edges but it's flat on top. It needs a crown that peaks at 30% of the way back from the front and never exceeds a very specific curve.

But really all the opportunity is in the wheels and underbody. You can reduce lift with a bellypan and it's completely invisible to the people who's opinion matter.

[19bonestock88]

Agreed, if you invested any real portion of the cost of swapping an 8L90 but not also it’s LT1 mate I to your van, you could really optimize the aero on it and likely get your 20mpg Highway with a simpler powertrain...

I’d look and see if anybody makes a stand alone trans controller for the 6L80, which would be a cheaper solution than the 8L90 and likely *almost* as good... I don’t see you needing that super low 1st gear unless you’re towing or something...

[racprops]

Thanks.

A belly pan seems like a major project and I am under the idea that my grown effects which is only a couple of inches off the ground keeps a major part of the air from getting under the van.

I have driven Chevy Vans from around 1978, and in the 80s and 90s I drove across the USA about a dozen times. All have had stock bodies.

ALL until this Van was blown around the road by passing Big Rigs. Passing or being passed has always been a bit of a fight, the same for winds and so when I first took this van on its first major road trip knowing it was even higher than all my other vans I expected it to be even worst.

So on the first trip as I over took a BIG RIG braced to handle the bow wake of the truck and slipped right by with no problem, smooth as glass.

WTF....must be a odd cross wind killing the normal bow wake so I again was braced as I over took or was passed by many big rigs before I could relax, this new van with its cosmetic ground effect was REALLY working, cross winds and big rigs were no longer pushing the van around.

After about driving a Chevy vans, a 1994, a 1978 for about 25 years I was very surprised by this behavior. And very happy to have it.

So by this behavior, a MAJOR change in how it handles passing big rigs and wind I really think it is fairly aerodynamic.

So cutting into the roof or making a belly pan seems unneeded.

[racprops]

As for why I want the big first gear: With it I can nearly match the performance of my stock first gear with my stock 3:43 rear end.

With my planed 2:14 to 2:42 rear end it would be a stuck pig with anything less deep.

BUT with the 8L90's tall first 3 gears I can expect even slightly better take off than my stock gearing.

And with all 8 gears reach a much lower RPM range in over drive, around 1000 RPMs at around 80 MPH.

I can have my cake and eat it too, This engine and transmission looks to be even a hotter hot rod off the line and all the way to cruising speed that my old drive train, and be much more able to match RPMs to what ever speed or mountain I may encounter on the road.

So please look at this chart, note the power ranges and the cruising ranges...

And then looks at the chart for my stock setup:

[Ecky]

Crosswind / turbulence stability is not the same as low drag. If your van were truly low drag you could have been in the 20's with your original powertrain. Efficiency gains in the drivetrain are relatively small fruit compared with drag and rolling resistance, which is why most on here focus on those.

[aardvarcus]

If you do indeed have a torque down low engine, matching your existing gear ratio in first is unnecessary and may make you slower. I launched my old 1991 K2500LD with the 5.7 in first, because it was a bit faster. I launch my heavier 1994 K2500 with the 6.5 in second, because it is faster than launching in first. The same transmission (8.63 spread ratio) in both, with the most major difference being the torque curves, the latter having torque down low.

I don't know how you could pick your gearing or cruise RPM until you have at least a torque curve for the motor you will be using. Without doing what the other suggest, you will have a narrow window where this will work well.