Its not always about MPG

[Frank Lee]

Ummm… OK?

[Vman455]

Originally Posted by Tahoe_Hybrid

don't worry my 6.0L is doing a bit better then that 3.0l engine you got there.

what i'm worry about is making sure the battery does not go flat at this point from it sitting about it's 4900$ for a replacement.. Yes i can afford it

I rather invest that once the market bottoms out in the next week it should be crumbing by Monday or Tuesday.. it's going to be a real shell shocker market correction... it's going to drop down to about 13-14k. when it goes back up i could buy many batteries. then with the 5k = 30k = 1 free battery

yeah I only got 18.4 last time but it was idling for 4 hours but the majority of the time in autostop(had to keep warm waiting inline at the store not for Toilet paper (just for general items for the week) ( i stocked up on TP & water months ago when they first mention it back in January ..) 200IQ!

This legitimately reads like a press conference. Type three periods if you're being held hostage.

[oil pan 4]

A fool and money are soon parted.

[ksa8907]

40mpg tank average? I will personally wager $100 you will not achieve that with that vehicle.

30mpg tank average? Still very doubtful.

[aerohead]

Originally Posted by Tahoe_Hybrid

It has very aggressive DFCO. That is how i'm able to get that many mpg in the first place..

I suspect the Electrical motor is spinning the engine in DFCO... with a OBD reader you can see 0.00v on the upstream o2 sensor. that mean no fuel to air ratio.


when i first saw that i thought my sensor was broken or some other issue..


since there is no "engine braking"
it feels like it's in "neutral gear"

if I shift it into Manual Mode it has "engine braking" and you stop pretty quickly

Under steady,constant speed cruising,where the engine would develop its best BSFC,and the motor wouldn't be in the equation,your Road Load Horsepower would determine your mpg.DFCO wouldn't enter into the equation.And so it would come down to rolling resistance and aero drag.There's no magic sauce as far as tires are concerned,unless your on a railroad track.Which leaves aerodynamics.I've driven hybrids enough to know that the electric motor is essentially 'parked' on road trips,used only for passing or hill-climbing.You need a low enough load to keep the engine in cylinder deactivation mode.And at that point,BSFC will only take you so far.

[Ecky]

Just read about this transmission - turns out it isn't a 4 speed auto! At least, in typical operation it isn't. It has three orbital gearsets, similar to how a Prius works, and no torque converter.

https://www.caranddriver.com/reviews...rid-road-test/

This Tahoe is the first “full hybrid” from General Motors, meaning that it can run purely on electric power at low speeds. It uses a new two-mode hybrid system that is a joint development of GM, BMW, Chrysler, and Daimler and is fundamentally different from the hybrid powertrains used by Toyota and Honda.

The transmission resembles a conventional four-speed automatic to which two 80-hp electric motors are integrated by marrying them to the transmission’s three planetary gearsets. Despite the two-mode name, the transmission, which fits into the same space as the automatic in conventional Tahoes, seems to operate in three distinct modes.

The first mode is continuously variable (CV) and provides ratios from infinity to 1.70. The Tahoe always starts in this mode because it lets the transmission take off smoothly from a stop without the need for a torque converter. When accelerating gently, you can stay in this mode using only the electric motor up to 32 mph, but usually, the 6.0-liter V-8 cuts in to provide additional power.

The second mode also uses CV operation but with a different planetary gearset to provide ratios from 1.70 to a deep overdrive of 0.50 (used during coasting and regenerative braking). This mode provides the benefits of a CVT at higher speeds while keeping the electric motors running in their most efficient rpm range.

Finally, the transmission has four fixed ratios, which are selected when the electric motors are needed to charge the batteries or when towing heavy loads. The powertrain management system, which GM calls the “hybrid optimizing system,” juggles the mode and the ratio to provide the most efficient operation at each driving load.

The fixed ratios are as follows:

CVT1 - 0-1.70
CVT2 - 1.70-0.50
1st - 3.69
2nd - 1.7
3rd - 1.0
4th - 0.73
Rear ratio : 3.08

In 4th gear it's turning 1800rpm @ 75mph - which is still pretty great! However this is not how it typically operates. When running continuously variable ratios (which is whenever the batteries aren't completely flat) it can drop down to as low as 1230rpm at 75mph.

[Frank Lee]

That's a lotta tech for solo driving a barn down the interstate only to barely break 20 mpg in the real world.

[aerohead]

Originally Posted by COcyclist

Perhaps I am being picky about terms but I would like to see some consensus on what we are calling spats and what we are calling skirts. I was under the impression that spats are the little plastic rectangles that most car makers are using in front of the tires, like the white spats we wore to cover the front of our black shoes in marching band (or the massive ones on the green Jetta).

In the 50s, fender skirts came down over the top of the rear tire. In the 90s we got side skirts that lowered the rocker panels between the front and rear tires.

OP- I think you will have to go full Basjoos on this to significantly decrease your Cd. I have found air dams all get ripped off sooner or later. I am using a full belly pan with diffuser, inner and outer side skirts and small spats in front of the tires. All have stayed on winter and summer and have greatly increased coasting distances and mpg in my experience. A full boat tail is too hard to live with day to day for me and has not been done yet on my car.

*'Spats',according to Hucho,are an inner fender which encloses a front wheel within the wheelhouse.Ford used this technology on the 1983 Probe-IV concept car.
*'Skirts' have always defined any panel which spans the wheel opening,to enclose and shelter a wheel,front or rear, from the airstream.

[aerohead]

Originally Posted by Tahoe_Hybrid

I had problems with the electrical causing issues with the Engine control Module & hybrid controller.. Preventing EV and auto stop from working correctly over the last year...

it will be higher this month. as i fixed the issue the positive cable was caked on with dirt and oil... it will be in the 24-25 range for the city. this month..


also i said 40-48mpg could be possible if i could lower the drag. a bit as it will be in EVT mode.more often . which runs the engine at 1,000 rpm at 38mph to 48mph..


the best I have gotten was 31.2mpg on the highway.
as i was able to keep in in the eco mode most of the time.. 40+MPG would be possible on the highway... with some aero mods..


I'll make another entry one for City and one for highway so everything will get deleted and re install the numbers

I ran back-of-the-envelope numbers on the Tahoe.If,without hypermiling,you're currently experiencing 31.2-mpg @ 60-mph,in order to achieve 40-mpg,under identical conditions,would require a drag reduction to Cd 0.136,lower than the GM Sunraycer,solar race car of 1987.A 60% drag reduction (if we presume Sunraycer's current Cd is adjusted for a crosswind-averaged coefficient.
The 'baby' template model registered Cd 0.1201 @ zero-yaw with complete canoe fairings on all wheels.
There's no 'physics' boundary obstructing your achieving the new target,however the man-hours necessary for fabrication might blow your 'human-capital' budget all to ---l.

[Tahoe_Hybrid]

Originally Posted by Ecky

Just read about this transmission - turns out it isn't a 4 speed auto! At least, in typical operation it isn't. It has three orbital gearsets, similar to how a Prius works, and no torque converter.

https://www.caranddriver.com/reviews...rid-road-test/




The fixed ratios are as follows:

CVT1 - 0-1.70
CVT2 - 1.70-0.50
1st - 3.69
2nd - 1.7
3rd - 1.0
4th - 0.73
Rear ratio : 3.08

In 4th gear it's turning 1800rpm @ 75mph - which is still pretty great! However this is not how it typically operates. When running continuously variable ratios (which is whenever the batteries aren't completely flat) it can drop down to as low as 1230rpm at 75mph.

I was able to run it at 1850rpm at about 85mph in v4 mode too bad it's goved to 95MPH..


my IAT/MAF is malfunctioning... I was recording a intake temp of 80degrees when it was 57F on a stone cold dead start (Engine was not running right funky idle ) today it was the correct temp, so that pretty much rules it's faulty IAT/MAF combo....