MPG ICE using cybertruck body

[Tinker71]

Is there a real engineer out there that can calculate what the MPG would be if you put a ford ecoboost or 4 cylinder cummins turbo diesel in a CT with the current 10 speed trannies? Not that I would want to do this.

I don't think people realize how important aerodynamics will be for range. Most bed campers and high profile campers will destroy range. 50% range reduction might be conservative. Even an open vault might cut your range by 30 miles.

BTW if I talked anybody out of a CT I will buy your <100,000 total/50000 dual motor reservation for $200 Tinker71

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[Dids]

Is there a real engineer out there that can calculate what the MPG would be if you put a ford ecoboost or 4 cylinder cummins turbo diesel in a CT with the current 10 speed trannies? Not that I would want to do this.

I don't think people realize how important aerodynamics will be for range. Most bed campers and high profile campers will destroy range. 50% range reduction might be conservative. Even an open vault might cut your range by 30 miles.

BTW if I talked anybody out of a CT I will buy your <100,000 total/50000 dual motor reservation for $200 Tinker71

People don't realize aerodynamics as that important because they aren't., I'm not saying they aren't important, just saying they are not the most important.
For instance a current Ford pickup truck ICE has a lower city range than highway. Low speed stop and go with minimal aero load uses more energy than high speed with higher aero load. This would not change if you put it in a more aero vehicle like the CT.
Will increasing the load wether aero or mass decrease range? Yes it always takes more energy to move a higher load.
Will the aero become dominate at highway speeds? That is unknowable since there are many different configurations that could increase load. For instance dragging a parachute would probably mean that the aero portion of the load becomes dominant but outside of a scenario like that it is unlikely that aerodynamics will be the primary increase in load.
Extrapolating that a certain camper reduces ICE range by 50% and therefore it will reduce CT range greater because CT is more aerodynamic is false since most normal campers weight is the dominant load. When weight is the dominant load then the components of power will point in the expected direction of performance.
Power is force(torque) x speed(time).

 

[Mabrrr2]

I have read that you cant buy a reservation and the only way that it would be possible is to purchase the truck from someone the day they bought it.

 

[Tinker71]

People don't realize aerodynamics as that important because they aren't., I'm not saying they aren't important, just saying they are not the most important.
For instance a current Ford pickup truck ICE has a lower city range than highway. Low speed stop and go with minimal aero load uses more energy than high speed with higher aero load. This would not change if you put it in a more aero vehicle like the CT.
Will increasing the load wether aero or mass decrease range? Yes it always takes more energy to move a higher load.
Will the aero become dominate at highway speeds? That is unknowable since there are many different configurations that could increase load. For instance dragging a parachute would probably mean that the aero portion of the load becomes dominant but outside of a scenario like that it is unlikely that aerodynamics will be the primary increase in load.
Extrapolating that a certain camper reduces ICE range by 50% and therefore it will reduce CT range greater because CT is more aerodynamic is false since most normal campers weight is the dominant load. When weight is the dominant load then the components of power will point in the expected direction of performance.
Power is force(torque) x speed(time).

On a flat highway route aerodynamics will prevail. (Say Texas) Once moving, what is changing with mass? A tiny bit of rolling resistance? In my ICE Sienna I don't even need brakes going down a 5% grade at 70 mph. Wind resistance keeps all that potential energy in check. A CT on a hilly back country road with a tall camper mass will likely prevail. 35 MPH. But then regen actually might help you out, but that is not the majority of an average trip.

The CD for an average pick up is .45 and for a CT is .30 at highway speeds. Since you still have to add frontal area get overall drag resistance to the formula it is a safe bet that towing a 10' tall bumper pull weighing 7500 lbs air resistance will still prevail. A loaded Semi box truck with CD of .96 weighing 60,000 lbs can still get 7 MPG. Weight is hardly the issue Rectangular box has a CD of 2.1 Again do you accept the challenge. I don't have the training. I bet you could get 40 MPG highway with a cummins in a cybertruck body.

 

[ajdelange]

The CT will pull about 450 Wh/mi. EPA uses 33700 Wh/gal as the energy content of petrol. Thus the mpgE of a CT is 33700/450 = 74.9. The remainder of the job depends on what you think the overall efficiencies of the ICE and BEV power trains are. If you assume 85% for the BEV and 35% for the ICE you would have 74.9*.35/.85 = 30.8. If you assume the ICE is only 20% efficient your estimate for it would be 17.6 mpg.

 

[ajdelange]

Weight is the biggest factor as inertial load and potential (gravitational) load are both directly proportional to it. Drag is relatively unimportant unless you tow at speeds at which no sane person would tow. See #7 at https://www.cybertruckownersclub.co...rtruck-one-vendor-is-testing.1655/#post-25272

 

[Crissa]

I think you guys are looking at it all wrong.

https://www.cybertruckownersclub.co...ertruck-one-vendor-is-testing.1655/post-25256

Having an efficient motor means that drag becomes relatively larger in calculations of range (which is what you care about). ICE motors are wasting extra energy at idle or acceleration, not to mention just being worse at keeping moving.

-Crissa

 

[Dids]

I think you guys are looking at it all wrong.

https://www.cybertruckownersclub.co...ertruck-one-vendor-is-testing.1655/post-25256

Having an efficient motor means that drag becomes relatively larger in calculations of range (which is what you care about). ICE motors are wasting extra energy at idle or acceleration, not to mention just being worse at keeping moving.

-Crissa

Efficiency is amount of work performed per unit of energy. In reality a higher load on an electric motor makes it more efficient, not less. ( The most efficient electric motor is fully loaded) You are correct, drag is a larger component of load for an electric motor but that is only because of electric motors flat torque curve and not because it is more efficient.
In other words adding more load be it aero or weight affects an electric motor less than it affects ICE with a corresponding smaller decrease in range for electric.
I can hear the heads exploding....

 

[Crissa]

EVs are straight up more energy efficient than direct ICE motors, but yeah.

Drag is the larger component here. We need to drag big boxes around, and that's going to be the part that hurts our range the most.

Also, cargo weight (in relation to range) is a function relative to total mass : The battery pack is already heavy, so to double our gross weight would be more stuff than with a lighter ICE vehicle.

-Crissa

 

[Tinker71]

Efficiency is amount of work performed per unit of energy. In reality a higher load on an electric motor makes it more efficient, not less. ( The most efficient electric motor is fully loaded) You are correct, drag is a larger component of load for an electric motor but that is only because of electric motors flat torque curve and not because it is more efficient.
In other words adding more load be it aero or weight affects an electric motor less than it affects ICE with a corresponding smaller decrease in range for electric.
I can hear the heads exploding....

The CT will pull about 450 Wh/mi. EPA uses 33700 Wh/gal as the energy content of petrol. Thus the mpgE of a CT is 33700/450 = 74.9. The remainder of the job depends on what you think the overall efficiencies of the ICE and BEV power trains are. If you assume 85% for the BEV and 35% for the ICE you would have 74.9*.35/.85 = 30.8. If you assume the ICE is only 20% efficient your estimate for it would be 17.6 mpg.

Since your appear to be the only engineer on this thread. What I am trying to get to is if a CT does say 350 Wh/mile on the flats at 75 MPH with .30 CD what would at CT with a exceptionally light camper that changes the CD to a 1.7 under the same conditions? Say it is a box that extends 4 feet from the peak of the existing roofline x the width and depth of the bed. I think the exceptionally low CD with the bed closed is causing a disproportionate advantage over conventional pick ups. Even a lumber rack is going going to have a major impact on range. I may play with the math this week end. Anybody know the frontal area of the CT?

 

[Dids]

Since your appear to be the only engineer on this thread. What I am trying to get to is if a CT does say 350 Wh/mile on the flats at 75 MPH with .30 CD what would at CT with a exceptionally light camper that changes the CD to a 1.7 under the same conditions? Say it is a box that extends 4 feet from the peak of the existing roofline x the width and depth of the bed. I think the exceptionally low CD with the bed closed is causing a disproportionate advantage over conventional pick ups. Even a lumber rack is going going to have a major impact on range. I may play with the math this week end. Anybody know the frontal area of the CT?

1. Your CD estimate of 1.7 is very high and CT 0.3 isn't so very low, yes it's lower than a typical pickup but ford f150 has a CD 0.36 and that is with an open bed. ( My guess? additional 4 ft x 4 ft frontal might double the drag) so 0.6 is more realistic.
2. We do not know the weight of CT and Wh/mi are guesses. Sandy Munro says the CT will actually be a lighter vehicle than people think due to exo skeleton, but if we say it will use about 450 wh/mi we then need to guess how much it weighs to guess how much rolling friction is. Let's guess .01 CR.
What ends up happening? Without knowing some of the vital numbers doing math on guesses produces results that are very misleading.
You have range anxiety, the number 1 thing people have that is also the number 1 thing that people say is not an issue once they actually use an EV.

 

[ajdelange]

Because there are so many variables to consider it is hard to give realistic answers. We can, however gain some insights by looking at the numbers. A 5500 lb CT driving for an hour at uniform speed of 50 mph on flat terrain with Cd*A = 1.6, drive train efficiency of 95%, assumed rolling resistance coefficient of 0.009 and wheel slip of 0.1 will produce a load budget, all in Wh/mi, something like this

5500 lbs Speed 50 to 50 Avg 49.9 mph, 0.0 ± 0.0 %grade , Wh/mi Total: 357.8, Drive: 17.7, Slip: 33.7, Drag: 206.4, Roll: 96.7. Gravity: 0.0, Inertial: 3.3.; Recov. 0

Thus the total Wh/mi is 358 which seems reasonable which load is made up of 17.7 Wh/mi drive train losses, 33.7 wh/mi slip losses, 96.7 wh/mi rolling resistance losses and, of course is this case, the major loss, drag of 206.4 wH/mi. There is only a small (because it is averaged out over the 50 miles driven) inertial load associated with accelerating to 50 mph.

Of all those loads only the insignificant inertial load and the rolling load depend on the weight. Were you to tow a trailer of approximately the same frontal area as the CT but with a Cd 1.7/.3 = 5.7 times greater that trailer would present a drag load of 5.7*206.4 = 1176.5 Wh/mi. The trailer would present a small inertial load but no power train losses (it doesn't have a power train) or slip losses (it's wheels aren't delivering torque to the road). But there would be a rolling resistance loss. Assuming the weight of the trailer to be about the same as that of the truck the rolling loss would be about the same 97 Wh/mi for a total estimated load for the trailer of 1273.5 Wh/mi. Add to this the 359 Wh/mi for the truck and you have 1632.5 which implies the range with such a rig would be 359/1632.5 = 22% of the truck's rated range (assuming its rated consumption will indeed be 359 Wh/mi). This tells me that trailers don't have Cd as great as 1.7 and indeed it seems they are more likely to be around 0.6 - 0.7. But that's not the whole story. Frontal area is the other part.

Now when you get into more interesting (realistic) driving conditions things change.

5500 lbs Speed 50 to 20 Avg 41.9 mph, 0.5 ± 1.5 %grade , Wh/mi Total: 645.3, Drive: 18.4, Slip: 34.9, Drag: 163.9, Roll: 96.7. Gravity: 80.8, Inertial: 250.6; Recov. 0

In this budget a 5500 lb RV is driven uphill on an average grade of 0.5% but the grade can vary from +2% to -1%. The speed limit is 50 but the driver has to slow for curves, other traffic etc and he may have to slow to as low as 20 mph. The actual profile determines in very large measure what the budget will be and the numbers above are from a randomly generated one. Notice that there is now a gravitational load of 81 Wh/mi (from going up the grade and up the little hills too) and an inertial load (from speeding up after slowing down). Note that the average speed is only 42 mph and that this reduces the total drag load to 164 and that the inertial load is greater than the drag load. Keep in mind that the gravity and inertial and to a lesser extent the rolling loads all increase directly with weight e.g.

5700 lbs Speed 50 to 20 Avg 41.9 mph, 0.5 ± 1.5 %grade , Wh/mi Total: 661.8, Drive: 18.7, Slip: 35.5, Drag: 163.9, Roll: 100.2. Gravity: 83.7, Inertial: 259.7; Recov. 0

Now the CT has regen. If we turn that on we can recover say 80% of the kinetic and potential loads as in this budget:

5500 lbs Speed 50 to 20 Avg 41.9 mph, 0.5 ± 1.5 %grade , Wh/mi Total: 423.3, Drive: 18.4, Slip: 34.9, Drag: 163.9, Roll: 96.7. Gravity: 58.9, Inertial: 50.5.; Recov. 0.8

Recovery is a very important part of the story and that is because you can turn regen on in the truck but not the trailer. I often try to simplify the problem by asking people to consider towing a second CT behind their CT. The loads for the towing CT would be those for the regen on case (423 wH/mi) while those for the second would be for the regen off case less powertrain and slip losses, 661.8 - 18.7 - 35.5 = 607.6. This brings the total load on the towing CT to 645.3 + 607.6 = 1252.9 Wh/mi which implies 29% range relative to rated range.

Finally let's look at a budget with a steep average grade:

5500 lbs Speed 50 to 20 Avg 41.9 mph, 2.0 ± 1.5 %grade , Wh/mi Total: 806.3, Drive: 27.8, Slip: 52.8, Drag: 163.9, Roll: 96.7. Gravity: 214.5, Inertial: 250.6; Recov. 0

This makes it clear that if your destination is higher than your starting point you are going to pay for that in battery. Note that for the tractor you will recover much of what you paid but that for the trailer you won't.

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