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Discussion Starter · #1 ·
GM has been so tight lipped, but since the HummerEV range has been quite impressive even at 70 mph, if we had a basic idea of Cd we could figure out more about the upcoming SilveradoE, Silverado E will definitely be about 800-1000 lbs lighter, and have less rolling resistance (tires), and less powertrain drag (2 drive units vs 3), but the Cd is the most important for highway range.

Some Cd I found online
Hummer H2 .56
Rivian R1T supposed .30 ? I question this one.
Tahoe .36

My Guess
HEV ED1 .46
SilveradoE .35

HummerEV gross consumption about 620 wh/mi in InsideEV 70 mph test, my guess is SilveradoE closer to 500 wh/mi @70 mph

Punching this into my calculator for very rough estimates SilveradoE should have 420-430 miles of range @70 mph
 

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I saw this article that claims .5 for Hummer, .44 for Lightning and .3 for Rivian, but then there are some tests showing Lightning did better at 70mph than Rivian. Rivian range tests do seem to be all over the place and not consistent, likely due to tires.


 

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Discussion Starter · #3 ·
I saw this article that claims .5 for Hummer, .44 for Lightning and .3 for Rivian, but then there are some tests showing Lightning did better at 70mph than Rivian. Rivian range tests do seem to be all over the place and not consistent, likely due to tires.


Hummer H2 was a tested .56 , looking close at the Hummer EV, it's much slicker then the H2, GM hid some clever aerodynamics on the HEV, most people never notice, which I guess is the goal with a design driven vehicle. I think from the frunk floor up the Hummer is pretty good, its from the frunk floor down where things are awful...

I don't think is Lightning .44, its better then that. Rivian R1T .30? come on? with which tires? I would believe .3x for the Rivian, but not .30 . Rivian and the F150 Lightning are about the same in battery size and 70 MPH range. Rivian is smaller but heavier, and mostly steel, F150 only has a steel frame, the entire top hat is aluminum. Hummer is all steel, surprisingly, even the doors, they feel light, but they are steel, or magnetic aluminum, haha! The only aluminum I found on the Hummer body is the tailgate.
 

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Hummer H2 was a tested .56 , looking close at the Hummer EV, it's much slicker then the H2, GM hid some clever aerodynamics on the HEV, most people never notice, which I guess is the goal with a design driven vehicle. I think from the frunk floor up the Hummer is pretty good, its from the frunk floor down where things are awful...

I don't think is Lightning .44, its better then that. Rivian R1T .30? come on? with which tires? I would believe .3x for the Rivian, but not .30 . Rivian and the F150 Lightning are about the same in battery size and 70 MPH range. Rivian is smaller but heavier, and mostly steel, F150 only has a steel frame, the entire top hat is aluminum. Hummer is all steel, surprisingly, even the doors, they feel light, but they are steel, or magnetic aluminum, haha! The only aluminum I found on the Hummer body is the tailgate.
Yeah, GM's new EV BEV3/BT1 design language has turned their previously "for looks" designers into aerodynamic aestheticians, using each brand's classic design cues as a base. I recall a story where Bob Lutz had to really twist Gen 1 Volt-designer Bob Boniface's arm to get him to incorporate a small 2" spoiler on the Volt's rear. But that spoiler added 3 miles of range, which was a huge range win for a small design change when you only have a 10 kWh usable battery to play with. No arm-twisting now. I suspect it may be sort of a game....hiding aero Easter eggs that pay real dividends.

That Hummer EV 70 mph IEVs range test totally blew up my previously-accurate range model. I couldn't find anything in either the driving conditions or Tom's procedure that would have "gamed the range". It now has me putting Hummer images under a microscope to find their secret sauces.

Until I discover hard evidence of GM's baked-in aero magic, I've arbitrarily adjusted my previously-accurate range model to match the field-tested range + kWh used. Now I come up with:

Hummer EV: Cd = 0.40 (yeah!), assuming a 33 sq. ft frontal area. I'm suspecting that Volt-like 2" rear spoiler on the cab's top, slight downward arcing roof taper towards the bed, tail-gate spoiler, and those angular side sail-gussets linking the cab and bed do more than we realized to minimize bed-induced vortices and reduce drag. Also, I suspect things going on everywhere else that I just haven't picked up yet.

Regarding Rivian: There is now substantial evidence both through outside-CFD-modeling and real-word range testing that the Rivian's Cd is in the range of 0.31-0.32. Rivian's engineers and designers did a world-class aero design job, full stop. Frontal area = 30 sq. ft.

The Silverado EV has a different design language, with more sharp edges than Rivian's more-rounded features, but it incorporates essentially all of Rivian's aero tricks + includes the Hummer side cab/bed sails, and if you look closely, you'll see the bed's side panel tops are not horizontal, they rise up higher at the side-sail connection and then gently taper down to the tail gate. That likely maintains attached side-air-flow better than Rivian's horizontal bed rails. But I did notice Rivian uses the same advanced-aero combined rear spoiler/air curtain as the Lyriq's at the cab's back, while the Silverado doe not. The Lyriq shows that GM is familiar with the concept. Perhaps because the Silverado's bed is longer and cab roof tapers down at a steeper angle than the Rivian's, GM's designers found the air curtain feature didn't provide any benefit, or perhaps it was just a small aero/design compromise.

I'm figuring the Silverado likely about matches the Rivian Cd to Cd, but has a 5%-10% larger frontal area, so overall aero drag road load is still higher. I'm now guestimating about 450 miles at 70 mph fixed speed. Cd = 0.32 @ 32 sq. ft frontal area.

Ford is not far behind either the Rivian or Silverado. Except for missing the cab rear spoiler and the Silverado's cab/bed side sail panel, their aero designers also checked all the boxes.

My range model, using 0.36 Cd and 32 sq. ft. frontal area, came up with 271 miles at 70 mph. That closely matches Tom's IEVs 70 mph range test @ 271 miles, performed in near perfect driving conditions.

@Tom E-Tron: I know you and many others are mesmerized by Lucid's drive train, and especially Rawlinson's recent presentation, and want to directly compare it to GM's ultium drive units. But as an engineer who has lately been deeply-steeped into EV drive-train/battery design, what I saw in Peter's video was two parts solid/creative engineering, two parts well-crafted showmanship, and a hint of PT Barnum. Lucid truly did create a world-class drive unit, mechanically-miniaturized and light-weight, perfect for besting it's competitors' luxury platforms. But that is a Rolex design. Peter even described the miniaturized in-shaft differential as a "Swiss watch". But did not mention the Swiss watch cost.

Rolex is different than Timex, but the watch makers/engineers within either brand have the same basic skill sets. Just targeting their skills to radically-different markets. The Ultium platform's centroid is not Rolex. It is Timex. It is $30K Equinox and $40K Silverado WT. It is EVs For Everyone. Not EVs For Saudi Princes. I strongly suspect GM is reserving their Princely-level EV engineering for the soon-to-come Celestiq. We'll likely see a whole other technological level inside that vehicle. Michigan-based hand-crafted Rolex's, straight out of the Warren Global Technical Center.
 

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Discussion Starter · #5 ·
Yeah, GM's new EV BEV3/BT1 design language has turned their previously "for looks" designers into aerodynamic aestheticians, using each brand's classic design cues as a base. I recall a story where Bob Lutz had to really twist Gen 1 Volt-designer Bob Boniface's arm to get him to incorporate a small 2" spoiler on the Volt's rear. But that spoiler added 3 miles of range, which was a huge range win for a small design change when you only have a 10 kWh usable battery to play with. No arm-twisting now. I suspect it may be sort of a game....hiding aero Easter eggs that pay real dividends.

That Hummer EV 70 mph IEVs range test totally blew up my previously-accurate range model. I couldn't find anything in either the driving conditions or Tom's procedure that would have "gamed the range". It now has me putting Hummer images under a microscope to find their secret sauces.

Until I discover hard evidence of GM's baked-in aero magic, I've arbitrarily adjusted my previously-accurate range model to match the field-tested range + kWh used. Now I come up with:

Hummer EV: Cd = 0.40 (yeah!), assuming a 33 sq. ft frontal area. I'm suspecting that Volt-like 2" rear spoiler on the cab's top, slight downward arcing roof taper towards the bed, tail-gate spoiler, and those angular side sail-gussets linking the cab and bed do more than we realized to minimize bed-induced vortices and reduce drag. Also, I suspect things going on everywhere else that I just haven't picked up yet.

Regarding Rivian: There is now substantial evidence both through outside-CFD-modeling and real-word range testing that the Rivian's Cd is in the range of 0.31-0.32. Rivian's engineers and designers did a world-class aero design job, full stop. Frontal area = 30 sq. ft.

The Silverado EV has a different design language, with more sharp edges than Rivian's more-rounded features, but it incorporates essentially all of Rivian's aero tricks + includes the Hummer side cab/bed sails, and if you look closely, you'll see the bed's side panel tops are not horizontal, they rise up higher at the side-sail connection and then gently taper down to the tail gate. That likely maintains attached side-air-flow better than Rivian's horizontal bed rails. But I did notice Rivian uses the same advanced-aero combined rear spoiler/air curtain as the Lyriq's at the cab's back, while the Silverado doe not. The Lyriq shows that GM is familiar with the concept. Perhaps because the Silverado's bed is longer and cab roof tapers down at a steeper angle than the Rivian's, GM's designers found the air curtain feature didn't provide any benefit, or perhaps it was just a small aero/design compromise.

I'm figuring the Silverado likely about matches the Rivian Cd to Cd, but has a 5%-10% larger frontal area, so overall aero drag road load is still higher. I'm now guestimating about 450 miles at 70 mph fixed speed. Cd = 0.32 @ 32 sq. ft frontal area.

Ford is not far behind either the Rivian or Silverado. Except for missing the cab rear spoiler and the Silverado's cab/bed side sail panel, their aero designers also checked all the boxes.

My range model, using 0.36 Cd and 32 sq. ft. frontal area, came up with 271 miles at 70 mph. That closely matches Tom's IEVs 70 mph range test @ 271 miles, performed in near perfect driving conditions.

@Tom E-Tron: I know you and many others are mesmerized by Lucid's drive train, and especially Rawlinson's recent presentation, and want to directly compare it to GM's ultium drive units. But as an engineer who has lately been deeply-steeped into EV drive-train/battery design, what I saw in Peter's video was two parts solid/creative engineering, two parts well-crafted showmanship, and a hint of PT Barnum. Lucid truly did create a world-class drive unit, mechanically-miniaturized and light-weight, perfect for besting it's competitors' luxury platforms. But that is a Rolex design. Peter even described the miniaturized in-shaft differential as a "Swiss watch". But did not mention the Swiss watch cost.

Rolex is different than Timex, but the watch makers/engineers within either brand have the same basic skill sets. Just targeting their skills to radically-different markets. The Ultium platform's centroid is not Rolex. It is Timex. It is $30K Equinox and $40K Silverado WT. It is EVs For Everyone. Not EVs For Saudi Princes. I strongly suspect GM is reserving their Princely-level EV engineering for the soon-to-come Celestiq. We'll likely see a whole other technological level inside that vehicle. Michigan-based hand-crafted Rolex's, straight out of the Warren Global Technical Center.
I 100% agree with you on Peter Rawlinson's presentation, I felt was cheesy, but I am impressed at the different technologies they try, and how they are not shooting to be an also ran, but the best. Having driven a Lucid Air, its be the best balance of Luxury / Performance of any sedan I have ever driven. It CRUSHES the Mercedes S, and to do that with the highest range of any EV in production, and the fastest charging of any EV in production (range added per minute), give more cargo area than an S class, but have the footprint of an E class... Can you say "have your cake and eat it too"? I have yet to find anything its not good at, OK, well price/ value, but that is because Lucid does not have scale. What impresses me most about Lucid drivetrain is the refinement, and power/weight, and there is no gear lash when crawling around, its tight as heck.

On the Hummer, you think the Cd is clear down to .40? You know more about this stuff than me, and I think the top half off the Hummer is pretty good, but the bottom half?

How about the F150 lightning?

Silverado E frontal area should be 3-5 sq ft smaller then Hummer , Hummer Track is 5" wider, mostly just wheels and flares, but has longer control arms, which all see wind.
 

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The bottom half of any EV will always have less drag than an equivalent ICE. The flat bottom with the battery has less cavities for vortex and turbulence, especially body on frame with a driveshaft.. But you cannot avoid the wheel wells and tires causing drag.
 

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I 100% agree with you on Peter Rawlinson's presentation, I felt was cheesy, but I am impressed at the different technologies they try, and how they are not shooting to be an also ran, but the best. Having driven a Lucid Air, its be the best balance of Luxury / Performance of any sedan I have ever driven. It CRUSHES the Mercedes S, and to do that with the highest range of any EV in production, and the fastest charging of any EV in production (range added per minute), give more cargo area than an S class, but have the footprint of an E class... Can you say "have your cake and eat it too"? I have yet to find anything its not good at, OK, well price/ value, but that is because Lucid does not have scale. What impresses me most about Lucid drivetrain is the refinement, and power/weight, and there is no gear lash when crawling around, its tight as heck.

On the Hummer, you think the Cd is clear down to .40? You know more about this stuff than me, and I think the top half off the Hummer is pretty good, but the bottom half?

How about the F150 lightning?

Silverado E frontal area should be 3-5 sq ft smaller then Hummer , Hummer Track is 5" wider, mostly just wheels and flares, but has longer control arms, which all see wind.
Right on that Cd. My eyes don't believe it either. I just can't wrap my head about 0.40 with the so-boxy shape + the apparent total lack of typical aero wheel-wells +the Hummer-style upright windows. But when I start the range calc backwards, taking the definite average speed, distance, and kWh used, which determines the actual "road load", either that Hummer magically lost 1,500 lbs plus rode on LRR highway tires plus got next-generation Ultium SiC inverters, or there's some aero voodoo going on. We'll put a big * by that number until we get another confirming range test.

Here's a fun explanation: I grew up in the SF Bay Area, at one time living spitting-distance from the GM Fremont plant where my stepdad worked. There was a place in the Santa Cruz mountains south of us called "the Mystery Spot", where apparent physics-defying things happened. Pool balls rolling "uphill" on a pool table, etc. (all using optical illusions) This is the first time Tom has done a range test in the Ypsilanti area. Can anyone in MI advise if "strange physic-defying things" happen around Ypsilanti?
 

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Right on that Cd. My eyes don't believe it either. I just can't wrap my head about 0.40 with the so-boxy shape + the apparent total lack of typical aero wheel-wells +the Hummer-style upright windows. But when I start the range calc backwards, taking the definite average speed, distance, and kWh used, which determines the actual "road load", either that Hummer magically lost 1,500 lbs plus rode on LRR highway tires plus got next-generation Ultium SiC inverters, or there's some aero voodoo going on. We'll put a big * by that number until we get another confirming range test.

Here's a fun explanation: I grew up in the SF Bay Area, at one time living spitting-distance from the GM Fremont plant where my stepdad worked. There was a place in the Santa Cruz mountains south of us called "the Mystery Spot", where apparent physics-defying things happened. Pool balls rolling "uphill" on a pool table, etc. (all using optical illusions) This is the first time Tom has done a range test in the Ypsilanti area. Can anyone in MI advise if "strange physic-defying things" happen around Ypsilanti?
From my experience with the Hummer EV I have no problem believing Tom's truck was equipped the same as mine, I am getting 400 miles in mixed driving, and not trying to stretch it. I just have not drive a long distance at 70 mph, but tom was consuming 618 wh/mi, which is not great, not bad.

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I saw this article that claims .5 for Hummer, .44 for Lightning and .3 for Rivian, but then there are some tests showing Lightning did better at 70mph than Rivian. Rivian range tests do seem to be all over the place and not consistent, likely due to tires.


The Rivian was tested under much worse environmental conditions, and they assumed the size of the battery instead of using the actual size. I was surprised Edmunds would push misinformation like they did, but not entirely.
 

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Right on that Cd. My eyes don't believe it either. I just can't wrap my head about 0.40 with the so-boxy shape + the apparent total lack of typical aero wheel-wells +the Hummer-style upright windows. But when I start the range calc backwards, taking the definite average speed, distance, and kWh used, which determines the actual "road load", either that Hummer magically lost 1,500 lbs plus rode on LRR highway tires plus got next-generation Ultium SiC inverters, or there's some aero voodoo going on. We'll put a big * by that number until we get another confirming range test.

Here's a fun explanation: I grew up in the SF Bay Area, at one time living spitting-distance from the GM Fremont plant where my stepdad worked. There was a place in the Santa Cruz mountains south of us called "the Mystery Spot", where apparent physics-defying things happened. Pool balls rolling "uphill" on a pool table, etc. (all using optical illusions) This is the first time Tom has done a range test in the Ypsilanti area. Can anyone in MI advise if "strange physic-defying things" happen around Ypsilanti?
I think the wind direction changed through his test from "not detrimental" to "helpful" when he turned around in his loop.
 
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