Jaguar I-Pace

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Col Lamb
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Post by Col Lamb »

Merc CLA and Beamer 5 series have a Cd of just .22

Audi A4 is.23

Prius .24

Ionic .24

Even a Ford Focus is .25

There are a lot of cars with a Cd of under .3

Considering that the Audi 100 of the early eighties had .30 etched ito its rear quarter window to signify its aerodynamic nature the automobile industry has progressed at a snails pace in aerodynamics.

Its not just aerodynamics that need improving its the overall weight that is going in the wrong direction
Col
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Kasfranks99
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Joined: Thu Jul 28, 2016 8:38 pm

Post by Kasfranks99 »

Found this very interesting on the iPace. All stripped down at the motor show.

https://jalopnik.com/the-coolest-electr ... 1829506735
GTS 😀
johnd
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Joined: Sat Nov 22, 2014 10:23 pm

Post by johnd »

Couple of footnotes on the range/gearing/efficiency etc topics.

I-Pace motors (like most EVs I guess) are already geared, albeit with a single gear ratio - see image attachment below. It's obviously a decision made during the design process as to what the optimum gearing should be and which presumably dictates the trade-off between steady speed and efficiency and hence range at a given steady speed. Still seems likely to me that a major reason for less efficient I-Pace performance at eg 80mph is inferior aerodynamics more than anything else.

Second, there's some evidence that efficiency results may be quite sensitive to exact test conditions, eg tyres' rolling resistance and OAT (outside air temperature). See eg:

I-Pace_motors.JPG

Macan SD (Rhodium) www.porsche-code.com/PH4H6XU3 June 2016

Real mpg at Fuelly
Deleted User 1874

Post by Deleted User 1874 »

Col Lamb wrote: Wed Oct 10, 2018 6:09 pm Merc CLA and Beamer 5 series have a Cd of just .22

Audi A4 is.23

Prius .24

Ionic .24

Even a Ford Focus is .25

There are a lot of cars with a Cd of under .3

Considering that the Audi 100 of the early eighties had .30 etched ito its rear quarter window to signify its aerodynamic nature the automobile industry has progressed at a snails pace in aerodynamics.

Its not just aerodynamics that need improving its the overall weight that is going in the wrong direction
Listing literally ALL the cars with ultra-low Cd figures doesn't make it the norm! Some of them only manage it in very specific configurations too. Here's a list of the current benchmarks:-

https://www.motoringresearch.com/car-ne ... cars-2018/

Also notice that not many SUVs make it onto that list (actually just the Tesla X) and saloons have an inherent advantage over hatchbacks (just compare the Focus saloon vs hatch). Have to say Mercedes and BMW are doing very well here, as are Tesla and Audi. Don't see any Jags there though.

The point stands that ultra-low Cd is one of the things that any modern car should really have and especially a range critical EV! A low frontal area is also desirable to minimise the product CdA, but that obviously involves some compromise with cabin space, headroom etc. The worst case scenario is a tall, wide, boxy SUV like a Range Rover with a Cd of 0.37 and huge frontal area. Incidentally the Macan has a pretty unimpressive, but typical SUV Cd figure of 0.36-0.37 depending on spec.
Deleted User 1874

Post by Deleted User 1874 »

johnd wrote: Wed Oct 10, 2018 10:11 pm Couple of footnotes on the range/gearing/efficiency etc topics.

I-Pace motors (like most EVs I guess) are already geared, albeit with a single gear ratio - see image attachment below. It's obviously a decision made during the design process as to what the optimum gearing should be and which presumably dictates the trade-off between steady speed and efficiency and hence range at a given steady speed. Still seems likely to me that a major reason for less efficient I-Pace performance at eg 80mph is inferior aerodynamics more than anything else.

Second, there's some evidence that efficiency results may be quite sensitive to exact test conditions, eg tyres' rolling resistance and OAT (outside air temperature). See eg:
Yes of course there is always a single drive gear to match the speed range of the electric motor to the driven wheel speed range. But not necessary to have multiple gears to provide an efficient 0-150 mph road speed range. It will be interesting to see if the new Tesla Roadster has a second gear to reach 250 mph! It may well require it, but I'm not sure.

I agree aerodynamics are going to be a major factor against the iPace at motorway speeds, where aero drag is the dominant force to overcome. 22" wheels are not going to do it any favours either, so I would strongly advise not to bling out on those if you need maximum range.

Quick article here supports this view. A Cd of 0.29 is simply not very impressive in this company and I think it will hurt Jag more than they expected.

https://insideevs.com/efficiency-jaguar-i-pace-falters/
Deleted User 1874

Post by Deleted User 1874 »

Col Lamb wrote: Wed Oct 10, 2018 6:09 pm
Considering that the Audi 100 of the early eighties had .30 etched ito its rear quarter window to signify its aerodynamic nature the automobile industry has progressed at a snails pace in aerodynamics.

Its not just aerodynamics that need improving its the overall weight that is going in the wrong direction
Agreed on both these points. With the Cd figure, there is obviously a lower limit that you simply can't get past and I think we are getting down very close to that limit with figures like 0.22. I know the Tesla team were aiming for absolute minimum Cd with the Model 3 and 0.23 was their best effort, ultimately missing their target figure I believe of 0.21. The Merc had to be made in a very specific configuration to achieve its 0.22 as well, it's not the standard baseline model figure. In the past the industry has always been aware of Cd and wind tunnels have long been available, but they have always compromised on Cd for improvements in other parameters such as wind noise, lift coefficients and of course simple cost saving. But now Cd is coming back into focus as we move into the EV world, where range is a critical parameter. So we are seeing a big push with cutting edge cars now achieving figures as low as 0.22 and maybe 0.20 is achievable with no compromise?

Weight is another fundamental parameter to minimise and even more of a challenge with EVs. It's much less critical for motorway cruising efficiency but for handling, ride and acceleration it's all bad news.
Dandock
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Post by Dandock »

Once, whenever that is, a viable infrastructure for all marques is in place will not range anxiety simply be the same as mpg when you pays your money and takes your choice.
VG Petrol S http://www.porsche-code.com/PHIVCQU7           And a GT3 RS... by Lego! Not crash-tested! 😀
Deleted User 1874

Post by Deleted User 1874 »

Dandock wrote: Thu Oct 11, 2018 2:26 pm Once, whenever that is, a viable infrastructure for all marques is in place will not range anxiety simply be the same as mpg when you pays your money and takes your choice.
Range anxiety is only really a thing for small battery EVs like the Leaf, Zoe, i3 etc. It's not really something people with Teslas generally suffer from. iPace drivers will be somewhere in the middle with the current patchy charging infrastructure. The most range anxiety I've suffered from has been in ICE cars when running on fumes. We've all been there for sure! Now you could argue that the same applies to EVs, but the sat nav is clever enough to prevent it ever happening, guiding you to a Supercharger long before range becomes critical. Plus you tend to be less complacent. I've lost count of the number of times I've skipped a filling station when the fuel light has first come on thinking I can just find another one a bit further along and then ended up desperately searching for one on fumes! Can't say I've ever actually run out on the road, but certainly had a few very close scrapes.
Dandock
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Post by Dandock »

Peteski wrote: Thu Oct 11, 2018 4:33 pm
Dandock wrote: Thu Oct 11, 2018 2:26 pm Once, whenever that is, a viable infrastructure for all marques is in place will not range anxiety simply be the same as mpg when you pays your money and takes your choice.
Range anxiety is only really a thing for small battery EVs like the Leaf, Zoe, i3 etc. It's not really something people with Teslas generally suffer from. iPace drivers will be somewhere in the middle with the current patchy charging infrastructure. The most range anxiety I've suffered from has been in ICE cars when running on fumes. We've all been there for sure! Now you could argue that the same applies to EVs, but the sat nav is clever enough to prevent it ever happening, guiding you to a Supercharger long before range becomes critical. Plus you tend to be less complacent. I've lost count of the number of times I've skipped a filling station when the fuel light has first come on thinking I can just find another one a bit further along and then ended up desperately searching for one on fumes! Can't say I've ever actually run out on the road, but certainly had a few very close scrapes.
From what I read on here Tesla are pretty well sorted for principal routes. What needs to happen is for Ionity and whatever else to get a comprehensive network sorted. As I said once these networks are thoroughly sorted range will be as relatively unimportant as mpg and vehicle purchases will be based once again on the choice between performance and economy.

As you say, though, the bigger challenge is for the smaller vehicles that cannot comprise the battery volume. We therefore have to wait for the technology to rise to that challenge.
VG Petrol S http://www.porsche-code.com/PHIVCQU7           And a GT3 RS... by Lego! Not crash-tested! 😀
Dandock
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Joined: Sat Jun 06, 2015 7:29 pm

Post by Dandock »

When in France a couple of weeks ago we stopped at a new Aire. I’m sure there was an Ionity charger there although I couldn’t see it on their website but Ive just wondered what their coverage was like right now.

https://ionity.eu/en/where-and-how.html
VG Petrol S http://www.porsche-code.com/PHIVCQU7           And a GT3 RS... by Lego! Not crash-tested! 😀
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