Electric cars and cooling drag

[JulianEdgar]

Originally Posted by ME_Andy

The original post has been edited so this discussion is almost worthless now.

As indicated in the edit pane, I fixed a typo. Nothing else changed.

[JulianEdgar]

Originally Posted by freebeard

That's probably it.


Could you find an example? aerohead excluded?

Sorry, Aerohead doesn't count then?

[freebeard]

I'll give you Aaerohead, the assertion was 'a few people'. You're welcome for the proofing.

[JulianEdgar]

Originally Posted by freebeard

I'll give you Aaerohead, the assertion was 'a few people'. Your welcome for the proofing.

Your = "you're". That's fine, think nothing of it.

I can't be bothered trawling through thousands of posts. Maybe it was just Aerohead and I was trying to be tactful.

[freebeard]

We're even. I planned it that way.

[oil pan 4]

Originally Posted by freebeard

I'll give you Aaerohead, the assertion was 'a few people'. You're welcome for the proofing.

It makes since to me. It fills in a lot of blanks to the question "why is this guy the way he is".

I've lost count of posts that say, "If it were an electric vehicle then its Cd would be [and then the poster reduces the cooling drag to zero]."

Sounds like an aerohead, total n00b, or me 20 year ago quote.

[aerohead]

Originally Posted by JulianEdgar

Forgive me for being frustrated, but it has been said time and time again here that BEVs have very low / no cooling drag.

The only available evidence that I have been able to find does not support that.

So in response to my post, we have:

• a few acknowledgements and thoughtful posts eg the temperature ratio of coolant versus atmospheric
• a range of denials
• a lot of irrelevant information (eg cooling drag for internal combustion engine cars)
• the purported change in cooling drag for internal combustion engine cars if they were hypothetical BEVs that needed no cooling (huh?)
• people who apparently think the size of the grille represents the percentage of cooling drag
• people who think that comparing the ICE version against the BEV version of a car somehow gives percentage cooling drag for the BEV version
• people who say my sample was too small / biased / etc... but have no alternative data

- and so on.

Honestly, what is the point of trying to correct misapprehensions here with actual, real, wind tunnel data?

Perhaps you'll need to surrender the the reality that members will attempt the share data they believe germane, even if only tangentially, as sometimes, that's where distinctions are made.

[aerohead]

* the Chevy Spark ICE is Cd 0.36. BEV variant is Cd 0.325.
* the FIAT 500 Lounge ICE is Cd 0.359. BEV variant is Cd 0.311.
* the Hyundai KONA ICE is Cd 0.32. BEV variant is Cd 0.29.
* the 2007 Ford Fusion ICE is Cd 0.34. 100% grille-block = Cd0.316.
* the 2016 VW Golf ICE is Cd 0.287. BEV variant is Cd 0.27.
* the KIA Niro ICE is Cd 0.35. BEV variant is Cd 0.35.
* the Spirit of EcoModder, 2014 is Cd 0.2675. With 100% grille-block, Cd 0.2405.
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1) if we're going to talk about cooling drag, how about establishing fixed parameters under which the quanta will be observed and reported.
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2) if electric motors are, say, 90% efficient, and ICE engines approx. 35%, at any given road load, the heat flux to be dissipated across a heat-exchanger would be impacted accordingly. An assumption of like heat transfer coefficients would suggest that, the ICE / BEV cooling systems would require the same proportionality with respect to exchanger frontal areas, flow volumes, and cooling drags.

[aerohead]

Here's a colorized Road Load Horsepower graph of a 'typical' car, circa 1996, from Honda R&D, presented in a JSAE Paper for the 1996 Honda Dream, tandem solar racer.
You'll notice how the load varies with velocity.
We'd want to 'fix' this sort of thing when doing any comparisons.
http://i1271.photobucket.com/albums/...titled7_25.jpg

[AeroMcAeroFace]

Originally Posted by aerohead

* the Chevy Spark ICE is Cd 0.36. BEV variant is Cd 0.325.
* the FIAT 500 Lounge ICE is Cd 0.359. BEV variant is Cd 0.311.
* the Hyundai KONA ICE is Cd 0.32. BEV variant is Cd 0.29.
* the 2007 Ford Fusion ICE is Cd 0.34. 100% grille-block = Cd0.316.
* the 2016 VW Golf ICE is Cd 0.287. BEV variant is Cd 0.27.
* the KIA Niro ICE is Cd 0.35. BEV variant is Cd 0.35.
* the Spirit of EcoModder, 2014 is Cd 0.2675. With 100% grille-block, Cd 0.2405.
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1) if we're going to talk about cooling drag, how about establishing fixed parameters under which the quanta will be observed and reported.
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The parameters are cooling drag as either a proportion/percentage of aerodynamic drag or Cd change. This is ignoring other changes that may occur as a result of becoming an EV.

Comparing ICE and EV variants doesn't help, because it is more than just the cooling that has changed, the gearbox is different, they may use narrower tyres, different rims, there is no fuel tank or exhaust, the battery pack may form an undertray where previously there wasn't one etc.

There is no need to "fix" anything, aerodynamic drag is proportional to speed squared, that is why we have Cd