Mega Q & A: Warm up a modern car, new car shortage, EVs & Tesla

Answering your questions, responding to your feedback on everything from warming up modern cars, the car supply shortage, welding and metalwork, and electric vehicles…

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Here are the answers to a great many questions asked by people like you in the comments section of my recent reports:

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Is it a good idea to let the engine run for a few minutes after a cold start before driving? - John Vender

The obsession with warming cars up typically harks back to the 80s, when we didn't have very interesting engines because technology, compared with today, was not as good.

Three core issues made warming up a car popular in the 80s: drivability, lubrication and metallurgy. 

With metallurgy, all the parts in the engine wouldn’t fit together in the context of going from dead cold to operating temperature.

In the 80s, most cars had carburetors and analog control of things like air-fuel ratios, ignition timing, spark advance and valve timing - all of that engine management stuff.

We didn’t have high speed digital control of the combustion process throughout the warming up period which cars have today. 

From a drivability point of view an engine is basically good to go the moment it catches fire. If it's turning and burning, a modern engine is ready to drive thanks largely to direct injection and much better internal plumbing.

Lubrication, well, that's changed a lot too. Back in the 80s - four decades ago - mineral oils were not as good as today's synthetic oils. The big party trick for synthetic oils, apart from their longer life, is their ability to maintain an acceptable viscosity through a great range of operating temperatures. Meaning, from dead cold the oil remains pretty runny and easy to pump right up into the top of the engine by the oil pump.

Then, at high temperatures, it doesn't thin out too much - it remains thick enough to do an effective job lubricating all those mechanical parts.

Viscosity has been extended by chemical engineering, and I'd suggest you can crank your engine, put your seatbelt on, close the door, check the mirrors, and drive down your driveway.

That engine is fully pressurized from the point of view of being lubricated.

As for metallurgy, back in the 80s we had lower emissions standards and there was less imperatives on carmakers to get the engine up to its operating temperature quickly, which would be where it's most efficient and doesn't emit too many noxious chemicals like unburned hydrocarbons, when it's cold.

Today we've got much better control of the process and the warm-up happens much quicker; the whole thing is designed to reach its operating temperature quicker, more engine components are made of aluminium which is a much better thermal conductor than cast iron, for example. 

Current technology has improved things dramatically, but also, it’s worth noting -  it's a really really bad

idea to race off before the engine is at its normal operating temperature. 

If you start the engine, idle down the driveway, then drive gently for a total of 30 seconds to one minute, that's as good as warming the car up for several minutes in the 80s.

oh man you'll be a fossil in 5 years time, 3 years ago Tesla had one production factory, now they have 5 and more rolling out across the world, good luck with your combustion engines. - Vin Hili

It’s often nice to kick off with the things we agree on.

However, one of the most insufferable things about this transitional phase we're in now, where we've got established internal combustion over here and we've got electric vehicles and hydrogen over here is the people in the different camps who treat it like a freaking religion.

One of the core tenets of religion obviously is faith like you just have to believe right and one of the things you have to believe is that every other religion is wrong and that's exactly how the dynamics work between hydrogen and electric vehicles and internal combustion.

But in reality, for decades to come, there is a place for all three. 

Now the difference between me and some freaking EV zealot is I only go by the facts. Let's not forget I drove a Kona EV for 12 months and loved it and I didn't miss going to a fuel station once, so I get the EV thing.

They're pleasant to drive and they do a few jobs really well and in some respects they're better than internal combustion and in others they're not.

You've got to be realistic, meaning, in touch with the facts especially if you want to deal with the big problem which is the climate emergency.

Now here in Australia, we are still approving new coal mines, we are still exporting an enormous amount of coal equivalent to our national greenhouse onshore emissions. This is out of step with the desire of most people in the electorate and certainly most people in the developed world.

There's a surge of opinion among ambient humanity that we need to solve this problem and our current actions with coal is not the solution. Nor is some sort of grandiose promise from our useless prime minister about 1.7 million evs on the road by 2030. That's ridiculous.

The foundations are not in place to make that happen and at best in terms of the climate emergency it's a freaking band-aid.

You've got to be realistic if you want to make a change. Saying, ‘I'm going to buy an EV because I’m concerned about air quality in our cities, big tick, that works.

If you said ‘I’m concerned about national energy security and, in particular, our vulnerability to the supply of liquid fuels, so I'm buying an EV,’ that is a strategic problem for our national

security and if you do that you're taking a little bit of that dependency on foreign oil away.

Buying an EV thinking ‘it's the only thing I see that can help the climate emergency,’ I'd say a divorce from coal and being realistic, using facts because that's the only way humanity can hope to solve any problem.

Most of this car shortage hype is so manufacturers can create FOMO and gouge more money from you. Don't believe it in most cases. If you go in and they pull this start walking out and you may find a car magically appear! Lol - J J

I know conspiracy theories are a popular pastime, but I'll give you a really pragmatic reason why that cannot be the case.

There's 50 or 60 different car brands, depending on how you carve them up, globally. Certainly, the most important ones could be encapsulated in a list 50 or 60 long okay.

They all hate each other. There's nothing Mercedes-Benz hates more than Volkswagen, and there's nothing Toyota hates more than Mazda and there's nothing more that Mazda hates  than Hyundai and Kia.

There's so much multilateral hatred that these people could not all sit down in a room and engage in a massive global conspiracy where they all kept pumping out cars in secret during a pandemic and faked a shortage with cars just stacking up 10 high at the dock, only for you to walk in and call their bluff. They can’t just magic one up.

That is unrealistic on so many levels, and also, inconveniently, the car industry just wants to sell more.

Mass production is a game where you get that factory ideally cranking out three shifts a day

as fast as it can crank just making cars endlessly because that makes the production line efficient; it lowers the per unit cost, thanks to economies of scale.

Then you've got these rabid sales directors who just get out the whip and they lash - there's a cascade of ass kicking to sell. That's how the car industry works.

For them to engage in an artificial inversion of this process which is just philosophically abhorrent to them at every level, it's just flat out ridiculous. It's up there with flat-earthing and anti-vaxxing, frankly.

Please tell me why I need to get rid of the mill scale on my rolled steel - Paul Thompson

I did a report on metallurgy and abrasives, namely, which different abrasives go with which kind of metallurgical applications. You can check that out here >>

Now, mill scale is this black shiny crap on the outside typically of every piece of hot rolled steel you ever buy and it's inconvenient because it's glassy, hard, and difficult to cut. It's hell on machine cutters, milling face cutters etc.

If you've just got to take a shave off something that's been hot rolled that's a pain in the ass, it's kind of hard to drill through as well and it's responsible for a fair bit of wear and tear on drills.

So getting rid of it makes sense from time to time. It's also kind of flaky, so cosmetically, if you paint it, it's going to look rough and it's porous, at least at the junction between the mill scale and the bare metal. The rust is also porous and that allows water and oxygen to  combine and foment more rust, which they probably don't want in the finished product.

Obviously, if you're going to do anything involving elbow grease like filing or cutting with a hacksaw or anything of that nature, or you're going to run a milling face cutter over the

top of a piece of hot rolled bar or rod or something.

This stuff is it's just the scale and it's really hard on the cutting edges, which means you're going to have more wear and tear on everything that you try and cut, sand or grind.

This stuff with it also loads up some adhesives like zirconium, so you don't want that. If, for example, you've got two 250mm wide pieces of steel channel, which I'm turning into a fabrication surface that's flat in two directions, I want to clamp to it and weld to it. If you want to attach the ground cable for your welder, it doesn't really conduct that well covered in mill scale, because you lose a fair bit of energy through the mill scale, so it's harder to get a solid electrical contact.

Then when you are welding, in particular if you're tig welding using tungsten inert gas, it's entirely intolerant of impurities such as mill scale - properly  hates it and your tig welds look crap.

Also, if you're doing what most people call mig welding, which is really gas shielded arc welding metal with inert gas, it prefers to be reasonably free of impurities like mill scale as well.

You want to get rid of it for both kinds of welding, and even for the other two kinds of welding like flux cored arc welding (which would be mig without the gas) and also just regular stick welding (manual metal arc welding), you always get a better result if you don't have impurities to weld through.

For all these reasons, you want to remove mill scale.

Pro Tip: If you've got a manageable piece of steel, don't bother grinding it off at all. Just go to the local hardware store or supermarket and get yourself some normal white vinegar, immerse the steel in it for 24 hours and then just scrub the mill scale away with a normal scrubbing brush. 

You could also get stronger acid from the hardware store, like muriatic acid, but if you do that, you have to be pretty careful with it because it is possible to hurt yourself with the vapours and or if you splash it into your eyes or get it on your hands. Bad news. Vinegar is much safer.

Mill scale is a bastard, but you have to deal with it if you're going to deal with any kind of subsequent fabrication operation.

While you’re on the welding subject, check out my Ultimate auto-darkening welding helmet DIY modification >>

I'm a blacksmith/farrier and we end up with a ton of scale on a horseshoe. At farrier competitions we are forced to be luddites and use a hot rasp, but in the field we’ll use either a linisher or an angle grinder. We generally use Zirc, but going to have a bit of a play with some of the others. - WA & VH Lawrence

When training to be an engineer, for the first few years they shoved us into the workshops in heavy industry in the railways. I always wanted to work in the blacksmith shop at Redford, it was just awesome.

Every time I walked through it, I wanted to have a crack and never got the chance, so half your luck, doing that sort of work.

Now, zirconium is really short for zirconium oxide; they call it ‘zirconia’ or just ‘zerk’. It's this bluey green stuff on a linisher belt. It's a particular kind of oxide and it's got some interesting properties like it self sharpens, and that's why it lasts a little bit longer than the brown stuff which is aluminium oxide.

Unfortunately, I was having a crack with a zerk flap wheel recently on a piece of metal with just a little bit of mill scale on it, and the result was it loaded up on the wheel - that wheel is now next-to-useless.

So zirconia is not the ideal abrasive to use for anything with mill scale on it from your recent

blacksmithing or steel merchant when you're buying the hot roll stuff.

You’re much better off going with aluminium oxide or even silicon carbide.

I’ve worked as metal fabricator most of my working life and never considered using a masonry grinding disc for mill scale, I’ll certainly be giving it a go in future.  TONY D

I urge you to have a crack with silicon carbide because it is much more effective, especially if you've got a lot of mill scale to deal with in the one project.

Brown is aluminium oxide, the greeny blue is zirconia, and the red is ceramic (not so effective with mill scale) but silicon carbide is really good because the abrasive dynamics are just different. It's like having a million really sharp knives having a crack at the problem and the Pro Tip here is that silicon carbide is common with masonry grinding wheels and they work just fine on mill scale.

But when you start with your silicon carbide wheel, compared with your masonry grinding wheel, brand new there's a really sharp 90 degree edge on the wheel, obviously. But what you really want for dealing with mill scale is a used edge, which has a radius that's been worn on the edge. I use this rounded edge on both of the steel beams that I'm working on here on the fabrication surface. What you get is this nice rounded surface.

When you get a new wheel and you attack the mill scale with it, it's really savage on the underlying steel so my strong advice would be to find a bit of old concrete (probably not the local police station steps) or something, and just round the wheel over until you get this rounded profile, ideal for grinding off mill scale.

When you've got 1.7 metres or steel to process, it’s not amenable to being placed in a bucket and soaked in vinegar overnight.

Use the masonry disc to deal with the mill scale, go light with the grinder, then clean up the underlying steel with a 40 grit zerk flat wheel, and if you do both of those processes together you know to do silicon carbide first and then your zerk dressing wheel (40 grit’s fine for most ghetto engineering applications) depending on whether you're going to paint it or not; 40 grit works.

I'd also suggest silicon carbide is dangerous to be breathing. Really bad. Silicon carbide is not one of those substances that you do not want to have lungs full of because the phrase “million microscopic knives” might indicate how nasty it is. 

Go outside and try to do it on a day with ambient breeze, stand upright most of the time, wear a full face visor and a p2 mask, and hopefully that keeps you reasonably insulated from whatever evil nature lies with those silicone carbide particles. 

Pro Tip: When you experiment with silicon carbide on mill scale, don’t do it in a closed up garage with no breathing protection - that's a little bit risque.

As an engineer I’d imagine you’d know that there’s no such grade as “mild steel”. A cert 4 teacher I once had advised our class never to use that term in an exam because it’s not listed in any standards and you’ll lose marks if you do. I’m guessing you use the term to describe low carbon steel? - Tony D

Agreed, there's no such thing in terms of detailed design as mild steel but context is everything. If you're at TAFE or university doing a project that involves the design of a beam to hold a bridge up over the river, and you tell the examiner that you're going to build it out of mild steel then you should expect to fail.

But, there's a category of steel that I would colloquially refer to as ‘mild steel’ and it would be these kinds of shapes, like big channels and two big beams that are holding the fat cave up over my head right now. I generally refer to them as structural grade mild steel which would be minimum sort of yield stress of 250 megapascals. 

And if you want to know what a megapascal is, it's one newton of force for every square millimeter of area. So, 250 megapascals would be 250 newtons of force for one square millimeter of area, which would be roughly 25 kilos of force for every square millimeter before it yields. This means before the deformation under load becomes permanent, mild steel could be broadly categorized as being anything up to about 450 mpa.

There's many colloquialisms for steel, like ‘tool steel’ which is used for something like a cold chisel might, there’s ‘high speed steel’ which is used in a twist drill, for example.

There are many different grades of those steels, like ‘low carb’ and ‘mild’ steels. The more you drill down into it the more nuance there is.

Even with cars, they use different grades of steel in the body shells these days. The gold standard for high strength is so-called gigapascal steel, which is 1000 megapascals. Every time you go to a marketing presentation for a new car launch, they talk about how much

hot forming they're doing on the bodies, which is essentially because these tougher steels in that gigapascal range are less amenable to being cold formed. This mean in order to use them you have to heat them up and get them into shape quickly, and then let them cool down before being welded into the body structure at typically high stress points.

The terminology depends on who you're conversing with because when someone’s talking about regular house steel beams for fabrication, to me they're just made out of mild steel and we're never going to get close to the yield stress.

I know what they're made out of and hopefully, now, so do you.

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QUESTIONS ANSWERED PART II

If colour makes no difference ... why do they always tell you to paint the inside of rolled plastic pipe water heaters black? - Pablo Rages

In my recent photovoltaics report, during the side issue of colour, I did not say it doesn't make any difference when it's a black car versus a white car in the sun in the middle of summer.

I said it makes a slight difference, claiming about one or two percent absolute temperature change, but really the difference of colour in terms of how hot a car gets inside is grossly

overstated by most people. It's just people who don't understand the relationship between radiation and thermal effects make this assumption based on cognitive bias that has built up over time.

When you're talking about a heater, up there on the roof, which is really just black polyethylene pipe sitting in the sun, I'd suggest that the colour of the pipe doesn't make all that much difference either. But what would make a pretty big difference is its reflectivity.

So, if it’s shiny, it might be a good idea to scuff it back a little bit with some 400 grit wet and dry sandpaper, because the more reflectivity you remove, the more radiation is going to be absorbed by the material.

A matte coloured car might be much hotter than a shiny glossy car, irrespective of the colour - that would be an interesting experiment to run.

The other thing about water heaters on the roof, the kind that absorb solar radiation into the tubes to heat up the water, one of the principal means of heat loss is forced convection, like when the wind blows. It’ll  take a lot of heat away from the heater, so a way of making that installation more thermally efficient would be to put it in a box that deflects the wind, and cover it with a highly transparent sheet of glass that was also tough enough to withstand

things hitting it in the environment. 

Another example of how colour really doesn't matter is people using black paint on their intercooler to improve its thermal efficiency and get greater cooling out of it. That's not going to work.

The evidence for this is when you go and look at every modern car manufactured today, statistically, they will all have two or three heat exchangers inside the grille. You'll see a condenser for the air conditioner, which is designed to reject heat during the condensation phase when the working fluid turns from a gas into a liquid. 

Then you'll see a heat exchanger for the engine coolant, poorly termed the ‘radiator’ even though they don't really radiate.

You might even see an intercooler which is typically an air-to-air type cooler for the inlet air charge, because going through a turbocharger typically heats the air up a lot. 

Those three heat exchangers are bare aluminium. If the car industry could save a tiny bit of expensive aluminium on each car, just by painting it black, they would do that in a heartbeat because 10 grams here and 10 grams there from three different heat exchangers is 30 grams times 1 million cars is 30 million grams which is 30,000 kilograms - 30 tons of aluminium saved. Saving 10 grams is not an insubstantial saving.

But they're not black because black won't help.

In fact, the paint would only be an effective layer of protective insulation between the heat exchanger and the air which it’s trying to convect though.

You've gotta send this video to Rob Stokes the NSW Planning Minister. He and his boffins have decided to ban dark coloured roofs in Sydney as they state they contribute to heating up the planet and contribute to climate change. I kid you not. Seriously, who advises these people? - Far Ken

Rob Stokes’ first effort at abject comedy, in my view, was found in his comments recently on electric vehicles >>

His quaint hypothesis on electric vehicles was just another kind of enslavement, as I understood. Although, I think he did use that word ‘enslavement’.

He suggested it’s just like internal combustion only a different slave master. He’s so far out of touch with reality, in my view, it's not funny.  

It’s particularly galling in the case of somebody who's a planning minister, responsible for planning the future urban spaces for five million people here in New South Wales, unacceptably so, in my personal opinion. 

I had a little bit of a look at Mr Stokes, who is just what we need in politics, I think you’d agree - a lawyer with a diploma in biblical studies. Who better qualified to do all of that planning decision making? 

When it comes to black and white roofs, if Mr Stokes believes that this kind of thing has any hope of making any tangible difference whatsoever, to climate change or quality of urban whatever, in our cities… he's off with the fairies and out of touch with the physics, again.

Hi John can you please confirm that this unit has a 40 amp hour lithium battery? Thanks - Bob the Colorado

Check out my battery deep dive tech report here >> for context to this question.

But this question is about how it's kind of farcical or at least it doesn't make rational sense to use ‘amp hours’ when you're comparing batteries at different voltages.

The only thing that matters is ‘Watt-hours’ because watt-hours are the amount of on-board energy.

The Bluetti AC200P is a 2000 watt-hour battery and if you're running it exclusively at 240 volts that means it's about 8.5 amp-hours. If you're outputting 12 volts, it's about 160 amp-hours.

Of course, these ratings ‘amp hours’ and ‘watt hours’, they're subject to the discharge limitations of the battery and the maximum draw rates and so on. There's not infinite linearity of 2000 watt hours. You can't have 4000 watts for 30 minutes, for example, because that will trip the current protection inside the device; you just can't draw it that fast. With these kinds of batteries you get to a certain level and they might still hypothetically be some energy inside, them it's just really locked away and not accessible.

But generally, I just go with the manufacturer's claims because I don't really have a means of testing what amount of energy remains inside the battery - I’m a mechanical engineer not an electrical engineer.

I didn't catch the IP rating of this thing (if you mentioned it?), and how would it stand up strapped in the back of the ute on the way to Dingo Piss Creek with Tiffany? Keep up the good work. - Brambo Keff 

I reported  recently on the Bluetti AC200P: it's essentially a 2000 watt hour lithium-ion battery with an inverter, packaged up inside the box. 

It’s got numerous outputs, you've got wireless phone charging, 240-volt wall outlet, you've got a 12-volt outlet, a USB-A out and USB-C out.

You can use all of these outputs simultaneously, subject to not overloading the maximum discharge capacity of the battery.

If you're looking for this kind of portable power solution, check out my Bluetti review here >>

But in relation to the IPX rating for environmental waterproofing, it's quite an open device, with a fan inlet/outlet, it's analog on the other side, you've got flow-through ventilation presumably through the inverter, and I suspect the whole battery charging and discharging thing has big fat heat sink on it as well.

When I look in the manual, there's no IPX rating for this device and in fact the official advice in the manual is ‘keep it out of the rain and don't use it in high humidity over 90 percent’.

So, I don't know what the official IPX rating for “don't get it wet” is, but I’d strongly urge you: don't get it wet.

It's a sensitive sort of electronic device which has been ruggedized for use outdoors, obviously, but it's probably not compatible with operational deployment with the Frogmen.

How the hell do you reach the blue sorting boxes? Bugged me the entire video :)

- William

How do you get to those blue storage bins on the wall?

- Clyde Wood

I just use a step ladder. The reason for having the boxes up high, which is kind of why I'm fielding these questions is accessibility.

Let's talk about workshop design for a moment. The important thing about workshops is accessibility of the things you need and use in a primary, secondary and tertiary priority.

All of the things that you need frequently, like in my case, a dead blow hammer or a center punch or a ball peen hammer, some screwdrivers, the pliers, a file - whatever - that's all got to be primarily accessible.

The most common power tools, a drill, a driver, an angle grinder, they've all got to be quickly on-hand in order to get going.

Then there's secondary accessibility, which is like the blue boxes; I don't always need an M12 x 50 socket head cap screw, but it is just up there if needed. All that’s required is a step ladder off the wall to grab it. 

Lastly, when rare-use tools are needed, they’re packed away all over the place in various toolboxes and everything's got a place. Things that get used least often are the least accessible and the things used most often are the most accessible.

The main reason for having all the primary stuff up on the wall and accessible now is you can see if something's missing and you don't lose 10 minutes here, five minutes there, or 15 minutes there failing to find something. I've spent so much of my life looking for tools that it's so hateful and so inefficient and so freaking wasteful of one's only remaining resource which is time.

We only live for about 4000 weeks in our lifetime, so it would be good to spend as little of that time as possible trying to find what I was looking for.

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