Top three worst names ever in automotive engineering
3. COOLANT
The coolant in your radiator - the red stuff, the green stuff … it’s not there to assist the cooling. In fact, water on its own would do a better job just cooling your engine. The most common so-called coolant is ethylene glycol - the green stuff. (The green is fake - it’s just a dye.)
Ethylene glycol has lots of interesting properties, but carrying heat from your engine is not, frankly, one of them. It’s only about half as good as water at doing that.
Water is the commonest heavy hitter of heat transport. A technically cognizant person (every mechanical engineer on the planet) knows the specific heat capacity of water: it takes 4.18 kilojoules of energy to heat one kilo of water by just one degree C.
Allow me to translate for the non-cognoscenti: water is effing hard to heat up. It takes a shitload of heat to warm water up just a bit. Therefore, it’s the perfect fluid for moving heat away from something (like a hot engine) and into a radiator, where that heat can be rejected into the air.
When you mix ethylene glycol with water about 50:50 you actually reduce the ability of the liquid blend to carry heat away from the engine by about 25 per cent. The main reason for adding it is to drop the freezing point and raise the boiling point.
That same 50:50 ethylene glycol and water mix freezes at about -37 degrees C - and it’s really good if the water in the cooling system doesn’t freeze - because it expands when it does and that often breaks expensive components from within, as well as rendering the car undriveable. So that’s bad.
As a side benefit, together with pressurising the cooling system, a 50:50 mix of ethylene glycol in water, together with 15 PSI of pressurisation raises the boiling point - to almost 130 degrees C. It’s kinda bad if the coolant boils in the engine - it leads to a generalised class of failures fairly categorised as ‘catastrophic’.
The other chemicals in the so-called coolant also have nothing whatever to do with cooling - it’s all about the lubrication (of the water pump) plus corrosion inhibitors for the engine.
2. RADIATOR
I know: What’s he got against cooling systems? Nothing. I love me a good heat exchanger. Everything from cars to nuclear power stations use them. It’s just that radiators do not cool your engine by radiating. They’d be different if that’s how they really worked.
Heat transfer for dummies. Heat is like water - it flows. Water flows from high to low heights. Heat flows from high temperature to low temperature.
There are three mechanisms for for that flow: conduction, convection and radiation. Conduction is mainly about heat transfer in solids.
Convection is all about losing heat into a fluid (pro tip: fluids are liquids and gasses).
Radiation is like: You’re sitting in front of a fire. It feels warm because: Radiation.
When you look at a so-called radiator, you can tell instantly that it’s not designed to radiate - if you’re scientifically literate. For starters - it’s up the pointy end of the car, and they hacked a big hole in the front of it to facilitate airflow. That’s a big hint.
Anything involving airflow and cooling is about convection. If radiators actually rejected sufficient heat by radiating, they wouldn’t need the big hole in the front of the car. The sun doesn’t need any air to radiate its heat 150 million kilometres to earth.
If so-called radiators actually radiated effectively, they would not need fans (the fans are only there to maintain airflow when you stop in traffic). They serve no other purpose.
1. SHOCK ABSORBER
If ‘Shock Absorber’ is not the worst name in all of automotive engineering, I don’t know what is. You think about it - you drive over a pothole: the suspension droops into the hole, then the leading edge of the wheel and tyre crash into the ridge on the far side of the pothole.
The tyre compresses, then so does the spring. These are the devices that are absorbing the shock. If it’s a big pothole and you hit it hard enough, the suspension will hit the bump stop and the rubber pad there will also attempt to absorb the shock.
If it’s a really big pothole and you hit it sufficiently hard, you might also bend or break the wheel - that’ll help absorb the shock. (But it’s probably not that helpful overall…)
The one thing that does not help absorb the shock is a so-called shock absorber (which is really a vibration damper - hence the more correct name: the damper).
So-called shock absorbers are really there to smooth out the subsequent unhelpfully bouncy response of the spring - they don’t really do very much primary absorption of shocks.
The salient difference between springs and dampers: Springs push back with a force that’s related to their displacement - dumbing this right down: how hard they push is based on how far they’re compressed or how far they’re extended.
