I Know Nothing About Car Systems

[rmay635703]

Originally Posted by jeff88

Any reason why I couldn't use propylene glycol instead of EG? It doesn't have as low of a freezing point, but I don't really have to worry about that in this weather! Is there another reason why I wouldn't want to use it?

Also as a side note, why do we not use oil as a coolant? (I know that the engine oil does help with cooling, but I'm not talking about that). Couldn't one use a really thin, maybe 0w-10, oil in a coolant loop? I would think (and read) oil is a better vehicle for heat pick-up and removal.

propylene glycol is the ORIGINAL antifreeze and is found in coolwhip.

here at the big defense company we use it in all of our "artic" kit trucks, comes in a nice purple color.

its also safer and much more expensive (for reasons I can't explain)

[jeff88]

Originally Posted by rmay635703

its also safer and much more expensive (for reasons I can't explain)

I originally asked the question just because it was a random thought, but after everybody's answers and some research, I really like the idea of using PG, because of it's non-hazardous properties; to me it's that much more eco-friendly you're making your vehicle by using it. I would definitely look into finding this at a decent price if/when I ever flush the radiator (another maintenance project, another day).

I looked on Amazon for PG without any filters and it is really amazing how many different products it is used for. I think one of the reasons why it is so expensive is that it is used in cosmetics. Cosmetics is a VERY large industry and just like clothes or hand bags or any other female-buying dominated industry, prices go up. (That's not a knock on anybody or anything, just a business axiom.) What needs to happen, and I have no idea how to do this, is they need some sort of "de-natured" PG, like they did with de-natured alcohol to avoid alcohol taxes (and having people drink it).

[Occasionally6]

Water is even better as a coolant if you can avoid it freezing and prevent corrosion.

I think Toyota's use a proprietary coolant from the factory. It's not compatible with some other coolants so flush well before swapping in something else. If you don't, you can get a mud like sediment in the cooling system if the old and new coolants react.

R134a won't work very well as a coolant in an engine cooling system because:

It can only exist as a gas at the sort of temperatures found there i.e. it's beyond its critical temperature and pressure.

The pressures would be very high, higher than in a typical car A/C system, because that's related to (the much higher) temperature.

If you can't use the change of phase (liquid to gas) to absorb heat, water and EG and PEG are better at absorbing heat anyway.

Normally, only liquid coolant is used but VW (for one) investigated using a vapour phase system where water based coolant was allowed to evaporate. That meant less coolant could be used, so less weight and faster warm up, and a smaller heat exchanger (radiator). I gather it was tricky to arrange the evaporation rate and heat transfer inside the engine.

"Air cooled" engines are in fact substantially oil cooled, as can be internal parts like pistons. One advantage is that oil will work at temperatures that would cause a water based coolant to boil. Otherwise, water is still a better coolant.

Maybe look at concepts like: specific heat, latent heat of evaporation, critical temperature and boiling point, particularly as it relates to pressure, for a broader view.

[jeff88]

I've never really thought about this until today. When the wheels of your car stop turning, how does the engine keep running? I would think with your brakes applied, all the moving parts would fight and fight to continue to move until finally they all stopped along with the wheels. But obviously they don't, so what separates the engine from the wheels and keeps the engine going? The transmission? The differential? Something else? I tried doing a Google search and only came up with problems/repairs.

[some_other_dave]

If you have a manual-transmission car, you already know the answer: The clutch does--you have to push the pedal in so the engine and transmission are no longer connected together.

Automatic transmissions have a liquid connection between the engine and transmission: The torque converter. It's a little like having a fan that blows air at another fan, and the air turns the second fan's blades. That's a vast oversimplification of this one aspect of the torque converter's function, but hopefully it gives you the idea.

With an automatic, there is no solid connection between the engine and the transmission. (Though most cars now have "lockup torque converters" that do make a solid connection, that generally only happens at higher speeds. At low speeds, there is no solid connection.)

Here is lots and lots of reading for you: HowStuffWorks "How Automobiles Work"

For the transmission, see: HowStuffWorks "How Automatic Transmissions Work"

-soD

[jeff88]

Thanks soD, I've actually read those articles before, but they were good refreshers. I didn't realize (I guess I missed that part of the article) the TC is for this purpose. I thought it was for the multiplication of the torque when the engine and transmission speeds are different. Good to know that there are multiple reasons for the TC.

Instead of using a TC, could one use a "smart" clutch hooked into the brake pedal. It wouldn't latch when the car is at speed and the brakes are applied, but if the wheels are stopped (or really close to), then the clutch is applied and the break in the system happens. Or maybe you wouldn't need any of that. Anytime the brake is applied, it would detach the engine/transmission and as soon as you let off the brake (before you press the gas again), the clutch would re-engage the system.

How does a CVT provide a separation between wheels and engine? I've read they do not have a TC like autos, but that they do have a 'clutch pack'.

[some_other_dave]

Not sure on the CVTs.

The stuff you are describing with the automated clutch is something like how the dual-clutch transmissions (and some earlier single-clutch designs) work. They have a clutch (or two), but it is operated automatically.

-soD

[Occasionally6]

The variations of CVT that I can recall how it is done (at least sort of) are DAF and snowmobiles, which use a centrifugal clutch to engage the drive. The other - Nissan? or Ford/FIAT? - which uses an electromagnetic powder that locks solid when an electric current passes through it to connect engine and trans. together.

At a guess, some may use a conventional torque converter, probably with a lock up clutch or maybe just the clutch part like the internal clutches in an epicyclic transmission.

[wdb]

Just to confuse things thoroughly: I drove a Volkswagen in the late 1960's that had an "Automatic Stick Shift"; it actually had a torque converter *and* a clutch (electronically operated, no clutch pedal).

[bestclimb]

Originally Posted by jeff88

...
Also as a side note, why do we not use oil as a coolant? (I know that the engine oil does help with cooling, but I'm not talking about that). Couldn't one use a really thin, maybe 0w-10, oil in a coolant loop? I would think (and read) oil is a better vehicle for heat pick-up and removal.

If it says air cooled on the box you can bet there is some oil cooling going on.