Earth sleeve

[Mikefromlondon]

These sealed containers are only confusing the engine comparisons where there is no sealed container.

If a pressure is maintained steadily to an exact setting required, and under any given conditions, i.e. regardless of temperature, but within the engine RPM range of Turbo compressor then it can be said to act like a sealed system. Even though the air inside the duct work may be very fast flowing, (dynamic),
(my example of a sealed canister with a certain volume of air, where when you heat it or cool it its densnity is unlikely to change, and of course you said I might be getting mixed up between Mass and density. In this example are they not both the same thing as neither mass nor density can change. Why do cars have Mass Air Flow meters, and why not Air Density meters?

My understanding of Mass and Density is that Mass is the atomic weight of an atom, and density is number of those atoms present in a given volume of space.

 

[EFLImpudence]

It's a bit of a misnomer:

Hot wire sensor (MAF)[edit]
A hot wire mass airflow sensor determines the mass of air flowing into the engine’s air intake system. The theory of operation of the hot wire mass airflow sensor is similar to that of the hot wire anemometer (which determines air velocity). This is achieved by heating a wire suspended in the engine’s air stream, like a toaster wire, with either a constant voltageover the wire or a constant current through the wire. The wire's electrical resistance increases as the wire’s temperature increases, which varies the electrical current flowing through the circuit, according to Ohm's law. When air flows past the wire, the wire cools, decreasing its resistance, which in turn allows more current to flow through the circuit, since the supply voltage is a constant. As more current flows, the wire’s temperature increases until the resistance reaches equilibrium again. The current increase or decrease is proportional to the mass of air flowing past the wire. The integrated electronic circuit converts the proportional measurement into a calibrated signal which is sent to the ECU.

If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow. Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume. (See stoichiometry.)

This sensor sometimes employs a mixture screw, but this screw is fully electronic and uses a variable resistor (potentiometer) instead of an air bypass screw. The screw needs more turns to achieve the desired results. A hot wire burn-off cleaning circuit is employed on some of these sensors. A burn-off relay applies a high current through the platinum hot wire after the vehicle is turned off for a second or so, thereby burning or vaporizing any contaminants that have stuck to the platinum hot wire element.
https://en.wikipedia.org/wiki/Mass_flow_sensor

 

[JohnW2]

These sealed containers are only confusing the engine comparisons where there is no sealed container.

Indeed - and that's really a variant of what I've been saying repeatedly - that we don't know enough about the inner goings-on in this system to be able to mentally model or predict exactly what will happen. Even if we ignored the difficulties of extrapolation from a static to dynamic situation, we don't know what conditions exist in different parts of the system. As you say, it clearly is not equivalent to constant volume ('sealed container') conditions (in which case cooling would not affect density), but probably nor is it equivalent to constant pressure conditions. The truth is presumably somewhere between those extremes, and undoubtedly different at different points in the system.

Having had all this discussion, and done a fair bit of reading, I think I'm probably prepared to back-step a bit and concede that the 'reason(s) for' having an intercooler encompass both the increase in density (which you have been majoring on) and the avoidance of temperatures so high as to produce problems of premature detonation (which I have been concentrating on).

Which of those the "main reason" is probably a question to which there is no universal answer - since it undoubtedly "depends" on circumstances. If the temperature of air coming out of the compressor (with the desired degree of compression) were so high as to present an unmanageable problems of premature detonation (with attendant risk of engine damage, to mention but one thing), then I think that one could argue that avoiding that problem was the "main reason" for installing an intercooler. On the other hand, if the temperature were not so high as to create that problem, then increasing density would probably be the "main reason".

Kind Regards, John

 

[Mikefromlondon]

It's a bit of a misnomer:

Hot wire sensor (MAF)[edit]

If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow. Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume. (See stoichiometry.)

This sensor sometimes employs a mixture screw, but this screw is fully electronic and uses a variable resistor (potentiometer) instead of an air bypass screw. The screw needs more turns to achieve the desired results. A hot wire burn-off cleaning circuit is employed on some of these sensors. A burn-off relay applies a high current through the platinum hot wire after the vehicle is turned off for a second or so, thereby burning or vaporizing any contaminants that have stuck to the platinum hot wire element.
https://en.wikipedia.org/wiki/Mass_flow_sensor

excellent article, reinforces my own thoughts on density must also increase with pressure, but depending on how this pressure is being created, here the volume remains constant (duct work and intercooler space volume) but pressure is being created by turbo pumping or forcing more air (more mass) into the system, but of course not in a sealed jar (static volume) where pressure can also increase by increasing temperature since number of atoms (mass) remains unchanged, i.e. no further topping up of atoms (mass)

So yes we are all right, it depends on lots of factors, and conditions, and changing one factor or conditions also then influences another, and this means constantly varying parameters.

I am also beginning to understand that how lowering temperature can result in increase in density, but only under certain given conditions, and certainly not under all parameters.

A turbo systems is complex, it could be static for a few seconds as well as fully dynamic, or in between depending on the amount of throttle opening, how rapid the cooling occurs, what pressure is the turbo pushing mass of fresh air into the system, how hot it is to start with, are there any turbulence within the duct work and within the intercooler.

so yes the bottom line is there are far more complex goings on than a simple Boyle's law, I am sure intercooler must help in many ways to prevent pre-ignition that can cause detonation which is also known as pinking, or knocking, and help densify air density.

Talking of pinking, in the mid 70s, I use to run my car on heating fuel (paraffin) and it used to pink like hell, but at half the cost of normal regular petrol, it saved me a few bob to spend down my local, to reduce the pinking I had to ****** static ignition timing from a knurled knob on its distributor and disconnect vacuum advance pipe, fun days I called them.

so yes we all now agree that intercooler does both, it increases the air density by cooling compressed air, and lowers the temperature to prevent pre-ignition.

that leaves one other thing we have not talked about and that is What does Amal valve do? I like to hear from you and not google it. Not 10 pages yet come on get your pen out!

 

[EFLImpudence]

Assuming you have spelt it right, I've never heard of it.

 

[Mikefromlondon]

Yes I have spelt it right, so there is something you need to brush up on, I think you will be needing to oogle, I don't know much about it myself and I thought John W2 or you could enlighten me a bit.

 

[Mikefromlondon]

Im sure most can tell i am no electrician but i have been running a few cables etc etc. One question about earth cable, i keep fitting earth sleeves but why does cabling not come with 3 coated cables rather than 2.

I think I will have to apologies to you for going off topic, it wasn't intended but it ended up in a multipage debate, thanks to you, now to answer your honest question, which makes perfect sense why not sleeve the earth conductor and save us all carrying earth sleeving, at times it can be bloody nuisance when you run out of it and many people I have seen revert to not using it at all, and i hate to see those bare unprotected wires, as they themselves can cause shorts by coming in contact with live terminals inside a socket.

But sure we have all discussed already why it may not be insulated with a pvc sheath in green/yellow colours,
one reason i wanted to add was that many electricians use the bare earth wire to strip back the outer insulation layer by pulling it along with a pair of pliers. So may be manufacturer's were trying to make our life a little easy so we don't have to carry knives to slice insulation.

But if you prefer a twin & earth with a factory insulated sleeve (insulation) then you may have to move to Australia, because I think it is a requirement in that piece of land, here http://cjw4817.en.made-in-china.com/product/ioRxIhjlAZVD/China-Twin-Earth-Australia-Wire-4mm.html

 

[Nozzle]

But if you prefer a twin & earth with a factory insulated sleeve (insulation) then you may have to move to Australia, because I think it is a requirement in that piece of land, here http://cjw4817.en.made-in-china.com/product/ioRxIhjlAZVD/China-Twin-Earth-Australia-Wire-4mm.html

I believe DIY electrical work is also illegal there! They like protectionism.

Nozzle

 

[JohnW2]

I believe DIY electrical work is also illegal there! They like protectionism.

Indeed. I gather that members of the public can go on some sort of 1-day course in order to be allowed to attach or change plugs on appliance leads!

Although most of the statistics are difficult/impossible to collect with any accuracy (if at all), I would be very interested to know what (if any) impact the outlawing of electrical DIYing has had on 'safety' (electric shocks, electrocutions, proven 'electrical fires') in Australia - since I have some definite suspicions about what the answer might be!

Kind Regards, John

 

[Nozzle]

And not just electrics, plumbing too! i saw a list of tastks that can be performed, and it is very limiting indeed, you can replace a tap washer but not a tap. I think it's so restrictive as it's better for employment rather than from a strictly safety perspective.

Nozzle

 

[bernardgreen]

I think it's so restrictive as it's better for employment rather than from a strictly safety perspective.

The authorities were not very attentive between 2010 and 2013 as reported here

http://electrical.theiet.org/wiring-matters/53/sub-standard-cables/index.cfm

A major cable recall, affecting up to 40,000 homes and businesses, and costing an estimated A$80 million (£43 million), has hit the headlines in Australia. The distributor is in liquidation, the owner has had criminal charges brought against her and the largest ever taskforce, comprised of 21 consumer agencies and regulatory bodies, has been assembled. These organisations have come together to source, destroy and replace around 2,500 miles of potentially hazardous cable across five states before it becomes a fire or electrocution threat.

 

[Mikefromlondon]

Really speaking these days almost everything from a toaster to breadmaker is manufactured in China to standards setr by the west and using plants and machinery provided by the west, so when chines goods fail, blame not china but our greedy importers because they want to maximise their profit and will ask chinese manufacturers to do short cuts, and customer is always a boss, they will do what they are asked to do. Name a single consumer thing that is made in Australia and or UK or USA, even union Jack is made in china. At best we are only good at making roast beef and yorkshire pudding.

Cables do become brittle if they have too much fire retardant additives. That would have been Australian requirement in the first place.

Also temperature range of a cable is crucial to its longevity, we tend to go for cables that perform around high temperatures but when we are hit with sub zero temperatures these cables can become brittle and get damaged.
https://www.anixter.com/en_uk/resou...wire-and-cable-cold-weather-temp-ratings.html