The real 50% of a fuel tank?

[clf]

What would benefit of the cooler behind offside rear wheel?

[HarryM1BYT]

Originally Posted by clf

What would benefit of the cooler behind offside rear wheel?

Sorry, I don't understand what you are asking?

[MG Tom]

Originally Posted by clf

What would benefit of the cooler behind offside rear wheel?

To cool the fuel before it is returned to the tank!

[T-Cut]

How do variations in tyre circumference fit into the ECU's reckoning of fuel consumption and range?

TC

[HarryM1BYT]

Originally Posted by T-Cut

How do variations in tyre circumference fit into the ECU's reckoning of fuel consumption and range?

TC

Well, ignoring the fact that the mpg calculation can be user adjusted, they don't.

Its idea of a measured mile will change slightly, depending on the circumference, but I doubt any standard options will make a noticeable difference.

[clf]

Originally Posted by HarryM1BYT

Sorry, I don't understand what you are asking?

sorry my fault, quick fat fingers typing. Should have read, What would be the benefit of the cooler?

MG Tom has answered that

Why I asked is, HarryM1BYT, you said diesels purposely warm the fuel to make it free flowing. That makes sense, but having a radiator to cool the fuel didnt make sense lol. Cooling it going back to the tank, does make sense though, if maybe a little over engineered perhaps?

I mean, how much fuel is actually needed to be returned to the tank. With so many ECU's I would have thought the pumps would only have delivered a continual required amount, with perhaps a little excess for bursts, then using the excess as a buffer ( a bit like decent CD players). I do understand when switched off, there would be a need to return fuel to the tank, but how much would that return be, if there is a need for a small radiator.

[HarryM1BYT]

Originally Posted by clf

sorry my fault, quick fat fingers typing. Should have read, What would be the benefit of the cooler?

MG Tom has answered that

Why I asked is, HarryM1BYT, you said diesels purposely warm the fuel to make it free flowing. That makes sense, but having a radiator to cool the fuel didnt make sense lol. Cooling it going back to the tank, does make sense though, if maybe a little over engineered perhaps?

I mean, how much fuel is actually needed to be returned to the tank. With so many ECU's I would have thought the pumps would only have delivered a continual required amount, with perhaps a little excess for bursts, then using the excess as a buffer ( a bit like decent CD players). I do understand when switched off, there would be a need to return fuel to the tank, but how much would that return be, if there is a need for a small radiator.

The two electric pumps deliver much more fuel than is needed by the engine at maximum consumption, as does the HP mechanical pump. The delivery is constant, with the HP pumps action imparting a lot of heat and pressure into the fuel, before it is then fed to the injectors.

The surplus hot fuel not used by the injectors, is then allowed to return to the tank under very little pressure, via the cooler unit. Whether it needs to be cooled or not, is determined by a thermostat, similar to the coolant thermostat. If the diesel in the tank gets too hot, the plastic tank could be damaged, too cool and it will not flow so easily so the stat/ cooler, keeps it (once up to temperature) at a steady temperature.

Flow and return to the tank has been standard on both petrol and diesel cars for some years. Slightly more complex than just a flow, but the twin pipe system avoids the need for pumps which stop and start, like the unreliable SU pump.

[Mike Noc]

Originally Posted by clf

sorry my fault, quick fat fingers typing. Should have read, What would be the benefit of the cooler?

MG Tom has answered that

Why I asked is, HarryM1BYT, you said diesels purposely warm the fuel to make it free flowing. That makes sense, but having a radiator to cool the fuel didnt make sense lol. Cooling it going back to the tank, does make sense though, if maybe a little over engineered perhaps?

I mean, how much fuel is actually needed to be returned to the tank.

When the fuel is cold it doesn't return to the tank but recirculates around the LP circuit, with the losses being topped up by the ITP.

This allows the fuel being supplied to the HP pump to warm up. When the temperature of the returning fuel reaches 76C the thermostat opens and then regulates the fuel temperature.

There are a few sketches of the circuit here:

http://www.the75andztclub.co.uk/foru...d.php?t=172055

[HarryM1BYT]

Originally Posted by Mike Noc

When the fuel is cold it doesn't return to the tank but recirculates around the LP circuit, with the losses being topped up by the ITP.

This allows the fuel being supplied to the HP pump to warm up. When the temperature of the returning fuel reaches 76C the thermostat opens and then regulates the fuel temperature.

There are a few sketches of the circuit here:

http://www.the75andztclub.co.uk/foru...d.php?t=172055

That is an over simplified diagram and includes none of the complexity in the tank. T-cut's diagram is better, but naturally even more complex.

My understanding is that there is always some returned fuel going back to the tank and that the cooler is there to prevent the fuel in the tank getting too hot.

[Mike Noc]

Yes it doesn't show either the plumbing in the tank or the tank venting arrangements, but what it does show isn't simplified and is an accurate description of the rest of the pipework because it was traced out from what is fitted to the car, as can be seen here:

[IMG][/IMG]

I've mentioned in the past to TC the diagram in his book isn't an accurate flow diagram of what you see when you look in the tank. When I get some spare time I'll have the scrapper tank apart and trace the pipework out.

As for there always being fuel returning to the tank, apart from a small amount of fuel getting past the restriction in the 5 port valve, when the thermostat is shut there isn't a direct path back to the tank.