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How much in your tank.

Mean Green

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I have recently converted the RR to LPG and have an 80L tank fitted in the boot. I understand that I will only get about 85% full for expansion. By my calculations 85% is 68L. However, the most that I have been able to get in is 57L. And that is after running the car until the began to stutter before filling so I assume it is effectively empty.

So how much do you get in?

Are there differeces using different place to fill up... so far I have always used the same garage.

Also my MPG has dropped significantly, I was getting around 15-16 on petrol, this has dropped to 10.8 for the last tank!

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The tank will always fill to the same point regardless of the filling station or pump. This is because the shut off valve in the tank has an arm with a float. As the float rises, the arm gets to a point where a little cam flicks over and the valve slams shut.

However, the amount of gas you can get in MAY vary from one filling point to another IF the forecourt is not level. Similarly if your Rangie is heavily laden it may affect the angle at which the tank sits at.

You may not be getting 68 litres in if the tank has not been fitted at the correct angle in the boot. Most tanks have marks on them which are used to ensure that the tank is at the right angle. Some valves/tanks have the no. of degrees stamped on them to indicate the angle at which the valve box should sit.

For a simple single point/mixer conversion, you would expect to get 20% less miles per gallon on LPG than on petrol. This is partly due to the lower calorific content of the LPG by volume, and partly because the engine is not optimised for LPG (different timing curve and compression requirements).

If you are getting more than 20% economy loss, then the system may need fine tuning, and/or the system may not be as well matched to the engine as it could be.

Hope this helps,



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if the tank has not been fitted at the correct angle in the boot

See, I told you. :P

Have a look at the tank again, a lot of E marked tanks have a big + marked on them, that should be the centre & uppermost. Stick a spirit level in the back, your Boge strut may not be working, in fact surprise me if it is :rolleyes:

It will depend on how the float is oriented inside the tank, most I have looked at swing across the plane of the circumference if you know what I mean :blink:

Have you fitted an advance unit yet? With that, engine in good shape and the system set up properly you can expect 12-13 daily driving and up to 16 at a steady 70 with an RRC.

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That tank was fitted to the millimetre according to the specs that came with the kit. There was even a suppliment table that listed an amended height to use.

However, we'll have another look at it again shortly. Its the same diameter as my tank, so i'll compared the kits notes with the notes i have for mine. IIRC the kits notes said the hole centre was to be higher than what my setup was.

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If the tank is definately fitted at the correct angle, then the problem is likely to be that the multivalve/shut off valve either has the wrong length float arm(different for different diameter tanks), or the float arm got a little bent at some point prior to installation. Minor 'tweaking' of the float arm can be done to increase the capacity of the tank(bend the arm so the float is a little higher).

Obviously to do this, the tank needs to be empty and carefully vented(even when driven until empty, there will be a lot of pressure and vapourised gas remaining!).

If you ever get to this stage, check that the dip tube(pick up tube) really is vertical(pipe up which LPG flows from the bottom of the tank).

WARNING! Do not undertake this job unless you really know what you are doing! The tank should be pressure tested after removing and refitting valves inorder to check for leaks.

Many sophisticated systems like Cartman's have the ability to automatically shut off the supply of LPG when the tank gets low. This is because when the level of LPG falls below the dip tube(pick up tube), gas vapour will flow up the pipe to the engine rather than liquid gas. This results in the engine running lean and can result in expensive backfires. On more basic systems, you should switch to petrol as soon as the engine begins to falter on gas for this very reason. So systems like Cartman's are likely to leave a little more gas in the tank than basic systems. ALL tanks will have a little gas remaining when the engine starts to falter, because the dip tube/pick up tube doesn't quite go to the bottom, just like a petrol tank.

Hope this helps,

Regards, Diff

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