twin-LPG-tanks

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jan_rrc39v8
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twin-LPG-tanks

Post by jan_rrc39v8 »

Yesterday i took the RRC to an LPG specialist to have a second LPG tank fitted.
That way i will have 2x 60L + the entire stock gasoline tank available for increased range. The 2 LPG-tanks will be coupled so i can fill them in one go.

I have opted not to have them mounted under the car but rather inside the boot, one on each side. The spare wheel will be carried flat on the floor between the 2 tanks and i will make a false wooden floor over it so i can carry luggage on top of the spare wheel.

The reason i don't want chassis mounted tanks is offroad capability and access.

I am curious how the electronic fuelgage indicator will react to having a second tank attached to the first.


DD: RRC 3.9efi lpg, project: bmw e9 CS with 3.5L turbo + MS&S

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ChrisJC
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Post by ChrisJC »

I have done this twice.

In theory, both tanks should empty together, and therefore having a fuel level sensor on one tank is OK.

However, in my experience, one tends to empty first, so the fuel gauge either doesn't move for ages, or moves rapidly then doesn't move for ages.

As a result, I use the trip / odometer to work out when I need to refuel!

I also found that a single fill-point didn't work very well on my van because UK fuel pumps will only deliver 100litres, and each of my tanks was 100l (total 200l). With two fillers, we could have two people filling it at the same time.....

Chris.
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jan_rrc39v8
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Post by jan_rrc39v8 »

little update: today i ran the twin-tanks to 8% left. I had no issues while driving and the indicator/gauge which is installed in the old 1st tank is still useable.

Filling: i managed to squeeze in 95L on top of the 8% (= about 10L) that was still in the tanks. The tanks are both 60L capacity , in one of the tanks the 80% limiter was taken out, this means i can fill both to a combined 90% = 108L. real experience = 105L
From 75L onward the pump had considerably more trouble to keep on pumping.
DD: RRC 3.9efi lpg, project: bmw e9 CS with 3.5L turbo + MS&S

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ChrisJC
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Post by ChrisJC »

jan_rrc39v8 wrote:in one of the tanks the 80% limiter was taken ou
That is very dangerous - why have you done that?

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jan_rrc39v8
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Post by jan_rrc39v8 »

ChrisJC wrote:
jan_rrc39v8 wrote:in one of the tanks the 80% limiter was taken ou
That is very dangerous - why have you done that?

Chris.
why? more range.
i don't agree with your view. Remember, in my setup i still have 10% expansion space left. With some carefull management it'll be no problem, it's being done all the time (just avoid parking the car with a full tank in the blazing hot summer sun or in a hot closed garage)
In reality you fill up and start driving, all the while lowering the level again.
DD: RRC 3.9efi lpg, project: bmw e9 CS with 3.5L turbo + MS&S

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Post by ChrisJC »

Do you have one-way valves in the tank outlet pipes between the tank and 'T' junction? Or are you effectively 'sharing' the expansion gap between the tanks?

I had a fault once which meant that a tank was being 100% filled, and boy did it go with a bang when the sun got on it. Smelled of gas too!

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jan_rrc39v8
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Post by jan_rrc39v8 »

the expansion gap is shared, the 2 tanks are effectively 2 communicating vessels. Only the outlet to the evaporator has an electric solenoid valve.

additionally both tanks have an overpressure relief valve that is connected to the outside air via vent hoses. (in case the car burns while the tanks are full. This way a controlled release of LPG is guaranteed)
Lots of rendundancy and built-in safety in the system.
DD: RRC 3.9efi lpg, project: bmw e9 CS with 3.5L turbo + MS&S

Uzzy123
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Hiya mate quick question

Post by Uzzy123 »

I just topped up first time 93 lit that all it went in I have 105 lit double tank. The red light came on when I was on 340 miles. I topoes up again only this time 60 lit went in and the light start flashing at 315 miles

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