E60 M5: Auxiliary fuel tank

[rassi]

I have contacted Dahlback Racing, to see if they can adapt one of their 55 litres auxiliary fuel tanks to the M5.

http://www.dahlbackracing.se/english/main.asp (Go to Other Parts, Fuel system).

Having a range of 400 km bothers me much more than the actual costs of filling up, so if a solution could be found, it would make the M5 in my use (long distance driving, 450-1000 km) much more practical.

The tank would be installed where the roadside kit (compressor, etc) lives, i.e. the "spare wheel well" - would anyone have the max dimensions, depth and diameter, of the "spare wheel well" as mine is currently having its clutch and flywheel replaced, so don't have access to measure it myself.

[joscal]

Great idea! The small tank is the problem as although thirsty MPG is no worse than similarly powered cars.

Might give you more traction in current weather too!

Cant help with measurements as mine is in storage, sorry.

[Babw]

I'd be a bit concerned about upsetting the balance of the car. BMW have gone to some length to achieve a near 50/50 weight balance.

[ecain63]

Babw said:

I'd be a bit concerned about upsetting the balance of the car. BMW have gone to some length to achieve a near 50/50 weight balance.

Should only be a concern if the car is being tracked hard. No difference having an extra 55ltr of fuel in the boot t having a small adult or older child in the back. In fact even on track 55ltr of petrol would make no odds over a circa 2000kg chassis.

[rassi]

If a tank could be adapted it would in any case be smaller than 55 litres due to the battery. The mobility kit and foam pack could easily be removed though. I hope to get my M5 back tomorrow and will do some measurements then.

[Babw]

ecain63 said:

Should only be a concern if the car is being tracked hard. No difference having an extra 55ltr of fuel in the boot t having a small adult or older child in the back. In fact even on track 55ltr of petrol would make no odds over a circa 2000kg chassis.

Correct me if I'm wrong but surely the moment of having 55kg from the mass centre of the car (assuming this is the gearbox region with a driver) another 2-3 feet further back would be far greater than having an adult in the back seat.

[andygtt]

Babw said:

ecain63 said:

Should only be a concern if the car is being tracked hard. No difference having an extra 55ltr of fuel in the boot t having a small adult or older child in the back. In fact even on track 55ltr of petrol would make no odds over a circa 2000kg chassis.

Correct me if I'm wrong but surely the moment of having 55kg from the mass centre of the car (assuming this is the gearbox region with a driver) another 2-3 feet further back would be far greater than having an adult in the back seat.

Yes but it will very rarely be full if fuel lol... Also Remember what it replaces will also weigh a little so offset some of the extra weight.

Saying that it definatly won't be an improvement to the car, and I don't think I need extra range as it does 300miles to a tank on long runs now!

[Mattt]

Babw said:

ecain63 said:

Should only be a concern if the car is being tracked hard. No difference having an extra 55ltr of fuel in the boot t having a small adult or older child in the back. In fact even on track 55ltr of petrol would make no odds over a circa 2000kg chassis.

Correct me if I'm wrong but surely the moment of having 55kg from the mass centre of the car (assuming this is the gearbox region with a driver) another 2-3 feet further back would be far greater than having an adult in the back seat.

Given that the OP wants it for long range driving, I would tend to think that this involves more motorways than racetracks - where this is irrelevant.

Depending on the fitment/routing, he could then shut it off empty for track driving.

[phelix]

we're splitting hairs here - 55 litres of petrol (which is a fair old volume and not easy to find additional space for) only weighs 40kg. And as Eddie points out that sort of additional weight in a 2000kg car is almost nothing.

[Contigo]

Dahlback are near Bergen, great guys!

[ss1977]

Just wondering if there's any update on this? Sounds like a great idea!

[ndj]

Apart from the shocking price my primary concern would be having 55 litres of gas a few inches away from the battery, and inside the passenger compartment, in the event of a medium to heavy rear end shunt.

[rassi]

Afraid no updates - sent a diagram with the measurements 2 weeks ago, but haven't heard back. Will do a reminder now. As to the 55 litres near battery, etc, I agree that it could be an issue, but my understanding is that the auxiliary fuel tank is built to racing standards, so should withstand a medium impact.

Will report back if I get any news.