Petrol tank full or half full at start ?

[majordad]

Im wondering what the current best practice is for this , does having the tank full at the start risk leakage or fuel overflowing onto track ?

[Pica-Pica]

If you’re using an OEM tank there is no risk of leaking whatever during extreme vehicle manoeuvres, as long as you do not fill beyond the manufacturer’s maximum fill procedure. That is all tested. If modified, that’s another matter.

[brillomaster]

TDOs ive been to mention not brimming caterham/lotus 7 type cars, but everything else is good to be brimmed before tracking.

Unless you're a weight weeny, in which case start with a quarter of a tank, anf put 5litres in after every session.

[alfa-alex]

Fuel is heavy!

Quarter tank and add as required

[ecain63]

Just fill it up to avoid regular trips to the pump. My car (Exige 410) uses a 1/4 tank for 15 mins on track. My mates M2 uses about 1/3 tank for the same time on track and his tank is bigger.

I always fill up and run to the red light. 3 fills a day at Silverstone or 2 at Goodwood for example.

[majordad]

Thanks for the answers.

[Tommie38]

What is the car?

I’d fill just to save trips to the pump. Unless you are chasing times it really doesn’t matter, but you will probably be able to notice the change in handling.

[majordad]

Its a general question related to our Porsche track day here in Ireland.

[bigothunter]

alfa-alex said:

Fuel is heavy!

Quarter tank and add as required

Can you consistently detect the difference in lap times between a quarter and a full tank?

[brillomaster]

I can certainly feel the difference when i have a passenger to when i don't, thats about 70kgs.

And a big car could easily have an 80litre tank, so the difference between full and a quarter could be 60kgs.

Though, i wouldnt normally notice when i do a mid afternoon fill as the track is normally running faster then and ive got my eye in by then.

[E-bmw]

bigothunter said:

alfa-alex said:

Fuel is heavy!

Quarter tank and add as required

Can you consistently detect the difference in lap times between a quarter and a full tank?

No use to man-nor-beast in an e36, it will fuel-starve on right-handers more than a few seconds long.

[alfa-alex]

The car I drive isn’t very powerful, it was built as a race car and so everything is setup for just enough fuel to complete a race.

The difference in handling on a dry track is quite noticeable.

Fuel starvation isn’t an issue!

If you’ve gone to the extent of stripping the interior weight why would you want to add 40kg back in?

My way is right for me, though I completely appreciate my way isn’t right for everyone!

Alex

[bigothunter]

alfa-alex said:

The car I drive isn’t very powerful, it was built as a race car and so everything is setup for just enough fuel to complete a race.

The difference in handling on a dry track is quite noticeable.

Fuel starvation isn’t an issue!

If you’ve gone to the extent of stripping the interior weight why would you want to add 40kg back in?

My way is right for me, though I completely appreciate my way isn’t right for everyone!

Alex

Given that 40kg of petrol equates to 12 gallons, your race car must have a 16 gallon tank. Wow

[Dr Jekyll]

brillomaster said:

I can certainly feel the difference when i have a passenger to when i don't, thats about 70kgs.

And a big car could easily have an 80litre tank, so the difference between full and a quarter could be 60kgs.

Though, i wouldnt normally notice when i do a mid afternoon fill as the track is normally running faster then and ive got my eye in by then.

More like 45kgs.

[anonymous-user]

Indeed, petrol weighs about 750g/litre. An average tank capacity is 40 litres so a full tank weighs 30kgs....

[foxsasha]

Just brim it. Refilling after each sessions is a faff and I'll bet a packet of cheese and onion Seabrook that you see zero lap time difference. Not least because you no doubt won't be timing.

[C70R]

Pica-Pica said:

If you’re using an OEM tank there is no risk of leaking whatever during extreme vehicle manoeuvres, as long as you do not fill beyond the manufacturer’s maximum fill procedure. That is all tested. If modified, that’s another matter.

This. So much this.

Unless you're running a kit car or something with a modified fuel tank, I wouldn't give this question a moment more thought.

The driving heroes saying how they can 'feel' a weight difference of a 3-4% through rubber suspension bushes, road-legal tyres and PAS make me laugh.

[shalmaneser]

foxsasha said:

Just brim it. Refilling after each sessions is a faff and I'll bet a packet of cheese and onion Seabrook that you see zero lap time difference. Not least because you no doubt won't be timing.

This.

Fuel does make a big difference to feel though it does depend on the car - my 996 feels very different with a full tank vs an empty tank as when the tank is empty it highlights the f/r weight balance. Probably less noticeable in front engine rear wheel drive cars though with more normal weight distribution.

But it's a pain if you run out halfway through a session and have to waste track time leaving the circuit to fill up. Much better to do so over lunch.

[ChrisCh86]

Just fill it up to one click (i.e. don't overfill).

You'll use the petrol up so quickly that it's best just to put in as much as you can and be done with it. More time on track is the most important thing given how much you've paid to be there - and you won't notice the weight difference in your lap times.

[MOTK]

Worth considering also to not run too low depending on your car and which track. An example would be saddle bag tanks on say an e46 m3 going up the hill after the old hairpin at donington, gauge says just under 1/4 tank left but no fuel reaches the engine, ask me how I know.