Suck or blow?

[greenwoo]

Easy tiger.....

Soooo. The new fuel tank will have an internal collector which the maker assures me will remove the need for the external swirl pot ( unless i take up racing and run the tank on fumes ).

Part of my intent was /is to remove the need for the lift pump....however here's the question for the clever among you.
The specs for all HP pumps such as Bosch/Sytec etc all state that the pump cannot 'lift' and in reality i;d like to have positioned it about 6-8cm ABOVE the outlet ( because that way it can sit above the chassis rail).

Logic in my head says that on starting the car up unless the fuel is down to just 6/8cm in the tank the gravity effect would prime the pump. But would that hamper its performance? Ie/ its sucking vs being totally gravity fed?
and...would that likely cause any issues when/if the tank were to run low, in perspective 7cm in the tank would equal about 2.5galls...and quite often i run the car down to the last gallon, and sometimes worse!

Any thoughts?

[Tony B]

Im in the camp of wanting to fit the HP pump lower than the outlet of the tank, my logic states that its not good for a pump to suck, but also my logic (which could be completely wrong) says once your below 2.5 gallons then its unlikely youll be able to start the engine.

6 to 8cms is quite a distance(so ive been told before), cant you fit the pump below the chassis but still have other parts of the car lower for the road scrapes?

[jeffw]

Would you not be much better having the pump in the tank like production cars do?

[David T]

My external Sytec HP pump is about half way up the tank and has worked without issue for 7 years. I'm typically running tank in the top half unless on a long run or road trip when it gets down to the last few litres. I know there are some additional merits to a LP pump too, but during my recent rebuild I was not convinced to change what has been working well.

[greenwoo]

Would you not be much better having the pump in the tank like production cars do?

explored that a bit Jeff, started to get complicated in terms of finding one with the right height and then having to get a better/proper fixing in the tank for it to screw into.

[b33fy]

They can suck to a degree, 6/8cms wouldn’t be a deal breaker imo. Grab a Bosch 044 copy, sytec or similar, and see how it goes.

The in tank solution isn’t as difficult as it sounds, the height/depth can be adjusted relatively easily. The Impreza set up is easy to alter, though it needs to be sorted at tank fabrication stage.

[Fury1630]

Just a thought - if the pump is too vulnerable when fitted at / below the bottom of the tank, is the tank not vulnerable?

Fit it as low as you can get it, I'm sure it'll be fine*

*I'm not a fuel system expert & haven't much idea what I'm talking about

[leegav]

I’m with Jeff built in would have been easier.
All in one system would be less complicated. Tiger fit shitty pumps above the outlet on all older tigers. Sit that type of pump above the chassis and you won’t have any issues. Do you have any other option? Below the chassis is obvs a no go.
If it’s a decent tank the internal baffles and the placement of the outlet will negate any worries.

[Hammy]

Would you not be much better having the pump in the tank like production cars do?

explored that a bit Jeff, started to get complicated in terms of finding one with the right height and then having to get a better/proper fixing in the tank for it to screw into.

The Landrover (Discovery I think) and MX5 (mk1 and mk2) have a good in tank solution used in a lot of kits.

Cheers