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  1. S1S2euroS3LotusEspritOwners
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Fuel tank xover plumbiing

 

Had a secondary (the one without the sender unit) fuel tank made, but any particulars on how to plumb it for the crossover tubing. Like what is the threading on that bottom pipe piece and did people put a shut off on that before it picks up the crossover tubing? And heard some complaints about how long it takes to equalize fuel, so did people put in bigger crossover hoses?, Thanks, Gordon
 

Crossover hose on the S1/S2 is small. I think it¡¯s basically a standard fuel line. The later cars had a much bigger like 1¡± or maybe larger hose. Actually the later cars had 2 custom formed hoses and a crossover pipe. That makes a big difference in crossover flow but changing that would require modifying both tanks because you would need the bigger spigot on both tanks. The Turbo Esprit draws fuel from the left tank, pumps it up to a bypass pressure regulator and the bypass flows back to the right tank. Because of the bypass the fuel pump is constantly pumping gas front he left tank to the right tank so the cross over is normally flowing gas back from right to left even when standing still and idling. The crossover needs to flow better with gravity than the fuel pump can deliver so it needs to be bigger. S1/S2 uses a low pressure pump with no fuel return so theres no need for the extra flow in use. It would certainly be nicer for filling up though if that hose were a bit bigger. The fittings on the later tanks are all BSP thread with a Banjo bolt and I suspect that the S1 S2 is the same but I cant be certain without looking. BSP threads come in both T (Taper) and P (Parallel) versions, the tank threads are parallel meaning they are standard straight cut threads and the seal comes from the gasket washers on the banjo fitting. Taper threads are like Pipe threads that seal on the taper of the threads usually with the addition of teflon tape or pipe sealing compound.

Dave C

On Aug 23, 2023, at 12:07 PM, gsauerphd1 via groups.io <gsauerphd@...> wrote:

?Had a secondary (the one without the sender unit) fuel tank made, but any particulars on how to plumb it for the crossover tubing. Like what is the threading on that bottom pipe piece and did people put a shut off on that before it picks up the crossover tubing? And heard some complaints about how long it takes to equalize fuel, so did people put in bigger crossover hoses?, Thanks, Gordon
 

Thanks for that, going to be at log 42, so hopefully somebody there with an S2 that I can take a bunch of pictures of because as I go to reassembly I see I¡¯m not quite remembering all I need to, but just bringing +2 this weekend, thanks Gordon

On Aug 23, 2023, at 1:17 PM, dave78esprit via groups.io <armsdc@...> wrote:

?Crossover hose on the S1/S2 is small. I think it¡¯s basically a standard fuel line. The later cars had a much bigger like 1¡± or maybe larger hose. Actually the later cars had 2 custom formed hoses and a crossover pipe. That makes a big difference in crossover flow but changing that would require modifying both tanks because you would need the bigger spigot on both tanks. The Turbo Esprit draws fuel from the left tank, pumps it up to a bypass pressure regulator and the bypass flows back to the right tank. Because of the bypass the fuel pump is constantly pumping gas front he left tank to the right tank so the cross over is normally flowing gas back from right to left even when standing still and idling. The crossover needs to flow better with gravity than the fuel pump can deliver so it needs to be bigger. S1/S2 uses a low pressure pump with no fuel return so theres no need for the extra flow in use. It would certainly be nicer for filling up though if that hose were a bit bigger. The fittings on the later tanks are all BSP thread with a Banjo bolt and I suspect that the S1 S2 is the same but I cant be certain without looking. BSP threads come in both T (Taper) and P (Parallel) versions, the tank threads are parallel meaning they are standard straight cut threads and the seal comes from the gasket washers on the banjo fitting. Taper threads are like Pipe threads that seal on the taper of the threads usually with the addition of teflon tape or pipe sealing compound.

Dave C

On Aug 23, 2023, at 12:07 PM, gsauerphd1 via groups.io <gsauerphd@...> wrote:

?Had a secondary (the one without the sender unit) fuel tank made, but any particulars on how to plumb it for the crossover tubing. Like what is the threading on that bottom pipe piece and did people put a shut off on that before it picks up the crossover tubing? And heard some complaints about how long it takes to equalize fuel, so did people put in bigger crossover hoses?, Thanks, Gordon

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