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RSFan
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Last seen: 5 days 2 hours ago
Joined: 05/08/2020 - 13:24
Seeking expert advice on a dual pumps setup

Hi, 

I'm seeking expert's advice in view of upgrading an oem tandem fuel pump system, car is a 2003 Audi RS6 C5. Reason for the upgrade is the use of e85, but also for preventive maintenance as those pumps are 17 years old or so by now. 
Current configuration is an in-tank pump followed by an in-line pump, pressure in the rail is 4 bars. To achieve the upgrade I've purchased an in-tank pump from another brand (starting with W, model number F274 - couldn't find an equivalent at AEM sorry), and an in-line AEM 400LPH.

Now that I'm just about to install the new setup, I'm having doubts : as confirmed by other rs6 c5 owners, the in-tank pump is enough to fuel the engine up to 650HP, so I was wondering if there is any advantage in keeping the tandem setup, knowing that my target is a reasonable 550HP. My uneducated feeling is that the job would be shared by 2 pumps instead of one so put less constraints on the pumps, but at the expense of moving/compressing more fuel hence increasing its temperature.

What do the wise ones say on the subject?

Many thanks! 

RSFan
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Last seen: 5 days 2 hours ago
Joined: 05/08/2020 - 13:24
Bump 

Bump 

AEM_NS
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Last seen: 3 days 2 hours ago
Joined: 06/06/2014 - 09:31
Typically pumps in series are

Typically pumps in series are for higher pressures while pumps in parallel are for higher flow. The general rule of thumb is that pumps in series need to be very similar in flow because if they're not, the upstream pump may starve the downstream pump and damage it. Long story short, except in specific cases, you'd want pumps in parallel to support more flow and more power. You don't need more pressure and putting two pumps in series doesn't get you a pseudo surge tank where you have a lower output pump filling a reservoir that a higher output pump then pulls from. The "right" way to do two pumps would be to run them in parallel.

It's also a good idea to specify where you're referencing power from - either at the crank or at the wheels - and to not mix them.  A 450LPH pump may support 750 crank hp but that's only ~560 all wheel hp.  If your target is 550 all wheel hp, then you'd be using 98% of the pumps capacity.  550 crank hp would be ~410 all wheel hp.