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      12-01-2012, 02:04 PM   #313
ign335i
Second Lieutenant
 
Drives: 335i e92
Join Date: Nov 2012
Location: CA

Posts: 286
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Quote:
Originally Posted by trbolexis View Post
Disassembly of the stock fuel sending unit is a delicate process, and when it comes down to it, you are essentially breaking it apart to install the pump.

The suction valve at the bottom of the assembly is not regulated at +70 PSI in factory form. Pushing the pressure through it up that high is going to cause failure at some point; but i have no data on that point currently. To add to this note, there is also no sealing surface for it to be completely "fuel tight" at the base when held on by zip ties. -- Imaging having a huge boost leak all before your throttle body because you didn't feel like putting a clamp on the coupler. You would be able to hit boost certainly, but with very little wow effect; and all that leaking boost out of the system is going to cause the turbo to have to work harder to maintain pressure. As a result, it may over-run, and fail prematurely. Another note, the leaking boost around before the TB is also going to cause your boost to fall off at higher RPM as your turbo falls out of its efficiency range. -- Remove the word turbo from all that i previously mentioned, and sub in fuel pump. Remove 'boost leak', and sub 'fuel leak'. Remove TB, and sub 'before your HPFP'.

I think you get the point. The DIY procedure is going to essential cause a fuel leak in the low pressure system which makes the pump work harder, and also causes loss off efficiency as pressures go UP (and the pressure in the LP system is much higher than most any other vehicle in production, period.); this is why you want to leave the stock system intact. The booster pump will NOT cause a leak, and will ONLY raise fuel volume flowing to the HPFP. It gives you complete peace of mind when driving your car on long trips because you know that your stock siphoning valves and fuel regulated systems are 100% fail proof, and that your fuel gauge is accurate.
A lot of propaganda here. My favorite bits are speculation on breaking the suction valve, that your fuel gauge wouldn't work with another solution, and that you need to break the stock LP unit when it is clear you can just drop a Walbro E85 pump in. Ironically the inline booster pump uses a Walbro E85 pump anyway to patch up underperforming stock system. I'd love to see how the pump is cooled (since intank pumps need to be in tank to cool). If it is intank, well then guess who's fuel gauge isn't reading accurately.

Last thing, its already been demonstrated the DIY E85 Walbro holds LP at 100% ethanol and 500+rw on RBs (demands more fuel than single turbos). In fact much past this you will see HP start to fall, indicating the $200 DIY eliminates LP issues.

I guess once we see more details this pump setup could look better, but so far I am unimpressed. I have been waiting for a LPFP upgrade and was honestly expecting a lot more than this. Not just a copy of the DIY Walbro slapped on top of the stock unit. I will wait a little longer for more info and results, but its not looking good!
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