Thread: LPFP Tech info
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      01-22-2013, 06:55 PM   #180
Dave W.

Drives: Porsche 951, 1992 Eagle Talon
Join Date: Apr 2012
Location: SF Bay Area

iTrader: (0)

Somewhere in the middle of this thread someone asked if anyone noticed that Shiv edited his numbers and made it look better. I noticed and I got a little laugh out of it. I'm not sure if anyone else understood the humor behind it, so here it is;
In Shiv's original post he rated the Walbro 450 pump a little conservatively to be on the safe side. Apparantly Terry was in a huff over Shiv's post, so Terry promptly corrected Shiv. Shiv edited his post using the numbers that Terry was insisting on, and the results immediately looked better for Shiv +Co! lol

Of course Shiv was a gentleman about it and merely replied,

It's in post #7 for those following along.
Terry; "As far as I know the Walbro "267" pump is rated @ 355 liters/hr @ 70psi @ 13.5v on paper. 1 liter/hour is 1.63 pounds/hr for gasoline. More for E85 of course. So with no over head it's rated at 578 pounds/hr worth of gasoline."
Shiv; "Ok"

Next point; fuel heating. If you have a pair of pumps that draw high amps they will heat the fuel. How much heating they put out is another topic, it also depends on how many gallons are in the tank since 15 gallons can absorb the heat without raising the temp much. Low fuel levels might see higher temp increase. Luckily gasoline has relatively the same flow characteristics at different temp so it doesn't matter much. OTOH E85 is sensitive to heating and gets less dense as it heats up. I'm at lunch so I can't do a search right now, if anyone is interested just lookup 'temperature-density Ethanol'. It's the reason OEM flex fuel sensors have a temperature sensor built into them. They not only read ethanol content but fuel temp, too.

I'd also like to encourage anyone who's interested in learning about the N54 fuel system to read the following link;
There's a lot of good info there. Read the first few pages, there's more info added as the thread goes along. The golden rule for modifying anything is to first understand how it works before you try to make changes.