Hey guys, thought I'd post a couple of the findings so far.
First, a little background. Normally when testing pumps I test the assembly, meaning the electrical pump itself in the bucket/assy as per the factory, with factory or upgraded venturi's etc. The reason why is end use assembly matters more than pc/part comparisons, BUT... we need pc/part comparisons to make good decisions on building that final assembly.
Before we get to that point though, let's take a look at what we're working with internally, pump wise on the 5 series. I grabbed a new Bosch 5 series pump assembly, and first things first, pulled 'er apart to see what the guts were like. Pretty stout! Tossed her in the 'ole reliable portable pump test bench (made 'er on a shop cart) and this is what I got.
You could call that 1.25 GPM minus a little. Voltage was 13.5V, current draw was about 16 Amps. Remember this is the pump itself, straight connection directly off the pump (-6 line on the OEM pump hose barbs).
There are normal fluctuations with pumps, you'll see some run a touch stronger than others. Some of this is wear in, some of it is unit-to-unit inconsistencies. By and large they all fall within a fairly tight performance window, but this is one of the reasons why we validate pump assembly performance on
every single pump, before anything is shipped -no exceptions.
So let's take a look at the venerable Walbro 450. Commonly used as an OEM pump upgrade on the BMW platforms, we know on the 3 series N54 (and some N55) powered vehicles the 450 outflows the stock pump by a massive amount. Seems like a shoe-in for an upgrade on the 5 series too -let's compare it pump-to-pump and see what a brand new 450 puts down -remember, this is -6 line attached directly to the hose barbs on the pump outlet, no fittings, no goofiness, just pure pump output on our test stand:
I'd still call that 1.25 GPM, only I wouldn't say "minus a little". Voltage was 13.5V, current draw was about 19 Amps.
The competition markets the 450 as an upgrade on a 5 series, but I don't see it. Less than 0.1 GPM difference, draws 3 Amps more, and a complete package out the door (with no core) is close to $900 for the mods done to a pump you can pick up new from FCP for under $200 shipped. The 450 does, however, slightly outflow the stock pump, and remember the stock pump isn't "officially rated for E85 use". Personally? Not impressed and neither should you be. Not many people have test stands to validate performance on; I spent a large part of my career as a test engineer, so while I'm comfortable with some seat-of-the-pants engineering, it's all a bunch of bullshit if you don't get real world performance out of it. The 450, god love it, comes up short -not because the 450 isn't a great pump, but because the 5 series pump is so much better than expected.
The 5 series pump assembly is a bit of a pain in the ass to take apart. Granted, I've only done one (and it IS doable) but for the guys who want a reasonable LPFP upgrade, a 450 is absolutely NOT the key to victory; save your money, it's a TERRIBLE value to put a 450 in a 5 series. Don't despair though, we have plenty of great options to keep you guys happy with fuel.
One final note about flow numbers; these are similar to dyno numbers in that it's difficult to directly compare one setup to another pump test bench elsewhere, so don't get too bogged down in the direct numbers, just understand that if I put a pump on and it flows X GPM, swap pumps and it flows 2X, that same delta is going to be on any other test bench.
Our pump stand numbers are good; don't bother with a 450 in your 5 series. We'll have more solutions for you soon.
Chris
Edit: Someone requested a chart to outline the differences. Using advanced technology, I did such a thing.
