On 24 Mar 2017, at 8:56 pm, Charlie England <flyrotary@lancaironline.net> wrote:

Have you tried swapping the position of the pumps & making the same measurements? It's hard to imagine it making that much difference, but the bottom pump does have a tight right turn and then a sharp edged 'T' turn to the left. I couldn't guess how much, but that would account for at least some pressure increase. 

Charlie

On Fri, Mar 24, 2017 at 4:14 AM, steve Izett <flyrotary@lancaironline.net> wrote:

Hi Guys

Hi Peoples

Here is a photo of our parallel pumps plumbed with 3/8 aluminium lines feed from a 28 gallon header tank above to the right.

Fuel then passes through the firewall and race filter before feeding the rail and returning via the pressure regulator (4cyl toyota reg) 

back through the firewall to the header tank, again in 3/8.

I did further measurements today. 

1. Bottom Pump only ~8A and 48psi - Turning both pumps on this pump draws 9.9A and produces a rail pressure of 65psi

2. Bottom Pump only ~9.9A and 44psi - Turning both pumps on this pump draws 14.8A and produces the same rail pressure of 65psi

So bottom pump goes from 8.0 -> 9.9A (1.9A increase) under higher head pressure

Top pump goes from 9.9A -> 14.8A (5.1A increase) under same head!!

Clearly Pressure Reg bypass capacity is inadequate for both pumps, perhaps with even one pump running. 

(I don’t have data of fuel pressure under load to see if it drops as power is applied)

I think I modelled the pump layout/manifold after seeing someone else’s and not sure if it causes any problems?

The pumps came from eBay stating that they were genuine Walbro and now I’m wondering.

Cheers

Steve Izett

Glasair Super II RG Renesis 4 port RD1C EC3 EM3 

<Fuel Pres Pumps.JPG>