I am planning on using a EFI system on my O-320. I recently got a deal on a Andair fuel selector valve with #4 return ports. After the fact, I found out that EFII uses #6 on their returns to flow more fuel back to the tanks to limit vapor lock.
I decided to conduct a test to see how much difference can be had in this system. I know sizing is critical on the suction side, but not as much on the pressure side. I have a racing shop, so I had a lot of fittings and parts lying around. Here are the setups I tested:
#6 Return setup
6' of #6 braided line into Warbro pump, out #6 to pressure regulator set at 35psi, out to multiple #6 fittings(8), 5' of #6 hose and 5' #6 SS hard line.
Pumped gasoline for 30 sec into a container and measured the volume by weight in grams
Ran the test 4 times averaged 2695g or 86.4 fl/oz with a variable of about 10g
#4 test
Same setup, but after the regulator drop down to #4, with 8 fittings, 5' -#4 hose and 5'- #4 SS hardline.
Results averaged 2690g or 86oz
I difference of .4 fl/oz or 1/2 of a percent.
I'm planning on running all #6 lines to the regulator and only #4 hard lines after the regulator. I think I should be fine and plumbing may be a little easier with the #4 returns. I also believe the valve can be had for a fair amount less from Van's with the #4 fittings than you can find #6 ones elsewhere?
This isn't meant to start a debate and I may be off. I just thought I would share my findings.
Thanks
I decided to conduct a test to see how much difference can be had in this system. I know sizing is critical on the suction side, but not as much on the pressure side. I have a racing shop, so I had a lot of fittings and parts lying around. Here are the setups I tested:
#6 Return setup
6' of #6 braided line into Warbro pump, out #6 to pressure regulator set at 35psi, out to multiple #6 fittings(8), 5' of #6 hose and 5' #6 SS hard line.
Pumped gasoline for 30 sec into a container and measured the volume by weight in grams
Ran the test 4 times averaged 2695g or 86.4 fl/oz with a variable of about 10g
#4 test
Same setup, but after the regulator drop down to #4, with 8 fittings, 5' -#4 hose and 5'- #4 SS hardline.
Results averaged 2690g or 86oz
I difference of .4 fl/oz or 1/2 of a percent.
I'm planning on running all #6 lines to the regulator and only #4 hard lines after the regulator. I think I should be fine and plumbing may be a little easier with the #4 returns. I also believe the valve can be had for a fair amount less from Van's with the #4 fittings than you can find #6 ones elsewhere?
This isn't meant to start a debate and I may be off. I just thought I would share my findings.
Thanks