Everyone keeps telling me that my fuel system isn't big enough for my new motor, so I decided to do some testing. Bear in mind that my fuel pressure is stable throughout an entire run, and I haven't seen any indications that the system is inadequate, it just SHOULD be according to a lot of people I've talked to.
The procedure:
- Use the manual override switch for the fuel pump to pump 5 gallons of fuel into a can, through the entire fuel system (filters, regulator, etc..)
- Restrict the fuel line AFTER the regulator to maintain various indicated fuel pressures during the pumping procedure (measured on my in-car Autometer gauge)
- Time the entire pumping of 5 gallons to determine the fuel flow/hour
My setup has two -6AN lines running from the regulator directly to the carb bowls. I used a -6AN tee to restrict the flow to a single line, then tacked additional things I had lying around the garage onto the single line (a -6AN to -4AN reducer, a spare filter, a length of 1/4" hard line, etc...). With these various things at the end of the line I was able to maintain very solid fuel pressure during pumping, without adjusting the regulator.
The Results:
<pre class="ip-ubbcode-code-pre">
PSI Time (m:sec) Gallons/Hour
2 2:59 100.55
4.5 3:14 92.78
5 3:25 87.80
6.5 3:55 76.59
</pre>
Interpreting the Results:
I'm running VP C12 fuel, which has a specific gravity of .717, which means it weighs 5.98 lbs/gallon (at 60deg F).
At 6.5psi, my fuel system is therefore pumping 458 pounds of fuel per hour. Depending on the BSFC of my engine (which I don't know off the top of my head), the fuel system will be able to support different amounts of power:
<pre class="ip-ubbcode-code-pre">
BSFC HP
.45 1017
.5 916
.55 832
.6 763
.65 704
.7 654
</pre>
I'm going to guesstimate that my BSFC is somewhere in the .5 range, which means the system has over 200hp of "headroom". I'll call the engine shop on Monday and see if they recorded it during the dyno session just to be sure.
Does anyone see any problems with this procedure/result?
Has anyone else done similar testing? Anyone want to? I'd be interested to see how some of the big $$ fuel systems compare to my relatively cheap setup.