Service C27 - Fuel Flowrate with quick disconnect fittings installed...
For the last 8 or 10 years now, I have used ethanol-free fuel combined with Stabil fuel stabilizer in all my small engines and old vehicles. The last fuel-related issue I have had in anything was with the RZ350, but that was pre-ethanol-free days mixed with a whole bunch of neglect. Even the small hoses on my small engines (mowers, string trimmers, chainsaws, etc.) don’t have to get replaced every two years anymore.
Although Stabil says it works for up to 2 years and even thought the RZ500 was starting and running fine with the old fuel, I realized the fuel in there was much older than that so I decided to drain and replace it. To my defense, I have added a half gallon here and there as it needed it, so some of the fuel is fairly fresh.
Remembering back to when I installed some quick-disconnect fuel fittings from the tank, there was some discussion and concern whether the fuel flow was being restricted in some way. At the time, I wanted to measure this just to set my mind at ease about damaging the engine due to a lean running condition (fuel supply starvation). But it’s better late than never!
Link to prior discussion on flowrate:
http://www.rzrd500.com/500phpBB3/viewto ... 105#p96883
In that reply, it was stated that we are looking for a flowrate greater than XXX. Here is a snip of the recommendations:
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This reply came from forum member Wolfgang:
"I usually do the following math to get a ballpark figure, using expected max. peak fuel consumption. My calculation is in ltrs/100km as we do in most part of Europe, you can modify this to mpg of course:
Assumed max. consumption is 20l/100km at a speed of 200km/h.
Within 1 hour, you would drive 200km = 20l * 2, so you would burn 40l of fuel.
Your fuel lines need to flow a min. of 40l/hour.
So put a fuel line into an empty bottle and measure the amount of fuel you get within a minute. If it is min. 40/60 = 0,67l, you should be safe. If it is 1l per minute, you can feel even better."
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In all honesty, I feel a steady state one hour calculation is possibly understating the peak fuel usage at any given moment. I would venture that twice that flowrate a might be witnessed during a WOT run up through the gears. Perhaps 1.4 liter/minute range might be a more suitable target to set.
First, I rounded up a portable tank to catch the fuel (I always reuse any drained fuel in the mower because it will happily burn anything!).
Picture 747
Then attached my mating fitting and drain hose to the RESERVE line.
Picture 748
There was less fuel left in there than I thought and I dumped in into a smaller 1 gallon sized container for easier measuring. Even with the backlighting, the fuel level is difficult to see in this picture, but blue tape marks full gallon and actual height of fuel. The rough amount of fuel in the can is therefore 4.188/6.625 = .632 gallons.
Picture 749
While I was draining the fuel, I used a stop watch app to measure time, which recorded 83 seconds.
Picture 750
Doing the math for .632 gallons in 83 seconds works out to:
Fuel Flowrate = 0.457 gpm = 1.73 liter/min.
As I was conducting this test, the speed of the flow indicated it wasn’t going to be a problem (it was flowing fast!), but it’s nice to know the exact number.
After I finished up this little test, I realized I overlooked one small (maybe big?) detail… the tank venting. While I was draining the fuel, I had the cap off the tank. A more thorough test would have had the cap installed to check whether the venting is restricting flow in any way. I guess I will do that another day and at this point, I have the flowrate with tank wide open for comparison.
For now, I can rest assured the fuel line disconnects aren’t an issue.
C27 Total Cost: US$0.00 (Just measurements - Flowrate calcs)
