Randall Washington, Proprietor - aka "Randakk"
Chapel Hill, NC USA
Reverse Engineering Information...Electric Fuel PumpsPlease read: DisclaimersRandakk's Electric Fuel Pump Conversion Kit for Honda GL1000 and GL1100
If you've landed here, you're no doubt sold on the advantages of an electric fuel pump. Perhaps you are searching for a way to make your own electric fuel pump, save a few bucks and not buy mine. Good luck if that is your plan, but you might care to read on... I see examples of such efforts posted online by obviously proud owners. I see many engineering problems with these efforts. There's a temptation to get drawn into these threads (especially when my product is discussed or obliquely referenced), but I have decided to try stay out of them and post this information here instead. Facet makes dozens of models of fuel pumps that all look the same externally. I get an amazing number of brazen requests asking for the specific model number for the pump I use. Not going to happen! The model I use is specially ordered and not widely available. You won't find it in auto parts stores, online speed shops or aviation supply catalogs. The pressure and flow ratings were optimized for this particular application through a rather extensive R&D effort. It also incorporates an anti-syphon check valve. The pump I selected is a "non-certified" variation of the "FAA - Type Certified" boost pumps used in many light aircraft including Piper Cherokees. Such pumps have been used for decades and are ultra reliable. However, this is one case where aviation considerations are "bad" for road use. In most light airplanes, you would want fuel to flow if the pump fails. In an earlier life, I was a pilot. Pilots are trained and have good discipline in the use of petcocks. Bike riders do not. On a bike - if fuel flows past a failed pump and there is no check valve and the petcock is left on and one or more float valves don't perform - you risk catastrophic engine failure through hydro-lock. So there is a strong argument against aviation pumps for this application. The "copies" I've seen of my electric fuel pump conversion have all made bad choices on the pump model selected. All of the Facet model numbers I've seen posted to date by reverse engineers are less than ideal on the issue of pressure rating. A commonly mis-selected Facet pump is spec'd at 2 1/2 - 4 1/2 psi. On the high end, this pressure is excessive and will surely overwhelm Keihin float valves...especially when they have a bit of wear. Since these pumps are relentless, chronic flooding is the inevitable outcome. The OEM mechanical pump delivers at a pressure (spec cited in the Honda manual) that is about ideal for the OEM Honda Keihin float valves. Unfortunately, it delivers the pressure in a pulsating fashion which is not ideal. Electric pumps deliver in a steady fashion which helps idle performance. Higher quality float valves (like those found in Weber carbs) can accommodate much more fuel pressure... those can live happily on 4 psi. Pressure is only part of the equation. The other main variable is volume. Volume must be sufficient to support extended wide open throttle, full power operation. Calculate miles per gallon fuel use at max throttle. How much fuel would you burn at 125 mph in an hour? That's the rate at which your fuel pump should be able to deliver in an hour...even if it's only for short bursts. Otherwise, you risk high speed lean-out which can cause engine damage. Point of fact: Honda was very conservative on this point. The OEM mechanical pump exceeds the max volume requirement by a considerable margin. I've seen backyard electric fuel pump conversions that will deliver about 10 times the actual volume required! Anything more than the max required for the application is "bad." Also, an external pressure regulator will reduce the flow rating of a pump. These are unnecessary (when the right pump is selected) and introduce an additional point of failure. They should be avoided. Since the GL1000 has almost zero reserve charging ability, electric pumps must be selected with some consideration given to their electrical draw requirements. Again, I see some pumps in use that far exceed the desirable limit on this point. I see examples of homemade electric fuel pumps conversions where the mounting location was poorly engineered from a heat management viewpoint. The engineering of mounting location, air flow and isolation material strategies are critical for long pump life. Finally, on a purely cosmetic issue...Facet pumps are cad-plated. Attempts to paint over this finish are generally doomed to failure and may actually harm the pump. Legalities and ethics aside, you are certainly free to copy my design and attempt this on your own. If you do, please don't contact me seeking technical assistance (as others have) if you run into difficulty. For obvious reasons, you are on your own. Simple product? Perhaps, but more than meets the eye! Back to: Randakk's Electric Fuel Pump Conversion Kit for Honda GL1000 and GL1100 Please read: Disclaimers For more information on the use of material from this website, click here. |
