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I am currently captivated with the idea of converting a recently aquired 1977 GS750 to fuel injection. Im confident i can adapt a set of GSXR600 or GPz1100 throttle bodies, rebuild the harness to include a Microsquirt EMS computer, and modify the fuel tank for a return-type high pressure fuel system.
The single hurdle i have been unable to resolve as of yet is the fuel pump. It is my intent that this retrofit be totally reversable should i desire to revert to the original mikuni setup (perhaps for resell value at a later date). As a result i have discarded the idea of canabalizing the near perfect fuel tank in order to adapt a modern in-tank fuel pump. I therefore have been searching for a suitable inline fuel pumps.
Unfortunately the only production motorcycles that i am aware of that were equipped with external pumps from the factory were GPz1100s and GSXR1300. These pumps seem to be extremely rare and/or hideously expensive from the manufacturer ($450 for a GPZ pump!).
The only viable option then is to find the smallest available car/truck inline external fuel pump. Unfortunately the smallest i have been able to located is a Walbro GSL393 which flows 155 L/hr @ 40psi and draws 5A at that rate. Not only is that WAY more fuel that is requried to fuel an 80hp 750 motor but that's also more current than i would like to allocated for the fueling system.
So here is my proposal:
Simply reduce the operating voltage to the fuel pump using a high efficiency switch-mode power supply. Similar to the power transformers that power modern laptops. I can build an ~90% efficient SMPS based on simple, commonly available components to step 15V down to a lower voltage to input to the GSL393.
Take a look at the flow/pressure/current curve provided by Walbro (below).
If im not mistaken, i should be able to adjust the input voltage until 3A is drawn by the pump, at which point it will flow 57L/Hr (15GPH), more than enough for my application, and 3A is more feasible with the GSs (feable) alternator.
Thoughts?
-Zander
The single hurdle i have been unable to resolve as of yet is the fuel pump. It is my intent that this retrofit be totally reversable should i desire to revert to the original mikuni setup (perhaps for resell value at a later date). As a result i have discarded the idea of canabalizing the near perfect fuel tank in order to adapt a modern in-tank fuel pump. I therefore have been searching for a suitable inline fuel pumps.
Unfortunately the only production motorcycles that i am aware of that were equipped with external pumps from the factory were GPz1100s and GSXR1300. These pumps seem to be extremely rare and/or hideously expensive from the manufacturer ($450 for a GPZ pump!).
The only viable option then is to find the smallest available car/truck inline external fuel pump. Unfortunately the smallest i have been able to located is a Walbro GSL393 which flows 155 L/hr @ 40psi and draws 5A at that rate. Not only is that WAY more fuel that is requried to fuel an 80hp 750 motor but that's also more current than i would like to allocated for the fueling system.
So here is my proposal:
Simply reduce the operating voltage to the fuel pump using a high efficiency switch-mode power supply. Similar to the power transformers that power modern laptops. I can build an ~90% efficient SMPS based on simple, commonly available components to step 15V down to a lower voltage to input to the GSL393.
Take a look at the flow/pressure/current curve provided by Walbro (below).
If im not mistaken, i should be able to adjust the input voltage until 3A is drawn by the pump, at which point it will flow 57L/Hr (15GPH), more than enough for my application, and 3A is more feasible with the GSs (feable) alternator.
Thoughts?
-Zander
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