EFI Conversion Hurdle: The Fuel Pump - One possible Solution.

[the_zander]

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

 

[mike-s]

Interesting, a mod ive always been interested in watching unfold

 

[niclpnut]

What about from a V65 magna. They had a fuel pump that was inline external of the tank. Maybe modify something like that for your purposes?

#1 is the pump.

Fuel comes down from tank through #4 fuel filter into pump.

Round $100 new or there seem to be some floating around on ebay.


Nic

 

[Dave8338]

Not sure of the pressure it could provide but it may ba an option. :-s

http://www.bikebandit.com/houseofmotorcycles/1993-yamaha-virago-xv1100e/o/m7938#sch123474

 

[Don-lo]

The fuel pumps used to fill carbs are low pressure, and you can get 2 kinds of those at autozone (can't remember the psi).

You should be able to make a secondary fuel holding tank just for mounting your standard in-tank efi fuel pump. It would basically be a well-sealed vertical cylinder (4" wide?) sitting downhill from the gas tank.

I hope you realize that any modern throttle body is HUGE compared to a GS750 intake tract. That may play havoc with the efi. A later GS850/1000/1100 (8 valve) head has much bigger ports, and work better.

 

[cal_look_zero]

I used a generic riding lawnmower inline pump on my 69 vw bug which required a lower flow rate/psi than any other 12v pump I had found. $20 online.

 

[Smitty86]

I have a 1980 GS 750 that I've mixed up with a 02 R6 I have the motor out to finish fab and paint on the frame and I remember I have a set of R1 fuel injected throttle body and it fits so if I get an aftermarket power commander can I make this work

 

[salty_monk]

When I used to build Kit cars the "go to" for people converting from carbs to FI was to use a pump/accumulator etc assembly from a Golf GTI..... One of the older models I believe, Mark 2 or Mark 3 something like that.

 

[GSX1100 dreamn]

You could use the 650 Bandit.

I have 1250 Bandit on my 1260 Kat, the throttle bodies fit.

4 years commuting.

 

[GSX1100 dreamn]

Adapted 1250 bandit pump.

 

[GSX1100 dreamn]

enter atleast 15 cahracters

 

[GSX1100 dreamn]

https://www.thegsresources.com/_forum/forum/technical-forums/carb-fuel-exhaust/88712-kat-efi

 

[GSX1100 dreamn]

If the link works you might get some ideas, I am using the standard Bandit ECU.

 

[GSX1100 dreamn]

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

For EFI it's not flow it is pressure you need, more specifically 43PSI is the normal for EFI bikes.