MSefi.com read only forum (Jan.15,2018)

Hi Folks,

Newbie on the long road to microsquirting a 70's air cooled motorcycle engine. I got 2002 GSXR1000 throttle bodies and injectors etc mounted up to the head and am pretty happy with the result so far, now I'm looking at fuel delivery.

Obviously the easiest way is to use the matching GSXR pump, but I have an old style frame and hence a tank shape which is not terribly compatible with the long Gixxer pump, which is designed to sit in the flat bottom of a tank which basically goes down to the crankcase. The GSXR pump is also attractive as it includes the fuel pressure regulator. The most popular choice for an external pump seems to be the MSD unit, but that puppy is rated to 500hp or somthing! Talk about overkill, I presume the gixxer pump is more closely rated to the capacity of a motorcycle engine and would draw less current as a result?

How does the GSXR adjust for MAP? Other regs I've seen regulate fuel rail pressure relative to the manifold pressure, but it appears from (dodgy ebay) photos I've seen would indicate that there is no manifold pressure line coming into the pump/reg unit. So do Suzuki just ignore this variation in diferential presure across the injector?

I don't have easy access to a wrecking yard nearby, also I'm in Australia where the supply of cheap parts via ebay is not so easy so I can't just grab a pump to look at it. If anyone has decent res pics of one of these beasties (pref with ruler for scale reference) it would be great.

Thanks in advance
Steve

I don't have direct experience with the GSXR, but can tell you that it's OK to have the fuel pressure not referenced to manifold pressure. Harley does it on their bikes, and I suspect you're right about the GSXR. Any differences in the fuel flow due to the pressure difference will be compensated for when you tune the VE table.

Fred

Thanks Fred,
I guess if it is compensated by the VE table then all is well. Seems like you might have up to what? 500mbar (abs) in the manifold at times? Maybe less. When you're only running 4 bar (abs) rail pressure that seems like a big difference. But oh well, I have to get hold of one of those pumps first and see if I can make it fit in my tank.
Cheers
Steve

how did you go with the suzuki pump in the end? I have one off a gsxr 600 '06 model. I am thinking of using it in my '86 gsxr 1100 tank. If I do, its a bit of cutting and surgery etc.
were you happy with the fuel injection change over?
Kev

Have you considered using an external inline pump so you dont have to modify your tank? I used a Walbro GSL393 on my Ducati bevel twin. This pump is rated at 160 LPH which is much more than I needed so I slowed it down with a PWM speed controller running about 60% duty cycle. These devices are available in kit form from Jaycar in Australia for about $23.00. I did a flow test with this setup and found that after pressurizing the line and with no injector load, the regulator was bypassing at a rate of about 45 LPH. This setup is working perfectly on the road with the pump running cool and no noticeable increase in fuel temperature. I have no idea what current it is drawing but whwtever it is , my charging system is handling the load easily.

I did consider it. Two reasons why I may persist with an internal tank pump, first is that I have one and secondly is that I have one less thing cluttering the chassis. I do have a concern about filtration and pressure control, have to see how that goes first, early days here, plus I am a newbie at all this. Fingers crossed, thanks for your advice.
Kev

How much did you pay for the pump? Did you have to supply a regulator and fuel filter as well?

Probably not a regulator , thats why you had to slow the pump down, is that right?

From memory the pump cost around US$100.00. The regulator is the standard 3 bar Marelli regulator that was supplied with the 45mm Ducati Monster throttle bodies bought on ebay for US$90.00. The fuel filter is a Napa Gold high pressure filter readily available from multiple automotive parts outlets in the USA for around US$6.00 each.

The main reason for slowing the pump down was to decrease flow in order to overcome a potential problem of the fuel heating as a result of the amount that the regulator would have needed to bypass. Also there is a possibility of the pump drawing less current but I have not measured this for verification. In operation the fuel flow does not seem to have any noticeable increase in temperature and in hindsight probably would not have had, even with full flow. This is mainly due to the pump being mounted in a position that gets a good cooling air flow and also that the bypass is returned high in the tank where the fuel load is cool.

Well its good that the pump runs cool, heat is the big killer I always say. What you have done is interesting. I might decide to go the same way in the end, that would save hacking the tank ( they are getting expensive to buy second hand ) plus the pump would eat up some gas capacity. Thanks for the help.
Good to know there are other options. you can do what you like here, its only you who pay the price. Its your bike to change how you see fit.