Jump to content

Fuel injection conversion


Recommended Posts

Hi everyone,

I'm new on here so please be gentle. 

I'm doing an efi conversion on a bandit 12, but my question is relevant to any EFI conversion. My question is does it matter if the diameter of my fuel hoses / fittings are different throughout the system. So my fuel pump supplies the fuel rail via AN6 hose, then the rail itself is 4mm ID, then it widens up again to AN6 to supply the pressure regulator. I'm thinking the change in hose diameter will make the pressure regulator see a lower pressure than the fuel rail does and so allow the fuel rail too much pressure?

It would make more sense to me to run the regulator before the rail but I have read this is a bad idea. 

Any thoughts welcome

Thanks for your time


Link to post

Dan it wont make a lot of difference . Normally pump into the rail then regulator . Idea you keep a constant fuel pressure in the rail . Need to make sure you can supply enough fuel for the power the engine is making ( pump and lines )and flow enough back to the tank when running at slow speeds . I like to fit a return line either equal or slightly larger to the supply.

Link to post

Hi colinworth, thanks for your reply. 

The rail is lifted directly from a 01 gsxr 1000, so the 4mm sections I was talking about are presumably ample for flowing enough fuel for ~160bhp. However as this rail is from a return less system, I was just worried the change of diameter would mean different sections experienced different pressures. I just don't want to get it together and realise it doesn't work :)

The pump I'm using is a walbro gsl393 which does upto 155 lph. Do you think those 4mm sections are wide enough for that volume? If they're not does the pump just fry itself?

Thanks again




Link to post

By my rough maths 155LpH equates to about 515hp and I doubt a 4mm pipe will allow that sort of flow!

Allowing some headroom over the std 160hp figure - say 250 - the line is maybe capable of flowing 75LpH. So you either change the fuel rail for a bigger one (as presently it may pose more of a restriction than the regulator!) or swop to a lesser capacity pump (subject to your power output expectations?) 

If the fuel flow is severely restricted out of the pump it could overheat a) the pump or b) the fuel - or both!

I know on my bike a Teflon -6 pipe will flow sufficient fuel for 350 - 400hp, to go higher, safely, i'll need teflon -8

Link to post

Thanks that's helpful. Looks like I'm gonna have to make some changes. There's probably room for me to drill out the 4mm pieces to 6mm however on closer inspection, the pump outlet is M10 and with the AN6 adapter screwed in, there is only 5mm exposed for fuel to flow to I suppose its pointless going above that. Odd as I wouldn't have thought 5mm would support 155 lph either


Link to post

I guess it will be fine even without any changes. Actually you can get surprising amounts of flow through small orifices if length of restricted part is short. For longer length hoses and pipes it's more important to keep cross section large enough. Just for an anecdote, I have seen nitro bikes that have a single AN6 hose to feed all the fuel for the engine, about 1000hp worth of nitro! Although I guess that causes some noticeable pressure loss but compared to that 155lph through 4mm rail is nothing :)

On the other hand placing the regulator before the fuel rail should work just fine as well. Most of the factory installations use this arrangement.

Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...