Pump Pressure / Flow / Injectors

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hendo#1

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Can someone please explain to me the correlation between pump pressure / flow and injector sizes?

Please correct me, but if I have a healthy fuel pump already, why is it necessary to put in an uprated pump when you could just size bigger injectors and have it correctly mapped to suit? For a hybrid set up for example.

Or have I completely missed the point?
 
pump will supply a flowrate of X
exceed the requirements of said flowrate you need a higher flowing pump

"healthy" means nothing really.
introduce boost to the rising rate fpr which is 3bar, and then ask for an example 1.6bar boost, the fuel pump needs to be able to deliver 4.6bar fuel pressure and flow.. example flow vs pressure table below for an uprated pump to show relationship.

std in tank pump can delivert 3.3ltr/min no load, but much less ( i dont have figures) when you ask for pressure and flow.
usually stock pumps begin to not keep up in low 300bhp level in my experience of them.

larger injectors are required on hybrids anyhow.. usually 550cc bosch used.

FP-265lph-fwd-pump-flowrating.JPG
 
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OK, it makes a bit more sense now. As the pressure rises the flow rate reduces.

I think I'm getting flow and pressure mixed up.

If your fuel pump set-up was borderline on a set of 550cc injectors, its certainly not going to keep a 1000cc set of injectors happy...

Am I about right?
 
hendo#1 said:
OK, it makes a bit more sense now. As the pressure rises the flow rate reduces.

I think I'm getting flow and pressure mixed up.

If your fuel pump set-up was borderline on a set of 550cc injectors, its certainly not going to keep a 1000cc set of injectors happy...

Am I about right?
Click to expand...
If the pump set up is adequate then yes it would be fine going up to 1000cc.
If the pump system isn't adequate to support 1000cc/min at 4-5bar then you will see really high duty cycles at not a lot of boost/power.

The two systems go hand in hand. You don't throw 1000cc injectors on with a stock setup, you must upgrade both so they support each other and the fuel supply/power you're after
 
hendo#1 said:
OK, it makes a bit more sense now. As the pressure rises the flow rate reduces.

I think I'm getting flow and pressure mixed up.

If your fuel pump set-up was borderline on a set of 550cc injectors, its certainly not going to keep a 1000cc set of injectors happy...

Am I about right?
Click to expand...
correct.
 
So why do people upgrade to a 4bar fpr if it will flow less?
 
vtecas said:
So why do people upgrade to a 4bar fpr if it will flow less?
Click to expand...

It needs to be mapped to support the flow else the ECU pulls it back out... plus there are other factors to consider like the flow rate and pressure capability of the pump..

I ran a 4bar FPR and 550cc injectors which gave me around 630cc but the map was scaled for 630cc injectors... the map has no concept of fuel pressure rate.. std maps are scale for std injectors at 3bar... the ecu is blind to you fitting a 4bar FPR so will fuel for what it knows... it will then see that AFR is too rich for the amount of fuel its calculated and adapt accordingly reverting back to a state it can calculate correctly..

4bar FPR is quite taxing on a std pump though... I still run a 4bar but I have an inline pump thats man enough to support it

<tuffty/>
 
vtecas said:
So why do people upgrade to a 4bar fpr if it will flow less?
Click to expand...
It will flow more (IF) the pump can flow more... ~15% more

BUT you are applying more load on the pump so its still the fpr base line pressure +boost which the pump has to deliver

Run 1 bar boost on stock fpr you are already running pump at 4bar
 
So I'm running 1.3 bar of boost plus the 4 bar fpr.... My pump is going to die soon :blush:
 
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