Std Fuel Pump Capability

[Warpspeed]

My figures are based on injector flow at that power for correct air fuel ratio, with zero fuel returned to the tank absolutely flat out.

This might not be a good idea, but it is the theoretical absolute maximum limit for the whole fuel system and pump.

A fuel pump supplier might not feel entirely comfortable with this though, and specify the pump at a power level that allows 10% fuel return or some safe margin as a design centre figure. These days they could get sued and be liable, if a particular pump falls a wee bit short of any published specification.

So there is going to be a gap between a safe design figure, and absolute possible maximum.

[Sydneykid]

Hi Zombie, did you read this on the Bosch web site................

"Bosch Fuel Pumps have their flow rates defined in N-Heptane as part of their engineering specification. N-Heptane is a pure chemical and does not have the same viscosity and density as standard petrol. Hence the N-Heptane flow rate figures stated should be used as a general guide for comparison purposes only."

and

"Operating voltage = 12v, test pressures indicated are also suggested maximum operating pressures."

So to use the 044 as an example:

^ at zero pressure using 13.8 volts, it flows 330 litre of Premium unleaded petrol, as per the table.

^ at 5 bar (73.5 PSI) of resistance using 12 volts, it flows 200 litres of N-Heptane as per the Bosch reference.

The reason why I quote 330 litres is, that is what they flow when you test them in the car with no resistance. Warpspeed’s method, although ultimately more accurate for assessing the flow of the whole system, is a bit tricky to use at the race track. So if I have a suspect pump, I can check it by quickly disconnecting the hose at the tank and checking the flow. It has been my experience that when a pump fails (or is failing) it shows up in the free flow test just as well as it does in a resistance (pressure test).

It is worth noting that the hoses from the pump have enough resistance (although quite small) for the pump to work against. In some applications with really large fuel hoses this may not be the case.

Plus as Warpspeed says, there is a difference between the rated flow of the pump and what they actually can do. The manufacturers are conservative by as much as 5% in my experience.

Hope that answers your question.

[Zombie]

I did read that, but didnt understand what it really meant.

I think I get it now, Thanks heaps Sydneykid & others

Adam

[Busky2k]

Hey I just realised, doesnt the skyline have a variable voltage fuel pump? So at idle, the pump wont be running at full bore, so that Warpspeed technique wouldnt be accurate would it? I know for a fact my 200SX doesnt, but yeah...

[Sydneykid]

Hi Busky2K, I wouldn't run an 044 using the standard wiring, it won't handle the current drain. We use the standard wire as the switch on a relay and run a separate power supply from the battery that is capable of handling the 044 current requirements.

[Warpspeed]

This is always a very good thing to do with any major pump upgrade.

Power for the stock pump will come via the ignition switch, and at least one relay, and other assorted crap. These circuits have other loads as well as just the pump, so the voltage drop at the back of the car might be a lot more than you expect.

Rewiring the whole lot is not a practical option. Sydneykid has the right idea (as always !). Use the original pump power wire to energise a pump power relay located at the back near the pump. Then run a really big fat cable right back to the main fuse-box.

The variable pump speed feature will then not work, and you might end up with a noisy pump, but perhaps not if you take special care in mounting it.

But even if you do nothing else, check the voltage right at the pump, it makes a vast difference to pump performance.

Another thing you can do that might not appeal to everyone, is to fit a second pump in series with the stock pump, and leave the stock pump as it is. The second pump relieves the in tank pump of just about all back-pressure, and it will then flow far more, getting twice the flow this way is not unexpected.

The second pump can be in the engine compartment, and hang by its rubber hoses, so there will be no extra noise. Also there are more volts at this end of the car if you use a pump relay as described above. You can even see and get to the damned thing as well.

I am not suggesting this is any better, just different. It certainly works, is easier to do, and it is something else to think about.

[lukits01]

Im also chasing 200rwKw and right now I have my eyes on a Bosch910 pump

I read on previous threads that these arent recommended to be mounted in-tank

What kind of problems would I have if I tried to mount it using the standard brackets?

i.e. replace the standard in-tank pump completely

Has anyone mounted a 910 before? What's the average price on 910s nowadays anyway?