Just wondering if anyone had seen any figures for the required fuel flow to produce a certainn BHP?

Just curious as while testing my blocked fuel filter I measured my ZX6R pump as giving out 1L / minute and wondered what that would be good for.

I have seen one suggestion on the internet, which was to multiply BHP x 0.38 to give L/hr - which if correct gives 157 BHP from the pump.

I'd hope you didn't need 1 litre per minute for 157 Bhp as you soon empty your tank

Are you getting ltrs/hour and ltrs/minute mixed up?

A 60L tank gone in one hour, big engine...depressing

You can calculate your theoretical power by calculating the energy in 1 Litre/60 seconds mixed with oxygen at the correct a/f ratio then multiplied by the efficiency of the engine (approximately 0.33). This will give you a power unit (Joule/second or Watts) that you will then have to convert to BHP.

Using the energy in petrol as 42.4 MJ/kg and the density as 0.74 kg/L we get 31.376 MJ/L
multiply this by 1 L/60 s gives us 522.933 KJ/s or 522933 J/s or 522933 W
multiply by 1 BHP/ 0.7457 W gives 701.265 BHP then multiply by efficiency of 0.33 gives a theoretical maximum power of 233.76 BHP, with the units i quickly googled.

But don't forget that your measurement may not have included the resistance of fuel line, filter, injector jets. This could be much lower once all of that is accounted for.

[Edited on 28/5/14 by umgrybab]

quote:

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Originally posted by DW100
I'd hope you didn't need 1 litre per minute for 157 Bhp as you soon empty your tank

Are you getting ltrs/hour and ltrs/minute mixed up?

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quote:

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Originally posted by umgrybab
You can calculate your theoretical power by calculating the energy in 1 Litre/60 seconds mixed with oxygen at the correct a/f ratio then multiplied by the efficiency of the engine (approximately 0.33). This will give you a power unit (Joule/second or Watts) that you will then have to convert to BHP.

Using the energy in petrol as 42.4 MJ/kg and the density as 0.74 kg/L we get 31.376 MJ/L
multiply this by 1 L/60 s gives us 522.933 KJ/s or 522933 J/s or 522933 W
multiply by 1 BHP/ 0.7457 W gives 701.265 BHP then multiply by efficiency of 0.33 gives a theoretical maximum power of 233.76 BHP, with the units i quickly googled.

But don't forget that your measurement may not have included the resistance of fuel line, filter, injector jets. This could be much lower once all of that is accounted for.

[Edited on 28/5/14 by umgrybab]

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If you want to sanity check some numbers then you can see what power output cars have with which fuel injectors.
Injector duty cycle maximum of maybe 80%.

For example gsxr1000 k2. 155bhp. 4x240cc/min injectors. So your pump will easily support 157bhp.

Generally fuel pump outputs are way over specified simply because it is the safe thing to do. Otherwise on the day when the voltage is a bit low, the fuel filter a bit clogged, the air a bit cold, and the driver a bit keen then the fuel pressure drops and it all goes molten pistons.


Have you noticed that if you reverse the polarity on those mitsubishi pumps that they still work, but pump less fuel? Well mine did.

1lt/min would give about 190bhp, with no fuel return. (the formula is 0.19*cc/min=bhp. For the injector example, you get 157 bhp from 960cc/min (4*240cc/min) of injector because you wouldn't run them at 100% duty. I suspect this is about right, or you could start to suffer from misfueling, so you always have a bit of spare duty on the pump.
Regards
Hugh

link

1 litre a minute is a fairly small engine, my 2 litre turbo runs 550cc injectors at 90% at Max load, 2 litres of fuel going a minute no problem.

Also, are you checking the pump loaded at full pressure or just open flow?

quote:

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Originally posted by coyoteboy
1 litre a minute is a fairly small engine, my 2 litre turbo runs 550cc injectors at 90% at Max load, 2 litres of fuel going a minute no problem.

Also, are you checking the pump loaded at full pressure or just open flow?

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Open flow rate will be much higher than at 3 bar, depending on the pump type exactly.

Typical flow chart;



I'm playing around the 300 mark, with some overhead (running lots of fuel top end to keep it cool, could lean out a lot but ~330 is about the known limits for the 550 injectors on this engine).

As my setup is carbs and the zx6r pump is for carbs the pressure is only just a couple of psi.

Was curious as to the fuel pump capacity as I plan to transfer my setup from my 1800 pinto over to a Duratec when I swap engines.

My bad, assumed EFI! Should be fine then!