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fuel pump for 450bhp

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Old 07 October 2018, 07:43 AM
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the shreksta
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Default fuel pump for 450bhp

as i will be spending a considerable amount having a fresh build for circa 450+bhp i will be swapping out my 5 year old walbro 255 for a fresh one, i see they do a walbro400 would that be better suited to my needs?

thanks
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Old 07 October 2018, 09:04 AM
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Bosch 044
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Old 07 October 2018, 09:12 AM
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Originally Posted by scooby2.5maz View Post
Bosch 044
thanks buddy will look into them
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Old 07 October 2018, 03:15 PM
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Aeromotive 340 or Walbro 450
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Old 08 October 2018, 09:13 AM
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RCM340
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Old 08 October 2018, 09:41 AM
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stockcar
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you dont need a Bosch 04 or a Walbro 450 at that level - a GENUINE walbro 255 or RCM 340 will happily cope........
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Old 08 October 2018, 02:46 PM
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Originally Posted by stockcar View Post
you dont need a Bosch 04 or a Walbro 450 at that level - a GENUINE walbro 255 or RCM 340 will happily cope........
ok alyn thanks
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Old 08 October 2018, 10:14 PM
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Scoobyworx 340 Collosus sure that & rcm all the same
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Old 10 October 2018, 09:13 AM
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rsjohn
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What pump if OP decided to go 500bhp, surely best to slightly overdo pump not only for future if he wants to go slightly more than 450 but for reliability also?
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Old 10 October 2018, 10:39 AM
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the 340 pump flow capacity is 340 litres per hour, that's 75 gallons per hour. just to get some sort of perspective into it lol
If still in any doubt I would install an FPR with guage.
Trev
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Old 10 October 2018, 12:14 PM
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Fuel regulator won't help. Oversizing the pump, would cause over-fuelling at wide open throttle (open loop uses the map). Idling/part throttle uses the closed loop/oxygen sensor compensation.

Rough pump size calculation: MAX HP x 0.65 (petrol turbo) divide by 1.585 = ?lph
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Old 10 October 2018, 01:34 PM
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Originally Posted by 2pot View Post
Fuel regulator won't help. Oversizing the pump, would cause over-fuelling at wide open throttle (open loop uses the map). Idling/part throttle uses the closed loop/oxygen sensor compensation.

Rough pump size calculation: MAX HP x 0.65 (petrol turbo) divide by 1.585 = ?lph
How does oversizing a pump cause over fuelling? Would the fuel pressure regulator not keep the fuel at the desired pressure?
I have been running a Bosch 044 from 280bhp right up 400bhp as I have upgraded various components all while using the factory pressure regulator with no I'll effects.
Not disagreeing as I don't know myself, genuine question.
cheers.
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Old 10 October 2018, 02:09 PM
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Originally Posted by 2pot View Post
Fuel regulator won't help. Oversizing the pump, would cause over-fuelling at wide open throttle (open loop uses the map). Idling/part throttle uses the closed loop/oxygen sensor compensation.

Rough pump size calculation: MAX HP x 0.65 (petrol turbo) divide by 1.585 = ?lph
so calculation gives roughly 205 litre flow needed for 500hp
my wrx standard pump leaned out at around 430, think the pump was rated 190lph also may have been on 20%meth at the time but memory not good now.
granted fpr no good if pump can't supply the fuel.
Trev

Last edited by trevsjwood; 10 October 2018 at 02:11 PM.
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Old 10 October 2018, 02:28 PM
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Originally Posted by trevsjwood View Post
so calculation gives roughly 205 litre flow needed for 500hp
my wrx standard pump leaned out at around 430, think the pump was rated 190lph also may have been on 20%meth at the time but memory not good now.
granted fpr no good if pump can't supply the fuel.
Trev
Meth content needs a higher multiplier. Meth, on its own, is x 1.9
wrx 03-04 fuel pump approx 130lph
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Old 10 October 2018, 03:00 PM
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Originally Posted by ianbott View Post
How does oversizing a pump cause over fuelling? Would the fuel pressure regulator not keep the fuel at the desired pressure?
I have been running a Bosch 044 from 280bhp right up 400bhp as I have upgraded various components all while using the factory pressure regulator with no I'll effects.
Not disagreeing as I don't know myself, genuine question.
cheers.
You can map for an unnecessarily large fuel pump, at wide open throttle (open loop). But your still drawing excess current and heating the fuel.
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Old 10 October 2018, 08:16 PM
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ianbott
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Originally Posted by 2pot View Post
You can map for an unnecessarily large fuel pump, at wide open throttle (open loop). But your still drawing excess current and heating the fuel.
Current draw is minimal really, plus it's not at wide open throttle that much realistically and I have it running through the standard Subaru fuel pump controller but thanks for the explanation, still trying to understand open and closed loop fuelling lol.
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Old 10 October 2018, 08:39 PM
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Originally Posted by ianbott View Post
Current draw is minimal really, plus it's not at wide open throttle that much realistically and I have it running through the standard Subaru fuel pump controller but thanks for the explanation, still trying to understand open and closed loop fuelling lol.
It's the unnecessary increase in fuel flow, defeating the fuel pressure regulator orifice, and affecting the pressure drop across the injectors. The absorbed heat, in the increased, unused, fuel is returned to the tank, to be re-cycled.
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Old 10 October 2018, 09:40 PM
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I have an external bosch 044 which is part of a swirl pot system I have connected up for track only, the intank pump acting as a lift pump to swirl pot. With swirlpot/bosch 044 connected up the fuel pressure rises by about 0.3bar over when just using the normal system, that's at tickover. I adjust it back to the required pressure but the over supply must be causing the pressure to rise in the first place?
Trev

Last edited by trevsjwood; 10 October 2018 at 09:42 PM.
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Old 11 October 2018, 06:53 PM
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Hmm, I have a walbro 255 (genuine, from lateral), and also a genuine 044 pump on the shelf .. I was going to swap them before mapping (and run the 044 in tank), but are we now saying a 255 will support up to 450bhp?

im only aiming for 400, so for hassle factor, I'd like to stay with the current setup, as mapping is a week and a bit away.
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Old 11 October 2018, 06:54 PM
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Also I imagine it makes a difference at what boost pressure the hp is achieved, as the pump would flow less fuel at 3 bar static + 2 bar boost, as opposed to say 3 bar static and 1 bar.
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Old 11 October 2018, 08:25 PM
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the pump most would have at that level is bang in between the two you have lol.
It's got to be a personal choice but if the 255 was in good shape I personally would keep your present set-up, rather than running the big Bosch all the time.
If at a later date you decided up the power with meth for instance re consider then.
Trev
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Old 12 October 2018, 01:35 PM
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Primary pump is fine / any higher or indeed taking the car on track then a lift pump with a swirl system would be advised or you could hunt for a spec c anti surge pump assembly
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Old 12 October 2018, 07:43 PM
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bugeyestuart
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Got an RCM340 on my car and was told it would be good for 450bhp
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