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Fuel pump flow rate?
- Thread starter Chuck
- Start date
According to the service manual at idle with the vacuum hose disconnected from the pressure regulator the psi should be between 46 and 53 and with the hose on should be between 36 and 44.
I recently posted a DIY to attach a fuel pressure gauge right on the fuel filter.
I recently posted a DIY to attach a fuel pressure gauge right on the fuel filter.
Confirming that the pressure remains adequate under load is a good very good indication that the fuel pump is supplying enough fuel. :smile:
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Chuck said:
My bad. Gotta improve my reading comprehension skills. Anyway as to your original question, I don't have a clue but I do know that at WOT the typical engine requires 1/2 lb of fuel per HP per hour. Knowing that a gallon of gasoline weighs 6 lbs...........
Assuming 400HP you would require 200 lbs of fuel or 33 gallons per hour.
I'm pretty sure the stock fuel pump is at least capable of that amount. Don't you FI guys use fuel pressure regulators?
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Hugh - I replaced my stock fuel pump (with around 120,000 miles) with a Walbro 255HP pump, and then put a new fuel pressure regulator in place.
Depending on the horsepower you're looking to make that might be overkill, but I've got a great tune putting out a bit less than you with that pump, and am quite happy.
And for the record my fuel pressure idles at 41/42 and rises (1:1) with changing pressure.
Depending on the horsepower you're looking to make that might be overkill, but I've got a great tune putting out a bit less than you with that pump, and am quite happy.
And for the record my fuel pressure idles at 41/42 and rises (1:1) with changing pressure.
burbel said:
My numbers were just an example. if you have a great tune and you're putting out less than me you're in big trouble as my motor is basically stock.
Hugh said:My numbers were just an example. if you have a great tune and you're putting out less than me you're in big trouble as my motor is basically stock.
Ahh my apologies I read but didn't comprehend - I have a habit of doing that after work (or in work, for that matter).
I'm putting 350 to the wheels with my CTSC (high boost).Either way I think the Walbro 255HP (I would recommend Lightning Motorsports, great prices, great support) would be plenty for any FI setup - it removes one more possible failure point, IMO, in any system.
Reminds me of the year+ I drove my NSX with one cylinder not firing... Seemed a bit slow but still ran like a champ.
Damn igniter unit. 
I have the Denso thats rated at 380 LitresPerHour, which has no prob supplying enough to a handful of 500+ WHP NSXs.
Something to keep in mind is that, while related, fuel pressure is not the same as fuel flow. Typically, a fuel pump is rated at various/specific pressures at various/specific flow rates (and even at various/specific voltages).
J
J
On the NSX excess presure is vented with a regulator back to the fuel tank as long as you stay under the presure/volume curve of the pump every thing is good.
From Issue #34 of D Sport:
Fuel Demands:
LPH= Total HP x .3158
Total HP= WHP/.8 (Turbo & NA) or WHP/.7 (SC, parasitic loss)
Therefore, for 600 RWHP = 750 Total HP (Turbo/NA) 237 LPH needed
600 RWHP on SC will need 857 Total HP or 271 LPH
Two other factors need to be considered: Peak boost pressure and voltage (current).
Basically, flow decreases as boost pressures rise. The manufacturer should have flow rates at various pressures(if not a chart). Simply start at their base pressure, usually around 45 psi, add your boost pressure (ie 6 or 9 psi for CTSC) and see what the flow rate is at 51 or 54 psi.
The pumps are also flow rated at a specific voltage. Basically higher voltages yield higher flows. If it is different from your system, find out what the flow rate is for your specific voltage.
They also recommend NOT using two or three pumps, go for one big one instead. Rationale is that if a pump fails, a single system failure will be easily recognized, whereas a two or three pump system can still run with less than optimal conditions (potentially lean at WOT). Also two pumps in parallel do not give the sum total flow rate.
Fuel Demands:
LPH= Total HP x .3158
Total HP= WHP/.8 (Turbo & NA) or WHP/.7 (SC, parasitic loss)
Therefore, for 600 RWHP = 750 Total HP (Turbo/NA) 237 LPH needed
600 RWHP on SC will need 857 Total HP or 271 LPH
Two other factors need to be considered: Peak boost pressure and voltage (current).
Basically, flow decreases as boost pressures rise. The manufacturer should have flow rates at various pressures(if not a chart). Simply start at their base pressure, usually around 45 psi, add your boost pressure (ie 6 or 9 psi for CTSC) and see what the flow rate is at 51 or 54 psi.
The pumps are also flow rated at a specific voltage. Basically higher voltages yield higher flows. If it is different from your system, find out what the flow rate is for your specific voltage.
They also recommend NOT using two or three pumps, go for one big one instead. Rationale is that if a pump fails, a single system failure will be easily recognized, whereas a two or three pump system can still run with less than optimal conditions (potentially lean at WOT). Also two pumps in parallel do not give the sum total flow rate.
I have had difficulty getting the A/F ratio to a sufficiently rich setup with my new low boost CTSC (with header, cat bypass, exhaust) using the fuel regulator adjustment that comes with the kit. The fuel pump appears to be cavitating (the impeller spins and even though the measured overall pressure is 85-90+/- some of the pressure is actually air created by the rotation of an impeller designed to flow at lower rates, as opposed to 100% fuel pressure, thereby starving the motor for moments in time of fuel and causing an excessively high/lean A/F ratio) and cannot therefore keep up with the demands placed on it. Comptech has acknowledged that they have seen a few of the new setups with this sort of issue. My mechanic suggested an Apexi piggyback fuel computer, which is being installed over the next few days. This setup will permit longer pulses of injector opening time (if I am following him correctly, which I may not be) which will offload some burden on the fuel pump which appears unable to keep up. Comptech has expressed agreement with his approach and solution to this issue.
Let me know if anyone else is having a similar problem, and I will let you know how the proposed solution works.
Let me know if anyone else is having a similar problem, and I will let you know how the proposed solution works.
Hugh said:
Hugh , you use a fuel pressure regulator also!:biggrin:
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