thendawg

iTrader: (2)

So up to this point, Ive actually been using the stock feed line. Im having a pressure drop issue at high rpm which is probably largely due to the stock feed line, but also Im running out of pump. I plan on adding a second DW301 pump later this week, and Ill also be running a new feed line. Im just curious what size feed most people are using? My current return is a 3/8" (-6), so for feed Im trying to see if there are any downsides of going with a 1/2" (-8 )?

Ace83

iTrader: (6)

stock feed line is kinda small, im using it though as my return line.. im using -6 for feed, i dont think you will need -8.. but if you do, im sure dual pumper is a must. what injectors size you have?

trd07tc

iTrader: (-1)

-6 is more than enough.

ScionFred

iTrader: (1)

According to AEM -6 is okay for gasoline up to 500bhp but they recommend -8 for methanol.

http://www.aemelectronics.com/faq.php?cID=1

The following table will help you determine which hose size is correct for your application: These sizes are based on a nominal fuel pressure of 40 psi.

Fuel Delivery Hose Sizes
Gasoline Powered Engines
Up to 499 HP .344” hose -6AN
500 - 799 HP .437” hose -8 AN
900 – 1100 HP .562” hose -10 AN

Methanol Engines
Up to 499 HP .437” hose -8 AN
500 - 799 HP .562” hose -10 AN
900 – 1100 HP .687” hose -12 AN

trd07tc

iTrader: (-1)

methanol and e85 are two very different fuels

ScionFred

iTrader: (1)

True but you still have to flow at least 25% more e85 than gasoline to make the same bhp. So according to AEM, -6AN should be good for ~375 bhp max.

I'm not saying that I agree with that, I really don't know. Just offering AEM's fuel line sizing guide for the OP's consideration.

Ace83

iTrader: (6)

the bigger factor would be the fuel pump and injector before having the need to upgrade to -8.. just my opinion. overkilling the lines before the pump will most likely just cause the fueling to get worst

ScionFred

iTrader: (1)

This is confusing.

1) A single DW301 flows 78gph @50psig and 13.5V
2) 4x 1000cc inj's flow 64gph @50psig
3) The return line should be the same size or larger than the feed line

If the fuel lines are sized correctly, I don't see the need for dual pumps (156gph). Why not use the -6 for feed and add a -8 return? Especially if running dual DW301s. You don't want to pressurize the return line.

Please correct me if I'm wrong. I'm just learning about this subject.

..

paul_dezod

thendawg

iTrader: (2)

Look at what a single DW301 flows at 85-90 psi vs basically 1200cc inj (how the 1000cc's will flow at 65-70 psi after subtracting boost pressure from total fuel pressure) - thats where the prob is. The single DW will flow fine at 50-60 psi all day - but I need 90 psi total fuel pressure

thendawg

iTrader: (2)

Oh an I think Ive solved the dual pump issue - I got a sweet ___ deal on a Kenne Bell Boost-A-Pump. I talked to DW and they confirmed the pump can run all day at 18v without issue - and look at the flow charts - the pump flows almost 50% more at 18v vs 13.5

paul_dezod

90 PSI of FP? Why so much? That's absurd.

thendawg

iTrader: (2)

So yeah for ref -

1000cc inj at 70psi (approx 1200cc flow max) = 76 gal/hr
DW301 at 90psi (70psi+20psi boost) @ 13.5v = 54 gal/hr
DW301 at 90psi (70psi+20psi boost) @ 18v = 90 gal/hr

thendawg

iTrader: (2)

Only running 70 psi base - plus 1:1 rising, so with 21-22 psi itll actually be closer to 92 psi on the rail, however due to the pressurized intake manifold, it will only effectively be 70psi lol - Im making these 1000's go as farrrrrrr as I can lol - unless someone wants to donate some id2000's to my cause :D lol

paul_dezod

Why are you running a base pressure of 70 PSI? 3BAR or 4BAR is more than enough base. Make sure the injectors you are using even capable of running 90 PSI through the screens. Plenty are not.

Ace83

iTrader: (6)

why would you need a huge return? In my understanding the flow rate concerned is from pump to injectors, so it could keep up with the engine fuel requirements.. the fuel going to the return lines are excess fuel dumped by the regulator not used while as it maintains the set fuel pressure.

trd07tc

iTrader: (-1)

thats a lot of FP without a bosch pump and Injector dynamics

ScionFred

iTrader: (1)

I've read from several sources that the return line should be at least the same size or larger than the feed line. The link below explains why much better than I can.

http://www.lmengines.com/fuel_lines




Many people base fuel line sizing based on common misconceptions and customs and as such a fair amount of fuel installations may be fine for a race only application they are unsuited for street applications due to the street duty cycle being on average 20%-30% with idle, city cruise of 15%-20% of the engine power and if the fuel system has reserve these duty cycles would be 5%-10% of the fuel system capacity.

Fuel pressure supply lines are usually adequate for maximum performance, with a preference of 125%-150% fuel line delivery of 100% power to ensure adequate fuel in the event of an unforeseen problem with fuel delivery, i.e. pump speed/voltage/dirt. Fuel pressure lines should be sized to expected capacity and fluid velocity below 4 fps to reduce the Reynolds Number which signifies excess turbulence hence reduced performance.

With such low volume use of the fuel system capacity return fuel lines area usually inadequately sized. The purpose of the return line is for the unused fuel delivered to the engine to be bypassed back to the tank as all constant volume pumps cannot be dead headed. When this fuel is bypassed it experiences a pressure drop and any air dissolved in the fuel or entrained in the fuel boils out forming air bubbles as well as any fuel components vaporizing during this pressure drop. Ideally we want this activity to occur in the fuel line and not in the tank. When the pressure drop in the line is not sufficiently close to ambient the gasses do not condense back into the fuel and the air does not form complete bubbles in the line to escape the fuel in the tank. What does occur with an insufficiently sized return line is that when the bypassed fuel returns to the tank there has not been a sufficient pressure drop in the line and the remaining pressure is discharged in the tank and with it air and gasses discharging forming foam. Return line velocity should preferably be less than pressure line fluid velocity to accomplish the reduction of foam and fuel rail pressure rise.

Fuel line bypasses are commonly called a regulator which is incorrect. A regulator controls pressure on the outlet of the regulator, regardless of the input pressure to the regulator. A fuel bypass function is to bleed off a preset pressure to the outlet; the outlet pressure should be atmospheric and is determined by any restriction downstream. The bypass outlet pressure is ideally ambient atmospheric although return line sizing if too small will increase outlet pressure and added rising fuel pressure line/rail pressures. Another problem with fuel bypasses is the under sizing of the bypass orifice resulting in low flow causing low fuel consumption pressures higher than high fuel consumption pressures causing erratic fuel rail pressures. A larger bypass would be required or a series of bypasses to bypass the total fuel not used at low fuel consumption conditions.

Return line example - If the engine requires 600 lb/hr of fuel at maximum power and is used in low speed/power applications then the return line and bypass needs to return 90% of the fuel with ideally no pressure loss. That would mean a return line sizing equal or larger than the pressure line.

The fuel line sizing calculator is used to determine pressure losses and velocities of fuel by incorporating viscosity, Reynolds Number, D’Arcy-Weisbach Friction Coefficient, Colebrook Equation for friction for the final output of pressure loss in psi. Head pressure is also used and requires the input of the fuel rail elevation above the fuel pump to establish pump pressure to overcome gravity. This calculation can also be used to establish suction head which is the distance from the fuel level to the pump inlet and it can be used for pump performance.

The output of the fuel line sizing calculator is that with the known pressure losses one can consult fuel pump performance charts to properly design the fuel system to engine rated power.

Ace83

iTrader: (6)

good info

trd07tc

iTrader: (-1)

you need an 044 dude