The three most common Walbro pumps are compared. The 190L/Hr, 255L/Hr, and the High Output 255L/Hr. They are tested at "stock" FPR of 43psi, "15psi of boost" or 58psi, and "30psi of boost" or 73psi.

Cross referencing the flow data with the chart in Corky Bell's book "Maximum Boost", we can obtain the following data:

190L/Hr pump is good for ~280HP
255L/Hr pump is good for ~510HP
255HP pump is good for ~610HP

All of the source links are at the bottom of this post.


[Pump Model] [Battery Voltage] [Test Pressure] [Current Draw] [Flow]

Walbro "190" LPH GSS-250 12.5V 43psi 6.0amps 168.45 Ltr/Hr
Walbro "190" LPH GSS-250 12.5V 58psi 7.0amps 145.11 Ltr/Hr
Walbro "190" LPH GSS-250 12.5V 73psi 8.0amps 88.96 Ltr/Hr

Walbro "190" LPH GSS-250 14.0V 43psi 6.5amps 208.83 Ltr/Hr
Walbro "190" LPH GSS-250 14.0V 58psi 7.5amps 162.78 Ltr/Hr
Walbro "190" LPH GSS-250 14.0V 73psi 9.5amps 104.10 Ltr/Hr


Walbro "255" LPH GSS-317 12.5V 43psi 7.5amps 229.02 Ltr/Hr
Walbro "255" LPH GSS-317 12.5V 58psi 9.0amps 201.89 Ltr/Hr
Walbro "255" LPH GSS-317 12.5V 73psi 10.5amps 147.00 Ltr/Hr

Walbro "255" LPH GSS-317 14.0V 43psi 8.0amps 261.83 Ltr/Hr
Walbro "255" LPH GSS-317 14.0V 58psi 10amps 230.92 Ltr/Hr
Walbro "255" LPH GSS-317 14.0V 73psi 11.5amps 182.97 Ltr/Hr


Walbro "255 High Pressure" LPH GSS-342 12.5V 43psi 7amps 233.4 Ltr/Hr
Walbro "255 High Pressure" LPH GSS-342 12.5V 58psi 9amps 210.10 Ltr/Hr
Walbro "255 High Pressure" LPH GSS-342 12.5V 73psi 10.5amps 189.3 Ltr/Hr

Walbro "255 High Pressure" LPH GSS-342 14.0V 43psi 8amps 264.4 Ltr/Hr
Walbro "255 High Pressure" LPH GSS-342 14.0V 58psi 9.5amps 242.9 Ltr/Hr
Walbro "255 High Pressure" LPH GSS-342 14.0V 73psi 11amps 220.8 Ltr/Hr


Check this graph (http://www.stealth316.com/images/flowtest-walbro.gif) out too just to see how much boosting the fuel pump's voltage can increase flow. This shows just how well a Boost-A-Pump can work.


Interesting note about using a stock FPR...

"Note, however, that using a 255 or 255HP pump on a DSM will probably require an adjustable aftermarket Fuel Pressure Regulator, especially if using larger injectors, in order to get the fuel pressure curve more linear. Any very high flow pump can overrun the tiny stock FPR, causing the base fuel pressure to be higher, and making the fuel curve nonlinear, making the ECU's control of the fuel more difficult. When coupled with larger injectors, you can basically flood the engine with fuel, causing your car to run super-rich (black smoke out the tailpipe almost all the time), lowering mpg and power. Installing an adj FPR allows you to dial the base fuel pressure back to stock, maintain a linear fuel pressure curve, and gain back mpg and power."


Links to source pages:
http://www.stealth316.com/2-fuelpumpguide.htm#j5
http://www.roadraceengineering.com/f...pflowrates.htm


Source for fuel pumps:
http://autoperformanceengineering.com/html/fppumps.html
(I don't know about the Duratec, but the Zetec uses the GSS250, F20000141, GSS317, or the GSS342)

 

good info man

 

I don't kno what the hell i just read...hahahahha

 

devon, it's ok.

fuel pumps are tested at the highest voltage and lowest possible pressure. hence the "255-190" numbers they get. the higher the pressure the lower the overall volume that is actually flowed.

what i would really like to know is the numbers off the stock lsj pump.

 

Thanks man. So i guess the above is 'good info?'

 

Found out this on the stock fuel pump

Additional features: high pressure ( 56 psi ) fuel pump

This is the source
http://fastfieros.com/turnkey_soluti...ne_install.htm

 

pressure is irrelivant to me.
gph, or l/hr is what matters

 

Pressure should matter to you. The higher the pressure the more the injectors will flow. Also in a boosted application, the manifold pressure pushes back against the injectors creating a lower differential between the manifold and fuel rail pressures, essentially making the injectors smaller. That is why a 2.8" pulley requires 60# injectors even though 42# injectors should be good for ~125hp each.

Also the higher the pressure the lower the volume flow rate. Notice that as the pressure increases, the volume decreases.

Since we don't have a return fuel system, modification will need to be made for a return line and a regulator to be installed.

 

I do have one installed in my car.

 

Yeah I saw that in your sig. How did you do it?

 

X2...

 

you just talked in circles...the volume is what matters

 

Yes the volume is important, but the pressure is just as important. The higher the pressure the less the pump flows, but the more the injectors flow. It takes pressure to get the fuel into the engine and that is why it is also very important.

 

I'll make a post on this now. Look for Return-style fuel system for 2.0 LSJ.

https://www.cobaltss.net/forums/show...28#post1740728

 

conflicting info

which reverts me back to pressure is irrelivant to me.

 

IT's funny how alot of my stealth stuff can be used or thought about for the cobalt too. I have a dual walbro setup in my stealth with an adjustable FPR. works great!!! and jeff lucius the guy who created stealth316.com is smart as hell! there's tons of great info on that site.

 

For the 3rd time. The injectors need high pressure to deliver fuel, higher pressure results in lower pump efficiency(pump volume). Just like a turbo or a super, you have to find a pump that will deliver enough volume at the pressure you need.

 

Wow I just got thrown for a loop and do not know which way is up now...hold on I need a beer to finish reading whats next.....

 

what happens when the car runs 80 psi of fuel pressure?

hi, the volume the pump can flow goes down. what happens when the volume gets too low? you blow **** up. is it because of pressure? yulp. too much can kill an engine for the simple fact it can not sustain the volume needed for the engine to be happy with.

why do people change pumps? it's NOT because of pressure, it's simply because the fuel pump can not sustain the required volume. what happens when you turn the pressure down? the flow rate levels out, and all is happy. i do understand what you're getting at, but in my world, pressure is irrelivant.

 

A fuel system is just that - a system! All the pieces must work together. The current trend is to run a pump that is much bigger than should be required to compensate for deficiencies within the system. Simply buying and installing the biggest pump you can find will not be enough if the rest of the system is poorly thought out. The same can be true buying a pump based upon price or what you think is enough fuel pump. Either deficiency can also easily drain the wallet if you run out of fuel and start damaging engine parts ... not to mention losing races!

This article will focus on electric fuel pumps. Mechanical fuel pumps are not worth the effort unless you are mandated by the rules of your class (as in most circle track applications). You can use the same basic knowledge with your mechanical fuel pump in regards to requirements and fuel regulator choices.

Fuel pumps are generally rated in gallons per hour (or GPH). Mallory offers pumps rated at 70, 110, 140, 250 and 500 GPH. All of the Mallory pumps are of gerotor type which makes them quieter and more efficient than rotary vane style pumps. However, it is mandatory that a fuel filter be installed between the fuel cell (or tank) and the pump. The higher efficiency of the gerotor pump also is less tolerant of garbage getting into it ... always run a filter before the pump! You should also have a filter just before your carburetor or injector rail as well.

A typical engine uses 0.5 pounds of fuel (gasoline) per hour to make each horsepower. Gasoline weighs in at approximately 6 pounds per gallon. To calculate fuel consumption let me show you by example. Lets say we have a 400 HP engine (or nitrous system) and we will use the following formula:

400 HP X 0.5__ X 1 gal = 33 GPH
HP per hour 6 lb.


If you installed a pump rated at 33 GPH on a 400 HP Nitrous system the engine would experience severe fuel starvation and your wallet would cringe in "empty" pain! WHY?

There are several reasons ... However, the main reason is the way that pumps are rated. Fuel pumps are rated at "zero" pressure (also known as "free flow"). Rating a pump at zero pressure is useless because the pump will never be at zero pressure when it is operating in the vehicle. As fuel pressure increases, the fuel pump slows down and fuel output is reduced. If you use a standard "dead-head" type regulator, the pump may be forced to produce as much as 25 PSI. At 25 PSI, the actual output GPH of the pump is much less than at "free flow".




All of this makes choosing a pump size difficult. You may use the following as a fuel pump "rule of thumb". Additionally, it is a good idea to give your system a bit of safety cushion. I always run a pump one size larger than I need just for insurance.

For Dead-Head type regulators:
Multiply maximum horsepower by .23 to calculate minimum pump size in "free flow" GPH.
Example: 400 HP x .23 = 91 GPH "free flow"

For Return-Style regulators:
Multiply maximum horsepower by .17 to calculate minimum pump size in "free flow" GPH.
Example: 400 HP x .17 = 68 GPH "free flow"

These minimum pump sizes assume that the fuel system is equipped with fuel lines of adequate size. If the fuel lines are too small (or if there are a lot of restrictive fittings in the system) a larger pump may be required to satisfy the fuel demand of the engine. The minimum fuel line size (from the pump to the regulator) is dependent on the horsepower output of the engine (and/or Nitrous system) regardless of the size of the pump.

Use these figures as a fuel line sizing standard:

* Up to 250HP = 5/16" or -04 AN
* Up to 375HP = 3/8" or -06 AN
* Up to 550HP = 1/2" or -08 AN
* Up to 800HP = 5/8" or -10 AN
* Up to 1200HP = 3/4" or -12 AN

If you use a return-style regulator, you will also need a return line from the regulator back to the tank. The size of the return line is dependent on the size of the pump you are using, regardless of the engine's horsepower output. The return line must have limited or NO pressure in it. In most cases, the minimum return line size will match that of the supply line, but a larger return line is sometimes preferred.

Use these ratings to decide your return line sizing based upon fuel pump output:

* Up to 45GPH = 5/16" or -04 AN
* Up to 90GPH = 3/8" or -06 AN
* Up to 180GPH = 1/2" or -08 AN
* Up to 360GPH = 5/8" or -10 AN
* up to 720GPH = 3/4"or -12 AN

Mounting the fuel pump takes thought as well. You MUST mount the fuel pump as low as possible and as close to the fuel cell (or tank) as possible as well. DO NOT mount the pump above the fuel tank.

NOTE: At many times I'm asked about the actual angle of mounting the pump. I'm asked if the pump must be mounted upright. Take it this way, if the seals in the pump happen to fail, would you want fuel leaking into an electric motor or simply onto the ground? Well if you like fires ...

Mount the fuel pressure regulator as close to the engine as possible. DO NOT use restrictive fittings, especially sharp 90ş or "T" fittings. If you must use a 90ş or "T" fitting, use the tube style fittings from Earl's, Russell, Goodridge, Bonaco and others. See Below...


The GOOD and the BADbad example of a fuel fitting

Good example of a Racing Designed 90* fuel fitting Of course the first shown below is what you want. The restriction of the fittings (second fitting) can be hazardous to your race engine and the consistent ability to Win Races..




Regulators and the Benefits of Return-Style Systems:

One of the biggest restrictions in most fuel systems is the "dead-head' regulator. Dead-head regulators are popular because you do not need to install a return line. However, they are not only more restrictive but also create several other problems that can be eliminated with a return-style regulator. Dead-head regulators also have a higher failure rate than return-style regulators.

Mallory offers both dead-head and return-style regulators. Both types are available in large and also small versions though you should never run the small regulators on pumps rated higher than 180GPH.
Dead-head regulators regulate pressure by starting and stopping flow. Return regulators regulate pressure by sending excess fuel back to the tank in a continuous cycle.

Because a dead-head regulator starts and stops flow, fuel pressure between the pump at regulator is higher than the pressure between the regulator and the carb (or injectors). However, if the pressure gets too high, it can and will damage the fuel pump. Therefore, the pressure coming out of the pump is limited by a device built into the pump called a bypass. Low pressure pumps are limited to less than 9PSI and should not be used with dead-head regulators. High pressure pumps are limited to a pressure of between 10 and 25PSI.

Not only can the fuel pumps being used with dead head regulators fail because of pressure issues, but pumps with dead head regulators also run hotter do not last as long as when connected to to a return-style system because it is the fuel that cools the pump. Pounding the fuel because it can not move creates more heat.

The Mallory 70 and 110 pumps are low pressure pumps that can be used without a regulator for the street or with a return-style regulator for racing. Mallory 140, 250 and 500 series pumps are high pressure/high volume and must be used with a regulator (dead-head or return-style).

The bypass in the pump can malfunction. This can cause the pressure to drop or increase so much that the pump motor fails. Even if the bypass in the pump is working correctly, it is still possible to have a pressure drop with a dead-head regulator, even when using a large pump. See the image below:


At idle, gauge #1 will read 10PSI where gauge #2 will read 8 PSI. At full throttle, the increase in fuel flow will create a pressure drop between the pump and the regulator. The amount of pressure drop depends on the restriction in the fuel line ... a 4 PSI drop is not uncommon. Gauge #1 will now read 6PSI and because a dead-head regulator cannot raise the pressure, gauge #2 will also now read at 6PSI. The result is a 2 PSI pressure drop at the carb or Nitrous even though a very large pump may be in use.

NOTE: When using a dead-head regulator, a second gauge should be installed just before the regulator. This will allow you to check that the pressure before the regulator stays higher than the set pressure.

Most race pumps have the bypass set very high (14-25 PSI) to avoid this problem. However, this creates another problem. The higher bypass pressure makes the pump work harder and draw more amperage. In fact, the pump works just as hard at idle as it does at full throttle down the track! This is one of the main causes of early pump failure. To counteract this problem of high amperage draw, many companies manufacture voltage reducers for street cars to slow the pump down and increase the life of the pump.


A few "WHYS" to return-style regulators:

This is a profound point to be made when I (or your engine builder, carb builder or fuel pump manufacturer) tell you to run ONLY a return-style system on your vehicles.

* You can avoid these headaches (especially when the pump dies just before a final-round elimination and you do not have enough time on your hot-lap, or for that matter a spare pump, to fix it in time to race ... Loss By Default!) by running a return-style (or bypass) regulator.
* The bypass in the pump is plugged or disabled when you run a return-style regulator so there is no chance of it failing.
* The pressure just before and after the pump is always the same so there is no need for two gauges.
* The return regulator has complete control over the pump pressure and will automatically compensate for pressure drop in the fuel line.



If there is s 2 PSI pressure drop between the pump and the regulator, the return-style regulator will force the pump to produce 10 PSI. If there is s 4 PSI drop, the pump will be forced to produce 12 PSI. In either case, the pressure at the regulator will remain at 8 PSI (or whatever you set it at). The pump will also live longer since it is only producing 10-12 PSI instead of 14-25 PSI. This means that a voltage reducer is not needed, even on a street car.

Fuel pressure regulators suffer from something called "recovery time". Recovery time is explained as the amount of time it takes the regulator to react to changes such as a sudden increase in fuel demand (as when you jump on the throttle or hit the Nitrous button). Return regulators react much quicker for several reasons. Return regulators allow the fuel to flow straight through without making a 90° turn. With a return regulator the fuel doesn't have to make it's way around the plunger like it does in a dead-head regulator. Just before you jump on the throttle (or hit the nitrous button), the fuel in a dead head system is barely moving. In a return system, the fuel is constantly moving from the rear of the car to the front and back again. This means that the fuel already has momentum, which reduces recovery time. This movement of the fuel also keeps the pump cooler and reduces vapor lock.


"We never race any hot tracks in the heat of summer, do we?"

Dead-head regulators can also cause "creep" which means the fuel pressure tends to slowly increase. Return regulators cannot creep.



Nitrous systems are very sensitive to fuel pressure fluctuations. It is highly recommended that you run two independent fuel systems when using Nitrous (preferably with return-style regulators). Two small systems with small pumps, fuel lines and regulators are usually cheaper than one large system anyway. If you must use one large system, use two dead-head regulators installed in parallel, not in series. NEVER use two regulators in a system with a return-style regulator! Any fuel system with a return regulator must have only one regulator.



Fuel System Designs For Engines With Nitrous:

 

Wow I now need a second beer

 

fax me some too

 

LMAO...sorry I am lost when it comes to stuff like that I would rather explain what I am trying to do to someone who is knowledgable and ask them for thier advice...It has not steered me wrong yet.

 

90% of it is theory. 5% is truth, the other 5% is someones mistake.