Inn-Tune

iTrader: (33)

I decided to make another tech thread since some people apreciated the intercooler comparison.

First some notes on fuel pump sizing:
When looking at the specs of a fuel pump, be sure to note voltage and fuel pressure for a given flow rate. Pump flow and voltage are directly proportional, while flow and fuel pressure have an inverse relationship. To put it simply...as voltage to the pump goes down, so does the pump's potential output. As fuel pressure increases, the pump's potential output decreases due to the pressure it must overcome.

Many pumps are rated at 0 psi, which is a rather useless figure. 200 GPH at 0 psi is around 144 GPH at 4 bar which would be typical for a car running 1 bar of boost (with a manifold referenced FPR) on top of a standard 3 bar static pressure. At 2 bar of boost you'd be down around 125 GPH.

When sizing your pump it's important to know the supply voltage it will be receiving. Does voltage to the pump drop when you turn on the A/C or other accessories? Find out what your system really produces at a minimum and how much the pump flows
at that voltage. Prepare for the worst case scenario and do what you can to ensure that the pump gets good constant voltage.

Here's a link to some popular pumps' flow data (Walbro, Denso, etc.):
http://www.stealth316.com/2-fuelpumpguide.htm

You can see that the Denso 310 pump gives you a touch more headroom than a wally 255, but only up to 22 psi, at which point the Walbro actually outflows it. I'd switch up from a single Walbro or Denso 310lph around 550 hp. You can run twins or switch to an external above that. Again these are just guidelines and they depend on your setup. If you're naturally aspirated, you can go further than FI guys on the same pump due to lower BSFC and generally lower fuel pressure. Those running high boost require more pump capacity than those running low boost. Remember that as I mentioned above, fuel pump flow decreases as fuel pressure increases. I know you're used to thinking about bumping up the fuel pressure to get more fuel in the engine through the same injector size, but the increased pressure makes it harder for the fuel pump to flow. Forced induction applications generally use 1:1 regulators for that exact reason. As manifold pressure increases it decreases injector flow, unless the pressure behind the injector is equalized (above base pressure) with manifold pressure.

One nice thing about the Denso pumps (for some people) is that they're quiet. Many of you already know this, but Walbros are louder than stock. Also the Denso is OEM quality and they're known to generally last longer than Walbros. Denso happens to supply the OEM Evo pump, it simply has a lesser flow capacity of 190 lph. The Denso 310 pump does cost nearly 3 times as much as the Walbro, so keep that in mind.

If you go to a big external pump, a pump controller is key to avoid fuel overheating and pump damage, especially for a street driven car which isn't always at or near maximum effort. If you're running twin Walbros or Densos, some engine management systems (such as AEM EMS) allow you to automatically kick on the secondary pump when certain conditions are met. For instance on the EMS I kick the secondary pump on above a certain manifold pressure. This serves a similar purpose as the external pump controller by pumping less fuel when it's not needed. This decreases flow through the return system and excess recirculation, which keeps fuel and pump heating to a minimum.

Before someone says....but this guy made this much HP on this pump so you're wrong...people make power with a RRFPR and stock engine management, they drive in the snow all winter on summer tires, and rev 1000 rpm over stock without valvetrain upgrades, but that doesn't mean they're smarter or better. It means they're either less informed or more willing to accept disaster. Also these numbers aren't set in stone. Every car is different, but these are good general guidelines. On that note, everything in this thread applies to gasoline only. If you're running the car on methanol (not talking about a little injection) or some other fuel this goes right out the window. If you're running race fuel, nitrous oxide, meth injection or other power boosting agents, you CAN get more HP out of a given amount of fuel.



Now onto fuel line sizing:
Here are some guidlines for EFI setups. The numbers don't apply for carb'd cars running fuel pressures of 4-10 psi or so, which require larger lines for the same HP figures.

-6 (3/8") fuel line is good for 500-550 HP or so on the outlet side of the pump, but you want -8 (1/2") for the suction side

-8 (1/2") fuel line is good for around 900-1000 HP on the outlet side of the pump, but you want -10 (5/8") for the suction side

People often go to -10 sooner as a precautionary measure. Just don't get into overkill too much or you'll overtax your pump and overheat the fuel. For instance...your 500 hp car almost definitely does not need -10 line on the pressure side. If you were powering the car with 100% methanol it would be another story.

Yes people have made over 500 hp with lines smaller than -6. It's just as I mentioned regarding the pumps. You can push the limits or you can take some extra time and money and build a margin of safety into your system. Remember different setups require different amounts of fuel to produce a given HP figure. I recommend switching to -6 for margin of safety if you're around 500 hp, and I'd go to -8 above 650 HP or so. After that I'd switch to -10 around 950 hp.

I didn't make this thread to scare half of you into replacing your whole fuel system. It's not necessary for the majority of you to change the lines. If you're building something and want to know if anything beyond a pump upgrade is necessary, I'm happy to help.


-Mike

nickracer9

iTrader: (10)

you have any flow numbers for the bosch 044? and can it be mounted in tank?

bolsen

iTrader: (2)

Great timing, I happened to be preparing to fabricate a fuel system in the next few weeks.

Several options I was thinking of doing was to run a surge tank with an external pump. https://www.evolutionm.net/forums/sh...d.php?t=171221

However, I would like to make it a bit more simple, if possible. So, what I'm going to try to do is convert the feed/return lines on the intank housing to -8 feed and -6 return. I'm still up in the air about doing an external pump, but it's an option.

Or maybe it's as easy as just throwing some fittings on the bottom of the tank with an external pump and utlizing the stock retun lines.

Plus, if it's cheap enough, I'll just have to make another "how-to" for it

Inn-Tune

iTrader: (33)

nickracer9 - sorry but I don't have flow data on Bosch pumps as we don't sell them. I bet some googling online or a search of the Bosch website will get you the info you require.

bolsen - You could stick a sump in the stock tank with AN fittings on it and mount an external pump right under the car just as you mentioned. That's worked for a lot of people, but they generally replace the return line.

If you're running below 450-500 hp, I'd just go with the surge tank setup and some Walbros. If you're going for more power AND trying to avoid starvation, I'd consider install a fuel cell with proper baffling and a nice external pump with controller or twin Walbros.

If you're racing the car, check class rules to see if these mods are allowed. Some classes require fuel cells and others don't allow them.

-Mike

bolsen

iTrader: (2)

I don't want to go with a fuel cell, for it puts you in a new class if you race

Noogles

iTrader: (-1)

I've always been a fan of the large aeromotive pumps mounted inside of the fuel tank.

Mike,

what would you rate dual walbro inline pumps at?

I was thinking 2 -6 line merging into one -10 line with a -10 return.

Inn-Tune

iTrader: (33)

Noogles - I'd say twins will get get you to 800 HP or so safely, but if you're looking at making that kind of horsepower I'm guessing you'll be running 30 psi or more of boost. At that point you're over 5 bar of fuel pressure and as you can see on the flow chart for the Walbro, it drops off more quickly above that point. If you're running 30-35 psi or more I'd strongly consider a nice external pump for reliability's sake.

-6 is plenty for the return as long as you aren't running both pumps all the time, which you don't want to be doing. Dual -6 into single -8 works fine for most setups. What is your power goal?

-Mike

Noogles

iTrader: (-1)

I'm looking to make right around 700 whp with an HKS TO4z, Would you think that a intank aeromotive a1000 would to the job.

What other alternatives are there?

Inn-Tune

iTrader: (33)

Noogles - I'm a big fan of Aeromotive parts, but when you run around 30 psi of boost, which you probably are with a turbo that size, flow drops dramatically.

At 43 psi fuel pressure it flows around 575 lph, but when you run 30 psi boost and fuel pressure comes up to match that pump flows around 255 lph around 13V, only 30% more then the flow of the walbro pump under those conditions. I'd go with the next step up 11104 pump. It pusheds over 300 lph at 13V for an over 60% improvement over the Walbro.

Don't forget the pump controller. As you can see from the flow numbers and the prices this is why so many people use twin Walbros. From a pure flow standpoint you can match the high pressure capacity of a large and much more expensive pump. If I'm building a high horsepower race car, a good external pump is a no brainer. For a street car I leave it up to you all to decide whether you feel the extra investment is warranted or not.

By the way if anyone is wondering how I got these number I took pounds per hour from Aeromotive's charts divided by aprrox. 1.58 (pounds per liter of gas).

On an unrelated note, there are MUCH better turbo options than that old school HKS unit. Their efficiency pales in comparison to today's turbos by a large margin. I tuned a few Supras on very similar setups the same day, one with that same HKS turbo and one with a new turbo from Precision. The results were night and day. Spoolup was over 1000 rpm slower and it didn't make any more power until the boost was up real high.

-Mike

Noogles

iTrader: (-1)

i forgot abou the controler. it look slike i'll probably just go with the AMS setup then.

Do you offer any High Flow fuel options?

Inn-Tune

iTrader: (33)

I haven't put together a complete retail package for your car. I generally put fuel systems together on a per car basis when you're at the level of replacing all the lines in the car, etc.

-Mike

4ringturncoat

iTrader: (21)

Do you have any experience with the new 485 liters per hour "Black Box" sump system for the ATL fuel cells? It is rated for 100 psi but I could not get a pump chart from ATL.

Inn-Tune

iTrader: (33)

I haven't used that one. If you call them up and they can't get you a flow chart that's just plain shady.

djtmotorsports

iTrader: (11)

Time for me to chime in with my limited knowledge

nickracer9 - The Bosch 044 pump can be mounted in-tank. Bosch won't tell you that, but we've done that on numerous road race - fuel cell setups.

4ringturncoat - ATL uses the Bosch 044 pumps in their "black box". Just saw that at PRI last month, what a "sweetheart" setup!

Darin

4ringturncoat

iTrader: (21)

I thought it looked pretty good and just need to know if it will handle 600awhp. I think they have a sending unit that will work with our gas gauge also. Should work great for road racing and drag with the trap door sump they have.