Fuel Pump Upgrade
 

Please do not let this take due credit away from this school (Dunwoody college of Technology) LOL even though it might.

Background: I am a auto tech student at Dunwoody & This morning we were going through our fuel system section. While browsing Mitsustyle due to boredom, i over heard my instructor saying there is no need to upgrade fuel pumps.

I stopped everything i was doing raised my hand to ask: Does this go for aftermarket applications specifically E85 or pump gas performance cars? His reply: Its stupid upgrading your fuel pump, a fuel pump is designed to provide 3 times the capacity of what it calls for. I dont think Ive ever or will ever see a car on the street or street/track car that will need to upgrade its fuel pump.

Now this turned into a class room argument. If upgrading ones fuel pumps really is s a hoax, then why do so many people including Performance shops recommend upgrading fuel pump's. . . if the pumps are more then capable of supplying the demand? Once again the reply: Its shiny and if it sells why not. People do it because Something racing tells them to and they buy into it.

I thought he was just being funny at first so i waited a couple minutes and asked him again! SAME REPLY! I know most instructors are all OEM this and that, yet this has to be basic knowledge. . . .even for them.

Question: Plain and simple does he have somewhat of a valid point or not? I say he woke up on the wrong side of his bed. I still disagree with him, yet i dont know how to quite explain what i want to tell him. Couldn't a OEM pump maybe be capable of providing the fuel needed just not in a timely manner? (I might be wrong and please correct me if i am) This guy made me furious not to mention the ones that all of a sudden agree with him.

Please add more then he is a MORON. Im sure FPR, fuel lines ect play a big roll as well, i added that variable eliminating faulty lines so were going of Perfect fuel systems.

Quick explanation behind the reason for upgrading fuel pumps would be nice. Ive done quite a bit of research and just want to confirm HE IS WRONG for not the firs time. . . .:loser:

Re: Fuel Pump Upgrade
 

Here's a calculator for fuel pump and injector sizing. I would NOT just pop it up and show him. Use the formulas listed right below it and do the math on the front board. REMEMBER, BSFC is .60 for turbod cars, 43 psi fuel pressure and 7 psi of boost is stock.

http://www.eastcoastrollingthunder.c...r/finject1.htm

Here is a DSM fuel pump flow list.
http://www.roadraceengineering.com/f...pflowrates.htm

Re: Fuel Pump Upgrade
 

Forgot to add, I use to go to Dunwoody and no matter what you say; the instructor is always right.:jackoff:

Re: Fuel Pump Upgrade
 

Lots of info on E85 out there.

By dividing those two figures into each-other it becomes apparent that an engine running on E85 needs 48% more fuel flow compared to the exact same engine running on Gasoline.

http://www.superchargerperformance.c...uel-conversion

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A lot of people don't think in terms of 30psi boosted motors, either. You don't need much for fuel pumps on an NA vehicle but most fuel pumps struggle at 70+psi.

http://www.amsperformance.com/ams_ev..._pump_test.php

Re: Fuel Pump Upgrade
 

Nice, i should write the formula and all the math on the white board. Since im alone in the class room for another 7minutes, might not be enough. Ill write it on paper at home and copy it on the board tomorrow put a smiley face next to it and write go figure or something and watch him from the window!

This is sooooo funny, im just curious why he dosnt know this? Him: No no no idc what you do a OEM fuel pump has more then the capacity to flow all the fuel you need. You could NEVER need so much fuel what are you crazy! Funny guy.

Re: Fuel Pump Upgrade
 

Thank you mlomker ALMOST 50 PERCENT MORE!!!! Telling me a oem pump will be just fine LMCO (laugh my crank off)

Re: Fuel Pump Upgrade
 

The way you might want to approach this is to tell him that it's not so much the fact that they can't flow enough fuel because of their size, but because the fuel pumps have such bad volumetric efficiencies at higher pressures that you need to start out with a larger flow to be able to have the needed flow at the higher pressures.

If you look at the link from RRE you will have definitive proof of why, in an engine that needs higher fuel pressures, you need to upgrade the pump. Not higher boost pressures so much, but the higher FUEL PRESSURES needed. Any fluid pump is going to get less efficient as the pressure demands on them go up. The chart that's posted on the RRE site just goes to show what kind of horsesh!# efficiencies these pumps have across the board. The Walbro's come in at 50% at 12.5volts and about 70% at 14volts for efficiencies. The OEM ones are even worse.

I think that's the biggest reason for upgrading. They are capable of flowing all kinds of flow at low pressures, but it's the higher fuel pressures that make them not able to keep up.

Re: Fuel Pump Upgrade
 

Ok, that makes perfect sense. At higher pressure is where pumps become critical. Ill share that with him, and note his response. Thank you guys for the inputs

Re: Fuel Pump Upgrade
 

The way I've always understood it is as you start using more fuel the injectors are open more, which in turn causes there to be less pressure in the fuel system. That is why a bigger pump is needed, to help keep the pressure up, as well as simply flowing more fuel when even larger injectors are used.

Re: Fuel Pump Upgrade
 

Thats a good way to look at it as well. I brought that point across and he said a stock oem pump still could keep up with the demand. Which makes me wonder well if your FPR is set to maintain a certain pressure, is he positive the stock pump can adapt its speed to maintain that pressure (In a none variable speed pump)?

Since you can only provide a max amount of maybe 14. something volts to the pump by rewiring, and the motor will only be able to go so fast. Then how is it possible for the pump to pump the needed amount of fuel to maintain that pressure given that certain amount of voltage?

I guess maybe looking at the internal make up might make a difference? Time to look at the guts of a fuel pump? Show the difference in mechanical make up.

Re: Fuel Pump Upgrade
 

Most of the old school fuel math you see on the internet and in books doesn't even work right for pump gas/race gas let alone E85. If you go by some of that stuff, you would need 1000000000000000000000cc injectors and -16 fuel lines(I am exaggerating, but...)
Also the math to figure additional fuel needs for injector and fuel pumps are different. Fuel pumps are not hit nearly as hard by running E85 as injectors are.

Re: Fuel Pump Upgrade
 

First off I'll say like everyone else did. In a boosted application like ours, and where we run what'd i'd consider a good amount of boost in our cars often, you have to run the pump in a higher pressure range where the pumps are typically less effecient. At a base fuel pressure of 40psi, a pump will flow a good amount of fuel, and hence the reason people cometimes say if you have a 255 pump in your car, you may start to overrun the stock FPR at idle, but it doesn't matter once you start driving around. So now say you are running 20psi, you're fuel pressure just went from 40 to 60. Look at those charts and see how much less that pump flows.

Also for fun, I quoted you above. You could ask him "well what if you're planning to make 3 times the power?" :D

Re: Fuel Pump Upgrade
 

I've heard that before also. Acually I think I heard it from you in a thread over on the Supraforums. Does anyone know why exactly that is?

Re: Fuel Pump Upgrade
 

Interesting. So using the formulas above might not be the best way of calculating the rate of flow ect? Im trying to find a side by side graph or something along those lines to see a comparison with the same variables referring to injectors, FPR, lines, Turbo set up or displacement of a N/A and so on.

Re: Fuel Pump Upgrade
 

Halon i did! In addition to E85 and giggled . . .and of course everyone looks at the dsm kid funny . . .haha. Yet his comment about any street/track car not being able to use the pump to its max just seemed odd to me.

Re: Fuel Pump Upgrade
 

I was even surprised by the link that I posted. I was under the impression that it was around 30% more flow and not anything like 48%.

Re: Fuel Pump Upgrade
 

well, i suppose you could drop your base fuel pressure to like 10psi, so then at 20psi of boost you'd be at 30psi of fuel pressure :) No idea if the injectors would like that though, and you're idle, wellll that'd suck pretty bad I bet.

Re: Fuel Pump Upgrade
 

10psi. . .the Honda we worked on yesterday we put a inline resistor in the fuel pump circuit when enough resistance was added to bring the pressure down to 15 stuff start going bad it kills at 10 psi . . .now automatically i think its gonna be WORST on a DSM haha just cause its a DSM lol!

Re: Fuel Pump Upgrade
 

Keep in mind that our fuel pressure regulators are rising rate on a 1:1 scale. For every PSI of boost the engine sees the fuel pressure goes up 1 PSI. Like Shane said, that's where our stock pumps become inefficient.

Re: Fuel Pump Upgrade
 

It does that would mean. . .for the guys at 30psi plus there FP goes up to upwards up 70PSI? That is serious pressure. . .technically according to his analogy that still wouldn't be enough to render the pump useless since even under hard acceleration the pump only uses 1/3 of its capability meaning at 40-47psi random honda spec. . .120PSI would be needed to max out the pump. Thats just ridicules i dont care what he says 120psi to max a stock pump that dosnt even make any sense.