Doppelgänger

iTrader: (12)

OK, well, I finally have the means to get my 3" done, but what i'm wondering if I should spend the cheeze on the newer version of the FM cast elbow. Mine is the older design that does not have the wall between the turbine and wastegate...whereas the newer design does. How much of a difference does this really make? Is it worth the $220?

Also, with going to a 3", am I going to need to upgrade the fuel pump and fuel rail or can I do it later? Goal is to get close to 300rwhp on the 2560.

hustler

iTrader: (6)

i remember people talking here that a bigger fuel rail was unnecessary. I can't help with anything else, but with 550cc injectors that flowed 560 and a Walbro 255 I'm at 74% duty at 261/252 on a dyno that reads 10% lower than fagmo dynojets.

Saml01

iTrader: (9)

No you dont need the new cast elbow.
No you dont need a bigger fuel rail.
No you dont need a new fuel pump.

Depending on the size of your injectors, you might wanna get bigger ones so you dont run the ones you have very close to maximum duty cycle.

Doppelgänger

iTrader: (12)

I'm running RC550s right now. If there is a way to give a bit more headroom out of the 550s before digging into the intake manifold, i'd rather do it... so if the 255 will give me a bit of extra room, then i'd rather do that first. So..how much more headroom can I get from a larger fuel pump?

But back to the original Q, Sam, give me some examples as to why there is not much to be gained from the elbow when oh so many people (including Garrett) put those divider walls on the exhaust side? If it does make some giant difference at high HP levels so be it.. but I guess it's not a big difference at sub-300 numbers?

I can understand [not needing] the fuel rail, because I can't see why if fuel pressure is xxpsi at one end that it would be any different at the other end..considering the psi IN the fuel rail has to be consistant...kinda like one of those garden hoses with all the pin holes in it and how the spary coming out of them is even all the way down. I guess with a large enough injector it could change.. but at what cc I have no idea.

TurboTim

iTrader: (9)

who know is if the divider is necessary.

Paul made over 300rwhp with no divider in his downpipe.

Doppelgänger

iTrader: (12)

But isn't Paul running a modded 2560?

Saml01

iTrader: (9)

Unless you plan to increase fuel pressure then a larger capacity pump wont help you. At least that is how I understand where the need for a larger pump comes from.

Why dont you give me some examples of why there is something to be gained.

This isn't a rocket engine. The minor "improvements" people "dream" up dont make a difference. The only thing it does is persuade people to spend more money. FM cant make you buy another elbow so they tweak it slightly and sell you on the idea that its better. That whole theory of turbulence from the wastegate is bullshit imho. I have seen 600hp STI's run a bellmouth with no divider and an internaly gated turbo.


Exactly as you describe. It doesnt make a difference.

But make the holes(injectors) in the hose(rail) largerand you lose pressure, so you cant shoot farther. That means you need a more powerful source. So yes, larger injectors, larger pump.


Luckily for us I dont know anyone as of yet who has run out of fuel due to a fuel pump not providing enough pressure.

I think one guy on here, he was running E85 with 1000CC injectors and 500HP. I think he got a bigger pump.

I know a guy with a 800hp Ford Lightning with a Turbo the size of a rock turtle that is running some behemoth 45lb injectors and he needs TWO 255 Walbros and he's running the stock fuel rails.


I believe his is just ported to prevent boost creep.


---------

If I am saying something wrong, someone correct me, last thing I wanna do is steer doppleganger the wrong way.

Doppelgänger

iTrader: (12)

Sam... that's exactly the insight/examples/informative kinda reply I was looking for

I know the whole "divided wastegate" thing is an issue depending on who was asked, and i'm sure others would be more than happy to say positive things about having such a mod and i'd be interested to see proof that it makes a difference. To ME, it doesn't seem like it would make much of a difference, and that's exactly why I have not run out to buy one. I guess the big reason for it would be because of boost creep...which in that case one would port the internal or go external. I see it more as a band-aid to the limitations of a internal wastegate after a certain amout of psi being run with xyz turbo.

As for the pump, would I need to add in an adj. FPR in order to utilize the higher rated pump? Is that even possible on the 01+ fuel delivery system?

I just to make sure when I get the 3" on and go get it tune I can go for ~15psi and not have anything else that will hold me back at that point. I know after that i'll be needing to address a bigger turbo...and with a bigger turbo, i'll need better internals to utilize the HP capabilities of it (2871) and with that comes fuel supply because the 550s aren't going to be good for 350+ (or are they?).

Saml01

iTrader: (9)

Boost creep issues are caused by an exhaust that flows so good that the majority of the exhaust gas continues going through the turbo instead of the wastegate. So what does that mean? If the divided housing made a difference it would only cause you more problems.

You gotta port the wastegate to give the exhaust gas a better chance of getting out before getting to the turbine wheel. If you have no issues now, then don't sweat it.


I don't think you can use an FPR on an NB. You have a returnless fuel system don't you. I am not totally familiar with the NB fuel system but I know it runs at a higher pressure then the NA fuel system and it runs at a constant pressure. The pump does all the work.

I think the 3 inch isnt going to cause any issues for you aside from the chance of boost creep. Otherwise expect improved spool and some extra HP. Changing your exhaust wont produce differences that will require re-engineering your system.

When you start making more power then you should also think about bigger injectors. I dont think your 550's will cover it. If I had to guess id say 650+ would be more appropriate and obviously a larger pump is a cheap insurance policy here too.

Braineack

iTrader: (62)

To convert Gal. / Hr. to Lbs / Hr. - multiple by 6

Multiple that by .80 (duty cycle) and divide by .55 (BFSC) and see how much B.H.P. the pump is capable of flowing for.


OEM pump at 60psi can flow something around 305BHP worth of fuel.
a 255 LPH at 60psi can flow something around 500BHP worth of fuel.


you cant make power without fuel. if the pump cannot provide enough, then you're screwed. With more fuel pressure the pump actually flows less fuel, even though your injectors increase their fueling capacity.

hustler

iTrader: (6)

my fuel pump wouldn't let me make more than 200whp, but it was 18-years old and probably dying. You should be able to make 300whp with 550cc injectors before upping fuel pressure.

Doppelgänger

iTrader: (12)

OK. Well.. I can see both sides of the fence on this one. Which brings me to...how does the damn FPR work on a returnless system?

I think i'm understanding how the 255 can boost capacity of the 550s, but wouldn't rail pressure need to be upped via adjustable FPR? If 60psi in the rail creates x flow of fuel through 550cc injectors, then how does changing the pump create more flow through the 550s if pressure is the same?

Let me see if I am getting this. If the stock pump and 550s are used at 60 psi then the flow (cc) of fuel through the rail is x cc @60psi. So if the injectors are required to let more fuel in (flow) this would cause a drop in fuel pressure, but the stock pump is there to keep it up at 60psi. Once the injectors are flowing x cc worth of fuel more, the stock pump cannot keep 60psi...which is also a reduced flow in fuel. So in order to keep 60psi worth of flow, the pump needs to be ugraded. Yes?

Sorry if this seems redundant to some, but I guess this is how knowledge is obtained Sometimes I need some mental stimulation to "see" things that I normally can't think of in self-thought.

Braineack

iTrader: (62)

Think of a water source in your doubt of a Georgia town that has a limit/cap of how much water you can draw from each day.

Your town sources water from a well. Let's say you had 4 buckets in the water. Each representing the demands your town needs (cylinders).

So far every time you draw from the well when you draw from the well there's always ample supply (250rwhp).

But a heard of hippies displaced from the closed Starbucks in the next town move into town. you now need to draw from the water at a greater supply. But you still have the same limit from how much water you can draw.

You quickly run out of water, so a smart feller petitions the state gov't to increase the supply (255lph) and it was approved! You now have ample water supply for your town and the demands of the new found hippie population.



increasing injector size is like using larger buckets, you don't have to fill them all the way (low duty cycle).

hustler

iTrader: (6)

think about putting your thumb partially over the end of a waterhose. You have a max pressure attainable. Let enough water through or go wide-open and pressure drops as flow increases.

Doppelgänger

iTrader: (12)

I just thought of another...off the wall...example to how all of this work.

Let's go shopping at the garden center of Home Depot, shall we? We have a 100 gallon tank (fuel tank), a generic water pump (stock fuel pump), some garden hose (fuel lines), a standard spray nozzle liek you would use to wash your car (FPR) and one of those cool hoses with all the holes in it (fuel rail). Now let's start a fire in the yard and put that fancy holed hose around it to keep it contained.

So we take the spray nozzle and fit it to the holed hose and hook everthing else up (common knowledge). We get everything going and in order to keep the fire contained, the spray nozzle feeding the holed hose only needs to be opened up half way (prssure in fuel rail). But your dumb *** friend tosses in a gallon of gas and the fire gets bigger. So now you pull the trigger on the nozzle to increase the flow through the holed hose...which is just enough to keep the fire under control...but now since the nozzle on the holed hose is all the way open, you can't move anymore water. Oh noes here comes your dumbass friend again with a few more gallon of gas to throw on the fire. Well, since the system is maxed out, you upgrade the pump to supply more pressure (flow) to the nozzle which will flow more water through the holed hose and onto the fire.

Yes?

I think I might be retarded.

Doppelgänger

iTrader: (12)

Oh I completely understand duty cycle. But i'm trying to make sense of fuel pressure with using different pumps through the same lines/rail/injectors. See if the above example gets it right.

Eraser-X

I know a guy with a 800hp Ford Lightning with a Turbo the size of a rock turtle that is running some behemoth 45lb injectors and he needs TWO 255 Walbros and he's running the stock fuel rails.


Wow 45lb an hour! what is that a 475 or 480cc injector?

a 1000cc injector is 95.25lb an hour and a 550cc is over 52lb and hour.

Saml01

iTrader: (9)

I didnt know that until after Scott posted the conversion formula.

Either way, in total he has more fuel consumption across his 8 injectors then we have across 4.

P.S. No need to be a dick, congratulations you proved someone wrong.