fuel supply?

[e30leigh]

ok. this is slightly out of hand.

i know exactly how a fpr works. from what i can see we are going around in circles. i guess the way i try to understand and word things isnt the same as you. but i still know exactly what and how the reg works. i just have a different approach to things and dont trust in the factory one like the rest of you do when it comes to turbo applications.

this was ment to be a fuel pump question. but that all changed when i mentioned i wanted to change my fpr. weather its for the better, worse or is no change at all is not the point.

and just to clear up. when im talking about 0 pressure. i should clear up i ment 0 difference in pressure between ambient outside pressure and the manifold pressure.

but lets agree to disagree. and move on

[nando]

firstly, understand that I'm trying to help, not argue.

comparing fuel pressure to manifold pressure is rubbish in regards to the manifold pressure changing the effective fuel pressure.

it's not rubbish - it's *critical* to the operation of any electronic fuel injection system. Unless you have something very advanced with a PWM controlled fuel pump, all EFI systems expect a linear injector response. if you start buggering with that by using a rising rate FPR (where the ratio increases as pressure goes up), then the computer really can't operate effectively.

if manifold pressure is 0 (ambient) fuel pressure isnt going to be 30psi for a start. itll be 30psi at idle.... infact on m20 motors its closer to 42psi on all motors ive seen.

manifold pressure is NEVER zero. you might be thinking in relation to boost pressure - ambient pressure is 14.7psi, or 1 bar (100kpa). 3 bar is 43.5psi (stock FPR), not 30psi.

when the engine is cranking, the manifold pressure is 1 bar, and the pressure differential is always 3 bar, the total pressure is 4 bar (1 bar atmo + 3 bar rail). if you were boosting 14.7psi, or 1 bar, manifold pressure would be 2 bar, the pressure differential would still be 3 bar, and the total pressure would be 5 bar. that is what a 1:1 regulator does.

at idle, it will actually be less that atmospheric, because the throttle restriction creates a vaccuum. typically it will be .2-.3bar, or 20-30kpa. the pressure differential will still be 3 bar, but the total pressure will be less than when you're cranking (or at WOT).

the pressure may change with the reg manipulating it with vac/boost yes. but if the reg was static as the above seems to be pointing out... 30psi as stated. and the manifold is ambient, which it can only get if the car is off or at fwo on an n/a car, or just before boost on turbos. then the fuel pressure remains 30psi. if it gets 5psi boost from a turbo the static reg still produces 30psi of effective fuel pressure.

absolutely not - it doesn't work that way. the regulator is not static, the ratio is static, yes, but it increases the total pressure when manifold increases. it doesn't stop at 100kpa, because even an N/A engine can go over 100kpa at full load. if you boost 5psi (~30kpa), the regulator will increase total pressure and still keep the differential at 3 bars.

however!!! the rise in air volume all 5psi of it will infact require more fuel pressure to maintain a stoche (spelling??) air fuel mixture.
i fail to see how someone can think more air pressure in a manifold reduces fuel pressure coming out the injector. they are completely different and non connected systems.

that's what the stock regulator already does! it requires more total pressure, but the pressure differential between the manifold and rail will always be 3 bars. It doesn't have anything to do with air volume - the regulator's job is to keep that differential the same at all conditions, so that the computer can effectively calculate the amount of fuel it's goint to inject. the computer is concerned with air volume and mass, the regulator only cares about the pressure differential.

also in regards to new regs. we have proven multiple times here that newer adjustable regs are more reliable, give better tuning options and when using bigger injectors where alittle extra pressure doesnt hurt it goes along way. infact with a pump in fuel pressure we can pull our pulse width back just slightly and saves injector life.
yes the pump doesnt care, the injectors dont care, the reg doesnt care what the others are doing in the system.
but lets say you fit a new cam, 288 even, the stock cam gear might do the trick but there is offen good performance gains to be had from fitting an aftermarket adjustable gear to better adjust advancement or retarded angles.
its simular with the fuel system. the more control you have over it the better. and what the hell is wrong with fitting a reg that is designed for the added fuel pressures of running boost, chosen over an older reg designed for other kinds of running conditions, and to give me the adjustment and controll of my system i am looking for. in my regards its a wiser choice. just cos its different it isnt wrong. it isnt worse. there may be no gains to be had. infact there often never is. but there is piece of mind and what i am personally looking for.

well I'm probably not going to convince you otherwise, but you really should do some reading into the basics of how a pressure regulator works, because you clearly don't understand. I'm probably not the best at explaining it, but a google search would be helpful.

good luck..

[e30leigh]

comparing fuel pressure to manifold pressure is rubbish in regards to the manifold pressure changing the effective fuel pressure. if manifold pressure is 0 (ambient) fuel pressure isnt going to be 30psi for a start. itll be 30psi at idle.... infact on m20 motors its closer to 42psi on all motors ive seen. the pressure may change with the reg manipulating it with vac/boost yes. but if the reg was static as the above seems to be pointing out... 30psi as stated. and the manifold is ambient, which it can only get if the car is off or at fwo on an n/a car, or just before boost on turbos. then the fuel pressure remains 30psi. if it gets 5psi boost from a turbo the static reg still produces 30psi of effective fuel pressure. however!!! the rise in air volume all 5psi of it will infact require more fuel pressure to maintain a stoche (spelling??) air fuel mixture.
i fail to see how someone can think more air pressure in a manifold reduces fuel pressure coming out the injector. they are completely different and non connected systems.

also in regards to new regs. we have proven multiple times here that newer adjustable regs are more reliable, give better tuning options and when using bigger injectors where alittle extra pressure doesnt hurt it goes along way. infact with a pump in fuel pressure we can pull our pulse width back just slightly and saves injector life.
yes the pump doesnt care, the injectors dont care, the reg doesnt care what the others are doing in the system.
but lets say you fit a new cam, 288 even, the stock cam gear might do the trick but there is offen good performance gains to be had from fitting an aftermarket adjustable gear to better adjust advancement or retarded angles.
its simular with the fuel system. the more control you have over it the better. and what the hell is wrong with fitting a reg that is designed for the added fuel pressures of running boost, chosen over an older reg designed for other kinds of running conditions, and to give me the adjustment and controll of my system i am looking for. in my regards its a wiser choice. just cos its different it isnt wrong. it isnt worse. there may be no gains to be had. infact there often never is. but there is piece of mind and what i am personally looking for.

[jaywood]

But what is the rising rate regulator and what does it do? To answer that question, let's look at a typical electronic fuel injection system for a gasoline engine. A typical EFI system utilizes an electric fuel pump which runs constantly. The fuel is sent to the fuel rail. On the other end of the fuel rail is a fuel pressure regulator, which bypasses a certain amount of fuel back to the fuel tank in order to maintain a constant fuel pressure in the rail, as set on the regulator. This allows the fuel injectors to vary fuel mixture just by modulating the pulse width of the injector.

There's one problem with this concept though; in a gasoline engine, the pressure in the intake manifold or inlet ports, where the injectors are located is constantly changing, based on rpm, throttle position, and in the case of the turbocharged engine, boost pressure. Manifold pressure can go from, say, 25 inches of vacuum (negative pressure) all the way up to, say 15 psi of positive (boost) pressure. Even though the pressure in the fuel rail is constant, the injector is "seeing" varying pressures in the manifold, therefore the effective pressure at the injector can fluctuate, which would make the fuel injection system unstable and unpredictable. For example, let's say the pressure in the fuel rail is 30 psi of fuel pressure, and the pressure in the manifold is at 0 psi. Pressure at the injector would be 30 psi. However, let's say that the turbo is producing 5 psi of boost pressure. Now, the injector pressure would only be 25 psi, and, in effect, the engine would be getting less fuel at a time when it needed more fuel.

To overcome this problem, most fuel pressure regulators are "manifold referenced." This means that there is a signal line from the manifold to the regulator that tells the regulator what the manifold pressure is, and actually causes the regulator to adjust fuel pressure to compensate for changes in manifold vacuum or pressure. A manifold referenced regulator always provides a 1:1 change in fuel pressure as related to manifold pressure, and are extremely common on fuel injected engines.

The rising rate of gain fuel pressure regulator takes this concept a step further, and it would generally be used in a situation where an electronic fuel injected engine is retrofitted with a forced induction system, either a turbocharger or a supercharger. A rising rate regulator, in theory, would allow one to add a turbo system to an existing fuel injected engine without altering the fuel injection maps at all. Here's how:

We know that a gasoline engine runs a fuel mixture of between 15.5:1 (lean mixture) to around 11:1. (rich mixture) The electronic fuel injection system is programmed to operate the engine within this range, and the mixture is programmed to vary based on engine rpm and load. However, when forced induction is added, the mixtures across the rpm and load map must change. An engine with forced induction must run richer mixtures across the board, when operating under boost. The reason is that compressing the air produces heat, and heat leads to detonation. Richer mixtures keep the combustion temperatures down which prevent detonation. One way to change the mixtures for a forced induction engine would be to change the fuel maps. However, this requires special software, an engine dyno, and a high level of skill and experience in tuning engines. The rising rate pressure regulator was developed as an alternative to complicated and expensive re-mapping of the EFI control. Instead of changing the injector pulse widths, the rising rate regulator increase the fuel pressure as turbo boost increases. It must increase fuel pressure at an exponential rate to boost pressure, not at a 1:1 rate as a normal, manifold referenced regulator would do.

Copy/pasted from here: http://www.turbokart.com/BEGi.htm

[nando]

the factory ones are not built to cope with the pressures of boost. its on the side of caution more then anything to change it. and being able to set the fuel pressure more accordingly has its advantages to fine tune the fueling system slightly. or to compensate for the injector and pump change. 1-1 rising rate is what i will fit. but it goes without saying that a good quality aftermarket reg built for turbo applications is going to function alot better then a 24 year old reg that is built for functioning the controlls during vaccum and ambient pressures only. and with a much lower fuel pressure demand behind it. one could say the factory regs adjustment range is more limited and possibly not up to the task.

they work fine. they don't care about "boost". the stock regulators have been proven hundreds of time with turbo builds.

you don't change your base pressure because the pump or injectors changed - that's nonsense. you change the tune inside whatever you're using to run the engine. the regulator doesn't care what injector size you have and the pump doesn't care what regulator you've got. Besides, most injectors are going to be rated at 3 bar, which is what the stock regulator is.

there is no adjustment "range". it will always keep a 3 bar differential pressure, yes even under boost. it doesn't adjust anything, it's always a 1:1 ratio (3 bar over manifold pressure).

[LowR3V'in]

You're just making excuses now.
These regulators have been proven over and over again on many different cars.
Bosch regulators are not NLA. They don't have to be 24 years old.
I don't know why you're saying it's not meant to see boost or this and that.

We're just trying to open your eyes to good info.

[e30leigh]

the factory ones are not built to cope with the pressures of boost. its on the side of caution more then anything to change it. and being able to set the fuel pressure more accordingly has its advantages to fine tune the fueling system slightly. or to compensate for the injector and pump change. 1-1 rising rate is what i will fit. but it goes without saying that a good quality aftermarket reg built for turbo applications is going to function alot better then a 24 year old reg that is built for functioning the controlls during vaccum and ambient pressures only. and with a much lower fuel pressure demand behind it. one could say the factory regs adjustment range is more limited and possibly not up to the task.

[jaywood]

Begi 2025. You can find them used for $100.

[LowR3V'in]

Get a begi if you're going to do it that way.
There's one on ebay right now for $120

[nando]

why do you need to increase it? the factory regulator is already 1:1. It will already increase pressure with increasing manifold pressure (yes, under boost too). If you've upgraded the fuel pumps, there's no reason to change the base pressure, unless your injectors are slightly too small.

rising rate means the ratio increases with manifold pressure. that means it will go to 1:2, then 1:3, then 1:4, etc. you don't want this. it makes fuel response non-linear, and all engine computers expect it to be linear.

unless you're basically going to "tune" with a FPR, not a custom chip or standalone?

adjustable FPRs are mostly useless unless you have a very specific need. It's better to change the commanded PW inside the ECU if you need more fuel, or get bigger injectors if they're too small. I've had one for years, and it's set at - 3 bar, like stock. :|

[e30leigh]

i understand how they work. the facorty ones arent going to cope with the boost. i need an adjustable one to set the base pressures correctly. and why people would run two in a row is beyond me. one quality adjustable, rising rate reg is all that is needed.

[nando]

don't mess with FPRs unless you really understand them. Rising rate FPRs are generally a bad idea. 1:1 is a standard FPR which is what you already have. A rising rate FPR increases the ratio as manifold pressure increases, instead of being linear.

[e30leigh]

ill look around for a larger intank lift pump. perhaps a 540 or e46 like you said and use that to feed a surge tank. ill then replace my external feed pump with a bosch 044 to feed the rail. with 6 37lbs injectors i think ill need something decent with a rising rate fuel pressure reg to replace the factory item. i may even modify the factory fuel rail slightly to that the aftermarket reg, perhaps a 1-1 rising rate sard item, can be used without the stock item. itll make the whole system work that much better.

thanks for the info guys.

[nando]

The 044 will actually make life easier for the lift pump, since it wont need to build presure, only supply volume. if you look you'll find charts that show the 044 in dual and single config. a dual config will flow all the volume you could ever need, and the 044 will give you the needed pressure. the 044 will piss all over walbro crap six ways from sunday :)

if you want a cheap, not made in china POS upgrade for the in-tank pump, look for a used E46 M3 pump. they do 5 bar stock, and pretty much go right into the E30 pump carrier (late model style, anyway).

[bmwguy325is]

Early cars had two pumps. 87/88 can go either way. If your car has the external pump behind the drive it does have the transfer pump as well.