The FSE - Adjustable Fuel Pressure Regulator - How / What / Where

This is a long one - and covers just about everything regarding this piece of equipment for posterity etc

Summary

The FSE is an ADJUSTABLE Fuel Pressure Regulator and should not be confused with a expotential RISING RATE regulator

The FSE is potentially Good for the following

· Static rail pressure can be increased = improves flow of fuel to injectors

· Increased responsiveness at hard acceleration = flattens lean spots

· Low throttle / cruising = acts like normal / stock regulator

· At positive boost the FSE reverts to a normal 1:1 fuel pressure regulator that works more effeciently than stock

The FSE is potentially Bad for the following

· Not set up correctly = reduced pressure and fuelling

The FSE is NOT a substitute for a proper fuelling system

Courtesy of Chris Wilson

The pressure regulator works like this:

You have a fuel pump in the petrol tank, sending fuel forward, through the fuel pipe (rail) that feeds the six injectors, which are electronically pulsed on and off for different on / off periods to give the amount of fuel the map in the ecu tells them to for any given engine operating sceanario. The fuel goes out the other end of the pipe, through the pressure regultor, and back to the tank. There is also a pulsation damper that absorbs the shock in the fuel line when the injectors are opening and closing slowly, at idle, to keep pipe noise to a minimum.

The fuel pump, if it was pumping against a blocked off pipe, which would be the case with the pump running and the engine not started, could probably manage well over 100 psi, but the injectors are designed for only about 40 / 50 psi, and the ecu is mapped according to a pre decided fuel rail pressure.

So a regulator is factory set to (say) 40 psi, and excess pressure is just recirculated back to the tank. However, under boost the injectors are squirting into an intake that has (say) 18PSI pressure in it, so to keep the system balanced the regulator has an extra hose going to it that connects to the intake manifold and adds boost to one side of a diagphram within the regulator.

The diagphram is sized so one psi of boost raises the rail pressure of the fuel by one psi as well. Under vacuum (light cruising, idling) there is a vaccum in the manifold (negative psi figure), the same additional hose reduces pressure by whatever the vac level in the manifold is by pulling the diagphram the opposite way, again, the status quo is maintained, fuel pressure wise in relatio to manifold pressure.

As for some of the aftermarket ones, they raise the fuel pressure by MORE than the amount of boost, so if the static pressure should be 40 psi, and you are running at 10 psi turbo boost, a normal regulator would run the rail at 50psi fuel pressure, but a "performance" one would perhaps run 55 psi.

HOWEVER, the map in your ecu is designed to expect fuel pressure to rise linearly with boost, so it doesn't know the injectors, still opening for the DURATION pre mapped, are now squirting more fuel in that given opening time, due to increased fuel pressure within them, and hence the engine gets more fuel and runs richer. Whether this is good or bad, planned for or whatever is another can of worms entirely.

The FSE, to be a fairly universal item, relies on an adjusting screw to set the static fuel line pressure. This screw is very sensitive, and you need good high pressure measuring gear to set it up correctly

Courtesy of Pete Betts

I think most Toyotas are set at 2.5bar (36.75psi) the exact measurement I'm not sure about. Easily checked if required.

quote:

the FSE increases to 'above' whatever the Reg is ? ?

Fuel pressure at the injectors is controlled via the manifold pressure (as with all injector systems), this is no different with an FSE to the standard regulator.

BUT the FSE reduces the time taken to get to the required fuel pressure. i.e. it responds quicker so you have better fuel delivery than standard.

More responsive throttle.

The FSE is also adjustable so you can (should you choose) increase the pressure from 2.5bar up to the pump pressure if you like. It's a combination of increased rail pressure and faster response times that makes it a good upgrade.

But only if you are at 18psi and wish to go beyond it or you have found a lean spot which cannot be corrected etc etc.

Fitted one to a Celica the other day and the chap couldn't understand why it gave no more power. (but this is a power boost valve he says...) Well set at the stock fuel pressure he was getting no more fuel that stock but he did get a more responsive throttle. No point adding more fuel to a car (2.0lt NA) that couldnt' suck in enough air!!!

But you can't use the AFC to give it any more fuel than it can give already. It's only really useful for leaning out the fuel when you fit bigger injectors. I think anyway.

The AFC can help lean out rich spots and richen up lean spots in across the RPM band which will help will mid band torque but it will not give you any more power at WOT, as already stated this is limited by your fuel pump, pressure regulator and injector size.

quote:

Do the stock Inj' push more fuel just because the rail pressure is higher ? ?

Yes. FOR THE SAME DURATION OF INJECTOR OPENING.

quote:

or, does higher rail pressure just ensure 'enough' supply to do the

job they're supposed to ? ?

Yes as well. It's all down to the time the injector is opened for and the control mode, closed loop or open loop.

quote:

I thought the ECU will control the amount sprayed because it's

'mapped' and has Lambda etc ? ?

This is why I mentioned TIME and control method.

You see with an ECU that does NOT learn the increase in fuel pressure will mean a richer mixture across the whole operating range of the engine. This is a bit sh*t if you want to save fuel whilst cruising or idling for your MOT.

BUT as the Supra can learn then the ECU has a finite ability (not infinite!) to adjust the injector duration (i.e re-map itself) for closed loop operation using the O2 sensor.

However when you're pushing the car hard and the ECU switches to OPEN loop fuel control it just uses a fixed injector duration map.

Which means it will open the injector for a set time, higher pressure rail will force more fuel through the injector in that same time period, thus making the mixture richer.

If your FSE valve is set to Ypsi pressure then at WOT when you used to have say 440cc off a Xpsi fuel rail you'll now have 440cc *(Y/X) flow of fuel from your Ypsi rail.

There are limits of course, the poor old injectors don't really like being used much above 80% duty cycle (and at WOT on a BPU car you're reaching nearly 100%) plus the higher pressure can't do them a lot of good in the long run (but I have no proof of that!)

Fuel Pressure Regulator and Pulse Dampener

The fuel pressure regulator maintains a constant pressure across the fuel injector. The inlet manifold pressure varies with throttle angle, and engine speed. Small throttle angles and high engine speed produce low manifold pressure (high vacuum). While high throttle angles and low rpm give high manifold pressure.

In addition to these conditions, low manifold pressure is associated with idle and high manifold pressure is at full throttle.

It is the fuel pressure regulators job to keep a constant fuel pressure across the injector(s) regardless of manifold pressure.

Currently, there are several types of fuel pressure regulators in use. Many late model cars use a return-less system where the fuel pressure regulator is mounted in the fuel tank adjacent to the fuel pump (and therefore requires no return line back to the fuel tank). In most naturally aspirated applications these types of systems are adequate.

With forced induction or heavily modified engines, an adjustable fuel pressure regulator with manifold vacuum reference must be fitted.

The two common types of fuel pressure regulators used are non-adjustable and adjustable.

As the name implies, a non-adjustable regulator is set at a fixed value and is manifold-vacuum referenced (whenever a regulator is said to be vacuum referenced, this means that the inlet manifold vacuum/pressure is ported into the chamber above the regulator diaphragm).

As manifold pressure increases, the pressure in the top chamber of the pressure regulator increases along with it, allowing the regulator to compensate for the increased demand of the fuel delivery system.

Keep in mind that at idle or low throttle openings with high rpm, there is very low manifold pressure (vacuum). This tends to literally draw fuel from the injector.

As manifold pressure increases (as the throttle is opened), this vacuum dissipates and it is harder for the fuel to discharge from the injector.

The regulator reacts to the differences in manifold pressure to maintain constant fuel pressure across the injector.

There is a spring in the vacuum (top) chamber of the fuel pressure regulator. The spring’s pressure on the diaphragm determines the fuel system’s static pressure. The system’s static pressure is the amount of pressure measured with the vacuum hose disconnected or with the engine turned off.

The fuel system’s static pressure is higher than the fuel pressure at idle or under high vacuum conditions.

When the engine is running, the engine vacuum acts against the spring and the effect of the vacuum diminishes as the throttle is opened.

At idle, there is a high amount of fuel returned to the tank because the vacuum is pulling the diaphragm seat off of the fuel return orifice, reducing fuel pressure.

As the throttle is opened, the diaphragm seat starts to close off the orifice, restricting the amount of fuel flow through the return line.

An adjustable regulator allows the static pressure to be raised or lowered via an adjusting screw that acts on the diaphragm spring.

On most adjustable regulators, when the screw is turned in pressure raises and when it is turned out pressure is reduced.

Although we highly recommend installing a proper fuel delivery system, raising or lowering fuel pressure can compensate for fuel injectors that may not be properly sized for an application.

Most aftermarket fuel pressure regulators (and OE regulators) use a 1:1 ratio of fuel to boost pressure for increasing fuel pressure in applications where forced induction is used.

This means that for every psi of boost, fuel pressure is increased one psi. This ensures adequate fuel delivery under boosted conditions

Fuel pressure regulators do exactly what their name implies: they control fuel pressure. They do this by opening and closing a valve at the end of the fuel rail thus allowing or restricting the return of fuel to the gas tank. When the valve closes, fuel cannot return to the tank and pressure builds in the fuel rail. This forces more gas to be shot through the injectors.

Big deal, right? Well, yes it is. As you push the accelerator and open the throttle plate, you allow more air into the engine. You still remember that we need to maintain a constant (more or less) Air/Fuel ratio, right? Well, if more air is flowing into the engine, we need more fuel to match it. This is the fuel pressure regulator's (FPR) sole function.

Vacuum decreases as you open the throttle plate. As the vacuum decreases, the FPR closes, thus increasing fuel pressure and sending more fuel into the injectors. Unlike naturally aspirated engines, 4G63s have turbos which means that they don't stop at 0in/Hg of vacuum, they move to positive manifold pressure, or what we like to call boost. Since this is the case, fuel pressure needs to be increased even more.

The stock FPRs do exactly that. For every 1psi of boost that you run, the FPR increases the fuel pressure a matching 1psi. 1psi/1psi maintains the A/F ratio. Pretty cool, huh?

But suppose that you have quite a few modifications and you see that you are starting to run leaner than you'd like or that is safe. This means that your fuel injectors aren't able to inject all the fuel that you require. You have a few options here and this is where the real fun begins with tuning and being able to monitor the engine.

What option you chose will depend on your wallet and what you plan to achieve with future modifications. In any event, you need to get more fuel to the cylinders. You can:

· Use an adjustable FPR

· Install larger injectors (usually requires a fuel computer to help compensate)

· A fuel computer

· Install larger fuel lines

· Install additional injectors

The cheapest option to increasing fuel supply to the engine would be the addition of an adjustable FPR. The limit of how much these can help is restricted however. If you plan on substantial modifications in the future, it may be in your best interest to go directly to larger injectors. However, if you just need a little room to play, adjustable FPRs are a very viable option. Prices vary with quality and features.

A fuel pressure gauge would also be in order for proper settings.

OK, fine, how do they work? An adjustable FPR does the same basic job that the stock FPR does, but it allows you to manually adjust the base or idle fuel pressure and still maintain the 1/1 increase under boost. How will that help you? It's probably best to show you by example rather than try to explain it.

Suppose you add an adjustable FPR and make the base fuel pressure (FP) 55psi. There are some very standard calculations that you can make (we'll discuss more in the Fuel Injector section) to see the change in flow of the injectors given the new fuel pressure.

All formulas available on RC Engineering's site.

Givens: fuel injectors are rated at 43psi. 1G base FP is 36psi. 2G base FP is 43psi. As you can see, this is one of the reasons that 1Gs run leaner than 2Gs do...they run UNDER the rated flow of the injectors on the car! 2Gs run at the rated pressure of the injectors so a 450 injector runs at 450cc/min on 2Gs. So we will do two calculations for the 1Gs, what they flow at 36psi in addition to what they flow at the new higher FP. All flow rates are in CC/MIN and assume 100% duty cycle (see the Fuel Injector Section for more information).

SQRT (NEW FP/OLD FP) * INJECTOR SIZE

1G 2G

Rated @ 43psi Stock @ 36psi New @ 55psi New @ 55psi

450 411 509 509

550 503 622 622

650 595 735 735

720 659 814 814

850 777 961 961

So what do you notice? That's right, increasing the fuel pressure effectively increases the size of the fuel injector, even more so for the 1Gs. If you were running lean before, you will now have more room to work.

That's cool! So what's the bad part? Well, for starters, turning up the fuel pressure too much can be a bad thing so this will limit exactly how much "larger" you can make your injectors. Depending how lean you were running or how much more fuel you need, your only course of action may be physically larger injectors.

In general, running injectors over 85psi will cause deterioration of the spray pattern and it will adversely effect your mixture. This is not to say that you can't run them over that, it's just not a good idea. If that's not enough for you, too high of a pressure can actually shut them off. And keep in mind, since the FPR increases the FP 1psi for every 1psi of boost, your boost level needs to be added to your base FP to determine the max FP that you are running. For instance, if you have a base FP of 55psi and you are running 20psi of boost, your max FP is going to be 75psi (give or take a few psi for variations).

One more thing to consider is your fuel pump. Before you even attempt to install an adjustable FPR, you need to have an upgraded fuel pump.. If you look at the Walbro charts in the Fuel Pump Section, you will notice that as pressure increases, volume decreases. This is true of all fuel pumps.

You will need to be sure that you aren't running the pump so hard that it can't supply the volume of fuel that you need at the higher pressure. The 255LPH High Pressure pump will afford some extra volume at increased pressures and is perfect for use with large injectors and higher than stock FP.

Definitive info HERE look under pressure regulators

Originally posted by Chris Wilson

Definitive info HERE look under pressure regulators

Or, more specifically:

RIGHT HERE

Thanks chaps. Interesting read... will have to study further in the tea break!

Still doesnt explain why everyone seems worried about the FSE as if you read the 'epic' paul posted it seems to deliver at a ratio of 1:1 (stock) as soon as +ve boost is hit which when in seq. in a supra is pretty early in the revs during normal driving , the only reason it appears that the rate is rising is to get slightly quicker throttle response off boost , in short it appears to me that this is how the FSE works

1) Off boost rising rate (non stock operation)and will normally be on part throttle and therfore ECU operating closer to its closed loop operation.

2) Positive boost 1:1 rate (stock operation) ECU knows excactly what is going on because it is operating at stock and before you say Ahhh but the pressure is higher to start with , do you really think your 100,000 mile fuel systems are operating at EXCACTLY the factory designed presure ????

Dude:flame Dev

Originally posted by Chris Wilson

Or, more specifically:

 

RIGHT HERE

This is a link to Rising Rate Regulators Chris - which is not the primary definition/purpose of the FSE - and could be misleading

The FSE is an ADJUSTABLE regulator

At positive boost the FSE acts as a normal 1:1 fuel pressure regulator

In fact this is more effecient than the stock regulator

Paul you should give up selling parts, you'd make a fortune writing books for insomniacs

Playing devils advocate, explain the effects of the diaphragm size in an FPR, the flow resitrictions ( max flow through an FPR) and the effects of fuel heat on the fuel pressure:innocent:

Ok, so when your at +ve boost the FSE will make sure that the fuel system is at stock idle pressure + manifold pressure. Fair enough.

The stock ecu, although has SOME closed loop ability is supposed to know what is going on and adjust the duration of injector opening to make sure the right amount of fuel is still going in.

Is this what happens? Would you not need another gizmo to shorten the duration? I know that our fuel systems probably aren't what they were but to the kind of degree where you going to be needing to add 0.8bar (at stock) line pressure to the injector? If that's the case then Toyota have vastly underspecced/lifed the fuel system in our cars, or alternatively vastly overfuelled the car when new with the expectation of the fuel system to degrade.

Hmmm don't know. I think a lot of people are using the FSE to "band aid" a deteriorating fuel system. Fair enough, but be careful that your not using a full body cast for the splinter in your thumb if you see my meaning (Crap metaphore I know but it's early )

Originally posted by TLicense

.

Hmmm don't know. I think a lot of people are using the FSE to "band aid" a deteriorating fuel system. Fair enough, but be careful that your not using a full body cast for the splinter in your thumb if you see my meaning (Crap metaphore I know but it's early )

I am sure that this is well within the stock ECU working capabilities...

and I dont think they are using it to bolster up a deteriorating system - just to get the best out of the stock.

It is never meant to be a substitute for remapped ECU's/larger injectors/improved fuel delivery systems etc - but it does provide a 'cheap' way to get the best out

It's very easy to expound the use of new complete systems etc - but I prefer the real world where people (inc ME!) dont have workshops, time, resources and money to do this.

How, I wonder, does this mechanical device provide a 1.7:1 increase in fuel pressure when off boost and only a 1:1 increase when on boost? There is one adjusting screw, there is one vacuum reference pipe, and there is one internal diaphragm.

I'm rather convinced that the FSE valve in fact increases fuel rail pressure by 1.7:1 all the time. This is why people use them on 440cc injectors, to up the fuel pressure and deliver a bit more fuel when on-boost.

Paul, your initial posts credit who said what apart from the first one which assures us that the FSE Power Boost Valve isn't a rising rate regulator. Is that from FSE themselves? It reads like a sales pitch, there are a few things I don't buy at all in that.

-Ian

The 1:1.7 is a mechanical figure and does not bear relationship to the actual rate achieved from minus to positive boost - which is more like 1:1.17 / 1;1.2

This is no sales pitch from FSE - this is from the work done on the valve 'post manufacturer'

Also - checking out the fuel pressure when in use on the car one can see that this is the case - as otherwise the fuel pressure will rise expotentially

The FSE is used to improve the initial pressure because it is ADJUSTABLE

Keep in mind that at idle or low throttle openings with high rpm, there is very low manifold pressure (vacuum). This tends to literally draw fuel from the injector. As manifold pressure increases (as the throttle is opened), this vacuum dissipates and it is harder for the fuel to discharge from the injector. The regulator reacts to the differences in manifold pressure to maintain constant fuel pressure across the injector. There is a spring in the vacuum (top) chamber of the fuel pressure regulator. The spring’s pressure on the diaphragm determines the fuel system’s static pressure. The system’s static pressure is the amount of pressure measured with the vacuum hose disconnected or with the engine turned off. The fuel system’s static pressure is higher than the fuel pressure at idle or under high vacuum conditions.

When the engine is running, the engine vacuum acts against the spring and the effect of the vacuum diminishes as the throttle is opened. At idle, there is a high amount of fuel returned to the tank because the vacuum is pulling the diaphragm seat off of the fuel return orifice, reducing fuel pressure. As the throttle is opened, the diaphragm seat starts to close off the orifice, restricting the amount of fuel flow through the return line.

An adjustable regulator allows the static pressure to be raised or lowered via an adjusting screw that acts on the diaphragm spring. On most adjustable regulators, when the screw is turned in pressure raises and when it is turned out pressure is reduced. Although we highly recommend installing a proper fuel delivery system, raising or lowering fuel pressure can compensate for fuel injectors that may not be properly sized for an application

Imagine for one minute that this piece of machinery is not the 'work of the devil' and that it might just work

Crikey Paul... looks like you've opened a right can of worms!!! And here was me thinking that the FSE was an accepted bit of kit!

Originally posted by Patrick_Devlin

Crikey Paul... looks like you've opened a right can of worms!!! And here was me thinking that the FSE was an accepted bit of kit!

It is m8 - people had perhaps not been fully aware of what the FSE adjustable regulator does and were confusing it with a different type...

The type of reg that Chris is worried about (I agree wholly) - and would not put anywhere near my machine or recommend anyone else to!

Being my picky self I'll respond to each bit in turn

Originally posted by Paul E

The 1:1.7 is a mechanical figure and does not bear relationship to the actual rate achieved from minus to positive boost - which is more like 1:1.17 / 1;1.2

Not sure what you mean here, it reads like the 1.7:1 ratio isn't ever reached, not even close.

This is no sales pitch from FSE - this is from the work done on the valve 'post manufacturer'

Do you mean independant testing? If so I'd like to see the qaulification behind "At positive boost the FSE reverts to a normal 1:1 fuel pressure regulator that works more effeciently than stock" because I'm not sure how one FPR could be more efficient than another one, if it was less efficient what would it do, restrict the flow of fuel in some way? That sort of comment is why I said it sounded like marketing spiel.

Also - checking out the fuel pressure when in use on the car one can see that this is the case - as otherwise the fuel pressure will rise expotentially

It wouldn't rise exponentially, that would be a x^2:x regulator. It's a ratio increase. If it's 1:7.1, then 10psi boost would give a 17psi increase in fuel pressure, by the time it's at 20psi of boost, the fuel pressure would be 34psi higher than static. This is the whole school of thought behind an FSE valve, in that it pushes more fuel (than stock) out of the injectors as the boost pressure goes up.

The FSE is used to improve the initial pressure because it is ADJUSTABLE

It can increase the static pressure then. Which means it alters the stock fuel map at idle and in fact across the whole range, as the injectors are seeing more pressure than stock at all times.

(snip the explanation about static pressure)

When the engine is running, the engine vacuum acts against the spring and the effect of the vacuum diminishes as the throttle is opened. At idle, there is a high amount of fuel returned to the tank because the vacuum is pulling the diaphragm seat off of the fuel return orifice, reducing fuel pressure. As the throttle is opened, the diaphragm seat starts to close off the orifice, restricting the amount of fuel flow through the return line.

And the diaphragm is sized to give a greater-than-1:1 ratio. As you say, under vacuum, it gives a rising rate. But the vacuum feed also provides the positive pressure, aiding the spring instead of pulling against it. This closes the orifice more, raising the fuel line pressure to compensate against the increase in cylinder pressures. If the diaphragm is sized to give a 1.7:1 ratio off-boost, it's going to give a 1.7:1 ratio on-boost as well. It's a simple device.

Imagine for one minute that this piece of machinery is not the 'work of the devil' and that it might just work

It's not the work of the Lord either. It does do what it says it does - raise fuel pressure at a higher ratio than cylinder pressures.

-Ian

Without entering a mud slinging fight, both Ian & I had early FSE's, probably the first on Supras in the UK ( Ian, I assume it is the one PW put on?) Now mine from memory definitely rose faster than 1:1 on boost, as my fuel pressure went up to 70 psi when running 42 psi static & 19 psi boost. Maybe, just maybe, the early typer were different? They were not Supra specific parts then, but a WRX Imprezza part.

Not sure what you mean here, it reads like the 1.7:1 ratio isn't ever reached, not even close.

Correct

Do you mean independant testing?

Yes - Undertaken on a pressure rig -

If so I'd like to see the qaulification behind "At positive boost the FSE reverts to a normal 1:1 fuel pressure regulator that works more effeciently than stock"

The stock will only ever achieve a 1:0.9 or 1:0.95 rate - the FSE a true 1:1

It wouldn't rise exponentially, that would be a x^2:x regulator. It's a ratio increase. If it's 1:7.1, then 10psi boost would give a 17psi increase in fuel pressure, by the time it's at 20psi of boost, the fuel pressure would be 34psi higher than static.

This is the sort of regulator that Chris would be worried about - a 'racing' regulator that will be far too much to handle - but the FSE does not work this way

This is the whole school of thought behind an FSE valve, in that it pushes more fuel (than stock) out of the injectors as the boost pressure goes up.

Initially yes and flattens off flat spots during this increase - marginally above stock 1:1.2 - but not when at positive boost

It can increase the static pressure then. Which means it alters the stock fuel map at idle and in fact across the whole range, as the injectors are seeing more pressure than stock at all times.

Not when they dont need it

And the diaphragm is sized to give a greater-than-1:1 ratio. As you say, under vacuum, it gives a rising rate. But the vacuum feed also provides the positive pressure, aiding the spring instead of pulling against it. This closes the orifice more, raising the fuel line pressure to compensate against the increase in cylinder pressures. If the diaphragm is sized to give a 1.7:1 ratio off-boost, it's going to give a 1.7:1 ratio on-boost as well. It's a simple device.

This 1:1.7 is a 'mechanical theory' figure when used with N/A cars working with negative boost.

The ACTUAL effect with turbo charged cars with positive boost is to track the boost on a 1:1

Remembering one can shove theories around until cars come home - this is what actually happens!

Originally posted by Terry S

Without entering a mud slinging fight, both Ian & I had early FSE's, probably the first on Supras in the UK ( Ian, I assume it is the one PW put on?) Now mine from memory definitely rose faster than 1:1 on boost, as my fuel pressure went up to 70 psi when running 42 psi static & 19 psi boost. Maybe, just maybe, the early typer were different? They were not Supra specific parts then, but a WRX Imprezza part.

This sounds like their 'Racing' regulator

They have three

Racing (no way for soop)

Adjustable (One we use)

1:1 (which the subarus use with adjustable ECU's)

The only reasons at all to change from the stock regulator, as far as i can see, are if you are using injectors that are either designed to run at a different line pressure, or have a massive flow rate which you require to take advantage of. I am at a total loss to think why a stock engine, or one modded correctly would benefit from an adjustable regulator other than in the above scenarios. If a bit more line pressure is required for some bizarre reason the stock one can be tweaked, it's a common cheat in racing.

Originally posted by Chris Wilson

The only reasons at all to change from the stock regulator, as far as i can see, are if you are using injectors that are either designed to run at a different line pressure, or have a massive flow rate which you require to take advantage of. I am at a total loss to think why a stock engine, or one modded correctly would benefit from an adjustable regulator other than in the above scenarios. If a bit more line pressure is required for some bizarre reason the stock one can be tweaked, it's a common cheat in racing.

The benefits of improving responsiveness etc have been covered to death Chris - and they work!

And I would prefer a proper adjustable regulator rather than fudge by 'tweaking' the stock non adjustable regulator

Perhaps in racing - but not on my machine thanks!

Originally posted by Paul E

Remembering one can shove theories around until cars come home - this is what actually happens!

Agreed. If we are talking about different products perhaps some clarification about that would have been useful at the start, as it read like "the FSE valve" rather than "the 1:1 type FSE valve", and I've not found a source of info on the web yet that refers to anything other than the 1.7:1 version so I didn't know any others existed.

Ironically, I could only see a point to them if they did actually force more fuel out of the injectors while on boost. That would be a selling point, even if it's an atrocious way to alter your fuelling. Otherwise I agree with Chris, why change from the stock FPR? The only reason I've seen is that the stock one apparently doesn't give 1:1. Even if that were the case, the ECU mapping process would have been done around this and therefore the fuelling would still be correct. So putting in a 1:1 would make the car run rich.

-Ian

Originally posted by Paul E

The benefits of improving responsiveness etc have been covered to death Chris - and they work!

 

And I would prefer a proper adjustable regulator rather than fudge by 'tweaking' the stock non adjustable regulator

 

Perhaps in racing - but not on my machine thanks!

Paul, I think that under racing conditions engines are tuned so close to death that accuracy and longevity are huge considerations as one slip = blown engine and lost race rather than running a bit rough. I wouldn't call tweaking a stock FPR a 'fudge' when the word 'tweaking' is used in a race engineering context either.

Chris - how many race engines have you seen using FSE valves for improved responsiveness?

-Ian