Ok all RPW talk about is a Fuel Pressure Regualtor kit. I know it increases the fuel pressure, but it's just a valve isnt it? So it increases the fuel pressure, but the injectors are only set to let in a certain amount of fuel arnt they, cause the computer set's the amount. So what's the point of it? To me it's a waste of money cause u need to modify the computer to change the fuel input, well thats the way I interperate it.

i have often thought this to myself! :doubt: (glad to see im not the only one!) :redface:

This is how I see it, wrong or right ?

Your ECU varies the electrical pulse width sent to your injectors thus varying how long they open and close for.
By increasing the fuel pressure you are going to improve atomisation and put more fuel into the chamber for the same pulse width as you would with a lower pressure. eg say the injector opens for 1 millisecond at 150psi injecting 1.5mL compared to 1 millisecond at 100psi injecting 1mL of fuel, these figures are completely made up as an exaple only and not based on any math at all.
More fuel, bigger bang = more power.

eg say the injector opens for 1 millisecond at 150psi injecting 1.5mL compared to 1 millisecond at 100psi injecting 1mL of fuel, these figures are completely made up as an exaple only and not based on any math at all.
More fuel, bigger bang = more power.

yeah but does'nt the compter adjust the fuel going in according to the situation regardless of the pressure? cause it tells the injectors in inject a certain amount does'nt it? The reason I say that is cause different cars would have different fuel pumps with different pressures, but there still putting in the same amount of fuel?

Also is there any proof of this acually increassing power? Or is it just what RPW guys said

they also affect the richness of the mixture i think you could steal a kw or 2 from that but i dont think the ecu actually know how much fuel is going in just how long the injectors are opening for and theyd have preset data....

Well After The Big Bang The O2 Sensor Is Going To Say Hmmm In Rich Ill Lean Off Now So Yes There A Wast Of Money..............and More Fuel Does Not Mean A Bigger Bang...14.7 To 1 Air Fuel Ratio Is The Best Bang...so If Fuel Is Increased It Needs More Air

Ok,
The theory is more pressure to get better atomisation. This will then allow better burn thus more power.

You will be able to burn slightly more fuel due to the better atomisation. Any one who knows how the o2 sensore works will then know that under cold running, heavy load and acceleration that the ECU will ignore the o2 Sensor.

And while 14.7.1 is the ideal air fuel mix it does not mean most power either.

In my Turbo rotaries I used to have a slightly rich mixture inder high boost to enusre that combustion temp was cooler.

Running slightly higher fuel pressure in a NA motor can have small benefits. The ECU does not know how much fues is passing though the injectors, it just assumes that at the standard fuel pressure, i will open an injector for xxx/ms and this is how much fuel will be delivered. The o2 sensor, will if the condtions are right then tell the ECU "too much fuel, back off" and then the injector pulse is shortened. This all happens in a split second and takes into account air temp, air volume, throttle position, revs, engine temp etc.

Hope this helps

If Your Running Turbo You Need More Fuel Because Your Putting More Air In To The System And Ive Never Seen A Rotary Run Anything Other Than Rich

The other point about the RPW FPR that everyone seems to have missed so far is that it is a rising rate regulator. That means that as manifold pressure changes the amount of fuel pressure increases at a rate disproportionate to the manifold pressure change which means more fuel faster and less flat spots on acelleration.

Of course an after market FPR comes into its own when you've done enough mods that you're hitting 100% duty cycle of the injectors at full load.

14.7:1 AFR is the ratio required for the most 'complete' combustion of air and fuel. That's not the same as the ratio for best power.

14.7:1 gives best compromise between power and good fuel consumption which is what you want when cruising at a constant speed. Also this is the best mixture for emission control using a cat converter. Max power comes in at about 12.5:1. Any richer than this actualy starts to loose power, but because it burns cooler it is often done to protect the engine.
Cheers

The other point about the RPW FPR that everyone seems to have missed so far is that it is a rising rate regulator. That means that as manifold pressure changes the amount of fuel pressure increases at a rate disproportionate to the manifold pressure change which means more fuel faster and less flat spots on acelleration.

Of course an after market FPR comes into its own when you've done enough mods that you're hitting 100% duty cycle of the injectors at full load.

14.7:1 AFR is the ratio required for the most 'complete' combustion of air and fuel. That's not the same as the ratio for best power.

Close but not quite.

Your manifold pressure will never go above zero atmosphere unles you have a turbo etc.

The RPW, which is simply a Malpassi or similar FPR, is compatable with a turbo however is not needed. A simple single diaphram FPR is more than enough so long as as it is adjustable which is the main idea for fitting this. (no I am not bagging RPW).

If you have done mods, then there is a good reason to fit this to get an adjustable and reliable pressure in the fuel system.

Isnt the only reason o2 sensors aim for 14.7 is this is because its the optimum opertating range for the cat converter and at a certain point of load or tps reading the ecu disregards the o2 and runs of the maps. Best power is usually around 12.5 and best fuel economy while crusing is around 16.1. I run a fuel reg, mainly coz the standard one was over run by my larger pump.

Your manifold pressure will never go above zero atmosphere unles you have a turbo etc.
Surely you mean it'll never go above one atmosphere? :D

Are you also saying RPW's FPR isn't a rising rate version?

Now I get to clarify - all these people clarifying - is anyone else confused yet?

The above posts are true - the units we are use are a rising rate. They are the FSE brand not a normal malpassi unit.

The difference is that the FSE unit is a modified Malpassi which is a rising rate under vacuem, not boost which is what the majority of Malpassi units are. This means that under vacuem the fuel pressure relative to vacuem pressure is at a 1.7 : 1 Ratio. Once it reaches a boost condition, it reverts back to a 1 : 1 ratio.

A normal malpassi unit works the opposit 1 : 1 like stock under vacuem and then normally either 1.7 or 2.0 : 1 under boost.

The reason why they work on N/A cars so well and turbo cars to eliminate flat spots is that it increases the fuel pressure momentarily faster when you accelerate. THis riches up a factory setting called the "Fuel Pump Accelerator Section" which momentarily increases fuel to overcome the sudden increase in air until it stabilises usually as you evacuate the plenum chamber.

Of course you can also adjust the base pressure higher as well but we normally find on most magnas we set the pressure to 40 psi at idle (38 psi is stock) and this means around 3 - 4psi more fuel at Wide Open Throttle as well.

Yes it does provide better atomisation with higher pressures but realistically, over 45 psi it is on the multi disc style magna injectors not going to make a hell of a lot more difference.

I hope that explains it clearly? Did I confuse anyone else :nuts:

Thanks RPW dude that helps, so what is a approximate power increase with basic mods extractors, exhaust and CAI?

Thanks RPW dude that helps, so what is a approximate power increase with basic mods extractors, exhaust and CAI?

One of us must be confused........ cause from all the information I've read about these things - I'm pretty sure it will only improve acceleration, or throttle response which I interpret to mean "car gets off the line better".

No one has made any reference to the fact that peak power will be increased........ which I interpret to mean "peak power will not increase".

Agreed it is unlikely the FPR unit on a N/A car will result in a power increase. there woudl be a torque improvement at low rpms, throttle response (The leaner it is the more it helps) but as in actual KW no measurable gain.

As for what hp / kw gains from other mods depending upon brands, size of engine and other factors teh general rule of thumb is around 10 - 15kw at the flywheel as an approximation with the basic mods.

waist of money and does not make sence to want to put more fuel in ....

waist of money and does not make sence to want to put more fuel in ....
with all these ppl dishing out technical descriptions/arguments making them sound very convincing that its a good mod you just sound really stupid saying that...


got anything to backup what you say or are u giving advice to ppl from a gut feeling you have :doubt:

waist of money and does not make sence to want to put more fuel in ....

You are absoloutly correct there is no need to waste more money and add extra fuel - :nuts:


wait for it lol

its coming lol

nearly there lol

Unless the car is running lean or has sufficient modifications which has leaned out this particular setting. :badgrin: I think that has been stated sufficiently several times

ignoring throttle responce, does the fpr benefit with power output when a unichip is fitted and tuned to the cars current specs?

from my understanding, lifting the pressure of the fpr you can reduce the duty cycle on the injectors?

Lifting the rate of the injector pressure from say at WOT from 45 to 50 psi woudl reduce when tuning the car if required, the injector cycle from say 5ms to 4.75ms as an example.

Not really anthing to be concerned about as such, on most cars with teh greddys we find that we pull fuel out in some areas, add in others and some stay the same.

I finally got around to fitting my FSE Fuel Pressure Regulator today. About 2 weeks ago I fitted a K&N Pod at the end of CAI piping to the lower front bar, and after the novelty of driving around in tippy mode holding every gear change til 4,500+ wore off - man did I notice the dreaded <3,000rpm flat spot.

Wound the pressure in the rail up to 40psi with the help of the FPR and I'm confident there is a marked improvement in accelleration below 3000rpm.

Almost impossible to say that it makes much difference when the throttle is held wide open for more than a few seconds - but definetly a more immediate response when you first press down on the loud pedal.

Thats my experience anyway - just thought I'd share.