Fuel Pressure Regulator lag. A15 SOHC

[MMamdouh]

i think so too

MMamdouh

[RichieOzzie]

Ok, seems good, BUT... One of the ways the manufacturers use to control fuelling is with the FPR.

The pressure is a theoretical minimum, BUT CONSTANT for the engine to run with the injectors being pulsed at a certain rate. This can then be increased by increasing the pulse width time of the injectors, as in opening them electrically for a certain amount of time.

All good, but what happens if the FPR is a little slow, or in-accurate.... which is what happens with the cheap one used as OEM items. They fail/& are deficient on response, accuracy, and sensitivity. (Not good, but the engine will start and run off the production line, and that is what counts)

So, bearing this in mind, increase the pressure at the injector tip, and the fuel by volume being forced through them will increase slightly, but non-the-less, enough to alter fuelling to higher ratio.

Economy/stoichiometry is known to be chemically 14.7 parts of air, to one part fuel 14:1. This is the ideal chemical ratio of fuel to air for it to burn completely & efficiently. Unfortunately, accelerating needs a little bit more fuel as we open the throttle, and give the engine more air. We open the throttle, and "BAM", the ratio is 28+:1 of fuel, which is weak... too weak, so the injectors open rapidly, and faster, and fuel is increased according to the metrics set in the ECU, and it tries to get this stoichiometric ratio back to 14:1, using the Oxygen sensor to tell the ECU how far out it is, The ECU then computes the opening pulse of the injectors to suit, until it gets close.Read here -> http://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratio (Here you will see the word "Lambda", which is another name for the sensor we call the O2 sensor)

The sudden increase in fuelling as the injectors open is controlled with the FPR as the master at this stage. Unfortunately, the OEM one neither... is responsive enough, Accurate or sensitive, and give s a "Near" amount as it can do.

Now, Make this FPR more accurate etc, and you then have something running nearly as quick as the ECU can control the injectors. This way the fuelling is more accurate, and will produce more torque evenly. Imagine that at 4000RPM, the cylinders ar firing at quite a rapid pace, and one or two mis-fires, or weak combustion(s) in the cylinders will not be too noticeable, or you may just feel it as slight hesitation.

Power per stroke as the engine pulls will be less than it "COULD" be. Even, say, for instance, the engine has 10% bad/weak combustion cycles as you open the throttle. " B.M.E.P. will be askew". BMEP is the singular most important thing in Internal combustion engines, read this -> http://en.wikipedia.org/wiki/BMEP

Equate all this to power/acceleration as the good combustion pulls the bad combustion(s) along, until it gets right, then all the torque you have missing, and all the effectively wasted fuel!!!, ...... if it burns slow, or un-regulated, you may as well have not put fuel in the cylinder at all!!

So, here's where it all works better. Burn the fuel more efficiently, and you will have more power to pull the car along.


So, I know the Injectors run at 33psi at idle, which is what the ECU knows to be good, and the O2 sensor cannot see. The O2 sensor needs to be at around 630 degrees before it starts to work... unfortunately at idle, the xhaust gas that flows across it is way below this temperature. This actually is important, as the ECU only KNOWS that at a certain engine temperature, the injector pulse is as it is programmed, it cannot do any better(unless you convert it to a 3-wire heated item).

The engine is fuelled according to a point on the ECU map, and nothing else. Increase the pressure at the injectors, and you will increase the fuelling too. Removing the vacuum pipe and blocking it makes 43psi at the injectors which equals rich fuel mixture.
All good, but when the engine is warm, and idling with a load on it, for example the Air-con, or the Auto Gearbox in "D", the the idle will become unstable/rough, and the IAC Idle air controller cannot operate quickly enough to establish a smooth, efficient idle.

You need to set the base(idle pressure to around the 33psi mark.

Here's how I did it.
Start engine and get it warmed to operating temp.
Block/remove the vacuum hose, and you will note the pressure goes up at this point. Turn the screw on the RRFPR Rising Rate Fuel Pressure Regulator to around the normal engine running fuel pressure of 43psi(3 bar), lock the setting in.
Replace the Vacuum hose, and you will see the pressure drops down to the 33psi IDLE pressure, and the idle will smooth out for you at this point.

Now, what we have done is set the maximum fuel pressure to 43psi, and the idle pressure to 33psi by using engine vacuum, which, in theory is what the engine needs. You can see this if you quickly open the throttle, the gauge will dart up toward the 43psi point, which means she is fuelling well.

Just taking off the Vacuum hose is good for pressure, but the fuelling will be out of control, and more than likely, the O2 sensor will see this, and advise the ECU to remove fuel, as it is too rich to be economical and efficient. -Not what we wanted eh???

So, what we have done, by just putting a FEW more PSI at the injectors when we open the throttle, is increase the fuelling ratio a LITTLE!, which is what was needed on eco-friendly engines like the Lanos.

When you allow more air to get drawn into the engine too, it makes for quite a lot, for a little spent. See the Air-box feed pipe diameter when compared with the air-box outlet pipe!!

drill a few 1/2 inch holes on the inside edge of the air-box, I have 5 in mine. It eliminates the restriction of air getting it to the manifold/Engine. Combine this with 2psi extra at the injectors, the O2 sensor will see the extra fuel needed as the air flow by volume has increased..... Bam, more torque, better breathing, better response.

All together, you can also see that this mod will increase efficiency by making more of the fuel burn more accurately, which gives increased economy.

So.... More economy as proven many fold. More Torque, which is the force that turns the wheels more strongly.

Cheap power increase,.....THEN Imagine Forcing Air into the engine, and how the dynamics change!!, say Turbo or supercharging... aka Forced induction!!

.... but do not over-fuel the engine at idle, as the ECU cannot control it. You have to run the vacuum pipe to the FPR.



Hope this helps clear-up all the vague parts of this modification, and explains why it works for people.

Combine this with MMamdou's timing change to the engine in this forum, with a little thinner oil, and then do a side-by side with a non modded car. These four changes do not change insurance, safety or design regulations, so its a free for all to do.

Remember, it will never be a formula one engine, but add little changes to it here and there, and they all add-up to an exiting change to the cars driveability.

[RichieOzzie]

Just a place I found the information readily available a click&Go for the pressure increase versus volume of fuel increased.

Try this -> http://www.witchhunter.com/injectorcalc1.php4

The bottom of the page has a Fuel flow calculator, which, if you put in 43.5 as the so-called stock pressure at full tilt, and then in the next box, put what you turned the pressure up to in the second, you will see the volume as a quantity of EXTRA fuel placed into the cylinders.

I run 47 psi, and the % of fuel increased is in credible.

NOW.. take the Idle speed pressure of 33psi, and put 47 on that, you will see the engine is Waaaay over-fueled a idle to run smoothly, and the ECU cannot cope with trying to regulate this.

This is why I say to increase the full-on pressure with the vacuum pipe OFF. Set it to around the 47psi mark(depending on accuracy of gauge remember), lock it down, and then replace the vacuum pipe. IT will drop to close to 33 psi, which is good for idle.

Easy?