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I got a Supercharger on my ej22 now running about 6PSI.

It doesn't show any sign that it is leaning out the fuel mixture but im worried about it. I don't have any way of testing it at this stage.

Questions are:

1- Should i be worried? Im still running the factory NA ej22 reg at the moment. (Factory computer)

2- Should i use an EJ20T fuel pressure regulator? Will this thing do something cool and sort out any portential problems with this?

3- Will i have to get a aftermarket fuel pressure regulator and some how tune it. And how am i meant to tune it?

Thanks in advance
Dave

thinking about this a little - surely if the engine management components are up to scratch the ECU will manage things so long as the supercharger does not push (get pushed) beyond its parameters. Do EJ20G FPR's specs show a different operating pressure? The best air fuel ratio i have seen is a portable job that is so quick and easy to set up and put engine through its pace. I think it was on mainline.com.au - about $1800 . If you can find a good mechanic who has one....

Why not go for something like this:

http://cgi.ebay.com.au/Dynojet-Wide-Ban ... dZViewItem

I run a 5 wire wide band in my other car as a permanently installed tuning aid.
You can log data, view it at your leisure and take action as necessary.

A mob in Canberra known as Tech Edge sell some good TRUE wide band O2 sensing stuff and its what I have to tune my R33 when I get the Datalogit software .

Rule 1 . You can't properly tune an engines AFR with fuel pressure alone .
I know some love regs like the Malpassi rising rate one but all it proves is that the user doesn't have control of the injectors duty cycle and fueling .

More than half the fight with an artificially boosted engine is the engine management itself . Turbo engines are a different spec (cams/CR) so its not just as easy as grafting in a WRX engine management system .
One half ok way of doing things is using an interceptor to "bend" the load sensors (MAF AFM) signal to alter AFR , late management systems can usually tell when things are not as they should be ie AFM showing high voltage than it thinks it should have and the usual response it to go RR - rich and retarded timing . The rich AFR's you can live with to a degree but the retarded timing kills performance . Interceptors can work ok but you got away with more variation on dummer systems like L's have .

You may have to look into aftermarket engine management systems .


Cheers A .

im i right in saying that rising rate fuel pressure regulators are used for charged vehicles and normal ones for N/A?

also do people get better combustion/power from adding one of these to their system?, i understand u'd prolly need an aftermarket ecu. or to get them to work properly do u have to retard timing etc.

on the lib rs forums someones selling cables and software for your computer which plug into the data link cable in your car. Just shows what the ecu's doing in real time. Think they're 50 bucks or so

Good to see I'm not the only one using Tech Edge.

Factory ej20T regulators would have to be raising rate wouldn't they??

Dave

Subafury wrote:im i right in saying that rising rate fuel pressure regulators are used for charged vehicles and normal ones for N/A?

also do people get better combustion/power from adding one of these to their system?, i understand u'd prolly need an aftermarket ecu. or to get them to work properly do u have to retard timing etc.

This method of upgrading my FPR to an adjustable one got around my problem of my previous turbo wagon leaning out, not the best way as mentioned above and programable ECU would have been required if the bigger turbo and intercooler was to be fitted to my EA82T (hence another reason it was sold). This FPR and with another inline fuel pump got the AFR back to where it should be. I had a Malpassi adjustable FPR fitted and the tuning shop had the diagnostic tool with end pipe O2 sensor to measure it under load.

if u get one of the cables or make one
u can use a laptop and the select monitor program to see what the a/f ratio is

as long as u didnt strip the data pulg from your ecu loom when u cut it down

Yeha i did strip it out... but i should be able to hardwire a data lead in to go straight into a laptop.

Dave

http://www.vwrx.com/index.php?pg=selectmonitor
for schematic
about a page down

Fuel pressure regulators or FPR for short .

Most good factory workshop manuals give a bit of insight on how they work .

An EFI FPR is designed to give a constant head of pressure over whatever pressure exists in your inlet manifold .

Before I go deeper you must understand that there is no such thing as a "negative pressure" , most in general society are conned into believing that atmospheric pressure at sea level is zero and obviously thats not the case - other wise you wouldn't be reading this .

A REAL pressure gauge reads ABSOLUTE pressure - meaning everything above a total vaccum which is REAL zero . You will sometimes see pressure figures in PSIA - A for absolute . The silly gauges read in PSIG meaning PSI GAUGE .
A PSIA gauge will show 14.7 psi/1 BAR/100 kpa/1000 millibars (all means the same thing) at sea level . A PSIG will read zero at sealevel .

Meanwhile back at the FPR . Virtually all petrol engines run in a low inlet manifold pressure state at idle and light load , this is because the throttle valve won't pass all the air the cylinders are demanding because we are slightly strangling them to regulate power output . Our FPR regulates off inlet manifold pressure so its diaphram pressure will also be below atmospheric pressure . Remember that the spring loaded diaphram valve sets the static fuel pressure usually somewhere around 36-38 psi . Lets just say that your crusing down the highway at part throttle and you manifold pressure is 7 PSIA , 7.7 psi below atmospheric which is 14.7 PSIA . The the static spring pressure in your FPR is eg 36 psi so we add the two together = 43 PSIA .
Now for whatever reason you decide to floor it and your inlet manifold pressure rises to atmospheric , the FPR sees this and adds the constant 36 psi to atmospheric so 36 + 14.7 = 50.7 psia . This is how it would work on an NA engine but yours has a turbo so it can generate pressure greater than atmospheric ie 14.7 + 10 pounds (PSIG pounds) = 24.7 PSIG . In this state to the 24.7 PSIG you can add the regulators constant 36 to get 60.7 PSIG .
By this I hope you can see that all the reg does is supply a constant in this case 36 pound head of pressure over that existing in the inlet manifold - no matter what it is in relation to atmospheric pressure .

Domestic blis (school bus) calls , more later on rising rate and how FPR pressure relates to EFI systems .

Cheers A .

Chapter 2:

Fuel pressure in relation to manifold pressure .

At idle inlet manifold pressure will be very low ie maybe 3 PSI-Absolute . With our FPR's constant this gives 39 PSIA fuel rail pressure or in silly graduations 24.3 PSIG (PSIA figures will always be approx 14.7 lower than PSIG figures because thats the difference between Absolute zero and Gauge pressure zero) .

Any way in an idle state the engine doesn't need much fuel or injector open time if you like . The fuel pressure is about as low as its ever going to be and this keeps the injector open time and spray patterns manageable .

For above idle conditions manifold pressure will rise and so fuel pressure rises by the regs constand pressure (pressure head) above it .
So really the system runs in "regulation" with fuel pressure low at light loads and higher at high loads . It all helps the injection system along with the computer driven signals to the injectors to vary their duty cycle or injector open time .

Enter the dreaded Rising Rate FPR :

EFI computers have always been a mystery to some and those migrating from carburettors innitially felt cheated by the inability to vary fueling for non std applications . It occured to someone that if the fuel rail pressure could be made to rise faser than the inlet manifold pressure the dumb computer and injectors would pass more fuel and let the engine have lower (richer) air fuel ratios . This is one way to make that happen but its crude because even at less than high load the fuel pressure is higher than the computer thinks it is so the system is now not running in regulation . Also the fuel pump has to work harder to push the greater fuel pressure into the system , a characteristic of pumps is that the more pressure they are forced to make the less volume they can move . In std form the manufacturers usually don't spend any extra to fit a higher than std pressure capable EFI pump because in std form (the way the vehicle is supplied) it doesn't need it .

If you use one of these RR FPR's you really should think about a higher capacity fuel pump because the god knows how old std one ain't gonna like being given purple hearts late in life . You also have to be VERY sure that your fuel hoses can stand up to the increased pressure within them , if it springs a leak an is ignited by a hot exhaust manifold/turbo/ignition system and you powerless to put it out the vehicle WILL burn to the ground . If it doesn't take you or anyone else with it you may be forced to watch it go up in the middle of nowhere . A bitter pill and if the missus/GF/kids etc are with you ...

The hardest thing to come to terms with in non std EFI apps is understanding that the right way to go about it is larger injectors and a computer that will pulse them properly to give appropriate air fuel ratios - and ignition timing signals . The solutions can be aftermarket computer systems / say a plug in like Apexi does for some cars eg their PFC though in Subie that would be to run an EJ turbo engine . You can get away with interceptors sometimes to "bend" the air flow metres signal but the variations you can make will be limited by how smart the ECU is . Things like the E Manage or even the Jaycar kit - Digital fuel Controller , can be used to do this .

One downside to late model cars is that they use the computer to do other things like A/C control and or some electronic auto gearbox logic functions so its sometimes not an option to replace it with something non std .

One last option is to find some tuning business to reflash the std computer and upload non std injection and timing maps - thats if your car has a late sophisticated engine management system like most current cars do nowdays .

I hope I've given a bit of insight into EFI systems and some potential traps . Don't underestimate the electronic hurdles to overcome and understand that the manufacturers deliberatly make it diffucult because they don't want you playing with it - bad PR if you hurt someone is bad for their image and future sales . On the positive side the aftermarket army is alive and well and proving to be an equal match to the electronic police . For example Ford Australia claimed the aftermarket would NEVER crack their XR6 turbo engine management system and retune for greater performance . The electronic underground said "oh really" and 12 months down the track it was so thoroughly cracked that no one ever considers aftermarket computers on those cars .

All I can hear is snores so I'm gone ! Cheers A .

Very interesting... thanks for that. I will read it again later... i sorta got lost.

Dave