Hey all I just thought i should relay this info through as it is very unusual and might help someone else in a roundabout way.

About 2 months ago I decided to fit a 1.7:1 Rising rate FPR to my magna, it wass running perfectly and i had one lying around so it seemed like the thing to do at the time.
Anyway, I tuned the bugger up, running in series with my stocko one to up the pressure only a fraction at load. The reason for this being it was a turbo one and wouldnt have worked really that well any other way the fuel pressure would have been nuts (super high up high or super low at idle)
Anyway, along goes about a week and the car has been responding really well, improved respose down low where i spend most of my driving hours, and so i thrashed the car a bit, as you do.
Suddenly, out of the pits of magna doom hell! Comes a terrible rattling noise in the bowels of my engine, all sorts of possibilities are suspected;

Tappets
Bearings
Piston slap!
Harmonic Balencer
Exhaust

Finally i settled on the idea of doing an oil change as it was due one to see what happened.
Nope. Not fixed.
Checked arount the engine with a stick to my ear to find the source of the noise to no avail.
Not pulleys, bearings, harmonic balancer or exhaust...
That left tappets and the dreaded piston slap...
Including the idea that it got louder with load and only happened sometimes, above 3500rpm, and at times on cold starting, i assumed tappets but reading the workshop manual it said not possible...
Not beleiving it could be piston slap either as the symptoms didn't fit i went to my local mitsi dealer, and had no joy.
As usual.
So I went to my local mechanic, and after myself and two mechanics had a powwow we thought it could possible be pinging...
Strange as I usually run BPUltimate...
Anyway, long story short, i removed the FPR a lo and behold, about a week later, the noise vanished. And is yet to be heard again!

Here is the speculation on what happened;

The FPR, running i series with the stock unit, always produced a richer than normal mixture.
The ECU, noticing my richer-than-normal-at-all-times mixture, went "ooh, lets lean that out!"
(I have reason to beleive it can actually do this! These ECU's can remap themselves it think!)
The FPR, providing an unusual fuel curve under load, accidently induced a leaner than should happen mixture above 3500rpm, thus ushering detonation!
I removed the FPR.
The computer, after 300 odd km went "WTF?!? I'm running far too lean! Better richen up!"
Car ran good again!


Now this may sound silly, but everyone knows about the problems where you adjust timing and the computer resets it to some horrible wrong setting again, same with idle speed, etc.

I also know for a fact that the misti workshop manual states that cars will run richer than usual for the first 500km, this is i beleive the estimated amount of time they need to learn the correct fuel curve. And of course other things... like idle, timing etc.

It may be possible then that rough idles may be caused my O2 sensors reading too lean and the car richening up? or reading too rich and idle leaning out...

My VR-X BTW has done 180,000 clicks and idles smooth as a dream and has tonnes of power... not a problem with it until of course i put a FPR on...
Now a thing to note is i set my FPR up completely differently to most magnas, and it was a turbo unit, so im not bagging FPRs... but this is interesting to note, and i have a feeling one may be able to richen the overall fuel curve over time simply by tricking the ecu into thinking the engine is running lean...

If this is true it also means over 500km a ecu should 'learn' to compensate for a pod filter, yes?

I would love to know what you all think, this is purely my speculation based loosely on circumstatial and first hand evidence, I wish i had had my AF ratio meter hooked up to verify these results but i didn't.

Hear from you!
Scott.

And that's why you don't run a Rising Rate FPR in series with the factory one.

If you want to run one (I have been for over 12 months and highly recomened them to improve throttle response), get the proper adaptor so you can run the fuel line straight from the rail into the regulator. Otherwise you end up with two different valves trying to regulate the same thing.

*edit* the FPR I'm running is also a 1.7:1 unit and had no problems with it on 2 different N/A TJII magnas. Set the base (idle) pressure to between 35-40psi and have never had a problem or run rich / lean as proven on numerous dyno runs.

Hmmm odd one.

Basically a RR FPR on a NA car is pointless, but is okay if you use it to adjust the base pressure. Being a rising rate, it will rise the fuel pressure 1.7psi to ever 1psi of boost pressure, and im assuming you dont have any form of supercharging so the RR section of the FPR isn't being used. Again though, it will work and can be used to set a base pressure and still controls fuel pressure on vacuum and WOT but all you needed was a regular FPR with adjustable base pressure as they all have vacuum diaphrams.

If it were running low pressure, than being in series your OEM unit would have just held the correct pressure. You can only INCREASE pressure with a second FPR in series, so you could only have been richening the mixture, which ill get to next.

The ECU has its fuel and ignition map it reads from. When TPS is below 50%, and there is low load, the ECU doesn't use its mapped values to control fueling, it uses the o2 sensor to determine fueling(closed loop). For instance the o2 sensor reads lean or rich, that is it, no specific value. The ECU constantly on the fly adjusts the mixutre very slightly from rich to lean, so that on average, its spot on the stoich mark. If a certain load is exceeded or a certain TPS reading triggers, then the ECU jumps back to the fuel map(open loop) to work out what it needs to do. Thats because when giving it some stick, the motor will not be running a stoich mixture for various reasons.

The ECU is either in closed loop or open loop. Closed loop is when its getting feedback from the o2 sensor and using it, open loop is just reading rpm, temp, load and a few other things and looking up on the map how much to fuel, and precicely fueling for that instance. The ECU assumes constant(per vacuum anyway) fuel pressure, and while in open loop mode can not tell there is higher or lower fuel pressure so it will just open the injectors for the certain amount of miliseconds it was programmed to for that instant. If there is more fuel pressure then you will run richer than tuned for, similarly with less fuel pressure the motor will run lean. HOWEVER in closed loop mode, if you have higher fuel pressure, the ECU will adjust the fueling so that it varies between lean and rich which will retain fuel econ.

I dont really know what the ticking noise was, but be assured if it wasn't a knocking noise then it was probably just a sticking tappet and completly unrelated. Still odd none the less.

Sorry about the novel with no answers but it should be able to clear a few things up, plus your post was still bigger :p

:clap:

Jason,

One of the best explainations I have ever read regarding closed loop / open loop operation.

Thanks mate!!

Thankyou BB, I do A LOT of ECU work in NQ and help out the designer of the Adaptronic ECU. Its also why I question the use of piggyback units when an Adaptronic, with all the features of a $2000+ Haltech, can be had for less than $1000

What gains can be made from this mod? And about the question on the ECU adapting to POD filters, i am interested in this also.

A adjustable FPR can serve to be a primitive way to adjust the whole fuel map up or down, allowing you to lean out the motor to produce more power. OEM tunes are generally pretty rich, to compensate for the idiot factor of drivers, malfunction etc etc. They run around the 11:1 mark even on NA cars some times, which is too rich for even the most fragile of motors. Leaning out the mixutre to 12.5-13:1 on a NA car is considered acceptable if no detonation occurs, and can unleash a fair amount of low down torque and widen the torque curve up top, causing a later decline in power in top end.

Simply putting on a new FPR is not really a good idea, as you can just as easilly reverse the effect, or worse distroy the motor. It needs to be done while on a dyno so that the FP can be set and locked at the right pressure to lean the motor out slightly but not too much.

It is still a bandaid solution to fitting a new ECU which you can program to run lean at every single instance insteady of just shifting the WHOLE spectrum up or down. It does work in some cases fine, though I wouldn't recommend it without dyno tuning.

What gains can be made from this mod? And about the question on the ECU adapting to POD filters, i am interested in this also.
The ECU wont adapt to the pod filter, it's a case of the MAS that magna's run not being able to read in the swirling air accurately. The ECU will then take this reading and use it, so the best way would be to somehow get an aftermarket air sensor that will detect swirling air properly, though i don't think anyones done that yet.

The ECU wont adapt to the pod filter, it's a case of the MAS that magna's run not being able to read in the swirling air accurately. The ECU will then take this reading and use it, so the best way would be to somehow get an aftermarket air sensor that will detect swirling air properly, though i don't think anyones done that yet.



That would be a really good thing to look into. Do the Japanese Diamante's use the same sensor??? There has to be something out there that reads the distortion of swirling air.

IMHO the best bet would be to leave the airbox in and get a pannel filter, as pods dont make any more power/torque. They do sound cool though, which is why I had one fit for a while lol

hey can tappets make a rattly noise that gets louder with revs, appears cold and dissapears after a few seconds, and goes away when you drive the car sensibly?