As the title. What meters the air flow into the engine to adjust fueling, does it rely on the Lambda sensor reading to know if the air/fuel mix isnt lean/rich?

works on MAP and TPS iirc.

Cheers, where might i find out what that means? (serious question, not being sarcastic) I just want to find out as much as possible about ECU remapping before making a definate choice as to which path to choose.

Best route is to do a search on "link", "ecu remap", etc. There is a wealth of information around these topics.

Works on the speed density principle ie engine revs and boost (or vac)with a throttle proportioning algorythm in addition, basically you then map using load (boost) aginst rpm using VE as the level. The boost/vac is read in absolute pressure.

Bob would it be better to take the maf out and put a bung in it when fitting the link ecu because last time i put my car back to standard the maf had blown.

See you in 2-weeks Bob

It would be better to replace the maf unit with a tube of the same internal diameter... that way the whole maf is safe sitting on a shelf and the tube should be less restrictive to airflow than the maf with a bung might be.

Wondered if all the guys who put their JECS back in and find the MAF has failed have it failing because it is not powered by the ECU to burn off deposits whilst the Link is running the car?

Completely off topic -

however just like to say:

Link (and other aftermarket ECUs) = 2d map
Subaru OEM = 3d map.

Reprogramming the Std Subaru ECU is a better option, surely?

Chris depends on whether you count the map contents as a dimension or not. Personally I would say that they are all 2d because they have an x and a y axis which are load/boost/airflow/TPS or some combo vs RPM. So called 2d maps are IMHO just say a single column table rather than a single value which is more like a parameter. At the end of the day it is all terminology, but I have no access to anything which I would call 3d, although some people would call a 16 * 16 table a 3d map, some ECU manufacturers would too, but I can't see any dimensional differences between the Link and JECS.

The hot film maf doesn't burn off deposits in any case, only the hot wire and if anyone has a Link then they can quite easily remove the cartridge, I tend to do that for them if its a MY99-00, the earlier hot wired mafs can't be removed like that but the whole thing can be done away with in that case.

Any map with an X,Y,Z map is 3D, that means Link, Motec, Jecs, Gems all have 3D maps, and all also have 2D maps as well which only have an X and a Z.

I would be interested to hear Bobs thoughts re- removing the MAF or replacing with an unrestricted tube as I have, like others, wondered about the implications of not powering the MAF. (I have replaced the original ECU at MOT time once so far with no problem)
JohnD

Point taken John - & you're probably right - it may be just terminology.

I just think that too many people simply ditch the standard Subaru ECU (without a second thought) for expensive after-market ECUs, which IMHO are sometimes less sophisticated than the standard OEM item (after all the Subaru item is capable of handling hot-cold starting conditions - different ambient atmospheric pressures etc etc).

At the end of the day - I'm sure you'd agree that its the quality of the mapping itself not the ECU that equates to a good tune.

It's one of my "bug-bears" that too many owners are often parted with their money for a new ECU & Remap - whereas this would have been better spent on the mapping itself utilising the standard OEM ECU - in fact they might be surprised to get better results.

Just MHO.

Chris

John, no problem removing maf completely ... I have ... factory ecu's are great within their limitations ... trouble is I found out what that is ... as soon as I can use it again I will do.

Actaully the ecu limits are currently defined by the parameters that can be accessed for change in the case of the Jecs so its a bit unfair to imply otherwise.

It is how to "creatively" manipulate a few choice inputs? MAF signal... bigger MAF sensor, port the MAF housing, throw on an APS etc and of course we have the scaling map. With the MAP signal if using a 3 or 4 bar map with a 0-5V output could we not just redefine our "multiply by 0.155 to get absolute boost" and work out the new conversion for a given sensor and change all the maps (at least the ones we have access to) to suit? With an appropriate MAF and MAP scaling we could surely make use of our load window up to 56 with a bit to spare for overboost scenarios and safety run-off? Boost control would surely just closed loop in the same way. Atmo compensations seem fully adjustable if the calibrations are not entirely clear.

I was thinking that 550s on a 2.5 would idle and start quite nicely since the compensations would be right :D Arguably 550s are not big enough, but are we changing our minds on the safety of high injector duty cycles? I am also considering the wisdom of going over 400-450 BHP on an Impreza anyway for what is mainly a road car... since the streetable transmissions and clutches we have available are good for that range with some reliability. On Andy F's car it has plenty of torque to slew you about the road in the dry in 3rd gear at some very interesting angles. Of course the pursuit of power of itself is one exercise, but it is also nice to make a balanced car.

I think a 350 BHP Subaru is really quite benign and forgiving. Yet to see what I think of the 400-450 BHP range... does it become normal :rolleyes:

Certainly with your achievements with 2.0, it does question 2.5, but for road use, I am thinking of a 2.5 at relatively low boost (say just 1.2 bar on an 05/06) for a nice torquey motor.

First I want to run 2 bar boost, second I did not max the maf sensor, third I did max the engine load value ... thats down to running the boost. So there is no way I can use it at present, 740cc injectors are hard enough with the std compensations in place, running the last 0.6 bar boost on one set of load lines is just not a goer. With access to some compensations and the map sensor callibration I'm in business again. (I hope)

The trouble with power is it does become normal, its odd, great big adrenalin rush when it first arrives, after a few thousand miles even 450bhp feels slow again ... daft I know but you do adjust to it. My car is no different to drive than before, very progressive and tractable, just don't need to use more than 50% throttle. More throttle than that feels like a catapult mind, only down side is that it is very very easy to get it totally out of shape in the wet (and dry in the lower gears) !!!

Other "side effect" is you don't need to prove anything to anyone cos you know you will win !!

God damn technical guru's! ;) My head hurts.
Cheers for the earlier answer.

Agree, but then I would do ;) :)

Re the 3d thing - you can produce a 3d image out of the map. I suppose you could of course have RPM, load, temperature (eg charge or coolant) with a lookup for injector or ignition timing. Maybe that would be a 4d map in some books. And also a complete ba$tard to map :eek: Also the extra dimension would probably be somewhat redundant because you could just have an interpolated map of charge temp vs retard and keep your main map simple. But then at 2500 RPM on cruise after a hard thrash with a high charge temp you may not want to pull the timing down since detonation would not be your limit to timing any longer. But I would rather not map such an arguably excessively complex system, and you would struggle to actually put good numbers in it since you can't control the charge temp to map it so well. I'm waffling now, sorry.

[Edited by john banks - 2/4/2003 10:19:01 PM]