john banks

Are there any that come with a Subaru plug? What is the voltage scaling on them? (ie what voltage at vac, atmo, 1 bar, 2 bar?)

The Phase II JECS ECU saturates the MAP reading to $FF at 4.74 V approx, making the factory sensor good for about 1.73 bar boost with this ECU. 1.91 bar would be that maximum out of the Subaru sensor even if the output went as high as the 5 V supply, so a new sensor might be needed.

Anyone know if MAP sensors can swing their output voltage to the supply rail and if they stay linear?

Another complication is that the MAP input seems to influence the load as well as TPS and MAF after all, so using lower voltages would be nice. My MAF voltage at about 350 BHP is only 4.5 V so there is a fair bit more to come yet from the MAF sensor at least with an APS induction kit (saw over 4.7 with the airbox).

[Edited by john banks - 1/18/2003 3:47:18 PM]

Claudius

What's Phase II JECS ECU?

As for the voltage outputs, have you tried checking the manufacturer's website? Sorry if this sounds dumb (but that's me )

john banks

Tried looking up the Denso parts number previously with no joy. Just have again and still no joy just a very poor block diagram of gasoline engine management

Phase II JECS I mean the ECU in MY99 and 00 UK and STi/P1 cars.

[Edited by john banks - 1/18/2003 4:04:52 PM]

JamesS

John,

Any idea what effect, specifically, the MAP input has?

john banks

Not my data, but apparently at very high boost it pushes the load value up meaning that the ECU is reading from different areas of the map, even at WOT and the same MAF voltage. Vehicle speed may also play a part it seems. The maximum load value is about 56.5, presently I am using about 50, and I hope to add 75 BHP yet

The hope is that by keeping the scaling on the MAF and MAP down then I can still get useful boost control and timing/fuelling resolution.

JamesS

Interesting....So FCD and running 1.2/1.3 bar vs FCD and 1.5/1.6bar means that the latter is using lower load sites than ideal?

john banks

Well, ideal means a bit leaner and more advanced - sounds quite good to me (within reason).

pat

Phase II JECS almost seems like an oxymoron... If memory does not decive me, only the early Phase I cars had a Unisia Jecs ECU, later Phase I and early Phase II had Hitachi ECUs and New Age cars run Denso engine management.

As for MAP sensors, the easiest option is to get a Weber Marelli APS/05 3 bar sensor which scales linearly and will read 3 bar absolute, just need to recalibrate the MAP sensor calibration in the ECU. It won't plug in directly but a good quality (gold plated contact) harness is available over the counter from your friendly local Ford dealership.

Cheers,

Pat.

john banks

Pat the MY99/00 ECUs for UK, STi and P1 all have Unisia JECS
labels on them.



Thanks for the lead on the MAP sensor.

Pavlo

The weber sensor goes to 0v at 0 absolute pressure. SO unless you can change the multiplier AND offset in the ECU it will lead to an engine check light, because the ECU thinks there is excessive vacuum.

Calibration isn't much of an issue, just a PSU, DVM and manual pressure gauge you trust.

On the pre97 ECU you can get away with just the later map sensor, despite atmo point moving from 2.6 to 2.3 volts on the sensor.

You could, if so included buy a sensor unit, and make a custom amplifier to rescale the output after the 2.3v level.

The MAP doesn't change the load paramete in the ECU at all, I proved this to myself by manually adjusting the pressure to the MAP sensor whilst the engine idled, no change in load was seen. Moving the throttle sensor without moving the butterfly did increase the load, as did revving the engine without moving the throttle sensor.

edited to add, www.fuelparts.co.uk do the map sensors and plugs etc, they distribute through PartCo, but you can download the catalogues etc from the website.

Paul

[Edited by Pavlo - 1/18/2003 8:35:44 PM]

pat

John,

I must be getting confused, I know for a fact that Subaru used Hitachi ECUs, perhaps the board is Hitachi, or perhaps I'm thinking of a different model car... like I said, "if memory does not deceive me"... there's some weirdness going on, allegedly the MAF sensors are Hitachi but they have a JECS label on them, and I recall seeing a throttle position sensor which has Hitachi on it! Must be mongrels or something

The Weber Marelli sensor can be mail ordered from Burton Power and Demon Tweeks, both usually carry a healthy stock level

Cheers,

Pat.

ustolemyname??stevieturbo

iTrader: (1)

Not sure how much Burton etc charge for the Weber Map sensor, but I have seen them for around £50 on offer in some of the ford places. Demon Tweeks arent the cheapest place around.
A Quick scan through one of the ford magazines should give a good supplier.

Bob Rawle

The data came from me, basically I have maxed out the maps on the jecs with my latest iteration of engine spec. without maxing the maf although I run it close so I suspect that map plays a part in load calculation. It means that I run one set of values for approx 15% of my engine load, depending on conditions I also achieved the 56.5 ceiling of engine load using only 1.2 bar of boost at low revs. (that I haven't sussed yet)

John, been looking into it since I had the problem, Marreli will work also there is a GM 3 bar that I use with Link/Motec. I am still not 100% convinced that the map sensor is part of the problem though but this will add support, or not, to the theory. After discussion with Steve D its also a possibility that speed is part of the equation so an experiment to remove my converter is in order. Map callibrations are linear but if map affects compensations then those are not all available.

The callibrations are linear but the range is only 0.2 bar more so not sure that this will help, boost for boost the output is lower so maybe but, again, compensation maps we can't get at will be affected.

Pat the ecu's are definately from Jecs as John says.

Pavlo

Bob,

I don't believe the MAP affects the load figures, but MAF certainly does. I've got a MAF sensor from a 300ZX on the basis that it has higher airflow for the same voltage.

If you were to use such a maf sensor, then in theory, 56.5 on the load parameter would equate to more airflow. I've yet to test the MAF sensor, but I do have a curve for it. I think the numbers are arbitary, but the I beleive the shape of the curve is the important factor. I will need to compensate with fuelling constant, which I beleive you don't have access to at this time for 99-00.

There is a company in the US that does custom made MAF sensors, basically the same sensor element in a larger (up to 8 inch!) tube. With some testing, running the OE sensor in a larger diameter tube could work.

Paul

Andy.F

When I ran with my pneumatic FCD at too low a pressure, the mixture went very lean (only at high loads) and the engine detted. I am of the opinion that MAP value is also used somewhere in the load calculations.

Bob Rawle

Paul, I am not saying it does absolutely but the evidence and my datalogs certainly suggest it, I have masses of data fom my own car, the maf is not being maxed and still has head room, even at lowish TPS valuse I still hit the limit, the only difference is the boost I am running. Reduce the boost and I am still seeing similar maf voltages but engine load drops.

Why do you think its not having an effect, in limp home the ecu runs from the map sensor not the maf, unplug and check it out to see.

A larger maf will allow lower output voltages which will reduce engine load values but since the compensation's are not accessable that would be a dangerous thing to do running as I do.

Its going to be a question of detailed analysis of single change iterations to find out.

The jecs has been estimated to allow around 385 or so bhp using std sensor system, my findings would suggest that's about right imho.