1996 Impreza EJ15 ECU "Z1"

[seport]

This is called professional reverse engineering work, thank you.

I will try again the O2 addresses this evening and see what comes out.

Alexander

[seport]

Does the pending parameters live in the same area? i.e. between FB80 and FF7F?

[b3lha]

You're welcome. I wish it was possible for me to do this professionally.

Yes. All the parameters will be in the 1K RAM between FB80 and and FF7F. There is no other RAM where they can be stored.

Do you know if you car has a purge solenoid? It seems to be disabled in the ROM, so maybe it is does not apply to your car?

Func44B6-Test-Purge-Solenoid
44B6  1573C2F0    BTST.B #0,@H'73C2:16
44BA  267D        BNE H'4539
...
4539  15FB86D7    BCLR.B #7,@H'FB86:16    ; Errorflags
453D  19          RTS

000073C0   01 F4 69 FF 73 3F 17 00 D8 00 03 7D 40 FF FF FF   ..i.s?.....}@...

0x69 = 01101001

Bit 0 of 73C2 is fixed as 1 in ROM, so the Purge Solenoid error can never be set.

If this is the case then there is no point in looking for the Purge Solenoid Duty Cycle.

[seport]

I believe it has a purge solenoid valve, I check the diagnostics manual this evening.

[seport]

You are right about the purge solenoid valve, although I have a purge canister it doesn't seem to have any electrical solenoids with it's hoses.

I made all 3 O2 addresses as your latest instructions and the formulae for 3 of them the same (X*5000/512) and now they make more sense.
If you have evoscan software i can send you a log file and run it on your computer. You will not be impressed with the performance since it is a very slow car, however still very good after 12 years.

Alexander

[b3lha]

Good. Now only 4 parameters remain, I think.

It will be interesting to see your log file. I have not seen the Impreza CS here in Britain, but my wife is from Kenya and it is quite popular there because it is strong enough for the bad roads.

I may be busy tomorrow but I will continue on Monday.

Phil.

[seport]

any one know how to convert MAF sensor voltage output to mass air flow (grams/sec)? I need to calculate real time fuel consumption by using the mass air flow (grams/sec) and vehicle speed.

[b3lha]

The ECU will have a map to convert MAF sensor voltage to Mass Airflow. Just like it does for Temp sensor voltage to Temperature. I'll have a look for it on Monday.

[b3lha]

The ECU has a map at address 7060 to convert the MAF sensor voltage to Mass Airflow. The map consists of 65 sixteen bit values.

00007060   00 00 00 6D 00 97 00 C8 01 00 01 3F 01 87 01 D8   ...m.......?....
00007070   02 33 02 98 03 09 03 86 04 11 04 9A 05 3F 05 F3   .3...........?..
00007080   06 B6 07 91 08 7C 09 7B 0A 8C 0B B2 0C EE 0E 46   .....|.{.......F
00007090   0F AF 11 60 13 26 14 EB 16 CE 18 F2 1B 35 1D 6B   ...`.&.......5.k
000070A0   1F 82 22 06 24 5A 27 02 29 C0 2C FB 30 62 33 E1   ..".$Z'.).,.0b3.
000070B0   37 8B 3B 66 3F 7B 43 BB 48 1F 4D 0A 51 E1 56 F2   7.;f?{C.H.M.Q.V.
000070C0   5C 3C 61 C3 67 86 6D 15 73 42 79 AC 80 51 87 31   \<a.g.m.sBy..Q.1
000070D0   8E 46 95 9F 9D 26 A4 ED AC E3 B5 0C BD 65 C5 EC   .F...&.......e..
000070E0   CE 9D FF FF FF FF FF FF FF FF FF FF FF FF FF FF   ................

See attached graph.

The airflow is calculated as a 16-bit value and stored at FC10 and FC11. This value is proportional to the Mass Airflow. To convert it to grams per sec, you would need to multiply it by a constant like this:

g=a*k
g is grams/sec
a is the sixteen bit airflow reading from FC10
k is m/52893
m is the maximum airflow in g/s (ie. for which the MAF reads 5 volts)

If 8 bit precision is sufficient, you could use a = the byte from FC10 and k=m/206.

How do you calculate fuel consumption from Mass Airflow and Vehicle Speed? I'd be interested to know if this works.

[seport]

Thanks Phil,

I will send you a document I found via e-mail, since the attachment limit is too small.

With evoscan sw, if I request the data at FC10, and use the following equation (FC10 data X 50000)/206, will this be the grams/second?

[b3lha]

No. You have to know the maximum design specification of your MAF sensor.

For example, if your MAF sensor is designed to read 120g/s maximum then you would calculate (FC10 data x 120)/206.

[seport]

so then i did not understood the chart, what is the unit of maf in the chart?

[b3lha]

The ECU uses the chart to convert from voltage to airflow. It looks at the voltage on the X axis and finds the airflow on the Y axis.

But the value obtained is not in g/s. It is a proportion of the maximum airflow, like a percentage. That is why you need to know the maximum airflow in g/s in order to convert this reading to g/s.

[seport]

Now I understand So I have to find out the max grams/sec of the MAF sensor.

I found this:- "the ECU reads roughly 16 * (V − 0.5)2 g/sec" but this is for a Hitachi MAF sensor used on Audi. I found it here: http://s4wiki.com/wiki/MAF

What do you think Phil? Does it apply for Subaru or may be dependent on the model of the MAF sensor?

 ::)I think I went out of subject!

[b3lha]

I think it is dependant on the model of MAF sensor.

I suppose you could guess a value and then log the data over a long journey and compare the calculated consumption to the actual fuel used. Then adjust your guessed value accordingly. But it is not so easy to do in reality.

When I read the document you sent me, I realised that they assume the AFR is always 14.7:1. However, your ECU adjusts the AFR between 14.0:1 and 19.0:1 depending on RPM and Engine Load. (See the fuel map posted previously). So the calculated mpg will probably be less than your actual mpg.

Phil.