Z31 - Wild switch at 141*F(60*C)

[harwood909]

I'll upload the log. It's short and sweet and illustrates what I'm experiencing when the ecu reaches 141 degrees F (60 degrees C). Injection time shoots up and goes very rich. I don't understand what could cause such a drastic change.

87 turbo Automatic computer (trans has been swapped to a manual)
Stock MAF
550cc injectors
o2 sensing is off

[midian]

have you turned on "automatic transmission off" feedback switch?

[harwood909]

Yes I have.

[Matt]

Post the tune file please. I see the jump 1.87ms to 2.77ms so the ECU code is doing something temp enrich related but not sure what

[harwood909]

Here it is Matt. The log I posted was not taken while running this tune but this tune had the same issue at 141F.

[harwood909]

Post the tune file please. I see the jump 1.87ms to 2.77ms so the ECU code is doing something temp enrich related but not sure what

Any luck with this issue Matt?

[Matt]

Sorry I've got about 20 support cases to work through at the moment. This one required some intimate bench time with a Z31 ECU and your tune

Okay so 60 degC is the switchover point between batch injection and sequential injection

1.95ms both injectors are firing same time, after 60 degC it switches to 2.6ms and switching between one injector and the other

This is on the 21P11 base file, even stock tune does this and on the 21P01 image too. Standard ECU operation

If it is going to rich there may be a mismatch with the flow rate of your injectors (at a guess) causing this issue

[harwood909]

Sorry I've got about 20 support cases to work through at the moment. This one required some intimate bench time with a Z31 ECU and your tune

Okay so 60 degC is the switchover point between batch injection and sequential injection

1.95ms both injectors are firing same time, after 60 degC it switches to 2.6ms and switching between one injector and the other

This is on the 21P11 base file, even stock tune does this and on the 21P01 image too. Standard ECU operation

If it is going to rich there may be a mismatch with the flow rate of your injectors (at a guess) causing this issue

Ahhhhh this is making a little more sense now. There was a TSB for the fuel injection on z31. Part of the service was rewiring of the injectors so they are always batch fired. When I redid my harness I rewired them back to sequential. I did this because of the new injector connectors and to clean up the wiring.

I'm guessing the best thing to do would be to rewire the injectors so they will batch fire regardless of what the ecu is telling them to do. This is very confusing as to why they would program the ecu like this in the first place.

[Mercennarius]

Sorry I've got about 20 support cases to work through at the moment. This one required some intimate bench time with a Z31 ECU and your tune

Okay so 60 degC is the switchover point between batch injection and sequential injection

1.95ms both injectors are firing same time, after 60 degC it switches to 2.6ms and switching between one injector and the other

This is on the 21P11 base file, even stock tune does this and on the 21P01 image too. Standard ECU operation

If it is going to rich there may be a mismatch with the flow rate of your injectors (at a guess) causing this issue

Ahhhhh this is making a little more sense now. There was a TSB for the fuel injection on z31. Part of the service was rewiring of the injectors so they are always batch fired. When I redid my harness I rewired them back to sequential. I did this because of the new injector connectors and to clean up the wiring.

I'm guessing the best thing to do would be to rewire the injectors so they will batch fire regardless of what the ecu is telling them to do. This is very confusing as to why they would program the ecu like this in the first place.

Did you ever rewire your injectors back and if so did it resolve your problem? Thanks.

[Matt]

I've added parameters to the 1.2.55 version of Nistune yesterday

Attached is the Z31 address file (put in Documents\Nistune\Address folder) which contains the switch over temperature (60 degC) and a tickbox to enable disable

As for the switch over RPM/injection time this is a ratio which is hard coded into the ECU code

Code: Select all

9BDB : D6 54 			ldab	RAM_0054_temp_mult
9BDD : 81 06 			cmpa	#$06 <<<<<<<<<<<<<<<<<<< Switch to batch 
9BDF : 22 1E 			bhi	BRA_9BFF_Cranking
9BE1 : 25 04 			bcs	L9BE7
9BE3 : C1 97 			cmpb	#$97 <<<<<<<<<<<<<<<<<<< Switch to batch
9BE5 : 24 18 			bcc	BRA_9BFF_Cranking

9BE7 : D6 1F 			ldab	RAM_001F_Limit_Flag
9BE9 : C4 EF 			andb	#$EF
9BEB : D7 1F 			stab	RAM_001F_Limit_Flag
9BED : 96 76 			ldaa	RAM_0076_inj_MSB
9BEF : D6 77 			ldab	RAM_0077_inj_LSB
9BF1 : 20 1A 			bra	L9C0D

9BF3 : D6 54 			ldab	RAM_0054_temp_mult
9BF5 : 81 05 			cmpa	#$05 <<<<<<<<<<<<<<<<<<<< Switch to sequential 
9BF7 : 22 06 			bhi	BRA_9BFF_Cranking
9BF9 : 25 EC 			bcs	L9BE7
9BFB : C1 20 			cmpb	#$20 <<<<<<<<<<<<<<<<<<<< Switch to sequential
9BFD : 25 E8 			bcs	L9BE7

To add these parameters to the code will require another feature pack update

The 06/05 parameters on/off through testing move the RPM/injection time point (imagine a diagnonal line drawn through the fuel map).

We have found that resizing to large injectors (eg 1100CC as on my mates car) resulted in lower injection times and the switching point not happening until 6000rpm. Normally the stock ECU would switch over about 3000rpm

Adjusting from 06/05 to lower numbers like 04/03 seemed to help

The $97/$20 parameters also come into play here but I'm not sure how they are used at this stage but do affect the switching point

[harwood909]

I'm pulling the car out of storage today so I will tinker with it from a very... very cold start. I just updated Nistune as well to 1.2.57 and I see the check box and also the adjustment for the batch/sequential temp switch. So ready for summer after a solid 6 month long winter! Thank you

[Matt]

No probs. I had to help a friend out his similar issues so hopefully this helps you too