Z31 Reprogramming - question for Bernard

[Sean73]

I'm just getting started into burning my own ECUs. At this point I am in the information gathering phase and I've been reviewing the stock Z31 and Z32 maps.

 

I have a 240Z Turbo powered by a stock Z31 harness, ECU, and MAF. At some point I would like to install larger injectors and MAF for more power. Through my research I have found that tweaking the ECU maps for bigger injectors and/or MAF is not just a simple matter of modifying the "K value", and running with it.

 

Bernard, have you tried copying over the Z32TT maps to the Z31T maps? I realize the two maps are structurally a little different, but wouldn't it be possible to copy the relavant fuel, timing and VQ values from the Z32TT maps to the Z31 maps, since the bins are the same size? I would retain the stock Z31 maps for cold start, and anything else specific to the Z31 sensors.

 

Then, install injectors equivalent to the Z32TT, and the Z32 MAF to my existing Z31 EFI. I figure this would be easier than custom-tailoring a Z31 map. Just use a stock Z32TT configuration that's known to work reliably to about 350 HP.

 

 

Any input appreciated.

[Bernardd]

I started with a stock fuel/timing maps, then altered for best results. I have not tried any maps from the z32 ecu other than when I switched to the z32 maf I used the tp values from the z32, then altered them. You can copy the maps over and they might work well for you, give them a go and post back.

Bernard

[Sean73]

Did you have to physically alter the Z31 ECU so that it doesn't croak when it sees the <2V input from the Z32 MAF?

[Bernardd]

Yes, I removed three resistors that control voltage to an opamp. I don't have the board #'s for them handy at the moment. You will need to use an ecu with a # of the jwt 450hp control system list. They are easily configured to use a different maf. The older ecu's have the components to control the min voltage from the maf on a small board. I never messed with that ecu's maf settings at all, althought it is easily programmed as well.

[Sean73]

Bernard,

 

I am making progress on my ECU. I bought a willem programmer off Ebay, and started burning some 29C256 chips with the stock 88SS program. A friend is altering my 88NA ECU with a ZIF socket. I'll be able to test the stock program in the next couple of days.

 

Anyway, I am still interested in the mods you did to install the Z32 MAF. If you have any additional info, such as where on the board these resistors are, I would be very grateful.

[Bernardd]

http://album.hybridz.org/data/500/8360MafMod.JPG

http://album.hybridz.org/data/500/8360MafMod2-med.JPG

The small resistor is #'d R201.

You can install different resistors where the large green ones are to change your limp mode voltage.

[Sean73]

Thank you! Did you just jumper the resistors with some wire?

[Bernardd]

I just removed the resistors and that's it.

[Sean73]

Thanks.

 

I am trying out my 88 ECU with a stock chip and running into a couple of issues:

 

1) it barely holds an idle when cold, but idles perfect once the engine is warm. (I warmed up the car with the 84 ECU). Perhaps it does not like the CHTS input but I need to do more troubleshooting.

 

2) It won't go into closed loop mode

 

I suspect the ECU doesn't like the 1984 ECCS wiring, even though the only difference are the air regulator and the fuel temperature sensor. These aren't mentioned in the JWT literature, so I figure they are not major enough to send the ECU into a limp mode - what do you think?

 

3) Tried burning a AT29C256 with the 88SS.bin code from the Z31.com website. The car would not even start. I figure it's something in the configuration of the willem programmer that I am using. One thought: should I write the 128 bytes of code to the first half of the chip, or the second half?

[Bernardd]

Thanks.

 

I am trying out my 88 ECU with a stock chip and running into a couple of issues:

 

1) it barely holds an idle when cold' date=' but idles perfect once the engine is warm. (I warmed up the car with the 84 ECU). Perhaps it does not like the CHTS input but I need to do more troubleshooting.

 

2) It won't go into closed loop mode

 

I suspect the ECU doesn't like the 1984 ECCS wiring, even though the only difference are the air regulator and the fuel temperature sensor. These aren't mentioned in the JWT literature, so I figure they are not major enough to send the ECU into a limp mode - what do you think?

 

3) Tried burning a AT29C256 with the 88SS.bin code from the Z31.com website. The car would not even start. I figure it's something in the configuration of the willem programmer that I am using. One thought: should I write the 128 bytes of code to the first half of the chip, or the second half?[/quote']

 

 

1. Is it rich or lean? Squeeze fuel return line or fuel line to determine which if you don't have a wideband yet.

 

Tables to edit are:

7E00 - Start Enrich

7E10 - Start Enrich

7EB0 - Coolant Temp Enrich

7F30 - Coolant Temp Enrich

 

2. Change the value at address 7F91 from 3C to FF. This is the coolant temp that closed loop starts at. FF disables closed loop corrections. You want this to be disabled to prevent the ecu from making corrections when your trying to tune.

 

3. Second Half.

 

Bernardd

[Sean73]

Hi Bernard,

 

The ECU update is going well. I took your advice and burned the 88SS code to the second half of the AT29C256 chip. It works great now. The cold start problem went away - it must of had something to do with the original 88FedAuto chip.

 

I've noticed the idle is much smoother with the 88 ECU, and it did eventually go into closed loop without making changes to the code. So, it's all fun stuff from here.

 

I picked up a Z32 MAF locally for $25! So I would like to install it. However, I am a little nervous about removing the small resistor off the board, since my soldering skills aren't good (a guy at my work helped me with the ZIF socket, and I don't want to take advantage of him). Once I locate a 2nd spare ECU and Z32 MAF, I think I'll start with the Z32 MAF conversion (I always like to have a spare on hand).

 

As for injectors, I'm torn between high impedance O-ring style injectors, or low-impedance barb style Mercedes injectors. Both have their pros and cons.

 

Meanwhile, I'd like to do some experiments with the stock code. Here's some ideas I have - feel free to critique (I am still just an amateur).

 

1) Adjust TP values for the 8% displacement difference between the L28 and VG30. This probably wouldn't do much, but my thinking is that the VG30 TP values might be a tad too rich especially at low RPM.

 

2) It appears to me that the VG30 map doesn't go past 7 psi of boost. I found this by back-calculating from the theoretical air/fuel ratios. Even with the stock injectors, I wonder if it's worthwile to expand the maps to higher TP values, and get more accurate delivery at 7-10 psi.

 

Thanks for all your help. I can't believe more people don't do this. For a $50 eprom progammer, $50 ECU, $6 chips, and freeware software, I've converted my Z31 ECCS into a very tunable system. With the money I saved I can go out and get a wideband.

 

Sean

[Sean73]

Thanks again for the info.

 

To remove that resistor' date=' take a pair of small needlenose pliers and grip the resistor and apply the solder gun in short intervals until the resistor comes off. It should only take a dab or two and it'll come off.

I'd change the kvalue first. That will clean up the fuel a little, then if necessary change the tp scaling. I'd do a bunch of rich column tests first to determine where you're accessing the maps at given maf voltages. Once you've determined the maf voltage and rpm and fuel column you can start to build a table with maf voltages in place of the fuel values. This will make tuning in the future a thousand times easier. Because you're change to a z32 maf soon I wouldn't get to carried away with this yet but at the same time it's a good way to become familiar with what's needed to tune teh ecu.[/quote']

[Guest NickL]

Bernardd,

 

I am also very interested in re-programming my ECU. I have a JWT 450HP setup. Would you be willing to help me?

[Bernardd]

Depends on what you want to do. Do you have the equipment to burn proms?

[Guest NickL]

Yes, I have an eprom burner. It is the mapping information for the Z31 ECU that seems to be impossible to find.

[Bernardd]

I've uploaded (downloads forum) a file for romeditor and one for live edit. Make sure the binfile is 32k in size. What are you trying to tune?

[Guest NickL]

I downloaded the Romeditor file. I did not see a file in the posting for the Live Edit file. I am tuning an L28ET with N42 head, 450HP JWT kit, T4 turbo. I have tried to use the Romeditor software before. The layout of the data in the fuel tables does not make much sense to me. Upper left quadrant of table has very large values (192). One column later it transitions to a very low value (18).

[Sean73]

Read the article on ECU tuning at ZtechZ.net. It's for the VG30DETT, but most of the same principles apply.

 

This is a good place to start in learning how to burn your own chips.

[Bernardd]

This is the formula for fuel map:

if Data > 128 then

Multiplier = (DATA - 64 / 128 )

else

Multiplier = (DATA + 128/128 )

 

 

The value of 192 you're seeing is one. Whatever the ecu has calculated for that load point and rpm, the ecu multiplies it by the forumula above to get it's actual pw. In romeditor some of the values are blue. They are the learn area of the map, as well as the feedback area. Meaning the ecu is allowed to correct fueling based on o2 readings. Enter the #'s in the formula and you'll see what I mean. This is how I first tuned my ecu for larger injectors. I didn't know about the k value so I adjusted each point in the fuel map by a multiplier. Worked very well.

[Guest NickL]

I have read a number of articles on tuning the Z32. The problem is that very little is available for the Z31.

 

Bernardd,

 

The VG30 adr zip file will not unzip - it comes up with an error. I have downloaded it 2 times with the same result. I am using WinZip.