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Discussion Starter · #1 ·
One of my friends has a 240SX SR20DET swap and he has a nice little datalogging setup using a stock plug on the car. I've been browsing over at pgmfi for a little while to learn about how to do this, but it seems most things are for OBD1. They say it works, but a lot of the write ups are still unclear. Has anyone here done the Nokia USB cable thing for an OBD0 ECU? Looks like a pretty easy mod, just soldering a couple of wires.
 

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Don't panic guys, i'm just super busy these times.

Ok. to enable dataloging on obd0 you need a chip that has datalogging enabled. So you need to chip your ECU.

If you go on PGMFI, and search a lot, you will find a rom called NG60. This rom is an almost complete rewrite of the stock chip and has dataloging enabled. Downside of this is that you need to make your maps (fuel and IGN) because the chip is not calibrated exactly the same. Searching on PGMFI you will find a link to Xenocron's web site that contains stock maps for the NG60 rom.

Once you have this working, you not only have dataloging, but also a full adjustable OBD0 ECU. Not as complete as OBD1 can do, but still kinda cool. You can support BOOST and thing like that.

BUT, for the same amout of work, you can convert to OBD1 (all you need is an OBD1/OBD2 distributor, conversion harness for ECU and distributor). With that in place, you can buy a P28 (for VTEC cars) or a P06 (for non vtec) and use one of the best free programs to edit your rom, CROME. Then you can use EcuControl to datalog, or pay 150$ to enable datalging mode in Crome to the maker of the program. Rom Eidting on OBD1 works very well and results are a lot more smoother than OBD0. You have more cool options on OBD1 than OBD0.

Last thing, when you want to plug your laptop to the ECU, you need a device to do that. Inside the ECU there is a CN2 marked connector... Well, the slders point are there and you need to solder in the said connector. Once you put the 4 pin connector, you need a cable to hookup all this. You can either use a device that we call a Max233 that will translate Serial Communication from the computer to TTL signal on the 4 pin connector inside the ECU. OR you can go USB and find a device that will translate from USB signal to TTL.

http://www.moates.net/product_info.php?cPath=49&products_id=79
http://www.moates.net/product_info.php?cPath=49&products_id=78

You can also use a Nokia Cable, the DKU-5 one that is the equivaqlent of that Hulog for cheaper, but you may have trouble finding the pinout of the cable.

http://www.synoptic-tuning.com/ecucontrol/nokiadatcable.htm

http://www.synoptic-tuning.com/ecucontrol/how_to_mod_my_ecu.htm

Good luck ;)
 

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Many OBD-1 engine/ECUs use a heated oxygen sensor, but the heater stuff can be disabled IIRC. OBD-1 only uses one O2 sensor. I think OBD-2 uses the second one to judge if the catalyst is functioning properly.
As for the distributor, you might need to find a '92-95 ZC distributor and CYL (or whatever the one on the other cam is) sensor.
 

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Discussion Starter · #10 ·
So, would it be better to just convert to OBD1 and start off with a chipped OBD1 ECU? What would that require, I would imagine a conversion harness for the ECU, a new dizzy, a 4-wire O2 sensor, and of course a P28?
 

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downest said:
So, would it be better to just convert to OBD1 and start off with a chipped OBD1 ECU? What would that require, I would imagine a conversion harness for the ECU, a new dizzy, a 4-wire O2 sensor, and of course a P28?
no need for a 4 wire. I didnt say you had to replace it.
 

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downest said:
[...] and of course a P28
Since you're going to chip it anyway, if you're having a hard time finding a P28, you can buy a P05 auto and move the hardware that normally controls the lockup solenoids over to the positions that handle VTEC. Move around a few program jumpers to enable VTEC and 5-speed behavior, load a P28 program and you're set.
OBD-1 ECUs are so flexible. :)
 

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Discussion Starter · #18 ·
I'm doing another junkyard trip this week, and I'm seriously considering getting that P28 and starting on an OBD1 conversion.
I was reading up on the swap, I found this on pgmfi.org. It says to keep the same injectors and resistors, so I'm confused on that. Also about the injectors, my friend is going to boost his Z6 soon, and he offered me the stock injectors, is there any benefit to getting those, I'm pretty sure they will be free since I'm helping with a lot of work on the car.
I'm guessing I will be needing an OBD1 dizzy as well. How much should I pay for one at the junkyard, and which cars can I pull it from? Does it have to come from an EX/Si? Can I use my stock OBD0 dizzy with a conversion harness?
I think I want to wire my own conversion harness, there are a lot of diagrams out there for it. Ideally, I'd like to somhow make it so I can plug in my current harness to one end, and plug the other end into the P28. The only problem with this is, I don't know where I would get the plugs for the harness side. Could I pull the plugs out of another OBD0 ECU and use those? When I get the P28, I think I'm going to cut the harness a few inches up so I can use those wires, that's what the junkyard usually does when they pull parts for me anyway.
The last thing is the O2 sensor. A lot of guides for the conversion include it, what are the advantages/disadvantages of the 4-wire? I don't mind getting one, and I heard someone talking about the O2 sensor in a VX civic being something special, what is that? I'm pretty sure there's a VX at the yard, I remember seeing the mini-HX wheels.
 

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The civic hx uses a wideband o2 sensor stock, not a narrow band like on most other cars. Which means it can actually read levels of stoich and not it's below stoich or above stoich, with no true value to the reading. Widebands cost a lot more than narrowbands.

The 4 wire o2 sensor just has a built in heater, the o2 sensor does not work until it reaches a specific temperature, in obd0 cars the exhaust gas has to heat up the sensor until it can get into the operating temperature range and then work. So on obd1/2 they use a heater when you first turn the car on to get the sensor to start working much quicker. It's probably marginally better for your cat since it will only be running a little rich for a short period of time when you first start it.

You can make your own conversion harness, but it may be easier to buy one, depending on what parts you can get a hold of where you live. I think xenocron.com still sells those harnesses.

Don't you have to do something to the ecu about the knock sensor if your engine doesn't have one or can you just leave it off?
 

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downest said:
It says to keep the same injectors and resistors, so I'm confused on that.
It's an issue of resistance through each injector circuit. Resistance is a measure of how much a given circuit or component impedes the flow of electrical current (amperage). The higher the resistance, the less current can get through.
OBD-0 injectors are peak-hold type injectors. They're designed to be snapped open by a quick surge of current, then held there by a smaller amount. As such, they have a less powerful coil (the electromagnet that opens the injector valve) and a lower resistance which allows for that initial surge of power.
OBD-1 injectors are saturated type injectors. They're designed to be opened and held open by a constant level of electrical current. As such, they have a more powerful coil and higher resistance.
Honda ECUs are all designed to drive saturated type injectors. That is, the ECU only switches power on or off, there's no control over the current flow.
If you simply plugged an OBD-0 peak-hold injector into an OBD-1 setup, it's lower resistance would allow much more electrical current to flow through the ECU than it's designed for. Enough so to damage the ECU's injector drivers or overheat the injector coils. OBD-0 setups get around this problem by putting an additional resistor in the circuit of each injector which limits current flow, protecting the ECU.
If you put an OBD-1 saturated injector into an OBD-0 setup, the injector's higher resistance would already be limiting it's current flow to a safe level, but the OBD-0 resistor box would take the limiting a step further, causing the injector to open sluggishly or not at all.
The solution here is fairly simple: If you're using OBD-0 injectors, use the resistor box along with them. If you're using OBD-1 injectors, install jumpers where the resistor box would be. OBD-1 engine harnesses already have a jumper in place - if you look at the driver's shock tower connectors, you'll see one with a plug in it. That plug is just a bunch of jumpers which distribute power to the injectors and other 12v components on the engine.


downest said:
I'm guessing I will be needing an OBD1 dizzy as well. [...] Does it have to come from an EX/Si? Can I use my stock OBD0 dizzy with a conversion harness?
I think the VX uses the same distributor as the EX/Si if you're really after one. I've run my 'Z6 on a P06 ECU (normally coupled with the D15B7) before without issues. That says to me that all the OBD-1 Civic distributors use the same sensor pulse patterns, making them electricly compatable.
As for OBD-0 distributors, the sensor pulse patterns are different from OBD-1... The ECU won't be able to run the engine properly.

downest said:
I heard someone talking about the O2 sensor in a VX civic being something special, what is that?
The VX also uses a wideband as akirarex was saying. You need a special controller to make use of the wideband sensor - it won't work if you just hook it up to a P28. The VX ECU will obviously run it, but that ECU is a completely different animal than the P28. I don't think anyone has disassembled the VX code (though it has been a while since i looked at pgmfi.org) and tried to do anything with it, so it's basicly unchippable.
 
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