Zoldman Posted November 1, 2003 Share Posted November 1, 2003 I've been searching and reading on LT1 and OBD I and II, and I think I'm more confused than when I started. I have found a decent LT1 from a 97 F body, but it is OBD II. OK, I can live with OBD II; there are ways around some of the limitations. My question is related to the cats, which I will not have. How will the OBD II computer deal with the readings it gets from the non cat exhaust? Aren't there post cat sensors in OBD II cars? How tough is the OBD II to OBD I conversion, or is there an available OBD II programmer that can eliminate these issues? Help me!!!!! Bill '73 240 wanting new heart Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 1, 2003 Share Posted November 1, 2003 Bill, You can get O2 sensor simulators that plug into the harness to fool the PCM into thinking that the O2 sensors are there. See here: http://store.summitracing.com/partdetail.asp?part=CEI%2D104033 Tim Quote Link to comment Share on other sites More sharing options...
Zoldman Posted November 1, 2003 Author Share Posted November 1, 2003 Tim, Your name popped up a lot on my searches, so I thought you would know the answer. This is the first "computer engine" I have really worked with; I've been a neanderthal "carb" guy for the most part. All them leeetle wires and stuff. I hope you don't mind if I pick your brain once I get to actually trying to get it to run. I'm out in Riverside, so I'm in your neck of the woods, sort of. Thanks a lot Bill Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 1, 2003 Share Posted November 1, 2003 Bill, See here. Your are welcome to come. http://www.hybridz.org/phpBB2/viewtopic.php?t=25899 Tim Quote Link to comment Share on other sites More sharing options...
Zoldman Posted November 1, 2003 Author Share Posted November 1, 2003 Tim, God, I'd love to come, but I've already promised my younger boy (11) he and I would do a movie and video game day tommorow. We don't get to spend time together "just us" very much, so I don't want to disapoint him (or me!). I've talked to Matt (Skinhead) on the phone, and plan on going "Pickaparting" with him some Saturday, so this would have been a great chance to meet him in person too. Well, Im sure there will be another time, and I appreciate the offer. Again, I really thank you for your reply, and look forward to meeting you sometime soon. Bill Quote Link to comment Share on other sites More sharing options...
80LS1T Posted November 1, 2003 Share Posted November 1, 2003 Well like Tim said all you have to do is get O2 simulators. The rear O2 sensors dont have any effect on engine performance. They are only there to turn on the check engine light if one of the cats is not functioning properly. So just get the O2 sims and run with out cats! The O2 sims will tell the computer that the cat. converters(the ones you dont have) are functioning properly and that everything is all good. (I thought I would explain what the O2's at the rear are for and what the O2 sims do, just incase anyone was wondering! ) Guy Quote Link to comment Share on other sites More sharing options...
Zoldman Posted November 1, 2003 Author Share Posted November 1, 2003 Guy, I'm glad you answered that, because I meant to ask what the @#% they were for anyway. What other computer related mods, if any, did you make? Is there is good write up here or elsewhere that I have missed in my searching? Thanks Bill Quote Link to comment Share on other sites More sharing options...
80LS1T Posted November 2, 2003 Share Posted November 2, 2003 Well I have an OBD1 style LT1. Mine is a 93'. If you go with an LT1 the best years are 94-95' because they are OBD1 and you can tune them yourself with TunerCat software or LT1Edit software. The 93' still uses the chips where are you can "re-burn" the chips in the computer on teh 94-97' the 96-97' are OBD2 and the software actually costs more from what I understand(I havent really looked into it because mine is not programable) I will be updating some time to the 94-95' computer. As far as computer mods...if you get the software there are lots of things you can do to tune your engine and if you go with the 4L60E tranny(newer 700R4 electronically controlled tranny) you can program shift points and other things for the tranny. For wiring harness, I know Tim wired up his harness from the factory harness. I went the easy/more expensive way and bought a "painless" harness(plug and play basically). I know that there have been a lot of posts on the wiring for the harness so if your going that route then do a search for "LT1 harness wiring" or something like that and you should find what you are looking for. Hope that helps! Guy Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 3, 2003 Share Posted November 3, 2003 Bill, I would try to get an OBDI harness. It will make tuning much easier. THe wiring of the LT1 PSm is actually quite simple (although it dies look daunting!) You actually only end up having to connect these wires: 4 injector power wires (12V ignition +) 1 PCM pwer wire (12V constant +) Fan Control (the PCM earths the relay) Fuel pump control Everything else just plugs from the PCM to the engine sensors via the OEM LT1 harness. Then the gauge input wires: 1. Oil Pressure (I used a mechanical gauge) 2. Water Temp 3. Oil Temp (I used the oil level sender hole in the oil pan. This was just a nice extra gauge and is unecessary) 4. Volt meter. 5. Tach. 6. Speedo. I used all Aftermarket gauges (Autometer Ultralites). I actually have NONE of the original electronics in the car. I am using the Honda S2000 ingnition switch, toggle switches for lights etc, no heater, defroster, or windshield wipers. I think the only original Datsun part remaining are the tail lights. Let me know if you need any help when you get to the wiring. Tim Tim Quote Link to comment Share on other sites More sharing options...
Oltmann Posted November 3, 2003 Share Posted November 3, 2003 I would try to get an OBDI harness. You don't have to swap harnesses to switch from OBDII to OBDI. The harness for OBDII is the same pin for pin as the OBDI harness, with the addition 4 wires for the rear O2 sensors. All the sensors are the same, with the exception of the knock sensor which produces a higher value. This can be rectified by either swapping to the older sensor, or wiring a 2K resistor between pin 22 on the blue connector and ground. All you really need is an OBDI PCM. You can find OBDII programming software now, but it is more expensive (probably by more than it will cost to swap to OBDI) and the monitoring/logging software doesn't work as well. Because of this, I would advise you to swap to OBDI Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 3, 2003 Share Posted November 3, 2003 Thanks for the correction Spencer!! Yes, just the PCM and ALDL connector (which any OBDI GM car can provide). I got my OBDI ALDL connector from a Cavalier. Tim Quote Link to comment Share on other sites More sharing options...
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