fl327 Posted August 22, 2003 Share Posted August 22, 2003 Goofing around and testing pile of spare parts, testing my afms, ecus, and what not. Decided to swap out my 83zxt five speed ecu for my old 81zxt ecu, right? Started right up, happy me. I remember the post about fuel cut in a zxt, so me being me I had to go try it out. BTW, I havent reved my car past 6k with 83zxt setup I am running now. Warm the car up, decided to leave my timing ay 24BTDC. I took it for a spin on the freeway, and dropped it back into second on the on ramp and the sucker just shot to 7100, without blinking, without the infamous fuel and ignition cutoff. I made power that fell off greatly after 6300rpm, but the sucker did spin fast up there, and yes, this is with the t3. Needless to say, I left that ecu in there for the time being. My fuel pump is wired to a relay independently of the efi system, and I have never used or wired up the fuel pump modulator or the stock relay for it, I deleted that one as fast as I could get a relay. Im wondering if this is the reason why it would not initiate a fuel cut???? I have heard it is like hitting a brick wall, and before I had a tach I thought that I was hitting a rev limiter of some sort. Once I installed one, I learned it wasnt a fuel cut, it was bad connector on ecu causing it to stutter at 4k or so. I have also heard that ignition and fuel both cut off for split seconds when a rev limit is hit. Im thinking that it is the fuel being cut off intermittantly? I spun it a few times to 6500, but feeling really flat it started feeling I got back to reality and drove home normally, but I did not hit a rev limiter. Just something I found out today, wondering if its just an 81zxt ecu. Tommorow we will try to do 6500+ once or twice with 83 ecu. When are you guys out there experiencing a rev limiter? Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 22, 2003 Author Share Posted August 22, 2003 VERIFIED 83 ecu cut me off the rev party at 6600 consistently 81zxt ecu I have HAS NO REV LIMITER. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted August 22, 2003 Share Posted August 22, 2003 When I had a stock one, I hit the limiter about 6400, although when I changed the cap and rotor, sometimes it would rev beyond that without issue. All I can say is, it may rear its ugly head when you least expect it, so make sure your head doesn't bang the windsheild. I had mine moved to 7k when JWT set up my ecu. Quote Link to comment Share on other sites More sharing options...
Guest zpeedracer25 Posted August 22, 2003 Share Posted August 22, 2003 it was bad connector on ecu causing it to stutter at 4k or so. Do you happen to know which connector or wire was causing this condition? I've been chasing the same problem for quite a while on my 1977 280Z with 1982 L28ET. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 22, 2003 Author Share Posted August 22, 2003 I contribute my intermittant ecu problems to a faulty connector-the middle connector ( It had a lot of "wiggle"), and these connections got dirty alot, I blame that on the floor being dusty as heck. I vaccummed the floor and use dielectric grease on ecu connectors. I soldered in a tighter molex connector and mounted the ecu rigidly to the driver kick panel, and it was good to go. What would happen to me is that when the car would hit that stutter point, I would reset the ecu and it would go away, then it would come back again a few days later, do it again go away, until I wiggle the middle plug. Then all I would do is wiggle that plug, and it would go away again.... I forget what the middle connector goes to, but im sure any of them would cause a similar issue. I could check the FSM for you if you dont have one. Loose and dirty connections and bad ground have been the most reoccuring issues with this car-and almost everytime this happens-I hit the "brick wall" at 4500 and sometimes right when I floor the car. I installed a grounding kit I got off a silvia clip to cure ground issues, and resoldered in quick release connectors with plenty dielectric grease to all connectors. If I had the turbo, fuel, and be able to adjust my ignition curve, I would be good to go 6500 at least, as is if I let it hit 7k it will shoot up there pretty good, but power will be down-hot charge. I put the chip back in my limiter for 6k, system is still only feeling good up to 5500, but I go to 6k to keep Rpm up when I hit the gear. With the auto ecu it charges hard to 7k with a little stutter above 6400 or so, not a limiter or connector thing, IM out of air! with the 83 ecu it will initiate a fuel or ignition cut at 6600, I only tried this twice. Here is a weird one, downright boggling. When I drive without the tps connected in my 75, it doesnt almost nothing, its meaningless. When I do it in the zxt-it will barely move? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 22, 2003 Share Posted August 22, 2003 fl327, you are interchanging an 81zxt and 83zxt ecu on the same car? I've always thought 81's used dropping resistors and this and that and basically they weren't interchangable. However, this question is very interesting to me. I am builing an 82zxt motor for my 81n/a and am having a bear of a time finding and 82/82 zxt ecu, whereas 81zxt ecu's seem to be more plentiful.. so, yeah. I guess that's why I'm asking. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 22, 2003 Author Share Posted August 22, 2003 the 81zxt ecu is fine, I have interchanged ecus a number of times, ive actually run all 81-83 year ecus with no issues on 81 harness, and I keep a few spares that I have to keep. Ive run the 81 ecu with a 83 distributor, and it was a drop in swap. 83 is preferred to me though, since it runs 24btdc instead of the other ones which like 20btdc, which is another enigma------------ Im running 24 btdc on the 81 ecu, and its identical.... I dont know whats up with the resistors either. I have the 81 harness with resistors, and used an 83 ecu for the longest time, and beat on it pretty good with it as well-------- it just doesnt make any sense to me at all. Maybe the later ones can sense the resistors or something in line, maybe it could be something Nissan designed in case of ecu replacement, and stopped 81 turbo ecu production after that year????? It kicks more @55 than a donkey either way, and either setup has been very good to me. Heres some more weirdness, ive used tps from four or five different datsun/nissan cars from the 81-89 period, and they all work great? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 23, 2003 Share Posted August 23, 2003 83 is preferred to me though' date=' since it runs 24btdc instead of the other ones which like 20btdc, which is another enigma------------Im running 24 btdc on the 81 ecu, and its identical....[/quote'] No mystery. It's just the initial advance the engine uses at idle. The ECU will use identical advance curves once off idle, the 83 will retard 4 degrees more. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 24, 2003 Share Posted August 24, 2003 so... either way i should be safe if a get an 81zxt harness along with the ecu? That way the dropping resistors would be in place (whether or not they are needed/etc is another question). The injectors themselves are the same from 81-83, right? So, fl327, the only combo you haven't done is an 81zxt ecu with a 82-83 harness (??). Everything else seems to work. That is good to know. Quote Link to comment Share on other sites More sharing options...
zhins50 Posted August 24, 2003 Share Posted August 24, 2003 FL327 put my buddies car together, it runs 83 harness with 81 ecu, its nice. Of course, his car still runs me into the ground, I will get you Quote Link to comment Share on other sites More sharing options...
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