yo2001 Posted December 17, 2003 Share Posted December 17, 2003 Well, I drove my 280Z 200miles today and I think I discover something about the Z31 ECU. First thing is cold start cycle. It turns on automatically when you first crank the car. The cold start suppose to close after car is moving via speedo sensor. Which I don't have, so it causes th ecaar to run rich for like 3.5 minutes after warmed up start up. I also found that 1 point in A/F ratio is roughly 100deg F. Just posting my discovery. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted December 17, 2003 Share Posted December 17, 2003 Hey I was just going to post an ecu discovery myself! I might as well put it here.. My Z31 ecu (attached to my Z31 turbo engine in my 280)... I watch my o2 sensor voltage (apexI turbo timer/a/f ratio monitor) At exactly 3000rpm it goes from reading .9-1.1 volts to 4.55 volts (meter doesn't read past 5 volts) When it does this, I really start burning up the fuel... To get any decent fuel mileage, I MUST keep it under 3000rpm.... this is just cruising too.. it reads max voltage when i lay on the throttle and build boost as well. I know in the FSM it talks about swtiching from sequential to batch firing the injectors at 3000rpm i think... There are two other variables..the other with the car being up to operating temp.... I'm not sure what the rest says.. 3K in 5th is approx 120kph.. not nearly enough to keep up with traffic in the city... I'll have to put in a 3.54 diff again to be able to hang with the traffic and get good mileage. BTW I can get as much as 28mpg with the car...Not bad considering all my rolling resistance, and aero mods.. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted December 17, 2003 Share Posted December 17, 2003 Yo2001: I know the automatic Ecu's for the 300's had a circut that held the automatic tranny out of overdrive till a temp sensor in the tranny let it know that it was up to temp. Hmmm anyone else have z31 ecu knowledge they can share?.. drop it in this thread... Quote Link to comment Share on other sites More sharing options...
yo2001 Posted December 17, 2003 Author Share Posted December 17, 2003 that sounds like something is wrong there. Mine stays at .90-.93 on start up and .86 volt after warm up. I cruise at 3600rpm on the interstate. (3.90 diff ) Under WOT at .94 or so. That's measured with same Apexi Turbo timer that you got. However mine ever goes pass 1V. But I do only get about 20mpg on the interstate. But my )2 might be no good since it has seen about 10-15 gal of leaded fuel The batch will fire twice as fuel as sequential so I guess it'll use more fuel. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted December 17, 2003 Share Posted December 17, 2003 According to my FSM 1 volt (approx) is supposed to be just leaner than than stoich.. I recall it saying that at idle the z31 should be 15:1 or so... I'll have to look in my manual again, and get the exact #.... I do know that it runs very lean at idle....(factory set) I have lots of tuning ahead next season, so I imagine I'll have to bone up on my FSM this winter... Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted December 26, 2003 Share Posted December 26, 2003 Once you get over a certain airflow, the ecu goes to batch fire on all 6 injectors, hence the bad gas mileage. Stioch is .47 volts FWIW. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted December 27, 2003 Share Posted December 27, 2003 Well, I'll have a look through my Haynes manual for my truck. Its a 93 king cab, and has the 3.0L V6. As far as I can tell, its very close to the Z31 engine, and my auto trans has the same feature (no O/D till its warm). Maybe the 'trouble shooting' section will give some info.. Quote Link to comment Share on other sites More sharing options...
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