RB20DET computer worries-HELP!

[dwhe009]

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Hi everybody, im having a few problems with my stardard computer. First i will list what i have;

R32, RB20DET, silver top motor, manual transmission, 3" exhaust, 600*400*70mm intercooler, pod air filter, standard turbo. Regapped 0.8mm plugs

The motor is in a commodore. I brought the motor from the wreckers and i got a computer from a Nissan Laurel C33 with it. Everything works fine and the thing has been running like a dream for 3/4 of a year. I only just put the intercooler in and beause its sucking in much more air, due to it being denser, i have ran into a few problems. The car runs very inconsistly. Air/fuel ratios are the same, there is correct fuel pressure so the timing must be doing strange things. Sometimes it will feel very very quick, and other times it will lose about 20%. It wont be anywhere near pinging as its only sitting at 10psi.

Is the computer the same as for the gtst? Is there a difference between auto and manual computers? as my one is a auto computer and there is error 54 (auto signal to ecu) on the computers self diagnostics.

Thanks alot for any help.

[BenA31]

hmmm i was also getting that problem with my GTST. Mine was running a auto computer and had since had a manual conversion and was also getting that same error. although i've since had the computer remapped and haven't noticed any problems while driving. If i got some time i might go see if i'm still getting that error code, but i doubt it cos the whole ROM of the computer was cleared for the remap and from what i understand should be running like a manual computer now.

[dwhe009]

Did it fell quick then slow? each new time you started it up that is.

Its so bloody annoying. See yesterday the thing felt slow and just this morning it took off and started wheelspining in second at around 50 km. ha.

I was wondering if anyone knows how to look at the timing while the car is going. i.e. not timing light. I might beable to see a change from each day. I have tried looking at the difference between the crank angle and spark signals on a oscilliscope but cant cant get correct values of advance?

[BenA31]

NISDATA scan tool. Theres a dude on the forums selling them on the forums. I pretty sure it shows ya timing changes.

Mine got looked at when i took it to XTC workshop and they connected up their laptop to my diagnostic port just under the dash, there software showed all the realtime figues and numbers of everything inc timing.

[dwhe009]

cheers mate, but im a poor barstard. Student you see.

I have been reading so many forums of guys changing there base timing but i dont quite get how this works. I thought that once the standard computer is reset it advancing timing at all load/rev/temp etc points until knock is sensed by the detenatign sensor, then slightly retarded? this would mean that if you turned the crank angle sensor up 3-5 degrees you would get the same result as the computer just figures out the best values anyway?

anyone know anything about this? I must be wrong cause all you guys are getting better results by advancing the base timing ay?

cheers for any ideas.

[blind_elk]

By setting the base timing on the CAS, you are simply changing the point at which the CAS signals the ECU that it should start thinking about initiating a spark event. All the ECU knows is that it has a table of values that tell it to delay 'x' millisecs after it gets the trigger signal before firing the spark. If it gets the signal 3 crank deg earlier, then it will fire the spark 3 crank deg earlier.

[dwhe009]

cheers alot blind_elk, i have been confused alot over that one for a while. All understood now.

Still like to know if my NISSAN LAUREL C33 computer is the same as you guys gtst/gts4 stock computers.

Thanks

[grigor]

As it's not a factory installation, have you checked pin 44 (neutral switch) was connected during the fit up?

Regards.

[dwhe009]

Yeah, hooked that up when i put motor in, cheers.

But i have fixed it now anyway. I was going through all the pins on the ecu and checking there voltages against what is in a manual i found and i found my problem today. two inputs from the Automatic transmission control unit ( which off course is not there as i have a manual) where supposed to read 10V, pin 14 and 5. There where both ground (0V) on my ecu. So i hooked them through a 5k resister to 12V, and then there held at 10V while the car was on. Yay, this cancelled my self diagnostics code of 54 and im sure the car is running better.

You see, correct me if im wrong but i think when a fault code is logged by the ecu, It drops the timing everywhere (say 5 Degrees), like a safe mode. This is what i was talking about before. Sometimes the fault would come up and sometimes not each time i started the car. Just as the same as sometimes the car would fell very quick, and sometimes not. This must have been caused by the fault code. I have started the car around 10 times after i fixed the code and it has been consistly been running well.

Im so bloody glad. Cheers guys again, now for 14psi. ha