Sleepy rpm trace

djr81
Posts: 3
Joined: Mon Dec 08, 2008 2:44 am
Location: Western Australia

Sleepy rpm trace

Postby djr81 » Mon Dec 08, 2008 3:11 am

Having some problems with the rpm trace on my DL1. It works fine most of the time - the rpm matches the display on my ECU display.

Unfortunately it does not appear to work so well when accelerating from stand still, ie 5000+ rpm and a clutch dump. You can see it working as the revs rise before the start, but then flat lining shortly thereafter. It does much the same on the gearchange from first to second.

The exported graph is here:
http://s517.photobucket.com/albums/u337/djr818994/

I have tried modifying the maximum allowable rate of change values to huge numbers & varying the smoothing but I cannot wake up the signal. It is a square wave 0 to 5V signal from the ECU to the all wheel drive computer in an old R32 GT-R.

Is it likely to be software related or a little more fundamental than that?

Secondly - there is a TPS signal as shown next to the graph. Which of these wires (if either) can I tee into to obtain the TPS info?

Thanks in advance for any help. :)

pault
Posts: 64
Joined: Fri Nov 02, 2007 4:53 pm
Location: St Charles, IL

TPS

Postby pault » Mon Dec 08, 2008 5:51 pm

Looking at the ECU schematic I would expect tapping into the throttle signal + on pins(56 and 47) would be a trial and error process.

I would first look at the voltage on that wire from 56 to 47 while varying the throttle. What is the peak, what is min? If it is in range than you may be able to connect it in directly, though there is always the chance it will keep the ECU from running the engine.

Alternately you can hook up two resistors in series from the throttle signal + wire to the throttle signal - wire. And then connect this middle point to the DL1 input. The idea here is to keep the DL1 from interacting with the ECU. The larger the resistance the less likely the DL1 and ECU will screw each other up. If you use this method, I would start with a pair of 5K resistors and see how it works.

Good Luck,
Paul

djr81
Posts: 3
Joined: Mon Dec 08, 2008 2:44 am
Location: Western Australia

Postby djr81 » Tue Dec 09, 2008 5:38 am

Thanks for the help.

The output signal from the ECU (ECCS in Nissan speak) is supposed to be 0V at 0% TPS & up to 4 volts on 100% throttle.

pault
Posts: 64
Joined: Fri Nov 02, 2007 4:53 pm
Location: St Charles, IL

Postby pault » Tue Dec 09, 2008 4:52 pm

That is in range for the DL1. So the only question is if there is some unintended interaction between the two systems.

Good luck
Paul

Turby
Posts: 296
Joined: Thu Nov 17, 2005 2:28 pm

Postby Turby » Wed Dec 10, 2008 2:12 pm

It is possible that the ECU implements some form of spark cut on overrun, if you are tapping into the coil wire you get similar results to what you see.

The alternative is to try and take the rpm feed from tacho signal coming from the ECU. More modern cars using CAN bus send the tacho signal via the CAN bus so you can't do this either.

HTH

Turby
Posts: 296
Joined: Thu Nov 17, 2005 2:28 pm

Postby Turby » Fri Dec 12, 2008 2:20 pm



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