240sx SR20DET - DIYPNP

[AdrianD2]

Hey guys,

I am getting around to finishing up a DIYPNP build for a 1993 240sx with an early "Redtop" SR20DET.
We are trying to run sequential ignition and sequential injection.

My first issue is with reading the CAS Trigger Wheel. I am using the DIYautotune trigger wheel seen here... https://www.diyautotune.com/product/50- ... or-ka24de/

There are 4 pins on the CAS connector. Power, Ground, 180* Signal(Inner Optical), and 1* Signal(Outer Optical).
Where should I be routing these two signals into the ECU? From what I understand it should be OP+(LowRes?) and VR2+(HighRes?), and then configure in Tunerstudio for the wheel.

The second issue is the ignition. The car has COPs from the factory, however they are controlled with a "Power Transistor Unit"
Quoted from the Nissan FSM: "The ignition signal from the ECM is amplified by the power transistor, which turns the ignition coil primary circuit on and off, inducing the proper high voltage in the secondary circuit."
How I have understood it is that I can use 4 logic level ignition outputs to talk to the PTU (Power Transistor Unit) and then it will in turn fire the coils. Am I correct in thinking so?

Trying to wrap my head around a few things just to make sure everything is okay before we install and attempt to start.

[billr]

As to the coil driver, the answer is "maybe". Do you know what the PTU expects for an input signal? It would be nice to assume the stock ECM was outputting a fairly standard "logic level" (in regards to voltage thresholds and current), but that may not be so...

[CRSTune]

MS2 systems can't use the stock trigger wheel so when running, it has to use basic trigger using the 4 cam teeth as "crank" teeth. That would mean the cam signal is actually fed to the ECU's crank input (they're swapped). DIYAutotune made it easy for users and documentation by swapping the teeth locations on their trigger wheel. So, the crank signal becomes the cam signal and vise versa.

Now that you know that, you're going to feed the "low res" signal to "OPTO IN +" while the "high res" signal will go to "VR2 IN +"

That PTU you're talking about is the ignitor. It will communicate directly with the Megasquirt logic level outputs.

[AdrianD2]

I do not know what the stock ECU outputs to the Igniter, I've been searching up and down through FSMs for that answer.

@CRSTune - Thank you for your response! I will make that change to the MS tonight.

Hopefully after this, everything will fall into place. I'll keep this updated. Thanks guys!

[AdrianD2]

I believe I have everything set up Basic setting and Ignition wise.

Would some care to double check? I've already fried one igniter, I don't want to destroy another LOL!

[CRSTune]

Your dwell is probably too high.

Set "Nominal Dwell" to 1.9ms. Cranking dwell can be 2ms.

It also does not need a lot of voltage compensation either for dwell. Try the following table:
8V - 142
10V - 118
12V - 102
13V - 100
14V - 98
16V - 92

[AdrianD2]

Thanks again for your help CRS!

[AdrianD2]

Any additional confirmation on the .msq?
Much appreciated!

[CRSTune]

Are you still having the problem with the ignitor? I'm assuming that you have the motor running.

Nothing specifically wrong (other than what I mentioned previously) is jumping out at me. Those settings should work and get you going.

With that said, here are a few things I'd do differently or have noted:
-Set timing pulse to "End-of-pulse" as opposed to "Start-of-pulse." I'd also use an injection timing table rather than a single value.
-I've found I can run 10-15deg of cranking advance on these engines. Experiment and see what you get. You should notice it start with more strength. Of course, I'm assuming you've timed and set this motor.
-Get your general sensor lag factors as high (closest to 100) as possible. You only want as much smoothing as is necessary but less smoothing can improve response.
-If you have the injector deadtime data, use it.
-When you get the car running well enough, turn on "over-run fuel cut."
-I haven't known the Nissan idle valves to run inverted. Have you noticed anything weird with the idle?

[AdrianD2]

Unfortunately we do not have the car running yet.

RPM signal doesn't seem to be correct. While cranking I see values well over 1,000 RPM.

Not really sure where to go from here. I have the trigger wheel settings correct. MSQ is above in a prior reply.

I've attached two datalogs, any advice? Thanks guys!

[CRSTune]

It's not picking up all the tach events. Sometimes the cam signal drops out. Other times, it loses crank tooth signals. What pull-up are you running on the signal wires?

[AdrianD2]

Looks like I left off the Pull-up for VR2 when I added the jumper when I modified it last...

Any recommendation for which pull-up resistor to use there? I assume to 5v as well?

[CRSTune]

1K to 5V will work.

[AdrianD2]

1K to 5V will work.

Thank you! You have been a massive help!!

[AdrianD2]

I still can't seem to get RPM to read properly.

Still getting values that jump beyond 1,000 RPM, even up beyond 4,000 RPM.

Any more insight on this perhaps? Are there more mods that I have to make to hardware?

MSQ attached for reference.

Thanks!

[Matt Cramer]

Can you post a tooth log?

Also, how is the CKP input set up? It looked really ragged in the composite log.

[AdrianD2]

Hey Matt,

Thanks for the response, the owner of the car will be back in town this weekend, so I will be able to get the log.

I've never done a tooth log before, but I will look for a write-up.

Thanks!!

[Matt Cramer]

We've got a write up here:

http://www.msextra.com/doc/pdf/html/Meg ... 4-188.html