Gearhead_42 Dork
8/24/14 10:37 a.m.

I'm finishing the install of my megasquirt DIY PNP

1993 Nissan 240SX KA24DE engine and harness. Is there a spot under the hood I can wire in the IAT? Install docs state to use "the orange and white wires that come into pins 16 and 17 of the ECU from the MAF"... well they don't exist. There are only 3 wires in the MAF harness, fat black, fat white and black/white stripe. Any chance they're just cut off somewhere further up the harness?

Gearhead_42 Dork
8/24/14 10:51 a.m.

Or am I being pedantic and just need to connect to a ground (17) and the signal (16) on the MAF and screw the color?

WonkoTheSane Reader
8/24/14 11:06 a.m.

The second one. AIT is like any other temp sensor, give it 5v and read the resistance.

Gearhead_42 Dork
8/24/14 12:14 p.m.

OK, I seemed to guess correctly as the IAT is accurate on the tunerstudio dash. CLT isn't even close (42F) using the quoted Nissan stock calibrations. No start, there's fuel and spark but they seem to not be meeting at the proper times. Occasional (mis)firing only.

Out of time for the week, back to baby daddy duty.

bentwrench HalfDork
8/24/14 12:39 p.m.

Are there wires on those pins at the ECU connector?

WonkoTheSane Reader
8/24/14 7:31 p.m.

Is it possible that the dizzy is stabbed 180* out? I.e., you're on tdc of have exhaust stroke instead of compressrion?

Looks like its time to figure out the ohms for that sensor.. That's always annoying... Can you thread a generic chevy sensor in its place? I forget what that sensor was setup like...

Although, if the sensor isn't within normal Nissan range, I wonder if that's why the engine felt down on power? The ecu never got the right temp?

Gearhead_42 Dork
9/12/14 10:08 a.m.

More questions (surprise) Still fighting to get the initial start so I can set timing etc. Latest versions of diypnp/microsquirt firmware and updated paid version of tunerstudio.

I have installed the diyautotune optical trigger wheel in my distributor, in place of the stock 360-slot unit. All other ignition components are stock.

What ignition settings should I be using , especially trigger angle? I have the fixed timing at 15 degrees and the crank advance at 10 with the "trigger angle" set at 345 with the settings in "toothed wheel" mode.

Secondary, any gotchas when using four injector drivers for full sequential rather than the two outputs that are stock? Need to double any suggested pulse widths or anything like that?

And before anybody says "rtfm", I've r'd every f'ing version of the m I can find, and most of them disagree on some point or another

MadScientistMatt UberDork
9/12/14 11:09 a.m.

Is the CLT reading fixed? Getting a good start without it is going to be very tough. If it isn't, let me know what volts you see with key on and engine off at the CLT terminal.

Trigger wheel and wheel decoder settings are given here:

Pulse widths are automatically scaled for sequential when this is enabled, so that one is no big deal.

Gearhead_42 Dork
9/12/14 12:30 p.m.

In reply to MadScientistMatt:

So these then? (MS2/Extra since there's not separate microsquirt section) TunerStudio settings (Sequential coil on plug and / or sequential fuel)

Settings under Basic Setup -> Tach Input / Ignition Settings: Spark mode: Toothed Wheel Ignition input capture: Falling Edge Spark output will depend on what output setup you're using. BIP373s and QuadSparks both use Going High / Inverted. Getting this setting wrong can damage the ignition module and/or coils. If the ignition module or coils get hot with the key on and the engine off, turn the key off immediately and select the opposite output setting. Settings under Basic Setup -> Tach Input / Ignition Settings: Trigger wheel arrangement: Dual wheel with missing tooth Trigger wheel teeth: 12 Missing Teeth: 1 Tooth #1 angle: 345 (This varies slightly between individual engines. Check with a timing light and adjust as needed.) Wheel speed: Crank wheel Second trigger active on: Rising edge

That's what I have in there. I'll dig though the menus again to verify, I was really hoping maybe those weren't the correct ones :lol: Like I said, I'm "single coil" but at the same time the "and/or" sequential fuel puts me here. Going high/inverted is still correct for the stock ignition system though?

David S. Wallens
David S. Wallens Editorial Director
9/12/14 5:22 p.m.

I have nothing to add other than thanks, Matt, for helping a reader with a question.

Gearhead_42 Dork
9/12/14 8:09 p.m.

I love that Matt is on here... The GRM forums in general are way more laid back yet more helpful than the "specialist" sites, generally. I'll almost always come here first

Gearhead_42 Dork
9/21/14 7:01 p.m.


I gave up, and started a new clean slate project offline using the OTS tune for the S14 ka24de. Made the required changes for the sequential injection and the trigger wheel, and only then went out and hooked to the ECU.

Got the mismatch warning, accepted all, and burned all offline settings without changes. Calibrated iat and CLT, calibrated TPS, burned and cycled power once more for good measure.

Fired immediately and settled into a factory smooth 700rpm idle. Wow. Dizzy timing was at 5atdc so I moved it over one tooth and locked into 15btdc. Clicked off fixed timing and idles smooth as butter at 1200.

Lots of tuning to do but I am just giddy with antici

Pation. ChumpCar here we come!

Thanks so much for the assistance Matt and everyone!

Shameless plug for us, check out Chubby Gecko Motorsports on the book of face, and stop by the ChumpCar Sprints at PittRace if you're in the neighborhood :)

WonkoTheSane Reader
9/21/14 9:14 p.m.
Gearhead_42 wrote: Success!

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