Rally Neon 2GN MS3 / MS3X - Started and now some questions.

Just install MegaSquirt or some other system that allows you to tune your car or just have a question about tuning and the options available? Feel free to ask it here.
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Rally Neon 2GN MS3 / MS3X - Started and now some questions.

Post by webkris » Tue Nov 05, 2013 2:17 pm


Last night after changing settings to 36-2+2 I got the Rally Neon started and running! :rockon: http://youtu.be/jM1V6h9mrZU

My setup is a BONE STOCK 2003 SXT SOHC MT - wired for standalone. Besides being a rally car - Build Log - viewtopic.php?t=57224
The plan is to get the wiring and settings dialed in with a "known good engine" before dropping in the "hot motor" with compression and cams.
We're going all motor instead of turbo so that we can continue to kick ass in the Group-2 class. :)
I'm using the stock harness so I can go back to the NGC PCM if need be.
I'm using all of the stock sensors! I'm surprised when I see threads from 2013 that ask about installing GM sensors.
I've got the coil pack setup for wasted spark as COP seemed like more of a hassle than a benefit.
Fuel is being run from the MS3X - goal is to get it full sequential, but I need a CAM signal before that will work.

Here is the 2GN NGC wiring guide that I made / have been working off of:

Here's the folder with my current settings and logs if you're interested: http://rallynotes.com/megasquirt/

Cam Signal Issues:
Checked with my scope and I have a good 5v CAM signal.
Never see cam signal on "Composite Log".
Where - besides ignition settings - do I have to specify the cam input as "MS3X Cam In"?
Will it only show up when I set the fuel to "full sequential"?
Here is my latest .msq - http://rallynotes.com/megasquirt/2013-1 ... .36.35.msq

IAC Issues:
As mentioned - using the stock 2 wire IAC. Certainly easy to power with 12V and connect to the PWM Idle, over the 4 wire 1GN model.
It only starts to open at like 80% and then is full open at 100% - what settings should I tweak here?
I noticed a pretty god awful squealing noise when set to default 1021Hz. I set it down to 500 and that went away, but I think with PWM it means it may run hotter. Any recommendations here?

By The Way:
This is a SymTech Labs MS3 - and although I was disappointed with their production and delivery expectations. I'm impressed with their build quality and setup. The computer came with a base map for my Neon and after selecting the correct settings - started up surprisingly well.

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Post by occasional demons » Tue Nov 05, 2013 10:40 pm

Other than their little hiccup with delivery times, they have been pretty helpful. Possibly they can help you out. Or possibly some other knowledgeable member may chime in.
dblsg wrote:ya'll a bunch of post whores

2001 Neon ES MTX with '02 R/T PCM
Help support 2GN!

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Working it out...

Post by webkris » Thu Nov 07, 2013 1:45 am

I got closed loop idle working. (see settings below)
I apparently never tried the sequential setting with the 36-2+2 trigger setting - and then got it all working. My cam signal showed up!
If anyone has any feedback on these settings - I'm open
So, is this the first "standalone MS3 2GN NGC"? If not, let's compare notes.

- Kris


Last edited by webkris on Thu Nov 14, 2013 6:08 pm, edited 1 time in total.

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Post by webkris » Thu Nov 14, 2013 6:07 pm

Okay here's what I have learned in a week.
#1 The PWM Idle wire from my MS3 was not setup to a 12V driver..
I was sort of stunned when I only saw 5V coming from it, and then I realized 2 things immediately: This was driving the IAC with a tiny transistor. Because this was 5V I now understand why 100% was needed to open it a little and 40% closed it. The signal was still working after my IAC stopped working, so who knows if I can ever use that again. Symtech does correctly list this as "(opt.)" on their diagram. It was an option I didn't have installed - because...

Good news is that I have IDLE wire from the MS3X. It turns out that IS setup with a 12V driver and can be directly connected. Updated my wiring guide. I'm removing my old idle settings - I suggest P=20 I=50 and D=0 to start with. Make sure you set where YOUR CAR revs to with the IAC open and closed. Mine was like 3500 / 600 RPM.

#2. Unlike 95-2002 the 2003+ NGC 2GN Alternator Field Coil is wired to GROUND.
If you are fuzzy on the directions and want to keep stock wiring (my goal) you will fry your $19 voltage regulator. Wiring the alternator will require you to change the stock connector to 12V+ and signal from the regulator. I chose to make this a new (separate) connector in case I ever need to switch back to the stock computer I don't want a 12V line run to something that expects GROUND.

Helpful links:
This explains the diode and ASD / Fuel Pump wiring - http://www.symtechlabs.com/support/know ... irt:relays
This explains the voltage regulator wiring - http://www.symtechlabs.com/support/docs/VregInstall.pdf

Vehicle Speed Sensor
I was able to get VSS working through some trial and error. The stock sensor wired to PT4 LOGIC can be used with the following settings: Driveline / 4 teeth / 23" tire diameter. I verified these settings with the rally computer already tapped into the stock sender. IMPORTANT NOTE - All VSS settings require a power cycle! Even when they say they don't...

Updated Guide
I now have all of the connections I made to do a full standalone setup. My advice to anyone trying this is - let the stock computer go... There is just no need to keep it around when it will only be pissed at idle or have to deal with duplicate sensors. I updated my wiring guide (above) http://rallynotes.com/megasquirt/ms_2gn_wire.png with all these discoveries.

DATA! I won't bore you guys with hours of tuning data, but I was finally able to make a 3rd gear wide open throttle run:
Good luck with your MegaSquirt install! - Kris

Last edited by webkris on Fri Nov 22, 2013 2:14 pm, edited 1 time in total.

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Post by fixit » Tue Nov 19, 2013 1:26 pm

Subscribed, thanks this is very helpful--
My plan is for a stand alone ms2 to run srt4 motor

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Post by webkris » Tue Nov 19, 2013 5:10 pm

fixit wrote:My plan is for a stand alone ms2 to run srt4 motor
Standalone IMO avoids a lot of weird idle and tuning issues. I would recommend the MS3 w/MS3X or an MS3Pro instead of the MS2, but I know a lot of 2GN guys have had great luck with the MS2 and there is a big install base. The 3 has been out for a while now, and I really think the MegaSquirt in general has grown up in the last 5 years.

Having fun with THIS last night: http://youtu.be/nxeuDeBa-vQ

- Kris

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