Megasquirt Tuning - Page 2 - Tuning Forum

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Re: Megasquirt Tuning
Sunday, November 06, 2005 4:21 PM
Just FYI, you can put a second ECT sensor in the plug behind the engine where the block heater would go. I needed a reducer for this, i believe to 1/2 NPT from whatever the ect sensors are. Just an easy place to put your additional coolant temp sensors!

I still think MSTweak and the newer Vexme software should be all thats ever needed to tune your engine. As far as the AFR target tables go, I dont think you should use those in place of a finely tuned VE map. I do think they should be used AFTER you have tuned your VE map.

Re: Megasquirt Tuning
Sunday, November 06, 2005 4:55 PM
Hmm, well, I'll try the double up on sensors...if it doesn't work, well then nothing was really lost, right? Meh.

Need to pick up some relays and crap, along with the cable.

O noes!
Re: Megasquirt Tuning
Sunday, November 06, 2005 4:58 PM
i can't get MSTweak to work correctly. and my NB o2 is the best for tuning so right now, we just tuned everything a little on the rich side just to be safe, and i don't get on the gas very hard. Once the WB is here i will be doing alot of tunning for everything.

I did the same thing with the Coolant temp sensor bung as Roscoe.

So does anyone have any screen shots of there VE maps? or anything at all? just for comparing

Re: Megasquirt Tuning
Sunday, November 06, 2005 7:02 PM
Remeber guys that you can't compare VE maps directly. You have to first scale them to your REQ FUEL setting first. So that means telling us all what your REQ FUEL is when you post the maps, otherwise they are useless! I have some of Dj's maps for the ecotec, I'll have to ask him before I post them though. Stay tuned.

Re: Megasquirt Tuning
Sunday, November 06, 2005 8:35 PM
i tuned mine with ve only. i played with afr table and mstweak after dicking with the logs in excell so they would work but was unhappy with the results. just directly tuning it via the ve table seemed to work best. as for the plug i looked at that on a spare engine and saw like you said a reducer was required. this would cause 2 things. one it would move the sensor outta the direct flow of coolant. secondly it is somewhat in the way of the thermostat housing. other problem with that for my car is i have an auto. so either the trans or the exhaust mani has to come out to even get to that plug.

99 Turbo Sunfire GT | Ram 2500 | International Rollback | Mr Hanky the Suburban
Re: Megasquirt Tuning
Sunday, November 06, 2005 8:47 PM
We have the same exact engine mang. Yes, you're right about the ECT sensor coming away from the hole in the block, this was a concern of mine, but as experience has determined, it doesn't seem to matter at all. No matter where I was going to put the ECT, this would have happened anyway, so moot point for me. But you can definitely get in there without removing the manifold, its just like everything else with these cars, its a real bitch.

But, yea if tuning with only VE worked for you, thats awesome. Thats why I went MS, many options, many features and many ways to tune it.

Re: Megasquirt Tuning
Sunday, November 06, 2005 9:01 PM
yeah the auto makes it a bitch. and so long as the coolant temp sensor is over 170 degrees it wont matter its a warmup thing really. I allready had the tube and ill put the right size clamps on it later so itl be a little cleaner in there course theres nothing about my car thats pretty hehehe

99 Turbo Sunfire GT | Ram 2500 | International Rollback | Mr Hanky the Suburban
Re: Megasquirt Tuning
Monday, November 07, 2005 5:51 PM
Some ignition questions weren't resolved.

DIS ignition reference cnage for the pre 98 crank is definitely 60 deg BTDC. Judging by the pictures on the NY Jbodies 2200 page, the change in location of the crank sensor notches should change the reference angle. I'd love to get some reliable feedback on that.

Waste spark describes the arrangement of spark plugs and coils. Waste spark connects both ends of the secondary side of the coil to a spark plug, and each plug is in one of two cylinders seeing TDC at the same time. Waste spark does not describe the triggering system. Waste spark systems are used on motorcycles and snowmobiles with magnetos, automobiles with points, Ford, Dodge, and GM systems as well as import cars.

The GM OBDI and many OBDII DIS systems are exactly the same as the HEI system from the ecm/ pcm's point of view. Connect the system using the same wiring, use the correct reference angle, and you'll have a reliable system. My wiring diagrams and service manuals don't indicate any reason to use an OBDI ignition module, though practical experience may say otherwise.

Coolant temp circuit inside the ecm/ pcm does indeed switch pullup resistors. Sharing the sensor is definitely an invitation for problems. Placing the CTS above the thermostat is also an invitation for problems, as the sensor will not indicate correct engine temp during warmup. The t-stat blocks coolant flow until temp is reached, then it quickly opens. When an engine is first warming up the t-stat can go through several rapid open / close cycles. Placing the sensor in the block but outside the path of coolant usually works well. The engine does not warm up quickly enough to cause a serious lag in reported temperature.

Wide band readings are affected by timing. Retarding timing tends to cause the exhaust gas to indicate a lean condition. Advancing it tends to show richer fuel. So far the best way to lock in cruise timing seems to be picking an AFR then varying timing by a few degrees + or - to see what affect it has on TPS. If you can cruise with the least throttle opening, you should be getting the best mileage. Lots of highway time is extremely helpful in this regard.

I have said before that it would be extremely cool to log OBDII data while driving around to compile a timing map for the 2200. I can post 2.2L timing curves (both mine and stock) but with the combustion chambers in the 2200 being "new and improved" (how can they be both??) I don't know how close the older spark values will be.

Happy tuning.
Re: Megasquirt Tuning
Monday, November 07, 2005 8:03 PM
thats is some great info. I might have to start researching more on the subject so i can run spark through megasquirt on the motor i'm going to build this winter.

Re: Megasquirt Tuning
Monday, November 07, 2005 8:59 PM
Slowolej, I'll spend some time later finding the specifics on the ignition so we might hear your input on it..

Re: Megasquirt Tuning
Monday, November 07, 2005 9:10 PM
im definately lisening in on this one. id love to get my ignition going w/o having to convert to edis but ill do whatever it takes.

99 Turbo Sunfire GT | Ram 2500 | International Rollback | Mr Hanky the Suburban

Re: Megasquirt Tuning
Monday, November 07, 2005 9:26 PM
Here are some links I've never seen before.. Looks like the MSII can definitely do I4/V6 DIS ignition control.. I'm still trying to find out why you need OBD1DIS module/coil pack though..

Slowolej, I'd love your input on this..

Re: Megasquirt Tuning
Monday, November 07, 2005 9:27 PM
Re: Megasquirt Tuning
Monday, November 07, 2005 9:33 PM

The IDI used by the Quad 4 will not work IIRC. I will have to find a schematic to be sure, but I dont think it uses an EST and BYPASS circuirty. The 7X signal and crank shaft position sensor are fine, but the 96 and newer J-Bodies DO NOT use an EST/BYPASS type ignition module. These cars dont really have an ignition module, instead there are a pair of ignition control signals that come from the ECM/PCM. But you can still put on a different DIS system on the Quad 4 and MS will control it! You will have to find a 2.0L or 2.2L 4 cyl DIS module/coilpacks from something like a 1990-93 Cavalier, Corsica, Baretta, Century, Ciera OR 94-95 S10/Sonoma with the 2.2, then wire it up as shown in the DIS thread.


Re: Megasquirt Tuning
Monday, November 07, 2005 9:58 PM


*Note- Any of the later model GM DIS systems that DO NOT have a BYPASS circuit and/or have multiple EST (IC) circuits to each coil driver (referred to as “up-integrated” systems by GM) WILL NOT CURRENLTY WORK as MS (and MS2 as far as I am aware) has only a SINGLE ignition control circuit. In a great many cases such as the Saturn 1.9, J-body 2.2 (LN2) and Quad 4s and even ECOTECs, it should be as simple as replacing the factory DIS ignition module/coils with one of the older “bypass” style, connecting it as shown, and making the appropriate adjustments via MegaTune. I’ve been compiling some AC Delco part numbers to facilitate these retrofits, and will post them in a future post here.

Re: Megasquirt Tuning
Monday, November 07, 2005 11:16 PM
This about sums up the procedure for replacing our existing DIS system with the older preobd2 DIS system, WITH part numbers (not guaranteed to be accurate)..

Megasquirt 4 cylinder DIS Compatibility/ Conversion and Parts Summary <UPDATED OCT 18 2005>
* unless otherwise noted, all references to Megasquirt are referring to PCB Rev 2.2

The following North American 4 cyl engines that use GM DIS are current directly compatible with Megasquirt rev 2.2 using MSnS-E.
These are to be referred to as “MSnS-E Compatible Engines.”

MSnS-E Compatible Engines
1987-1989 2.0 VIN 1 used in Beretta, Cavalier, Corsica Skyhawk, Tempest, Firenza
1987- 1992 2.5 VIN R/U) used in Fiero, Grand Am, 6000, Cutlass Ciera, Cutlass Calais, Celebrity, Lumina, Century, Skylark
1988- 1992 2.3 VIN A (LG0) Quad 4 DOHC H.O. (High Output) 1987-92 N Cars 1990-92 L Cars 1990-91 W Cars
1988- 1992 2.3 VIN D (LD2) Quad 4 DOHC 1987-92 N Cars 1990-92 L Cars 1990-91 W Cars
1992 - Only VIN 3 (L40) Quad 4 SOHC 1992 N cars (Grand Am, Achieva, Skylark)
1990-1991 2.2 VIN G used in Beretta Cavalier Corsica
1991- 1994 1.9 VIN 9 Saturn SOHC (Single Over Head Cam) w/TBI
1995- 1995 1.9 VIN 8 Saturn SOHC (Single Over Head Cam)
1991- 1995 1.9 VIN 7 Saturn DOHC (Dual Over Head Cam)
1992-1993 2.2 VIN 4 used in Cavalier, Corsica, Berretta, Century, Cutlass Ciera
1994-1995 2.2 VIN 4 used in Chevy S10 and GMC Sonoma

*Note* the term “VIN x” refers to the 8th digit of the Vehicle Identification Number which indicates the ENGINE CODE or VIN CODE for the applicable engine

These MSnS-E Compatible Engines have several things in common.
- All of these engines use GM Direct Ignition System (DIS) which is a “waste spark” ignition with a coil pack for each pair of mated cylinders.
-All of these engines use a 7X crankshaft reluctor with 6 evenly spaced notches 120 degrees apart and 1 “sync” notch 10 degrees after one of these.
-All of these engines use a 2 wire VR type crankshaft position sensor (CKP) which is mounted in a sealed bore in the engine block, adjacent to the 7X reluctor ring.
-All of these engines’ spark timing was controlled by a GM ECM/PCM using BYPASS>EST circuitry, similar to HEI 7-pin.
When the engine was cranking (or less than 400 rpm) there will be 0V on the Bypass circuit and ignition timing is controlled by the DIS module. After the engine starts (rpm greater than 400) the ECM applies 5V to the Bypass circuit, triggering the module to hand-off control of the coil primary circuits to the ECM via the EST circuit. The ECM controls the ignition timing advance and retard, as engine conditions dictate- in “next cylinder” mode.

MSnS-E Compatible Engines will immediately function with a correctly connected Megasquirt with full ignition timing control providing that the MS has the appropriate internal modifications. These modifications require re-routing the output circuits from the LED17 and LED19 circuits. The Megasquirt must also be running MSnS-E code, and have the appropriate changes made to the ignition settings in Megatune (See MSnS-E forums for more details)

ADDITIONALLY the ignition parts from most MSnS-E Compatible engines (*except VIN R/U) can be used on many newer engines (that share the same 7X crankshaft reluctor) and made compatible with the Megasquirt with full timing control.

These engines are referred to as “Conversion Candidate” engines
4 cyl Conversion Candidate engines

1996- 2002 1.9 VIN 8 Saturn SOHC (Single Over Head Cam)
1996- 2002 1.9 VIN 7 Saturn DOHC (Dual Over Head Cam)
1993- 1995 2.3 VIN D (LD2) Quad 4 DOHC (Dual OverHead Cam)
1993- 1995 2.3 VIN A (LG0) Quad 4 DOHC H.O. (High Output)
1993- 1994 2.3 VIN 3 Quad 4 OHC (SOHC Single OverHead Cam)
1996- 2003 2.4 VIN T Quad 4 DOHC
1994- 2002 2.2 VIN 4) “pushrod” L4 (LN2)
1995- 2002 2.4 VIN T) Quad 4 Twin Cam
2000- 2005 2.2 VIN F) ECOTEC DOHC L61

The Conversion Candidate engines all use a 7X crankshaft but have a NON-Bypass type DIS Module. These modules typically use 2 or more IC Control signals directly from the ECM/PCM, in effect they DO NOT have a traditional ignition module as it is "up integrated" into the ECM/PCM.For this reason these engines will not function with Megasquirt MSnS-E directly without conversion.

*Also Note the Quad 4 and Saturn DOHC engines listed above use low impedance (z) injectors and will require the injector flyback daughterboard to prevent damage to the Megasquirt injector drivers.

Conversion Instructions

Basic Conversion Information
Each Conversion Candidate engine will require specific and differing alterations to make them MSnS-E compatible:

-In general these will always include REMOVING the oem ignition module and replacing it with one from almost ANY MSnS-E Compatible engine(New or Used)

On the Quad 4 "Candidate Engines" it is recommended to use the module with complete coil and cover assembly from a first generation Quad 4 (VIN A an VIN D engines) *Email me at for the wiring schemtic as this engine combination has not been totally validated

-The connectors to the compatible module are often different than the candidate engine, requiring them to be cut off and replaced with the correctly wired compatible connectors. -In most cases the original waste spark coil packs can be maintained.
-Often the stock candidate crank position sensor can be maintained, although wiring to it may need to be altered.
-Some candidate engines such as the Quad4 and ECOTEC use Coil On Plug (COP) ignition systems, therefore a complete set of spark plug wires long enough to reach the DIS module, will be necessary.
-On those engines a suitable metallic bracket will also need to be installed to fit the DIS module and coilpack assembly. This bracket must be connected with a 12 AWG (3 sq mm) wire or braided ground to a clean engine ground point or battery negative.

Locating USED MSnS-E Compatible DIS components for Conversion
Use the “MSnS-E Compatible Engine” list as a guide for scouring your local Pick-A-Part and Wrecking yards. Note The 2.5L components may not always work with your application due to the integral design of the crank sensor used on some versions of that engine.
When you find a suitable donor take as much of the DIS system as you can :

-DIS Module and coils preferably WITH plug wires, mounting bracket and all fasteners
-DIS Connectors at the module
-Cut the connectors off with at least 6-12” of pigtail BUT try to keep the harness to the crankshaft position sensor intact! -it is a special “shielded” harness with a drain wire connected to terminal B of the 3 way connector at the DIS module.
-Salvaging the crankshaft position sensor is generally unnecessary as a candidate engine should already have one (and it may be different)

* I personally have robbed dozens of these from various wrecking yards and have paid anywhere from $1 to $100 for these components depending on their age, condition and the mood of the goof at the cash register.
** Whenever using “recycled” DIS modules and coils it’s a good idea to remove the module and coil packs and carefully clean any corrosion that exists at the module and coil mounting points. Remove any corrosion or oxidation with a bit of Scotch-Brite or steel wool. Clean any corrosion on the coil and module mounting bolts with a wire brush or run the correct die over the threads. Rinse all grease and oil from the DIS parts with contact cleaner or BrakeCleens.
This little bit of extra work is well worth it as will prevent misfires and erratic performance caused by high resistance and/or shorts.

Purchasing NEW MSnS-E Compatible DIS components for Conversion
Often someone putting together a new Megasquirt installation will not wish to compromise the integrity of the installation with used parts. By using NEW parts you not only get a warranty, but you also eliminate potential headaches caused by faulty used components. *Remember it was in an accident, it may LOOK OK but still be DOA!

For this purpose I have compiled a list of AC DELCO components used on the MSnS-E Compatible Engines. Remember, I’m NOT a partsman! I believe them to be accurate but cannot accept any responsibility for the accuracy of these part numbers that I have taken directly off of AC DELCOs on-line catalog at:

4 cylinder DIS Components for the following MSnS-E Compatible Engines
Instructions:Choose any one of the 3 applications below and order ALL associated parts (DIS module, connectors, brackets etc) for that application. Feel free to use ANY parts source (you don’t need to use AC Delco) The only real practical difference between them is the connectors used, and maybe the mounting. There may be some undocumented differences in current limiting and/or bypass advance levels.
Heck, that’s what we’re here for right??

1992-1995 2.2L VIN 4
DIS Module- AC DELCO PN# D1996A
Alloy Bracket for D1996A – PN#10495161
DIS Coils for D1996A- AC DELCO PN# D555
Harness Connectors (3) for D1996A:
C1 AC DELCO PN# PT787 (6-way)
C2 AC DELCO PN# PT782 (3-way)
C3 AC DELCO PN# PT1798 (2-way P2S)

1987-1991 2.0 VIN 1, 2.2 VIN G
DIS Module- AC DELCO PN# D1927A
Alloy Brackets for D1927A – PN#10495161
DIS Coils- AC DELCO PN# D555
Harness Connectors (3) for D1927A:
C1 AC DELCO PN# PT787 (6-way)
C2 AC DELCO PN# PT782 (3-way)
C3 AC DELCO PN# PT205 (2 way “L” shape)

1988-1992 2.3 VIN A,D,3 Quad 4
*Parts to convert 1993 and later "Candidate" Quad 4 Engines to "MSnS-E Compatible" DIS Ignition
DIS Module - AC DELCO PN# D1935A
DIS Coils - AC DELCO PN# D563
Harness Connectors (2) for D1935A:
C1 AC DELCO PN# PT701 (11-way)
*May be able to use existing 11-way connector WITH REWIRE

**May also wish to change Cam Cover Assem to older style
10497610 VIN D Embossed " 16V Quad 4 DOHC "
10468402 VIN A Embossed "High Output 16V Quad 4 DOHC"
10470589 VIN 3 Embossed "Quad OHC"

1991-1995 Saturn 1.9 (all variations)
DIS Module: AC DELCO PN# D1950E (2 connector style)
Alloy Bracket for D1950E – NPN
DIS Coils- NPN
Harness Connectors (2) for D1950E:
C1- Saturn PN# 12084220 (6-way)
C2- Saturn PN# 12084416 (5-way)
The Saturn Compatible DIS Module has only 2 connectors as the CKP sensor is incorporated into the 5-way C2 Connector (see schematic)
*NOTE* All DIS Mounting brackets must be GROUNDED to the engine block or B-

Crank Sensors - It is generally recommended* that you install a NEW Crankshaft Position Sensor in the “Candidate Engine” at the time of conversion.
*WARNING – If the old sensor will not pull out from the block easily LEAVE IT IN. These sensors have been known to break if too much force is applied during removal. Sometimes the broken end can be removed from the block with a small screw in dent or seal puller. Worst case scenario is having to pull the oil pan or even the crank to extract the remains of the sensor.

Crank Sensors for “Candidate 4cyl Engines”
1989- 1992 2.3 VIN A: AC DELCO PN# 213-970
1989- 1992 2.3 VIN D: AC DELCO PN# 213-970
1992- 1994 2.3 VIN 3: AC DELCO PN# 213-970
1994- 2002 2.2 VIN 4: AC DELCO PN# 213-235
1995- 2002 2.4 VIN T: AC DELCO PN# 213-970
1996- 2002 1.9 VIN 8: AC DELCO PN# 213-2816
1996- 2002 1.9 VIN 7: AC DELCO PN# 213-970
2000- 2005 2.2 VIN F: AC DELCO PN# 213-970

Crank Sensors for “Compatible 4cyl Engines”
1987-1989 2.0 VIN 1: AC DELCO PN# 213-148
1987- 1992 2.5 VIN R/U: AC DELCO PN# 213-154
1990-1991 2.2 VIN G: AC DELCO PN# 213-148
1991- 1994 1.9 VIN 9: AC DELCO PN# 213-2816
1995- 1995 1.9 VIN 8: AC DELCO PN# 213-2816
1991- 1995 1.9 VIN 7: AC DELCO PN# 213-2816
1992-1993 2.2 VIN 4: AC DELCO PN# 213-148
1994-1995 2.2 VIN 4: AC DELCO PN# 213-148


Crank Sensor Harness

AC DELCO PN# 10486180 is a SHORT shielded Crankshaft Position Sensor (CKP) harness that includes the 3 way harness connector (at the DIS Module) and the 2 way connector at the CKP. It may be too short for many applications, but could certainly be lengthened providing you maintain the shielding by using shielded twisted pair audio wire.

Navigate to this AC DELCO Web-Site
and Click on “Display Part Number Image By AC Delco Part Number”
ENTER the Part Number to see a picture of the applicable part (If Available)

Credit goes to WopOnTour for this information from

Re: Megasquirt Tuning
Monday, November 07, 2005 11:19 PM
Major thumbs up to Excidium for dooin all this research!

if i get time this weekend ill try it.

99 Turbo Sunfire GT | Ram 2500 | International Rollback | Mr Hanky the Suburban
Re: Megasquirt Tuning
Tuesday, November 08, 2005 8:31 AM
I've got the basic documentation for how I have connected my MS. It's not so much a diagram than a connections listing, but it does the job I think.

MegaSquirt Connections

Let me know if I missed much or if more detail is needed.

Re: Megasquirt Tuning
Tuesday, November 08, 2005 12:52 PM
lol after reading half those links, and this page I'm am started to hate you guys, and the people on MS.....j/k

you are all to smart for me, and now got me really interested in this ign control. So i'll prolly go through a couple dozen sleepless nights reading about it and learning about it so i can run it correctly.

thanks for the helpful info on the subject. lets keep the discusion going

Re: Megasquirt Tuning
Tuesday, November 08, 2005 1:02 PM
PoundinFire: Awesome job! If you could post that information in a more graphical format it might help benefit those of us without MS word, though I will have to install it again for the meantime.

Re: Megasquirt Tuning
Tuesday, November 08, 2005 1:06 PM
I'll do that tomorrow on my day off. I just finished that in some sneak sessions at work today.

Re: Megasquirt Tuning
Tuesday, November 08, 2005 4:26 PM
Having some issues, Laptop won't communicate with MS2. What do I need to do? I purchased fully assembled, it was ran through the stimulator. What usb to serial cable adapter do i need? Can I get it at best buy? Thanks!

O noes!
Re: Megasquirt Tuning
Tuesday, November 08, 2005 6:06 PM
any of them should be fine. ust make sure its set to the right speed and emulates com port 1-4 not 5 or higher. also make sure megatune is set to the same firmware revision you have.

99 Turbo Sunfire GT | Ram 2500 | International Rollback | Mr Hanky the Suburban
Re: Megasquirt Tuning
Tuesday, November 08, 2005 7:42 PM
Excidium found the basic reason why MS won't work with some of the newer ignition systems. The Q4 was the first engine which didn't have a "real" ignition module. My notes listed the 2002+ 2.2 Ecotec as needing an older module, but it turns out I was working from notes about swapping OBDI onto an Ecotec engine. I guess I need to label my notes better. Anyway, the next step is to figure out if the OBDI ignition module can replace the OBDII part, or if they need to be used together to keep things like the airbag and bcm happy.

I have pcm pinouts if needed.

Re: Megasquirt Tuning
Wednesday, November 09, 2005 1:49 PM
converted to pdf for those who don't have Word : MS Connections

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