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LS1 MegaSquirt Install

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I think mine are still powered by 5 volts for MS1 v2.2 or v3.0 boards. Where did you see something about me using 12volts? I will use 12 volts to power them with MS3, but not MS1/MS2. Here is the line from the install guide:


Both crank and cam sensors are powered with 5 volts. It has already been confirmed by other people that both sensors return a 5 volt square wave logic signal. I did find new info that in the factory setup both sensors are powered by 12 volts, but 5 volts works without the need for other circuitry to interface with the processor.

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FYI, I have moved on to MS3 running my LM7 engine (LS series).  There are a couple general notes I can add here.  I am using truck coils, round style with the heatsink.  Apparently they will autofire if dwell is too high.  Check on the msextra forums if you are running these.  I am not seeing any problem with them, but I am using the suggested dwell values (4ms cranking and running).  The default dwell battery correction table with MS3 is based on the stock GM dwell table for these coils.


Also, my final electrical gremlins came down to three things:


1.  I did not have adequate power supplied to each sub system in the car.  I added new wiring of the proper size for each system (coils, injectors, fuel pump, etc)


2.  I was routing my high voltage grounds from the LS coils through the harness, which was radiating noise onto other sensor wires.  Now I ground these at the cylinder head per the instructions in the MS manuals.  The instructions may not have been there when I first did this install, or I did not read close enough.  Take your pick :-)


3.  Making sure grounds are all well connected.  Very basic stuff.  To fix this I now ground my battery to the cylinder head at the same bolt using a copper bus bar that I have on my MS3/fuse/relay backboard.  Then all grounds (except high voltage coil as mentioned above) go to the copper bar.  It has 6 studs on it to easily connect everything: MS3 grounds, MS3x grounds, sensor grounds, cylinder head ground - heavy gauge wire, wideband grounds, etc...


Good Luck on your installs and don't hesitate to contact me with questions.  This is what I love to do :wink:



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Only new thing I did with this setup is install a toggle switch for E85 to Pump Gas.  Now if I want to switch back and forth I pull into the filling station near empty and fill up with the other fuel type.  I then start the car and wait for it to stutter, signalling me that the new fuel has made it all the way to the engine, then flip the switch.  This works well for me, it only takes a couple seconds after firing up.


Here are my notes:


Tuner Studio indicator for tableswitch watches portH6, it is inverted.  Meaning when the toggle switch is in the default position, down then it is open and portH6 see a high or ON state and this will be the base state for E85.  When the toggle switch is flipped up then portH6 sees an OFF condition because the switch shorts the tableswitch wire to ground, this is the pumpgas position.


E85 uses all 1 tables and gas uses all 3 tables.


Went ahead and added warm up and after start to tableswitch.  Now table switch does following:

·         VE table

·         Spark table

·         AFR table

·         Required fuel

·         Priming pulses

·         Cranking %

·         WUE %

·         ASE %

·         ASE taper


Pumpgas required fuel  5.1

E85 required fuel (+34%)  1.34*5.1=6.83

Increase priming pulsewidths by 34% for E85

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