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Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/30/21 12:14 p.m.
alfadriver said:
Stefan (Forum Supporter) said:

Here's some info on the various versions:


Basically, MS3 with MS3X provides faster processing speeds, sequential fueling/spark up to v8's, more support for OEM trigger options, on-board SD Card logging and serial to USB adapter.

Starting with MS2, CAN-BUS support is provided which allows more flexibility for logging/dash support, etc.  You can add sequential fuel and spark support with add-on boards and different firmware.

I have seen that.  But someone needs to explain how that makes a simple CIS ACVW motor before suggesting that someone takes that step- or in my case, a SPICA Alfa Nord motor.

How would all of those additions help vwcorvette or myself?  Would either of us notice the difference between a Micro and an MS3?  I'm also assuming that the VW won't be changing the dash- I know I would not be.  

I'm not trying to be difficult- it's just that many times a MS subject comes up, the greater power of the MS3 always comes up without a strong explanation why it's so much better for a simple 4 cyl engine.

This is one of the issues I've had with the Megasquirt community - a lot of people assume that everyone wants what they want.  Like, people getting almost irate at you for not running sequential staged injection with coil on plug and three networked Android displays for a full digital dash, when all you are interested in is replacing a carburetor.

For what you want to do, an MS1 running fuel only would work just fine.  MS2 offers finer tuning than 8x8 tables and .1ms injector on-time resolution, but with an older engine engineered to have a gentle VE slope so mechanical FI would work fine, you don't really NEED more than that.  (This goes for the VW too)

​​​​​​The MS2 CAN is send only, if you want to read networked inputs such as from a wideband controller, you need MS3.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/30/21 4:24 p.m.
alfadriver said:

In reply to MadScientistMatt :

I don't have a path to install a stepper IAC

To quote Independence Day, that's not entirely accurate. smiley  GM had a neat little idle control mechanism on certain Cadillacs.  It was a stepper motor like all of their other IAC strategies, but this was a throttle stop.

The throttle stopped against it, just like the idle speed screw on a carb.  You rotated the nut manually to set base idle airflow, and it would extend/retract to control idle speed.  A switch was also incorporated in it to turn on idle control strategy, but I don't know if any flavor of Megasquirt could utilize that.  I suspect GM did that because they could not rely on a TPS threshold, since the IAC by nature would also move the TPS.


With this and a little bracketry, people with ITBs should be able to have computer controlled idle speed without having to have a soggy mess of vacuum tanks and plumbing.


Whether you feel a need to add a layer of complexity is one thing (personally, I'm fine with no idle control) but it should be possible with easily sourced components.

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
7/30/21 8:41 p.m.

In reply to Pete. (l33t FS) :

The only downside of ms1 is the processor is nla new and the software layout and menus are arranged a little different than ms2/3. Best to start with ms2 or better if you don't have a good reason to pinch pennies. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/31/21 8:08 a.m.

In reply to Paul_VR6 (Forum Supporter) :

True.  Availability is a huge concern.


I went years, and many tens of thousands of miles of driving, with a fuel only MS1.  1.01 circuit board, even smiley  I have an MS2/Extra in there now, but it is still fuel-only, because I prefer the fast starts that a distributor can get you.  If the engine stalls, I can just bump it with the clutch and it will re-fire within the next 180 degrees.  No need to spin the engine over 360 degrees for it to resync, and then more degrees to start to fire ignition.

Before a True Believer[tm] says "but if you do X it won't stall", I set my idle speed as low as possible to keep from annoying the neighbors.  I'll take an occasional cold stall over being obnoxious.  If I could get it to not stall sometimes, I'd just set the idle lower until it does.

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