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MS2 dwell setting


74Adam

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Hey guys, I am getting started on my megasquirt journey and will probably be asking some stupid questions so please cut me some slack. My situation is that I have a car with MS already installed and "setup" but it barely runs. I was under the impression that I would be getting a car back that was dialed in and ready to go, at which point I could learn the intricacies of MS at my own pace. As it turns out, I am going to have to figure it out myself. Maybe that's just as well. I have the megamanual and have been reading through it as well as reading a lot of old posts on here. I have tunerstudio loaded and have been playing with it for the last couple of weeks. I hooked it up to the car last week to pull the existing settings from the MS and saved it in a file so I have a reference (even if it obviously isn't a great one).

 

The car:

78 N/A 3.0 liter, mild performance build

Everything is stock except the 240SX TB

"Dumb" cold-idle valve

Fuel only (for now)

Firmware: V2.600

 

So, the guy set the dwell at 1.0ms, which seems low (acceleration compensation of 0.2ms). The megamanual says a rough range is 2-4 and I have seen many posts on here that seem to reflect that, but most people are using aftermarket coils. I'm thinking I could set it at 2.0 or even 3.0 without toasting anything. Would appreciate any thoughts.

 

thanks

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Pretty sure that "dwell" is an ignition coil charging term.  If you're running fuel only you wouldn't worry about it.

 

If you're planning to control ignition and asking for that then, somewhere out there on the interweb, and in Hoffman and Cramer's book there's talk of the finger test method.  Increase it until the ignition modules get warm, then dial it back a bit.  Or there's math yu can do with your coil's specs.

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Sorry, that really was a stupid question....lol. Sometimes you get so wrapped up in this stuff you can't see the forest for the trees.

 

Dexter, I'm sure you are right. I feel comfortable about a lot of my settings but I am struggling with the PWM stuff. My understanding is that if you have resistors in series with the low Z injectors (like the stock Z has) that you don't need it. But, you have to enter something. My settings are as follows:  injector open time-1.0ms, battery voltage correction-0.20, PWM current limit-75%, PWM time threshold-1.0ms and PWM period-100. I just re-read the megamanual on injector criteria and realized that I may need to set the time threshold to 25.4ms. Essentially, treating the injectors as if they are high Z. Do I understand that correctly? 

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Since I am running fuel only, do I need to be concerned with any of the ignition settings? Obviously, I would set the trigger wheel=0 (i.e., no trigger wheel) and I would set the rev-limiter algorithm to "none" since I have no control over that. But what about the settings under "ignition options". Do I need to worry about any of these? There is setting called "coil charging scheme". This seems relevant since "standard coil charge" is one of the choices.

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