Goin' Megasquirt (My progress thread)

[Lex]

I recommend switching the stock setup and attaching cylinders 1,4 and 2,3 together on the respective MS injector drivers.

[FE3-323]

i remeber hearing about this lex, refresh me tho, why was this better?

[therieldeal]

it definately works better, i made this change when i switched from 360cc's to 550cc's, and instantly the car idled better (even with the very small idle pulse due to the 550's). it has something to do with how MS doesnt really have any idea which cylinder is firing at any given time, but i'm sure Lex could better explain it.

[photoeye0]

i noticed you didnt put down how to pair the injectors

its
yellow 1-3 to injector 1 on the ms 32-33
yellow/black 2-4 to injector 2 on the ms 34-35

ok one more tip

becuase there are several ground pins and most wire kits come with large ground wire take some smaller wire and cut them to equale lenth then attach them to the pins on the oposite side i usualy attach 3 wires to one heavy grond wire.

it will fit nice and create an even ground.

I put 1-4 and 2-3 on togther cuz that is how Lex did it in his wirte up... He said it help some of his idle issues. Was I wrong to do it that way?

And I will use your ground tip thanks.

[therieldeal]

i am running the way Lex suggested, with no problems. like i said, it idles smoother this way.

[photoeye0]

Than it's stayin the way I have it.

I should have some up date pix soon too.

[Lex]

It has to do with the start of injection. The MS will start injection on the first ignition pulse it receives - so it will inject at different times in the engine cycle depending on how the engine is oriented when it was shut down.

There is an optimal configuration of injecting during the cycle and you are closer to that optimal configuration if you tie the cylinders that are at TDC at the same time together.

If you tie 1,4 and 2,3 together you will always inject when one bank will be in the (power, intake) stroke and the other bank will be in the (compression, exhaust) stroke.

If you leave it as stock, you can have different combinations of when injection happens relative to engine timing and some work worse than others.

[jacobrussell]

direct from the mega squirt manual


if you have idle issues its probably due to one of two things

tuning

or

you wired your injector wires backwards at the MS

[Lex]

What I was talking about is more subtle than this Jacob, and that diagram is generic. It doesn't say which cylinder inj 1-4 are on.

[jacobrussell]

maybe you guys should try simultaneous fire?

i will not suggest changing the stock set up but its so simple any one who gets a ms from me can change the wires in a matter of minutes so do what you want i know i had no problems with stock and large injectors

[therieldeal]

simultaneous fire with 550's? thats gonna be one hella short idle pulsewidth...

[jacobrussell]

ok after a lot of research i have this to say about injector pairing..

you might get a smooth idle changing the pairing but

you loose out on the cooling effect of the fuel on the wasted cylinder

[FE3-323]

coolilng effect, or pushing raw fuel out the exhaust which does which?

[Lex]

ok after a lot of research i have this to say about injector pairing..

you might get a smooth idle changing the pairing but

you loose out on the cooling effect of the fuel on the wasted cylinder

What wasted cylinder? The fuel sits on the back of the intake valves until they open and fuel is sucked in. There is no wasted fuel or wasted cylinder in this regard.

[jacobrussell]

your right about the ms wiring diagram its wrong i miss read it

but I'm wiring my new setup to stock i made 350whp and got 35 mpg with the same wiring and wasted spark before and a smooth idle with out using Fidle control.