Halfway down the page is the chart on Flyback board requirments, not recommendationd but requirements. Since this has been discussed a great deal lately and no one seems to want to search for any info on the MS site. On the laft side click on fuel injector selection and read halfway down the page.

http://www.megasquirt.info/

Terry

Sup Turbo_Talon
After reading most of the pages of the link you set from the Megasquirt site, I should completely get what a flyback board does, and what a resistor pack does.

Basically, if you have a V2.2 MS board, you can either get a additional flyback board or get a resistor pack when using 4 low impedance fuel injectors.
But if you already have a V3.0 MS board, then nothing is needed, because the V3.0 board built-in with the flyback board, and since it's built in, the flyback board is not needed, and also you only choose to use between flyback board or resistor pack, so with V3.0 MS board, you don't need the resistor pack either.

Is what I stated above correct? (please correct me if I am just totally lost in the air)

Below is the information I pulled out from the Megasquirt site, talking about the difference because flyback and resistor pack.

THE FLYBACK BOARD:
* allows the injectors to open somewhat faster than resistors will, improve the dynamic range of the injectors (resistors added about 1.0 millisecond to the injector opening time),
* the flyback board gives the injectors 'full power' while cranking, potentially making for better starting when it is very cold or when your battery is marginal,
* the flyback board potentially allows you to minimize the current through the injectors by tuning, theoretically helping them to last longer due to lowered heating of the injector coils,
* the flyback board and components are cheaper in some cases than resistors, if bought new, depending on how many you have to use.

THE RESISTOR PACK:
* simpler,
* have no active components to fail,
* require little additional wiring, and
* have been proven in millions of mid-eighties OEM applications.

Great good job reading its important info; however, the info in that link also states clearly that when running low impedance injectors 4 or less you are operate the injectors with PWM settings for peak and hold type injectors. You are not reqd to run the flyback circuit, it is strickly OPTIONAL. When running more than 4 injectors you need to run the flyback circuit.

Board version has nothing to do with this because the v3.0 can easily be built without 4 flyback fets and be built like the v2.2.

Low impedance injectors are designed to be operated as peak and hold injectors. A resistor box just makes you operate them as saturated injectors. Do you know the difference of the two and how they operate? That is the key to understanding the design on the flyback circuit and why the flyback board runs 4 fets as opposed to 1.

Glad to see you taking the time to learn this. 50% of the people running MS now have no idea what the flyback circuit really does and why and how the injectors operate.

Terry

Now after reading what you said, and I go back to re-read the page, I am a bit confused in what you said, and what the page is trying to say.

Let use my setup to be the example (I will install the MS this weekend, tomorrow)

Ok, I just got myself a set of 680cc injectors. they are for the 4G63, so the injectors are low impedance, but I will change the o-ring for my 420A engine. and I have V3.0 MS board.

Well, about what you said, I am running 680cc low impedance injectors, so that means with the PWM setting, the injectors will be operated as peak and hold type, which is what the low impedance injectors are designed for, so it's good.

Ok, I hope I get the above correct. so I get those so far.
But now I am lost with 2 points:

1) I thought the reason we need flyback board, because of using low impedance injectors. We need to use the flyback board because the low impedance injectors drain more power, so a flyback board is needed to provide the necessary power usage. But now from what you said, it seems like unless more then 4 injectors are used, flyboard is not needed??
I do know the flyback board provide other better options, but I thought it is a MUST Required things when using low impedance injectors.

2) I don't know what is the difference between saturated and peak/hold injectors?

Thanks.

ugh just use the flyback end of discussion.

Yeah.. sorry, I was thinking about refering to this post, since we were kinda talking about it in the other post.

So, do you have time to explain or mind to point me to the area for more information about those questions?

Thanks alot!