Hello
I'm building a 13b with pro jay throttle bodie and megasquirt. Now my question is does the ms3x expansion handle low z injektors on the same way as the v3 board or do i need ballast resistors. where could i buy 40 watt 3.3 Ohm resistors like Ohmite in europe.

Dirk

 

No, the MS3X can not handle low-impedance injectors. You will need to hook up a 10ohm 10 watt (or more) resistor inline for each injector.

http://msextra.com/doc/ms3/fuel.html#impedance

http://msextra.com/doc/index.html#ms3 Gives you more information on the MS3 and MS3X.

 

You can also use an external peak and hold board such as jbperf's peak and hold board.

Ken

 

Thank you very much

 

You may be able to use the stock resistor pac from the 2gen NA engine. Anyone know if this would work.

 

It would work, but peak and hold is better, it can yield smaller dead-time.

Ken

 

Ya, here is the thread talking about resistors vs P+H driver. Basically resistors require 15% more fuel to obtain the same AFR. Also the dead time differences like he said.
https://www.rx7club.com/single-turbo...k-hold-666741/

Also a guy posted in that thread this \/ which caused me to find this thread...

"The megasquirt (MSnS-E) has the capability to run peak-and-hold without a second box. Its done by adjusting the opening time and PW % variables in the "Basic Constants 1" menu, so you shoudlnt need to do anything else to it (assuming its working now)"

What is he talking about? MSnS-E?

 

I don't know what that thread says, but resistors won't require more fuel, just more pulse-width. It'll take longer to actually open the injector, so the amount of fuel injected will be the same.

MSnS-E is MS1/extra. It's the "extra" firmware for the MS1. The MSv3 main board has 2 injector outputs on it that are capable of driving batch injection on low or high impedance injectors. For low impedance, they have settings you can set to limit the current to the injectors during the "hold" portion of the pulse, and to limit the "peak" time.

The ms3x does not have the proper flyback circuitry to drive low impedance injectors.

Ken

 

Ya, by fuel I did mean more pulse width. Basically removes 15 percent of your max fuel output though.
Thank you for clearing up which models do low and which can only do hi.
I wish that ms3x would run lows :/
P+H box here I come.

 

I'm not sure if this is helpful, but I just use Injector Dynamics injectors which are high impedance...

they make injectors going up to 2225cc, and fit stock (FC) fuel rails.

 

Ya the injector dynamics is the best choice. The price is what throws me off though. Mostly considering I got a set of lo injectors. An FJO box usually turns up used for near $175, making going that route quite affordable compared to dropping $450 on a set of injectors.

 

DIYautotune is working on a peak and hold board for the ms3x, but there still testing so there is no info on it yet. They told me hopefully spring time.

 

ook, I like that idea, where'd you hear that.