secondary injector module/ecu
 

Continuation of the discussion from the for sale thread:

What does the secondary injector module actually do?

As determined by Marc's testing, all ECU's are interchangeable with the correct PROM. Which would lead me to believe that either the circuitry exists in both ECM's, or it's done entirely through the PROM.

One would think, that with the proper programming, a simple wiring change should be able to eliminate the secondary injector module from the car.

On another note, I have one of the DIYautotune megaquirt LT5 ECUs. When ordered, I had to specify 1990, or 1991+. They cited an internal wiring change between the two. Does anyone know if this is due to the secondary injector module? Why does the stock ECU handle both with a programming change, but the megasquirt requires internal differences to the circuitry?

Re: secondary injector module/ecu
 

The LT5 ECM and engine controls are a derivative of the L98 logic. The ECM ONLY controls the secondary injectors by energizing the secondary relays sending power to the secondary injectors. It essentially provides the ground
(-) for energizing the secondary modules. The pulsewidth for the secondary injectors is controlled or “shared” w the primary injector signal from the ECM. Once engaged, the ECM basically cuts the pulsewidth by 50% so two injectors now share the fueling needs of the motor.

So NO, a simple change would not do the same thing. The secondary module substitutes for injector drivers.

Re: secondary injector module/ecu
 

So if the ECUs are the same except for the PROM, and the 93-95 cars don’t have a secondary injector modules, it stands to reason that with a reflash and wiring change, the 90-92 cars wouldn’t need them either. Unless the 93-95 cars are doing something else.

Re: secondary injector module/ecu
 

Where do u get the idea that 93-95 LT5s don’t use secondary injector relays?

Re: secondary injector module/ecu
 

Yep the secondary injector relays are located on the passenger rear in the later model years. To be honest I forget that as well Dom.

Re: secondary injector module/ecu
 

The secondary injector modules are present in all ZR-1 s from MY 90-95. They simply moved in the later years to the rear passenger side. This makes sense why the ECM are all backwards compatible because they still have these secondary injector modules. I think they are the same the entire model run with the exception of the first 200 MY 90s for some reason.

Re: secondary injector module/ecu
 

In the very first post that I quoted in the thread that was edited 10 minutes ago. I guess that clears that up. I assume the injector impedance changed between 92 and 93?

So on to the second part of my post. What is the internal difference in the DIYautotune ECU? They listed the year cutoff at 1991 and up.

Re: secondary injector module/ecu
 

You’ll need to ask MegaSquirt. I was not aware that MS used 16 injector drivers or do they just replicate the LT5 ECM? I have no idea why a 92 would be different than a 91.

Are you saying the injector impedence changed in 93 or that is what must have happened IF the modules had been eliminated?

Re: secondary injector module/ecu
 

My best guess for 1990 to 91-95 variation has to do with the power key and how it works..

Re: secondary injector module/ecu
 

:happy1:

Re: secondary injector module/ecu
 

It's been low on the list, but I will have to email them at some point.

If the modules changed and aren't interchangeable, I'd guess it's because the injector impedance changed.

Interesting. Could be. I know with the megasquirt the power key becomes basically a programmable input. Maybe it's just based on wiring differences in the switch circuitry.

Re: secondary injector module/ecu
 

Apparently all injectors are interchangeable, so impedance is all the same.

Re: secondary injector module/ecu
 

Has to be. Key on and off switch vs. the Module. Maybe resolved at the chipset with key always on option. GC

Re: secondary injector module/ecu
 

I also believe Megasquirt still uses the Secondary modules.. that ECm was designed to be Plug and Pray (Err I mean PLay)

Re: secondary injector module/ecu
 

😂😂😂😂 Yeah but it doesn’t like to play w the CCM.

Re: secondary injector module/ecu
 

I had mine out of the box once, put it on my 91 and it had a very long crank time until it started and ran like crap. Haven't fooled with it since.

In what aspect? To the best of my knowledge, the only things they hadn't worked out were the trip computer/mpg stuff.

Re: secondary injector module/ecu
 

yes Spork, that and the last email said other stuff would glitch and then come back to normal.

I first pinged them in May of 2016.. 2 years ago, the issues have not been resolved and the unit is not anywhere for sale.. it is unfortunate, I would like to see a solution for our cars.. The guy that bought the 94 barn find needs a DIS.. so some of those specific modules are our Achilles Heal

Re: secondary injector module/ecu
 

They don't have access to the info needed to fix the ccm issues and likely never will, nor will it be worthwhile to invest the time due to the low demand.

I believe these are for sale any time, you just may have to wait until they get a couple orders before they build. I know when mine was built they had 2 or 3 orders. I ordered mine in March of 2016. Took about 2 months to get, with some communication issues along the way.

I hope to get it up and running this summer.

Re: secondary injector module/ecu
 

The wiring pinout is different between 90 and later years for both the power key (as mentioned), including the power key lamp, and the knock sensor. Later years also had EGR, but I doubt anyone running the MS would care about EGR.

Re: secondary injector module/ecu
 

Oh yeah forgot about the knock sensor.. all the above are easy enough to change

Re: secondary injector module/ecu
 

Then how are the ECM's interchangeable as per Marc?

Re: secondary injector module/ecu
 

Because the OEM ECMs have enough inputs and outputs..

So the PROM then Defines the ECM's inputs and outputs.

if you mapped it out the Power key, knock and EGR use pins that are unused on the 1990..

Functionality was there in the ECMs, just not used

Re: secondary injector module/ecu
 

So one would think that would be even easier on the megasquirt ecu. Which begs the question, what is different on their ecu between cutoff. I sent them an email.

Re: secondary injector module/ecu
 

Torqhead out of Canada has the CCM data stream figured out for L-98, but they don't have the engine control for LT-5 secondary injector control done (low demand). I've been trying to get MS to talk to Torqhead so that "they" can solve the CCM issues. Have not had any success so far.

Sent from my QTAIR7 using ZR-1 Net Registry mobile app

Re: secondary injector module/ecu
 

That would be awesome.