Recently got the car running, it's a '90 motor with a very large streetport running stock injectors and an '85 distributor for ignition. Idles fine, revs fine with no load, and AF's are fine up until ~3500rpm where it spikes to 20:1 AF.

It's a Megasquirt 2.2, just the base firmware using Megatune 2.25, no O2 sensor (sniffer in tailpipe on the dyno). I've included screenshots of the relevant settings below; do I need to run the MSnS Extra firmware even though I am using a distributor for ignition?

 

two words
"STAGED INJECTION"
I think you may be running out of fuel up top because secondaries may not be comming online like they should
msns-e has the staged injection function. It really is very simple to upload into the ms. Just like loading the standard software.

dpf22

 

That was my thought too; but shouldn't the current setup just fire all 4 injectors simultaneously? I have tried setting to "4" injectors.

 

that doesn't matter.. what matters is how you have it wired....

If you don't have all 4 injectors wired up, it won't be squirting on all 4.

 

Hi Ken,

It is wired per this diagram:



I will try upgrading to the msns-extra firmware with the staged injection function around 3000rpm and see if that helps, although I am still confused as to why I wouldn't have enough fuel with all 4 injectors firing all the time!

 

hmmmm, perhapse I jumped too early on the staged thing, however, do double check your wiring. Sometimes you miss something when you don't "physically" double check the wires for shorts/breaks. I used my stock harness with an intermediate connector and had this happen. What would I do without my multimeter lol.
Also a thought is you may be running too rich causing a missfire condition which looks lean on an o2 sensor. but You didn't elaborate on how it was acting when it leaned out.

dpf22

 

so it looks like you're squirting all four injectors at once...

If that's the case, you shouldn't be running out of fuel.

I would check the wiring if I were you... If you have it hooked up this way and are not running staged injection or dual table, then it should run pretty crappy on idle, etc... since the secondaries will basically be spraying into dead air...

Since it's not running crappy until you rev it up a bit, I think your secondaries aren't squirting.

I would also suggest getting msns-extra, and using the staged injection feature.

Ken

 

Thanks for the help. I successfully upgraded the firmware to msns-extra 029t, but now I can barely get the car to start using the same set of parameters I had used on the basic MS1 firmware; the times I can get it to start it idles horribly and sounds as if its only running on 1 rotor! Ignition is handled separately by the distributor.

I'd also like clarity on one thing; I've read around on this but can't seem to answer my own question - if Injectors is set to "2", as in your FAQ Ken, does that only fire the primaries until the staged injection function kicks in at the set RPM? Does changing Injectors to "4" turn them all on, all the time?

I've attached the MSQ, any help is appreciated!!

 

what it does is it fires the primaries simultaneously till the secondaries kick in when you have your settings set to transition. The settings are in the "advanced" menu on megatune.
Just noticing you have a large street port. I still think you were choking the motor with fuel. However, I would probably go to the megasquirt.info forums and get a program called megalog viewer. it shows you in real time when dataloging what is happening. Even with a narrow band o2 it should show you how the engine is running. This was very helpful for me. If you are choking the engine with fuel, you will see very jagged spikes on the o2 line. If you are too lean, it will just be around .6v or lower. However this is just a suggestion as it worked for me.

dpf22

 

it might only be firing on one rotor if you wired a primary and secondary to channel one instead of both primaries.

 

Will double check, but I'm 99% certain the primaries are wired as 1&2, with the secondaries as 3&4. Wired that way, selecting # of Injectors "2" in the Constants 1 page is selecting the #1 & 2 (primary) injectors only, correct? Channel 2 (Injectors 3 & 4) are not affected by this Constant page (or the VE Table 1) at all when Injectors = 2, right?