Just a quick question, I did some searching but couldn't find an answer. I will be running MSnS with my new turbo setup, and I already have a 02 bung for the stock sensor in my DP but I dont really want to get another one welded in as its difficult to find a place around here that can weld stainless-steel. So I was thinking, the stock ECU isnt controlling the fuel anymore, so can I remove the stock sensor entirely and just use the one already in for my wideband? Just curious as to how other MS users do this. TIA

since ur not using the stock ecu . i dont see a reason ehy u would need the stock 02 sensor

If you install the megasquirt while leaving the stock ECU in to control idle, I don't think it will be a problem. As far as I can recall the ECU only needs a couple temperatures to determine idle, so it shouldn't be a problem.

But it sounds like you are running your wideband in the rear O2 sensor spot? You should have it as close to your turbine discharge as you can, heats up quicker and maintains that heat better to ensure you are getting an accurate reading from it.

No, running the wideband from the front 02 sensor is what I want to do. Thus removing the front one entirely.

This is what I'm planning on doing when I actually get around to completing both installs... :P

I think I asked Terry about this once, he said to have another bung welded in for my wideband I think. I'm gonna be at this decision this week sometime most likely, so I would love to see if this is possible. I'm gonna check my pm's now to clarify.

I recommend adding a bung. Any shop with a mig welder can weld stainless steel. If they have steel wire in the Mig, you will need to coat the weld with high temp paint so it wont rust.


Terry

I've got a second bung too... it's worth it unless you are going to be removing the stock ECU entirely, one less CEL.

Does your wideband have a output for a narrowband o2 sensor? I used that and removed the stock o2. So my wadeband sent a signal to the msns and to the stock ecu. Make sense?

The narrowband output is still useless for preventing the CEL because the heater circuit will not be hooked up, and the stock ECU will pick right up on it.

Unfortunately, you cannot just put a certian resistor across the heater circuit, the resistance of the heater on a heated oxygen sensor changes depending on the tempature of the sensor - high tempature, high resistance, pulls less current, less heating. Low tempature, low resistance, pulls more current, more heating.

With MS though, you already have a CEL, so its not like adding one more would make that much of a difference. Couldn't you just do Corbins vfaq writeup to the front O2 and just ignore the heating element all together? Sure you would get another CEL code, but the stock ECU would still be reading stoich. right? I know I can just get another bung welded and it wouldn't be that big of a deal, but I was just curious.

Originally posted by GreenRicer
With MS though, you already have a CEL

I've been working really, really hard to find a way so that doesn't happen, mostly because I need OBD2 in order to pass inspection. I could always put the stock injectors back, tune the fuel pressure back to 43.5 static, and pop out the wastegate actuator cotter pin, but I haven't given up quite yet...

...jew can dooo it!

On top of putting resistors or leaving the stock injectors hooked up to the stock harness dangling somewhere, I was thinking maybe some kind of connection from the MS to the stock injector harness that takes a sample of whatever pulsewidth the stock ECU thinks, and have an option to use that value times whatever scalar to adjust for a different size injector. That way when the stock ECU tries to make a change it gets closed loop feedback from the stock narrowband that the change it made actually did something, hence no "injectors aren't hooked up" light.

that sounds like more work then there has to be...?
KIS* - I know the last S doesnt apply to most here.

Well, I dont have to deal with emissions yet, so I dont know how they do it. But couldn't you just use a 555 timer, cut the CEL wire and wire it into the timer, have a power wire going to your ignition, and then program the light to stay on for however many seconds. Thus: turn key- CEL comes on (just like other lights in dash display)- after 5 or 6 seconds the timer turns the light off till the next time you turn the key off and then on. You could have it in a little box, would be cake to wire up.

It doesn't work that way... inspection in my state requires the station to actually connect to the stock ECU over the OBD2 port and see what's up regardless of if there is a CEL or not. This is where a product like an "OBD2" simulator would come in handy, but such a product does not exist, and if it did, eventually somehow it would be declared illegal and sale would be prohibited.

Damn, that sucks...you should invent that OBDII simulator and keep it on the down low, make some boo-koo bucks with it too...or just move to a different state :P
But in all seriousness, thats quite a predicament, are the injector codes the only ones you cant seem to get rid of? or are there other issues too?