In reply to alfadriver :
I have had bad sensor drift issues any time the engine sucks oil, which is a thing that can happen. Then it will read, say, 17:1 even when it is rich, for example.
It will also read either minimum or maximum when it is warming up, which is a thing that it will do any time the voltage drops below 12v. Like, for instance, idling with the headlights and fan on.
In reply to Knurled. :
Neither of those problems are due to the sensor nor it's set up. Well, the second one can be traced to crappy power systems.
The lesson- don't burn oil, and power it correctly.
BTW, if you wait until you get 17:1 when it's rich, I'd suggest you look at it sooner.
In reply to alfadriver :
It's easy to say "it it hurts when you do that, then don't do that", but the point is, it's not smart enough to send an error message when there is a fault.
When the sensor stuffs up on the XFI (due to leaded fuel contamination, usually) the system is smart enough to ignore the O2 and run in open loop.
The 17:1 example happens pretty much instantly. O2 sensors do not like having liquid oil dumped at them when hot.
In reply to Knurled. :
If you are looking for reasons to not run closed loop whenever the sensor is good, it's your car. I would, personally, run it 100% of the time. I've not actually seen the problems you have seen, in the many hours and many cars I've worked on over time, so while I appreciate that it could be an issue, it's not really something I would worry about.
Especially the reaction to 17:1 would be to go richer, which is pretty safe. You would hit the rich limit and it would misfire, but that would not harm the engine all that much.
Given the choice of having a sensor or not, I'll take the sensor.
In reply to alfadriver :
You asked for a reason, I gave one. 
I did say the majority of people would have no problem...
Knurled. said:In reply to Paul_VR6 :
Given that the engines I generally play with are insensitive to tuning (with respect to finding enough pieces to glue back together and make an engine again) my main concern with tuning is to get it running as lean as possible without stumbling, because the generally high exhaust residuals mean you need a rich mixture for reliable combustion, and this results in lots of fuel dilution of the oil. The leaner I can get it to run, the less often I have to change the oil. Right now it's about 800-1000mi before the oil has gone from a quart underfull to a quart overfull and the 20W50 is a runny, stinky mess.
So, really, what I'd like is a mixture adjustment knob so I could pull fuel while on the highway until it just starts to stumble, and then add a little back. Could probably do this fairly easily, come to think of it, by telling MS that the trim pot returning a signal from 5vref is actually a 0-5v ethanol content sensor. (I'm on MS2/Extra, I don't think map switching/blending is something I can play with)
I am sure there is a way to do this, but how to implement it in MS2 may be tricky. Your idea using a trim pot for some "flex fuel" behavior could use useful for determining AFR targets, but IMHO that would be easy enough if you can get someone to drive and change AFR to determine your targets across the map. I have some generic ones I use for different engines, but as you've mentioned exhaust dilution, you either have very high backpressure and/or large overlap that leads to charge dilution. I would think at cruise this wouldn't be an issue, but I don't know the circumstance.
Knurled. said:In reply to alfadriver :
You asked for a reason, I gave one.
I did say the majority of people would have no problem...
So we should amend this: If you have a car that's functioning correctly, then closed loop is superior to open loop control.
goingnowherefast said:Knurled. said:In reply to alfadriver :
You asked for a reason, I gave one.
I did say the majority of people would have no problem...
So we should amend this: If you have a car that's functioning correctly, then closed loop is superior to open loop control.
If I had the money for a dry sump, I wouldn't be running MS. And Mazda's factory race teams' solution was a dry sump and a way to change the oil during pit stops. Sealing compression and oil against a flat surface is... tricky. And greatly imperfect.
Subarus and reverse rotation Hondas are also good for occasionally drinking half a quart of oil when on course. Now that I have some form of datalogging, it's fun to see how far it goes. On this last event I was seeing sustained .7-.8g with spikes to 1.8g.
Waaaait is this for a rotary? If so all conventional wisdom goes out the door and just keep pouring fuel in until it explodes. That is all I have seen people do (in the import drag racing world at least) so it must be gospel.
I didn't realize AEM made this, but it's what OP was looking for.
CAN LSU4.9 with no gauge. Bang.
Alfa - I too like the idea of running closed loop all the time, I was just told not to when I first started getting into tuning and haven't questioned it since. Since I'm running speed density and don't have an external baro pressure sensor, my fueling gets really off when I leave home for the mountains. Some closed loop correction for that in boost would be nice.
In reply to morello159 :
Gah, that thing would be perfect to stick on my old 911 if only it had a simulated narrowband output.
morello159 said:I didn't realize AEM made this, but it's what OP was looking for.
CAN LSU4.9 with no gauge. Bang.
Alfa - I too like the idea of running closed loop all the time, I was just told not to when I first started getting into tuning and haven't questioned it since. Since I'm running speed density and don't have an external baro pressure sensor, my fueling gets really off when I leave home for the mountains. Some closed loop correction for that in boost would be nice.
See also this Ecotron solution, it uses a Bosch controller. You do have to pick one output (analog 0-5V, CAN, etc.)
In reply to BoxheadTim :
Add barometric correction to your MS and the problem should get better.
and to the part about not running closed loop while tuning was to simplify things while getting the initial tune sorted, this was more to help the squidgy organic bit not get frustrated/confused.
Once the majority of the tuning was done you should run closed loop to keep things from going too far astray.
morello159 said:I didn't realize AEM made this, but it's what OP was looking for.
CAN LSU4.9 with no gauge. Bang.
Alfa - I too like the idea of running closed loop all the time, I was just told not to when I first started getting into tuning and haven't questioned it since. Since I'm running speed density and don't have an external baro pressure sensor, my fueling gets really off when I leave home for the mountains. Some closed loop correction for that in boost would be nice.
Sometimes, "common sense" makes no sense to me at all. Running speed density w/o BP isn't a reason to not run closed loop. We do that all the time. Then again, if MS just used the MAP sensor before cranking, you get a pretty darned good BP signal- but you really don't need to compensate it much. The BP issue tends to be a bigger one for MAF and how the load (aka spark) calculation happens.
Turn it on, leave it on, and be happy. Well, after your desired a/f table is what you want it to be....
In reply to alfadriver :
It does get BP before cranking, but when I drive 4000ft up into the mountains, that initial reading is no longer valid. I was arguing for closed loop, not against. We're on the same page :)
In reply to Stefan :
No MS on the 911 yet, I'm stil trying to track down the underlying issue before making drastic changes. The O2 sensor on these can be a known issue, and I was thinking about replacing it with a wideband as an additional diagnostic tool. But to feed the chipped stock ECU I still need a working narrowband output.
Most widebands will also have a narrowband output.
In reply to GPz11 :
Most do, but it looks like the AEM that was linked above doesn't. That's what my comment was referring to.
GPz11 said:Most widebands will also have a narrowband output.
Make sure it's a true emulation of a narrowband output and not an almost-linear 5v wideband signal scaled to be a 1v signal. Narrowbands are more of a switch.
The ONE(?) good thing about the Innovate is that it's narrowband sim output seemed to always work very well.
Depending on how creative you're feeling, converting the analog wideband signal to narrowband wouldn't be too difficult.
In reply to morello159 :
While that's a pretty cool project, the concern that I'd have is that I get to debug the project _and_ the Porsche, when I'm already trying to debug the Porsche.
Yeah, might be easier to simply weld a second bung on the exhaust ;)
In reply to Keith Tanner :
Well, the other header would really benefit from an O2 sensor as the current one is only monitoring one bank. If I could TIG weld there'd already be one on there (the header is stainless steel).
Of course that still wouldn't tell me if the existing sensor has decided on early retirement or not 
.
Paul_VR6 said:The ONE(?) good thing about the Innovate is that it's narrowband sim output seemed to always work very well.
Two good things: There was an auxiliary output that you could program to act like a narrowband sensor... at ANY ratio. Say 13:1 for instance.
So if you're playing with old K-jet stuff, you run both of those outputs through the 87 and 87a terminals of a relay, send the signal through the 30 terminal to the O2 input of the computer, and use the WOT switch to control the relay instead of going to the computer. End result, you run closed loop all the time, 14.7 at cruise and whatever you program the Innovate to switch at when at WOT.
Just in time for people to by and large not play with K jet anymore.
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