-
We've upgraded and reskinned the forum. Notice something off? Email us at [email protected] and we'll fix it.
V1 Mikes Extended, Full Frame Goblin - 2009 Cobalt LS with 135k donor
- mike_sno Goblin Guru
I was hoping you had some internals about why GM decided the way they did. Anyway, My guess would be efficiency, emission, performance and commercial. Some of those are contradictory targets.
I think we are not talking about the same thing here. My comment that this all is overrated came from a posting which pointed to a question how accurate wideband O2 sensors are. Which raised another question in why there are narrowband in the first place. The best thing I have found so far on how the O2 sensors really work is on wikipedia. Conclusion is, that my statement above was wrong and there is a technical difference between a narrow band (Zirconia or Titanium Oxgen sensor ) and a Wide Band sensor, which maintains still a secret so far.
Anyway, if there is no change in the way the ECU controls the engine, tuning will only shift the tolerance band to the target you want it to be. E.G. More performance, longer engine life, lower emissions, different fuel,... or a combination of those. With change, I mean moving away from just narrowband to wideband reading of the O2 level in the exhaust. (Open Loop to closed Loop operation). The LSI can run closed loop only at around lambda 1 due to the narrowband sensor. Which is probably the operation where the engine runns 99% of the time. Under the WOT and other conditions we run open loop. Means, the OEM or you or a tuner or whoever sets the parameters to get the wanted lamda value. With all the variables invloved this is becoming a very very complex problem. I just mentioned the soot on the O2 sensor, but there are many more factors which all have certain tolerances. Reducing the individual tolerances of the wideband sensor for example will certainly help, but how big is the overall influence of the complete system? I haven't seen a data sheets what tolerance a wideband has.
- Gtstorey Goblin Guru
If you will ask one or two questions at a time I will answer what I can. I’m struggling to figure out what is a question and what is a comment on your part.
I don’t know why GM does it this way. May just be that early on it worked and they have never seen a reason to change it.
Beyond that, I don’t know if you think you can get a GM ECM to use wideband feed back, but as far as I’m concerned, not very well. Yes you can force it to run open loop, but I don’t think any advantage outweighs the disadvantages. And even then it wouldn’t be using the wideband.
I don’t know why GM does it this way. May just be that early on it worked and they have never seen a reason to change it.
Beyond that, I don’t know if you think you can get a GM ECM to use wideband feed back, but as far as I’m concerned, not very well. Yes you can force it to run open loop, but I don’t think any advantage outweighs the disadvantages. And even then it wouldn’t be using the wideband.
- mike_sno Goblin Guru
Yeah, I agree. I have to many things going on at the same time. Alignment, Cruise Control and Tuning.
My question is opposite of what you just said. Can the ECU been forces to run only closed loop. Obviousley if you want to have things like power enrichment, this will most likely not work with a narrow band sensor. ( If I see this graph, it makes me wonder how wide the narrow band readings are accurate https://en.wikipedia.org/wiki/File:02-sensor-vs-Voltage.jpg ) In my understanding we run power enrichment open loop, because the narrow band can not pick it up. (and myabe even if we could, the ECU would not be programmed in a way to work with it.)
One thing which is most concerning is the way the ECU reads the Analog input. If it is fixed to read a certain voltage E.g. 0.45V and tries to get the engine as close as possible to this reading, there would be no way without more electronic involved to get this done.
The way I see it: Speed density or Volumetric efficencie cover for shortfallings of the air volumne flowing in. Power Enrichment covers for the narrow band limitations. IMO All of those are software tricks to cover unsufficient sensor data.
If the engine is just controlled with one table and this table has RPM vs MAP and in the cells the desired lamda value, would that cover all operation secenarios of the engine? WOT would mean high MAP, cruising would be lower MAP and casting would be lowest MAP.
Now, the problem is, that the ECU will only look for: Above or below (example) 0.45V. Well it would not be to difficult to create something like a translator between the O2 Sensor and the ECU Input. Which has it's own table and can translate a desired lamda at a given MAP and RPM to 0.45V.
I hope you can follow me....
There are many things I do not know! I am by trade not an engine tuner. I made some HPacademey classes and understand quite a bit in close loop (PID) regulations of industrial applications and programming. Lot's of engine tuning knowledge came from unverified sources like HP Tuners forum, Youtube, websites, but have no scientific proof behind it.
I believe the LNF has a wideband sensor. Would be intersting to know if that engine is more in close loop operation as the LSJ.
- Gtstorey Goblin Guru
Pick a question and ask it.
I will say if you want to be able to tune like you want to tune get an aftermarket fuel injection system. If you are sticking with the stock ECM, just tune it like it is designed. It might not be as “elegant” as you would like.
And don’t forget there are many tables in a ECM that you can’t control or even see.
I will say if you want to be able to tune like you want to tune get an aftermarket fuel injection system. If you are sticking with the stock ECM, just tune it like it is designed. It might not be as “elegant” as you would like.
And don’t forget there are many tables in a ECM that you can’t control or even see.
Rauq
Goblin Guru
- Rauq Goblin Guru
V1 - Wiring Wideband O2 Sensors
This has been a popular topic recently, so I'll attempt to write something up that can be referenced rather than adding information piecemeal in response to various questions. What is an O2 (oxygen) sensor? Spark ignition engines must inject a precise amount of fuel based on how much air enters...
The LSJ uses narrowband O2 sensors because that was standard technology at the time. It was good enough to meet power and emissions targets on a port fuel injected engine making 50hp/cylinder. The closed loop strategy is, if the O2 sensor is reading lean, add fuel. If it's reading rich, take away fuel. The ECU knows fueling is where it needs to be when it evenly switches between reading rich and lean. There's no concept of being perfect; in fact, maintaining perfect stoichiometric AFR would result in a check engine light for insufficient switching.
The LNF and most (or maybe just many) direct injected engines use wideband O2 sensors because they have much tighter control of fueling. Just the nature of port vs direct fuel injection. I'm sure folks running LNF engines can ask why GM put in all the effort to engineer an engine control strategy that doesn't add power when power adding parts are installed. The ECU is programmed to make X power, and if you install a free-er flowing intake or exhaust, the engine just goes "ok I can make the same power with less effort now so let's stick with making the same power." Tuning for power is obviously a little more complicated than telling the ECU to make more power, but for the sake of this comparison I think the example works.
- Gtstorey Goblin Guru
It looks like GM only within the very recent past started using widebands other than the LNF and its derivatives. 2019 Camaro SS (DI-LT1) still used narrowbands. 8th gen Corvette and 6th Gen Camaro 4 cylinder Turbo uses wideband. If Autozone listing of wideband or narrowband is correct.
- mike_sno Goblin Guru
Anyone know what kind of tool I need to remove the blue screws?Here is the pulley. I measured the cirumference as 239mm/pi = 76.1mm. I measured with my caliper 75.9. I am sure the caliper is more accurate. and Pi works
View attachment 44658
I found
Torq-set
Mortorq
Similar threads
