411 PCM with 2 bar enhancement......blended MAF and SD operation......possible?

[slarsen47]

I have been running a procharged 2002 Camaro in straight SD no issue (MAF and O2 sensors are still installed, but presumably have no effect on anything).

Because the MAF and O2 sensors are still installed in the car, I have been researching enabling the MAF for normal street driving and the PCM disabling the MAF when going into boost.

From what I have read (maybe my lack of understanding) it is not possible to do this with a 411 PCM. Can someone confirm that this is true?

If the PCM cannot be made to switch modes, one option would be to edit the tune file to use the MAF in daily driving and then edit out the MAF at the race track??

Has anyone done this? Is it even practical to do so?

If there is no great advantage to a dual MAF and SD tune, is there any reason to keep the MAF and O2 sensors installed?

The MAF restricts the intake and the O2's use electricity..............



Also, just got my 98 Camaro LQ4/4L80e driving and going down this same path (Huron kit waiting to go in after working out any bugs and basic n/a tune).

Also 411 PCM and running SD only at the moment.

From the comments below sounds like it is good that I left the O2 harnesses in place and so easy enough to put the factory O2 sensors back in.

[gametech]

You seem to be misunderstanding some things. The o2 sensors are used for closed loop operation. This has nothing to do with whether you are running SD, MAF, or blended. And the 2bar OS can use the MAF, but not in the way you want it to. The factory computer can be made to run MAF only above a set rpm, but cannot be made to disable the MAF above a certain rpm or MAP value.

[blindsquirrel]

Don't bother with a MAF. They are not magic, the only thing it can do is make it run either exactly the same, or make it run worse.

[slarsen47]

I do understand that the factory O2 sensors are for closed loop.

It just seemed like a good idea (if it was possible) to run MAF/closed loop for daily driving and then SD/open loop for WOT, boost and racing.

If the consensus is to just run SD, then no point having the MAF and O2 sensors installed.

[blindsquirrel]

The MAF and the O2s are unrelated. Closed loop speed density with no MAF is real. It works just fine.

Please explain what you think you'll gain from using a MAF for 'daily driving'. It doesn't give you better mileage, better driveability, smoother ride, whatever. It does none of that.

[twenglish1]

Ive never seen any real benefit of using MAF only, especially with major vehicle modifications, closed loop speed density for part throttle driving, and it will switch to open loop speed density and run the power/boost enrichment routines when you mash the pedal

[Alvin]

Read the help file too. Some of those custom os's do away with the possibility of using a MAF.

Back up what others said. SD has nothing to do with closed or open loop. Many Dodge and Honda are factory speed density closed loop.

Speed density will do great on this.

[slarsen47]

I am almost embarrassed to admit that I thought SD was open loop only!!

Physically deleting the MAF is no problem, I would rather not have this device in my inlet plumbing.

My tune file under engine > oxygen sensors.......has the "closed loop enable" set to 284 degrees and the LTFT disabled.

Should I be running SD closed loop to get VE table fueling corrections based on factory style O2 sensors feedback?

[slarsen47]

Ive never seen any real benefit of using MAF only, especially with major vehicle modifications, closed loop speed density for part throttle driving, and it will switch to open loop speed density and run the power/boost enrichment routines when you mash the pedal

I can re-enable closed loop because the sensors are still installed in the exhaust system.

I like the idea of closed loop for part throttle driving..............I failed to understand that it did NOT need the MAF to do this.

How and why does the PCM switch to open loop when you mash the pedal?

[GBull]

I can re-enable closed loop because the sensors are still installed in the exhaust system.

I like the idea of closed loop for part throttle driving..............I failed to understand that it did NOT need the MAF to do this.

How and why does the PCM switch to open loop when you mash the pedal?

You command open loop by how your PE enrichment is set to come on. "SD only" works really well but unless you get a "Custom OS SD only" you will restricted to the low octane spark table. This means no knock learn reducing timing.

These operating systems can be found under the OS tab in your VCM editor.

[slarsen47]

You command open loop by how your PE enrichment is set to come on. "SD only" works really well but unless you get a "Custom OS SD only" you will restricted to the low octane spark table. This means no knock learn reducing timing.

These operating systems can be found under the OS tab in your VCM editor.

The 2002 Camaro PCM was 12212156 and became 1253002 with SD 2 bar RTT. This is the original PCM.

Similarly the PCM OS in the 98 Camaro was 12212156 and became 1253002 with SD 2 bar RTT enhancement. This PCM was in a 2001 2500 chevy truck. It now states it is a 2002 Camaro as per edit details.

[blindsquirrel]

12212156 didn't exist until 2002, no way was that the stock OS in any 1998 anything. That may have been what it was by the time you found it and after it'd been messed with and the PCM swapped by somebody before you got there, but it didn't leave the factory like that.

[slarsen47]

I never said it was stock on the 1998. The stock 98 PCM was replaced by ME..........nobody else messed with it.

The 1998 was a roller..............no drivetrain, stock 98 PCM and harness.

I explained that the NEW 1998 Camaro PCM came out of a 2001 truck and that the 2002 Camaro tune/OS was written onto this PCM.

Along with the 4L80e segment swap and 2 bar enhancement.


My point of starting this thread was to try to understand how I can use the stock O2 sensors to enhance low speed operation.

Partly because I still had the MAF and O2 sensors still installed on the 2002 Camaro (D1SC) but disabled SD open loop only.

I have learned through comments on this thread that the MAF is not needed and that Speed Density can be used with closed loop. I was under the wrong impression that SD was open loop only.

Having learned this fact...............I will install and connect my factory O2 sensors on the 1998 Camaro as well which is currently SD open loop only (naturally aspirated at moment, turbo kit to be installed after satisfactory n/a operation).

What I need to learn is how the O2 sensors work with SD closed loop and how the PCM goes open loop when using a lot of throttle including boost.

[blindsquirrel]

It goes open loop when power enrich activates. Narrowband O2s by definition are only useful right around stoich, and in PE it's richer than stoich so the O2s are ignored then, and it runs completely off only what you have put in the VE (or MAF table). You can log this in the scanner. 'Fuel System #1 Status': OL - Not Ready, CL - Normal, OL - Accel/Decel, or OL - Fault.

You're still using some really weird language to talk about this stuff.

[slarsen47]

It goes open loop when power enrich activates. Narrowband O2s by definition are only useful right around stoich, and in PE it's richer than stoich so the O2s are ignored then, and it runs completely off only what you have put in the VE (or MAF table). You can log this in the scanner. 'Fuel System #1 Status': OL - Not Ready, CL - Normal, OL - Accel/Decel, or OL - Fault.

You're still using some really weird language to talk about this stuff.

Thank you...................any "weird" language on my part is a reflection of my lack of understanding of many aspects of tuning.

I have learned a lot but obviously have a long way to go.

So basically if my 2002 car idles and runs fine open loop there is no real reason or benefit to enable the narrow band O2's in closed loop??

[twenglish1]

Should always keep closed loop with narrowband sensors enabled for a street vehicle, as it will actively make fueling corrections based on changing environmental conditions, it is important for fueling to be accurate

[slarsen47]

Should always keep closed loop with narrowband sensors enabled for a street vehicle, as it will actively make fueling corrections based on changing environmental conditions, it is important for fueling to be accurate

Sounds reasonable.

Going to re-enable and see if I can detect any difference.

[abc]

Sounds reasonable.

Going to re-enable and see if I can detect any difference.

Oh boy, your gonna detect a difference and it probably won't be a good one, until it's tuned of course. We haven't seen a .HPT and .HPL file correct? It can and will likely run better with the PCM controlling most everything below PE but it will take tuning to get it done.

Another side note, if your NBO2's have been in the exhaust and not plugged in, they are likely junk, buy two new, top quality, and start over.

[Alvin]

The question if it will run better in open or closed loop depends entirely on the setup. The Cam will be the biggest factor here.

There gets to be a point where no matter what you do the stock o2's/fuel trims will not work.

[gametech]

The question if it will run better in open or closed loop depends entirely on the setup. The Cam will be the biggest factor here.

There gets to be a point where no matter what you do the stock o2's/fuel trims will not work.

Very true, but unless it is an all out race build, I have no idea why someone would put a cam big enough to cause that problem in a boosted application.