Help me understand SD Tunes better

[gpr]

I just purchased a 2002 camaro which has some mild mods done including a cam. The car is tuned horribly and i am thinking about starting from a stock tune and removing the MAF to use a speed density tune. I have read the tutorial and understand how to get the custom os installed, but wondering how exactly SD tunes work.

What are the benefits? Is it simplicity? My previous efi tuning experience is all SD since there wasn't mafs on the engines.

Also SD mode what is the main fueling table used? Is this table more of a standard at xxx rpm and xx tps give this amount of fuel? Then you have all the other tables that affect this base table such as engine temp, map etc..

Is it frowned upon, because of complexity, to use the 3 bar os with a stock map sensor? I will eventually be building a supercharger kit but would like to tune and get familiar with the 3 bar tuning os. Then when i add a 3 bar map i will know how to use and tune with it.

Anyone can break down a bit more how SD works i'd appreciate it.

thanks

[ScarabEpic22]

If all it has is a heads/cam, leave the MAF on and tune it that way. Start from a stock 2002 Camaro OS and work from there, should be MUCH easier. Check out the Calc.VET and Calc.MAFT tutorials in this section, all you need is a wideband and a mechanically sound engine to get your tune dialed in in a few runs.

If your plan is to eventually go supercharged, get your current tune dialed in. Then upgrade to a 2 Bar MAP (no dont try to use a stock one on a boosted engine), a COS, this would be the time to ditch the MAF (but only if you outflow the 512 g/s limit it has, otherwise leave it in).

[gpr]

Okay, how about for discussions sake, could some with SD experience describe how it actually works? The tutorials and such that i have read explain how to install it but not how it works exactly.

I will most likely do like you said and tune it with the maf for time being. But i would like to down the road switch to SD and tune it this way so i am use to it before doing the supercharger. This way i won't be trying to learn a new method of tuning while tuning a completely different combo. Once i grasp how things work and interact with each other I can tune and learn it very quickly.

[joecar]

SD mode:
- PCM sees a MAF DTC and so ignores the MAF,
- the MAF DTC disables the HO spark table (COS keeps adaptive spark sliding between HO/LO tables),
- the MAF DTC may disable some features such as adaptive spark, misfire detection and trans shift adapts,
- PCM uses VE table to calculate cylinder airmass,
- can run in CL or OL.

MAF mode:
- PCM sees no MAF DTC's and so reads the MAF,
- above 4000 rpm PCM uses MAF only to calculate cylinder airmass,
- below 4000 rpm PCM uses MAF during steady state conditions and VE during transient conditions,
- can run on CL or OL.

MAF only mode:
- same as MAF mode but with VE disabled, so PCM uses only the MAF to calculate cylinder airmass.

OL mode:
- commanded fuel is richer of CFOL and PE tables,
- COS allows SOL trimming on stoich cells in CFOL table.

CL mode:
- commanded fuel is either stoich or otherwise PE table.


More info: Summary-Notes -> post #4

[gpr]

Thank you for that information that helped a ton!

I have a couple more questions. When in SD COS is there still a PE mode? or do you simply tune it in the higher rpm's and tps/map readings to be at a richer mixture?

I'm assuming CL mode is only possible off the NBO2's? Is there anyway to wire in a wide band and run CL all the time? I'd assume if you ran CL all the time it would simply use the map and tps since the nbo2's can only read stoich. Would be nice to run a wide band with a table to simply command the afr you want. (systems in the past had this ability and was very easy to tune)

There are tutorials on how to tune in the VE automatically by wiring in the wide band. I would assume it is also possible to do this in SD? Also, why is it not easier to tune an engine in SD mode? Seems like you remove one component that you need to tune and verify??? or does this actually make it more complicated?

thanks for the help guys.

[gpr]

one more really dumb question, where can i download these COS? i see the description of them on the main page but no options to downlaod them. I think if i simply downloaded them and looked at them it would help me answer a lot of the questions i have on how they operate.

[joecar]

COS SD still has PE mode:
- COS OLSD: when PE triggers, the richer of PE or CFOL is what is commanded;
- COS CLSD: when PE triggers, PE is what is commanded.

CL is only possible with front NBO2's. This PCM uses only narrowband O2 sensors.

Yes, see AutoVE tutorial.

Yes the idea is to disable NBO2 trimming and isolate the source of airmass and tune/correct that source.

COS already comes with V7.5 installation... not all OS's have a COS. What year/model/vehicle do you have...?

[gpr]

Thank you Joecar for all the help.

Started playing with the car a bit this weekend. The tune currently on the car (just bought it used) has some very odd things done in it, which i need to change around. But the car is a 2002 and the operating system on this car is the one listed for a 2001. Is there much different between these two OS's? should i start fresh with a 2002 OS?

[joecar]

Ah, 2002 Camaro (I reread post #1).

The 2001->2002 OS upgrade is a common 4th gen Camaro/Firebird mod... I don't know why someone went the other way (backward in time)... the 2001 and 2002 files are pretty much identical, the 2002 file has an extra table or two, and maybe some corrections.

Compare your 2001 file with the stock 2001 file, take note of the engine mods, and go from there...

If you say that it is tuned horribly, then you might try flashing in the 2002 file and see how it runs, and start tuning from there.

[gpr]

I flashed it with a 2002 stock tune file and it started and idled but would die shifting into gear. I'm thinking I will stay with the 2002 OS then copy the fuel (possibly spark) tables that was running on the car from the 2001 OS into the 2002 OS as a base line to start with.