WOT aft and timing

[RevGTO]

The stock 99-00 timing tables are pretty aggressive in the peak torque range of 4000-4400rpm. I would routinely see max KR at the track running about 13.0 Richening up to the mid 12's didn't help much. So I backed a few degrees of timing out of the affected cells. That and bringing the octane up a bit takes care of all of it, so I can run my preferred 13.0 with zero KR.

[5.7ute]

hi 5.7ute,

I dont have a wide band, hence just changed one thing at a time, did a run and see the out come. There were like 4 points in the log file where the car knocked, upto a max of 5 deg was timing was pulled in 3rd gear at 4000rpm (worst) just as the MAF takes over right? Or is the MAF fully incharge on WOT.

I understand how the timing ramps, goes from like 24-28 deg on stock tune from about 3500-6000 rpm. My issue was that the commanded AFR is 11.7 which is clearly far from optimum. Essentially I reduced this to 12.6 commanded to see if I got knock, which I did but only 2 deg in 3rd, again at 4000rpm. So I richened it to 12.45 and the knock was WORSE, so it appears that this is actually burning faster (i really want to know how it relates to real AFR) for the same timing and knock was 5 deg as above. Basically I am now going to reduce the timing with AFR at 12.45. The innovate links Shawn posted are really useful, basically less fuel and timing gets similar or more power (a few hp like you say) than rich and more timing. And I would prefer to run less fuel and timing to achieve the same goal as super rich more timing

One question again (not at WOT just driving normal), say when running MAF only (enable at 400 rpm so that is the only thing controlling fueling right?) if I command 14.63 and a WB says it is leaner or richer, even though everything else is the stock tune does this point to incorrect MAF calibration OR incorrect injector rates OR the O2 switch point being off so adjusting trims??? I assume the latter with the O2s so I would change these such that I get a roughly stable 14.63 as I would assume the MAF and IFR are correct, or are the O2 best at 450mv as was mentioned before??

Airmass prediction is taken from the VE table until the RPM threshold of B0120 is met. (Stock 4000 RPM) The maf is still used as a sanity check. Once B0120 is reached, in a steady state, the Airmass calculation is taken solely from the maf. In a transient condition there is some tricky use of the maf, VE & transient tables which I have not fully nutted out yet.
Enabling the maf only at 400 RPM will cause some fuelling discrepencies at low engine speeds as airflow is erratic due to reversion.

Now, while commanding 11.7 AFR you may have only had an actual AFR of 12.8 AFR. Once you lowered commanded AFR to 12.6 your actual may have still been well over 13.2 AFR, causing the KR. Enrichening commanded to 12.4 would still be leaving you too lean at peak torque, again a wild guess at 13.1 AFR. One thing to ponder is that a certain AFR will give you a fast burn. Richer or leaner from this mixture the burn will be slower & less prone to knock. (I cant remember where I got this info from but I will chase it up) I believe this is happening in your case as a slight enrichment is making the engine more prone to knock. (A rich mixture can also cause knock, but without wideband verification this is all conjecture)
Post some logs if you can.

[N0DIH]

Here is the stock L67 Supercharged R/L Threshold.



It is interesting, it isn't allowed to switch until it gets well past 450 on the rich side. And despite being 500mV on the low, it swings well past....

Luke:

Some people still run stock setting O2 switchpoint setting with headers. I experimented with a range of 400-550 mv and tried to align up a mv reading to my B3601 of 14.63 AFR. I settled on 550mv across the board. I do not necessarily recommend that setting to everyone..but thats where I ended up.

You will have to experiment...

Regards..

[WeathermanShawn]

Wow, I really like that table & display. Our OS goes by 'Closed-Loop' Modes which are related to airflow (g/s).

That display really looks user-friendly. Is that yours or EFILive's?

Anyway, thanks for sharing. Very interesting..

[N0DIH]

That is TunerCat OBD2. I have EFILive Scan, not Tune yet. I use Tunercat for Roadrunner tuning. It rocks.....

LT1's have modes and switchpoints. 3800s don't have the CL Modes for it. The LT1's do IIRC (my 94 did)

Wow, I really like that table & display. Our OS goes by 'Closed-Loop' Modes which are related to airflow (g/s).

That display really looks user-friendly. Is that yours or EFILive's?

Anyway, thanks for sharing. Very interesting..

[maudyZ28]

thanks guys, I looked at the Z06 2001 tune and the O2 points are at 525, even the 1999 corvette C5 are different to the camaro, different sensors I presume?? anyway i digress

5.7ute, the 'innovate' link before that Shawn posted explains the fuel mix thing. Lean or rich burn slower and the best AFR is between 12-13.

Basically on 11.7 stock tune, no knock as expected
Change to 12.6 and get a 'small' amount of knock'
So i richen it to 12.45 and get MORE knock (must in fact be burning faster here, more optimum burning mix) still don't know what it really is (and had all O2 points at 450mv then)

I am going to change it to this and reducing timing by 3-4 deg and see how the car drives. Need to wait till next track day (3 weeks) and i'm competing too in a bracket series and my times are far from consistent, i can get power down on street tires :(

When doing the calc VE i enabled my MAF at 400rpm and the car ran quite well but i was driving very steady no raid throttle changes. Does it still try and use VE here if not in a steady state?? Also steady state means constant air flow so how above 4000 rpm is it steady state?? it cannot be because the MAF airflow ramps with rpm as more air comes in??

[WeathermanShawn]

When doing the calc VE i enabled my MAF at 400rpm and the car ran quite well but i was driving very steady no raid throttle changes. Does it still try and use VE here if not in a steady state?? Also steady state means constant air flow so how above 4000 rpm is it steady state?? it cannot be because the MAF airflow ramps with rpm as more air comes in??

If B0120 is set to 400 rpms, then the airflow from the VE Table is essentially ignored. It is using MAF calculated airflow (g/s) regardless of Rpm or steady-state. The concept with CALC.VE Table is that the airflow calculation from MAF when applied in that extensive Formula that Joecar worked up, is to calculate the dynamic airflow solely from the MAF and LTFT corrections.

Then when you are through, your MAF-derived Airflow and dynamically-derived airflow are essentially comparable. So after you complete the process, all your steady-state and transient airflows are in unison.

The 4000 Rpm threshold is a separate topic. It is not really applicable when you have it set to 400 Rpm. From the factory the 4000 Rpm threshold is as you stated. The amount of airflow at those Rpms are considered reliable enough to use the MAF exclusively.

It is very easy to confuse differing tuning methods while utilizing a method. The CALC.VE Table Tutorial is for those tuners who wish to utilize MAF-Closed-Loop. The resulting VE Table is reasonably accurate. While it is a natural instinct to think things through, it would be very easy for someone to miss a vital step.

If you do it correctly, your LTFTs, MAF Calibration and VE Table will be accurate. You will know it when your Trims average near zero, your Commanded Fuel in stoich and PE Mode match. Your CYLAIR.DMA and DYNCYLAIR.DMA Pids that you selected will rapidly converge to the same units. Normally by the 2-3rd log this occurs.

In some ways you just have to do it. Do it too fast or not reading the entire Tutorial will be self-defeating. With a wideband and functional narrowband sensors, you should be able to do this in an afternoon.

I would just slow down and make sure you do all the steps. Then it will make sense. It is hard to pack all of this in a Tutorial, but in essence all the remarks I have here are in the Tutorial.

Get that wideband and it will be a lot more productive tune..

[tor1965]

Is it so that if I am following the CALC.VE Table Tutorial it will let me tune in both the ve table and the maf table even if they are way out to start with?

[maudyZ28]

thanks again Shawn,

Im just trying to get in my head what runs what, I posted another topic about VE tuning without the MAF but using VE table exclusively.

I also wish I had a dyno it would make it sooo.. much easier. I think 3rd in auto is best to get a nice MAP but that goes from 0-160 mph, so I use 2nd which is still 0-100 mph capable as i probably look quite strange speeding up and slowing down and accelerating smoothly etc not to vary the throttle too fast. More logging needed, ill have to go on an epic drive Do you recommend Loading the car with the brakes??

tor - yeah start with a stock tune and assuming car has stock injectors etc you dont need to change anything. Go for a dive and log the PID and MAPs as per Shawn's tutorial. Make sure you have that calc_pid file. It uses the LTFT as the BEN factor if you dont have a wideband if you do then use it as a check to see how LTFT behave. Then correct the MAF frequencies and VE table to suite. The idea is using the MAF to measure the air flow to calculate how much the engine is asking for ad there by correct the VE table to match the MAF. I think also if you exclusively run the MAF and then correct it, the BEN factor will be one, such that the MAF freqs are correct. I'm sure Shawn can help you out if I havent explained it right, but thats how I understand it.

[joecar]

See my profile page (click on my username at left) for summary/cheat-sheets