How is delivered torque calculated in a gen3?

[GBull]

I'm curious how the pcm calculates delivered torque. What degree of accuracy does it provide? I wonder if changing stroke affects the calculations...?

Thanks!!

[SiriusC1024]

Mostly it compares to MBT. The accuracy is low unless MBT has been adjusted for the engine configuration.

[Fast4.7]

It uses MBT and also has a table that converts fuel flow to torque efficiency. On my 2005 P59 it has the efficiency tables for both E0 and E85 fuel. It is basically a BSFC table that has RPM vs commanded equivalence ratio vs BSFC. There is also a table for engine friction losses, accessory and ac compressor loses. If you know the engines actual torque output you can use the QC Fuel factor to get the torque values into the right ballpark.

[GBull]

Ive been logging it and using it to zero in on the best timing values. By making spreadsheets and comparing the torque values by .5 degrees of timing change at a time, I seem to be coming up with good timing numbers. I'm thinking it doesn't matter if the torque values are true to the exact output but are still good for relative comparing with different timings. I can watch the torque numbers go from smaller to larger and then tip back to smaller-or flatten, by the different timing values. Anybody ever tried this?

[SiriusC1024]

That's all in relation to MBT. Torque will decrease if timing exceeds MBT. You don't know MBT on a stroker.

[SiriusC1024]

Just curious, what's your tune looking like now?

[GBull]

I 'm thinking I can find MBT without knowing the actual number. I'm away for the day but will post my tune and one of my recent logs late this evening or tomorrow for your entertainment...

[SiriusC1024]

No you can't without a dyno.

If you want a relative comparison why not track acceleration. Faster acceleration means more torque.

([50020.110]-[50020.110.shift(1000)])/1

Acceleration is the derivative of speed. Rise(mph) / run(s). Here it's in m/s^2.

If you want more resolution then polling rate of mph has to be increased in scanner. Going below 1 second on the math with normal config gets jittery.
accel chart.png

[SiriusC1024]

You can even plot acceleration with respect to the spark table. Comparing logs that way would get your timing optimized. You can kinda find MBT without a dyno. At least WOT timing can be optimized this way.
mbt_rel.png

[GBull]

So a little backround..
Vehicle is 2001 Silverado 2500HD 4WD 6.0l (heavy sled at 6300lbs)
Molnar 3.9" rotating assy and wiseco .010 over forged pistons. 394ci
Truck Norris Cam (Yah, it's a stupid name..and not well loved it seems..)
AFR 205 heads
10.35:1 compression 220psi cranking compression.
8.1 injectors from same year Silverado, using stock truck intake manifold and TB. KN CAI.
Hughs 25 ALXTM tow converter.
Stock tires.
Still on stock exhaust manifolds but going to long tubes in the next couple months.

My goal was to build a good towing combination. The engine now has 4500 miles and I am still polishing the tune. The idle is good, the SD and MAF tables are good, and now I am working on the timing. I had to realize and then fix the pcv system sucking oil into the intake at the rate of 1qt per 1000mi. which was hindering the timing process... I did the typical job of just removing timing to the threshold of ping and then figured instead of just pulling a few degrees across the whole table and calling it done (no access to a dyno) I'd log delivered torque and reduce timing until torque values peaked in each cell. I did this process once across the table up to 3600rpm reducing by 1degree increments, for three degrees. I then created a spread sheet and compared each reduction to the baseline, next I choose the best outcomes for each cell and changed them one at a time. The torque numbers came up by a range of 10 to 20. Best numbers were generated by backing off the timing 2-3 degrees. After seeing this pattern I pulled out 2 degrees for the 4000rpm and up cells. At this point I took a test spin and the "seat of the pants" results were dramatic. I should also add that I did these evolutions pulling a dump trailer full of green firewood to really hit the higher g/cyl cells in the rpm ranges. Anyway, the results were good, but I figured I could do even better by making a finer run at it by breaking the table into 1000-1600, 1800-2800 and 3200-5600 blocks. I created an updated master torque log, and then made 4 more logs reducing by .5 degrees. I have completed the 1000-1600 block and will be starting into the 1800-2800 block tomorrow. After I finish the blocks I will record all the numbers on my spread sheet and change the timing, cell by cell from the best torque numbers. I believe most of the time I will still need to back off timing but the pattern could indicate a slight increase is needed, if so I will identify these cells and work them individually. So in my process I don't really care what the number is as long as I am influencing it higher. I look forward to seeing what kind of raw timing curve I generate using this process. Note: my torque histogram is #12.

I apologize for the wordiness, I rarely post but find my answers by researching the forum. I can not tell you how grateful I am for all of you senior tuners and your wisdom. I really appreciate you looking over my tune, it's all my own work, and letting me know of any problems you see. I look forward to giving your suggestions a try.

Thanks for the interest
GBull






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[SiriusC1024]

The attachments didn't post.

[GBull]

Did this work?

[abc]

I can't imagine that thing only needs 14 degrees at WOT?

[GBull]

I agree. I only recently solved the oil in the intake problem and am hoping to see maybe 5 more degrees. It's been about 600 miles since the clean up of the oil though. Anyway I'll be concentrating on the WOT range a little later in the week. I did desensitize my knock sensors 10% to see if it helped and it seemed to some.. but again, more work to be done there.

[abc]

I did desensitize my knock sensors 10% to see if it helped and it seemed to some.. (help what?)but again, more work to be done there.

Once you change that much of a combo., the stock knock strategy is a pure crap shoot. You should put some serious effort in to the knock strategy if you want to attempt to rely on them. You may want to study op on that before you go searching for max torque. Just listening for knock while your sitting in the cab at WOT is not the best approach. Looking at spark plugs for signs, listening to the engine with knock ears, implementing fuel that is not knock limited during MBT tests are some of the things that should be worked through.

Based on your combo., I would venture to guess, after proper testing, you will end up in the low to mid 20's for ignition advance. That is purley a guess, as I have never worked on that exact combo.

Are we to assume you were getting knock when the engine was ingesting oil, and if so, what were the signs?

[GBull]

knock sensors would pull timing, I would reduce timing and knock sensors would not initiate a timing pull. Never heard the knock. I need to learn about knock ears? what are they exactly? Actual product name?

[SiriusC1024]

Should be more like this. Low timing can make KR due to combustion instability.

Log MAF (Hz).

[GBull]

Should be more like this. Low timing can make KR due to combustion instability.

Log MAF (Hz).

Ok cool, I'll do it this evening when the traffic disperses....

[abc]

I need to learn about knock ears? what are they exactly? Actual product name?

Here is a quick thread that discusses some options and enough key words for you to get googling.
https://www.hpacademy.com/forum/gene...-monitor-tool/

[GBull]

Thanks!!