Analyzing log files

[Rich Z]

BTW, I took photos of the oxygen sensors looking for the differences between the fronts and the rear sensors.

Here's what the rear sensors look like:


And here's what the front sensor looks like:


Looks like the rears are more open to allow gases to more easily reach the sensor itself. In any event, there is definitely a difference.

[joecar]

Well, coincidentally when I was pulling off the exhaust, I found that one of the vacuum lines on the turbo wastegates wasn't threaded in tightly. Actually it was barely threaded in at all. So that certainly would have been a vacuum leak there. But what is it in the MAP trace that tells you that, if you don't mind explaining it to me?

It looked very wobbly when there was no reason for it to wobble.

[joecar]

I looked at all 4 sensors on my F-body and they are the same as your second pic.

Are yours all the same brand...?

[Rich Z]

I looked at all 4 sensors on my F-body and they are the same as your second pic.

Are yours all the same brand...?

Beats me. Interestingly enough, I found another rear sensor in a box of old parts off of my car that is the same style as the second pic, but with more slits for openings. The impression I am getting is that the rear sensors must need more airflow than the fronts for some reason.

[Mr. P.]

In my truck (2003 Silverado SS) the 'perforated' ones are the fronts... just be sure you are using the correct sensor!

As you KNOW you are running 93-octane E0 gasoline, the stoich of 14.63 you are running how is correct. If you are forced to use 'federal' gasoline E10, then your tune may be seriously off at high power levels IMO. The rest of us are forced to run crappy gas!

[Rich Z]

The sensor harnesses themselves attached to the sensors will tell me whether they are fronts or rears. The fronts have a flat 4 pin connector, whereas the rears have a square 4 pin connector. So when putting oxygen sensors on long tube headers, the choice offered to me was either front sensors with extension cables, or rear sensors with an adaptor to convert square 4 pin to flat 4 pin.

Once I get the issues straightened out on my car I will probably have to go with E10, since taking the car on any long trips out of town will certainly have me using the E10. I only know of one area locally that has the E0 93 octane fuel. The main reason I was using E0 was because I used UV lighting and could actually SEE the rubber lined SS braided hoses on my car weeping the E10 gasoline through them. The gasoline noticeably fluoresces under UV. And I could certainly smell gasoline whenever I walked into the garage, obviously coming from this car. Made me nervous, to say the least. I just got done yesterday putting all new PTFE ss braided fuel lines in, so to simplify things I will likely go back to the E10 pretty shortly.

Hopefully I'll have my car back on the street by the weekend. Assuming the weather clears up, that is.

This brings up a question. What about the stock tunes on cars prior to E10 being prevalent at the gas pumps? Are their tunes "seriously off" at WOT?

[Mr. P.]

...What about the stock tunes on cars prior to E10 being prevalent at the gas pumps? Are their tunes "seriously off" at WOT?

Yup; but stock vehicles aren't trying to make >600 forced-induction hp!!! In other words, stock power outputs do not require the huge amounts of enrichment fuel needed to cool the combustion chambers at the high power levels we enthusiasts are demanding now. The risk of damage is low if your AFRs are in the high-12s instead of the low-12s making only 275-325 natually aspirated horsepower, that is a whole different operating reality than delivering 800+hp at any extended period of time at 12.0:1 AFR instead of 11.5:1 AFR! Also remember that in older stock forced induction tunes (think like, Buick Regal V6 supercharged or turbo 3.8L motor) the calibrations were very fat at the top-end of the commanded AFR table just for a little insurance. The Delphi guys weren't stupid, in their time they had to deal with crappy California gasoline (which is now since 2012 federally mandated).

- Steve.

[ScarabEpic22]

And GM DUMPs fuel, at least in the truck cals. My TBSS commands between 12.1-13:1 during PE yet I actually get closer to 11.5-12..5:1.

Here's a pic of my last dyno day with my TBSS, run 1 was stock tune + efans patch + speed limiter removed. Run 3 was a spark-only tune to see what the power difference was going to be (ie completely stock VVE and MAF tables). Run 4 was with a 4" fenderwell intake that pulls air from behind the front bumper and the same tune as Run 3 except with a stock Z06 MAF curve so it would run. (not the best indication of stock fueling but the first 2 runs are.)

[Rich Z]

Yup; but stock vehicles aren't trying to make >600 forced-induction hp!!! In other words, stock power outputs do not require the huge amounts of enrichment fuel needed to cool the combustion chambers at the high power levels we enthusiasts are demanding now. The risk of damage is low if your AFRs are in the high-12s instead of the low-12s making only 275-325 natually aspirated horsepower, that is a whole different operating reality than delivering 800+hp at any extended period of time at 12.0:1 AFR instead of 11.5:1 AFR! Also remember that in older stock forced induction tunes (think like, Buick Regal V6 supercharged or turbo 3.8L motor) the calibrations were very fat at the top-end of the commanded AFR table just for a little insurance. The Delphi guys weren't stupid, in their time they had to deal with crappy California gasoline (which is now since 2012 federally mandated).

- Steve.

OK, I'm not shy about admitting I'm confused.

So if my car is tuned for stoich (does that word sound like it is spelled?) at 14.63 for E0 fuel and I put E10 in the gas tank, which if I understand correctly has stoich of 14.13, then am I not running (assuming I'm in OL without the O2 sensors making any changes) a half a point LEANER than I should be? In other words, E10 requires a richer AFR than E0 does? Meaning it takes more fuel using E10 to reach the proper air/fuel mix than it does with E0?

So, again, what was E10 supposed to gain for us? Looks to me that gas mileage will take a hit. And I hear they want to go to E15 now?

Hmm, well the guy who tuned my car tuned it for a commanded AFR of 14.63. So basically unless you find some non traditional source of E0 then the tune should actually be for 14.13?

I'm presuming that this is one of the constant values you need to have correct before you even start with the tuning? Like the IFR table?

[joecar]

Yes, half a point leaner.

Alcohol has a lower energy density BTU so yes you will see reduced MPG (edit: and a lower stoich means more fuel is used).

Yes, 14.13 (or something between 14.1 and 14.2).

If you don't initially set the correct stoich AFR, then tuning will bake in the difference.