BJ67

Right now, fully warmed up and just cruising at a steady 2000 RPM, my AFR is 14.75. I am going to do a second gear WOT pull from maybe 2000RPM to redline to see what the AFR is.
My concern is its lean , AFE CAI, lowered water temp 180 stat, cooled and dedicated fabricated air intake path from rf grille opening to aircleaner filter, have the hot water hoses and intake tube insulated for less heat transfer ,a piece of insulation under the throttlebody (on top of the water pump housing) all the plastic cover and insulator blanket off the intake manifold. I am sure I have created a cooler intake charge and I believe lean fuel-air mixture and cool inlet at WOT could be a loss of HP and a recipe for detonation.
What would be a safe range AFR At WOT?

tblu92

The commanded AFR during P/T is a 14.11 only for the 1st time this rich on the DI C7 engine In years previous the P/T AFR was at STOICH which is 14.68
14.75 would indicate it is somewhat lean at P/T However remember when lifting off the throttle the DFCO system kicks in so you get crazy lean AFR's that can be mis interpreted
DFCO is "deceleration fuel cut off" where to save gas the ECM shuts off the fuel and you get very lean readings --so make sure when you are reading AFR's at P/T it is not after decelerating
Now that being said --- I installed the same AFE CAI----This system added so much air that i had to ADD aprrox 13% of fuel via the MAF to compensate at P/T
As a matter of fact Diablo now has a specific AFE CAI tune that does the compensation for you
At WOT so may variables can come into play--the only way to get the AFR correct is to use a wideband 02---Typically at WOT these cars are set up rich anyway--so even a 10-13% leaness will still be safe--just make more HP !!! Older C5-C6's would run best and safe with a WOT AFR of about 12.7-12.8 However the new DI engines run best with a slightly leaner WOT AFR like 12.9 to 13.0
Only way to verify WOT fuel is using a wideband and a tuner that has experience with the new DI engines

schpenxel

The wideband reading is based around a stoich value of 14.7. It actually reads lambda (all widebands do), not AFR. It's just multiplying the lambda reading x 14.7 because that's what most everyone uses and it used to. This is why tuners should be using lambda and not AFR.

GM started using 14.1 for their stoich AFR values as that's what most pump fuel is now. In closed loop it doesn't actually change the AFR. It's going to run at lambda = 1 regardless of whether you have E0 or E10 in it and whether the stoich AFR table is set to 14.7 or 14.1.

Bottom line at part throttle you're running at lambda = 1 so nothing scary there.

What are you seeing @ WOT?

Also, there is a MAF and IAT that will see if more and/or cooler air is coming in. It's not like the sensors are there for looks--I'd be surprised if it's too lean. DI engines should be ran leaner anyways.

Unreal

Almost all modern cars have stoich set to 14.1 to account for E10 gas.

BJ67

I did a 2.5 minute data log with my diablosport intune pretty much steady 60 mph @ 2000 in fifth gear. Steady light throttle to maintain speed and then turned it off. The AFR scale has 3 readings min,max and the 1st one was scale. All 3 were unchanged @ for the full 2.5 minutes at 14.75. All the other pid's change a lot while the other's fluctuate. Shouldnt this AFR change during a short WOT test, like 30 to 90 in 2nd gear?? shouldn't it drop to at least 13 to indicate a decent WOT afr? If the AFR stays at 14.75, then I assume the Diablosport tuner is not reading AFR.

schpenxel

Sounds like you're reading commanded AFR and not actual. You can't read actual without a wideband. The factory o2 sensors can only tell if you're richer than stoich or leaner than stoich, they can't tell by how much.

robert miller

Nice write up on what the DI motor does. Also like he is telling you here the leaner it can run to a safe point in any motor with out getting knock is going to make the most power.

It is just finding that point on any motor set up and each motor is diff due to what every. Robert

BJ67

I am using the Diablosport tuner to data log and have the 93 AFE CAI installed for a long time. I am a old school methodical high performance tuner and a decent wrench. The new stuff I am out of touch, but totally understand timing issues, lean/rich issues, combustion temps, water temp pro's and con's. Distributer tuning and carb tuning, intake temps were my specialty. I know that a overall cooler running engine mixed with cooler intake air temps, the fuel injection system has to create a richer mixture versus water and air temp 20 degrees hotter ie 180 degree water vs 200 degree water temp and like on a 75 degree day to have 75 degree IAT versus 95 degree IAT. A lean WOT for instance 13.5 on a 90 degree day isn't bad, but on a 70 degree day that 13.5 AFR would actually be leaner or in other words the engine wouldn't seem to like that afr at that temp. in my way of understanding tuning. On a cold day I would jet richer, hot day jet leaner. FI should compensate automatically.

BJ67

I assume then during a WOT 30 to 90 MPH pull in 2nd gear AFR wouldn't change what I am seeing with this tuner, its not reading actual AFR. If its just reading the commanded AFR, wouldn't the commanded AFR change eventually at WOT?

schpenxel

Commanded AFR should have changed @ WOT, yes. I can't say why it didn't without seeing the tune and a log.

But yeah, just using a hand held with no wideband you aren't seeing actual AFR, just commanded.

schpenxel

Don't encourage the bozos.

Unreal

He maybe reading actual, but with no input into the diablo, it will just display a constant unchanged valued. You need the analog input hooked to a wideband to read AFR.

BJ67

I haven't done a WOT pull yet to see if the commanded AFR changes, I hope I see a change and if the commanded AFR is in the safe range.
I do have a choice of analog or digital log data, what would you set it to read?

schpenxel

I suspect it doesn't matter--I think that is for logging external sensors, i.e. wideband, which it sounds like you don't have

I don't use an intune for tuning personally so I am not 100% sure.

BJ67

The MAF is constantly changing very quickly, plus I do not have a clue what the #s are telling me, the volumn of air? being swallowed? what is more air or less air? IAT is just about right at ambient air temp which is good. Yes I know I shouldn't be data logging, but as long as I can make some sense of the basic info AFR, timing advance, timing retard, AIT, it will at least allow me to believe or determine the engine is running on the strong side and not the weak side.

schpenxel

Could be frequency, could be airflow. Probably airflow. Does it have a unit on the MAF reading? Grams/sec, hz, lbs/hour, something like that?

BJ67

Yes, all of those.

schpenxel

Then there ya go

Unreal

You don't have a wideband, so reading AFR doesn't mean anything. Might as well stare at the sun and guess your AFR.

Command doesn't help either.

BJ67

Just did a WOT quick data log with the Diablo intune, as soon as I got 99.8 % throttle, the equivalence ratio (AFR in parenthesis) goes from the steady 14.75 to 17.1 the whole time 2300 rpm to 6325 rpm WOT in 2nd gear. As soon as I lifted, goes right back to 14.75 . How can the commanded AFR be that lean? or am I interpreting it wrong.