schpenxel

It's inverted most likely--even though GM was supposed to be reporting EQ ratio they actually report commanded lambda on 2006's and up. I have a feeling the intune isn't interpreting this correctly. HPTuners had the same problem at one point in their new software until they realized GM wasn't reporting things correctly.

BJ67

That is good to hear. The part throttle commanded AFR at 14.75 from what I read is stoich. Any thoughts at all what the 17.1 at WOT could possible relate to? the value changed 2.3 points.

BJ67

Inverted like it should have dropped 2.3 instead to 12.45?

schpenxel

My first guess would be 14.7 / 17.1 = 0.86 lambda.

0.86 lambda x 14.7 stoich = 12.63

But all the stock ZR1 tunes I've ever seen are richer than that AND go richer by far at higher RPM's. I wonder if you're hitting a limit to how lean the intune will report (it's obviously not ACTUALLY that lean, but if I had to guess I'd say that's the leanest number the intune can spit out)

Total guess though. Like I said, never used an intune personally

BJ67

The 14.75 is at steady throttle cruising, the 17.1 was immediate at WOT and held that for the complete WOT range from 2300 RPM to 6325 RPM, than immediatly dropped back to 14.75 when I lifted.

jim2092

As Unreal has said here. Stop trying to tune at WOT without a wideband. Actual AFR at WOT is way more important then some crazy possible commanded number.

Unreal

Exactly. Your trying to log something the diablo cannot log. Might as well have it log cycle of the moon or something else, because it is useless data.

Get a wideband, then report back.

BJ67

Thank you again, I am really just trying to see if I need some tuning. Was trying to determine some ball park #s and determine if anything was way out of whack before I get a tuner involved. Knowledge is power and I have the Diablosport intune and was utilizing some of the features.

schpenxel

You can't really do that without a wideband

Unreal

Your trying to use features that are not supported on a corvette. Reading WOT on a mustang works great, on a vette it does not work. That is a generic device that works on tons of different cars, so not all features work.

BJ67

You are correct, Mike from Diablosport says the 17.2 in inverted, deduct the difference of 2.4 = 12.3 commanded AFR

schpenxel

Win

tblu92

When you lift off the throttle the DFCO system kicks in Deceleration fuel cur-off so it is near impossible to get an accurate AFR using a wideband as the fuel changes happen to rapidly to get a real reading----
YES on the C7 GM changed the closed loop fuel AFR to 14.11 due to ethanol based fuels
But Stoich is still stoich 14.68 so with a DI engine they are actually commanding a closed loop fuel richer than stoich
When going into power enrichment however the commanded AFR for a DI engine is far leaner than any previous LS engine due to direct injection
You have to remember there is a difference between "commanded " AFR and ACTUAL AFR--- Only a wideband will tell you actual AFR
IAT temps---coolant temps only adjust TIMING based on these inputs --however PE fueiing remains the same and is only scaled by RPM----even on an LS engine

schpenxel

Good to see you're still an idiot.

Unreal

This is all wrong, so please don't listen to this guy.

jim2092

This is my favorite "But Stoich is still stoich 14.68" after acknowledging the use of ethanol based fuel.

BJ67

I am old school and the new technology is complicated , but I am sure cold IAT and cold water temps should have a definite impact on AFR. Any engine has to run richer when cold or cool compared to 200 degree water temp and 90 degree IAT to some extent.

schpenxel

Not really. Once it's in closed loop it's targeting lambda = 1. Doesn't matter if it's 120* or 220*.

Now, for cold starts.. you're right. i.e. think choke on a carb, but that only lasts a minute or two.

BJ67

That sounds logical, lets say a good light throttle cruise AFR is 15 to 1 , can the engine really run that lean lets say on a 40 degree day with 40 degree IAT, doesn't the system richen itself? The old days and early emissions had cars running on heated air and lean mixtures. If that heated air source was lost, the engine would hesitate and surge when fully up to temp and choke open because the air being ingested was much cooler. Cooler intake air created a too lean condition as the afr was fixed. How does todays technology adjust for that? the old days you would richen the jetting on a very cool race day, lean it on a hot day

schpenxel

Basically it uses feedback from the O2 sensors to know whether to add or subtract fuel from whatever it's calculating based on MAF sensor, IAT, MAP, RPM, etc.

It's still targeting lambda=1 regardless (during part throttle/closed loop operation)

So, if it does go lean or rich it corrects itself, basically.