Wideband AFR's with SNS STG4?

[G60 Carat]

SO I finally got the Innovate LC1 working, and well.....I wish I hadn't


What I am finding is that if I go WOT at 2000rpm, I get only slight enrichment like 13.2-13.8 (sometimes it stays at 14.0 for a moment or two well under light boost)

Then as boost rises about 4000rpm it starts getting rich, and a certain rpm (about 5000) or PSI of boost (12psi maybe), I'm not sure the trigger. It goes insanely fat, like 10.0-10.5 is normal, and I've seen the gauge flash 9.9 a few times. (this might be the injectors going static, I believe SNS chips do that)

Unstable would be the best way to describe the AFR's of this car.

How much much low boost tuning can be down with the COpot? I've heard mixed reviews, I;ve always left it set at 500ohms (I'm going to play with it either way and report back)

What would I be aiming for? I'm assuming somewhere between 11.5 and 12.5 would be best?

[DigiMatrix]

Can you describe the mods to your engine? Pulley, RSR outlet, ISV bypass, cam, exhaust etc? Sounds more like your mods don't match the chip tuning. Now that you have a wideband you can tune the chip to match your exact mods.

[G60 Carat]

8.5:1 compression bottom end, stock head
Schrick 272/272
68mm pulley
Ported Charger (stock collector box)
Audi 5000TQ intercooler
Stock MKII dual downpipe exhaust Manifold
ISV Reroute

[petethepug]

Subscribed

[G60 Carat]

also my idle and part throttle cruising is pretty much bang on. Idle bounces between 14.3 and 14.9, and cruise about the same.

Sparkplugs are eerily clean, just a light tan on the ground strap. Porcelain is very clean and white too, even the base circle is pretty clean. I'd actually feel better if they were a touch more sooty.

I don't seem to be having any problems with knock or ping. (94octane) But like crappy stuff there on tip in, then way rich up top...sigh

edit:

I've read in a few different place now that the injectors do go static at a certain point

I have a SNS chip and the injectors go static at 5000 rpm. The AFR dips about 1-1.5 ex: from 12 to 10.7

higher the ohms the leaner it gets. i found stage 4 G60 at 800 ohms to run about 13.5-14:1 across powerband until about 13psi where they go static.

this would be bad.

your range is probably 200-1800ohms, it has no effect around 12-13psi.

So pretty limited with what I can do to fix the upper RPM stuff.
But my next game plan, is do dial down the COpot to about 200ohms (hopefully this will fatten the mixture at low rpm on tip in), and then drop my fuel pressure down to hopefully fix the static fuel dump up high.

[DigiMatrix]

pm sent. Also what FPR are you running?

[G60 Carat]

Currently at 4.0 I was running at 3.5 . Just the clean sparkplugs and eerily good fuel economy had me nervous. 19mpg. So I switched until I could get the wide band working.

[G60 Carat]

pm sent. Also what FPR are you running?

Got it thanks.

Data was a little weird to crunch. Clearly the COpot has some effect, but in your notes you say that`s not WOT fueling? So does the COpot have any effect on WOT fueling?

[DigiMatrix]

WOT fueling is over and above what I showed you - CO pot is always in the fuel calculation. More fuel will make the injectors go static sooner. At 4 bar, I would think you have more than enough fuel at the top end. If you don't want to change the tables in your chip, then your only option is as you decribe - lower the CO pot and reduce the fuel pressure. SNS stage 4 is built for 3.5 bar fuel pressure.

[2925]

CoPot only adjusts the fuel mixture 1-3% or some such nonsense, tuning wise it is useless. Also the CoPot is NOT active during WOT as the WOT switch changes the fueling to maps saved on the eprom.

[G60 Carat]

I was under that impression too, but it appears the COpot does have some affect on WOT AFR's. Like during testing If I go WOT at 2000rpm in 4th with different COpot settings I get different AFR's values. Once the rpm and boost come up some, then they are pretty much the same values no matter what the COpot setting.

[2925]

I think that's normal, I'm only regurgitating what I've read from others who seem to know about this stuff though so I could be full of it.
Maps kick on at full boost or close to it? Makes sense as this is when the additional fuel is actually needed, otherwise when we got WOT under 3k rpm the car would bog to hell.
Also I am under the impression SNS programmed their chips to run rich in WOT conditions to avoid the #1 lean and overall under fueling caused by full boost in our cars (IIRC).

[G60 Carat]

I dropped the fuel pressure back down to 3.5 bar and set the copot at 200

It does pretty much the exact same thing AFR wise. always starts in the high 13's when you first go WOT, then AFR's drop steady and at 5000rpm go rich into the 10's. But now it's in the mid 10's instead or low 10's.

[DigiMatrix]

CoPot only adjusts the fuel mixture 1-3% or some such nonsense, tuning wise it is useless. Also the CoPot is NOT active during WOT as the WOT switch changes the fueling to maps saved on the eprom.

A CO pot setting of 491 ohms is the neutral point. At this value, it neither adds nor subtracts to the fueling. Below this value it subtracts the value the ECU sees from the value it sees at 491 ohms and then takes the difference and multplies it by a value returned from one of the tables in the binary that is a function of boost pressure, divides it by 16 and adds it to the amount of fuel calculated to that point in the fuel calculation. The calculation is not completed at that point, and it has to be converted to injector pulse width and then the injector battery voltage offset added.

for values above 491 ohms to 2000 ohms the same calculation is performed, but the CO fuel value is subtracted from the main fuel amount.

So if you think about it, when you go to injectors that are larger or increase your FPR setting and don't change the CO multiplier table, the percentage of fueling change is larger because normally you have to reduce the values in the main fuel table to get the correct AFR.

Also the CO pot subroutine is called irregardless of the WOT switch. WOT table fuel calculations are also over and above the other fuel calculations - they are just added.

[G60 Carat]

short video of what it looks like when you grab a high gear and go wot.





shot with my phone sorry.

[G60 Carat]

Hmm SNS states that it's the WOT switch contact being broken between shifts that can cause it to go lean and then come back in every single shift.

Maybe when I'm spraying nitrous this summer, I'll just wire a little switch inside the car and tie it into the WOT switch wires. Then I can flip the WOT switch to stay on and still in "rich mapping" for the whole time. Basically hiding the shifts from the ECU, because it won't ever see the throttle lifted between shifts?

Anybody done this little lie to the WOT switch? How did it work out?

[crazynorweegian]

Hmm SNS states that it's the WOT switch contact being broken between shifts that can cause it to go lean and then come back in every single shift.

Maybe when I'm spraying nitrous this summer, I'll just wire a little switch inside the car and tie it into the WOT switch wires. Then I can flip the WOT switch to stay on and still in "rich mapping" for the whole time. Basically hiding the shifts from the ECU, because it won't ever see the throttle lifted between shifts?

Anybody done this little lie to the WOT switch? How did it work out?

I have heard that the stage 5 SNS chip bypasses the switch and uses the map sensor. Maybe grab one of those?

So, how do you want your AFR performance to go? I am just curious as to what you are expecting of it. Maybe I am having issues too and just don't realize it?

[REPOMAN]

The DIGIFANT uses a MAP [Manifold Absolute Pressure] sensor
mounted in the ecu it is a specific size, 1 bar=15psi the sensor
fills with the manifold pressure sending its reading to the ECU 8MB
EPROM chip to adjust the injector pulse according to the program. I.E. digi lag.
The ODB 1 and ODB 2 ecu uses a MAF [Mas Air Flow] the problematic
air flow meter on the intake track measures the air flow entering the
engine, calculates the values then sends it to the processor for instant fuel correction .