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Discussion Starter · #1 ·
Anyone know what the T7 Suite - SID Lambda value is suppose to be at idle? in gear? accel? etc.

I'm experiencing poor gas mileage, no other symptoms and wanted to rule out 02 sensor

2000 9-3 SE Stage 4 JZW automatic vert
 

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Any time the ECU is running in closed-loop (feedback) mode it should be trying to reach lambda = ~1.00 by definition.

It is probably programmed to be richer during acceleration and at WOT.

Drew
 

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Closed loop is when your computer is using the sensors to figure out fueling/ignition. You're in closed loop at idle when the engine is warm, and you're in closed loop when you are cruising at a steady low throttle. Therefore, lambda should be 1 during those two points in time. I believe it goes to 0 at high load or anything close to WOT, and technically when your engine is warming up from a dead cold start.
 

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I believe the LAMB value seen in SID is not actual O2 value, I believe it is the lambda integrator value. It the percent adjustment to the afr to reach lambda 1. Please correct me if I am wrong.

Mine is all over the place under closed loop, when open loop it goes to 0.

There is a spreadsheet out there that sorta explains what all of the SID info really is..... but I can't attach xls, and printing to pdf don't make sense with this.
 

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Discussion Starter · #11 ·
NFS - I think the issue is that our T7 Suite SID is showing lots of Positive and Negative values on Throttle. This morning I watched it start at 0 for a minute at startup and then into negative numbers...on throtttle (cold) it went to 0 but then it fluctuated - & + after warmup. Are you saying that any throttle should put the SID Lambda at exactly 0?
 

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Lamda is shown in the open sid function to show how much the ecu is adapting or adding or pulling out fuel to maintain stoich or 14.7/1, 2500 would be 25% and 250 would be 2.5 % and 25 would .25 of 1% and its just a reference to use as a aid to see if your fueling is way off, I have seen some add as much as 2500 and of course negative numbers mean its pulling out fuel to maintain stoich. If it goes over 2500 or -2500 for too long, a cel for short term fuel trim will be tripped.

The amul will tell you the true story and that is what I watch more than lamda, that is for short term diagnostic use, the amul will tell you what is going on with long term fuel adpatation. I have seen the stock viggen file run at 1000 or 1100 or 10% or 11%. My current file is running 120 to 320 or 1.2% to 3.2%.

I have seen some tunes run in the negative ranges, -1100 or -11%.

The sid functions are most useful for diagnostic purposes in my opinion, that really helps with tuning. I like to watch the coolant temp, intake air temp, airmass, torque and the knocking conditions. I occasionally look at amul to see where I am and as long as I am under 10-12%, I do not worry to much.

When cruising or at idle, the car is running in closed loop and will run at 14.7/1 and gas mileage should not be effected during this time while cruising along on the highway, once you go over a set value, say 700 airmass, it will go out of closed loop after a certain amount of time as expired and then finally go to the pre-set tuned fuel maps and ignore the 02 sensor.

Getting up to speed and doing pulls is what sucks the gas down, not cruising on the highway in closed loop.

Its much safer to be on the rich side anyway, would not want to be lean with a stg 4 tune.

John
 

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It's a long term fuel multiplicative value. If the ECU has been reset decently recently, and you've not been 'beating on it', expect the AMUL to change accordingly.

I've heard people say don't worry as long as it's 700 or less. A negative value means the opposite.
 
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