ECU and LAMBDA sensors

[spatz]

Hi engine gurus,

I need to setup the closed loop with my DTAFAST S80PRO and LS7 engine myself, kind of a task since it is the first time.
The variety of Lambda sensors is an overkill.
I mailed DTAFAST what to use, but maybe somebody already has experiences with lambda
sensors he wants to share with us.
I understand that the ECU has not much to do if the target Lambda (let us say 1) is met by the engine, if the measured value
however is different then the ECU will start regulating to reach the target lambda, right ?

thanks

[MGGTR]

I would try posting this question additionalty on the DTA Forum.

http://dtaforum.psycode.com/

[spatz]

did not know that there is any, MANY THANKS !

[GTR One]

spatz said:

Hi engine gurus,
I understand that the ECU has not much to do if the target Lambda (let us say 1) is met by the engine, if the measured value
however is different then the ECU will start regulating to reach the target lambda, right ?

thanks

Right! See my PM as I did a lot of work on this with my LS7..

[ROWDYRENAULT]

Spatz I think you have that backwards the mapping in the ECU runs the motor for fuel and timming based on several inputs including throtle position, air temp, engine temp, ect ect. The lambda is there as a sensor only to tell the ecu if something is out of wack. If you tried to run the engine at the lambda value of 1 during accel decell ect ect in many instances the car would fall on its nose. Thats the reason that a factory ecu on say a stock LS7 will probably always run better? smother? less fuss than an after market ECU like my Motec. The Motec will run as well as I program it and it runs very well indeed, but the factory has thousands of hours on the dyno and on the road with engineers and test drivers going to ever more fine points in the map concearning all of the parameters that can change. In the course of bringing a new engine car tranny combination to market the factory will probably map several thousand points. My Motec has probably been mapped at 100 points. lEE

[spatz]

i have the graph form the dyno which proves how poor the sock gm ecu is working, i only need the stupid lambda for the registration so they know that it is somehow working. once i have passed this i will run the engine without the sensor.i have been told that on newer cars they do not bother even measuring the exhaust gas just only read out the ecu and search for lamba errors.
thanks for your help

[ROWDYRENAULT]

Spatz: I will offer this, if the stock ls7 is giving you poor results on the dyno I would look somewhere besides the ECU.

[Scuffers]

spatz said:

Hi engine gurus,

I need to setup the closed loop with my DTAFAST S80PRO and LS7 engine myself, kind of a task since it is the first time.
The variety of Lambda sensors is an overkill.
I mailed DTAFAST what to use, but maybe somebody already has experiences with lambda
sensors he wants to share with us.
I understand that the ECU has not much to do if the target Lambda (let us say 1) is met by the engine, if the measured value
however is different then the ECU will start regulating to reach the target lambda, right ?

thanks

Lambda sensors are there to give feedback to the ECU of what the running air/fuel ratio is.

with the S80 and a V8 engine, you need 2, one in each header (left/right) ideally just after the collector.

in the S80 you then configure them so that it knows which one is which in cylinder order.

you then configure the lambda target map int he ECU, this is laid out much like the fuel map(s) but the value in it is the A/F (or Lambda) you want the engine to run at that point in the map, usually you would have it at 14.7 (Lambda 1) at light throttle/loads, falling to ~12.5:1 (0.85 Lambda) at high throttle/revs (this is the info you need to get for the specific engine preferably after some dyno work)

you then set then configure the ECU's filtering values to something sensible, and check the 'generate fuel correction map'

once this is all done and the engine is running, it will not look at the lambda values, compare them with the target map, and populate the correction map with the changes required to meet the target map.

with a little work on the settings for this, essentially, the ECU will then perfect the fuel map as time goes on, makes mapping the engine somewhat easier and long term, let's you keep tabs on the engine.

[spatz]

thanks, I have now acquired one LSM 11 sensor ( I intend to use only one cylinder row) as this whole lambda
control is only necessary for the registration. They somehow want to see it working and regulating.
The S80 ECU is already set
at your suggestions by the engine supplier but not using any lambda feedback. In general when the MAP is set up
correctly and the fuel is good I was told the lambda values will be ok.

[Scuffers]

spatz said:

thanks, I have now acquired one LSM 11 sensor ( I intend to use only one cylinder row) as this whole lambda
control is only necessary for the registration. They somehow want to see it working and regulating.
The S80 ECU is already set
at your suggestions by the engine supplier but not using any lambda feedback. In general when the MAP is set up
correctly and the fuel is good I was told the lambda values will be ok.

not being funny, but that's a very head-in-the-sand attitude that's probably going to come back and bite you...

[spatz]

why ?

[Scuffers]

spatz said:

why ?

the very fact you need to ask really should tell you something...

Not being funny, but it's just plan asking for trouble, and considering your talking very little outlay to do the job properly, I really don't understand why you would NOT to do it right, after all, how much does an engine re-build cost?

[spatz]

so how do i do it right in your opinion ?

[Scuffers]

spatz said:

so how do i do it right in your opinion ?

wire up lambda senders in both manifolds, configure the ECU to run closed loop with proper target's, drive round for a bit, look at the ECU's correction table, make sure it looks sensible, apply it, job done.

[spatz]

ok will give it a try

[spatz]

ok I did it right, got myself 2 of the innovate LC-1 lambda kits with the wide band sensors and hooked them up to the ECU. Works great even can see the values of the fuel correction map. I also installed their lambda gauge so I can monitor the lambda value constantly. The DTAFAST ECU S80 that I use has a trigger to turn the whole lambda control on/off, very neat !

[Scuffers]

spatz said:

ok I did it right, got myself 2 of the innovate LC-1 lambda kits with the wide band sensors and hooked them up to the ECU. Works great even can see the values of the fuel correction map. I also installed their lambda gauge so I can monitor the lambda value constantly. The DTAFAST ECU S80 that I use has a trigger to turn the whole lambda control on/off, very neat !

well done!

how far off was the map?

[spatz]

very close, as expected, the corrections are minor but that setup really works, I am not using a target lambda map just lambda 1 up to 4000 rpm

[Steve_D]

spatz said:

very close, as expected, the corrections are minor but that setup really works, I am not using a target lambda map just lambda 1 up to 4000 rpm

That is not what you want to be doing.
Lambda 1 or AFR 14.7:1 is a nice gentle mix of best fuel economy/power/emissions so will only be right for...say town driving.
For most power you want to be around 12.5 and a motorway cruise at light throttle can be as lean as 17.

You really need a map with different AFR for each condition then use the O2 sensors to trim it to the map.

Steve

[spatz]

ok that sound fair enough and is pretty much how the ECU has been setup, unfortunately the EU lawmakers have a different idea about that at least I am prepared
now for whatever they ask me for