Changing afr

Hello everyone,

I just want to make sure of something, if my afr is moving from 12.3 to 12.7 and i want to set it to 11 should i divide 12.7 by 11 then multiply it by the number on the table or should i take the middle number which os 12.5 and divide it by 11?

Thanks

Omaralsuw,

Assuming when you say "my afr is moving from 12.3 to 12.7" you are sitting steady in one zone?

If yes, have you investigated as to why it is moving around so much?

If your AFR is moving around that much then even when set to 11:1 it will most likely still be jumping around.

I would take the average of the 2 (12.5) and divide that by 11 which = 1.136 and multiply your VE number by that.

Hello chris,

The AFR keeps on changing when the car is on wot, as it goes through the rpms. Is there a way to make all of the afr change to a constant number, when i dont have any device to log the fuel?

I'm not sure I follow? Is the fuelling changing under steady state conditions in a single cell in your fuel table? Or simply as you move through the cells during a WOT ramp run? It's not uncommon to see the AFR move around a little under steady state conditions, but not as much as you're reporting. Generally I'll accept +/-0.1 AFR from my target. If the AFR is moving during a ramp run, it may simply be that you need to correctly map the fuel table.

Assuming your fuel table is correct and isn't causing the problem, I'd be looking at aspects such as your TPS or MAP sensor signal stability. If for example the TPS signal is noisy, it can request accel enrichment which will result in erratic AFR. Also any comp tables that are active can result in what you're seeing.

Hello andre,

Just to make it clear, it keeps on changing while it is on a ramp run on wot. But the problem is i dont have any device to log the fuel, as a result it is kind of hard to keep it constant through the run thats why i am asking if its possible for example, if it keeps on changing through 12.5 and 12.7 to divide the current fuel with the target which is 11.5 and multiply the whole high load table with the answer. 12.7\11.5 = 1.104* the fuel table on high loads, will it give me a constant value through the whole ramp run?

Thanks

Omaralsuw,

Multiplying your whole high load area of the map to change the AFR won't fix your issue, the AFR will still move around, just at a richer mixture.

I would agree with Andre and say that if the fueling is moving around during a ramp run then it sounds like your fuel might not be mapped correctly.

Since you're not logging AFR I am assuming you're watching a gauge while doing a run and seeing the AFR move around?

I would suggest doing small runs on the dyno (or road if you're road tuning) maybe going to 3000rpm and watch the AFR gauge and tweak the fueling until it reads your target, then do a run to 4000rpm and tweak the fuel then 5000rpm and so on. Doing it in small runs will help you remember the areas which need fuel added or removed breofre doing a full run to redline.

Once the fuel map is tuned correctly I would expect the AFR to stay within +/- .1-.2 AFR during a ramp run

it sounds to me like you have a wideband AFR gauge, and a tunable ecu. Is there any reason you cant run your analog out from the gauge to a

spare input on the ecu? What ecu is it? I may be able to assist in directions to wire it up. its really just 1, maybe 2 wires.

then you can log while you do pulls on the street, and then look at the logs and fix the trouble areas.

please state what kind of ECU/engine are you working on, and your tools

I am using motec m600 on a tb48 engine, and i am using a ntk lambda sensor with an ntk gauge.

The problem is i need to have the lambda option with the datalog option enabled

Can you increase your VE based on the datalog of engine load?

You can still use an external lambda controller (assuming your NGK gauge has an analogue voltage output? You can connect this to an analogue voltage input on the m600 and then calibrate that as a lambda input with the relevant data of voltage vs lambda from the wideband manufacturer.

If you're trying to make tuning changes during a ramp run based on just watching the wideband gauge, it will be very difficult to make changes to the correct points in your fuel table.