VEMS high AFR on idle

[Jamo]

Vems Afr

[Bram]

OK, I tried to start the car and it works, but now I noticed the idle is very bad with lambda 1.25. Once I start revving higher the red dots disappear and lambda goes back to 1.0. I see on idle all red dots lighting up in megatune and warning like miss-fires in the bottom right red box

Now Marc told me he used in my config 630 ccm @ 4 bar FPR, which should give (according to my calculation a req-fuel value of 6.49 * ( 2226 / 5 / 727 ) * 0.75) 2.98
Now I see that Marc set my req_fuel value to 3.8, which seems to be really much more then I calculated. Marc told me he took the 630 ccm @ 4 bar FPR into account.

Anyone has an idea what could be wrong?

[a4kquattro]

Hi Bram,

you can ignore the misfire light, its effectively meaningless.

For whatever reason you might have a slightly different VE due to different vacuum at idle than the basemap I supplied. If your fueling is sensible through the rest of the map other than at idle, go into the VE table and look at where the MAP cursor rests at idle and increase those numbers (1.2 lambda = lean, so add fuel till you get closer to 1.0 lambda).

Glad to hear you got it up and running though, now is the fun part

[A80Avant]

Bram, start a thread we can write on.
make sure you keep EGO correction OFF for now,and as marc said, set the VE table @ idle rpm to the numbers that will get you to lamda=1

do that with a warm engine, so that once you have that sorted you can mess around with the warm up enrichments at a later date

[Bram]

Hi Bram,

you can ignore the misfire light, its effectively meaningless.

For whatever reason you might have a slightly different VE due to different vacuum at idle than the basemap I supplied. If your fueling is sensible through the rest of the map other than at idle, go into the VE table and look at where the MAP cursor rests at idle and increase those numbers (1.2 lambda = lean, so add fuel till you get closer to 1.0 lambda).

Glad to hear you got it up and running though, now is the fun part

OK, I will try that! Thanks Marc.

Your quicker responding on S2forum then my email to you personally, so that is a good sign for all of us

[A80Avant]

oh nice, for a minute there i thought i lost the thread alltogether!
haha

[Bram]

ok, I adapted the VE table as suggested and once the engine reaches a temperature of +90 degrees C the lambda goes to 1.02 - 1.04. This should be ok right?
Also for some reason EGO is ON now, but I can not remember I set it on. Can this happen automatically?

Now I have to fiddle with the cold engine start parameters

[a4kquattro]

ok, I adapted the VE table as suggested and once the engine reaches a temperature of +90 degrees C the lambda goes to 1.02 - 1.04. This should be ok right?

yep.

Also for some reason EGO is ON now, but I can not remember I set it on. Can this happen automatically?

the "EGO ON" light can come on even you disable your wideband correction. The way I do it is in settings->wideband settings. You'll see two fields in there: rich limit and lean limit. to disable closed loop set rich and lean limit to 0. to turn it back on, try 10 for each.

[Bram]

But is it a bad thing dialing-in the VE table with EGO jumping ON, or is it not of any influence?

[A80Avant]

EGO should be OFF when you first put in the initial settings so that you know what is happening more or less with the engine. EGO should go basically on after most of the VE map is already done.

i usually input lean/rich limit 15% but when i want to set it on OFF,i just dial in the start of ego rpm : 7000rpm
that way it never comes on

[a4kquattro]

EGO should be OFF when you first put in the initial settings so that you know what is happening more or less with the engine. EGO should go basically on after most of the VE map is already done.

i usually input lean/rich limit 15% but when i want to set it on OFF,i just dial in the start of ego rpm : 7000rpm
that way it never comes on

yep, that works too. the way I described above will still show "EGO ON" in megatune but it wont actually do anything with rich and lean limit set to 0. The way you describe would probably prevent the "EGO ON" light from coming on as well.

[a4kquattro]

But is it a bad thing dialing-in the VE table with EGO jumping ON, or is it not of any influence?

Off. you do not want the wideband correction influencing your decisions on changes to the VE table. You want to see what the ecu is calculating for a required fuel injection quantity and the result of that calculation without any closed loop correction, so that you can bring the 'uncorrected' numbers as close as possible to the target (see the Lambda table for the targets you want to hit).

A good strategy is to display both lambda and lambda target as gauges on the main screen so that you can try to get the gauges to match throughout the power band as you tune.

[Bram]

OK, that makes sense to me. Cheers

[Bram]

OK, I tried to start the car and it works, but now I noticed the idle is very bad with lambda 1.25. Once I start revving higher the red dots disappear and lambda goes back to 1.0. I see on idle all red dots lighting up in megatune and warning like miss-fires in the bottom right red box

Now Marc told me he used in my config 630 ccm @ 4 bar FPR, which should give (according to my calculation a req-fuel value of 6.49 * ( 2226 / 5 / 727 ) * 0.75) = 2.98
Now I see that Marc set my req_fuel value to 3.8, which seems to be really much more then I calculated using 75%. Marc told me he took the 630 ccm @ 4 bar FPR into account.

Anyone has an idea what could be wrong?

Marc,

Still I doubt if the default calculation of req_fule setting is correct. Should I set it to 100% instead of 75% as in the calculation above? 100% should give me a req_fuel of 3.97

[A80Avant]

Bram, setting it at 75% will give you a wider amount of numbers to use in the VE table before a big change in fueling occurs.

here is an example:

you are @ 100kpa @ 3000rpm and have VE=95 which gives you a lamda of 1.00

Say you wanted to have there a lamda =1.01 so that you have better fuel economy
You would then alter the VE from 95 to 94 and recheck.
The 94 value could take the lamda to 1.02 !!! So then you wouldnt have a number to use between 95 to 94 to give you the 1.01 lamda that you are after. Of course that can be dealt with in the end with EGO correction, but the point is to be able to have a fueling map that can be very customisable and easily achieve the goals you are after.

By making the reg_fuel @ 75% you get to be able to use more values from 0-255 on the VE table to customise your table. On the other hand, having the 12x12 tables makes it less needed,as vems would have to cover the gaps between the values anyway,but as i said, you will find that you will need to have minor changes done on the VE table sometimes and that can be achieved with an elaborate VE value range.

Mine unforuntelly is not that elaborate at the moment but it does the job. Once i change the injectors i plan to do that