VEMS: the unstoppable pulsing idle

[loxxrider]

oooooh, I just realized you were talking about the lambda table and not the VE table.

Forget about the lambda table for tuning. Just set that at the values I have. You want to be tuning that stuff with the VE table! I have NEVER ever touched my lambda table and that is after three different injector sizes and two turbos.

[A80Avant]

what are you using the car for?

lamda table is vital for passing emmitions and having fuel economy on everyday driving!!!

[Billman]

Are you using the vems wideband lambda for EGO correction?

[loxxrider]

yeah, I don't use EGO correction which I didn't think about...that would make lambda table more important for you. I'm not really a believer in EGO. Sorry for the mis-communication there. Lambda table will definitely be more important for you if you are using EGO!

[Billman]

It is not about believing! Think about it: you make your VE table for an amount of load let's say on idle. Then you turn your heater on. Your VE table will need adjustment in Oder to have the right fuel.

In order to compensate now I suppose you are always rich with fuel but that is not very efficient, washes the bore etc.

Ego correction is main feature in all ecu systems (factory or aftermarket).

[loxxrider]

It is not about believing! Think about it: you make your VE table for an amount of load let's say on idle. Then you turn your heater on. Your VE table will need adjustment in Oder to have the right fuel.

In order to compensate now I suppose you are always rich with fuel but that is not very efficient, washes the bore etc.

Ego correction is main feature in all ecu systems (factory or aftermarket).

I just don't find it necessary if you have a good tune. I have plenty of cells around idle such that the car stays well above stoich under all conditions until the car gets into boost. I have yet to see a single instant under 100kpa where its under stoich under static conditions (I.E. not accel enrichment).

As the load changes, so does the vac level which is why if you have plenty of cells down in the idle range you will be good to go.

[A80Avant]

so basically you have a car that runs rich all the time and cannot pass emissions. Even on IAT changes the VE cannot remain constant. It is not about making sure the car does not go below lamda =1, it is about making the best of the ability of the engine and sometimes the engine runs better and produces more torque on slightly leaner conditions as well.

in my car if i leave the idle area outside of the EGO regions, then i have to use the the fuel enrichment table to make sure it always stays for lamda =1 to pass emissions but also to keep the idle stable. At the same time, ego correction makes sure it keeps the cruising area of the map always within limits.

You can make an excellent tune for a specific 10-30C IAT difference which is how the car usually runs most of the times, but it will go off the VE bin you have once the IATs become hotter or colder from that margin.

My view of tuning the car is not to make it rich on all areas so that it never goes below lamda =1. I actually have lamda =1.08 on certain rpm and kpa areas to make some fuel economy.

[Billman]

I use EGO correction from 700 rpm and it runs fine with steady idle (ISV off).

[loxxrider]

so basically you have a car that runs rich all the time and cannot pass emissions. Even on IAT changes the VE cannot remain constant. It is not about making sure the car does not go below lamda =1, it is about making the best of the ability of the engine and sometimes the engine runs better and produces more torque on slightly leaner conditions as well.

in my car if i leave the idle area outside of the EGO regions, then i have to use the the fuel enrichment table to make sure it always stays for lamda =1 to pass emissions but also to keep the idle stable. At the same time, ego correction makes sure it keeps the cruising area of the map always within limits.

You can make an excellent tune for a specific 10-30C IAT difference which is how the car usually runs most of the times, but it will go off the VE bin you have once the IATs become hotter or colder from that margin.

My view of tuning the car is not to make it rich on all areas so that it never goes below lamda =1. I actually have lamda =1.08 on certain rpm and kpa areas to make some fuel economy.

Something is getting lost in communication here...my car NEVER runs rich at all. Its between where vems doesn't even read lambda anymore (what is it...over 1.22 or so that it wont read?) and 1. So if anything, its quite lean! If I had a cat, I'm confident it would pass emissions without a problem.

If it goes out of the normal VE bin I'm in and goes to the next one, I have that next cell tuned for that too. I don't need the computer to tune for me.

[dkw_dude]

You can make an excellent tune for a specific 10-30C IAT difference which is how the car usually runs most of the times, but it will go off the VE bin you have once the IATs become hotter or colder from that margin.

Off topic but there is a map for MAT/TPS fuel enrichment. Found as my car was running richer at colder outside temperatures (-22°C today ). The enrichment map was preset with values that was too high, and the mixture got a bit rich. Adjusted the values in the map and all is good, will check it again as (or if?) it gets warmer.

[A80Avant]

i wont go into this any further as you fail to see the big picture. any car in the car industry uses nowadays wideband lamda to keep the car operating under all variety of circumstances and as a second feedback along with their MAF/map sensors. on vems you have the map sensor, ve table and wide-band. to me it seems unreasonable not to use everything to keep the car running always under ideal conditions. the fueling table goes without saying that it needs to be tuned first, but in no way covers all circumstances and that can be easily identified. If you are running lean as well, the wideband will allow you to correct on those circumstances. the VE table is tuned for the usual iat's that the car runs in, so that is why you get the impression that the car is always running perfect. If you have 20C ambient temp 90% of the time, see how your car runs if it goes to 40C or 0C, and let me know if it will still run ok with the ego OFF.

mat/tps enrichment table can also help but does not allow you to fully run without ego correction in my opinion.

back to the idle topic though..

[loxxrider]

For what its worth, I probably will try the EGO out at some point, I just haven't found it necessary yet. I made my tune for this car at 32 C and for the past few weeks, its dipped to around 0 C. I was slightly concerned with the temp change and monitored my fueling and saw no noticeable changes. I suppose my MAT table is nicely set up. Again, I'm not saying EGO is useless, just that I don't trust it under boost and also haven't needed it yet. Its OK, we can agree to disagree. Back to the topic indeed.

[A80Avant]

i never said anything about using it under boost. Some do, i dont. i use it only for anything up to 120kpa. 0.2bar is too low to be a problem anyway for the I5

[loxxrider]

I can definitely agree to that point.

[ranz]

with the only issue of sometimes causing a minor drop on several occasions, but never stalling.

What is your PID controller D value? it should be around 150 and no more problems I quess