What controls fuel at WOT?

[Jonas_R]

I'm I right in assuming that the fuel map and the FPR is the only thing controlling fuel at WOT?

My car seems to be running rather rich at the moment, and it where not before. I'm seeing AFR values as low as 10.2 I think.

Nothing has changed so I'm thinking something has gone wrong with the fuel pressure.
I'm getting some equipment, so I can check what it is, but running 7A FPR so I should see 4 bar absolute at fuel rail?

[S2central.net]

There is also compensation for air temperature so that might explain the extra fuel you are seeing - that is quite a jump though. Could be a mistake in the mapping maybe if this is first hot weather running you have done... You could prove that by faking a colder air temp signal into ECU of course - if that alone makes for better mixture then your map needs another tickle.

[Jonas_R]

Air intake temp is around 20C according to VAGCOM so I dont think that it is. That is maybe 10 degrees hotter then when the car was mapped. But would it over fuel that much?

But if fuel pressure is 4 bar, then it can only be air temp or fuel map correct? I mean not any other sensor that can mess with the fuel right? Lambda sensor is only for part throttle right?

[S2central.net]

Closed loop with lambda is idle and part throttle - yes.

But my suggestion (hint hint) for you to fake IAT sensor - watch air temp drop to 10 degrees from 20 real world ambient - then see what your mixture is like at WOT... Depending on how comp is setup - this *might* account for the difference - either way you will know for sure.

[A80Avant]

Apparently you are right, motronic is actually using specific fuel map for WOT and possibly part throttle that needs to be more than a narrow band can be specified for.

However,after installing my standalone kit for the wideband, i noticed that on WOT from 5th gear and on, mixture was going 0.70 and even less.

When i tried the same with VEMS the car was stumbling hard and coughing,as the mixture was too rich. Im now using vems with 1.9bar of boost holding about 1.7 to the redline and my mixture is ok with about 0.80 lamda and temperatures are also a tad lower than motronic.

[Jonas_R]

Paul: How would one fake the air intake sensor? I'm thinking a resistor could do the trick, then look at the air temp plot from sjm autoteknik.

Could a faulty air intake sensor cause this?

[Jonas_R]

A80Avant: Are you doing the mapping of VEMS yourself? And how difficult would you say it was to get it going?

I'm really considering using VEMS when I install my K26/K27/K29 over the winter.

[S2central.net]

Paul: How would one fake the air intake sensor? I'm thinking a resistor could do the trick, then look at the air temp plot from sjm autoteknik.

Could a faulty air intake sensor cause this?

Yeh take a variable resistor and play with VAGCOM logging air temp with engine running - adjust for say 0 10 and 20 degrees even if real temp is 20... you may get some knock at very low fake temp so be careful... This is not an ideal test but should something.

[A80Avant]

Yes, i did. I had some help for the basic spark table which was the most difficult part to make,as you have to have a dyno to do it properly,but i play it safe and dont overdo it to avoid knock anyway.

The good thing about VEMS is that you will always find help among other users that will give you their basic tables to start with.To have as a starting point that is.In the end you must have a table that fits and suits your engine

[GazzaG60]

a proper road map should be done on the road and not the dyno.

vems is not too bad a systme to start with. lots of quick wins.

agree regarding maps. think not one of us has exactly the same setup so tables of others need modifying usually more so on spark.

[Jonas_R]

Just created this little baby.
0-10Kohm but it is adjustable within +-5ohm.

So gonna try that and see if it helps.

[Rocco]

Jonas, with 10´2 AFR or lovwer your car works well??? it is too rich mixture true??

i remember whem changed my RS2 injectors to the bosch greens 440cc/3bar..... with the same 7A FPR... i had 9´3AFR or lower under full acceleration and the cars does not work well nothin the nothing,too rich.. ..

i think that 11´2 AFR will be much better under full acceleration



about 7A fpr...., i had tested it with a custom pressure gauge in the fuel rail and only gives you 4 bar under full acceleration, in normal drive you must see only aroung 2´5bar in fuel rail

[AUDIS2avant]

you can always go TO rich, ideal for 98-99ron should be 11,5-12 afr, if you have arr 10 afr that´s **** rich.

[prosty]

Check your airfilter, if you're not getting enough air the mixture gets too rich!

[Jonas_R]

I know it is to rich. But I need to find out what causes this, wrong fuel pressure, bad air temp or fuel map