Learning View Snapshots \ Discussions

[<GB>]

Definitely mechanical.

Vacuum leak for sure

Af correction at low load and knock at low load / engine speed indicates lean out and thus knock

Don't vaccum leak cars normally show a positive number in the first AF Learning range (idle and putt putt) due to more air entering the intake after the MAF causing fueling adjusting up at the MAP sensor?

I thought that was a tell tale sign.

this, if you check my lv on the first page the one after springy was done with a vacuum leak and my A/F table was positive, this kinda proves your point here bruce

[dr20t]

Dirty MAF..

I can't tell if you're being sarcastic or serious

Af correction can be positive or negative

Gb and Bruce :

Depends on where the vacuum leak is.

Negative indicates air fuel ratio is being adjusted down. So afr would go from say 10:1 to 11:1, because the maf is seeing less air than tuned for so will compensate by pulling fuel accordingly

If vacuum leak is in the manifold then it means maf is registering certain amount of air, motor is trying to get to stoich 14.7:1, but because air is being blown out after the maf that more fuel than required is being pumped in

The 02 sensor in closed loop then sees too rich a mixture and pulls fuel, causing lean out and knock at low load

Positive correction means higher afr because the system is too efficient - ie needs less fuel to get to same stoich 14.7:1 and therefore will subtract as requested

Boost leak before maf is the reverse

[<GB>]

Dirty MAF..

Negative indicates air fuel ratio is being adjusted down. So afr would go from say 10:1 to 11:1, because the maf is seeing less air than tuned for so will compensate by pulling fuel accordingly

Positive correction means higher afr because the system is too efficient - ie needs less fuel to get to same stoich 14.7:1 and therefore will subtract as requested

these sound the same? positive and negitive pulling fuel?

[bass_straitener]

Dirty MAF..

I can't tell if you're being sarcastic or serious

Af correction can be positive or negative

Gb and Bruce :

Depends on where the vacuum leak is.

Negative indicates air fuel ratio is being adjusted down. So afr would go from say 10:1 to 11:1, because the maf is seeing less air than tuned for so will compensate by pulling fuel accordingly

If vacuum leak is in the manifold then it means maf is registering certain amount of air, motor is trying to get to stoich 14.7:1, but because air is being blown out after the maf that more fuel than required is being pumped in

The 02 sensor in closed loop then sees too rich a mixture and pulls fuel, causing lean out and knock at low load

Positive correction means higher afr because the system is too efficient - ie needs less fuel to get to same stoich 14.7:1 and therefore will subtract as requested

Boost leak before maf is the reverse

I think you may have it the wrong way around. My understanding is if there's a leak after the MAF under vaccum more air is entering the system. Pressure equalisation. Therefore more air than has been metered is in the intake system and therefore more fuel is added to reach stoich.

Under boost you'll run too rich due to the same principle as air escapes from the intake after it's been metered. Thus not making power.

An unclean MAF just screws with everything. Everybody go home and clean your MAFs tonight.

[<GB>]

vacuum leak after the turbo will be air being pulled in so more fuel needs to be added, this would be much worse when the throttle is closed if the leak is in the manifold

boost leak will force air out thus mixtures will go rich and fuel pulled out till off boost when the car goes back to vacuum or the throttle is closed

[bass_straitener]

vacuum leak after the turbo will be air being pulled in so more fuel needs to be added, this would be much worse when the throttle is closed

boost leak will force air out thus mixtures will go rich and fuel pulled out till off boost when the car goes back to vacuum or the throttle is closed

I agree with this too.

[<GB>]

i break the areas down too!

ie

the valves to the throttle body (high vacuum and boost)

throttle to the turbo (min vacuum and boost)

turbo to the maf (min vacuum)

[dr20t]

I see what you're saying and agree with gb's last comment but riddle me this:

Why does Ecu throw af correction out when you simply put a silicone inlet on and change to a pod filter?

There is no vacuum leak after the maf - but what happens to your af correction?

[bass_straitener]

I see what you're saying and agree with gb's last comment but riddle me this:

Why does Ecu throw af correction out when you simply put a silicone inlet on and change to a pod filter?

There is no vacuum leak after the maf - but what happens to your af correction?

You have your MAF sensor scaling based on amount of air travelling through the intake system. A small percentage of this air has to hit the sensor and travel up the tube to register and convert to a scalar and voltage which is used in calculating your fueling target. The IPW, compensations yadda yadda then deliver the exact fuel amount to reach that target.

When you decrease the resistance of the filter material, increased diameter of the tube, slip of the material used, minimise turbulence etc you are flowing more air quicker through the intake. The size of the tube leading up to the sensor remains constant however. You therefore have to add MAF scaling to compensate for the volume or actual air now passing around it.

If you don't, and more air than expected arrives at the MAP sensor the ECU adds fuel to reach stoich in CL and simply uses OL targets based on the MAF scale. The ECU compensation max is only 25% and therefore you will run lean on boost and rich on CL as the ECU cannot correct to that extent. Combine that with dodgy scaling from both factory and tuning you further reduce the compensation that can be made and are at risk earlier.

Hope this clarifies things a little.

BTW I could be wrong, I don't know everything unlike some...

[senator]

Bruce what intake are you using???

With your power levels would it be worth refitting the OE box too see if you maf scaling improves.

Regarding the whole tuner debate..... thank your lucky stars Matt doesn't hide and refuse service unlike the farken halfwit at Pulse racing..... even with a dyno tune and 4+ hours on a dyno and $1200 and 3 attempts to get the tune stable.......you're no better off.

[bigBADbenny]

I'm really happy I'm tuned and thus logging regularly:
Doing so has revealed an AVCS issue I might have otherwise missed...

[<GB>]

Got a learning view Ben?

[bigBADbenny]

I do but it's work in progress with that issue and another revision to be flashed... So...

[<GB>]

I posted mine with a vacuum leak!

[KiDo_Tuning]

I know why it's wrong... Ipw is smaller due to bigger injectors
U got a learning view?

ID1000's on pump fuel need the fuel meter multiplied by 1.82

Definitely mechanical.
Vacuum leak for sure
Af correction at low load and knock at low load / engine speed indicates lean out and thus knock

Don't vaccum leak cars normally show a positive number in the first AF Learning range (idle and putt putt) due to more air entering the intake after the MAF causing fueling adjusting up at the MAP sensor?
I thought that was a tell tale sign.

06 WRX is supposed to run -15 in most regions as they are designed for lean cruise with MRP compensations. Add heaps of fuel down low in MAF and let the ECU compensate That is a vacuum leak, a small one but it is present. Even with Process West CAI's on stock cars, the MAF is often at -15 despite the bigger housing!