dastallion951

Yes but at 20% throttle the throttle body is barely cracked open, and usually at that spot of about 20% your in cruising timing range, so usually your air fuel is tuned around stoich for that because the cruising range in your map is right below idle range. So AGAIN if my wideband is showing stoich readings around 14.7-15.2 while im cruising with the throttle very light tell me how im using more fuel again. I can understand if im boostin more then 10 psi, yes my air fuel will start to tip rich, but if im barely going into boost around 5 psi to pass people on the highway if that, then the air fuel readings im getting is still around stoich. And yes I understand the fuel pressure regulator works on a 1:1 ratio. Im just stating what my car does with light load on the throttle. Raptord so if you have no pushing of throttle what happens you slow down, if you have LIGHT throttle IE 20% or so on the throttle your maintaining your speed while keeping your car in vacuum not boost therefore your air fuel ratio if your cruising should be around stoich readings.

Raptord

iTrader: (10)

You really don't get this, lol.

Anytime you're in closed loop, AFR will stay ~stoich. Yes. Idling will be stoich. Cruising 60mph in 5th will be stoich. Cruising 80mph in 5th will be stoich. But you'll need more throttle to cruise at 80mph than you will to cruise at 60mph. The air:fuel ratio will stay the same, but for it to stay the same the ECU will add fuel to compensate for the added air.

GTijoejoe

iTrader: (25)

I would like to state in addition to Raptord...to help you understand.. if you monitored your MAF voltage you would understand the increased airflow which the engine will compensate for to give you stoich reading. Its not dependent on 'throttle position' as when your engine is loaded differently at the same throttle position it will change how much air it will want to eat through you MAF...hence your MAF will not hide anything from you.
At stoich, more airflow, more fuel... less fuel economy

Butt Dyno

iTrader: (10)

* Walking
* Bicycling
* The bus
* Taxi
* Any other automobile on earth

dastallion951

Your right im not getting it because your not making sense, if your in 5th cruising in vacuum and the air fuel is stoich due to closed loop, so if its at stoich where are you getting added fuel. I can understand a small increase from cruising at 60- compared to 80 due to higher rpms thus a need for more fuel. Your not making sense, and im not an idiot when it comes to cars man. Sure I can understand what JoeJoe is saying about maf voltage, but thats only part of what the ecu uses to determine proper air fuel. If your staying at a consistent rpm in vacuum not boost, then the Maf voltage reading shouldnt increase. The maf voltage will only increase when air flow is increase through it and really the only time that happens is when you start to boost or go WOT where the turbo is pulling in a higher volume of air then when its just statically spinning due to the turbine gasses.

desiromeo812

iTrader: (13)

So you Admit that airflow will increase when you are 60mph vs 80mph? Think about it like this.. If airflow increases YOU have to add more fuel to it. In order to reach stoich the ECU will have to add more fuel as opposed to less fuel the less the airflow.

To add to this.. Stand behind your tailpipe and rev and hold car at 3k rpm... then rev and hold at 4k rpm.. at 4k RPM the exhaust will be more.. BECAUSE OF more air... more air needs more fuel.. Simple.. and also during this IDLE rev and hold test your AF should stay at 14.7.


I hope you get what Im saying.. 14.7 is jus a ratio.. thats all it is.

GTijoejoe

iTrader: (25)

I think some of your confusion is your misunderstanding of how the engine/drivetrain relate at a giving driving condition through the ECU and sensory.
Keep in mind for closed loop the ECU uses the MAF as the base, it really uses the 02 sensor and +/- fuel trims to keep your engine in stoich... hence closed loop control... because than you will get into the resolution the MAF has to actually control small finite changes and their correlation to AFR.
... but that being said, the MAF will never lie, if it reads higher, it has increased flow which surely the engine has to account for.

"The maf voltage will only increase when air flow is increase through it and really the only time that happens is when you start to boost or go WOT where the turbo is pulling in a higher volume of air then when its just statically spinning due to the turbine gasses"

This is what you don't understand, your statement is false and this is why.
As stated the MAF voltage will increase proportionally to airflow, this is true... what is not true is that the only time this happens is during WOT or boost. To put it into perspective, if your statement was true, than N/A vehicles would always have the same fuel economy no matter what until you reached WOT, and of course that wouldn't make any sense.
As your engine sees high vacuum in its manifold is a direct relation to how the engine is loaded through the drivetrain. Its a similar difference with engine loading between different gears, but to keep is simiple we are assuming you never switch gears.

So steady state 60mph on the high way driving your at -18mg on the vac gauge, of course stoich AFR... if I magically added 500lbs to your car...to keep 60mph you will start to see maybe -08mg on your vac gauge with same AFR.... but now you are using more fuel... maybe your thinking of course cause I just added more wieght to your car... but loading doesn't only change by weight, if you start climbing a small grade on the high way like 2-3%, this will also increase the load on your engine it will experience a similar event.. thus losing fuel economy.. so basically as you stated, same rpm, same speed, your MAF voltage will increase with loading.. even though your AFR didn't change.

Load is proportional to how much power the engine will need to output. So increased load, more power, which means its going to need more air and more fuel to get there... and this is even without WOT or going into boost, just completely forget you even have a turbo because its not needed to understand engine load vs fuel economy... all of this can still happen at a low throttle input.

I hope that clears things up, otherwise I'm not sure how else to explain it to you.

dastallion951

Yes desiromeo I understand I understood it the first time they said it, all i was defending was staying at a consistent rpm with the same throttle position in vacuum fuel will not increase, unless the rpms increase. Or boost is made, then yes fuel increases. I understand that, I also understand the ecu tries to compensate to stoich at idle and cruising rpms and speed. So thank you for trying to teach me something I knew.

thisxguy

iTrader: (17)

Get a secondary map tune for fuel economy / daily driving with 87 octane which will yield low power but saving gas and spending less at the pump :P

dastallion951

I did understand what you were saying, and what I meant by maf voltage increasing due to airflow is usually when you start to boost or go WOT in our cars. Whereas by cruising or light amount of boost the maf voltage will increase but not by much however it will increase fuel consumption. Obviously maf voltage will increase on an N/A car it has to if the cars ecu is gonna read that for air fuel adjustments. Yes I understand about the whole climbing grades will affect fuel economy, or heavier weight. But we werent talking that, I did understand everything you were trying to get across, and some of the wording from earlier posts had me confused, because these were clear out of the blue statements that didnt make much sense, thus me defending my statements which are true. Sounds like were all getting across the same message, in different wording.

Raptord

iTrader: (10)

Vacuum has to stay consistent as well. -10 in/hg will yield less fuel economy than -12 in/hg (in a fictional situation where all other variables stay constant).

Kracka

iTrader: (49)

To answer the thread title question:

"Straight to the dealership for trade-in!"

dastallion951

Obviously if the throttle position stays the same then the vacuum has to as well. Changes in throttle input will change vacuum, enough throttle input and the car will start boosting pressure. So like I said were saying the same thing in different wording.

kyoo

iTrader: (29)

lmao jeez

i just meant given air/fuel, more air, same ratio => more gas. pretty retarded i guess

Raptord

iTrader: (10)

Go up a hill without changing throttle position and tell me if your vacuum stays the same