mx594

iTrader: (4)

Can someone better explain open loop fuelling to me? I am currently N/A with a UTEC, so I am running in MAF mode. However I don't really understand what activating open loop fuelling actually does. In the UTEC manual it says that the UTEC uses a background table of A/F values which is not editable by the user. Does that mean that the UTEC will use the stock O2 sensors to self adjust to reach the target A/F values listed in the hidden table? So it will essentially tune itself (for fuel anyway) to accommodate various NA mods?

Wouldn't that mean that it has to re-learn every time you start the car? Or does it somehow save the fuel values from the last time the car was run?

And why can't the user edit the target A/F table? Is there one ideal set of A/F targets for all N/A cars, or is open loop fuelling simply an option that is useful for those who just want to "plug it in and have it work"?

SmallTuner

iTrader: (2)

open loop is an option for FI cars

so, no need to use it with N/A cars.

Jime

That is not correct. Open Loop Fuelling is for N/A and FI.

Speed Density is mainly for FI but I also use it on my N/A setup.

The difference with open loop fuelling is that it uses a fixed map and you adjust + or - to get the tune you want. It will not change EVER. If Open Loop Fuelling is off then you are in Piggyback mode which will change as the stock ECU changes. You also + or - as well but there is no fixed map it just adds or subtracts from the stock ECU. You are really editing the fixed map when you + or - the Open Loop map.

You want to use Open Loop Fuelling.

mx594

iTrader: (4)

So the UTEC wont self tune in open loop? The TXS manual is confusing, it makes it sound like the UTEC uses a background table of air/fuel ratios that it uses as a target to adjust itself until the desired AFR is reached.

Hypothetically, If I am in open loop, MAF mode and I put a 1.5 in the 5000 rpm 70% load column, what exactly am I adjusting by 1.5? Am I increasing the injector pulse by 1.5%, or am I changing the target AFR in the hidden table by 1.5% richer (i.e. 14.7 to 14.5) or am I increasing the MAF voltage reading by 1.5%?

You say that open loop is based off a fixed map, so it will never change. Will open loop fuelling then eliminate the problems I have heard about with the "uncertainty" when tuning that is due to the stock ecu fuel trims? I read somewhere on here that the stock ecu (when the UTEC is in closed loop mode I assume) will try to compensate for the changes you are making with the UTEC by using fuel trims, effectively fighting against you when trying to tune...which makes attaining the desired AFR like trying to hit a moving target - one day your tune will be good and the next day the stock ecu does something different and your tune is off. Am I understanding that correctly?

mx594

iTrader: (4)

Well I would, but I don't have a wideband yet so I just have the UTEC set to position 0. Too bad the UTEC can't output data from one of the FOUR stock oxygen sensors, otherwise I might be able to do some tuning.

Jime

I repeat "Open Loop Fuelling is based off a fixed map and it will never change." The UTEC assumes control from the stock ECU so it cannot change. The timing is the same, the UTEC directly fires the coils with no intervention from the stock ECU.

The stories you read about the tune changing in Open Loop are FALSE.

Jime

You do not want to tune with the stock sensors. Get a wideband.

athenG

iTrader: (2)

I mainly tune using speed density so I'm not really familiar with NA and MAF pull down. Are you talking about using Open Loop and MAF for fuel mode? I have always thought that using MAF pull up/down is just basically scaling the stock ECU MAF voltage. With Speed Density then it is a totally different story because you dont scale any value but instead you actually us IPW so you are really in control of the injector.

NETSHARK

The different between running open loop and not is that when you`re not running with open loop the UTEC only fools the ecu with adding and subtracting fuel (MAF Voltage) at the given loads but each time u press the pedal different conditions applies and the Factory ECU Decides what to change add to that the change from the UTEC. so bad stuff might happen here more than on the Open Loop.

But When using Open Loop it will make the UTEC have 100% control on the injectors (like What Jime just posted in RED above) hence why ur not hitting the rev limiter if ur on a 03 or a 04 Z because UTEC is the one on control now so if u wanna change the rev limiter you must enable Open Loop Fueling mode.

Speed Density is more used for Forced Induction because the MAP (Manifold Absolute Pressure) Sensor will reads how many PSI`s entered the Intake Manifold to add whatever Fuel should be added based on that amount of boost, the MAF is limited to small amount of boost 5.5 or less PSI after this number the MAF will not be able to read because of the excessive pressure.

On the other hand the MAF just measures how much air entered the engine by the MAF Voltage (Basically its all about the resistance in the MAF but i dunno how to explain it very well lol) the more air entered the more voltage will be generated, the less the air entered the less voltage will be on the MAF.

so its just a way to measure how much air is entered so the ECU can send the correct fuel related to this amount of air.

athenG

iTrader: (2)

I know using MAF pull up/down is just basically -/+ % on the MAF volt that it reads then it send the modified voltage back to the ECU so in reality it is still the ECU that is driving the injector right? I believe that our ECU has its own table that it build overtime and eventually make adjustment on the tune but I could be wrong.. I didnt really care coz I'm FI'd and I use speed density.

Quamen

iTrader: (14)

Is there any MAF's out there that will max out at a higher psi that could be swapped in allowing you to run higher boost levels out of speed density?

Jime

That is true if you aren't in open loop. However in open loop regardless if you are using speed density or MAF the tune never changes.

I have used both speed density and MAF in my N/A car and there is no difference for racing but part throttle in speed density takes a little longer to tune.

athenG

iTrader: (2)

Do you mean upgrading your MAF and still run Speed Density? Speed Density read pressure so it doesn't use a MAF sensor.

NETSHARK

GTM Sells a Programmable MAF didn`t read more about it but just noticed it on there website BTW as athenG said In Speed Density mode you need a MAP Sensor, the MAF is only required for the 0 Load Column.

Quamen

iTrader: (14)

I ment not using speed density. I am well aware that you can't use a MAF in speed density.

str8dum1

iTrader: (11)

any of those HPX maf's http://www.350zmod.com/HPX-MAF-Senso...vq35demmaf.htm won't max out. BUT.. i dont know how you'd calibrate it in the UTEC, or if it drops in and is plug and play. GTM does a lot of 'turn key' setups using that so they would prolly know.

Quamen

iTrader: (14)

I am going to have to look into that.