Stupid long overdue question - tuning fuel map.

[kengeroo]

When tuning the fuel map (with O2 sensor offline) do you want to tune to what you would expect under normal driving ?
i.e. when cruising AF = 14.7'ish,,, under load richer, etc.., etc...

Or would you want to tune the map to be a little richer and let the O2 sensor bring it towards 14.7 if appropriate ?

thx

[nimblestix]

I could be mistaken here as i only really started researching tuning this year, but 02 feedback is for idle and cruise, wot should be tuned to a set value. Rpm x load . so if I remember correctly you are on a PFC? You would power tune with o2 feedback off, then enable and touch up the cruising/idle area of the map. Although some tuners I've talked to would only tune the power area then just re-enable o2 feedback and send the customer on their way.

You can run with o2 feedback off entirely and have the map tuned to suit as well.

sent from a galaxy far, far away

[kengeroo]

yep power fc,,,
and yep O2 sensor for idle and cruise,,, but when tuning,, would you aim for 14.7 in those areas of the map (idle and cruise),, or aim for a little richer than 14.7 ?

[nimblestix]

I like cruising around 14 personally. But standard OEM I think aims for around 15.. 14.7 will be fine as long as it Richens up before heading into boost.

sent from a galaxy far, far away

[NoLimit0596]

Idle cruise 15-14.7 (Higher duration cam need to be more rich to idle correctly)
During spool up 13.5 - 13.0 higher than 5 psi 12.5
full boost 12.0-11.0

But each tuner have their way to tune a car and engine have too their characteristic

[Dragon Humper]

Its best to just leave the O2 feedback off. Most tuners in the PowerFC world just leave it disabled after the tune is ironed out with a wideband. I was always curious why mine were disabled on my car from Japan, I just thought that the car was run on Leaded fuel but as it turnes out, the O2 correction on the FC is pathetically slow close to useless. With the Djetro it is much easier because the vacuum #s can be used to fine tune the mix at idle and cruise. I have personally witnessed the vacuum go steadily higher and higher at a steady state of cruise while the PFC looks for the leanest mix it can get away with. With the Ljetro Im not sure how you could achieve the same thing.



Jon.

[Skym]

Best advice = talk to a tuner.

[nimblestix]

+1 ^ we can all give you advice but really just talk to whoever is tuning your engine. Ask them all the questions you have and if they're reluctant to answer or are unsure then go to another.

I'm definitely not qualified to give much tuning advice, if any. Just talking from my own experiences.

Good luck ken!

sent from a galaxy far, far away

[Dragon Humper]

So who in the lower mainland is good with the FCs then?


Jon.

[Velders]

I don't have any experience with Power FC, however...

Short Answer: Use your Wideband to tune to the AFR you want the engine to run at.

Longer Answer: If I'm not mistaken the Power FC Fuel map for L-Jetro is just correction factors for the MAF calibration curve. The map has values of 1.00 which use the airflow values in g/min from the calibration, greater than 1.00 gives more fuel, less than 1.00 gives less fuel. If you intend to use the narrow band sensors for 02 correction it is important you tune as close as you can to your target of 14.7:1 (assuming typical pump fuel). Anytime you want to be richer than this (outside 'cruise') you don't want O2 correction turned on. This is because narrow band sensors are only accurate within a small range of AFR values centered around 14.7:1. In fact 13.9 to 14.7 accounts for about 65% of the typical narrow band sensors voltage range.
So if you aim for an AFR much richer than stoic, you will very easily be outside the O2 sensors range and it will have a difficult time correcting.

[Dragon Humper]

There will be a load cut-off in the FC for the ECU to ignor the O2s. With the D its at a certain throttle opening combined with close to atmospheric on the MAP. With the L it will be a g/s cutoff combined with throttle opening.



Jon.

[Velders]

So Jon, does the D-Jetro PFC use a blend of TPS and MAP for the fuel map load source? I've been curious about that for a while.

[Dragon Humper]

Most ECUs will use several maps to extrapolate load. TPS vs RPM, TPS vs MAP, MAP vs RPM...then combine all those to come up with a load value. With the Commander on a Djetro you can only adjust INJ vs LOAD but I think with the DataLogit you can mess with it a bit further (ie: tweek the TPS vs MAP to delay enrichment for better fuel economy off boost). I wish I would get off my butt and get the Logit to really play with things because the Commander is painfull. I am more acustomed to tuning suites like LT1Edit and HP tuners for GM ECUs, you have about 500 parameters to play with there (most are for automatic trannies though).



Jon.

[Velders]

Ahh yeah okay, I was interested in how PFC handled it. Yeah the modern ECU's have an alarming number of parameters, thankfully for performance tuning most of them don't need to be played with.