Fueling and outside air temp

[xonelith]

This is probably a dumb question, but here goes anyway.

It's around -10*C here and my car has gone from 500km per tank of fuel to 300km. In warmer temps, my afr's are close to 14.7 at cruise. It seems, due to the colder weather, my afr's are down by 1. cruise is around 13.5-14 and at WOT it's at 12 (instead of my commanded 13). I understand that due to the denser cold air, more fuel is required, but shouldn't I still maintain a 14.7? Or is this error in the wb?

If I lean this out, will there be an issue? I'm still somewhat new to the whole tuning thing, so is there somewhere that I can adjust the afr's based on outside temp? or is it all based on IAT's? Would I just adjust the afr's through the IAT table?

I don't know if this was a problem when the car was stock or if this is because I messed up my IFR table when I installed larger injectors.

Thanks!
-xon

[Dirty Howie]

Hey I think its a good question !!!!!!!!!!

Waiting to hear the replies.........


DH

[xonelith]

Is this that dumb of a question...LOL. Can anyone shed some light on this dim bulb?

[Bill@HPTuners]

where are your trims sitting at?

I know you have a cam.

Generally though maf & o2's or in your case the single 02 should always be trying to keep you around 14.7:1

[MMGT1]

Are you seeing this while your coolant comes to temp? Just wondering if the decay rates are coming into play with the colder temps?(Start up and timers)
And is your IFR table set to 4.30?

[xonelith]

where are your trims sitting at?

I know you have a cam.

Right now they are all over the place, moreso than when they were in the summer months. I have done zero tuning in the cold weather (so I expect things to be off).

Generally though maf & o2's or in your case the single 02 should always be trying to keep you around 14.7:1

I expect that I should still be aiming for 14.7, and that's the answer I was looking for. I will tune it back to 14.7 for winter and retune for summer.

Which goes to my next question, is there somewhere that I should be tuning that will adjust for the colder temps, based on outside air temp? or do I just tune based on IAT? I know there is an adjustment table for the IAT's.

Thanks!

[Bill@HPTuners]

if your running in closed loop the computer should always be aiming for 14.7:1

[redhardsupra]

it doesn't matter what control system it's using (open or closed loop), or even what airflow model we're using (MAF or SD), you end up with airflow number. then through AFR and IFR you get pulse width for it.

so whatever you have your targetAFR set to (whether it's OLFA, PE, BE, or just plain old stoich) it should be achieved, unless your sensors are dead/near-dead/dirty, or the data in the tune does not represent reality (like injector flow calculated from an assumed, not real fuel pressure).

the biggest influence of outside weather is temp and pressure. they both contribute to air density, thus air mass calculations. fuel temperature is another thing--fuel atomizes differently at different temperatures. that changes completeness of mixture burn changes, thus AFR will change as well.
that's why i say that for good VE tuning, you need to first bring the full car up to temperature, not just watch your coolant temp. usually after 15-20 mins of driving around, everything stabilizes and AFRs are much more consistant. try it sometimes, do a VE scan with the system still warming up, and then another one without changing anything else once it's warm. they will be quite different.

[Billf6531]

redhardsupra, you hit the nail on the head. Wait until the oil temperature stabilises, then tune. It takes considerably longer for the oil temperature to settle out than coolant temperature. Stable oil temperature means that the block is up to normal temperature, and that includes the head, whose temperature has the maximum influence on combustion efficiency.

[MMGT1]

Tim, can our model monitor oil temp? I scan for coolant and trans temps(x2,factory sensor and gage) but not oil. Only pressure. Do we need another gage in the car??

[Bob Wiley]

I was also wondering about oil temp monitoring (I'm about to order the software and am curious). I assume it does since Bill stated to wait until the oil temperature stabilizes. Is this correct?

[Bill@HPTuners]

its vehicle sensor dependant...if the vehicle has an oil temp sensor you'll probably be able to monitor it...few do though.

[xonelith]

AFAIK, we cannot scan oil temp, as we don't have the sensor.

I think, after about 15min though, the oil temp should be ok.

[MMGT1]

Thanks Tim, wanted to make sure there wasn't a table in there somewhere, but if we don't even have the sensor...hahahahh. Thanks bud.
Paul

[S2H]

This is probably a dumb question, but here goes anyway.

It's around -10*C here and my car has gone from 500km per tank of fuel to 300km. In warmer temps, my afr's are close to 14.7 at cruise. It seems, due to the colder weather, my afr's are down by 1. cruise is around 13.5-14 and at WOT it's at 12 (instead of my commanded 13). I understand that due to the denser cold air, more fuel is required, but shouldn't I still maintain a 14.7? Or is this error in the wb?

If I lean this out, will there be an issue? I'm still somewhat new to the whole tuning thing, so is there somewhere that I can adjust the afr's based on outside temp? or is it all based on IAT's? Would I just adjust the afr's through the IAT table?

I don't know if this was a problem when the car was stock or if this is because I messed up my IFR table when I installed larger injectors.

Thanks!
-xon

I dont know if it exists in the vehicle you drive...
bt on some v8's theres a table called charge temp bias...
older years it doesnt do jack shit...newer years it helps control the bias of your IAT to ECT...
what this equates to is a pretty drastic difference of fueling in hot and cold weather...
so seeing a difference of 1 afr should show you that your vehicle is not correcting for the temperatures as much as it should be..


correct that table and your fueling will be corrected as well...
this table becomes even more important for people that run SD as they have no MAF to help calculate the airmass...

to tell if your wideband is going bad you should look at it in the scanner chart view and it should be reasonably consistent...if it looks like somebodys heatbeat then it might be time to change it out...it shouldnt jump super far from one instant to another...its gonna zig and zag a little... but not several points over a split second unless you go fro cruise to WOT..then you should see a good jump..or if your VE/MAF tables are out of whack it will be jumpy...but if VE and MAF are fairly smooth then the WB should be reasonably smooth as well..

[EC_Tune]

Is this that dumb of a question...LOL. Can anyone shed some light on this dim bulb?

Great question actually. For operation other than closed loop, you will want to alter the Open Loop AFR table to achieve the proper AFR for the outside temps. As you said, you did the tuning during warm months so naturally the cold temp stuff is a bit off. Once you go closed loop the system should adjust back to 14.6 AFR via your wideband. If not then maybe o2 sensor issues?
You do want to be at a richer AFR when cold (especially around Zero F) probably in the Low to mid 13's with your cam. Cam's seem to need additional fuel when the engine is cold (there's probably a physics lesson in there ). You can make a histogram to map out the WB AFR vs the Open Loop AFR table. Then make adjustments based on your "target" AFR not necessarily what is in the table as it will be richer or leaner than your "target".

[Russ K]

Doug

His car is a V6 Grand Am, so no open loop table.

Russ Kemp

[EC_Tune]

Dang...