[themyst]

Hey guys:

I was wondering if someone could help me out regarding this issue I'm having. As many of you east coasters know, the weather is frigid out there, so I would imagine that boost should skyrocket up to the max value in this weather with no ignition correction. The log is of a 3-4-5 pull shifting at 6000 RPM.

On my former 135i, I would see 15.6 psi / 31 ignition correction autotuned with no meth in HOT temps. In this case, I reset autotune adaptations, started my autotune figures at 15psi boost, 50% ignition correction, and after a few pulls, it dropped autotune figures significantly, to 14.2 psi / 77% ignition correction, although the aggression value stabilized at 2.0.

I filled up with the same Gulf 93 octane from the same station as my higher 135i autotune settings hit. I just got this car, and this is my second fill-up, both from the same station.

I have attached both a log and video of my run. Fuel Pressure as per Shiv's instruction, is just around 3.9 - 4.1V, which is within spec. boost looks clean, and ignition correction is cutting about 3 degrees of timing to ensure a smooth curve. Boost targeting vs. actual boost is a bit high though. I had this same phenomenon on my 135i (target 18psi, see upwards of 18.6ish psi) The challenge I'm faced with here is... what could cause this? Bad gas? Boost leak? (highly unlikely) A few ideas based on these logs would be appreciated. Thanks....

[NiVeDh]

I'm seeing a similar effect with my boost gauge - haven't done any logs yet. I set the max boost to 14 psi but it autotunes to 11.5 psi. Hopefully someone will provide some insight.

I also had a random weird situation where I lost all boost. The car would not go into boost at all. I shut the car down, checked my DVs and charge pipe and they were all fine, started it back up and that resolved everything. Perhaps related to this, when I switched maps one time, the "map display" screen stayed on for an abnormally long time (more than 30 seconds). My car has a mind of its own so I wasn't surprised.

[themyst]

Originally Posted by NiVeDh

I'm seeing a similar effect with my boost gauge - haven't done any logs yet. I set the max boost to 14 psi but it autotunes to 11.5 psi. Hopefully someone will provide some insight.

I also had a random weird situation where I lost all boost. The car would not go into boost at all. I shut the car down, checked my DVs and charge pipe and they were all fine, started it back up and that resolved everything. Perhaps related to this, when I switched maps one time, the "map display" screen stayed on for an abnormally long time (more than 30 seconds).

The good news is there doesn't seem to be anything wrong with my car. I just find it odd that the car would autotune lower in frigid conditions. It would autotune high in hot summer temps though. I'm think it might be the gas. Maybe i'll dump some race gas in there to see where I stand after this tank goes dry.

Never had an instance where I lost ALL boost though except in NA mode, that's definitely weird. I guess we'll wait for Shiv to chime in....

[NiVeDh]

Originally Posted by themyst

The good news is there doesn't seem to be anything wrong with my car. I just find it odd that the car would autotune lower in frigid conditions. It would autotune high in hot summer temps though. I'm think it might be the gas. Maybe i'll dump some race gas in there to see where I stand after this tank goes dry.

Never had an instance where I lost ALL boost though except in NA mode, that's definitely weird. I guess we'll wait for Shiv to chime in....

Not sure if it's the gas. I've been using the same gas I always use (Exxon 93). The temperatures here are colder too (30s-40s). Just last week when the temperature was in the 60s, my car was autotuning to about 13.8 psi as observed by my boost gauge.

[themyst]

Originally Posted by NiVeDh

Not sure if it's the gas. I've been using the same gas I always use (Exxon 93). The temperatures here are colder too (30s-40s). Just last week when the temperature was in the 60s, my car was autotuning to about 13.8 psi as observed by my boost gauge.

Cool, so I'm not the only one observing this then....

I mean the car pulls reasonably hard without meth. I could go back out there set it to 17psi and spray meth with no failsafe... but I can wait.

[OpenFlash]

FYI, when it gets colder you are going to make the same power at lower boost. If it gets really cold, the Procese applies an IAT correction to lower boost. This is due to fuel system limitations at peak torque (3000-4500rpm). Nothing to worry about.

[themyst]

Originally Posted by shiv@vishnu

FYI, when it gets colder you are going to make the same power at lower boost. If it gets really cold, the Procese applies an IAT correction to lower boost. This is due to fuel system limitations at peak torque (3000-4500rpm). Nothing to worry about.

So just to clarify, in cold temps (such as 33 degrees ambient like tonight when I logged) autotune will actually lower boost due to fuel system limitations?

So once I get my flow sensor back and set to 17psi, it will peg the boost limit and autotune down into the 0.x range assuming all is well in this cold weather?

[caradd]

I just noticed a drop in mpg. I bet the gas stations have switched over to the winter blend.

[forza1976]

Originally Posted by caradd

I just noticed a drop in mpg. I bet the gas stations have switched over to the winter blend.

non sequitur

[OpenFlash]

Originally Posted by themyst

So just to clarify, in cold temps (such as 33 degrees ambient like tonight when I logged) autotune will actually lower boost due to fuel system limitations?

So once I get my flow sensor back and set to 17psi, it will peg the boost limit and autotune down into the 0.x range assuming all is well in this cold weather?

When IATs are moderate, between 20C and 40C (too lazy to concern to F), you will see actual logged boost to peak at the Debug byte 5 (autotuned boost) value. When you see it go extremely hot or very cold, there are corrections that the Procede applies to keep the engine safe. By 70deg C, actual boost will be 3psi LESS than the nominal autotuned boost value. Similarly, when IAT is 0deg C (32deg F), actual boost will be 1psi below. By -10deg C, it will be 4psi below.

So if your operational IAT temps fall into these two extremes, don't be surprised if you see a condition where your aggression level is lower than your aggression target and yet actual boost has not maxed out at your boost limit (ie, 17psi).

[Ilma]

Kind of makes sense that colder denser air at the same boost pressure is going to make more power......therefore more heat in the combustion chamber.

Also, many gas stations have switched over to their winter formulations, and I think this is showing up on a lot of people's datalog values in a negative way, so pump octane may be a factor as well.

FWIW I am also running 14 psi on a mostly stock setup and find that 75% ignition correction seems to give me good timing curves.

I think there is something to this colder weather requiring less boost/or more ignition correction since a number of members are reporting similar symptoms.

[OpenFlash]

Originally Posted by Ilma

I think there is something to this colder weather requiring less boost/or more ignition correction since a number of members are reporting similar symptoms.

Yep, that's pretty normal. Combine dense air charge/more power with reduced octane/higher fuel demands and you get what we are seeing. No biggie.

[Clap135]

I am not seeing this with cold IATs.
dci/dp/fmic, high 20s outside and my boost shoots up to my 17psi limit instantly. My correction factor is also 0.2. What is wierd about your settings is that you are retarding alot of ignition. I can understand where boost drops down, but not an ic correction of 77.

[themyst]

Originally Posted by Clap135

I am not seeing this with cold IATs.
dci/dp/fmic, high 20s outside and my boost shoots up to my 17psi limit instantly. My correction factor is also 0.2. What is wierd about your settings is that you are retarding alot of ignition. I can understand where boost drops down, but not an ic correction of 77.

I'm doing this without meth....

With meth I bet it would peg the boost limit and stay there with really low aggression like you. I really don't want to run meth without a failsafe....

[Jeff@TopGearSolutions]

It was already said, but I was going to say, with cold air temps, the air is more dense, and thus more oxygen. So it takes less boost to make the same power.

[themyst]

Originally Posted by shiv@vishnu

Yep, that's pretty normal. Combine dense air charge/more power with reduced octane/higher fuel demands and you get what we are seeing. No biggie.

on another note, do you think I am running extremely lean post-shift?

[themyst]

Little update -

Prior to updating to V5, my autotune settings were at 12.7psi at 88IC. I always thought this was unusual, but after updating to V5, the default 13.5/50IC autotuned to 13.6/35IC after 1-2 short 3rd gear WOT pulls which is more like it. I did fill up at BP a few days ago just to try something different. Ambient temps were the same if not lower.

Perhaps bad gas? Bad firmware update? I'm leaning more towards the former.

[Penn999]

Originally Posted by themyst

Little update -

Prior to updating to V5, my autotune settings were at 12.7psi at 88IC. I always thought this was unusual, but after updating to V5, the default 13.5/50IC autotuned to 13.6/35IC after 1-2 short 3rd gear WOT pulls which is more like it. I did fill up at BP a few days ago just to try something different. Ambient temps were the same if not lower.

Perhaps bad gas? Bad firmware update? I'm leaning more towards the former.

most likely gas, I only get shell v-power now. I try and keep things as constant as possible to rule out any mishaps like that.

[335xiRT1]

I always see better autotuned numbers with shell 93 V-power.

[moveswiftly]

On map 1 with a Max PSI set on my car to 14.5 I have an Autotuned 14.2 and on map 2 with a max psi set to 16 i have an autotuned 14.5. however, When doing pulls in map 2 I constantly see 16 pis...
And i'm running Shell V power.

[themyst]

Interesting. I never really run Shell gas because I'm a creature of habit (running Gulf gas exclusively) but I'll give Shell a shot. It's only 3 cents more than the Gulf station by me.

[techlogik]

Originally Posted by JPSlick

It was already said, but I was going to say, with cold air temps, the air is more dense, and thus more oxygen. So it takes less boost to make the same power.

I believe this is an inaccurate statement. Someone correct me if I am wrong.

The amount of oxygen in the air is consistent, even at altitude.

It is the partial pressure that changes, thus the molecules are denser/closer together, which provides for greater explosion/expansion upon ignition of the fuel/air mixture.