Is tuning in colder weather bad when summer arrives?

[LGTspecB1657615261]

I am somewhat of a n00b about this stuff. If you tune the car in, say 45 degree weather, is it possible to run into issues when it gets into the 80's?

 

You are sucking in a lot hotter air, and the intercooler could be less efficient as well. What if you are heatsoaked and get on it? If everything was mapped out in colder weather, do you have the possibility to knock in the high-end?

I always figured it was best to tune for worst-case scenario to always be safe.

 

I know the MAF will read less airflow with warmer air and the ECU will compensate, but what if your intercooler is not running as efficiently as when you got the car tuned? i.e. the charge temps are a lot higher with respect to the intake temps the ECU is reading.

I guess, for me, there is a bit of disconnect between intake temps and charge temps and how the ECU makes realtime changes with respect to that. Will it pull timing up top if the air is a lot hotter? Will it "remember" that and continue to pull timing? I know in my knock tables it takes forever to get the -1.4 events to disappear because you don't spend too much time in that range.

 

Sorry this post is somewhat all over the place.

Thanks for the help.

[Legend]

It's better to tune in cold versus tuning in hot. Either way, you'll want to check some logs in the opposite conditions you tuned in to tweak as necessary.

 

For you, you might suddenly find yourself a little knock-limited when the warm temps come. If so, I'd decrease your base timing in the affected areas. Alternatively, you could leave the tune alone and just let the ecu subtract a little FLKC. You may also need to revisit your WGDC by IAT table.

[ClimberDHexMods]

Your concept of intercooler efficiency is incorrect. It should be just as efficient at 30 degrees as at 100 degrees ambient temperature, all other things being equal. The issue is not how hot your intercooler outlet temp is overall, but how hot that temp is relatve to the temp detected at the MAF. The DIFFERENCE in temps is where you can get in to trouble, at any temperature basis. Separately, going from hot tuned properly, to cold not tuned specifically in the cold, is that you hit table cells in the cold you cannot hit (and thus test) in a hotter climate.

[LGTspecB1657615261]

Really though? What if the ambeint temp is 80. Then the TMIC metal and coolant is ~80 at true equilibrium (lets forget about the heat exchanger for now). 140 degree air passes through the 80 degree TMIC with 80 degree coolant. The ability for the coolant to draw heat is proportional to the temperature difference between the air and the medium it is passing the heat to. Is that a correct statement to say?

 

If the coolant is now heatsoaked, we have 140 degree air and 110 degree TMIC/coolant. The ability to drop the 140 degree air is less because the difference between the two is smaller.

Is that NOT correct?

Lets say in scenario #1 the temp drops from 140 to 100 due to the TMIC / coolant. In scenario #2, how could it reach 100 degrees? The TMIC is heatsoaked and already over 100 degrees?

 

And what if my TMIC is not large enough and cannot keep up with the airflow. i.e. there is not enough cooling "power" for the flow of air?

 

My conern is, I have NO idea how to know if my AWIC is effective and comparable to a FMIC, TMIC, or worse than both. I have no idea what temperature drop a TMIC and FMIC are able to obtain. Without that data, I have nothing to compare it to. A local friend is installing an FMIC this spring, so I might pay for the parts to have sensors installed on it.

[ClimberDHexMods]

Really though? What if the ambeint temp is 80. Then the TMIC metal and coolant is ~80 at true equilibrium (lets forget about the heat exchanger for now). 140 degree air passes through the 80 degree TMIC with 80 degree coolant. The ability for the coolant to draw heat is proportional to the temperature difference between the air and the medium it is passing the heat to. Is that a correct statement to say?

 

If the coolant is now heatsoaked, we have 140 degree air and 110 degree TMIC/coolant. The ability to drop the 140 degree air is less because the difference between the two is smaller.

Is that NOT correct?

Lets say in scenario #1 the temp drops from 140 to 100 due to the TMIC / coolant. In scenario #2, how could it reach 100 degrees? The TMIC is heatsoaked and already over 100 degrees?

 

And what if my TMIC is not large enough and cannot keep up with the airflow. i.e. there is not enough cooling "power" for the flow of air?

 

My conern is, I have NO idea how to know if my AWIC is effective and comparable to a FMIC, TMIC, or worse than both. I have no idea what temperature drop a TMIC and FMIC are able to obtain. Without that data, I have nothing to compare it to. A local friend is installing an FMIC this spring, so I might pay for the parts to have sensors installed on it.

 

I'm sorry, but I am very tired so I'm just going to let it flow in no particular order.

 

A top-mounted good-sized AWIC intercooler is very far from black and white in comparison to an air-air tmic or fmic. In certain situations, your intercooler will perform better, most other things being equal. Your specific intercooler is too small IMO to really hold its own against an STi TMIC or FMIC efficiency-wise. But real numbers will tell you for certain. Your advantage against TMICs will be at stop lights and repeated pulls (because it is harder to heat soak an AWIC from within). So if you are a city driver, I believe it is a good choice. AWIC vs FMIC, the big difference is pressure drop and throttle response. However, those are small differences. People report small fractions of a second in additional response time with FMIC. Additionally, pressure drop is of minimal concern. The thing about boost is that unless you have a small turbo that is getting put out of efficiency range by needing to produce 2 or 3 extra psi instead of 1 or less, it is no problem to make more boost so that the throttle body/manifold still sees the target either way. Furthermore, smaller turbos end up pushing less air, leading to less pressure drop. So in its crazy way, pressure drop is most often a very small concern unless you are running a small turbo on a big fmic. People who do that can really set themselves back. So there are there are the AWIC advantages.

 

Now for the PERFORMANCE disadvantages.

Extra weight.

Radiant heat to the system is almost always present in some form, meaning if the ambient is 80, your water will always be a little more than 80. My thought to combat this is to use fans on the heat exchanger below XX speed, and wrap/shield the AWIC. But at the end of the day, a FMIC most of the time, and a TMIC some of the time can hit a temp closer to ambient than an awic can.

 

In this way, I think it is a close-wash between TMIC and AWIC. Around town, I believe the consistency of the AWIC will beat the TMIC due to no peaks and valleys of heat soak. On the highway, the close-wash flips the other way. If you insulate your AWIC from resting heat soak when you go run errands, or if you use a parked pump interval logic, then that issue is largely solved.

 

Race track (not drag strip) = NO for AWIC. Other cars' exhaust and the constant internal heat soaking will keep that ambient input water temp higher than you want, which effectively shoots you in foot. But on the track, it is important to note that nothing really works truly quite well compared to on the highway where you do a pull once in a while, and there is a ton of nice ambient air to keep the air-air intercooler or awic heat exchanger close to ambient.

[ClimberDHexMods]

If you already know this, congratulations: No need to tell me all about how you know this stuff.

 

Heat Exchanger (intercooler) theory (regardless of awic or tmic, it's all the same).

 

When it comes to intercoolers, people really screw up the concept of how they work more than anything.

 

I use to think an AWIC would dominate in almost all situations because I did not understand how heat moves from the charged air to the atmosphere in either type of application. But I have researched the theory of it to enough of an extent that I can now talk about it and know what's going on.

 

Basics:

Heat flows through air/water/metal/anything. Heat moves from where it is more hot to where it is less hot.

Heat usually does not transfer as fast as many people think. It moves relatively SLOWLY through aluminum intercooler cores.

Heat radiates through a core. You know how only the bottom 6 inches of a 9 inch or 12 inch high intercooler or visible on a LGT. That top part of the intercooler gets virtually no air flow through it either. In this example, if it gets really hot in the top part of the LGT FMIC, the heat radiates down through the core to where passing air has already cooled off the bottom levels of the intercooler. Hot to cold.

As I was saying before, heat moves slowly. How slowly? 6.3 seconds. No, it's completely variable. But it doesn't happen in a split second. That's why air-air tmics can heat soak after repeated pulls. STi heat soaks less easily than legacy tmic, but not eliminated.

So, that handles the first part, but there is more blurbing to be done.

[ClimberDHexMods]

reserved for when I'm not tired

[LittleBlueGT]

Your car already adjusts itself for temps. In the heat less timing is run (there is a table for that, IAT timing comp). It will even pull target boost if gets hot enough.

 

Your stock setting (likely unchanged on your tune I assume) are likely very close for what you need. They can however be tuned for. Do some logs in the heat, see how it goes. If you feel you need to run different timing in the heat then in the cold, consider adjusting the above mentioned tables, and leaving pri ignition timing alone.

 

Look at the tables, looks at the logs, use your head. Then if you still don't know, post up the logs for specific help. I think it will all start to makes sense.

[j255c]

No, tuning in hot weather required increased wgdc's. If you tune in the hot and then are on the same map for cold weather it may spike up higher and hit boost cut depending on what your tuner set it at.

[RJS5689]

As people have said, tune in the cold. This was my issue. I live in New York for the summer and during college vacations, but I go to school in Maine so I see some very cold winters. I was hoping to have my car tuned in the dead of winter, but it looks like my tune will be made next weekend. Looks like I'm tuning in the medium weather. Of course I'll have to take data logs during the summer/winter just to make sure everything is running alright.