Tuning in winter vs. summer
Dec 23, 2007, 08:21 PM
#1
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Tuning in winter vs. summer
How do professional tuners compensate and create a safe/proper tune for all four seasons (all temperatures) while only having your car one day, at one temperature, w/ one humidity? I don't know enough about tuning or how the car's sensors compensate in order to properly understand. Can anyone help?
Dec 24, 2007, 06:27 AM
#3
Basically, the car is more likely to knock in the winter (cooler air) if all other variables aren't considered. IAT and boost are the biggest changes with the seasons.
So, if you tune a car in the winter, you are basically set. You build in the basic margin of safety and it will likely be fine in the summer. If you tune in the summer, you leave some extra padding so that the car will not encounter knock in the colder months.
It really just takes some time and tuning cars around the year to see what the differences are. Different mods will make a difference too ... the biggest being the method of boost control.
Hope that helps.
So, if you tune a car in the winter, you are basically set. You build in the basic margin of safety and it will likely be fine in the summer. If you tune in the summer, you leave some extra padding so that the car will not encounter knock in the colder months.
It really just takes some time and tuning cars around the year to see what the differences are. Different mods will make a difference too ... the biggest being the method of boost control.
Hope that helps.
Dec 24, 2007, 06:57 AM
#4
its nothing more than my opinion, but I believe the issue is smaller than you think.
If you have tuned all the cells in load, boost and fuel and your coolant temp & ait are correct, your tune should not become worthless from one time of year to another.
After all I'm pretty sure the stock evo does not require a re-tune from winter/summer.
Part of the problem is if the tune has not covered any possible aspect of the load map. If you step into an untuned section of the map because the weather has caused your car to run differently is where you might have problems.
Same could prolly be said about the boost control maps
Practically once you have tuned for a season and find running issues get a re-tune, after a bit of this running around the ecu should be centered enough to run year round.
If you have tuned all the cells in load, boost and fuel and your coolant temp & ait are correct, your tune should not become worthless from one time of year to another.
After all I'm pretty sure the stock evo does not require a re-tune from winter/summer.
Part of the problem is if the tune has not covered any possible aspect of the load map. If you step into an untuned section of the map because the weather has caused your car to run differently is where you might have problems.
Same could prolly be said about the boost control maps
Practically once you have tuned for a season and find running issues get a re-tune, after a bit of this running around the ecu should be centered enough to run year round.
Dec 24, 2007, 07:45 AM
#5
the big difference is cylinder pressure. Even at the same boost/load level, cylinder pressures will be higher with a cooler, denser air charge in the winter. This can cause knock even if you don't leave the tuned cells.
The Evo does have a temperature compensation map that can be tweaked. I've modified it on a few vehicles and have seen a benefit from it. However, even with a modified compensation map, that dense air will reveal any over zealous areas of your tune.
Many have reported knock on the stock tune. The stock tune was designed to be good for as many weather/location variables as possible and therefore has a large margin of safety. This method tries to ensure that the car runs well in nearly any climate or altitude, but also leaves a lot to be desired power wise. We tuners could easily create a similar tune with big safety margins, but it would likely be no better than the stock tune.
When you tune the car, you effectively reduce the enormous margin of safety that the stock tune has and narrow it down to match the specific car and environment. This is why drastic location changes (Texas to Colorado for instance) require a re-tune.
But, when it comes down to it, a good tune will not knock in the summer or winter and will make power. You should not "require" a retune unless the environment drastically changes (elevation, humidity, etc.) or the car changes.
The Evo does have a temperature compensation map that can be tweaked. I've modified it on a few vehicles and have seen a benefit from it. However, even with a modified compensation map, that dense air will reveal any over zealous areas of your tune.
Many have reported knock on the stock tune. The stock tune was designed to be good for as many weather/location variables as possible and therefore has a large margin of safety. This method tries to ensure that the car runs well in nearly any climate or altitude, but also leaves a lot to be desired power wise. We tuners could easily create a similar tune with big safety margins, but it would likely be no better than the stock tune.
When you tune the car, you effectively reduce the enormous margin of safety that the stock tune has and narrow it down to match the specific car and environment. This is why drastic location changes (Texas to Colorado for instance) require a re-tune.
But, when it comes down to it, a good tune will not knock in the summer or winter and will make power. You should not "require" a retune unless the environment drastically changes (elevation, humidity, etc.) or the car changes.
Dec 24, 2007, 08:02 AM
#6
Basically, the car is more likely to knock in the winter (cooler air) if all other variables aren't considered. IAT and boost are the biggest changes with the seasons.
So, if you tune a car in the winter, you are basically set. You build in the basic margin of safety and it will likely be fine in the summer. If you tune in the summer, you leave some extra padding so that the car will not encounter knock in the colder months.
Hope that helps.
So, if you tune a car in the winter, you are basically set. You build in the basic margin of safety and it will likely be fine in the summer. If you tune in the summer, you leave some extra padding so that the car will not encounter knock in the colder months.
Hope that helps.
Knocking occurs when cylinder temps are too high for the given fuel,ie the "flashpoint". In the winter you see the lowest IAT's resulting in lower cylinder temps resulting in less detonation. People generally run the best MPH at the track when its cold.
in the winter, yes you are seeing more volume of air in the cylinder(PV=nRT, for those who have take high school chemistry) but at a lower temperature. You would think that the increased boost would cause more detonation, but actually its the oppostite.
plus, in the winter the cars cooling system can maintain lower temperatures because of newtons law of cooling
T(t)= T(actual) + [T(radiator)-T(actual)]constant
Which basically states, the greater the difference in the cars radiator and ambient air temperature the faster it will be cooled. This temperature thing obvious to most people but you'd be surprised.
Most detonation starts from hot spots on the head, and the cooler you can keep the head, the less likely you are to see knock or detontion.
I suck at writing but i hope i got my point across.
Last edited by colo_evo; Dec 24, 2007 at 08:04 AM. Reason: I suck at writting
Dec 24, 2007, 08:19 AM
#7
Your observations seem correct and do contradict what I've stated. However, in practice, a tune that is great in the summer is likely to knock in the winter. I've seen it happen on many cars I've tuned. I've taken a few of these cars a set the boost and AFRs exactly where it was in the summer and still had to retard timing to manage knock.
Maybe my explanation is incorrect, but I've witnessed it happen many times. I'm sure many tuners will agree that you have to run less timing advance in the winter. I feel that it's due to excess cylinder pressure and an earlier peak pressure due to the denser air charge.
Maybe my explanation is incorrect, but I've witnessed it happen many times. I'm sure many tuners will agree that you have to run less timing advance in the winter. I feel that it's due to excess cylinder pressure and an earlier peak pressure due to the denser air charge.
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Dec 24, 2007, 08:31 AM
#8
I'm interested to see it actually happen...i'm going to try and do some logs today, the high in denver today is like 30.
With my experience tuning a few supercharged mustangs, they ran much better in the cold. they might have been knocking a little, but you could tell a difference. I've blown a few head gaskets from excessive knock but that happened when i'd hotlap the car at the track in 90+ temperatures...
Touringbubble: i'm not trying to argue with you and i'm not saying either of us is right(you probably feel the same way). I'm just arguing from past experence(as you are). I actually like these debates because this is the best way to learn.
With my experience tuning a few supercharged mustangs, they ran much better in the cold. they might have been knocking a little, but you could tell a difference. I've blown a few head gaskets from excessive knock but that happened when i'd hotlap the car at the track in 90+ temperatures...
Touringbubble: i'm not trying to argue with you and i'm not saying either of us is right(you probably feel the same way). I'm just arguing from past experence(as you are). I actually like these debates because this is the best way to learn.
Dec 24, 2007, 08:42 AM
#9
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This is an interesting post. Especially since peoples boost has fluctuated with the colder weather. I know I have had to lower my boost a few times now. Subscribed... It would be interesting to hear some more tuners opinions...
Dec 24, 2007, 08:44 AM
#11
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well that's why I posted, so you more experienced guys can comment and work itout on YOUR cars, not mine. 
j/k I do appreciate the level-headed discussion.
j/k I do appreciate the level-headed discussion.
Dec 24, 2007, 08:45 AM
#12
Colo, same here. I enjoy debates.
I'll agree with your last statement. FI engine perform better in colder weather. Even with pulled timing, my Evo was still around 2 MPH faster in the 1/4 after the temps dropped. I went from a 12.6 to a 12.4 (feathering first) after temps dropped.
However, this was after logging the previous 4 runs or so and backing off the timing each run for knock. I started the night at a 12.8 with 9 counts in 3rd and 4th and ended knock free with the 12.4.
I'll agree with your last statement. FI engine perform better in colder weather. Even with pulled timing, my Evo was still around 2 MPH faster in the 1/4 after the temps dropped. I went from a 12.6 to a 12.4 (feathering first) after temps dropped.
However, this was after logging the previous 4 runs or so and backing off the timing each run for knock. I started the night at a 12.8 with 9 counts in 3rd and 4th and ended knock free with the 12.4.
Last edited by TouringBubble; Dec 24, 2007 at 08:49 AM.