[james4321]

Hey guys,
Few days ago I have done a custom tune and DP. Car seems to be faster. It’s stronger for sure. But today I went to check what is my 100-200kmph time and I am shocked. It’s worse than my stock car. Stock was 14.3s and now is like 14.8s. But stock was measured when outside temperature was around 8C (45F) and tuned when 35C (95F). I am wondering if this temperature difference can cause my car slower now than stock when temperature was much lower?
And sometimes can feel that car is a bit lazy when hot outside.

[tardboi]

Have you replaced the intercooler? Its definitely possible to lose power in heat.

[james4321]

Originally Posted by tardboi

Have you replaced the intercooler? Its definitely possible to lose power in heat.

Nope. IC is stock. Only custom tune and DP.

[Billfitz]

The density of air, and along with it oxygen, is greater at lower temperatures. That's why we use cold air intakes.

[james4321]

So you guys mean that can be like that, because od temp?
Of course I’ll measure times when temp will be low again. But now I AM wondering if something is wrong with car or it is how it is - summer worse times and ‚lazy’ cars.

[SeanFitz335]

Does your tune allow you to run a log (BM3 or MHD)? Take a few logs and check intake air temp (IAT). Watch your timing corrections as well. You will most likely see timing and/or boost corrections due to the heat. I live in Arizona and ran BM3 stage 1 with just a downpipe and stock intercooler for a while. Logs showed that my intercooler was getting heat soaked and IATs were way high. Car was pulling power and feeling flat.

I have since upgraded to a VRSF 6.5" Competition intercooler and power is back on back to back pulls. Of course, it's been 117F this week in Arizona (47C) so we're not making much power out here for the summer !

[Billfitz]

Originally Posted by james4321

So you guys mean that can be like that, because od temp?

Google 'Ideal gas law'. If it's confusing don't be concerned, Roger Goodell doesn't understand it either. It explains why cars run better in colder temperatures, and why you need to check your tire pressures more often in winter.

[james4321]

It’s shame, but I’m vessel engineer and I know that more cold air = more oxygen = more power. 😁
But I’m more curious if this temperature difference can cause that tuned car (when is hot outside) is slower than stock (cold outside) 0.5sec. I think thats a lot.
Starter to look for shift point. Because I have floored my car to check times. And it’s like I can feel that now it’s slower.

[Billfitz]

It will, for the same reason cars must have altered tuning to work well at high altitudes. So do people, for that matter.

[Wires]

When it's 30+C outside where I live, I can feel a huge turbo lag off the line. When it's 5C, a lot more power.

I've never time checked my car, but there would be a difference in HP between 35C and 5C. For me it's quite noticeable from a cool 10C morning to a hot 30C afternoon when driving (same car, same tuning, before as stock and now with BM3 S2)

[james4321]

Today I have checked my times 100-200kmph (~60-120mph). 35C (95-100F) and it’s 15.0s but I had to shift manually at 6200rpm. Higher was much worse time. But yeah, the point is: What do you guys think, what is the times dofference between 5C and 35C? I’m just wondering how much faster will be the car when temp is cold.

[Pussiwillow]

Originally Posted by james4321

Today I have checked my times 100-200kmph (~60-120mph). 35C (95-100F) and it’s 15.0s but I had to shift manually at 6200rpm. Higher was much worse time. But yeah, the point is: What do you guys think, what is the times dofference between 5C and 35C? I’m just wondering how much faster will be the car when temp is cold.

If you're still on the stock intercooler you're almost without a doubt pulling timing (power) even with colder temps outside let alone warmer temps… I would start with that because the stock intercooler is barely even adequate for a stock car in warm weather. I believe you start pulling timing around 120* IAT.
My stock intercooler on stage 2 saw 65* over ambient in 70*~ weather on 3rd-4th gear pull
Now I see 11-15*~ over ambient and way more consistent.

[MHF30]

Originally Posted by Billfitz

The density of air, and along with it oxygen, is greater at lower temperatures. That's why we use cold air intakes.

Do cold air intakes really make a difference though? I thought it was more a myth since the OEM intakes on these cars are cold air already.

[Wires]

Originally Posted by MHF30

Do cold air intakes really make a difference though? I thought it was more a myth since the OEM intakes on these cars are cold air already.

Depends on how you read what he wrote. CAI do address this, if you have a car (like mine) that comes with the hot weather kit (aka CAI), then changing that out for aftermarket would be a myth.

[Billfitz]

Originally Posted by MHF30

Do cold air intakes really make a difference though? I thought it was more a myth since the OEM intakes on these cars are cold air already.

Cold air intakes do make a difference. What's mythical is the claim that after-market intakes make a difference. They make that claim based on being cold air intakes, but fail to note that the stock intake is cold air. Worse, I've seen more than a few that claim to be cold air, but aren't. If you can see the air filter when you open the hood it's not a cold air intake.

[dtawf30]

F30 330i here (b48). I have the exact same issue. Car feels significantly slower during the day than at night time. B48’s are said not to require an intercooler due to the water to air system that it has, but I feel like it could fix my issues. Currently stage 2 on BM3 with a catless DP and a MST CAI. Let me know what you’ve done/ if you have done anything for this problem

[thejeremyman9]

Originally Posted by dtawf30

F30 330i here (b48). I have the exact same issue. Car feels significantly slower during the day than at night time. B48’s are said not to require an intercooler due to the water to air system that it has, but I feel like it could fix my issues. Currently stage 2 on BM3 with a catless DP and a MST CAI. Let me know what you’ve done/ if you have done anything for this problem

What could fix your issue? An upgraded IC? Note that OP has a n55 with air/air IC so its not the same as your car. How are IATs in your datalogs?

Datalog when you feel like the car is slow then datalog when you feel like the car is fast and post them both to see if there is something obvious to explain the perceived power difference.

[dtawf30]

Originally Posted by thejeremyman9

What could fix your issue? An upgraded IC? Note that OP has a n55 with air/air IC so its not the same as your car. How are IATs in your datalogs?

Datalog when you feel like the car is slow then datalog when you feel like the car is fast and post them both to see if there is something obvious to explain the perceived power difference.

Here are the logs. I’ve already got them looked over and it turns out there are timing corrections. Fuel quality should be good enough. Could it be spark plugs ? I’ve been stage 2 for about 10,000 kms and they’ve been on the stock ones.
https://www.bootmod3.net/log?id=6548...eae432fbf5e8c2

https://www.bootmod3.net/log?id=654f...05ef36c8387c32

[thejeremyman9]

Originally Posted by dtawf30

Here are the logs. I’ve already got them looked over and it turns out there are timing corrections. Fuel quality should be good enough. Could it be spark plugs ? I’ve been stage 2 for about 10,000 kms and they’ve been on the stock ones.
https://www.bootmod3.net/log?id=6548...eae432fbf5e8c2

https://www.bootmod3.net/log?id=654f...05ef36c8387c32

I skimmed them and it doesnt really look like timing corrections is the problem. It looks like the DME is actually lowering the timing target when the IATs are higher, by several degrees across the RPM range. Timing corrections are actually minimal even at the higher IATs (good fuel quality), but the car has less timing which will definitely reduce power. I dont see ambient temp in the logs so not sure what the delta over ambient is.

[dtawf30]

Originally Posted by thejeremyman9

I skimmed them and it doesnt really look like timing corrections is the problem. It looks like the DME is actually lowering the timing target when the IATs are higher, by several degrees across the RPM range. Timing corrections are actually minimal even at the higher IATs (good fuel quality), but the car has less timing which will definitely reduce power. I dont see ambient temp in the logs so not sure what the delta over ambient is.

Soo… the issue is simply temperature? I’m trying to avoid concluding with that because of the significance in difference between day and night performance, it’s literally a day and night difference 🤣. Burbles too sound much more intense at night, but I feel like that’s explained by temps

[thejeremyman9]

Originally Posted by dtawf30

Soo… the issue is simply temperature? I’m trying to avoid concluding with that because of the significance in difference between day and night performance, it’s literally a day and night difference 🤣. Burbles too sound much more intense at night, but I feel like that’s explained by temps

Based on my review of the logs, it definitely looks to me like lower timing targets at the higher IATs. ~3 degrees of timing can have a pretty big impact on power, not to mention the hotter air is itself going to make less power. IIRC it was like 20 deg C higher in the 2nd log.

What were ambient temps on those days?

I am not sure if A/W IC upgrades are offered for your platform, but another option is meth injection.