Hot weather driving

[Shortstuff]

So it's a 42 degree day in Melbourne today. I've noticed that even in drive my car is holding on to gears much longer than normal - cruising at 60 it will still be in 3rd, and it won't change to 6th until 100.

It also feels flat as anything. Has anyone else experienced this on a hot day?

It was ok last night at 30 degrees.

[AdamD]

So it's a 42 degree day in Melbourne today. I've noticed that even in drive my car is holding on to gears much longer than normal - cruising at 60 it will still be in 3rd, and it won't change to 6th until 100.

It also feels flat as anything. Has anyone else experienced this on a hot day?

It was ok last night at 30 degrees.

I think this must be a trait of the DSG in the Mk7. I never observed it in my Mk6 GTI when driving in hot weather, but my mum's brand-new Octavia RS has been doing exactly the same thing in very high heat (40 degrees plus) - only shifts into 4th at just over 60km/h, etc. If operating in manual mode it'll happily shift into the higher gears when asked, but revert to drive and it'll shift back to a lower gear pronto. I honestly don't know why it does this.

It'll feel flat because it'll be backing off the timing and running rich to keep the engine cool and to prevent detonation (pinging). Intake temperatures will be through the roof on a day like today. Drive it gently.

[Shortstuff]

Thanks for confirming! It's back to normal now it's cooled down a bit.

My Focus ST never used to feel flat on a really hot day, just went a lot better on a nice cold day so this surprised me in my GTI.

[VRJ]

Are we talking about the 6 or 7 speed DSG?

[Beech]

I have a 2014 Mk7 GTI, I live Karratha WA, we regularly experience 40+ degree heat during the summer. For me the car is an absolute disappointment to drive in the heat, it suffers from reduced power, horrid fuel economy. Additionally mine suffers mild fuel vapourisation issues on a hot day. Lots chugging and rough idling after starting the engine. The problem does resolve itself once the fuel lines cool down.

[Shortstuff]

The 6 speed in the GTI/PP and R is the culprit. My girlfriend has a Polo GTI with the 7 speed DSG and no such issues.

Wonder if a DSG remap would fix it?

[mp2811]

I have stage 1 apr and HP DSG map on my R and had no issues driving around yesterday.

Didn't notice any issues with gear changes and fuel economy was same as usual driving min traffic was 8l 100km with A/C blasting.

Obviously power would be down slightly but common sense in heat just cruise around! Plenty cool/cold weather in Melb to drive harder!

Guess the ecu/DSG combo a winner in all conditions!!

[NTPete]

Air Density

Hotter temperature's with lower humidity mean thinner air, which means the engine is producing less power at the same revs. The DSG works on load and it changes when the engine is producing enough power to move to the next gear, so on a hot day you have to expect less power. That's why Drag racers and Pilots don't like hot days as the air is much thinner so less bang for the buck and higher ground speed required to produce the same amount of lift for take off..

[donweather]

Hotter temperature's with lower humidity mean thinner air, which means the engine is producing less power at the same revs. The DSG works on load and it changes when the engine is producing enough power to move to the next gear, so on a hot day you have to expect less power. That's why Drag racers and Pilots don't like hot days as the air is much thinner so less bang for the buck and higher ground speed required to produce the same amount of lift for take off..

According to this dry air (ie less humid) is more dense than moist air.

Density of Dry Air, Water Vapor and Moist Humid Air

https://en.m.wikipedia.org/wiki/Density_of_air

My car hates hot humid days compared to cooler low humidity days.

[rabbitz]

So it's a 42 degree day in Melbourne today. I've noticed that even in drive my car is holding on to gears much longer than normal - cruising at 60 it will still be in 3rd, and it won't change to 6th until

Is it the same with or without A/C?

[danielb_c]

My mk7 R did the same thing when we had a 38-40deg day in Sydney, within a couple of weeks of me picking it up. It kept the revs far higher than it should have or even needed to (power was reduced, but still plenty of torque to push through the gears during gentle driving). Odd, as you'd think higher revs would mean quicker temp buildup, but maybe it helps everything else run quicker to cool it down (fans, etc), and cope with the super high load the AC would be putting on it.
It'd be good to know for sure if it's purely mapping or overheating transmission fluid or something.