Reduced redline on track (DCT)

[MaxL]

I am getting reduced redline on track, particularly on Watkins Glen. I know other DCT cars have a similar issue, but for me it's a bit too much of a problem - I can only do 4-5 laps before it starts to creep. The oil temp seems to be normal - just 1/3 of the way past the middle mark, and not going higher. In fact, it gets to that level within a lap and stays there stably, while redline starts to get reduced after about 4-5 laps at WGI.

I've noticed that these things help: short-shifting, shifting less (not going down to 3rd or up to 6th), downshifting at the very end of braking zone when revs are lower (but this is suboptimal because in many turns it means downshifting while turning), being slow...

My hypothesis is that it's water temp, probably because of DCT. Has anyone seen this issue and how did you resolve it? I am planning to sell the car in less than a year, so would rather avoid expensive mods.

[Porschefile]

There isn't an easy fix that I'm aware of. A larger DCT cooler would help if that is the problem. You could always add water wetter to the rad and see if that helps. I had great results with water and water wetter rather than antifreeze (or with low antifreeze content).

It is fairly unusual to have the revs limited in such a short time though. My car didn't have issues until 25-30min of hard driving (with 80+ ambient).

[Gearhead999s]

Originally Posted by MaxL

I am getting reduced redline on track, particularly on Watkins Glen. I know other DCT cars have a similar issue, but for me it's a bit too much of a problem - I can only do 4-5 laps before it starts to creep. The oil temp seems to be normal - just 1/3 of the way past the middle mark, and not going higher. In fact, it gets to that level within a lap and stays there stably, while redline starts to get reduced after about 4-5 laps at WGI.

I've noticed that these things help: short-shifting, shifting less (not going down to 3rd or up to 6th), downshifting at the very end of braking zone when revs are lower (but this is suboptimal because in many turns it means downshifting while turning), being slow...

My hypothesis is that it's water temp, probably because of DCT. Has anyone seen this issue and how did you resolve it? I am planning to sell the car in less than a year, so would rather avoid expensive mods.

When was the last time you cleaned the fins on the rad & coolers.The last time I cleaned mine I could not believe how much crud I got off them.I also had issues with reduced redline at WGI before I cleaned them but only after about 20 minutes running in 30c heat..

[Jaypod]

I had the same problem Max, pretty much every session with the exception of the first of the day. Being extremely hot out and it not really affecting the fun on the track I am not going to sweat it. I ran without any issues at CMP a couple of days prior when it was a little cooler out.

[MaxL]

I'm worried because it was happening more than last time I was at the Glen. Also seems to be affecting me more than Jaypod.

I did wash the radiator before the event from inside and outside, as much as I could without removing the bumper or lifting the car, but fins are not nearly as clean as on a new car. So it can be the culprit. What would be the best way to clean the radiator?

[Gearhead999s]

Originally Posted by MaxL

I'm worried because it was happening more than last time I was at the Glen. Also seems to be affecting me more than Jaypod.

I did wash the radiator before the event from inside and outside, as much as I could without removing the bumper or lifting the car, but fins are not nearly as clean as on a new car. So it can be the culprit. What would be the best way to clean the radiator?

I just sprayed everything with Simple green and let it sit for a while then backwashed it with the hose.If you use a pressure washer you will likely bend the fins which will restrict the airflow through the cooler.I was amazed at how much rubber & other crud that came off with low pressure water.

[mid-corner fun]

Log your water temps to see if that's the culprit, instead of guessing. You can do it for free if you're willing to glance down at the display on the straights (where the water temps are at their lowest) or borrow someone's data system for a session and look at the results later on.

Cleaning the radiator is a must regardless, for me it was the difference between finishing the sessions or not last year (with a different bmw runing 100% distilled water + Mocool)

[sawzall]

Originally Posted by MaxL

I'm worried because it was happening more than last time I was at the Glen. Also seems to be affecting me more than Jaypod.

I did wash the radiator before the event from inside and outside, as much as I could without removing the bumper or lifting the car, but fins are not nearly as clean as on a new car. So it can be the culprit. What would be the best way to clean the radiator?

I don't think you can say the cooling issues affect you more than anyone else. A lot of people had reduced red lines at WGI. Driving style will also play a big part in the amount of heat generated. Also, don't forget the last couple days at the Glen were by far hotter than the previous years events.

That being said, have you ever changed your coolant? You might want to look at that as well as your thermostat, and barring that, you might want to consider getting a new/improved radiator. It would help if you had information on your coolant temperatures to make sure that is the root cause.

[WarrantyTracker]

Yikes.

I ran 3 sessions each Saturday and Sunday at VIR North Course in the mid-80s this weekend with DCT, no problem.

Did the course in 3rd at very high revs, with redline shifts up to 4th on the back straight and 5th on the front straight. This course has lots of turns and elevation changes and several spots where you mat the throttle on every lap.

Just how hot was it at WG?

[sawzall]

Originally Posted by WarrantyTracker

Yikes.

I ran 3 sessions each Saturday and Sunday at VIR North Course in the mid-80s this weekend with DCT, no problem.

Did the course in 3rd at very high revs, with redline shifts up to 4th on the back straight and 5th on the front straight. This course has lots of turns and elevation changes and several spots where you mat the throttle on every lap.

Just how hot was it at WG?

Around 31-34C, with very high humidity.

[MaxL]

Originally Posted by WarrantyTracker

Yikes.

I ran 3 sessions each Saturday and Sunday at VIR North Course in the mid-80s this weekend with DCT, no problem.

Did the course in 3rd at very high revs, with redline shifts up to 4th on the back straight and 5th on the front straight. This course has lots of turns and elevation changes and several spots where you mat the throttle on every lap.

Just how hot was it at WG?

Have not been to VIR, but WGI is tough on the engine. It's 4th gear most of the time with the throttle pinned down pretty much all the time except when braking and two uphill runs from 3 to redline of 4 and from 3 to 6. On the second day I was going through 2/3 of the tank of gas per one full session.

I'll clean the rads better, buy ODB/CAN logger for water temps and see what happens next time.

[CanAutM3]

Do you track with the AC on?

I never had any overheating or reduced redline at the track except for the two time I forgot to turn AC off. I would get the reduce redline plus soon thereafter a overheating warning. Turning off AC and doing a cool down lap solved the problem on both occasions.

[MaxL]

Originally Posted by CanAutM3

Do you track with the AC on?

Only when I have a dead hooker in the trunk

No, I have it off. It is only this bad at WGI. I had it at Calabogie just once but after 30 minutes of driving, and it was 37C outside. Mosport is fine in any weather.

[WarrantyTracker]

Originally Posted by sawzall

Around 31-34C, with very high humidity.

What's that in English? I'm a Virginian, not a European.

[WarrantyTracker]

Originally Posted by MaxL

Have not been to VIR, but WGI is tough on the engine. It's 4th gear most of the time with the throttle pinned down pretty much all the time except when braking and two uphill runs from 3 to redline of 4 and from 3 to 6. On the second day I was going through 2/3 of the tank of gas per one full session.

I'll clean the rads better, buy ODB/CAN logger for water temps and see what happens next time.

Yep, you were flogging it harder than I was.

But I did have the AC on high

[E92inSG]

Does anyone know for sure yet what causes the redline to creep downwards on the track?

Oil temp?
Water temp?
Dct oil temp?

I get it after 3-4 hot laps in hot and humid Malaysia.

[Dartanium]

next track day is 100.5F with 65% humidity, looks like summer is gonna be extra tough on DCT than other parts of the car

[bigjae1976]

I think its just oil or water temp that will pull the redline down but not sure. Isn't there a separate warning for if the DCT is overheating?

My hypothesis with DCT cars is they are more likely to overheat because its so easy to shift. Much easier to keep the tach pinned on the redline vs a 6sp car. AND you're shifting a lot more.

Reduce the shifts and look for places where a higher gear will work just as well...the engine won't pull the redline as fast.

[Black Gold]

Originally Posted by bigjae1976

I think its just oil or water temp that will pull the redline down but not sure. Isn't there a separate warning for if the DCT is overheating?

My hypothesis with DCT cars is they are more likely to overheat because its so easy to shift. Much easier to keep the tach pinned on the redline vs a 6sp car. AND you're shifting a lot more.

Reduce the shifts and look for places where a higher gear will work just as well...the engine won't pull the redline as fast.

interesting, and makes sense.

plus who knows if the dct design naturally generates more heat

[Jaypod]

Originally Posted by KennyPowers

interesting, and makes sense.

plus who knows if the dct design naturally generates more heat

I have had the water temp warning many times in my old 6MT which reduces the redline until the temp comes down.

When I have had issues with the DCT, redline being reduced, only once have I seen the water temp warning, usually its just the redline reduction with no message, guessing creating too much heat

[bigjae1976]

Originally Posted by KennyPowers

interesting, and makes sense.

plus who knows if the dct design naturally generates more heat

I think the tendency to shift more in a DCT car creates more heat.

[Black Gold]

Originally Posted by bigjae1976

I think the tendency to shift more in a DCT car creates more heat.

right, I think that makes sense

but in addition, I wonder if the device itself generates more heat (dual clutch setup, more working parts etc)