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Discussion Starter · #1 ·
How does the temperature affect performance of our cars? I am talking about 3.0TDI engine. When it gets below 0 Celsius, does it decrease performance or should it stay same?

I am experiencing little, but noticeable decrease in power when temperature gets below 0 ~ 32F.
 

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I would have thought that when it's colder your car will have better performance as its getting cold air through the intake.

One for the prof I believe.
 

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+1

Didn't know there was such a thing as TOO cold air for an engine?

One thing is for sure, hot air is bad for performance. Average daytime temp in Sydney at the moment is 30C and it's awful for my S5's 0-100 time.
 

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Turbo engines love cold dense air,can add a few bhp:)
That's correct as long as you get the engine up to it's normal operating temperature first!

Also a thought.... Are Audis Quicker up North?:D
 

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I would have thought that when it's colder your car will have better performance as its getting cold air through the intake.

One for the prof I believe.
Someone called? ;)

OK... I'm a petrol head, not diesel head, but here's my view...

I petrol cars, the colder the air, the more dense, which boosts compression by a few percent. Cold air frequently has a high moisture content (at least here in the UK) which is incompressible, also boosting compression.

However, in a diesel, I would expect the following:

Diesels run much higher compression ratios (15 to 25:1), so the additional air density should make a difference, but the extra damp and cold will affect the diesel timing (something that can't be controlled precisely) and almost certainly alleviate this.

Diesel fuel also needs to be injected a ludicrously high pressures >1,000 bar. at lower temperatures, the fuel starts to become more viscous and I expect injector performance will decrease and acheivable rail pressures to be reduced. This I expect will lead to the reduced performance you are seeing.

...just an educated guess though!

Cheer, Prof. :)
 

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Does that only apply in Rutland (Ruddles Land) or the rest of the UK
 

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Discussion Starter · #8 ·
Thanks! I am sure that my car "felt" better in summer.:)
 

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I drive a diesel regularly (although its a diesel truck....duramax). I've noticed that in cold temperatures, once my engine is warmed up, it will make more power. However, diesel engines burn cooler than gassers, so it sometimes lakes a long time to get the engine temps up. Also, on my truck (and I assume the case is the same for the TDI's), there are fuel timing and quantity tables that vary depending on altitude and environment temperature. On the colder (and high altitude) tables, the timing is retarded relative to the normal operating timing in order to protect the engine. This will result in a reduction in power. Maybe this is probably what you are experiencing.
 

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Also bare in mind you'll have less traction in the winter unless you have winter performance tyres.

Here in the UK the residue from the cheap grit that the council's use leaves a slippy coating on the tarmac, noticible once the ice has thawed out. The bikers love it.
 

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And I who thought my A5 actually felt stronger :D

Yesterday in the cold (-5c) and no snow, but "wet salty roads" I was able to really push it and it moved like never before it felt. Was sliding and drifting in and out of some round abouts (all traction controlls turned off of course).

But traction is surely something that can make the car feel weaker for a short moment. I've noticed that if you gas it, and traction control is on, the traction control can slug down the car and it will go slower. If you turn traction control off, and let the wheel loose a little traction while accelerating... it will definetly feel faster.
 

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As others have said the engines will make more power as the air gets colder. However if the engine is cold the oil viscosity will definitely have more drag and cause the output to the wheels to lessen. Same for the gearbox, differentials, axles, seals, etc. If you can shove 0 degree air into a fully warmed up drivetrain you will have excellent power output.
 

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Air temp/humidity definately makes a difference to engine performance. Colder the better.
 

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Everebody is forgetting that Alejandro's A5 3.0 TDI has a MTM Cantronic unit installed.
With a really cold weather TDI engines increase its performance, but it depends on the air Temperature/boost/injection ratio maps of the ECU, because with really low temperatures probably the ECU decrease the power delivered to make easier and safer the driving.

Besides, it's possible that the Cantronic unit detects the temperature below 0ºC and stop modifying the stock ECU values trying to protect the engine and clutch of a bigger power delivery due to better conditions (colder and more dense air, so with more O2 and bigger power as a result).

It's only a guess, but I'm sure that a mail to MTM asking about it will answer the question.
 

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temp and performance

as the car monitors the air temp going in it should have an algorithmn to compute the correct fuel air ratio for the increased density meaning that you do in fact get more power.
The fuel is pre-heated if it is anything like my Passat with all the plumbing around the filter.
But the air surrounding the car is also more dense and so the car will do more work moving through it - though I would only guess it i less than the extra power from the engine.
 

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I for one definitely feel my car is down on power at the moment - I don't know if that's a temperature thing or something else (my emissions control light has come on YET again), but it definitely doesn't feel as 'perky' as normal.

I'm considering the APS re-map, but only on the condition that we do a rolling road both before and after - as I want to see what the actual output of the car is at the moment...

I was hugely embarrassed by a Lexus IS250 the other day that flew past me like I was stationary.... :( Or maybe it was more the case that at -2 degrees, I was waiting until I was out of the corner before getting the power down, whereas he felt sufficiently confident (or plain idiotic) to get on the power earlier... either way, was very embarrassing to be passed so easily.
 

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Turns out I probably wasn't imagining things (makes a change). A visit to the dealer to fix the emissions control light (yet again) has revealed that the car needs a new throttle body housing. Apparently, there is an intermittent fault where the valve is not opening properly - and that (they say) could account for loss of power.

Of course, this being an A5 part, it's on back order... so will update when the work is done.
 

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Discussion Starter · #18 ·
Thanks for so many answers and ideas guys! :)
 
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