I live at the top of a fairly long hill. Sometimes when as I'm leaving my garage I'll put my diesel A7 in neutral and just let the engine idle and warm up while I coast for a 1/2 mile or so. Then I'll put it in drive on the fly at around 20 +/- miles per hour when the decline ends.

I think the Audi's trans. is pretty much bullet proof, but I'm wondering if maybe it's not a great thing to do in general for the transmission. Thoughts?

 

Historically, there used to be so many stories about using neutral in an automatic, from revving on hot days to speed up the compressor and reducing overheating. reducing drag at stop lights, etc.

This issue has even come up on Car Talk… suggesting that even those who really don't care bout cars ponder such dilemmas.

Do you see any warning lights come up on the dash? These drivetrain systems are so interconnected via digital linkages, that it would seem like a bad idea, although I understand and celebrate your intention to give the motor sufficient time to reach near operating temperatures and a full head of oil pressure. My own routine is to start the engine as soon as I get in the car and the buckle-up, set radio, etc and when the car comes off of initial fast idle, to pull out and go. Emissions and fuel mileage are stabilized when you reach operating temperatures quickly, so I would assume a load will help your engine clear water vapor, etc. more quickly and that the coasting slows down the process. Certainly, an engine without a significant load is running inefficiently and subjected to the possibility of carbon build-up, etc. In my previous world of forced induction Saabs (two Aero's), light or no loads on the engine were a death knell.

Perhaps there is an Audi Tech out there who has seen a service bulletin on this - I would love to know.

Happy Motoring

Eric

 

Scott, can you let us know what the benefit is?

 

It's not a great idea to coast in neutral with any car for several reasons, one of which is lack of control in an emergency situation. While the transmission may be robust, Audi has not recommended tossing the transmission into drive from neutral at 20 mph as an everyday event.

I doubt the engine will warm up any quicker, especially since it will not be under load in neutral. In fact, it takes a few miles to do so - your 1/2 mile wouldn't make much difference in any case.

 

The engine will warm up quicker in neutral when coasting down the hill. When your foot is off the throttle when in gear and you are going fast enough, the injectors shut down since fuel is not needed to maintain RPM's. No fuel = no heat.

IDK if dropping into gear at 20 MPH will cause any damage. I would think that the engineers would have programmed a throttle blip so the engine RPM and road speed matched if it resulted in warranty work.

 

Thanks for the replies. As far as benefit, I'm claiming zero benefits really, apart from *maybe the engine be a tad warmer before its actively engaged.

Mostly, I just get a weird little kick out of being able to coast this modern piece of machinery like a soap box car for the first minute or two. I also agree with whoever said it's probably not the safest thing to do. I'm in a rural area so little chance of evasive maneuvers due to other cars, but the point is well taken.

 

There will be grater benefit to have the car in a high gear and just roll down hill (maual transmission mode) this way the engine will only drive by compression and you spear you transmission and brake pads :-)

 

I don't think I'd be happy to have my transmission and brake pads speared. Sounds expensive.

 

Typo :-)