So I have an A6 3.2 and I usually I keep my tranny in neutral when coasting down hills (in my mind it makes up for all the jackrabbit starts, i know it doesn't really). The other day I had forgotten it was in neutral and went to gun it through a yellow light. I realized it was in neutral when the engine seemed to be floating at a really high RPM and I wasn't accelerating...now I know that in park if you rev the engine there is a cutoff at like 4,000, but this was much higher. When I re-attempted to hit the limiter again i noticed that it's at around 7,600 RPM. That's ridiculous! The redline is at 6,800, and I have no idea why they would put a limiter so astronomically high if the engine couldn't handle it.

On occasion I've shifted into 1st gear right below the cutoff of 30mph and it over-revs to around 7200 before the tranny catches up and shifts, but a limiter at 7,600 is ridiculous. Just thought I'd share.

 

I suspect the Germans are being conservative in setting the red line low -- these cars are well engineered. Having said that, there is also a difference between running a car over red line at load and no load. I think I'll keep my older A6 and treasure the MT6 that let's me make all the decisions (good and bad).

 

Are you sure you have a stock engine?
You could be lucky having a manufacture's glitch.

 

True about the MT6; I wish they still put them in the A6s in the US. But I thought it was actually better to rev an engine higher under load vs not?

And I suppose it's possible it was a glitch, though it definately does have a limiter, just astronomically high. My suspicion is that the engine simply doesn't make any more power up that high.

 

Load or not, the engine isn't desinged to go over 8,000 rpms, any higher than that the valve springs couldn't keep up with the speed of the engine causing valve float and eventually make contact with the pistons, you were dangerously close to taking out that engine. I've seen many S4 4.2L engines over rev thier engines and blow thier motor when it was chipped. According to the freeze frame data in the ECM at the time those 4.2L's blew at about 8,200 rpms.

Those were $19,000 repairs BTW.

 

So the magic number is 8,000 and he only went to 7,600 so everything is OK....

Except - I can't figure out why anyone would put a vehicle in neutral while going down hills! It does nothing for gas milage, wrecks havoc with the brakes, and is dangerous.

 

Those driving skills should make your mechanic a happy guy! He has boat payments too! Keep up the good work!

 

Both true and funny.

 

Yes it doesn't go near 8,000, just right around 7,500-7,600. And there is most definately a limiter up there, even though everything is 100% stock.

And I only coast down hills where I don't have to brake. Probably doesn't make any difference, though it definately doesn't hurt anything. And yes, I'm sure it makes my Audi certified mechanic happy, though assuredly if he's getting his boat payments from my car it is from the factory, as I still have a great deal of warranty left on it.

These really are great durable engines though, and would make for a good swap with a 6MT A4 because of the lack of a limiter. I honestly believe that they can probably handle almost 8k without a problem.

 

LOL, if you were to float a valve into the piston, audi would NEVER cover that. Thats why they were $19,000 repair bills attached to 2 year old S4s. You wouldn't win in court either, they didn't....... Did i mention one of the cars that blew an engine was an automatic?