engine revs on when changing gear....

[paulus2112]

I rang the Audi service dudes in my local dealership and asked them if it is normal that my A4 1.8 turbo engine continues to increase in revs when I'm accelerating hard and have lifted off the gas and depressed the clutch to change gear. Apparently this is normal, it's something to do with keeping the emissions in check, by burning off excess fuel...

Has anyone else come accross this? I once drove a brand new Astra 1.6SXI that did the same thing.

I'm still getting used to revvng the engine to around 5-6000 rpm then lifting off the gas just a tad before depressing the clutch to keep the engine from picking up another 300 or so rpm when I shift up a gear.

It's not really a problem, just seems unnecesarry! Why is there excess fuel in the engine anyway?? am I shifting up gears too soon?

I'm not used to driving petrol turbo cars, the last decent car I drove was a Civic Vti which used to bounce off the rev limiter before wheel spinning into the next gear on a damp road. I figure a different driving technique is required with the turbo but where as the Honda manual told me the best rpms to change gear for best acceleration, the Audi one is suggesting I change into higher gears at 2000 rmp for best economy - pah!

Any ideas?

[nunchukhamster]

New one on me. We have a B5 Passat with the 1.8T engine and it doesn't do that (the 150bhp version engine before it was remapped).

[paulus2112]

That's the same engine as my Audi, I drove a Passat with the same engine the other day, it didn't do it either...

[nunchukhamster]

That's the same engine as my Audi, I drove a Passat with the same engine the other day, it didn't do it either...

The only really common faults on those engines were the crappy MAF's, but I can't see how that would make it run on, normally makes them cough/splutter/lose power.

Might be worth having a look at www.tyresmoke.net, good VAG forum.

[paulus2112]

Thanks, I'll try there - I've been looking for a good VAG forum!

[macca]

Sounds a bit odd to me, though my Mondeo (when it's working :rolleyes:) does a similar thing if you change gear a bit quick, feels like you took your foot off the accelerator too slowly.

I figured it was a) a crappy Mondeo and b) it probably had a flywheel the weight of a small car that kept the engine revving for longer.

[paulus2112]

That sounds like the same thing, I think it's an effect of dual mass fly wheels modern cars use.

They act like a damper to prevent damage to the gearbox when shifting gears at high torque.

Audi recommend changing the fly wheel at the same time as a clutch, between £300 & £400 on top of the clutch!

I'd be interested to see if the Passat 1.8T has a dual mass fly wheel, I believe the Ford 2.2TDCi does.

I think the Audi technician I spoke to was talking from his rectum!

Interestingly there are clutch kits available that do away with the dual mass fly wheel!

[macca]

It could well be, they do add a lot of weight. My Mondeo is the 2.0TDCi, but all the TDCi's have the DMF.

It's not so much the damage caused, it's noise prevention and driveability. The modern diesel gearboxes are built to withstand the torque that the engine throws at it, so are heavier and clunkier.

My Supra also had a DMF, mainly to 'dampen the drivetrain'. Without it, my gearbox sounds like it has a whole set of spanners on a fast spin inside it. Lots of vibrations from the engine go through there to make it rattle, and that's a silky smooth straight six.

[macca]

As an aside, it would be interesting if they had put a DMF on the Audi but not the Passat.

Maybe they were trying to make the Audi smoother?

[Stavros]

Slightly different engine/car to you, but when i reverse my 1.4 n/a peugeot 207 (if i tap the throttle) it over revs when you take you foot off the pedal; I just put it down to it being french. Although i dont get this problem when driving forward. How odd

[paulus2112]

I spoke to a mechanic in a garage today and he said all the A4s like mine that he'd driven do this. He said the Passats dont but they have a different clutch - also some Audis have a solid flywheel too. I've stopped worrying about it anyway, I'll figure out when to change gear without it overrevving too much in time! I certainly seems to be normal behaviour... If my flywheel falls to bits I'll know I was wrong!

[macca]

Slightly different engine/car to you, but when i reverse my 1.4 n/a peugeot 207 (if i tap the throttle) it over revs when you take you foot off the pedal; I just put it down to it being french. Although i dont get this problem when driving forward. How odd
That's what you get for buying a cheese-eating-surrender-monkey car! :tounge:

[macca]

I spoke to a mechanic in a garage today and he said all the A4s like mine that he'd driven do this. He said the Passats dont but they have a different clutch - also some Audis have a solid flywheel too. I've stopped worrying about it anyway, I'll figure out when to change gear without it overrevving too much in time! I certainly seems to be normal behaviour... If my flywheel falls to bits I'll know I was wrong!

Sounds sensible, I don't think you've got anything to worry about.

You'll get used to it soon enough and your driving will adjust to it.

[Stavros]

That's what you get for buying a cheese-eating-surrender-monkey car! :tounge:

Haha, Touché mr macca *lowers head in shame* :D

[Princess]

My lude does it, rev counter goes right up when I press the clutch to change gear :S