Right ok, this came up in a thread I read today but....

When rolling down a hill and going at say 40mph in 5th and the engine goes taka taka taka taka and then stops, is it the pistons that have stopped going round or its it the combustion has stopped?

in other words what makes it go taka taka? combustion or moving engine parts?

wouldn't sound of the pistons going round be louder than the standard diesel taka taka...

wouldn't sound of the pistons going round be louder than the standard diesel taka taka[/i']...

true I meant up and down. good joke:thumbup:

If th epistons stop and the car is in gear, its probably stopped because you've stalled

Errrr... When "coasting" i.e. with the clutch in but the car is still moving, the car has to pump fuel into the engine to keep the engine running.

When travelling down hill without coasting, the momentum/gravity is making the wheels turn, keeping the gearbox moving and hence turning the engine. No fuel is needed for this to happen - but the engine is still running, just using no fuel.

Hope this kind of answers your question Chris.

I thought it was Mil that made the vRS go Taka Taka?? :P

so it's the explosions that make the car go taka taka and not the pistons moving up and down (or the tappets as in my clio 1.2)

Chris - the explosions are somewhat inextricably linked to the pistons going round

Right ok' date=' this came up in a thread I read today but....

When rolling down a hill and going at say 40mph in 5th and the engine goes taka taka taka taka and then stops, is it the pistons that have stopped going round or its it the combustion has stopped?

[/quote']

If your rolling down a hill in gear and pistons stop 'going round' then the driven wheels will also stop 'going round'....

Is the "taka taka" sound something associated with diesel engines only ?

My car goes brrrrrrroooooooaaaaaaarrrrrrrrrrr

Even Octavia doesnt go "taka taka" - unless at idle and th echarcoal filter is making some noise.

the fuel dosn't cut when you are coasting. otherwise the engine would stop.

but it is true that less fuel is needed in one the overrun.

maybe I have taken what you all have said in a different way to what it was proposed but I still don't think you have answered my question.

what I am on about occurs after all pedels are released and rolling down an incline in gear. When you press the accelerator you hear the engine note increase then letting go of the accelerator makes the noise slightly less and more constant and then after a couple of seconds nothing........it sounds as if the engine has stopped but obviously hasn't as it's in gear....maybe it's just me but it is that silent it seems like the engine has stopped all together. That is why I am asking such a strange question.

Shall I just get my caot?

maybe it's just me but it is that silent it seems like the engine has stopped all together.

Think there's a fair bit of soundproofing, such that even though the engine is running it's fairly inaudible.

In a diesel engine, one of the causes of the "knock" noise the rapid pressure rise in the cylinders at combustion - if there's less fuel, the pressure rise is less, hence the engine will be quieter...

Rob.

Cheers rob. sounds like a plausible answer.

it's just in my last petrol car you always notice the engine what ever it's doing, not in the diesel you can hear it most of the time but when rolling in gear it's inaudible and so much quieter than when stood still when idling.

It sound as it is the combustion + pressures causing the taka taka taka noise so when going down the hill no diesel is going into the engine the engine is carried round by the momentum of the wheels and gearbox etc and therefore no pressure in the piston chamers and therefore even more silent than a petrol due to the sound proofing needed for diesels.

So at times the diesel is quieter than a petrol:P

Well, there should still be some fuel going into the cylinder AFAIK, just not so much so the pressure rise at combustion is less.

You'd have to compare like for like on petrol vs. diesel - Clio's aren't renowned for being quiet cars, but the petrol Fabias I've driven have been fairly reasonably soundproofed... :P

Rob.

a diesel engine is only quieter than a petrol when the petrol is running and the diesel isn't.

take a look under the bonnet at how much sound proofing your diesel has compared to your old petrol clio, this is alos what makes quite a difference to the weight

It's the incredibly high pressures used by the PD system that really add to the noise levels, and it's definitely been worthwhile sticking a bunch of additional soundproofing into the car/underbonnet

The explosions caused by combustion come out as the 'taka taka' noise...in other words, the 'taka taka' are the explosions.

I just realized I said the same thing twice.

The explosions caused by combustion come out as the 'taka taka' noise...in other words' date=' the 'taka taka' are the explosions.

I just realized I said the same thing twice.[/quote']

thanks Mil!

I thought it was this. Thanks for your help

lets have a point system for people who post good answers to questions:rofl:

Taka very much