S60 G/box: 2WD: car rolls down driveway when left in gear

[Blue 8]

Originally Posted by smudgethecat

Your having a giraffe here surely, firstly gravity is the force that will cause the car to roll downhill, secondy, er yeah ,of course the corresponding intake and exhaust valves will be closed depending on what part of the cycle that cylinder is at , others of course will have valves open, as said read up a bit, its **** all to do with butterfly valves ffs, its down to the higher compression found in diesel engines resisting the forces trying to turn the engine which make it harder to shove a diesel engined car along thats left in gear, whether that shoves from your shoulder, or gravity trying to push it downhill it doesnt matter , hope that clears it up for you.

Nah i doubt it .

[Dynosaur]

Originally Posted by smudgethecat

Your having a giraffe here surely, firstly gravity is the force that will cause the car to roll downhill,

... no sh*t, Sherlock!

Originally Posted by smudgethecat

secondy, er yeah ,of course the corresponding intake and exhaust valves will be closed depending on what part of the cycle that cylinder is at , others of course will have valves open,

... yeeees, so if some valves are open, it can't be the valves that are stopping the engine turning, can it ?
Nooooh, that's right - it's the compression rings.

Originally Posted by smudgethecat

as said read up a bit, its **** all to do with butterfly valves ffs,

... from which it's obvious that you haven't understood my comment that whether or not engine compression is stopping the engine from turning is NOT the issue.

Indeed, it's obvious you haven't read my original post or much of this thread.

I replied to a member who'd found that his diesel cars don't prevent rolling when in gear (as well as his petrols have) that it's possibly down to the difference between petrol and diesel engines : - the butterfly valve or lack thereof.
Only a wombat would imagine that I was only referring to the butterfly valve - since if it weren't engine compression stopping diesel cars rolling down hill, putting them in gear would be absolutely pointless!

Originally Posted by smudgethecat

its down to the higher compression found in diesel engines resisting the forces trying to turn the engine which make it harder to shove a diesel engined car along thats left in gear, whether that shoves from your shoulder, or gravity trying to push it downhill it doesnt matter , hope that clears it up for you.

From which, you've failed even to understand his point that diesels are worse than stopping in-gear rolling than petrols

I don't think it's me who needs things clearing up for him.

[smudgethecat]

Originally Posted by Blue 8

Nah i doubt it .

suspect your right blue i blame the fact a lot of schools dont include physics in the options available, old dyno likely opted for media studies

perhaps the easist way to get it through to him is to get him to try and shove a d5 in first gear then try the same with say a t5 it wil soon become obvious which engine is offering more resistance and guess what? if you find it harder to shove the diesel then so will good old mr gravity

[Dynosaur]

Originally Posted by smudgethecat

suspect your right blue i blame the fact a lot of schools dont include physics in the options available, old dyno likely opted for media studies

Seems to me we're starting from very different points here.

I made the rather basic omission of assuming that you knew enough to realise that it was understood that we weren't discussing whether engine-compression was preventing in-gear rolling - and that what was being discussed is why petrol and diesels differ in their capacity to do this.

But clearly, I presumed too much common sense on your part.

But since you ask, I'm a B.Eng (Hon.s) - Mechanical Engineering : Class of 1997 - Kingston University.

Perhaps it was you you were thinking of, when you mentioned mejia studies ?
'Cos is obviously wasn't English you studied.

[zx6rman_uk]

Originally Posted by Dynosaur

... no sh*t, Sherlock!

... yeeees, so if some valves are open, it can't be the valves that are stopping the engine turning, can it ?
Nooooh, that's right - it's the compression rings.

In fear of sparking WWIII..........

I assume were talking about piston rings? I'm fairly mecahnically minded and would presume that the compression rings dont offer much resistance at all. The gearbox and cam would surly present more of a resistance than the compression rings alone?

[Dynosaur]

Originally Posted by zx6rman_uk

In fear of sparking WWIII..........

I assume were talking about piston rings? I'm fairly mecahnically minded and would presume that the compression rings dont offer much resistance at all. The gearbox and cam would surly present more of a resistance than the compression rings alone?

Google is your friend.

[zx6rman_uk]

Originally Posted by Dynosaur

Google is your friend.

Oh noo im not falling for that one, Google has got me into way too much trouble in the past

[smudgethecat]

Originally Posted by zx6rman_uk

In fear of sparking WWIII..........

I assume were talking about piston rings? I'm fairly mecahnically minded and would presume that the compression rings dont offer much resistance at all. The gearbox and cam would surly present more of a resistance than the compression rings alone?

i wouldnt waste any more time mate .

[Dynosaur]

Originally Posted by zx6rman_uk

Oh noo im not falling for that one, Google has got me into way too much trouble in the past

OK, well the gearbox doesn't offer much resistance - or it would impede progress and generate huge amounts of heat. It's just a power-transferance device between engine and wheels that offers only minimal, internal-frictional resistance (which is what transmission oil is for).

And cams are only a mechanism for transferring power from the crankshaft to open the valves. The only resistance they offer is bearing friction - which with circulating engine-oil, is engineered to an absolute minimum.

[Dynosaur]

Originally Posted by smudgethecat

i wouldnt waste any more time mate .

From which, it can be taken that I've cleared things up for you a little.

For someone who's been a member here for less than five days, you're a cocky little ignoranus.