Running engine (diesel) with the ignition turned off

[RichardS]

Seriously ? How do you measure the height of a dished piston ?

Simple. The height of a dished piston is determined by filling the dish with minestrone soup and then extracting all beans and all the noodles.

The formula is then: Total Noodle Length / Number of Cannellini Beans = Dished Piston Height.

Richard

 

[JumbleDuck]

The level of stupidity now exceeds my willingness to post threshold, i can't even be bothered to read most of the latest, inane drivel.

 

[penberth3]

...….Are you really just a fitter, rather than an engineer or even a mechanic?......

I don't like to make assumptions, so can I ask where you are on this list. Apprentice trained? HNC? Engineering Degree?

 

[rogerthebodger]

I don't like to make assumptions, so can I ask where you are on this list. Apprentice trained? HNC? Engineering Degree?

Or Chartered Engineer.

 

[38mess]

I don't know much about diesel engines, but one thing has stuck in my memory from my Navy days is the shape of a piston head depends on type of injection, direct or indirect combustion..ok I'll get my coat

 

[penberth3]

I don't know much about diesel engines, but one thing has stuck in my memory from my Navy days is the shape of a piston head depends on type of injection, direct or indirect combustion..ok I'll get my coat

Already been mentioned, somewhere in the 200 posts.

 

[38mess]

Already been mentioned, somewhere in the 200 posts.

Thanks, I only started reading this when people with little knowledge tried to put the experts to rights usually ends in tears

 

[penberth3]

Thanks, I only started reading this when people with little knowledge tried to put the experts to rights ☺ usually ends in tears

You're right, about the pistons and the tears.

 

[Beneteau381]

Correct, not at all. It would only have an affect if you had a differently shaped cylnder head, eg a hemi-, a D-shapes or wedge, where you would be reducing the size of the combustion chamber.

The shapes will determine the compression ratio, and what determines the compression ratio.

It also doesn't change the CR very much, and can leading to other issues to resolve, eg relating to the valve geometry and so on.

It?

 

[Beneteau381]

I don't like to make assumptions, so can I ask where you are on this list. Apprentice trained? HNC? Engineering Degree?

He used to race!

 

[convey]

It?

The skimming of heads in order to increase compression ratio, emphasis on the other issues it goes on to cause.

 

[Beneteau381]

The skimming of heads in order to increase compression ratio, emphasis on the other issues it goes on to cause.

Changing valve geometry?

 

[convey]

Valvetrain geometry, exhaust and carb manifold issues, engine mounting etc, eg the angles between the valves/rockers/pushrods/cams.

Please accept that given the variety of valvetrain designs, eg chain, belt, desmodromic etc I can't included every variable in every post but, yes, similar issues exist.

Seriously ? How do you measure the height of a dished piston ?

Which do you mean, the pin height, the crown height, or the volume of the dish or bowl?

Part of the problem here is the lack of specificity and accurateness in your communication, your sarcasm is just defensiveness and a person weakness.

How to measure the volume of piston dish or bowl - an essential part of the shape as far as determining compression ratio - is very easy.

There are two primary ways, do you know what they are?

(cue: another 10 page of repeating the mantra that piston shapes do not affect compression ratio)

 

[convey]

Mark Twain

I am sorry if the discussion is going above your head.

If there is anything you don't understand, ask a specific question and I will explain it to you.

But, at the very least, I hope you've grasped, contrary to what your friend believes, that the shape of the piston, combustion chamber and deck height all DETERMINE the compression ratio.

 

[Beneteau381]

Valvetrain geometry, exhaust and carb manifold issues, engine mounting etc, eg the angles between the valves/rockers/pushrods/cams.

Please accept that given the variety of valvetrain designs, eg chain, belt, desmodromic etc I can't included every variable in every post but, yes, similar issues exist.


Which do you mean, the pin height, the crown height, or the volume of the dish or bowl?

Part of the problem here is the lack of specificity and accurateness in your communication, your sarcasm is just defensiveness and a person weakness.

How to measure the volume of piston dish or bowl - an essential part of the shape as far as determining compression ratio - is very easy.

There are two primary ways, do you know what they are?

(cue: another 10 page of repeating the mantra that piston shapes do not affect compression ratio)

why would skimming the head change my valve train geometry?

 

[black mercury]

Not another quiz.
Not fair convey that's two questions you have asked.
How about explaining why bowls in pistons of direct injection diesel engines have become shallower and wider in recent years and the advantages of having a shallower and wider bowl?

 

[black mercury]

why would skimming the head change my valve train geometry?

It will if the pistons hit the valves if too much has been removed.

 

[JumbleDuck]

why would skimming the head change my valve train geometry?

In a pushrod engine it moves the rockers a little nearer the cam followers, but not exactly a major effect.

 

[PaulRainbow]

Which do you mean, the pin height, the crown height, or the volume of the dish or bowl?

Part of the problem here is the lack of specificity and accurateness in your communication, your sarcasm is just defensiveness and a person weakness.

As my comment was in response to one of your idiotic "deck height" and "squish" remarks, it's pretty obvious what i meant.

The problem isn't my accuracy, it's your lack of knowledge and understanding. What did people like you do before Google ?

So, answer the question, where do you take the measurements for deck height and squish with a dished piston ?

 

[convey]

why would skimming the head change my valve train geometry?

By skimming a head you, in essence, lengthen the pushrods. The pushrods then tilt (or rotate) the rocker arms down (round) more on the valve tips, changing the position on which they push on the valves. If you're pushing on one side of the tip rather than the centre, the valve faces will then be pushing onto the other side of the valve seat, encouraging wear on the guides and seats (they'll start to cut into one side, pocket and not seal so well). In short, all the angles (geometry) change slightly requiring management in someway, eg using adjustable pushrods or shorter custom fixed pushrods, to match how ever much you took off the heads. In extremis, they might even start tapping on parts of the engine.

Wear on the guides and seats will then lead to other problems.

It's all about clearances and tolerances. An engine and its components will be design to operate within a range of tolerances, even with self-adjusting hydraulic systems (they can only adjust so much). So a light skim to level a face or after a weld might remain within tolerances, but a heavy skim for the sake of performance will.

Of course, if your valves are chain or belt drive such as with overhead cams, it's a different scenario.