What's On Your Bench? 2/15/13

[thomas1]

It would retard it.

Would it really change at all? If you're firing the plug 10° BTDC that is dictated by the flywheel's relationship to the crankshaft, regardless of the actual distance the piston is below the combustion chamber, correct?

 

[Mastermind]

Would it really change at all? If you're firing the plug 10° BTDC that is dictated by the flywheel's relationship to the crankshaft, regardless of the actual distance the piston is below the combustion chamber, correct?

And there's the thing........cutting the squish band changes the relationship between the spark plug electrode and tdc......

The end of the plug is actually closer to the piston at tdc. See?

 

[DSS]

Would it really change at all? If you're firing the plug 10° BTDC that is dictated by the flywheel's relationship to the crankshaft, regardless of the actual distance the piston is below the combustion chamber, correct?

Yeah but he's thinking the piston is going to be farther up in the jug so it isn't actually 10 * BTDC anymore.

Do I have to explain everything?

 

[3000 FPS]

Would it really change at all? If you're firing the plug 10° BTDC that is dictated by the flywheel's relationship to the crankshaft, regardless of the actual distance the piston is below the combustion chamber, correct?

You are correct I was just messin. TDC is still the same and does not change because the cylinder is lower and it sure does not make the plug fire any earlier. The only difference is the piston goes up into the cylinder further bumping up compression and I am sure Mastermind knew this when he asked the question. So he was just messin too.

 

[barneyrb]

Dan I wonder about something.........would lowering the jug advance ignition timing since the plug is actually closer to the piston?

On my bench are ideas see.

Not going to change ignition timing at all by dropping the jug. Top dead center ain't changing

 

[Mastermind]

Are you guys sure?

This is fun.

 

[3000 FPS]

Are you guys sure?

This is fun.

I am sure but two days I may not have been.

 

[dozerdan]

Thanks........did Brad report a post again?



I don't worry too much about either.....hell I don't worry about anything.

Dan I wonder about something.........would lowering the jug advance ignition timing since the plug is actually closer to the piston?

On my bench are ideas see.

The piston is going to be at top dead center just like it was before you cut the jug. Top dead center wont change.

What will change is the position of the plug and it will be a little closer to the piston coming up on TDC. There would be a very very slight advance on the ignition timing.

If I put a hotter plug in my car will I get more heat out of the heater? LOL

I don't worry about anything either, was just playing with you.

Later
Dan

 

[Trx250r180]

best way to tell is put a timing light on a saw before and after the squish band is cut ,see if it moves at all

 

[DSS]

TDC is the same but the piston is closer to TDC when it fires, right.

Isn't that the same as advancing the timing?

 

[bucknfeller]

TDC is the same but the piston is closer to TDC when it fires, right.

Isn't that the same as advancing the timing?

TDC is TDC, it doesn't matter if the plug is .020" or 20" from the piston.

 

[Mastermind]

best way to tell is put a timing light on a saw before and after the squish band is cut ,see if it moves at all

 

[Mastermind]

TDC is TDC, it doesn't matter if the plug is .020" or 20" from the piston.

Then why is it said that an extended reach spark plug will advance timing lead? :msp_unsure:

 

[Trx250r180]

when do we get to see the video to prove your theory ?:msp_tongue:

 

[DSS]

TDC is TDC, it doesn't matter if the plug is .020" or 20" from the piston.

20" is an awful lot of squish. :msp_unsure:

 

[Mastermind]

when do we get to see the video to prove your theory ?:msp_tongue:

Mechanically nothing will change. Like has been said.....TDC is still TDC.......but the plug is still closer to the piston so it will act as though timing has been advanced slightly.

 

[Trx250r180]

on one of my atv engines years ago ,when i got it back the builder included an aluminum spacer for under the spark plug ,maybe .025-.030 thick off memory what would be the porpose of that spacer ? i thought it was so piston didnt hit the plug ,maybe more too it than that

 

[Jacob J.]

So am I.

But you're not cheap.

 

[Steve NW WI]

on one of my atv engines years ago ,when i got it back the builder included an aluminum spacer for under the spark plug ,maybe .025-.030 thick off memory what would be the porpose of that spacer ? i thought it was so piston didnt hit the plug ,maybe more too it than that

Old trick used to "index" the plug, to point the electrode in a preferred direction.

 

[Mastermind]

on one of my atv engines years ago ,when i got it back the builder included an aluminum spacer for under the spark plug ,maybe .025-.030 thick off memory what would be the porpose of that spacer ? i thought it was so piston didnt hit the plug ,maybe more too it than that

It could be to index the plug so that the gap is facing down.........old racer trick to get that little extra.