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14:1 Compression Pistons for 202 to 210

Started by N/A-PWR , Dec 21 2012 07:52 PM

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#126 N/A-PWR

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Posted 26 March 2015 - 11:03 PM

Really Appreciate all your inputs,

 

but to throw more salt into the wound,

 

a Dome Piston has more surface area.  :)


#127 _oldjohnno_

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Posted 27 March 2015 - 06:58 AM

Imagine that the fuel molecules are chickens.

 

With a small surface area the chickens are crammed in and unhappy, unable to walk around and flap their wings.

 

But put them on a piston with a large and mountainous surface area and they are free to do some exploring and scratch around to their heart's content, to sing with joy and do some funky little chicken dances.

 

And we all know that a happy molecule is a productive molecule.

 

 

Hope this helps

 

So the piston dome should ideally be sculpted into a fun park? What about the inlet tract, surely there's scope there to make the journey more enjoyable? And isn't there something morally questionable about tricking them into blissful productivity before incinerating their innocent little lives away? Something about all this makes me uneasy..

 

Maybe.
My line of view is that a larger piston is slower and heavier and more inclined to rock.

 

Heat is transferred into usable energy, cooling a flame front would slow the combustion process, a good thing I spose if you had too much compression.

 

The further the flame front would have to travel would mean a longer duration to achieve complete ignition.

 

FWIW around 30% of heat is transferred into workable compression, pushing the piston down, around 30% is lost into the surrounds, into the cooling and oil system etc and around 30% of heat is lost right out the exhaust.

 

If you do the sums you'll see that a bigger cylinder has less surface area as a proportion of capacity than a smaller one. Having said that an undersquare cylinder has less heat loss area than an oversquare one of the same capacity, and as a result is more thermally efficient. Hence the current swing back to smaller bores and longer strokes. Obviously though they can only work if (1) piston speed can be held within reasonable limits and (2) the small bore doesn't limit breathing. For modern engines with "flat" four valve chambers (2) isn't normally a problem but with an old Holden six it most certainly is, so the bigger you can make the bore (within mechanical and structural limits) the better.


Edited by oldjohnno, 27 March 2015 - 07:00 AM.

#128 TerrA LX

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Posted 27 March 2015 - 07:17 AM

You are going to need them to get enough static compression to enable 14:1 dynamic.



Really Appreciate all your inputs,

 

but to throw more salt into the wound,

 

a Dome Piston has more surface area.  :)


#129 N/A-PWR

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Posted 27 March 2015 - 03:47 PM

Hello TerrA,
 
with the [email protected] duration Cam, we need 17.59:1 CR to get 14:1 DCR using a 10cc lump piston.
 

You are going to need them to get enough static compression to enable 14:1 dynamic.

 

here is the calculator:-

 

Attached File  Dynamic Calculation.jpg   114.87K   4 downloads


Edited by NA-PWR, 27 March 2015 - 03:55 PM.

#130 _oldjohnno_

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Posted 27 March 2015 - 05:00 PM

You want 14:1 dynamic???

 

That's a bit over-the-top isn't it?


Edited by oldjohnno, 27 March 2015 - 05:02 PM.

#131 _Bomber Watson_

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Posted 27 March 2015 - 05:16 PM

If it runs its certainly going to be a spectacular explosion. 


#132 EunUCh

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Posted 27 March 2015 - 05:30 PM

With a bit of adiabatic it might be well over 14 ?


#133 wot179

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Posted 27 March 2015 - 05:57 PM

Needs a pump on top as well.

#134 _Bomber Watson_

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Posted 27 March 2015 - 06:03 PM

frOck yeah 50 psi would go well with a 98% pop mixture. 


#135 EunUCh

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Posted 27 March 2015 - 06:07 PM

most guesstamets say 7.5-8.5 dcr is ok?

those poor chickens, how they gonna flap and squork and lay eggs with all that pressure  :)


Edited by EunUCh, 27 March 2015 - 06:10 PM.

#136 N/A-PWR

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Posted 27 March 2015 - 08:36 PM

Evening Old Johnno,

 

As you can see the calculation, that is using a 1mm head gasket,

 

so for starters, I can use the 1.6mm copper gasket,

 

which will lower the CR to 14:1, and DCR to 11.4.

 

You want 14:1 dynamic???

 

That's a bit over-the-top isn't it?

 

Attached File  DCR.jpg   115.71K   3 downloads


and leave the head chamber at 44cc.


#137 rodomo

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Posted 27 March 2015 - 08:48 PM

Go back to post 52...................He's running diesel

#138 _oldjohnno_

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Posted 27 March 2015 - 09:24 PM

Evening Old Johnno,

 

As you can see the calculation, that is using a 1mm head gasket,

 

so for starters, I can use the 1.6mm copper gasket,

 

which will lower the CR to 14:1, and DCR to 11.4.

 

Evening Dave. That sounds more reasonable.


#139 N/A-PWR

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Posted 28 March 2015 - 03:14 AM

Well that is the plan then,

 

will see where the valves interact in a set-up,

 

to work out the piston 10cc piston lump/s.  B)

 

Evening Dave. That sounds more reasonable.

 

.


#140 Dave6179

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Posted 28 March 2015 - 11:02 AM

Pull the pin and stand well back!

Would love to hear the crackle out the zorst pipe.


#141 _Macca97_

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Posted 28 March 2015 - 11:08 AM

might need a few rachet straps around the motor to keep it together


#142 _oldjohnno_

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Posted 28 March 2015 - 11:47 AM

Pull the pin and stand well back!

Would love to hear the crackle out the zorst pipe.

 

 

might need a few rachet straps around the motor to keep it together

 

So long as the tune is OK it'll be fine.


#143 TerrA LX

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Posted 28 March 2015 - 05:19 PM

Why the backdown on compression?
I thought you already bought your cam?


#144 _Lazarus_

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Posted 28 March 2015 - 05:30 PM

Johnno's pie shop uses more beef.


#145 EunUCh

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Posted 28 March 2015 - 05:41 PM

Dunno,tried one of calculators once and found the only way to get a dcr was by fitting the cam and measuring where the piston was up the bore @ 50 before closing with the other numbers at hand?


#146 N/A-PWR

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Posted 28 March 2015 - 05:50 PM

No problem's TerrA,

 

All in the interest's of science,

 

 have the Cam, which the short motor will still be the same design,

 

 by starting at the lower compression of 14:1 static for the test and tune,

 

 then can progress to the use of a 1mm gasket,

 

 which will boost the compression to 15.69:1 CR, 12.52 DCR,

 

 if that works, we can then remove 4cc's from the head chamber if still together.  :furious:

 

Why the backdown on compression?
I thought you already bought your cam?

 

Attached File  DCR 1mm.jpg   117.81K   4 downloads


#147 _Macca97_

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Posted 30 March 2015 - 06:50 PM

http://www.ebay.com....=STRK:MEBIDX:IT

 

This will give you the comp you need dave :)


#148 N/A-PWR

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Posted 30 March 2015 - 07:22 PM

That has been up for sale a few times hey Danny,

 

No good on a shelf, and if she was good, there would of been lot's made.  :furious:

 

This will give you the comp you need dave :)


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