The Singh Slash

[turbovanman²]

Grooves in pistons and grooves in chambers are apples and oranges.

Where were the dyno numbers of the grooves in the pistons and just pistons?

We know Frank, quit being such a downer,

He stated in the article that he has never used the grooves before so he has no idea if they work or not, sheesh man,

Its interesting article, thats what I got out of it,

[automotivebreath]

Tony Bischoff of BES Racing Engines grooved the pistons their BBC
for the 2005 EMS. They either didn’t know if it was beneficial or
didn’t care to say. I do like the way they used the piston dome
to redirect the fluid flow.

IMO you are looking at something that is very different. The reason
I say that is because the pistons go up and down in the bore. The
cylinder head is stationary and has a combustion chamber
with valves and the spark plug. These pistons have
domes and valve reliefs. These differences may seem very
insignificant but should be considered when making decisions.

Grooves in pistons and grooves in chambers are apples and oranges...

[Frank]

oh i understand completely that they are different. i also feel that they are more believable. recaping on the following post
http://www.turbo-mopar.com/forums/sh...4&postcount=32

[automotivebreath]

Believing or not believing is a very personal thing. The way I
like to look at it is something ether works or it doesn't, it doesn't
really what I believe.

I'm very familiar with how flame propagation is influenced by large
scale in-cylinder flow. The idea of boundary layer and how it is
influenced by the moving piston and stationary cylinder wall is
something that is very interesting and new to me. This picture
is great, it has stimulated the thinking on what is actually happening
inside of the expanding and diminishing cylinder.




Here's a picture you may find interesting, squish flow TDC compression.

[BadAssPerformance]

I have remained silent for long enough! Custon "Carroll Shelby" Combustion chamber slashes are the secret to all my horsepower!

[automotivebreath]

What design piston is used with that combustion chamber?

[BadAssPerformance]

Regular +40mm JE 2.2L piston... could not get JE to carve Shelby's signature into it

[automotivebreath]

The design of the crown, is it dished , flat top or reversed dome?

[BadAssPerformance]

Regular JE 2.2L pistons which are dished like the stock pistons.

Does it matter with the "Carroll Shelby" head mod?

[turbovanman²]

What design piston is used with that combustion chamber?

Thats the chamber Mike posted pics for me to groove. We use dished pistons to keep the compression low. I am sure with time and money we could redesign the piston for more compression with no detonation but at this point, kinda pointless I think.

[automotivebreath]

I don't understand why you say redesigning the piston for more compression
is pointless. If detonation wasn't a concern you could have compression and
boost for higher efficiency.

Anytime I use a dished piston, I'm concerned with squish to bore ratio. The
combustion chamber design pictured is good for use with a dished piston
because it has squish pads on both sides of the chamber. This allows a dished
piston with out lowering the squish to bore ratio considerably.


The reverse dome piston would be ideal, creating a mirror image of the
combustion chamber on the piston top would allow maximum squish action
with the low compression needed to control detonation. IMO highest boost
levels whould be obtained from this design.

... As the piston continues to move upward, the closer
it gets to TDC, the more we see air jets towards the center of the cylinder
and combustion chamber. This is where the next contributor comes in. #3 is
the interaction of the flow generated from piston moving up with the residual
swirl and on to a re interaction with the chamber's shape...

[automotivebreath]

... Flame will not propagate from in to out...

Frank, Thanks for providing the link to your previous post. When I read it the first
time I didn't fully understand your point. After reading it again, I now understand
and agree with much of what you are saying.

The only point I would like to add is what is happing 0-15 degrees ATDC of the
power stroke, something called reverse squish. When the piston begins to
descend and the combustion chamber size is expanding. The piston movement
creates a low pressure region in the squish zone pulling the flame front into the area.

Here's an illustration of how one designer solved a problen of poor end gas
propagation with a taper squish squish design.

[turbovanman²]

I don't understand why you say redesigning the piston for more compression
is pointless. If detonation wasn't a concern you could have compression and
boost for higher efficiency.

Anytime I use a dished piston, I'm concerned with squish to bore ratio. The
combustion chamber design pictured is good for use with a dished piston
because it has squish pads on both sides of the chamber. This allows a dished
piston with out lowering the squish to bore ratio considerably.


The reverse dome piston would be ideal, creating a mirror image of the
combustion chamber on the piston top would allow maximum squish action
with the low compression needed to control detonation. IMO highest boost
levels whould be obtained from this design.

Maybe but the cost involved would be stupid and would we really see any gains by it?

[automotivebreath]

Maybe but the cost involved would be stupid and would we really see any gains by it?

That's a very good point.

With the great combustion chamber design shown combined with the
increased combustion efficiency provided by the turbo, the benefits might
not be worth the extra expense.

[Frank]

Frank, Thanks for providing the link to your previous post. When I read it the first
time I didn't fully understand your point. After reading it again, I now understand
and agree with much of what you are saying.

The only point I would like to add is what is happing 0-15 degrees ATDC of the
power stroke, something called reverse squish. When the piston begins to
descend and the combustion chamber size is expanding. The piston movement
creates a low pressure region in the squish zone pulling the flame front into the area.

Here's an illustration of how one designer solved a problen of poor end gas
propagation with a taper squish squish design.

Most excellent diagram. It makes a lot of sense! However my only concern would be the lack of proper force vectoring. If you correct the flow into that void to allow for proper dispersal of gasses to reduce hot spoting, ensure complete combustion, etc, then you take away the flat area for the gasses to push downward. If it was the opposite taper, then we would be ok because the high and hot density is in the center, but as the problem exists, you have in proper expansion.

[automotivebreath]

...but as the problem exists, you have in proper expansion.

Used only as an illustration of in cylinder flows during a critical phase of the
combustion process, that being the build up to peak cylinder pressure. The
diagram does well to help one understand the dynamics of in cylinder flow at
the beginning of the power stroke.

IMO as it stands today, much advancement has been made but the ideal
combustion environment for the internal combustion engine is still unknown.
Perhaps the pent roof design is near ideal with a centrally located spark plug
high in the chamber. Utilizing a true flat top piston design (my favorite) would
generate near perfect force vectoring. The down side being small squish
area resulting from the valves consuming much of the chamber.

[Frank]

I think you would like this article.
http://www.theoldone.com/articles/Th...5FHead%5F1999/


Frank

[automotivebreath]

Larry Widmer, he's brilliant and light years ahead of the rest of the world. I will
go back and read the article again. On another forum he talks of the VW "super
squish" piston.

I used the "dome" to purge the dead area about the
intake-side of the chamber. Remember that this is a turbo piston, and while
we increased the compression (especially compared to other turbo pistons
that utilized dishes), the tendency for detonation was greatly reduced and
the engines realized considerably more power.

[automotivebreath]

I think you would like this article.

I appreciate Larry's work more now than ever before. The more we learn about
combustion the more sense we can make of his writings.

A properly engineered "combustion space" both dictates and permits
much higher compression (static and dynamic) with the outstanding ability to
prevent detonation, and so we feel that the "shape" is everything. Ideally, we
want the combustion rate to create maximum cylinder pressures well past TDC
to take advantage of optimum mechanical geometry for crankshaft rotation and
the process also needs to be fast enough to complete the "burn" prior to
opening the exhaust valve.

[Frank]

Ya he is loaded in the brain with good stuff. I have been trying to think up a good way to implement a good turbo piston for the 2.4L. However without a good engine dyno it will be too hard to prove results and even do R&D.


Frank