burn slots in squish area ?

[Cammer]

We are creating good dialog within this thread.

Tell us details about your groove (slot) experiences and we may be able to form a hypothesis of how they work.

What are some observations relating to grooves/slots cut into heads?

Do engines with grooves/slots idle better, have better throttle response, or have reduced timing demands?

Are you rejetting or reworking carburetor after installing grooved/slotted heads, and if so, are you leaning or richening?

What is the correlation (if any) between groove/slot location and results?

Has anyone studied spark plug readings and life when used with grooved/slotted heads?

Are the grooves/slots primarily used on squish type applications?

Has anyone changed piston configuration to complement grooved/slotted heads?
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[automotivebreath]

All indications are that combustion is more complete. Idle quality when running
a camshaft with a long overlap period is much improved, oil runs considerably
cleaner same goes for spark plugs. Combustion burn patterns indicate further
burning into the squish area. Carbon traces in the intake tract show reduced
reversion.

Ignition advance requirements are reduced primarily at at low RPM. All
carburetor circuits can be leaned out showing reductions in fuel consumption.

I have done numerous different groove locations, I have no conclusive
evidence indicating what is best. On a typical wedge head the valves limit
the potabilities. Results when grooving heads with large squish areas are
more pronounced.

This may seem a little abstract, I commonly run my engines into auto-ignition
conditions for extended periods of time. With grooved cylinder heads this
is much easer to control with out suffering engine damage.

These pictures are from a friends engine after one year run time, high compression
SBC running on the edge. Carbon traces were mostly a very thin blue film that would
easily wipe off

[Cammer]

I am trying to find some science in how a tiny groove can produce the effects you report.

I just can not grasp the logic.

Perhaps if I could afford a little nitro2 technology we could get to the heart of this groove thing.

I will try to test grooves when Spring gets here and I can dig out of the snow and my workload!

Frostbite is painful to an old man! No complaints- still have all my digits!

I do have to find a new name for the old hound- maybe something like Tripedal.

He can still outrun me!
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[automotivebreath]

Originally Posted by MAP

I'm trying to understand the physics of what may be at work here. I can see
that the one-dimensional-like feature of the groove can pose a barrier to
transverse flow, hence the reversion benefit. Is that the thinking here?

This has been discussed on several occasions, I have witnessed the
reversion benefit, no evidence that this benefit was a result of in-cylinder
flow patterns created at the end of the exhaust stroke.

Originally Posted by MAP

But this near one-dimensionality can also accentuate longitudinal flow. If so,
then is the groove intended to "accumulate" squeezed-out charge from the
quench area as the piston nears TDC, and then eject it in the direction of the spark plug?

So is the thinking, flow is a result of pressure differential. If a differential
exist between the squish area and the groove, flow is generated into the
groove. If a differential exists between the groove and the chamber this flow
is directed into the chamber.

Originally Posted by MAP

If so, then its efficacy would seem limited. In general, from a minimal-energy
condition, it would seem that most of the compressed charge in the quench
area as the piston nears TDC, would take the shortest geometrical route
into the chamber volume proper. From the picture, it would seem that the
majority of the charge would thus actually bypass the groove, and instead
make a beeline into the chamber.

I agree flow is a result of pressure differential and will take the shortest route
to equalize, so the modified squish pad does not eliminate squish action as
we know it. .

Originally Posted by MAP

If this thinking is correct, then why not create a system of grooves,
somewhat akin to the typical tread pattern on wide tires to eject water, so
that a greater fraction of the compressed charge in this area is guided
toward the main groove, thus accentuating the strength of the ejected
stream headed toward the spark plug?

This has been done this successfully, the idea is to redirect more of the
squish flow into a primary groove to enhance a theoretical “jet action”

Originally Posted by MAP

I know that adding grooves reduces the overall quench/squish action given
that this increases the average height of minimum compression in this area,
but perhaps a better optimization than currently known, or practiced, exists?

Most people see this and instantly want to improve it, I am no diffrent. My
view point is when ever you archive some success you should analyze the
changes made and look for opportunity for further improvement. Given the
fact that the internal combustion engine is about 25% efficient, plenty of
room for improvement exists.

[seattle smitty]

I was initially skeptical about the grooves because I saw no good test results, just annecdotes from enthusiasts who seemed rather mechanically and technically challenged, and who were reporting enormous improvements. I still haven't seen a good test (maybe I've missed it), but now I'm reading favorable reports on grooving from much more credible-sounding people, so I've reconsidered.

We know from what the factories have done that inducing swirl and tumble during the intake stroke has positive effects.

We know that creating a tight-fitting squishband has a positive effect again, at the top of the stroke.

In one motor I know of (because I own one), the Mitsubishi G63B 2.0L SOHC four, the factory decided that a top-of-the-stroke swirl was useful enough that they employed a device they called a "jet-valve" to induce that swirl, even though it involved extra machining and considerable complexity.

IF Singh's grooves really create a top-of-the-stroke swirl and/or tumble, I can easily see how they would have a positive effect. At this point, my question is similar to Cammer's: Given the several groove layouts we have seen here and on Singh's own site, and given that the enthusiasts always report wonderful results regardless of which groove layout they use, what can we say about the physical effect actually produced? Answer: nothing, we are still just guessing.

My GUESS is that some variety of groove(s) (and I haven't seen any that look right to me) aimed off-center to induce a slight, quick swirl, might add to the value of a good squishband . . . but it's nothing but a guess.

But I'm about to try it!

[Kenny]

Hey guys, I am thrilled to find an engine site of this caliber. Now for some questions that are going around in my mind. Could this simply be a function of having three smaller, almost equal, quench areas with a secondary ignition source(the slot), firing the adjacent squish areas? Isn't the squish area just a necessary evil to allow an open combustion space for a reasonably, unobstructed flame front while keeping compression up? I have it in my mind, that maybe the quench is also an obstruction to the flame front, just less detrimental to our goals than crazy domed pistons in an open chamber.

I would be interested in trying an experiment on one of my four valve engines, that has more of a quench band with two small flats. I would like to machine small angled grooves of decreasing depth from the chamber wall, toward the cylinder wall. Kind of an imaginary starburst pattern, if you will. That would create multiple small squish areas while the slots allow ignition of all the adjacent areas.

I am not convinced that the chamber cares whether this is on the roof or floor, so I will probably modify a piston so I can do an A-B comparison at a reasonable cost. Maybe I could come up with a pattern that resembles a pineapple grenade, so there would be some poetic justice if I blow this thing up.

I would really like to see something like this excite the mixture in the chamber in a way I can quit giving up flow for swirl. Porting for increased swirl makes my head hurt.

If I am oversimplifying please take it easy on me, I might be sensitive....

Thanks for your time,
Kenny

[Cammer]

I visited Larry Widmer's website to check on some Honda engine parts and noticed he uses a slot on some of his pistons.

He calls them reflector slots.

The plot thickens!
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[Kenny]

Originally Posted by Cammer

I visited Larry Widmer's website to check on some Honda engine parts and noticed he uses a slot on some of his pistons.

He calls them reflector slots.

The plot thickens!
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I looked around some of his stuff, but could not find what you have mentioned. Any chance you could post up a link?

[Stan Weiss]

This is all guessing on my part. I believe on the up stroke the grove helps direct the squish velocity to cause better mixture of the gas air and flame front movement. At the time after squish velocity has peaked, which is still BTDC we have a pressure differential where the squish area is lowering quick and the cylinder is 30 degrees or so into its burn. At this point the movement is back into the squish area. How deep do you cut your grooves?

Lets look at how much piston movement we have from 15 degrees BTDC to 15 degrees ATDC. In this test engine Bore = 4.0", Stroke = 3.25", Rod Length = 5.7" and ci = 326.73. The piston moves from .070908" down in the hole to TDC and back to .070908" down in the hole during this very important time.


Bore.=.4.0...Stroke.=.3.25...Rod.Length.=.5.7...RP M.=.6500
Wrist.Pin.Offset.=.0.0
Rotation.Time.of.crank.per.degree.in.Milliseconds. ...0.0256410
Rotation.Time.of.crank.per.rev.in.Milliseconds.... ...9.2307692
Crankshaft.rev's.per.Second....................... ...108.3333333
Crankshaft.Degrees.at.which.Rod.and.Crank.are.90.D egrees.74.0878

Crank......Piston.....Crank.......Rod....Cylinder. ..Cylinder
Angle......Travel......Rod.......Bore.....Volume.. ...Volume
Degree.....Inches.....Angle......Angle......CI.... .....cc
-ATDC.
345.0000....070908.-160.76852..-4.23148...0.89106...14.60184
346.0000....061842.-162.04523..-3.95477...0.77713...12.73492
347.0000....053382.-163.32305..-3.67695...0.67082...10.99275
348.0000....045532.-164.60191..-3.39809...0.57217....9.37619
349.0000....038295.-165.88173..-3.11827...0.48123....7.88602
350.0000....031676.-167.16241..-2.83759...0.39806....6.52297
351.0000....025678.-168.44390..-2.55610...0.32268....5.28771
352.0000....020303.-169.72610..-2.27390...0.25513....4.18085
353.0000....015554.-171.00895..-1.99105...0.19545....3.20293
354.0000....011433.-172.29235..-1.70765...0.14368....2.35442
355.0000....007943.-173.57622..-1.42378...0.09982....1.63575
356.0000....005086.-174.86050..-1.13950...0.06391....1.04727
357.0000....002861.-176.14510..-0.85490...0.03596....0.58926
358.0000....001272.-177.42993..-0.57007...0.01598....0.26195
359.0000....000318.-178.71493..-0.28507...0.00400....0.06549
360.0000....000000.-180.00000...0.00000...0.00000....0.00000

Crank......Piston.....Crank.......Rod....Cylinder. ..Cylinder
Angle......Travel......Rod.......Bore.....Volume.. ...Volume
Degree.....Inches.....Angle......Angle......CI.... .....cc
-ATDC.
....0000....000000..180.00000...0.00000...0.00000. ...0.00000
..1.0000....000318..178.71493...0.28507...0.00400. ...0.06549
..2.0000....001272..177.42993...0.57007...0.01598. ...0.26195
..3.0000....002861..176.14510...0.85490...0.03596. ...0.58926
..4.0000....005086..174.86050...1.13950...0.06391. ...1.04727
..5.0000....007943..173.57622...1.42378...0.09982. ...1.63575
..6.0000....011433..172.29235...1.70765...0.14368. ...2.35442
..7.0000....015554..171.00895...1.99105...0.19545. ...3.20293
..8.0000....020303..169.72610...2.27390...0.25513. ...4.18085
..9.0000....025678..168.44390...2.55610...0.32268. ...5.28771
.10.0000....031676..167.16241...2.83759...0.39806. ...6.52297
.11.0000....038295..165.88173...3.11827...0.48123. ...7.88602
.12.0000....045532..164.60191...3.39809...0.57217. ...9.37619
.13.0000....053382..163.32305...3.67695...0.67082. ..10.99275
.14.0000....061842..162.04523...3.95477...0.77713. ..12.73492
.15.0000....070908..160.76852...4.23148...0.89106. ..14.60184

[Cammer]

I can only reference website page as Larry controls rights to his website content:

The Old One - Energy Dynamics

Page down to piston photo to see slot and check Larry's Roller-Wave piston design for more clarification.
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Thank you to all posters for interesting and thought provoking conversation!
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