tried somender's grooves yet?

[Silverback]

AB- we’ve had this discussion before, and 1bolt, I have the strong feeling that Somender has stumbled over something interesting but he doesn’t really fully understand how it works, just that it does. This I feel is a large part of his sketchy description of what his happening (lets face it, there are tons of well explained principles that by the time you see them in most automotive forums they end up horribly twisted and confused, sort of like a game of telephone, imagine where you would be with something that is starting with an unclear explination?)

The interesting thing about this is that there are some that have seen dramatic improvements, and others that haven’t seen anything. WRT that I feel that there are at least 2 things going on.

First, there are different chamber shapes, layouts and quench distances, all of which affect the final result and what an optimum configuration will end up being. I believe that there is at least one documented instance where someone did the same as everyone else having good results and had no noticeable change, but then when he tried again and added multiple additional grooves and suddenly showed and improvement. I believe that I’ve also seen the opposite, where someone did more and did not see additional results.

Second, the grooves seem to make the biggest impact on low end, camshaft overlap effects, timing and detonation sensitivity. The fact is that like anything else, to see an mpg or an ET improvement at that point you need to optimize the rest of the combination for the results of the changes. If you make changes and then never use the results of the changes then you can’t expect to document a change, right?

The part that I’m stumped on, have gone back and forth with people about… is Somender’s recommendation of running larger than normal quench distances. I can’t make any sense of it, he doesn’t say why he recommends it anyplace (that I’ve seen), and I haven’t run across anyone that can explain it or document a positive change with a grooved chamber as you open up the quench distance.

As far as my interest in the subject… I’m convinced there is something to be learned here WRT to detonation control, flame front propagation, combustion heat, and the effects of fuel vaporization vs atomization in the chamber. All this adds up to some interesting implications for boosted engines and ones that end up heavily loaded at low rpms.

[KLR142]

Originally Posted by Silverback

The part that I’m stumped on, have gone back and forth with people about… is Somender’s recommendation of running larger than normal quench distances. I can’t make any sense of it, he doesn’t say why he recommends it anyplace (that I’ve seen), and I haven’t run across anyone that can explain it or document a positive change with a grooved chamber as you open up the quench distance.

I think the "sense" of running a larger quench clearance would be that it allows for the flame to travel in between there better, thus making the burn even more complete.

But like you, I'd think a tighter clearance to get as much as possible into the actual combustion chamber would be good, while only using the grooves to get mixture OUT of the quench areas.

Then again, running larger quench clearances would likely allow more of the combustion process to be distributed throughout the cylinder and apply force on the entirety of the piston, as opposed to just the center of it in the chamber.

So much going on...

AB(what's your name so I can stop calling you that? :-P), what piston to head clearances are you using normally? I can't remember if you said it's something you've toyed with or not. I really just want to do this once, and I'm tempted to stick with the norm of going as tight as I can get, but I'm also planning on grooving it...

[automotivebreath]

Originally Posted by KLR142

...AB(what's your name so I can stop calling you that? :-P), what piston to head
clearances are you using normally? I can't remember if you said it's something you've
toyed with or not. I really just want to do this once, and I'm tempted to stick with the
norm of going as tight as I can get, but I'm also planning on grooving it...

Hi Kyle,
I primarily use piston to head clearance to make final adjustments to the
compression ratio. Because I run large camshafts and normally run flat top pistons N/A,
I tend to go for a higher compression ratio and end up with a relatively tight
piston to head clearance. Not very scientific but when the camshaft is on the large
side for the compression ratio, a thinner head gasket can have a big impact.

With that said, I have tried various piston to head clearances for as little a 0.030" to
as much as 0.060", both with and with out the grooves. The benefits can be found
with both extremes. I use 0.040" to 0.050" as a target piston to head at engine
assembly with steel rods 7500 RPM max. This is a good safe target that won't result
in the piston smacking the head at RPM.

BTW, my name is Randy

[KLR142]

Originally Posted by automotivebreath

Hi Kyle,
I primarily use piston to head clearance to make final adjustments to the compression ratio. Because I run large camshafts and normally run flat top pistons N/A, I tend to go for a higher compression ratio and end up with a relatively tight piston to head clearance. Not very scientific but when the camshaft is on the large side for the compression ratio, a thinner head gasket can have a big impact.

In much the same way that grooves do, yeah? More friendly at lower rpm compared to an ungrooved head with a thicker gasket, not to mention less prone to detonation.

With that said, I have tried various piston to head clearances for as little a 0.030" to as much as 0.060", both with and with out the grooves. The benefits can be found with both extremes. (can you expand on that please?) I use 0.040" to 0.050" as a target piston to head at engine assembly with steel rods 7500 RPM max. This is a good safe target that won't result in the piston smacking the head at RPM.

BTW, my name is Randy

See bold above.

I'll be using flat top pistons and I haven't decided yet, but somewhere between 11:1 and 12.5:1 for the compression ratio. I'll probably be shooting for around .030" clearance and a 6500rpm or maybe slightly higher(at some point, stock FI limits me to 6250 right now). With a smaller bore that comes with my Volvo engine.

Tighter squish really becomes a good thing once you get it to .040" or smaller, according to what I've read, and the benefits taper fast at anything larger than that. This is without grooves of course, I haven't read much about people playing with different piston to head clearances while experimenting with grooves. Then again, there's so much to play with with the grooves alone...

You mention the benefits at both ends of the spectrum, do you mean thin without grooves and thick with? Or just in general?

Man, I can't wait to actually DO stuff to the head/compression of my car. It's going to change the beast soooo much. Along with fully programmable injection.

Thanks Randy!

[Silverback]

Originally Posted by KLR142

Tighter squish really becomes a good thing once you get it to .040" or smaller, according to what I've read, and the benefits taper fast at anything larger than that. This is without grooves of course, I haven't read much about people playing with different piston to head clearances while experimenting with grooves. Then again, there's so much to play with with the grooves alone..

the original patent and somender's page mention opening up the quench distance to something on the order of .070 or .080”. Somewhere he did have a page that was labeled as an explanation to why but I don’t remember it having anything along the lines of an explanation, just that it works better.

[automotivebreath]

"In much the same way that grooves do, yeah?"

From my experiences some benefits may parallel, in general results are not the same.

"can you expand on that please?"

With the application I have the most experience with (N/A drag race); grooved
cylinder heads delver with tight or wide squish clearance.

Personally I wouldn't go with "somewhere between 11:1 and 12.5:1 for the
compression ratio" for street use.

[KLR142]

It's a smaller cylinder with aluminum head, nothing like the V8s you're used to. I have friends that are already running around with a couple engines running around with 12:1ish compression on the street. Still on stock engine management crazily enough. We'll see what happens, between the tight squish and grooves I don't see myself having issues running 12:1 with the right camshaft and tuning on pump gas.

[ajunkyarddog]

I am under the impression that the Somender grooves optimize results in the idle to low rpm scale by increasing turbulence & mixture mixing that is normally problematic in a long overlap camshaft setup where the fuel isn't completely atomized. Once the piston speeds increase with rpm & the liquid fuel in the chamber is thoroughly atomized, the advantages of the grooves seem to yield a diminishing return. I have not personally experimented with the grooves because i haven't figured out how to use them with a Hemi type chamber & a dome piston configuration...there simply isn't sufficient quench area to compress the charge into jet effect offered by the grooves & the piston dome blocks out the path to the spark plug. My guess is that Somenders grooves provide primary benefit to the low rpm range concerns that include emissions quality, mileage, low end torque & uniform oxidation of the fuel mixture in a high compression motor. The grooves would probably be optimal in a diesel application.
I wonder if there are additional gains to be found by using a customized piston (with shaped extensions) that intensify the mixing at a higher rpm. Most racers are concerned about the peak HP numbers & this groove concept probably doesn't offer
any sufficient improvement to pique their interest.
I'm going to experiment with some limited grooving patterns in the Hemi chamber & i'll post if a realize any noticeable gains.

[Cammer]

I happened upon this site while surfing for Geo race engine parts:

Somender Singh grooves in a Geo Metro!

His grinding is horrible but the photos are good.

You can see how much quench/squish area is lost to the grooves.

His results seem to mirror others posted around the internet.

[BlackCat13]

My thoughts about the grooves and the squish distance is this.

The piston area above the rings including the bevel around the top of the piston and the head gasket gap contains fuel mixture to be burned. Tight squish (.040) forces turbulence into the main flame front but does little for igniting the perimeter area. Closing the gap 35* after the spark fires. This is quench as defined, quenching the uncontrolled burn of the perimeter gasses, stopping the detonation.

The grooves squirt mixture and cause turbulence not only into the main flame front burning in the combustion chamber, but also squirt towards the cylinder wall, displacing the mixture trapped in the piston perimeter.
If the squish distance is closed too much (.040), the perimeter area is cut off from the burning flame front and the possible burning of the mixture in the piston perimeter area is cut off.... quenched... stopping efficient burning.
It seems that opening the squish to .070 might allow that burn to continue whereas .040 might cut it off.

Just thoughts and speculation on my part, but I have been following the grooving for a couple years and I believe that it works.