Sorry, I did perform a search. I guess not just the "right" one. All I kept finding were discussions about beefed up transmissions and "smoking" questions. If my research skills were better, I would not need to ask about Mystery Carburetors!

Thank you for your indulgence.

The wheel may not need reinventing, but there is apparently an ever present need to explore its deployment. Popular Science and Popular Mechanics seem to cover the subject every month.


“Design to Improve Turbulence in Combustion Chambers by Creating a Vortex”

Somender Singh says a radical design change to the face of combustion chambers by forming grooves, channels or passages through the squish areas will further enhance in-cylinder turbulence followed by multi flame front combustion. Do-it-yourselfers might consider cutting some grooves in their chambers to approach the effect.
See:
http://pesn.com/2005/10/13/9600187_Design_to_Improve_Turbulence_in_Combustion_Chambers/

Others have evidently unlocked the secrets of combustion chamber modifications too:


http://powrehaus.com/

Curl if you are seriously interested do a search under my username. I posted a few times over the last few months about this topic...

Back in March I believe. Metric Mechanic has some unique ideas IMO and not everyone buys into them. Also it is widely believed that they have been known for overstating their HP numbers (from what I have read on other forums but not from actual experience).

IMO if you are going to use MM go with their whole entire system from swirl valves to combustion chamber to pistons... all or nothing IMO.
_________________
BMW-Yachtsport
'80 Vespa p125x
'07 Accord DD (selling it)
2574356 - in need of restoration

I have a couple of old heads that have been previously modified (one has dimples like a golf ball.) I was not responsible for the modifications and have no idea whether they were effective.

I saw the MM pictures and wondered, if the modification is a positive step, why didn't manufacturers' mass produced heads have similar modifications. I am wholly uneducated on the subject and I no opinion on the subject.

Interestingly, as a result of this thread, someone has "allegedly" received a patent for such a modification.
http://www.popsci.com/popsci/futurecar/19b09aa138b84010vgnvcm1000004eecbccdrcrd.html

Thanks again.

I ran it by a couple of guys who are on the cutting edge of cylinder head design. Everything from Junk.. to no f'in way I tried that years ago and it didn't do anything. Even pointed out that there arn't the same number of groves on each chamber. The only positive that came out of it was that it could create a higher detonation threshold by having "More surface area" in the chamber but that's assuming none of the edges get hot and your running a really high compression ratio.

Curl wrote:

Engine builders commonly talk of porting, polishing and reconfiguring cylinder heads and combustion chambers. All of these efforts have supposed advantages of improving flow and flame propagation. Metric Mechanic seems to go one step further by modifying combustion chambers with grooves or ridges.

Not sure, but



I have heard some WWII aircraft engines may have had a similar setup.

Singh's grooves in the squish area are very different from the MM ridges in the chamber wall area. The only way to tell if this works is back - to-back dyno testing, which MM no doubt did do. As with many similar modifications, it may work by masking another problem which might well be fixable with "normal" means - just not as easily as wacking in some grooves!

Brian
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1972 NTM Mk4 B sports racer, M10 engine

Bevan, you likely have far more experience than this self-confessed-tinkerer and you are more likely to take advantage of combustion chamber innovations than I.

Although you seem dismissive, you appear to have read and at least tried to understand the significance of Singh's supposed development. Someone in the patent office was obviously impressed enough to provide a patent for Singh's "groove science." One of the articles suggests any ol' tinkerer can benefit from trying this "idea." Can you think of a reason why this process/procedure can work, rather than merely mask some other internal combustion issue?

Maybe Miller and Offenhauser considered and rejected this notion in the 1920's. Multiple valves per cylinder were used back then and only became commonplace decades later. Then again, there are those that currently think the ford flathead V-8's are the wave of the future.

Thanks for your well considered thoughts.

From what I can see, it looks like the impressions were made with a punch rather than a grinder. There also seems to be some minor shaping of the area near the valve guide. The head seems too clean to have been placed in service with these modifications.

Can you provide any more information regarding these modifications? Who took the picture, are there more, who performed the modifications, etc.?

I would like to see a picture of the head after it has been in service for a while.

Much like the skin of a modern golf ball, the dimples are believed to be better for gas flow. But that also involves a rotating ball and forces that may be different than those encountered in an internal combustion engine. I also wonder about all of the "sharp" edges created by the cratering and how they might create hot spots, incandesce and be counterproductive except in maybe diesels.

More info please!

Thank you.

Randall_L. wrote:

From what I can see, it looks like the impressions were made with a punch rather than a grinder. There also seems to be some minor shaping of the area near the valve guide. The head seems too clean to have been placed in service with these modifications. Can you provide any more information regarding these modifications? Who took the picture, are there more, who performed the modifications, etc.? I would like to see a picture of the head after it has been in service for a while. Much like the skin of a modern golf ball, the dimples are believed to be better for gas flow. But that also involves a rotating ball and forces that may be different than those encountered in an internal combustion engine. I also wonder about all of the "sharp" edges created by the cratering and how they might create hot spots, incandesce and be counterproductive except in maybe diesels. More info please! Thank you.

Its my head :)

That head has been cleaned and media blasted. It was in service in a friend's 2002.

The head originally was worked over by DC engineering, however I dont think they did the dimpling.

I now have another E21 2.0 head, and once removed, I am going to compare the two and see if the combustion chambers are any different.

Personally, from what I understand, swirl is best done in the intake tract going towards the valve, you want to keep high gas velocities going into the combustion chamber etc...

my msn is cogline41 at hotmail dot com if you want to chat further :)

Pics

Julian wrote:

Somender Singh says a radical design change to the face of combustion chambers by forming grooves, channels or passages through the squish areas will further enhance in-cylinder turbulence followed by multi flame front combustion. Do-it-yourselfers might consider cutting some grooves in their chambers to approach the effect.

Its an interesting theory. Alot of engine design books i've read etc seem to strive for intake gas velocity, so you'll see them doing things like shaping the shroud area around the valve and shaping the floor of the intake manifold just before the junction to the head to create a bit more gas velocity.

I dont know if i'm going to use this head, it is setup for bigger valves etc, but I am going to be building a turbo engine.. so I dont know if the dimples would help or hurt. It needs to be surfaced and I was going to polish up the combustion chambers as well, get them all smooth again.

Other than lowering the CR and inhibiting the exhausting of gases from combustion chamber by the dead space in the pockets, I see no advantage unless somebody got his smiles doing an exercise in seeing how deep do go in making the blind holes without piercing through to the water jacket and weakening the head causing thermal expansion stress risers to induce cracking.
There are sure a lot of wet dreams on this board lately. Like there is a belief that is how equipment is seat of the pants engineered and produced for a reliable product.

jimk wrote:

Other than lowering the CR and inhibiting the exhausting of gases from combustion chamber by the dead space in the pockets, I see no advantage unless somebody got his smiles doing an exercise in seeing how deep do go in making the blind holes without piercing through to the water jacket and weakening the head causing thermal expansion stress risers to induce cracking. There are sure a lot of wet dreams on this board lately. Like there is a belief that is how equipment is seat of the pants engineered and produced for a reliable product.

An old german guy I know saw that head and commented that messerschmidt had a similar thing at one point in a WWII plane engine, he had seen it anyway. A few other old old school aircraft guys have also seen it.

I tend to agree with you that, most likely this mod isn't going to do much, but there's only one way to find out, side by side dyno testing with otherwise identical engines. Like that is going to happen. This head was run and was working on a pretty pimped out 2002, high compression engine etc, and the owner never ran into troubles with the head apparently.

it's mainly an oddity in my eyes. I think if this technology was really solid we'd see it on F1 engines.

Also, I dont hold the belief that any of our stuff is "seat of the pants engineered" however I do realise that car manufacturers have to balance mass production as well as producing a reliable engine. Maybe this mod works wonders but as you said weakens the head and eventually it'll crack! who knows. Great part about this Faq forum is we can throw stuff like this out there and see what everyone thinks

Some science is the result of necessity and some due to serendipity. While the odds favor Nobel prize winners and those schooled in the subject, that is not always the case. Smokey Yunick proved that "seat-of-the-pants" science is not always a junk.

I do not know much about combustion chamber design or laminar flow. Nor do I have any experience with German WWII piston driven aircraft other than having seen them. I do recall having seen some dimpled chambers in outboard motor cylinder heads at a machine shop. The "dimples" were very small and angular - not hemispherical. The dimples resembled "knurling" marks. Other than having seen them, I have no information about them.

Evidently, the concept of "golfing combustion chambers" is neither new nor particularly novel:

http://en.wikipedia.org/wiki/Cylinder_head_porting


"It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Often the size of the port is reduced to increase power. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the 1. boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow but an optical finish is wasted effort and money.
The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this."