Recently, I've been fixated with grooved heads. Here's a good starter link:

http://www.somender-singh.com/

They say that putting a groove in the cylinder head's squish area greatly improves combustion chamber turbulence. Apparently torque is improved over the whole curve. Higher compression can be used.

His work is backed by a U.S. patent.

On the above site are several people who are putting the grroves in SBC engines. There's even a couple of LS1 owners using the grooves as well as a guy with a set of AFRs with custom grooves.

Does anyone have any experience with this?

 

Looks interisting. I would "think" it would cause hot spots? Some one (like a shop) should do a dyno before and after with some old heads lying around.

 

Does sound neat, and I could see how it would stir up the mix. But one thing I found odd on the site was the statement:

Looks like running the quench closer would enhance the groove effect?

 

I believe Absolute Speed used to do something simular with thier heads.

 

Here's another link from fueleconomytips.com which talks more about the theory of how it works.

http://www.fueleconomytips.com/index...id=73&Itemid=2

And here's a thread on their site that I am following waiting for dyno results. The site is dedicated to fuel economy, so you have to weed through the thread to find good nuggets about torque and performance.

http://www.mpgresearch.com/viewtopic...hlight=grooves

greg

 

Fascinating stuff.
I didn't take the time to wade through everything.......

Have they done a baseline test on the verge of detonation, and then upped the compression using the same gas and not had detonation with the gooving?

Have they seen how much they can increase boost with no other changes except the grooving?

_____________________
2000 FRC, ECS Paxton

 

I am waiting for the Chevy guy to post more results too. Apparently it has become so commonplace that they recommend grooving the heads while you have the heads off for a refresh.

I am hoping the guy from AFR chimes in (Tony, I think is his name) since one of the posters did the grooving on AFR 205s.

What got my attention was two things:
- Compression could be bumped up considerably without detonation.
- They are doing it on high performance engines. After grooving the heads, his .700 inch lift cam idled at 600rpms.

 

ttt, looking for more feedback

 

I would think these grooves would be a source of stress risers. I might be willing to try it on a CRX engine I'm rebuilding...

 

Now I've got to jog my memory here, but about 25 or so years ago I built a B/Dragster and used what were then state of the art heads from Brandywine. I've no clue if they are still in business but the intakes were left with a somewhat rough finish and the thinking was that it would create turbulance which enhanced combustion. Exhaust ports were smooth as a baby's butt to reduce any resistence for exhaust gases. Whether this goove accomplishes the same goal I've no clue. But it sounds very familier.

 

The difference here is that the turbulence is created in the combustion chamber, as opposed to the velocity created in the intake runner. The grooves do this *AFTER* the intake valve has closed.

Here's a quote from the article.
[begin quote]
The cylinder heads of most modern engines are divided into 2 segments: the “squish” area, and the “quench” area. The squish area squeezes the air fuel charge and forces it into the larger quench area on the compression stroke. Squish creates high velocity streams inside the cylinder to vaporize and homogenize the fuel in the air.

Looking at the picture above, there are 5 lines carved into the squish area of the cylinder head. There are 3 lines opposite the spark plug, and 2 lines adjacent to the spark plug. Notice that all 5 lines are aimed straight for the spark plug tip. As the spark plug fires and the flame front traverses outwardly, this pressure wave will travel down the grooves to form high-pressure jet streams. At this point, the cylinder head and piston are still cool enough that this jet stream isn’t dangerously hot.

Consider that the heavier elements in gasoline vaporize at 435 degrees F. at atmospheric pressure. Also consider that when the piston comes up on the compression stroke, this 435 turns into upwards of 1000 degrees F. under the extreme pressure. The liquid gasoline will go where there is the least activity in the cylinder…between the cylinder walls and the piston. The center groove shoots a jet stream down along the edge of the piston to blow this liquid fuel back out into the high velocity activity area of the combustion chamber where it can combust and produce power.

The other 4 grooves act to direct the swirl activity within the combustion chamber, as well as clean out the ring lands. They create a more intense, higher speed swirl which brings more of the fuel in contact with the flame front in a shorter period of time. This gives a more complete burn (read that lower exhaust emissions), less heat energy transfer to the cooling system, less carbon build-up on the piston rings and in the engine oil, more power, and better fuel economy.

In this picture there is only one groove. The cylinder head already incorporates high swirl design and the one groove is added primarily to clean out the ring lands of the liquid fuel. By visiting Somender’s web site you’ll find that the majority of the people incorporating his grooves are using just the single groove with impressive results.

The shape of the piston and cylinder head have their greatest affects on combustion efficiency when the piston is within about 10 mm of Top Dead Center (TDC). When the piston is more than 10 mm away from TDC, the cylinder head and pistons are just distant and innefectual walls bordering a large open expanse. So the grooves do their work within this 10 mm range. On the compression stroke, they force the compressing air/fuel charge into the quench area via higher velocity jet streams to better vaporize and homogenize the fuel. On the power stroke, they guide the explosion through these same jet streams but in reverse to create vorticies, to clean out the ring lands, and to some greater or lesser degree further excite the flame front.

Due to the rapid burn rate, higher compression ratios can be used without detonation problems. On turbo and supercharged engines, higher boosts can be run on the same octane fuel. In either case, lower octane fuel can be used than by conventional means
[end quote]