Here is the story of putting Somender Singh's grooves in a 3 cylinder Geo Metro engine. This is a head package from 3tech, optimized for fuel economy, with 11:1 compression ratio. (After road testing this, I recommend 10.5:1 C/R unless you want to use better fuel than the cheapest low octane fuel).
FYI, the spark plugs I'm using are Halo, the ones they specify for the Geo Metro. These plugs ping less than normal plugs in my application, as well as giving more power.
The general feel of the engine with 3 grooves per cylinder is that there is very useable torque from 1500 rpm to 6500 rpm or more. Keep in mind that I have a racing header on this engine. The engine will idle smoothly to below 500 rpm, but is limited to 650 rpm by the ECM. I can idle it while driving in 2nd gear below 500 rpm without it complaining too much. There is a fantastic throttle response now. If you are driving in 1st gear at 1200 rpm and hit the throttle, the car moves rather quickly compared to before.
My grooves are rather "unrefined" according to the experts. They should be smoother, and sharp edges should be slightly rounded off.
First, to mark the location of the grooves.
Now, here the grooves are cut;
And a close-up shot;
Installation follows.. stay tuned.
The head is now installed. The compression is a bit high for running 87 octane fuel, but still driveable. I installed temporary water injection, to clean the carbon out of the engine. I didn't clean off the pistons when installing this head.
I've never seen a 3 cylinder engine run so smooth as this one with the grooves. You can idle in 2nd gear at less than 500 RPM and the engine doesn't complain! And driving around town in 5th gear is way easier than before! The grooves made my car noticeably quieter, too.
Time will tell whether fuel economy is improved
On the advice of automotivebreath, I decided to modify and add more grooves in an attempt to eliminate the pinging problem. Here's what the head looked like after about 1000 miles of driving with my original grooves;
The grooves were starting to fill with carbon and the burn was obviously not as clean as advertised with the grooves. So, out comes the dremel tool again...
3 grooves per cylinder now, and they are much more blended in with the cylinder head near the valves. They are bigger, too.
I put it all back together and drove it... This 3 cylinder Metro now brings to mind the experience of driving a Swift GTi... the 3 groove setup made a serious contribution to torque! The pinging is almost gone now, with comparable pinging to an unmodified Metro, only I'm running nearly 11:1 C/R and using the cheap 87 octane fuel! The performance gain is very nice!
I test drove this some more and while it runs nicely the C/R is still a little high for cheap fuel. To be on the safe side I recommend only 10.5:1 C/R.
I'll update fuel economy when I get some more miles on this thing. So far, it appears to want to get over 50 mpg in normal interstate driving, now.