Piston ring thickness in boosted applications.

[plovett]

Does forced induction affect the choice of piston ring thickness? I am getting custom pistons made so I have some choices. Like 10 psi or so? I would guess not, but I thought it worth asking.

Thanks,

Paul

[PackardV8]

It has as much to do with the tune and the computer control thereof as it does with ring thichkness. Most of today's OEM high boost fours and V6s run thin rings.

[plovett]

Thanks for the reply. No computers on this build. Just a carburetor with a MSD-6BTM box to retard ignition timing with boost.

[PackardV8]

Thanks for the reply. No computers on this build. Just a carburetor with a MSD-6BTM box to retard ignition timing with boost.

With a conservative tune, conservative compression, the best forged pistons and the best rings, it might live.

However, BTDTNA. There's a reason OEM turbos/superchargers became more common as computers and sensors became more proficient. Today's engines produce horsepower we could only dream about with carburetors and distributors. The first OEM turbos couldn't run more than about 7.5 compression and very limited boost. Today, they're running 9 to 11-1 compression with three times the boost and making three times the horsepower, with a 50,000 mile warranty.

Mercedes-AMG has revealed its new turbocharged 2.0-liter inline-four, and it's the most powerful series-production four-cylinder in the world. It makes 416 horsepower and 369 lb-ft of torque in top trim, giving it a specific output of 208.9 horsepower per liter.

[mag2555]

I believe the first concern is how far down the top ring groove is from the piston top.

Then comes what the ring is made of and then if it’s barrel face ring or not.
The best way to cool the whole set up is to set the oil system up to squirt oil up into the bottom of the piston.

With some ingenuity you can set the system up with a solenoid to only come on at say 6 psi of boost.

[plovett]

Thanks for the reply. No computers on this build. Just a carburetor with a MSD-6BTM box to retard ignition timing with boost.

With a conservative tune, conservative compression, the best forged pistons and the best rings, it might live.

However, BTDTNA. There's a reason OEM turbos/superchargers became more common as computers and sensors became more proficient. Today's engines produce horsepower we could only dream about with carburetors and distributors. The first OEM turbos couldn't run more than about 7.5 compression and very limited boost. Today, they're running 9 to 11-1 compression with three times the boost and making three times the horsepower, with a 50,000 mile warranty.

Mercedes-AMG has revealed its new turbocharged 2.0-liter inline-four, and it's the most powerful series-production four-cylinder in the world. It makes 416 horsepower and 369 lb-ft of torque in top trim, giving it a specific output of 208.9 horsepower per liter.

Yup, conservative build. Low compression, low boost, relatively low specific output. What about the rings, though?

[plovett]

I believe the first concern is how far down the top ring groove is from the piston top.

Then comes what the ring is made of and then if it’s barrel face ring or not.
The best way to cool the whole set up is to set the oil system up to squirt oil up into the bottom of the piston.

With some ingenuity you can set the system up with a solenoid to only come on at say 6 psi of boost.

Thanks. I'll have somewhat tall pistons so plenty of space to move the top ring down. I wasn't thinking about squirting oil on the piston, but that's a thought.

Can you elaborate on what ring material is desirable and the barrel face shape?