Frank Acampora
Supreme Mariner
- Joined
- Jan 19, 2007
- Messages
- 12,004
Re: 87 octane ??
Speaking in generalities, the Chevy big blocks and Chrysler Hemi when used in supercharged funny cars and dragsters would have a flat head or dished head piston for lower compression to compensate for the supercharger. Maybe somebody on the forum with a supercharged go-fast boat can tell us their base compression ratio.
Don't know the compression ratio on the supercharged Buick Riviera, but I'll bet its slightly lower that the normally aspirated 3.8 V6. Buick was always a leader in forward thinking. First V6, speed records with the V6, Supercharged pick-up truck-forget the name -Grand National or something. A real barn burner. They still sell for premium bucks. Back in the early '60s they made a production turbocharged small V8 in a Skylark with alcohol injection when the turbo kicked in. Had a plastic tank in front of the radiator that you needed to keep full
And by the way. including burn out, a dragster engine only turns about 800-900 REVOLUTIONS from start line to finish. Do the math. 10,000 RPM divided by 12 (5 second run is 1/12 of a minute)
And, so much fuel is injected, they run right on the edge of hydraulic lock. I didn't believe it until I saw a demonstration. When the fuel injectors open, they spray like a garden hose!
And the reason for lower octane ratings at higher altitudes is: Because the air is less dense, less is inducted into the cylinder, thus, the EFFECTIVE compression ratio is slightly lower and less octane rating is needed.
Speaking in generalities, the Chevy big blocks and Chrysler Hemi when used in supercharged funny cars and dragsters would have a flat head or dished head piston for lower compression to compensate for the supercharger. Maybe somebody on the forum with a supercharged go-fast boat can tell us their base compression ratio.
Don't know the compression ratio on the supercharged Buick Riviera, but I'll bet its slightly lower that the normally aspirated 3.8 V6. Buick was always a leader in forward thinking. First V6, speed records with the V6, Supercharged pick-up truck-forget the name -Grand National or something. A real barn burner. They still sell for premium bucks. Back in the early '60s they made a production turbocharged small V8 in a Skylark with alcohol injection when the turbo kicked in. Had a plastic tank in front of the radiator that you needed to keep full
And by the way. including burn out, a dragster engine only turns about 800-900 REVOLUTIONS from start line to finish. Do the math. 10,000 RPM divided by 12 (5 second run is 1/12 of a minute)
And, so much fuel is injected, they run right on the edge of hydraulic lock. I didn't believe it until I saw a demonstration. When the fuel injectors open, they spray like a garden hose!
And the reason for lower octane ratings at higher altitudes is: Because the air is less dense, less is inducted into the cylinder, thus, the EFFECTIVE compression ratio is slightly lower and less octane rating is needed.
