High Compression
Race Director
Joined: Jul 2004
Posts: 12,685
Likes: 329
From: Scottsdale Arizona
Originally Posted by Ganey
More c/r is good.
I suppose this chart needs some explanation. It shows the increase in power in % of a C/R increase. EXAMPLE: If the original CR is 9:1 on right of chart & it is increased (A line) to 12:1 (B line) on left of chart, then the increase in power is about 4.5%. If the power is increased from 9.5 to 10, the increase is about .08%. Careful on overdoing it.
I suppose this chart needs some explanation. It shows the increase in power in % of a C/R increase. EXAMPLE: If the original CR is 9:1 on right of chart & it is increased (A line) to 12:1 (B line) on left of chart, then the increase in power is about 4.5%. If the power is increased from 9.5 to 10, the increase is about .08%. Careful on overdoing it.
Do you mean 8% or 0.08% increase in HP? I assume 8%?
PS. Oops; I get it now. You were estimating between lines. My keyboard was faster than my brain.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Ganey,
I have seen the table you posted before and have always been a bit suspect. My L46 was a high compression version of my L82. Same cam, 2.02 heads, intake, QJet, etc; BUT, the L46 had much more than a ~15 horse power advantage. The 3/4 ton pickups (bought new) had a huge difference in pulling power with engines differing principally with compression.
I don't think my 12:1 cr L88 would only lose 15 to 20 horsepower if I were to drop to 10 or less. The difference going from 10:1 to 12:1 is 7.8%, not 2.8%, at least according to DD2000.
In terms of personality, the difference between low compression and a high compression motors is like the difference between someone on Prozac and someone alert and ready for action. The table seems way too conservative.
Chuck
I have seen the table you posted before and have always been a bit suspect. My L46 was a high compression version of my L82. Same cam, 2.02 heads, intake, QJet, etc; BUT, the L46 had much more than a ~15 horse power advantage. The 3/4 ton pickups (bought new) had a huge difference in pulling power with engines differing principally with compression.
I don't think my 12:1 cr L88 would only lose 15 to 20 horsepower if I were to drop to 10 or less. The difference going from 10:1 to 12:1 is 7.8%, not 2.8%, at least according to DD2000.
In terms of personality, the difference between low compression and a high compression motors is like the difference between someone on Prozac and someone alert and ready for action. The table seems way too conservative.
Chuck
Team Owner
Joined: Jul 2004
Posts: 40,338
Likes: 786
From: Redondo Beach, California
In the National Corvette Restorers Society (NCRS) monthly magazine, there's vendors of gasoline lead additives (tetraethyl lead I imagine). If I had a compression ratio problem, I'd give their stuff a go.
In Corvettefaq.com there's an article about how to boost your octane rating if you're using pump gas. It has "recipes" for adding tolulene or xylene to pump gas. Tolulene and Zylene are sold as solvents in paint and hardware stores (sometimes sold as tolulol or zylol.) This stuff is about $6.00 a gallon here. A couple of gallons will boost your compression rating about 4 points if I remember. You know those little small bottles of "Octane Booster" sold in auto stores for $5.00 or so? Actually all they contain is either tolulene or zylene but all you're gettings is a few ounces and they're basically worthless because there's just not enough. Tolulene and/or zylene are common aeromatic additives for gasoline. They've been used for many many years in gasoline.
I used to have a piece part built L88 with the piston domes shaved down 0.100 inches for a 11.5:1 ratio. I would buy aviation gas at a local airport. At first I filled up 5 gallon cans and took it home. When the guy got to know me, he would also pump it right in the car if I wanted! 5 gallons of av gas and the rest of the tank with pump gas would work with 11.5:1. I don't know what av gas sells for now, but it's probably affordable. I also bought racing gas for use at the drag strip, but that stuff was really expensive.
...and finally. I once called up a gasoline refinery. They were the first to tell me about tolulene and zylene. Also, they were willing to make me gasoline with any octane that I wanted. The minimum order was 10,000 gallons.
In Corvettefaq.com there's an article about how to boost your octane rating if you're using pump gas. It has "recipes" for adding tolulene or xylene to pump gas. Tolulene and Zylene are sold as solvents in paint and hardware stores (sometimes sold as tolulol or zylol.) This stuff is about $6.00 a gallon here. A couple of gallons will boost your compression rating about 4 points if I remember. You know those little small bottles of "Octane Booster" sold in auto stores for $5.00 or so? Actually all they contain is either tolulene or zylene but all you're gettings is a few ounces and they're basically worthless because there's just not enough. Tolulene and/or zylene are common aeromatic additives for gasoline. They've been used for many many years in gasoline.
I used to have a piece part built L88 with the piston domes shaved down 0.100 inches for a 11.5:1 ratio. I would buy aviation gas at a local airport. At first I filled up 5 gallon cans and took it home. When the guy got to know me, he would also pump it right in the car if I wanted! 5 gallons of av gas and the rest of the tank with pump gas would work with 11.5:1. I don't know what av gas sells for now, but it's probably affordable. I also bought racing gas for use at the drag strip, but that stuff was really expensive.
...and finally. I once called up a gasoline refinery. They were the first to tell me about tolulene and zylene. Also, they were willing to make me gasoline with any octane that I wanted. The minimum order was 10,000 gallons.
