Compression Ratio Question.......
Melting Slicks
Joined: Feb 2008
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From: Palm Beach
Let me see if I have this right.
1.They changed the pistons to raise the compression ratio.
2.Then dummied down the cam to offset the increased CR.
Two expensive offsetting changes that gained 5 HP.
1.They changed the pistons to raise the compression ratio.
2.Then dummied down the cam to offset the increased CR.
Two expensive offsetting changes that gained 5 HP.
Last edited by MK 82; Feb 22, 2008 at 10:05 AM.
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
Seems kinda stupid, huh? I betcha that extra 1.25 point of compression helps the mods a bit..
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I'll spell it out one more time for you.
They upped the CR by .75:1 for 1990. If they had done that on an 89, they wouldve gotten more than 250hp, but they decided they wanted it to stay where it was, and so made the cam smaller. This is likely because the LT1 was in testing, and they didnt know how much it would make on a production car, and wanted to make sure the LT1 made a fair bit more hp than the L98.
They then made small muffler changes to affect the other 5hp.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
If you'd read and think about WTF we all just posted in the last 2 pages...
I'll spell it out one more time for you.
They upped the CR by .75:1 for 1990. If they had done that on an 89, they wouldve gotten more than 250hp, but they decided they wanted it to stay where it was, and so made the cam smaller. This is likely because the LT1 was in testing, and they didnt know how much it would make on a production car, and wanted to make sure the LT1 made a fair bit more hp than the L98.
They then made small muffler changes to affect the other 5hp.
I'll spell it out one more time for you.
They upped the CR by .75:1 for 1990. If they had done that on an 89, they wouldve gotten more than 250hp, but they decided they wanted it to stay where it was, and so made the cam smaller. This is likely because the LT1 was in testing, and they didnt know how much it would make on a production car, and wanted to make sure the LT1 made a fair bit more hp than the L98.
They then made small muffler changes to affect the other 5hp.
Changes cost money. They essentially got nothing out of it.
I does, however, leave the door open to a cam change for a good gain. Only reason I can think of.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
If you'd read and think about WTF we all just posted in the last 2 pages...
I'll spell it out one more time for you.
They upped the CR by .75:1 for 1990. If they had done that on an 89, they wouldve gotten more than 250hp, but they decided they wanted it to stay where it was, and so made the cam smaller. This is likely because the LT1 was in testing, and they didnt know how much it would make on a production car, and wanted to make sure the LT1 made a fair bit more hp than the L98.
They then made small muffler changes to affect the other 5hp.
I'll spell it out one more time for you.
They upped the CR by .75:1 for 1990. If they had done that on an 89, they wouldve gotten more than 250hp, but they decided they wanted it to stay where it was, and so made the cam smaller. This is likely because the LT1 was in testing, and they didnt know how much it would make on a production car, and wanted to make sure the LT1 made a fair bit more hp than the L98.
They then made small muffler changes to affect the other 5hp.
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But why two counterproductive changes. Why not just leave it alone instead of all that for 5 HP. You say they wanted the HP to stay the same. Then why change anything.
Changes cost money. They essentially got nothing out of it.
I does, however, leave the door open to a cam change for a good gain. Only reason I can think of.
Changes cost money. They essentially got nothing out of it.
I does, however, leave the door open to a cam change for a good gain. Only reason I can think of.
Incremental changes always add up.
Thread Starter
Team Owner
Joined: Oct 2004
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
Melting Slicks
Joined: Feb 2008
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From: Palm Beach
Team Owner
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From: Athens AL
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Le Mans Master
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From: One day you're a Comet...the next day you're dust... Arkansas
octane in my 440 Dodge so 93 isn't so super.
Melting Slicks
Joined: Feb 2008
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From: Palm Beach
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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Melting Slicks
Joined: Feb 2008
Posts: 3,286
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From: Palm Beach
89 17/25
90 16/24
http://www.fueleconomy.gov/feg/calcu...lumn=1&id=5243
http://www.fueleconomy.gov/feg/calcu...lumn=1&id=6394
Last edited by MK 82; Feb 23, 2008 at 12:00 PM.
Team Owner
Joined: Sep 2001
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From: Athens AL
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Thats not what I see.
http://www.fueleconomy.gov/feg/noframes/5244.shtml
http://www.fueleconomy.gov/feg/noframes/6393.shtml
Anyway the point is moot since they didnt get an increase by that site.
http://www.fueleconomy.gov/feg/noframes/5244.shtml
http://www.fueleconomy.gov/feg/noframes/6393.shtml
Anyway the point is moot since they didnt get an increase by that site.
Last edited by vader86; Feb 23, 2008 at 09:11 PM.
