Gears & Compression Ratio
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Instructor
Joined: Jul 2007
Posts: 236
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From: Mobile Alabama
Gears & Compression Ratio
I have a 90 L98 Automatic with the G92 Performance Axle Ratio which in 1990 was a 2.73 "I Believe" and all I have read leads me to "believe" that the 1990 L98 had a compression ratio of 9.5 - well I would like to go to a 3.73 in the gear and "if" the compression ratio is 9.5 what octane gas would I need to run - the owners manual say's 91 but all we have here is 89 or 93. Now I'm running 93 but the gas prices have even got my attention - now I still drive as much and as fast as I can but the prices have got my attention just not enough of it to stop me from driving but if I could get away with a lower octane well why not save a few bucks for ice cream. I think the 3.73's would really improve the quickness of the car and I'm not much of one to drive over 80 at the max on the interstate's. What are your opinions. On the compression ratio's I have the Helms guide and the Corvette Specs books and still seem to be getting different info on compression ratio.
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
If your worried about the difference in price between 93 and regular, then a gear change is not for you.
However, if you do the gear change, I would recommend something a little higher than 3.73, maybe more along the lines of 3.54. I've heard that the 3.73s can be a bit too much gear for a tpi car with a 700r4 tranny.
And you should be able to run regular through your car, if not, 89 should work fine.
However, if you do the gear change, I would recommend something a little higher than 3.73, maybe more along the lines of 3.54. I've heard that the 3.73s can be a bit too much gear for a tpi car with a 700r4 tranny.
And you should be able to run regular through your car, if not, 89 should work fine.
