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The Terminator
Driveline
Soo happy!! 3.90's are on!
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<blockquote data-quote="Bob Cosby" data-source="post: 1749925" data-attributes="member: 2506"><p>JT...the majority of the facts you present are accurate and indisputable. Also, I agree that if a car is traction-limited, lower gearing can have a detrimental affect.</p><p></p><p>However, with traction (IRS or not), a car that is geared to take advantage of its powerband (ie...optimally-geared) will out ET (meaning out accelerate in the 1/4 mile) a car with less-than-optimal gearing. 3.55s and 3.73s are less than optimal for the majority of 03 Cobras - even with a redline limited to 6500 rpm. </p><p></p><p>"Optimal gearing" for the 1/4 mile typically means that you gear the car to run several hundred rpm above peak HP at the end of the run in 4th gear. A stock 03/04 Cobra makes peak power at ~6000 rpm, meaning you want to run the car pretty much to redline in 4th gear - or above that if your peak HP rises.</p><p></p><p>The idea is to maximize average HP in each gear. In 1st, 2nd, and 3rd gear, that means calculating optimum shift points, for which rear gearing has little or no effect. However, for 4th gear, it means gearing the car as described above. </p><p></p><p>Put another way, if you're going to use all 4 non-OD gears anyway (which we will all do with aftermarket gearing), you'll go quicker if you maximize torque multiplication (lower gears) in each gear. Torque is multiplied with gearing, so for best ET, gear the car so that it goes through the traps ~500 rpm above redline in 4th gear.</p><p></p><p>Again - this assumes traction. If you race on street tires or are otherwise traction-limited, then you may or may not go quicker with an optimum power gear.</p><p></p><p>Also, N/A DOHC Cobra's all came with 3.3x 1st gear ratios, not low 2.x. Most of us that actively raced these cars still used very aggressive gearing, for all the reasons mentioned above, and even more so to get the car moving smartly in 1st and 2nd gear, because you spend most of your time in that part of the track.</p><p></p><p>Bob</p></blockquote><p></p>
[QUOTE="Bob Cosby, post: 1749925, member: 2506"] JT...the majority of the facts you present are accurate and indisputable. Also, I agree that if a car is traction-limited, lower gearing can have a detrimental affect. However, with traction (IRS or not), a car that is geared to take advantage of its powerband (ie...optimally-geared) will out ET (meaning out accelerate in the 1/4 mile) a car with less-than-optimal gearing. 3.55s and 3.73s are less than optimal for the majority of 03 Cobras - even with a redline limited to 6500 rpm. "Optimal gearing" for the 1/4 mile typically means that you gear the car to run several hundred rpm above peak HP at the end of the run in 4th gear. A stock 03/04 Cobra makes peak power at ~6000 rpm, meaning you want to run the car pretty much to redline in 4th gear - or above that if your peak HP rises. The idea is to maximize average HP in each gear. In 1st, 2nd, and 3rd gear, that means calculating optimum shift points, for which rear gearing has little or no effect. However, for 4th gear, it means gearing the car as described above. Put another way, if you're going to use all 4 non-OD gears anyway (which we will all do with aftermarket gearing), you'll go quicker if you maximize torque multiplication (lower gears) in each gear. Torque is multiplied with gearing, so for best ET, gear the car so that it goes through the traps ~500 rpm above redline in 4th gear. Again - this assumes traction. If you race on street tires or are otherwise traction-limited, then you may or may not go quicker with an optimum power gear. Also, N/A DOHC Cobra's all came with 3.3x 1st gear ratios, not low 2.x. Most of us that actively raced these cars still used very aggressive gearing, for all the reasons mentioned above, and even more so to get the car moving smartly in 1st and 2nd gear, because you spend most of your time in that part of the track. Bob [/QUOTE]
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