Gear Selection twin turbo big cubes
12-02-2008, 06:54 PM
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Gear Selection twin turbo big cubes Got a friend with 427 twin turbo trying to decide what gear to run in the rear end. Car will be used for drags quite often. Tranny is also M12 vette. Any insite would be nice. I am a blower guy dont know much about the spooling affects of a low or high gear in a turbo app esp with the m12 tranny. Thanks for any info you coul help with...
Car put down around 750 last dyno 3:42 gear
Car put down around 750 last dyno 3:42 gear
12-02-2008, 07:43 PM
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I was thinking he should stay with the 3:42 but to be honest the gearing of the m12 transmission kind of scares me going any bigger.
Maybe possible to gear rear for 3rd gear 1/4 traps? Maybe go something real low in the 2 somethings? Or is that a bigtime stretch?
Maybe possible to gear rear for 3rd gear 1/4 traps? Maybe go something real low in the 2 somethings? Or is that a bigtime stretch?
12-02-2008, 07:49 PM
#7
As most have said 3.25 to 3.50 is perfect. The lower the gear, the more load it puts on the motor and will help the turbo spool. To low, its hard to get the car going, but get a 2 step to launch and you should be good.
On a 28 inch tire, in 4th, which should be 1 with a 3.50 gear in the rear @ 6600 rpm you could trap around 157 according to the calculation.
Chris
On a 28 inch tire, in 4th, which should be 1 with a 3.50 gear in the rear @ 6600 rpm you could trap around 157 according to the calculation.
Chris
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12-02-2008, 07:55 PM
#9
3rd gear in the m12 is 1.43 so if you stuck with the 28 tire, and did a 2.90 in the rear you could hit about 133 in 3rd...
use the lpe 2 step, pull some timing, get 5-8 psi out of the hole, and the car should do very well.
Zombie has a th400, and has 2.xx gear and used 1-2 for drag, and 3rd like a overdrive. Didn't affect to much on the slip.
Chris
12-02-2008, 08:18 PM
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Thanks for all the help gonna recomend to him to stay with the 3:42 and hope for the best. I am sure he plays on the streets so the 2:90 gear I dont think is an option.
