Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Zetec Final Drive

Originally posted by DemonSVT:

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The 3.84 FD will degrade acceleration in every gear.

They will not change your trap speed. However that still means it takes longer to get to the same mph. (see #1)

They will not effect true power to the wheels. They can/normally falsely improve dynojet numbers because of the way a dynojet calculates power.

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Originally posted by MapOfTaziFoShoââ??¢:

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But, if you are making more power than b4 (3.0L) and you found yourself shifting into 4th gear at the end of the 1/4 then you are getting some benefit. Also when racing from a roll...the diff laucnh characteristics and the ability to hit 60mph in 2nd should be of some benefit.

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You are confusing benchmarking terminology with actual real world performance.

You state that the 0-60mph may be quicker because the car can reach 60mph in 2nd with the 3.84 and stock redline (6900rpm SVT)
{insert formula} 6900rpm with 3.84 & 24.5" tire = ~61mph

However you are failing to note that acceleration in 1st and 2nd gear will be slower because the gearing is weaker. That 3 tenths of a second you save from not having to make to 2-3 shift, during that small bench marking window, is basically going to wash with the slower acceleration of the first two gears.

Also if you use 10mph increments you will note that the 4.06 gears accelerate stronger to each respective 10mph mark when you factor in the shifting. Remember even if your 0-60mph is the same with the 3.84 gears your 0-50 is slower and 0-70 is much slower. (the 2-3 shift with 3.84's is between 60 & 70mph The 4.06's will just continue to walk its ass!)

You CAN NOT think about benchmarking times meaning a whole lot just by themselves. The placement of a shift point can significant skew those types of tests.

Racing from a roll. You still have 5% less TMF in every single gear. That means slower acceleration in each gear.

The only way a taller gear helps is if you have obscene amounts of power over a very broad powerband and can over power (literally) the losses caused by the weaker gearing. (there are formulas but I'm not typing them out) Turbo 3L's may fit that description but 300-400 wheels is really not "obscene" in my book. They do fit the very broad powerband and lower rpm powerband criteria though.


Also to add, the shift from 3rd to 4th at the end of the track is not relevant. The 3-4 shift duration does not cause any significant loss of acceleration ability in such low power applications.

Also any car trapping over about 95mph needs to shift to 4th regardless. That makes that a moot point for any car much above SVT levels.

Originally posted by MapOfTaziFoShoââ??¢:

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But, if you are making more power than b4 (3.0L) and you found yourself shifting into 4th gear at the end of the 1/4 then you are getting some benefit.

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If you do not shift into 4th in the 1/4 with a V6 in these cars then you have a very slow car! lol...Hell, I almost shift into 4th in the 1/8 mile with my Cougar and a 75 shot. If I had some traction in the first two gears I prolly would have to shift into 4th, but my cheap arse not buying some drag radials...that's a different story.

Originally posted by DemonSVT:

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The only way a taller gear helps is if you have obscene amounts of power over a very broad powerband and can over power (literally) the losses caused by the weaker gearing. (there are formulas but I'm not typing them out) Turbo 3L's may fit that description but 300-400 wheels is really not "obscene" in my book. They do fit the very broad powerband and lower rpm powerband criteria though.

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