Accelerate faster with O/D off??

T

tornatic!!

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#1

• Mar 28, 2006

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I have a stock '02 auto GT Conv. Why do I accelerate faster with O/D off?? It seems like with O/D off I accelerate much better than with it on. I know it takes away some top end because my rpm's are higher than normal with O/D off.

 

S

speedytang

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#2

• Mar 28, 2006

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The computer in the cars allows additional timing with the O/D button off. I have seen a PMS timing map for these cars and I have seen additional 8 degrees of timing with the O/D off.

 

the98stang

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#3

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speedytang said:

The computer in the cars allows additional timing with the O/D button off. I have seen a PMS timing map for these cars and I have seen additional 8 degrees of timing with the O/D off.

Click to expand...

That is nuckin futs!

 

S

speedytang

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#4

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Looking at some of my past data files it looks like the O/D button uses some of the same timing maps as the cars with traction control on without the ABS controlling the wheel spin.

 

Don 95Vert

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#5

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There are absolutely NO fuel or spark modifiers that depend on the OD button being on or off. It's just your imagination. It is a great idea to always have the OD off for WOT runs - you never want to go to OD under full power. Even on a stock car this is hard on the OD band. On a car making lots of torque, this would kill the tranny in short order.

 

U

Uncle Meat

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Mar 28, 2006

#6

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Hmmmm..... maybe because drive is a lower gear ratio than OD?

U.M.

 

T

tornatic!!

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speedytang said:

The computer in the cars allows additional timing with the O/D button off. I have seen a PMS timing map for these cars and I have seen additional 8 degrees of timing with the O/D off.

Click to expand...

Meaning??

 

merc123

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#8

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I've never noticed a difference in O/D being on or off. O/D is just that, OVER DRIVE. It doesn't kick in until when? When you let off the gas and cruise.

 

Brute03

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#9

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i don't think it should make a difference, as long as you have the throttle pinned the computer wouldn't allow the tranny to shift into O/D until you're near redline in third

 

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Stang2003GT

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#10

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speedytang said:

The computer in the cars allows additional timing with the O/D button off. I have seen a PMS timing map for these cars and I have seen additional 8 degrees of timing with the O/D off.

Click to expand...

Why would ford do that? Timing wont change fuel burn just when it happends. Why restrict timing when OD is on, its not like an old fashion overdrive unit which will turn ur 3 speed auto into a 6 speed auto. Still those things were beasts so I have no idea why anyone would want to do that.


The only reason I would turn it off is if ur driving like 110mph threw traffic and u want to let off for a sec and get on it again and u dont want to waste time shifting. Or in my 1990 corvette I drove around town in D because OD made my hold car shake. But who like to crusie around in OD at 50 mph doing 900 RPMs? Got to hand it to the 350 its got the torque for it, still got to be bad for the motor when it vibrates like that. I think it had gears under 3.

 

S

speedytang

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#11

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Don, What is causing the WOT timing difference on the '99 when the O/D is off. I have seen this myself no BS. Is it because of the converter not locking. Thanks

 

S

Stang2003GT

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#12

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Shouldnt it lockup after 1st? On a different note I know a chevy guy who always calls his transmission a 3 speed with a lock up that make it like a 4 speed. I always roll my eyes to that crap.

 

FivePointStang

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Mar 28, 2006

#13

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I seem to remember in my 94 AODE that when I had OD off it "seemed" to accelerate quicker. Although, Im sure the RPMs being higher before it shifted probably just made me feel like it was a tad quicker than when it was off.

Then again, it could have just been all in my head.

 

reddrgn01gt

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#14

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It accelerates quicker bc you are cruising at a higher rpm to start with. I almost never have the OD on.

 

Don 95Vert

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#15

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speedytang said:

Don, What is causing the WOT timing difference on the '99 when the O/D is off. I have seen this myself no BS. Is it because of the converter not locking. Thanks

Click to expand...

Probably changes in calculated load or RPM, or some other spark modifier but it really has nothing to do with the OD button being on or off. I can show you the spark modifiers and there a lot of them - but none have anything to do OD.

 

C

cooter_11

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#16

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Does it have anything to do with mainline pressure or firming shifts?

I'm probably looking too far into the question. You're at a higher RPM to start, therefore when you press the throttle you are more into you're powerband and are not lugging the engine. You'll feel a crisper throttle response when you cruise without O/D simply because you are in third gear and not fourth.

Also, third gear will give you more torque to the ground than 4th will, due to the lower gear ratio. The lower the gear you're in, the more torque you multiply. Say for instance third gear is a 1:1 ratio, and 4th (O/D) is like a .50:1 ratio. Now take your engine torque and multiply those number by it. We'll say 250 for easy math purposes. You get 250 in third, and 125 in 4th. That's not exactly how it works, but I hope that helps this make sense to ya tornatic.

 

K

Kilgore Trout

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#17

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So much in this thread...

 

03ghoststang

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#18

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all i know is that O/D is for when i want to retain some MPG LOL!! or highway cruisin otherwise i have it off and i dont shift into it going WOT cause

WOT + shifting into O/D = the death of O/D or tranny

 

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soctty7676

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#19

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Having driven plenty of Fords with the O/D button, the only thing it did was disable the O/D. This was useful when driving hilly curvy roads so the transmission didn't shift in and out of O/D.

 

I

isomatic

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#20

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• #20

If your OverDrive button is on your def. gonna see some decline in accel.