LOOK HERE: Your tranny, the 1/4 Mile, and YOU

[blueovalbaboon]

Gearing FAQ

ATX RATIOS:

1st: 2.82
2nd: 1.50
3rd: 1.00
4th: 0.73

Final:
3.68 (Duratec, SPI?)
3.91 (Zetec)
4.15 (SPI? Contour)

(a junkyard, Performance Automatic, or Lentech should easily be able to supply you with the desired final drive ratio)

What this means on the strip:

The most important part of understanding how a car's transmission affects quarter mile times is to understand what RPM range is being used in each gear.

First, we'll calculate the RPM drop after each shift. This is simply the ratio of the gear you are changing to divided by the ratio of the gear you were in:


1/2 shift: 1.5/2.82=.52 This means that 2nd gear RPM will be at 52% of what the 1st gear RPM was at shift.

2/3 shift: 1.0/1.5=.66 3rd gear RPM will be 66% of what 2nd gear RPM was at shift

3/4 shift: .73/1.0=.73 4th gear RPM will be 73% of what 3rd gear RPM was at shift.

As always, the bigger the diff gear, the more torque your car has, and the faster you'll be in the quarter mile.



MTX-75 GEAR RATIOS:

1st: 3.67
2nd: 2.14
3rd: 1.45
4th: 1.03
5th: .77

Differential Gears:
3.42 (duratec)
3.82 (zetec)
4.10/4.11 (contour and FR)

What this means on the strip:
1/2 shift: 2.14/3.67= .60 60% of original RPM
2/3 shift: 1.45/2.14= .66 66% of pre-shift RPM
3/4 shift: 1.03/1.45= .71 71% of pre-shift RPM
4/5 shift: 0.77/1.03= .75 75% of pre-shift RPM


MT-285 GEAR RATIOS:
(because of the weirdness of the Getrag, we'll be using the combined ratios of the gears)

1st: 12.789
2nd: 7.793
3rd: 5.651
4th: 4.615
5th: 3.828
6th: 3.126

1/2 shift: .62
2/3 shift: .74
3/4 shift: .83
4/5 shift: .82
5/6 shift: .78

The final and most important installation will be how to use a dyno graph to determine the best shift points for your car based on the above data. This is particularly vital in an ATX car where your shift points can only be changed through reprogramming the ECU, either by chip or flashing. I will also cover selecting an aftermarket Torque Convertor for the ATX crowd.

I NEED YOUR HELP HERE: PLEASE POST 1 stock dyno of a zetec, a duratec, and an SVT each. PLEASE POST a full bolt on (no cam) Zetec and a full bolt on Duratec. PLEASE POST 1 dyno of a Zetec with either NEW GRIND crower 2s (NOT old), Cat 1s, or FR 2's. Thanks. It doesn't take me long to do these writeups, but I'd ratehr not search like mad for the dynos...

If you want to learn this stuff, I need your help

[JeffG]

can i open up any the gears on an ATX? what would a junkyard have? does a lentech help?
this is my first attempt at "modding" a car. i am just trying to understand everything.

[ladybug04]

what about the spi's ib5 gearing?

[NewtzZx3]

well i don't see any dyno pics here so i'll link mine up, i don't think it quite meets your criteria, but better than nothing eh?



this one is with all mods in my sig except the fs sct chip, rims, and fc 65 mm tb (it was with a ported stock one instead)

[blueovalbaboon]

alright i'll get to work on it

[Z63R]

With all due respect, Sir, I will add that according to Ford's Media Website, my '03 2.3 PZEV Automatic transaxle is equipped with a 3.73:1 ratio.


Which I should really verify from a second source.

Perhaps The Lenster would tell us.

[blueovalbaboon]

First thing. Chris, 3.73=3.68 for all I care, so shove it.

On a lighter note, it's time to talk about calculus and physics. YAY!!!

First the physics. There's a lot of debate about when to shift. There's the ricer method of shift as high in the rev range as you possibly can because it sounds cooler. Screw that. It comes down to which is more important in the quarter mile: torque or horsepower. There are two equations we're going to pay particular attention to.

1. Horsepower = Torque (ft/lbs) * RPM/5250
2. Horsepower = Force(lbs) * Velocity (mph)/374

We've all heard number 1 said thousands of times, but number 2 is new. Now lets play around with it a bit:

Force = Horsepower/Velocity

So, at any given velocity, the higher your HORSEPOWER is, the higher your FORCE (and thus acceleration) is. It turns out what we want to maximize at the strip is the amount of horsepower being delivered to the wheels. THis is why we'll pay attention to the horsepower part of the graph when picking our shift points.

Now, for the calculus. Don't worry, no equations here, just concepts. Ideally, maximizing horsepower would mean we just leave the engine at the peak HP rpm and sit back as we get perfect quarter mile times. Problem here: none of use have CVT's. WE can't keep our horsepower level constant because our RPMs aren't constant.

Since we can't leave it at peak HP point, we'll just have to do second best and maximize the area under the curve. THis means we won't actually be shifting AT the peak torque point, OR the peak HP point, but somewhere PAST it. I'll show you why graphically.

[Z63R]

First thing. Chris, 3.73=3.68 for all I care, so shove it.

You know I like to split hairs. WTF???

[sleeperlove]

so anything new in this thread like when good shift points are. the graphs that were spoken of ?

[svt_gEEk]

I dont have any graphs, but the idea is to shift at a point in your hp curve where after the rmp drop-off you will be close to the same horsepower value on the curve post-shift as you were pre-shift. The point is to not let the horsepower drop down,late in the rpms, below where you will be after you shift. I know that is probably confusing and I didn't word it right. If further illustration is needed let me know and I will try my best to do so.

[blueovalbaboon]

that's a great summary geek

i meant to put the graphs in ages ago, but i lost all ambition.

[FOKUZ03]

nah keep on going this is intersting blueoval

[H2Oboy]

First SPI rockers, now this.....You drop more balls than a one-armed prostitute.

[FocusRyderZx3]

yo folks if you have a auto tranny, there really aint nothing you can do, only a torqe converter and one other thing, best thing, either get another focus with the mtx or swap. i had an auto and got a mtx and it was the best thing i have ever done you can actualy feel the power of the car while going through the gears

[DerrelHGreen]

MTX-75 GEAR RATIOS:

1st: 3.67
2nd: 2.14
3rd: 1.45
4th: 1.03
5th: .77

Differential Gears:
3.42 (duratec)

3.82 (zetec)

I have an MTX-75 and a Zetec, so my Kona has the 3.82 gears, correct?

Now let's say I wanted to gear it higher (lower numerical gears for less revs per mile)
will the Duretec MTX-75 transmission interchange with my Zetec MTX-75 transmission,
or must I install the higher ring and pinion ratio gears (3.42s) into my original MTX-75 case?

[blueovalbaboon]

the cases are different, the internals are compatible however. So I guess if your thing is landspeed racing or super good fuel economy, yeah you can snag the duratec ring and pinion and use it.

[DerrelHGreen]

That indeed was my thing.
Not just for the increased fuel economy, but also for the more relaxed and quieter cruising ability.

First gear would then become much more useable, unlike it is now.
Unless it's an uphill start, I generally take off from rest in second speed unless I'm
in a big hurry, and then I just get it moving enough to fetch second right away.

I had hoped that if the transmissions were indeed interchangeable, I might find someone that would want
my lower gears, and we could swap. My trans is almost brand new, with the car having less than 8K miles.

[blueovalbaboon]

PM KogboxKing on the site. He's a sponsor and could tell you hwo much it'd cost to professionally swap the gears.

[jroczx3]

what does it cost to go from a sock auto ztech (01) to either a 5 speed or a 6 svt ? im just curious if this is a dumb question i dont want to start a fight with anyone im just asking so if you feel the need to make fun of me then dont reply...there is no point to make fun of people here we are all driving the same thing with some differences

[LornesBored]

Originally Posted by svt_gEEk

I dont have any graphs, but the idea is to shift at a point in your hp curve where after the rmp drop-off you will be close to the same horsepower value on the curve post-shift as you were pre-shift. The point is to not let the horsepower drop down,late in the rpms, below where you will be after you shift. I know that is probably confusing and I didn't word it right. If further illustration is needed let me know and I will try my best to do so.

I somewhat understand, but why not illustrate it anyways?

[w00w00]

european mtx75 gear ratios came up in a discussion on another forum. these were submitted but not verified:

1st gear : 3.417
2nd gear : 2.136
3rd gear : 1.483
4th gear : 1.114
5th gear : 0.854

final drive ratio : 4.066

[Fahad_H]

Originally Posted by w00w00

european mtx75 gear ratios came up in a discussion on another forum. these were submitted but not verified:

1st gear : 3.417
2nd gear : 2.136
3rd gear : 1.483
4th gear : 1.114
5th gear : 0.854

final drive ratio : 4.066

I own a European Focus, is there a way to verify the gear ratios ?



Thanks,
Fahad

[Jaydaddy]

What is "flashing" the ECU?

[Fahad_H]

Originally Posted by Jaydaddy

What is "flashing" the ECU?

a tune by a device such as SCT XCalibrator 2

[Ciraeon]

It's a sticky, but rather dead, so perhaps this might bring it back from the dead.

There was a bit of talk of calculus, but it didn't seem like anyone threw any numbers at the wall. So, I pulled out my calculator, and did.

For the 2.0L Duratec on the -75 tranny, at a stock tuning point, going by Focussport's Dyno graph used in their comparison of the stage 1 turbo as a reference chart, this engine is of the 'push it to the redline' variety. Area under the curve keeps increasing right past the possible rev range. So, for anyone at least with a stock tuning on this one, 'theoretically', with a perfect 0.0s shift, best shift point's just before it hits the limiter.

Anyone interested in the math, and the assumptions, used, it's only a PM away.