project: dogbox transmission for st205 Options

[tufy]

Ater i had several transmisson proplems. i realized that i need a stronger one. i decided to build a custom gearbox. so i can decide for ratios. what would you chose if you build one?
here is some ratios

......................Standart...................fensport.............custom
1 st gear......3.38 - 57 Km/h.............3.58....................?
2 nd gear.....1.91 - 100 Km/h...........2.045..................?
3 rd gear.....1.26 - 150 Km/h............1.33...................?
4 th gear.....0.92 - 210 Km/h............0.97...................?
5 th gear.....0.73 - 239 Km/h............0.73...................?

Final drive 4.285............................3.933...................?

can any one tell me what is relationship between final drive and gear ratios.
if gear ratio x final drive ratio is equal, speed is same.

those are thinks that i am planning to have.
*seq. Shifter

*new input and output shafts,
staright cut gears,
dog clutches,
hubs,
forks

*final drive (pinion and crown), front & rear


*front lsd
(not sure about front lsd, fensport is using stock one)

This post has been edited by tufy: Mar 8, 2007 - 6:34 AM

[95celgt]

Theoretically, the final drive changes the overall ratio to taller or shorter gearing, so by the looks of it the fensport has a bit higher top end, but i see the individual gears themselves are a bit shorter so it MIGHT cancel itself out, regardless the fensport might give you another 10-15 mph on 5 gear.

[Driveby]

Not much help here but the fensport box is good for 200mph in 5th with an 8krpm limit.

[playr158]

Theoretically, the final drive changes the overall ratio to taller or shorter gearing, so by the looks of it the fensport has a bit higher top end, but i see the individual gears themselves are a bit shorter so it MIGHT cancel itself out, regardless the fensport might give you another 10-15 mph on 5 gear.

5th gear has the same ratio as stock so it shouldn't perform any different ?

[Bitter]

Theoretically, the final drive changes the overall ratio to taller or shorter gearing, so by the looks of it the fensport has a bit higher top end, but i see the individual gears themselves are a bit shorter so it MIGHT cancel itself out, regardless the fensport might give you another 10-15 mph on 5 gear.

5th gear has the same ratio as stock so it shouldn't perform any different ?

but the final drive is different, calculate that into the math.

[jgreening]

Here is some basic information:

Understanding Gear Ratios

I suspect that the answer to your question depends on your desired application. If the answer is drag application, I strongly suspect that you will want to pick ratios that allow you to cross the finish line without shifting to fourth gear. This would require calculating what gear-set is necessary for your trap speed given the OD of your tires. Unfortunately, my knowledge of how to do that is lacking. Perhaps someone else can help in that regard.

[tufy]

Theoretically, the final drive changes the overall ratio to taller or shorter gearing, so by the looks of it the fensport has a bit higher top end, but i see the individual gears themselves are a bit shorter so it MIGHT cancel itself out, regardless the fensport might give you another 10-15 mph on 5 gear.

5th gear has the same ratio as stock so it shouldn't perform any different ?

but the final drive is different, calculate that into the math.

i think final drive drive is pinion and crown right?
st205 should have 2 set. one in transfer box, one in rear lsd.. and they should be same ratio..

[Bitter]

yes, you want the front and rear final drives to be the same, i was saying that if your new box has a different final drive then you need to include that in the comparison of what your speeds in different gears will be.
http://www.5speedtransmissions.com/gear_calculator.html
http://www.f-body.org/gears/

the final drive also has an influence on wheel torque readings, the higher the FD the shorter your gears and the higher the torque multiplication. however for a boosted car longer gearing can be better since you'll stay in the boost longer and in your powerband longer than if you're shifting more often.



tufy, i know you know what you're doing. i'm just explaining this to the others who may ask or not know.

[Wolf_tm]

tufy,

what kind of problems did you have with your transmission ?

I know of people using successfully the E154 box with much more torque...

Bye...

[tufy]

tufy,

what kind of problems did you have with your transmission ?

I know of people using successfully the E154 box with much more torque...

Bye...

i broke gearbox shaft, rear difrential, then transferbox.
now have cusco lsd..
what is nubers of much more torgue?

[Wolf_tm]

1000 nm torque of tte Wrc engines...

This post has been edited by Wolf_tm: Mar 27, 2007 - 7:51 AM

[Wolf_tm]

tufy, do you use your car for track/fast road or drag races?
What kind of clutch do you have in?

[tufy]

tufy, do you use your car for track/fast road or drag races?
What kind of clutch do you have in?

i have cusco twinplate cerametalic clutch kit.
i use my car everyday fast road and weekend drag racing, with 570nm @ 1 bar. dont know about 1.5 bar that i use for races.

[Wolf_tm]

Ok tufy, let me explain...
I have 2 friends with a 3sgte engine on an st202 with the st202 fwd box.
One guy user via car in tracks, and he never had a problem... the other one for drag racing, and he already broke the box 2 times...
I think the problem is in the hard engagement in first gear.
It is just an idea of mine, but, is your twin clutch dampened?

[Wolf_tm]

i use my car everyday fast road and weekend drag racing, with 570nm @ 1 bar. dont know about 1.5 bar that i use for races.

tufy,
just for my curiosity,
but how is it possible you don't know power/torque at 1.5 bar ?

If you mapped it at that boost... and it is NECESSARY to do that if you don't want an explosion of your engine , you should even know those numbers !

[tufy]

i use my car everyday fast road and weekend drag racing, with 570nm @ 1 bar. dont know about 1.5 bar that i use for races.

tufy,
just for my curiosity,
but how is it possible you don't know power/torque at 1.5 bar ?

If you mapped it at that boost... and it is NECESSARY to do that if you don't want an explosion of your engine , you should even know those numbers !

man.... we left dyno with a bow proplem last year. after fix that proplem car was tuned on the road. we are planning to go dyno and finish mapping in a short time.
i know the limits of 3sgte engine..
do you think 1.5 bars is too much? i am planning to boost more after i have my top feed 1000cc injectors..

[Wolf_tm]

turbo pressure is only ONE of the values that participates in building power and torque, so turbo pressure it is not SO important.
For example, now i run 2.05 bars, and 1000cc. injectors ( and i still have to dyno it in this new setup, only road mapping ), but given that i hate drag races, but i love mountain winding roads, i personally built an engine with driveability and quick spool up in mind, at the expenses of max power.
I know the 3sgte limits too.
Good luck with the gbox!

This post has been edited by Wolf_tm: Mar 12, 2007 - 8:26 AM

[tufy]

thanks wolf.
but my question was not ''why i had transmisson proplems?''
i want some ideas about ratios...

[tufy]

here is what i am thinking to order.. as my car has good power starting from 5000 rpm till 8000rpm (best are 5800rpm-7500rpm) i decided that. longer 1st gear, 2nd gear remains same, slightly shorter 3rd and 4th gears. and longer 5th gear for top speed...


This post has been edited by tufy: Mar 27, 2007 - 11:39 AM