4spd Has Given Up!

[FPV TRANNY]

  The_Bogan said:

car is going into elite on the 3rd of december to have the gearbox rebuilt!!!

gonna add a 2700rpm stall convertor and a few extra goodies!!!

will keep yas posted on how she goes!!!

If you run with a 3000rpm converter,you will find that it will flare another 2 or 300rpm more.with your current power,street MT,s,converter and some cool weather, you should see a 11.5 @120mph

[ant0n]

what do you expect its just a BTR, and een rebuilding it itll still die in the arse after 6 months of hard driving, they just suck..look at upgrading ( mayby source a secondhandy box for cheap )

[JP300]

My standard box lasted about three years, I was running up to about 305 rwkw, low 12s passes no problem. But as soon as the power was uped to 360 rwkw it did exactly the same thing.

I had mine rebuilt and setup through Tunehouse and it has lasted for about a year so far! It has survived three outings at the track and the car still manages about 10 - 11 l/100kms on the freeway.

A 3000rpm stall is as high as you want to go if you are going to drive it on the street. Any more than that it will drive you nuts!

Tip: The 3000 rpm launches are even more fun if you can get a matched turbo!

Edited 27/11/07 08:16 AM by JP300

[TOM1111]

what exactly does a stall converter do?????

how does it effect normal driving

[aiboart]

  TOM1111 said:

what exactly does a stall converter do?????

how does it effect normal driving

It is a fluid ‘gear box’ with continuous rations.

For example It can take road wheels from zero speed all the way to say 15kph whilst the engine speed stays exactly the same.

In the process the torque convertor is constantly adjusting the ration of the ‘gearing’ whilst the car is accelerating. It continuously converts the differnce between the speed of the engine and the speed of the road wheels into extra torque at the rear wheels.

It is elegant and it is why auto cars did not need as many gears as manual cars. The torque converter acts as a type of continuous overdrive-underdrive, smearing the gear rations all over the place. In fact with a big enough torque convertor and a small enough operating range of speed you do not need to use any hard gears at all – the torque convertor does all the ‘gearing’.

The problem with the system is that the fluid based system is not as inherently efficient as a hard gears – which is why modern autos lock the torque convertor above a certain speed. The most modern auto’s, such as the ZF lock the torque convertor at every opportunity in order to maximize efficiency. To maximize efficiency further, they also use torque convertors with lower stall speeds/range – and they have more hard gears.

Another way of imagining how the torque convertor works is that the torque convertor allows you to rev the engine (say in 4th) whilst the car stays at the same speed (and still in 4th).

Of course you can rev the engine in a manual by virtue of a downshoft and you appreciate that whilst your speed has not actually changed the amount of torque available at the rear wheels has, which is why (generally) a downshift generates higher acceleration <1>. So when you rev an auto and the engine speed flares, the torque convertor acts in the same manner as the hard gear downshift, it multiplyies the torque at the rear wheels but with an entirely different (fluid) mechanism. Also, the torque convertor is a continuous transmission, so it is as if you did hundreds of small essentially tiny and instant hard gear changes.

The stall speed is the maximum speed difference between the road wheel rpm and the engine rpm (more or less). The higher the stall speed the more torque available at the rear wheels. The downside is that the higher the stall speed the more inefficient the torque convertor at stall.

<1> (even for a flat torque curve engine with a constant throttle opening – ie at constant engine output torque)

Regards,

aa

[aiboart]

.

Edited 28/11/07 06:46 AM by aiboart

[TOM1111]

thanks for that

[The_Bogan]

gearbox shipped off to kewish today for rebuild and stallie!!!! cant wait till I egt her back on the road!!!!

[The_Bogan]

should have gearbox back in the car by the end of this week or the start of next week depending on how long it takes to get back!

will keep you all posted on power loss with upgrading the stall convertor and what I do at the drag strip!!