More Power!

[Ivor_E_Tower]

:D

[johnb80]

It wouldn't matter if you were trying to pull a house up a mountain 310Nm is 310Nm it wont produce anymore. :D

unless amplified by your torque convertor....

 

The torque convertor can and does multiply torque when it slips (as does a clutch)

Torque is the amount of turning force the engine creates, surely all a torque converter can do is loose it? If it really could amplify it where does the extra power come from? why do they get hot in use? if it doesn't need any extra power then it would seem we have perpetual motion machines i.e. connect the output back to the input (more torque comes out than goes in) therefore the thing should runaway :huh:

 

Regards - JB

[Guest marcusheawood]

...Here you are JB: http://www.jatco.co.jp/ENGLISH/PRODUCTS/at_principle.html :D

[seatkid]

f it really could amplify it where does the extra power come from? why do they get hot in use? if it doesn't need any extra power then it would seem we have perpetual motion machines i.e. connect the output back to the input (more torque comes out than goes in) therefore the thing should runaway  :D

No extra power at all, in fact power is conserved (remember Newton?). When a torque converter slips, the product

 

torque * rotational speed (i.e. power)

 

is the same at the input as the output. In other words,

 

power going in = power going out less a bit for fluid churning losses (efficiency)

 

(Otherwise you would have to dissipate xxx kw in the torque conveter itself!)

 

So when the input shaft of a torque converter rotates at twice the speed of the output shaft, the torque is multiplied by a factor of two.

 

From what I can remember when I studied this many years ago, real world convertors multiply torque by a maximum of about four or five times and are designed to slip at low (idling) speed.

 

And that is why automatics are so good at accelerating away from a standstill (compared to a manual car)

 

For homework, I would like you to read chapters 3,4,......... :D

 

 

BTW my previous comments about a clutch amplifying torque may be incorrect however........ :huh:

[johnb80]

I can't admit to understanding how this is possible I bow to the greater knowledge of SEATKID. My flabber is well and truly gasted !

 

Regards - JB

[tim-spam]

A torque converter can indeed multiply torque due to its internal fluid dynamics, and there is a torque multiplication ratio quoted for most. However, in general, the higher the torque multiplication ratio, the higher the losses and the lower the power transmission efficiency. The power transmission efficiency is improved on many modern torque converters by the 'lock-up' facility above certain input speeds.

A clutch, however, can not multiply the torque at all, but has the advantage that when engaged the power transmission efficiency is as near as makes no difference to 100%.

[seatkid]

the higher the torque multiplication ratio, the higher the losses and the lower the power transmission efficiency.

Bit more complex than that! Efficiency is greatest at mid range values - the lockup clutch is used to improve efficiency at the 1:1 speed ratio end (i.e. cruising at speed)

[tim-spam]

I did say, 'in general'. The actual torque multiplication ratio is application dependent and is chosen by the design engineer according to, amongst many other factors, engine torque characteristics, transmission torque / power capacity, desired engine stall speed, etc.. If the design engineer chooses to use a higher torque multiplication factor (due, for example, to an unfavourable engine torque curve), there will tend to be an overall reduction in the efficiency of the application.

 

Another, more general example of considering the application rather than just the individual components, is the torque capacity of the Jatco auto box. If we assume a torque capacity of 400Nm, this would indeed be very marginal for an engine capable of delivering 310Nm torque if the torque multiplcation factor was anything more than around 1.3. However, there are several factors to consider. For example, the torque delivery of the engine may be less than 310Nm at the chosen stall speed. My guess is that the maximum torque delivery will be limited to well within the capacity of the gearbox by traction.

 

Once under way, the torque multiplication factor will quickly fall towards 1, well within the capacity of the gearbox.

[seatkid]

I would imagine the ECU will have be programmed to limit torque in relation to certain engine/road/gear speeds. In effect limiting torque during the inital acceleration phase. The rating of the box is a continuous rating and a short term overload would be permissible (but this info is not specified)

 

So buggering about with tuning boxes will potentially remove the protection afforded by the ECU....

[greg_68]

As an aside, the Alhambra is shortly to be offered with VW's "new" 2.0 PD TDI engine, which is offered with the DSG gearbox in many other VW group cars. Wonder if the Alhambra (and maybe the Sharan) will be offered with this engine-gearbox combination ?

Couple of questions.

 

When does the Galaxy production stop?

 

Is the production of the Sharan and Alhambra going to continue afterwards and if so for how long?

[Guest marcusheawood]

..SK, do you mean the ECU controlling the gearbox or the engine?

 

I cannot see why you would bother fiddling with the engine when the smartarse gearbox can handle all that stuff.

[seatkid]

the ECU controlling the engine......basically the engine mapping should take into account that the torque convertor multiplies torque by 4 or 5 times - when moving off from stationery with foot to the floor - the engine running at 2000 rpm+........it will restrict the torque (power) so that the gbx is not overstressed until the vehicle is moving fast enough (torque multiplier goes down) when it feeds in full power.

 

This might explain why some people feel the Galaxy auto is slow from a start.....

 

If this is the case then tuning boxes would definitely be a bad thing. A remap/rechip may or may not be bad depending on whether the programmer continues to offer the same protection.

 

Of course, all this protection may not exist at all and maybe the torque figure quoted by Jatco is input torque regardless of gear selection and input/output speeds....:D

 

As my dad used to say about auto boxes, electric windows, radios etc......"yet another thing to go wrong..."

[Guest marcusheawood]

The main problem with autoboxes is that you are at the mercy of specialists, it really is true that they are evil boxes operated by witchcraft and black magic! Main dealers shudder at the thought of cracking one open.

 

Unless you have a comprehensive set of special (very expensive) tools and detailed technical manuals there really are no user serviceable parts in there.

 

Everything else is fixable though.

[tim-spam]

I also think that there is absolutely no way that the traction of a FWD car could possibly react significantly more than 310Nm - full acceleration from a rolling start in first gear on a dry road with a manual gearbox produces significant wheelspin. In addition, SK is probably right when he states that the engine ECU will limit the torque under certain circumstances - after all, there is a switch activated by depressing the clutch on a manual gearbox, which reduces the fuelling to assist in changing gear smoothly.

[johnb80]

As my dad used to say about auto boxes, electric windows, radios etc......"yet another thing to go wrong..."

I suppose it's a bit like turbo's, electric starters and electric windscreen wipers, why on earth do you need a heater anyway ?

[seatkid]

:D Heaters used to be optional extras on cars.....a good sheepskin coat was considered sufficient once upon a time (and they didnt sping leaks....) :D

[Guest MATT]

gosh, this thread has got technical. some interesting stuff that has been added here, that was not found in the searches i did.

 

SK:

it will restrict the torque (power) so that the gbx is not overstressed until the vehicle is moving fast enough (torque multiplier goes down) when it feeds in full power.

 

makes sense.

 

i think im going to leave the tuning box alone, there is a lot of "ifs and Buts" surrounding the automatic gear box - and other bits, its not worth risking such an expensive component, especially if it is rated at 325NM.

 

auto boxes are fine, i would have an auto over a manual any day.

 

MATT

[johnb80]

:D Heaters used to be optional extras on cars.....a good sheepskin coat was considered sufficient once upon a time (and they didnt sping leaks....) :D

One of my cars in my earlier life was an original Lotus 7, no heater, no wipers and no roof! I used it day in, day out all weathers including shift work going to work at 05:15 when it was heavy snow (we used to live on the edge of the Penines). Still have fond memories and wish I still had it today, true to say it never went wrong apart from a plastic heel on the contact breakers (remember those) sheared off one night on the way home from afternoon shift. I removed the headlamp to use it as a torch, made a new heel from a tiewrap base and glued it on. It got me home.

 

Regards - JB

[GSMGuy]

John, those were the days m8 - DIY ruled - no need for the AA or RAC!!!!

 

 

Mike