6.0 Litre V8 Ls2 into 944 Turbo

[333pg333]

ORIGINAL: AndrewS

ORIGINAL: zcacogp

ORIGINAL: AndrewS
... the plan is to program the PCM to limit the torque in specific gears at certain points to ensure that no component suffers any undue torsional stress when the throttle is mashed to the floor.

Ummm, why would this help? Given that the component giving concern is the torque tube, and this is between the engine and the gearbox, limiting the engine torque in any one gear won't help. It is subjected to the full torque output of the engine (at full throttle, naturally), no matter which gear the transmission is in ...

(Please feel free to correct me if I am missing something! [] )


Oli.

Hi Oli,

Best way to explain is as follows:

Imagine you have a wooden shaft with a handle at one end and a large heavy weight at the other end. The wooden shaft is supported at both ends by mounts and will turn freely (see picture)

If you violently turn the handle, the shaft may snap. If you turn it more gently and then gradually increase the speed and force with which you are turning it, the weight will turn and the speed of the weight turning will increase. When the weight is turning quickly and you increase the force at which you are turning the handle - the shaft will not be as stressed as if you attempt to turn it with great force when the weight was stationary.

This is the principle of torque management which can be achieved electronically.

Regards,
Andrew

That's a good simile Andrew. So this isn't a torque management tool based on sensors or 'live' information like a traction control, this is something that gets pre programmed into the 'ECU' so those limits are always pre set? So you mash the throttle and it will always respond in the same manner? Perhaps I'm simplifying this, but if that's the case I'm not sure that appeals 100%. However overall at 20k for what you describe, it sounds like a great deal. To what level is the rest of the car refurbished? New interior, paint, wheels etc?

 

[Neil Haughey]

Torque limiting is nothing new, its just we are not used to it as we have such old cars. Other manufacturers have been doing it for a number of years, ISTR the Saab 9-3 viggen must have been 8 years ago now had a boost limit in 1st and 2nd gear for exactly the same reason and to lessen the inevitable torque steer and wheel spin. I am fairly sure most modern engine management programs on high powered cars feeds in the power in such a way as to limit torque spikes, they would have to otherwise there is no way any of the big companies could produce these 400+ Bhp monsters for the money they do.

 

[sawood12]

It has to be an open control circuit as there is no way of actually measuring torque as it really depends upon how much grip you have. Also if your driven wheels start to tramp such that they momentarily loose traction then regain it then the initial shock loading of the transmission will spike to many hundreds of times higher for a split second meaning that even if you had a detection system you couldn't react quickly enough. The torque management system simply limits the power of the engine so if you floor the throttle then the fuel system and ignition system wont give you full beans right away and will allow the power to be applied in a controlled way. I'm guessing this system can customised for the application to minimise the amount of restriction to suit how much grip you have? I'm guessing if you have very wide sticky tyres you'd need more restriction as the torque loading will be higher.

 

[333pg333]

That's sort of what I was thinking Scott. I mean in a basic sense my old Apexi EBC could be pre loaded with set boost at various rpms in various gears. All a bit to pre conceived and pre set for my liking.

As opposed to a traction control unit that is detecting live signals and reacting thus. So by putting the big wide sticky tyres on I can take advantage of the extra grip until loss of traction and then it cuts boost/ign or whatever. If I've got a pre set torque limiter, then in effect I'm limiting the amount of grunt I can get to the ground....but perhaps this is more of a component saving device than a power loading one?

 

[barks944]

ORIGINAL: 333pg333

That's sort of what I was thinking Scott. I mean in a basic sense my old Apexi EBC could be pre loaded with set boost at various rpms in various gears. All a bit to pre conceived and pre set for my liking.

As opposed to a traction control unit that is detecting live signals and reacting thus. So by putting the big wide sticky tyres on I can take advantage of the extra grip until loss of traction and then it cuts boost/ign or whatever. If I've got a pre set torque limiter, then in effect I'm limiting the amount of grunt I can get to the ground....but perhaps this is more of a component saving device than a power loading one?

With traction control the damage is done, as in you have already lots traction, this is ok with traction control as there is no harm in a bit of wheel spin. When it comes to boost control or torque limiting for protection of engine or drive train components if you exceed limits, boost or torque, then its too late the damage is done. This can be achieved with closed loop control but certainly in the case of torque this is a difficult thing to measure.

Lets be honest here the engine produces massive ammounts of grunt, and really the limiting we are talking about here just stops really fast torque spikes, we are talking 1-2 seconds here probably less. I don't think they are suggesting limiting torque absolutely just stoping it going from 0-400 too quickly .

 

[sawood12]

Pat, you are right in your analogy, but there is a slight difference. You are talking about traction control, but in this case we're talking about a safety device to protect your transmission from breaking. If you have more grip the more torque will be transmitted through the transmission, so if the engine is capable of delivering transmission busting torque then you want to either beef up your transmission or limit it at lower speeds (torque drops off with speed and RPM). As Tom says, this will just be live in the very initial take up of power application at low speeds.

 

[333pg333]

Yep, we're all saying the same thing. I think for the intended market and the fact that they're offering a warranty, the torque limiting device is probably a must.
I sometimes get a bit narrow minded when I'm writing out loud. []

 

[Copperman05]

http://www.youtube.com/watch?v=uCzGoefuX1s

 

[Neil Haughey]

Sounds good [8D]