why a certain camshaft for an auto????

disco-v8 · Post by **disco-v8** » Sun Nov 18, 2007 11:26 pm

each time i look at camshafts every company seem to do one for 4x4 auto's

whats so diffent with the cam that its made for an auto box????

is the cam designed to give less torque to stop damaging the box, or is it the other way around?????

basicaly whats so specail about these sort of cams????

Eliot · Post by **Eliot** » Mon Nov 19, 2007 8:50 am

At a guess, it would be a fatter torque curve - in the low/mid region.

disco-v8 · Post by **disco-v8** » Mon Nov 19, 2007 9:31 am

yeah fair enough i already had an idea it would give low down grunt, but ive seen torquer cams already on the market, but they will also do one for the auto box!!!!!

theres got to be something that the auto stops the cam profiler from makeing a better cam, or may be it helps him i dont no!!!!!

ChrisJC · Post by **ChrisJC** » Mon Nov 19, 2007 9:55 am

There's also an issue with torque at idle. I can't recall the exact explanation (Badger did mention this previously), but if you have the wrong cam, when you select drive, the engine may stall because there isn't enough torque.
Obviously not an issue on a manual.

Chris.

ramon alban · Post by **ramon alban** » Mon Nov 19, 2007 11:43 am

ChrisJC wrote:There's also an issue with torque at idle. I can't recall the exact explanation (Badger did mention this previously), but if you have the wrong cam, when you select drive, the engine may stall because there isn't enough torque. Obviously not an issue on a manual.

Chris. On Rover SD1 Efi Auto cars there was a dealer installed retrofit that used the transmission inhibitor switch to energise an air solenoid to bleed metered air from the air rail into the plenum.

This was sufficient to raise the idle speed by about 200 rpm as the car went into Drive or Reverse, thereby preventing stalling. In practice, of course, the potentially raised idle speed and the extra transmission load cancelled each other out so the actual idle speed remained rock steady as the car went in and out of gear. It was an elegant solution!

Exactly the same principle was used on CCOT AirCon cars to energise an air solenoid every time the AirCon clutch kicked in to prevent the AirCon load stalling the engine at idle, except that feature was factory fitted.

Here is the full story of how the transmission stalling problem was identified and resolved by Rover.

http://www.vintagemodelairplane.com/pag ... all01.html