Nhra releases 2017 rule book amendments

[Carguy49]

Mark, since you work with automatics all the time, I have a question for you. Is there a limit as to when an automatic trans can be made to shift by itself?

[ss3011]

Most governors , or auto 1-2 shifts are based on output shaft rpm . Electronic shifts are based on engine speed . The difference is on good weather days a governor shift will appear to shift at a higher rpm , due to converter slip . Electronic shifts will shift at the same rpm regardless of the weather . Might be a problem trying to dial in a car if the weather changes during eliminations .

[ALMACK]

Originally Posted by ss3011

Most governors , or auto 1-2 shifts are based on output shaft rpm . Electronic shifts are based on engine speed . The difference is on good weather days a governor shift will appear to shift at a higher rpm , due to converter slip . Electronic shifts will shift at the same rpm regardless of the weather . Might be a problem trying to dial in a car if the weather changes during eliminations .

My IHRA Pure Stocker has the electronic auto and after I installed the Baumann shift kit, it automatically shifts dead on @ 5,300 every pass, every gear

[ss3011]

Originally Posted by ALMACK

My IHRA Pure Stocker has the electronic auto and after I installed the Baumann shift kit, it automatically shifts dead on @ 5,300 every pass, every gear

Does your transmission have a governor ? When I raced Pure Stock we had to run the stock 13" converter , which was pretty tight , so there was not much slip in the converter at the shift point . Has the Pure Stock rules been changed , so it allows a loose converter ?

[ALMACK]

Originally Posted by ss3011

Does your transmission have a governor ? When I raced Pure Stock we had to run the stock 13" converter , which was pretty tight , so there was not much slip in the converter at the shift point . Has the Pure Stock rules been changed , so it allows a loose converter ?

I do not believe it has a governor.
The ECU tells the internal shift solonoids when to open/close.

All I know is that the factory ECU does a much better job of hitting the shift points than I could ever do with a ratchet shifter

Also....any converter allowed in PS now.

[kdanner]

Originally Posted by ss3011

Most governors , or auto 1-2 shifts are based on output shaft rpm . Electronic shifts are based on engine speed . The difference is on good weather days a governor shift will appear to shift at a higher rpm , due to converter slip . Electronic shifts will shift at the same rpm regardless of the weather . Might be a problem trying to dial in a car if the weather changes during eliminations .

Have to disagree/clarify this. I chase this with newer Fords and the 6 speed auto all the time. First, they don't necessarily shift based on RPM. They can, but more often than not it is based on MPH so really output shaft speed just like the old transmissions. I can't speak to the other brands as I don't know what they use. Also consider the amount of time between the shift being commanded and finally completed. Engine RPM continues to rise, then pulls down until finally achieving zero slippage once the correct elements are fully locked providing the next gear ratio. On those good weather days when the engine accelerates quicker, you'll see more peak RPM during the shift which leads to more initial RPM in the next gear. Probably better than a governor, yes, but certainly not perfect across all conditions.