torque curve

[slomodiesel]

Here's one for all you thinkers. I've been noticing on dyno charts on cr cummins (stock or bombed) the torque falls rapidly after 2900 rpm. usually on the down hill slide after 2600 rpm. also i noticed on several 6. 0 powerstrokes the peak is at a higher rpm and the down hill slide is after about 3300rpm. my question is is the steep fall of torque after 2900 rpm due to airflow restriction (cylinder heads) or is it due to fueling?

slomo

 

[Hohn]

I say fueling. Yes, the airflow on the heads sucks, but the boost helps to compensate for that.



The HPCR engines are programmed for peak HP at 2900.



jlh

 

[slomodiesel]

why then do the powerstrokes rpm more? I know the bombed cummins run more boost. I suppose the cam and airflow set the peak. how high of rpms can and have anybody gotten for a torque peak?

slomo

 

[dhill]

I had an '85 ford and the governed engine speed was 3750 rpm's. My '94 power stroke was also 3750. My '97 dodge was 2700 rpm's and I believe the '05 is 3300 or there abouts. The ford engine just runs to a higher rpm.



Dave

 

[SBall]

I'm no authority on this subject but I'd risk sharing my thoughts... .

I've noticed a relationship where as piston bore and cylinder displacement increase, the torque peaks at a lower RPM. The larger bore model also seems to produce it's horsepower (work) by trading lower RPMs for higher torque. I'd love to see Kevin Cameron (TDR writer), his slant on this interesting topic.

Steve

 

[Matt400]

why then do the powerstrokes rpm more?

I would say due to stroke, just guessing on the length so someone who knows the actual numbers can chime in but a shorter stroke motor will rev out more easy than a longer stroke.



As for the drop off at 2900 question I would say fueling to stay within the safe design limits (RPM) of the engine.