Wondering why the torque curve drops off. Is there a way to alter torque management to keep it flat?

 

I'm hoping someone with a little more technical knowledge can explain why the power and torque curves don't intersect at 5250? I thought that's the way it should always be?

 

I wonder what they can do for the NA XF.

 

All Dyno's reporting Horsepower (HP) and Torque (lb-ft), should always have the torque curve and HP curve intercept at 5250.

The reason is, HP is a byproduct of Torque and RPM, as in:

HP = (Torque x RPM)/ 5252 (constant).

So when RPM = 5252, you have a brief moment where HP = Torque, hence they overlap at that one spot (5252rpm on the plot).

What is even more perplexing is the before and after dyno, have the curves intercepting at different RPMs and neither one is 5252.
Before Dyno: ~5900rpm
After Dyno: ~6100rpm

The only reason is some dynos have a calibration feature that allows you determine your tach signal (RPM) with out actually tapping a coil or the specific tach signal on the vehicle, the shop simply goes through a calibration process with vehicle in the specified gear, and based on the speed of the roller(s) the dyno operator has to target a specific rpm and the dyno itself is set into a learning calibration mode, to gather they rpm of the engine.

 

If the calibration is off, as it clearly looks like it is since the curves don't line up at 5252, what does that do to the results? I'm assuming higher?

 

How much was the cost for this ??

 

This is just a theory of mine, the only way to know for sure is if Maryland was to ask Eurocharged for an explanation...

In my opinion, if the calibration is off then the whole run is off. Whether that's representative of higher numbers? I don't know.

 

The scale is different on each side of the graph, that's why they don't intersect at the 5250 point. However if the scale was the same on each side they would.

For example both tq and hp curves make the same numbers at 5250 rpm but because of the difference in scale they don't meet at that point on the graph.

If they rescaled it to make the graph match numbers on both sides then it appears it would intersect at the proper point.

 

Thanks, Matt. I think you are right on the chart explanation. When you compare the scales on their respective sides to torque and hp, they appear to line up at 5252 (or as close as I can tell at around 455hp/tq @5250). On a couple other points raised in other posts: the drop off in the torque curve appears to be right in line with the stock dyno run (the tail at the end of the post-tune run is probably as they were laying off the gas close to the redline - I think it's after the shift point regardless, so it shouldn't matter). In any event, I'll leave that to others to determine whether it is an acceptable drop off. As for cost, Eurocharged charges $1000 for the pulley and tune (they ran a black Friday special back in November, which is when I actually purchased mine). The install for the pulley was about $240, which is a little more than than they charge for other pulley installs because the Jag pulleys are such a pain in the rear to remove.

 

That definitely makes sense. I didn't notice that they had run different scales for horsepower and torque, and then changed again for the after runs. I wouldn't think that this was necessary on a car that develops very similar hp and torque figures....