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Re: the secondary torque peak - something else I just remembered . . . Didn't the Texas dyno operator lift off the throttle to avoid the rev-limiter? That would better explain the lack of the mini-torque peak at the top on those dynos . . . .
[QUOTE]Originally posted by Elistan
One other way that the Dynapack and Dynojet torque curves differ is the VTEC transition around 6000rpm.
I've been reading through the Dynapack tech verbage at http://www.dynapackusa.com/tech.htm, so I think I have a better understanding of how the unit works than I did before. It seems pretty neat, really. From what I can tell, the car's wheel hubs get connected to a hydaulic pump which pumps water through a manifold with a computer controlled flow rate - some sort of valve, I assume. (Some of this I'm speculating, since their website isn't overly specific.) The Dynapack computer reads the hub speed and fluid pressure in the manifold, and I assume based on the known flow characteristic of the valve, can determine the amount of fource being exerted by the hydraulic pumps. Since the valves are controllable, the actual speeds of the hydraulic pumps can be raised or lowered at will. (I don't see any mention of a spark sensor like the Dynojet has, so I assume the software has to calculate RPMs based on user-entered gearing information.)
But all of this begs the question - if the Dynapack has enough enhanced resolution compared to a Dynojet to show a torque spike near 8000rpm, why does it appear to have a lower enough resolution to show such a slow VTEC translation? I would have expected that if one type of machine were more precise than the other, that one would be more precise over the entire operating range.
Regarding the question of Kenny Tran lifting early on the North Texas dyno runs, that's simply something one of the attendants wondered about - and that person was satisfied when they saw the tach flash, in addition to the dyno plots. I've included the plot for the 700mile '04 car, and you can see the engine reach 8100rpm. (Well, obviously not the case in the first run, but the second or third definitely went all the way.)
One caveat is that these graphs are at SAE smoothing factor 5. I have the actual data files, so I'll look at them again when I get the chance with no smoothing at all, and see what they show then. In any case, the torque spike on the Dynapack plot appears to start at 7500 to 7600 rpm, and the Dynojet should at least be able to show that, right?
Originally posted by Daemione
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The dynapack is a more sensitive instrument - they can pick up the difference in torque output from simply turning on your headlights - a dynojet would never be able to see that.
Since headlight draws power from battery and/or alternator, and since the drag from alternator is essentially constant regardless of the electrical load, how is this possible?
Originally posted by RedondoS2K
Since headlight draws power from battery and/or alternator, and since the drag from alternator is essentially constant regardless of the electrical load, how is this possible?
I'd need an EE to confirm this, but I'm pretty sure the load from the alternator is not constant and is dependent on the electrical load on the system.
For what it's worth, when my car had a really loud exhaust I could hear the exhaust note change slightly when turning on the lights, even though RPM didn't change.
I agree with mxt_77, my understanding is that the load is variable.
That's how the Civic Hybrid and Insight work - the generator/IMA only draws power when braking is required, which is done by varrying the load/drag.
