Engine/Transmission (1998.5 - 2002) Safe to do on the Dyno???

[Sticks]

I am pondering taking my front drive shaft off (for added safety), putting her in 4 low (2 low with my lockout switch) and doing a run.



Will the drive line hold up to a run on the rollers (dynojet) in 6th? I am curious to see what the results are.



02 3500 ETH/DEE, Edge EZ, Stage II injectors, Water/Meth injection.

 

[SEmerson]

I would think you would ripe throught the gear to fast to get spool.

 

[Dkuhlman]

While I think you could get away with it on a set of dyno rollers, I've been told it's not a good practice in general. By utilizing low range in the transfer case, you're effetively doubling the torque multiplication but only running it out of half of the normal output, i. e. the rear drive only. This could lead to a transfer case failure.



4-wheel drive dyno anyone?

 

[jetenginedoctor]

There would be no benefit to testing in low range. If anything, you would experience lower power figures because there would be greater losses in the transmission and transfer case. Whenever possible, we test in whatever gear is 1:1 or thereabouts in order to negate as much driveline frictional and inertial losses as possible. On our dyno, we can test in any gear we want to and set the ramp rate to suit the vehicle being tested. Like I say, there would be no benefit to pulling the front driveshaft, other than getting under the truck long enough to find something broken needing to be fixed.



Brian Kennedy



DynoDynamics

 

[Sticks]

I knew the HP would be lower, but my thinking was that the TQ would be spooky high. But if all it is going to do is drop the numbers acorss the board, then that is a little depressing.

 

[KLockliear]

The TQ is calculated on an inertia dyno by the MPH/RPM ratio (number of RPM change per 1 MPH change). Basically, this negates the driveline mechanical advantage as far as showing the torque figure. Your best bet with the mods you have is to dyno in 5th on a 5-speed or 6th on a 6-speed in 2WD HI.

 

[ronco]

I tend to agree with everyone here. In low range, you are basically unable to properly load the engine and therefore will not get accurate HP/TQ readings. I ran my truck in O/D with the convertor locked to get an accurate measurement. HTH





Ronco

 

[jetenginedoctor]

I can load your truck in any gear. There is no point in it, though. There is a measurable amount of power lost within the geartrain whenever you're increasing the mechanical advantage (underdrive) or decreasing the mechanical advantage (overdrive) of the engine with a transmission. If you test in whatever gear gives a straight-through ratio, you are doing as much as you can to negate geartrain losses within the transmission. If it's engine torque that you're trying to fudge, testing in a lower gear or in a completely different transfer case range won't change anything. In order to ESTIMATE engine torque on a chassis dynamometer, you've got to try to calculate out the frictional and inertial affects of everything that connects the engine to the rollers of the dyno. There is NO SUCH THING as a chassis dyno that gives a real crankshaft torque figure, as that's NOT what it's measuring. A chassis dyno measures power at the wheels, or road horsepower. Any crankshaft power or torque figures are based on assumed values, and are an estimate AT BEST. Our dynos can graph in road HP and tractive effort (what a chassis dyno actually measures) or an estimated crankshaft HP and TQ based on a set of assumed values. There are far too many dynamics to take into account for any chassis dyno to claim to give actual crankshaft power numbers. Don't get sucked into that line of thinking.