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-   -   Dyno Questions (http://www.jeepgarage.org/f97/dyno-questions-69605.html)

SRTgeek 12-26-2013 04:34 PM

Dyno Questions
 
Hey Guys! Hope you all had a great Christmas! :thumbsup:

With the SRT's putting power to all the wheels, ideally I am assuming an AWD Dyno is best. I have seen Dyno photos though of SRT's with the front tied down, just the rear being dyno'd.

umm... how does that work? Where I live there are no AWD dynos so I am wondering if there is another way to Dyno that works?

I'm somewhat ignorant on dyno technology :lol:

jim383 12-26-2013 06:19 PM

Re: Dyno Questions
 
Quote:

Originally Posted by JDR8 (Post 950444)
Hey Guys! Hope you all had a great Christmas! :thumbsup:

With the SRT's putting power to all the wheels, ideally I am assuming an AWD Dyno is best. I have seen Dyno photos though of SRT's with the front tied down, just the rear being dyno'd.

umm... how does that work? Where I live there are no AWD dynos so I am wondering if there is another way to Dyno that works?

I'm somewhat ignorant on dyno technology :lol:

On the 2w dynos they take out the T/CASE motor(4 bolts) and unplug it and that keeps the front wheels from turning. As far as hp i think on the 2w dyno you may put out more hp BUT i have heard guys say they put out the same BUT i have to think not turning the front wheels you would put out more hp. Go here and read this by builder bill who builds the racing t/cases. Below is a post by builder bill who builds the RACING T/CASES ON THE 5 SPEEDS BUT IT WILL GIVE YOU THE OPERATIONS OF THE TRANSFERCASE.

Ok here is our SRT Transfer case.
Many thanks to Resume Speed for helping with links etc. on this thread!
Thanks also to Blown7 for the help on loading all the photos.

Below link is a basic parts list for our Transfer case:
http://www.wkjeeps.com/misc/Tcase_2008_Parts.pdf

Below is a write up from my Shop Manual:
The NV146 transfer case provides Full-Time Active Four-Wheel Drive for optimum traction in a wide range of conditions
and is used in the Grand Cherokee SRT8 vehicles. The transfer case center differential distributes torque 48
percent to the front axle and 52 percent to the rear axle along with an electronically controlled clutch pack that is
coupled to the center differential for torque biasing. The NV146 electronics provide an active system because it can
anticipate and prevent slip. The transfer case can redistribute 100 percent of torque to the front or rear axle,
depending on need.
The NV146 single-speed transfer case provides the following benefits:
No shift lever or driver interaction required.
Full-time four-wheel drive provides smooth operation and vehicle stability under all conditions because torque
is constantly being transferred.
Even torque distribution provides traction to maintain forward motion under most conditions.
The Brake Traction Control System (BTCS) works in tandem with full-time four-wheel drive. BTCS provides
resistance to any wheel that is slipping to allow additional torque transfer to wheels with traction.
Robust design and improved sealing enhance reliability.
No maintenance required.

Controls for the NV146 transfer case active clutch (torque biasing device) are located in the Final Drive Control
Module (FDCM) and communicated on the CAN C bus. The FDCM monitors wheel speeds at the front and rear
axles to detect wheel slippage. A complete vehicle dynamics model calculates slip at each tire for given vehicleoperating
conditions. The clutch pack in the transfer case is engaged to minimize the speed difference between the
front and rear axle, resulting in torque transfer to the axle with higher traction. The electronically controlled wet clutch pack uses an electric motor to actuate a sector plate. The sector plate actuates a clutch lever that applies
normal force to the multi-disc wet clutch pack bridging the differential. The clutch discs are alternately splined to the
front and rear driveshafts. When normal force is applied to this clutch pack, torque is transferred to equalize speed
differences between front and rear axles.

Unfortunately, the shop manual just copied the text and illustrations from a similar transfer case so I was on my own as far as the dismantling and re-assembly of some components.

Basic operation as I see it:
The shift motor (which some of us unplug from time to time) rotates the shaft that has a cam attached to it. It appears that it can rotate clockwise and counter clockwise. I can see NO harm in unplugging it for the dyno etc. as the shift arm will not engage the clutch pack for the forward output shaft.
The clutch pack is engaged when the cam is rotated...could be partially engaged or fully engaged, therefore increasing the torque to the front wheels. I did note that the clutches in this transfer case which had approximately 6,000 miles (per the junk yard) looked perfect. I did notice a shiny area on the output shaft where the clutches engage though.
The chain and gears look substantial...time will tell!
The one piece output shaft also looks substantial.
One thing that I was surprised at was with the 1 piece output shaft, the torque may be distributed to the front tires (again through the clutch pack) when the rear tires spin, HOWEVER, the rear wheels will still spin the same. This does not take into account the ABS system that will apply the brakes to the spinning wheel(s).

All in all, a pretty straight forward design.

august77 12-26-2013 06:20 PM

Re: Dyno Questions
 
They could have removed the front drive shafts/transfer case, to prevent the front wheels from turning.. by doing that, the Jeep will be running in RWD. You might need to set it to track mod to get the most power to the rear.

august77 12-26-2013 07:49 PM

Re: Dyno Questions
 
Something i found while googling for Jeep SRT Dyno...

SOUTHERN HOTROD JEEP Grand Cherokee SRT-8 2WD dyno instructions - Dodge SRT Forum - SRTConnection


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