Prior to starting this project I went over my Jeep very well. Making sure everything was tuned up and all pertinent parts where replaced. Things like Ignition Wires, Cap, Rotor, and plugs, ECT.
Then I contacted my friend up in Indy to make an appointment on his Dynamometer. Turns out I never made it there. Instead he directed me to one of his friends who just recently opened up a shop in Lexington and installed a Four Wheel Drive state of the art Mustang Dynamometer.
To make a long story short I was given 3 hours on this machine and made three recorded runs in my TJ with a stock engine while in Four Wheel Drive.
This Dyno is like no other. Basically it is an ego breaker. This machine not only applies force against the tires but also compensates for weight and wind resistance based on frontal profile of the vehicle. (Read that, Jeep has aerodynamics, it is just the functional equivelent of a brick!!)
In Stock form Jeep advertised that my 97 4.0L engine put out 181 HP and 220 ft/lbs of torque.
As fact would have it there is no way on earth for me to be able to verify this as Jeep measures it at the flywheel and not at the tires. Nor does Jeep compensate for the Jeeps Weight or Wind Resistance. Basically not very useful for me to use in comparison.
So, I have to work with what I have; a real Jeep, in four-wheel drive, and having the ability to measure working torque at the tires.
(Horse Power, on any dyno is calculated based on Measured Torque. Read that; Dyno?s only measure Torque in foot/pounds, not Horse Power)
Anyway here are the Torque and Horse Power Curves for my Jeep in Four Wheel Drive, at the tires, compensated for weight and wind resistance, and of course Friction Losses.
Told you it was an ego buster!
But even so I was surprised just how much power was lost between what the dyno said my Jeep had at the tires and what Jeep said it had at the flywheel when new.
Was this caused by everything already mentioned? Or was it simply my engine was not in anywhere near as good a shape as I thought it was?
Well one way to find out! Pull a 2004 Rubicon up on the Dyno with ony 4K miles on it.
Here is how that looked in data format, as compared to my Jeep.
As I think you can see, the losses at the tires for both my 1997 Jeep TJ and an almost new 2004 Rubicon are very similar when compared to the factory published power output at the flywheel.
I feel better now. (So it is legitimately an ego buster regardless of which vehicle.) I'm a happy camper!
That?s about it for tonight. Time to go to sleep.
Hopefully more tomorrow.
Have a great night folks.
Frank