dyno questions

[mtomac]

I will be dynoing my truck for the 1st time in Muncie. Diesel Performance Motorsports is supplying the dyno. It's a mobile drive on Dyno Jet 248. I know every dyno is different (Dyno Jet, Mustang, ect) has anyone run on DPM's dyno or a Dyno Jet 248?

I know I need to make max boost to show good power on the dyno. Will I have enough spool time on this dyno if I slowly roll on the power or should I give get it rolling then give it hell right away?

Would I be better off running my BFG 285x75x16's or the stock FS 245x75x16's?

Should I put weight in the bed?

Will the 5th gear lock out work well enough if there isn't a tech 2?

Any other dynoing hints/tips?

[Kennedy]

Keep in mind, my only DJ experience is from my bike, but in general:


Max boost will not likely happen as the DJ is not capable of loading a diesel as heavily as a load cell type. Fine line between holding the TCC lockup and releasing with too much pedal input at too low a speed. T/H will hold lockup much deeper, BUT will command the shift into 4th later, hence the need for the T2.


Not sure how they run The DJ. 1-5 gears, or rolling 4th. To get into 4th gear at a low RPM, you will need the Tech 2.


They say smaller diameter is better so long as they hook up.


Weight is a win/lose thing. Weight helps traction, but will increase rolling resistance.


Drive around the block a few times first so you have 140-150

[mtomac]

wouldn't the bigger tires and weight help load the motor? or isn't it enough because of the type of dyno?

would it help to deprive the wastegate of boost pressure?

how about unplugging the wire/wires to the ac compressor?

any way of keeping the cooling fan clutch from fully locking up and roaring like a hoover with a plugged bag?

[ 05-19-2003: Message edited by: Micheal Tomac ]</p>

[CPMac632]

I have ran on that dyno and other 248's. I'm not sure on the tire height but the taller lug tire will take more power to accelerate. They run from a low rpm in 4th and the powerstrokes they let shift down and then up thru the gears to overdrive so I assume that is what they will do if there is no tech2. They also generally run the truck for you but I did see a person or two run their own truck. You shouldn't get it hot enough to engage the fan. Like John said make sure to get it warm before running. It should make enough boost and plugging the wastegate won't make any peak hp. When I had my programming set up to come in extremely strong at 1500 I didn't slip the tires and the last time I was on that dyno I had the programming set to come in gradually and made 420 something and it didn't even come close to slipping the tires so you shouldn't need any weight.

[sdaver]

two voodoo dolls and a four leaf clover..........good luck :D :D :D :D :D :D dave

[Kennedy]

I haven't followed the "science" of this in too great a detail, but gear ratio can have a great effect. I believe there needs to be a calibration of roll speed to MPH (or tach pickup) in order to get an accurate reading. I'm sure there is a base calibration entered into the program. If a guy had time to play with this it would be interesting to see just what happens with tire/gear change. There was a run in IL where the guys used 2nd gear :rolleyes: and the stock Dmax made a whopping 198HP. I gather from reading the posts that there was about a 32% increase in the figures when the gear was changed on the trucks that ran later in the day.

http://forums.thedieselstop.com/ubbthreads/showflat.php?Cat=&Board=UBB22&Number=1217639&page=0&view=collapsed&sb=5&o=&fpart=2#Post1220785


I'm not making a whole lotta progress with my dyno project. The old garage is still standing, and the guy I want to build the new one has been "gonna stop by" for over a month now...

[Amianthus]

Dynos are a pretty funny thing.

They break down into two basic catagories.
Inertial (i.e. Dynojet) and Load Cell (i.e. Mustang).

The inertial dynos work by taking a fixed mass and accelerating it. Based on the mass and rate of acceleration, you can calculate HP (or watts). And when you plot HP vs. engine RPM you can get torque.
Good side- Extremely consistant, error resistant, and easy to operate.
Bad side- Unable to fully load our engines. Power curve lags behind actual power curve.

The load cell type dynos work by applying a measured load to the engine. There are several types of these. Eddy-current (most popular), water brake (most accurate), and other versions that have a deflecting brake of some sort.
The load is measured by taking the deflection of the brake (or the pressures in water brake type) and the speed of the rollers. The measured force (road load in ft-lbs) is paired up with speed to calculate HP. Then if you have enigne RPM, you can calculate torque.
Good side- Ability to fully load test vehicle and maintain consistant speed and loading, more accurate than inertial dynos.
Bad Side- Traction can be a problem, not as consistant, subject to larger operator error, more difficult to operate.

The most accurate way to get an accurate power measurement of an engine is to do what is called a pull-down test. You run the engine up to the governor and let the brake load it so much that it pulls the engine down to a certain point (usually just above idle) and then start releasing the brake taking data points on the way back up. This test usually takes around 15 seconds. Problem is, if you were to try this with the engine in a vehicle, good luck maintaining traction. Not to mention getting full fueling in direct drive with an auto. It's tough.

This may give you more questions, than answers. But it's a little more information than most people usually see. Hopefully it will help.