Atlanta Dyno Day Pics & Videos (now up)!!
11-23-2004, 07:40 PM
#31
Before I aks more questions, I want to say a HUGE thanks for having the courage to come here and answer all these questions. I am the one who emailed dynapack about the results as I could not find enough information to answer my own questions. I really appreciate you taking the time to answer!
Makes much more sense now.
So this has to do with not having enough time to set up the machine to each vehicle? I.e. if someone went to you for dyno time this would not occur?
Kind of the industry standard for scaling though, wouldnt you say? Say virtually any printout from a Dynojet, Mustang, etc?
When running a 951 like this how do you get over the issue of boost? A properly running 951 will never make full boost in 2nd gear which is probably where you would have to be to have enough torque to turn the machine?
Thanks for the information.
BTW, did Dynapack contact you about the charts? I sent them snaps as they asked for them.
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Gear Ratio:
The DynoPack dyno reads the wheel RPM and calculates engine RPM using the gear ratio. If the actual gear ratio (transmission ratio * differential ratio) is known, this number is entered. Alternatively, the dyno operator can set gear ratio by using the vehicle tachometer.
In the interest of time at the Open House the vehicle tachometers were used to determine gear ratio. For serious dyno sessions, the engine RPM is measured using a calibrated optical tachometer.
The DynoPack dyno reads the wheel RPM and calculates engine RPM using the gear ratio. If the actual gear ratio (transmission ratio * differential ratio) is known, this number is entered. Alternatively, the dyno operator can set gear ratio by using the vehicle tachometer.
In the interest of time at the Open House the vehicle tachometers were used to determine gear ratio. For serious dyno sessions, the engine RPM is measured using a calibrated optical tachometer.
Loops in Dyno Sheets:
The DynoPack dyno uses hydraulic force controlled by valves to apply torque to the axles. If the engine suddenly loses power for whatever reason, the computer may not be able to release torque quickly enough to allow the engine to smoothly accelerate. When power loss is severe, the RPM decreases before continuing the sweep. This produces a “loop” in the horsepower and torque curves. The driver also has to smoothly bring the RPM up to the initial RPM and then apply full Power in a controlled manner.
The DynoPack dyno uses hydraulic force controlled by valves to apply torque to the axles. If the engine suddenly loses power for whatever reason, the computer may not be able to release torque quickly enough to allow the engine to smoothly accelerate. When power loss is severe, the RPM decreases before continuing the sweep. This produces a “loop” in the horsepower and torque curves. The driver also has to smoothly bring the RPM up to the initial RPM and then apply full Power in a controlled manner.
5252:
I don’t know where this urban legend got started, but torque and horsepower curves on graphs only cross at 5252RPM under one special condition!!! Unless the scaling is the same for both torque and horsepower the curves will NOT cross at 5252. By the Way, 5252 is the constant to compute horsepower when torque is expressed in Ft-Lb and speed in rev/min.
I don’t know where this urban legend got started, but torque and horsepower curves on graphs only cross at 5252RPM under one special condition!!! Unless the scaling is the same for both torque and horsepower the curves will NOT cross at 5252. By the Way, 5252 is the constant to compute horsepower when torque is expressed in Ft-Lb and speed in rev/min.
Excessive Engine Loading:
This is a problem I have discussed with DynaPack. Engines with low torque at low RPM are difficult to dyno on the DynaPack 3000. Running in a lower gear usually solves the problem, but a poorly tuned or sick engine will not get past the residual torque of the dyno.
This is a problem I have discussed with DynaPack. Engines with low torque at low RPM are difficult to dyno on the DynaPack 3000. Running in a lower gear usually solves the problem, but a poorly tuned or sick engine will not get past the residual torque of the dyno.
Thanks for the information.
BTW, did Dynapack contact you about the charts? I sent them snaps as they asked for them.
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11-23-2004, 07:50 PM
#32
Going with the pack
is quite monotonous.
Rennlist Member
is quite monotonous.
Rennlist Member
Excessive loading - this isn't when trying to get to 3000 rpm is it? Cause I was full boost 15psi at that point and not moving... 250+ rwtq is plenty enough to turn the dyno...
