Are You Ready Boys n' Girls?? My LS3 baseline

[BLACK10]

Originally Posted by Avalnch

Prior to the dyno runs, the rear axle ratio and tire OD were entered into the computer. I can only assume the Dynapack compensates for tire mass by adding friction at the rear rotors. Also, your standard, roller dyno will lose some HP due to slippage between the wheel and the steel rollers. So, I wouldn't be too surprised that the DynaPack results are higher than standard dynos.

I think that the DynaPack unit provide a truer representation of RWHP. Besides, there's no other dyno machine close by to me.

I'll be going back for another run after my ARH and Pypes exhaust are installed. Will post those results too.

i drive my car with the wheels on

good luck with the mods

[MarylandSpeed]

The dynopack has a few advantages. First off, it is cheapest to insure because the car is not gonna go flying off it. (though Dynopacks are very expensive to purchase for some reason) Secondly it is portable. Lastly with no tires in the equation, traction and friction are not an issue.

For actual tuning, they are good because the numbers are very consistant. You see these used a lot for tuning race cars. The shop here that has a dyopack has race teams from all over the NE coming in because they want to be tuned on that dyno.

That being said for posting "Here's my dyno sheet"..they are not the best. To calculate HP and TQ, you need a gear ratio, engine rpm speed, and drum/hub rpm speed. Main issue with dynopacks is that they do not have engine RPM pickups like say a dynojet to read actual engine RPM's. With a dynopack, the operator manually types in the gear ratio of the gear he is using for the run (normally 4th on a 6 speed). Using the ratio, the dyno then calculates TQ based on hub rpm speed, and also "guesses" RPM's to calculate HP. Meaning the Dynopack says, if the gear ratio is x, and the hubs are spinning x fast, then the engine has to be turning X rpm. Dynopacks have issues in situations where the actual hub speed might become disconnected from engine rpm, such as with a stalled converter. I have also dynopack numbers get skewed because the operator put the wrong gear ratio in. The local shop I mentioned above can't give me a reasonable looking horsepower dyno graph on our supercharged 06 GTO because the high stall speed in the A4 messes with it's engine RPM speed calculations.

A dynojet on the other hand has rpm pickups that connect to a spark plug, so it knows actual engine RPM and is not guessing. You don't have to put a gear ratio in or anything. Basically, the Dynojet uses the engine RPM's and drum speed to calculate the actual gear ratio it is seeing. So a dynojet says if engine RPM is X, and drum speed is X, then we know for sure the gear ratio we use to calculate HP and TQ has to be X.

In short dynojet knows drum speed, and RPM, and uses it to calculate gear ratio. Dynopack uses Hubspeed and a user imputted ratio to calculate (more like guess) engine speed.

Wow..that was a long post. Basically, dynopacks are great for tuning because they eliminate the variables that tires cause...however since they calculate HP in a very different way, you should never compare numbers from a dynojet and dynopack.

When we bought our dyno, we looked at them..however for product testing, I really needed "dynojet" numbers...so that is what we got.

Originally Posted by Avalnch

Yes, those numbers are awesome. It certrainly feels it too.

I think the DynaPack machine is more accurate than a conventional roller dyno. There is no wheel slip since the machine is directly connected to your axle.

But, the true test will be at the track. Hope I can get there after the mods are done and post some results.

[Avalnch]

Originally Posted by EnvyTerra

Are you saying a dynopack can simulate 3900lbs of weight onto the back tires and the rolling resistance of two 65lb wheels/tires versus the road accurately?

If you look at the pics, you can see that the rear hubs are bolted to the DynoPack machine and the car's full weight is placed on them, so there is no "weight simulation" going on here.

If you read the previous post by Maryland Speed (thanks for the tech differences, BTW) you'll note that it states that the wheel rolling resistance is taken out of the equation since they don't exist. This particular shop also has road-racing cars that they tune and consistancy was mentioned.

Friction is the #1 killer of HP, so taking the rolling resistance out of the picture will provide a higher number from the DynaPack. Instead of RWHP, maybe DynaPack runs should be spec'd as RHHP (rear hub horse power).

Regardless, I'm only looking for a baseline to compare future mods anyways, but the higher numbers sure are nice to brag about.