dyno conundrum

[hoveringuy]

It's a huge PITA to tie a car down to use all the rollers... I really wonder why they would do that instead of just disengaging the clutch for the front rollers.

Good question! If I had known the clutch can be disengaged I would have insisted on it. It will take someone like me to raise the bullshit flag and have Dynojet call them to instruct them how to use it.

They had a shiny, new addition with no clue how to use it, then say my car is down on power. I will have an answer from Dynojet tommorow when I send the .drf files in.

[LowR3V'in]

Would you get the same curve on a awd dyno as normal? Just down on power?

[hoveringuy]

I sent the run files in.

Dynojet's response:

"The configuration of your runs looks correct for their dyno. You have correctly identified a big issue though, the fact that the car was run in a different gear. This may be the culprit of all the difference you are seeing. You should repeat the run, in the same gear as your previous dyno run. Also, I would have them disconnect the LINX system and run only on the rear roller as you did before. Adding all that extra inertia, especially with a car with this amount of HP, will lengthen the runs out quite a bit. Also, you will have some parasitic losses associated with spinning your front tires. For consistency, you want to run the dyno as they did before, in 2WD mode."

In other words, they wasted your money because the data is meaningless.

[KennyT]

Go back to the shop with that email printed. Parasitic loss = HP loss. Ask them for a run in 3rd gear with the dyno in 2wd mode. If they won't heed your request make the name of the shop known so we can avoid wasting our money.

[hoveringuy]

I went back to the same shop for a "re-do". The first run with the wheels off the front roller were completely normal and I knew instantly that had been the problem. The drums were still linked, but the front drum was spinning by itself.

I got some good data with different cam profiles including a very unexpected result.

Kids, DON"T DRINK AND PROGRAM.

I got a weird glitch on two of my runs but knew it wasn't the dyno because I could hear my cams slamming back and forth. I had a discontinuity in one of my programmed intake cam profiles so that the intake cam went from full retard, to full advance, and then back to full retard (40 degrees each way).

The waviness of the lines is because of resonance in the belt between the front and rear drums.



The dyno captured it perfectly!