In connection with my chip tuning, I wanted to do before and after tests on a dynamometer. (I should say that, a couple of months ago, I knew ABSOLUTELY nothing about dyno tests...now I know just a wee bit more! ) As I looked into the matter, I learned about needing to put the car in dyno mode to completely disable the traction control and that simply turning ESP off would not accomplish that. The issue arises because of the wheel speed differential on some dynos.

However, the dyno shop that I used has a dyno (it's a Mustang AWD 500) where the front and rear rollers spin at exactly the same speed; so that, as far as the car is concerned, it's as if it's driving on the road. So, based on my conversation with the proprietor, I concluded that putting the car in dyno mode was a non issue.

When I took the car for the first test, the tech put the car facing forward on the dyno and the car wouldn't move....he couldn't explain why. So, he then put the car on facing backward and it ran fine. He was able to do three pulls without incident.

Then I brought the car back after the chip tune. Still not knowing why the test wouldn't work with the car facing forward, he put the car on facing backward and it wouldn't work. Then he tried facing forward and it still wouldn't work. At that point he concluded that he wouldn't be able to do the test.

He explained to me that he's done tests on all sorts of cars, including Mercedes newer than mine, and he's never had this sort of a problem. So, he's frustrated that he's wasted an hour of his time with my car with its inexplicable quirk....and I'm of course frustrated that I can't get a second test done on the same dyno.

While I'm quite certain that I'm not exactly his favorite customer, he is willing to try the test again provided that I (a) pay up front and (b) figure out what needs to be done differently with my car. It makes no sense for me to go to another shop because it would be a different dyno with a different set of variables.

Does anyone have any insights or suggestions? Thanks so much!

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife