Emission Dyno - car too light

[twobone]

I had a funny experience when getting my car emissions tested.

 

We put the car up on the metal rollers and I was asked to bring it up to 40 KPH.

 

Once I hit about 20KPH, all I got was wheel spin on the rollers. I would get to 4,000 in 1st gear and when I shifted to 2nd I would lose traction.

 

So they called over "Bob" the biggest guy in the shop to sit on my rear bulk head to give enough weight to get it up to speed.

 

 

As an aside, I was surprised that my speedo was not reading while on the dyno. It is mechanical and reads off the gear box right? So if the rear wheels are turning, my speedo should work. Maybe I was too focused on the chaos at the time and did not notice it moving around.

[scannon]

As an aside, I was surprised that my speedo was not reading while on the dyno. It is mechanical and reads off the gear box right? So if the rear wheels are turning, my speedo should work. Maybe I was too focused on the chaos at the time and did not notice it moving around.

Are you sure it is connected to the transmission? The speedo on my Caterham reads the left front wheel lugs with a Hall effect sensor as I could not make the Miata sensor on the transmission play with the Caterham speedo.

[twobone]

I thought about that as my speedo is running fast since I lowered my tire profile. However, I poked around my front axles and can't find any sensor or wires. I will follow the speedo cable and see where she goes.