Dyno and Pulley Adjustments

[Sputniks]

Here is the email response to a question regarding STM adjustable belt pulleys (rollers). Aside that they weight 1/3 of the stock steel units they offer some extra adjust-ability.



"...
they are and adjustable pulley that moves in 2 degree increments, so its very easy to dial in cam timing while using on the dyno. the degree wheel doesn't need setup every time you want to make a change on the dyno..."

I have never heard the belt timing is adjusted during Dyno sessions. I always thought Dyno is about creating the fuel to air ratio map. I would appreciate if someone clarifies why and how the rollers can be used on Dyno to time the belts.

[meme]

It is the same concept on cars. Use adjustable cam sprockets to advance or retard cam timing as need to get the engine running in the sweet spot. Basically you can have the valves open sooner or later relative to piston.

[Sputniks]

Originally Posted by meme

It is the same concept on cars. Use adjustable cam sprockets to advance or retard cam timing as need to get the engine running in the sweet spot. Basically you can have the valves open sooner or later relative to piston.

Do the stock Streetfighter belt rollers (pulleys) allow a such adjustment?

[Ricko]

No.

[FlyingQ]

Originally Posted by Ricko

No.

Not true (sorry for the double negative).

Yes, the cam timing can be adjusted on all 4 valve motors and 1100/1000 2 valve motors. That's how the cam timing gets "degreed" using a degree wheel. Cheers.

[DucDuk]

Are they worth the time and effort to install or you just better off getting the cams degreed? I am asking only because as stated once the belts start stretching the cams become "un-degreed" but I am not sure that the stretching will enough to truly affect the cam timing prior to the time for replacing the belts.

[Sputniks]

Originally Posted by DucDuk

Are they worth the time and effort to install or you just better off getting the cams degreed? I am asking only because as stated once the belts start stretching the cams become "un-degreed" but I am not sure that the stretching will enough to truly affect the cam timing prior to the time for replacing the belts.

From what I know there are two set of the aluminium pulleys available for 1098 motor. The first set is Ducati Perfomance. DP rollers are "not adjustable". But they weight the same as adjustable STM (weight 1/3 of stock pulleys). STM pulleys are adjustable. But they cost almost three times more than DP pulleys ($550 vs $200).
I was considering the replacement pulleys just because of their weight. While it is probably very cool STM pulleys can be adjusted I just don't know if there are any dyno shops around able to take an advantage of adjustable pulleys.

[tjt1990]

The stock pulleys are adjustable just like these aftermarket ones. The only difference is the material they are made of.