I upgraded my MM's to prothane bullets and noticed a few changeshowever, one of them has me baffled.

My idle RPM seems to have dropped about 200 RPM. I've made no other mechanical changes to the car in months. Its got to have something to do with disrupting the vibration harmonics in the engine.

Does any body has a theory on this? or an explanation of what is happening?

 

did it happen right away or did you just notice, due to maybe its something else, my idel dropped the same and i cleaned my Throttle body but you need to really clean it, You need to open the blades and physically clean behind them as far as you can. The black crap you take out will amaze you. It worked on my car and rpms retruned. So try that and see if it works

 

didnt happen with my LT and motor mount install

 

I'm pretty intimate with this car and notice everything. Besides the idle vibrating, its the first things I noticed after the MM install.

The increased vibration seems to impact a lot of things. The second thing I noticed was that my car sounds louder. Keep in mind that I'm not in to super loud exhaust. I'm running LT's with the stock mufflers but, its definately louder after the MM install. I know it sounds unlikely but, I'm not making stuff up. Its got to be the increased harmonics from the vibration.

 

so whats the diff between the stock mm and the new ones

 

Stock are heavy, fluid mounts and isolate all of the engine vibrations.

Prothane are some type of polyurathane and are lighter,stiffer and safer (you won't break a motor mount) if you are going way big on power. However, they add a lot of idle vibration to the car. It makes it feel like a race car.

 

got yaa thanks

 

are the mounts not seated properly?.....I think the mounts do create more noise and vibration thru the car as they note that on the product. Makes sense as they are stiffer and torque is transferred differently (better). Wish I had an answer for the idle drop though...

 

prothane motor mounts do drop the engine about 0.5 inches in height............ minor detail they dont tell you. i had some custom 0.5 inch aluminium spacers machined to raise the motor back up.

 

Thanks for the input Eric.
Where have you been kid?

That's the problem with aftermarket stuff...
They conveniently forget to tell you about the details that would blow the sale.
******!