Does your Z4 rock?

T

TitanTim

Elite
Just an observation :) but when the car is stationary and you blip the throttle quickly does your Zed rock from side to side slightly?

Tim.
 
Dont know, but since I turned "surround" on the stereo ROCKS!!!!!
 
Every rear drive car I have owned has done this. Must be with the engine rocking side to side as supposed front to back in a front drive car..
 
TitanTim said:
Just an observation :) but when the car is stationary and you blip the throttle quickly does your Zed rock from side to side slightly?

Tim.
Click to expand...

That is normal for any car with a longitudinally mounted engine. Change in angular momentum causes the engine to torque against the engine mounts. That makes the car rock a bit.


Our Z4 rolls too.
 
Andrew*Debbie said:
TitanTim said:
Just an observation :) but when the car is stationary and you blip the throttle quickly does your Zed rock from side to side slightly?

Tim.
Click to expand...

That is normal for any car with a longitudinally mounted engine. Change in angular momentum causes the engine to torque against the engine mounts. That makes the car rock a bit.


Our Z4 rolls too.
Click to expand...
+1.
i assume you have a transversely mounted 4 cyl... longitudinally mounted inline 6/8 should not rock side to side as they are in primary balance...(i.e the cylinders are vertical in the case of the 6 and in the case of in v8's, cylinders are opposing and cancel out vibrations)
Thats why 6/8 cylinders are smooth!
 
It's a torque reaction rather than balance thing. The crank spinning one way tries to spin the whole car the opposite way. For every action there is an equal and opposite reaction. 3rd year physics :lol:

By the way, a straight 6 has perfect primary balance, but not secondary. The only engine with perfect primary and secondary balance is a V8.
 
AC Schnitzer UK said:
By the way, a straight 6 has perfect primary balance, but not secondary. The only engine with perfect primary and secondary balance is a V8.
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Surely it would need to be a horizontally opposed 'boxer' 8 to have natural secondary balance without counter balancing shafts? but after that a straight 6 is so close to achieving perfect balance as not to mention, as we know when we spin'em up :thumbsup: .
 
AC Schnitzer UK said:
You're right. Have a read...

http://en.wikipedia.org/wiki/Engine_balance#Primary_and_secondary_balance
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Yea my maths was never great but I always understood it was down to multiples/products of 4 with opposing motions, in a Otto 4 cycle engine anyway but my brain aches the more I try to figure it out :lol:
 
My old Subaru Impreza RS was best at rocking - quite odd at first, and when idle without blipping the throttle too....
 
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