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Engine Specific Info and Questions => IDI Engine => Topic started by: molgrips on October 27, 2008, 03:36:00 am

Title: Mysterious metal block underneath engine
Post by: molgrips on October 27, 2008, 03:36:00 am
On my AAZ, on the rear sub-frame there's a metal block about 6" square sticking out backwards, underneath where the downpipe comes down.

Wtf is it?  Some kind of vibration damping counterweight perhaps?
Title: Mysterious metal block underneath engine
Post by: gldgti on October 27, 2008, 05:12:52 am
you got it in one - its a dead mass presumably for changing some harmonic vibration frequency...

i actually recently pulled mine off, thinking "how much difference could it make?" infact, it has seemed to make a difference - i used to feel some mild steering vibration under high load (like driving up a big hill on the freeway) - now its GONE!

i'm leaving mine off.
Title: Mysterious metal block underneath engine
Post by: molgrips on October 27, 2008, 06:14:57 am
I'm getting a small amount of buzzing and noise at higher revs, when cruising.  I might experiment with it.  Maybe I can tune it some more by adding weight :)

Question is, why would it stop doing whatever job it was designed to do in the first place?
Title: Mysterious metal block underneath engine
Post by: mattbondy on October 27, 2008, 11:59:18 am
rust?
Title: Mysterious metal block underneath engine
Post by: molgrips on October 27, 2008, 01:21:15 pm
The plan is to put the front wheels up on ramps and tie some string or something to the accelerator cable, so I can lie underneath the car and rev it up to 2.5krpm and listen for any noise.  Can't hear a thing from the top apart from normal engine noise.
Title: Mysterious metal block underneath engine
Post by: RabbitJockey on October 27, 2008, 01:52:07 pm
my sisters 2.0 has one, i am curious what they are, made it a pita to get the passenger axel in.
Title: Mysterious metal block underneath engine
Post by: 8v-of-fury on October 27, 2008, 03:13:58 pm
my 91 golf donor car has this as well.. I like the idea of not having to move it over when i do the gas->diesel swap i am planning. :P