1997 Passat, What is the block under Exhaust down pipe

[mrorganic77]

I hope that some one can tell me why there is a solid metal block bolted to frame under the back side of the engine approximately where the exhaust down pipe is. Why is it there, what is it's purpose? The block is quite heavy and attached by four bolts. The dimensions are about 5 5/16" X 4" X 2".

I have noticed it there several times when changing oil but yesterday i had to remove it, to get to the exhaust down pipe, it is attached by only four bolts and does not appear to do any thing or touch any thing else.

 

[Lug_Nut]

It's a 'tuned mass' that is intended to shake at a different frequency than the cross member. It is supposed to eliminate a vibration at some specific rpm that caused a harmonic tone.
I removed mine on all my B4s (when they were in the way) and noticed no difference when I 'forgot' to reinstall them.

 

[GTiTDi]

What he said^! I have removed the block from every FWD VW I have owned...I figured it would improve the weight bias a tad!

 

[mrorganic77]

Thanks Now i will just leave mine off as i could always replace it if i feel some vibration that I feel would warrant replacing it. No use carrying that bit of extra weight every where the car goes.

 

[Digital Corpus]

I know the common belief or feeling is that it doesn't really serve much of a purpose. I noticed a harmonic difference with mine off. The car had a noticeable vibration in the cabin and was louder as I approached and went past ~2750. It wasn't a bad thing, or something like a loose bolt. just like a the vibration motor in a cell phone, but with the whole car. Easy to not feel or heard, but it was evidently present.

A friend's B4V has some vibrations that get kinda bad at 4K. I noticed the same harmonic in my B4 while I had mine off, but at a lower amplitude. I also don't have such a heavily modified engine.

 

[Technician!]

Leave 'em on. It picks up a frequency that will get sent to some other "distal" component instead....maybe one that could fracture in time.
As a test tech at VW engineering ( a long time ago!) we were getting a disturbing frequency of vibration at idle (imagine that!!!) in the "new" body style Rabbits for '81.
If a door was left open, or ajar...the problem went away!! You could see the door reacting. Engineering's fix was the
vibration dampner that you find bolted inside the front bumpers of those models.
At first I thought it was just a band-aid type of fix (like GM always used), but later came to realize that it was a problem that you could chase all over the vehicle, and possibly never eliminate...causing necessary suspended components to fail later.

 

[Vince Waldon]

Of course it's the owner's choice what they leave on the vehicle and what they remove...but I always start by asking myself: given the narrow price margins on cars in general, and the fact that, as Kettering used to say, "parts left out cost nothing and cause few service issues" *every* part on the car probably had a reasonably important purpose in the eyes of the teams that designed it... else they would have left it off in the first place.

If you read up on the Corvair most historians agree the original design instability was due to the removal of a $5 rear suspension part, in an effort to shave a few bucks per car off the design.

 

[compu_85]

I think Matt98AHU noticed a difference on his VR6 swap, I'll let him chime in.

-J

 

[schultp]

Of course it's the owner's choice what they leave on the vehicle and what they remove...but I always start by asking myself: given the narrow price margins on cars in general, and the fact that, as Kettering used to say, "parts left out cost nothing and cause few service issues" *every* part on the car probably had a reasonably important purpose in the eyes of the teams that designed it... else they would have left it off in the first place.

If you read up on the Corvair most historians agree the original design instability was due to the removal of a $5 rear suspension part, in an effort to shave a few bucks per car off the design.

Vince, I agree with your philosophy. I too tend to keep my vehicles close to stock set up.

 

[chrisvb]

just got rid of the throttle "shockabsorber" that makes the engine race when shifting (manual) cant think of any good reason for it being there in the first place.

 

[Vince Waldon]

OK, *that* I ditched in a heartbeat.