Exhaust ... OMG! What have I done?

[Drumster]

My new FlowMaster muffler and partial 2.5" exhaust was installed Wednesday. There was a bit of an issue at first with the rear hanger being too loose and shaking like crazy; but that's been corrected.

Took the van down to Blaine this morning and yes, it is a bit louder which I expected and that's no big deal. The problem is the engine has developed an ugly vibration; a sort of "buzz" at highway speeds. Kind of like an inline four cylinder motorcycle. I feel it through steering wheel, pedals, everything. The whole van now has a distinct and very annoying buzz. I'm wondering if it has something to do with the overall increase in mass of the new exhaust parts.

(I'm thinking I shoulda' just left well enough alone.)

Any thoughts?

[psilosin]

I'm wondering if it has something to do with the overall increase in mass of the new exhaust parts.

No that would not be the issue.

Sounds like bad luck in that either your new muffler and/or piping is developing a nice massive harmonic vibration at a certain rpm (which happens to be your highway cruisin' rpm) that isn't dampened by your hangers and is transferred throughout the vehicle.

Maybe try a different muffler. On a turbo vehicle the turbo absorbs so much of the noise that even straight piping without any muffler doesn't sound 'that' loud so a simple cheap glasspack cherry bomb type muffler will leave you legal with a nice tractor rumble and a nice turbo whistle.

[Feds]

Sounds like a job for Science:

Grab some hose clamps and a piece of flat bar. Strap the flat bar to a straight piece of exhaust, and see if it damps out the vibrations. That should determine if it's a mass problem.

There's a possibility that it's an interference: the exhaust is touching something as it heats up, and gets under load. Look at spots where the exhaust is close to the chassis. chalk the potential interferences, drive, see if the chalk is rubbed off anywhere.

Other option is a frequency resonance. in this case, stick another foot of pipe on the end of the exhaust, see if the vibration goes away.

[tonydca]

Vibrational issues aside, are you noticing any performance improvement with the new exhaust system?

[Drumster]

Vibrational issues aside, are you noticing any performance improvement with the new exhaust system?

It's pretty difficult to say. Because I'm kind of expecting a bit more, and want to have more; I could be perceiving a bit more. Lack of power has never been an issue really and now that it's a bit louder and kind of 'buzzy-er", my attention is drawn to those two phenomenon more than anything else.
Having said all that, there could actually be a bit more jump.

[Drumster]

Sounds like a job for Science:

Grab some hose clamps and a piece of flat bar. Strap the flat bar to a straight piece of exhaust, and see if it damps out the vibrations. That should determine if it's a mass problem.

There's a possibility that it's an interference: the exhaust is touching something as it heats up, and gets under load. Look at spots where the exhaust is close to the chassis. chalk the potential interferences, drive, see if the chalk is rubbed off anywhere.

Other option is a frequency resonance. in this case, stick another foot of pipe on the end of the exhaust, see if the vibration goes away.

Nothing is contacting of even close to the chassis; it's all very similar to stock and employs stock mounting tabs & rubber etc.
I think I'll start by going back to Gary & seeing what he has to say. I'd rather not venture into too much guess work or purchasing more mufflers etc. until he's had a chance to chime in. I will pass these suggestions on to him though and if a glass pack or whatever seems like a good idea to him, then I'll give it a whirl. He's been in the muffler/exhaust biz for many years and has a good grasp of the subject.

Thanks all of you for your comments.

[legionnair]

You could get some muffler wrap and cover the muffler to quiet it down

[LeeHammy]

Well if you want more you have to not just tune up your exhause like you did but the intake too. If you are stull running a stock air box and filter you may want to upgrade to a K&N to get the most out of the system. Air out will only be as good as air in.

[doodah]

Yikes!! I was thinking of upgrading my exhaust system also...now having second thoughts.

The harmonics idea sounds like the likely culprit though....

And I think I will do the upgrade.... Where's the best place for an Delica exhaust installation?

[doodah]

K&N, Amsoil and other serviceable foam&oil based filters do not filter 100% particles as efficient as a stock paper filter. Tests all over the internet and shops show this.

K&N type filters fare poorly in the summer and dry months when dust and dirt particles are everywhere. They do a worse job at filtering than a stock paper filter.

http://www.bobistheoilguy.com/airfilter/airtest3.htm

I would not use a K&N filter on my vehicle as a stand alone filter. Either a 2-stage filter (K&N + paper) or use K&N in the wet months and paper in the dry months.

Either way, changing the air filter does not affect the exhaust system.

[rezdiver]

x10 on not needing the K&N. K&N may provide more flow if you were running a naturally aspirated engine or have played with your injector pump to increase fuel flow.
this is not a performance vehicle. and you are running a turbo that generates huge amounts of air, there is more than ample air flow for your engine.
the larger exhaust may improve your performance ever slightly without fueling mods, but the major benifit is less restriction to provide the exhaust gasses an easy way out letting your engine run cooler.

[Drumster]

The problem here is not the K&N Apollo air filter I've had on for about two years and which, I discovered recently, does let a fair bit of dust through. But that's a different topic. This thread... http://www.delica.ca/forum/kn-apollo-ai ... 13133.html ... is about the K&N.

Back on point, the minor muffler/exhaust vibration I'm experiencing has nothing to do with that filter but seems very likely, as has been suggested, to have something to do with balance, mass and harmonic vibrations. Something has been thrown slightly off, as far as I can tell. I said "minor" and "slightly" just now because on Sunday we ran out Hwy 1 and in to Hayward Lake for a picnic and the problem was much less pronounced than a few days earlier. No idea why.

[Drumster]

I think it may have something to do with this...



Only the bottom right corner has been welded so there's much less contact between muffler & hanger than there was originally. Whole thing is that much less solid and therefore flexes more; same sort of principle as a tuning fork.

I think these vehicles were well designed enough so that the optimum amount of flex was built in. Alter too much one way or the other and unwanted vibrations & frequencies show up. I don't know for sure but that makes sense to me.

[Mr. Flibble]

Try putting a small clamp on that spot, see if there is any change. If so, get the weld changed.

[RichD]

Same thing happened to me with my L400, and I believe we might have used the same shop.

Take it back. They fixed mine and they'll fix yours too.

Edit: for the record, L400's NEED a flex pipe.