Re: Re: RE: Re: Help!! Get rid of the Z-tube??

From: Canucker Trucker (mal5@ualberta.net)
Date: Wed Jul 03 2002 - 12:43:40 EDT


>From what I can gather from all the posts is that the problem may be caused
by the TB alone:
1) Steve has the Z-tube only - no problems
2) Someone said they have an F&B TB - no problems
3) You have the problem with the stock airhat and the Fastman TB as well as
with the Z-tube
4) You mentioned Fastman has had this problem in the past ...

(thanks Dr. Watson)

So here's my theory: It **MAY** be caused by a phenomenon call 'vortex
shedding.' Basically, as air passes over an abrupt edge, the boundary layer
will 'stick' to the edge for as long as it can, until finally releasing
(like an elastic band breaking). When the boundary layer lets go (or the
'elastic breaks'), it creates a vortex which vibrates the edge it was shed
from ... At a particular wind velocity, the vortex shedding occurs at a
particular frequency ... if this frequency happens to be close to the
natural frequency of your engine or the TB mounts or something, it will
vibrate the hell outta it. ... so basically, the air velocity going through
the TB @ 2400RPM causes vortices to be shed at the same frequency needed to
shake the engine ... This phenomenon is the cause of the Tacoma Narrows (I
think?) Bridge collapse (but in that case the wind passing over the guy
wires caused vortex shedding at the same frequency as the wires ... like a
guitar string)

This phenomenon can also be seen on most radio antennae as you drive down
the highway ... ANYWAYS,

So how do you fix it? --- disrupt the air flow where the vortex shedding
occurs ... i.e. at the TB.

To get around the problem of the antenna ripping off as you drive down the
highway, DC wrapped a thin wire around the length of the antenna (take a
look at it next time you're at your truck)...this disrupts the airflow
around the antenna and reduces the size of the vorticies being shed. ...
you'll want to do something similar to your TB:

You could try dremelling off any sharp edges that were left in the TB after
fabrication ... check the bore and the butterfly plate ... maybe round the
edges of the butterfly plate ... any sharp edge that the air might get
'caught up on' is a potential culprit .... it's tough to say what would
cause it without looking at it ... OR just before the air enters the TB, you
could make some kind of flow disrupter like you were planning. Maybe just
some vertical fins in the Z-Tube. The key there would be to get the
disrupter as close to the TB as humanly possible.

Like Bernd said though, it's nothing harmful to the engine ... it may wear
some fasteners out or your throttle cable eventually, but who knows?

sorry for the length of my essay :) hope it makes sense.

--
Canuck
--------------------------------------------
Y2K 4.7L 2wd 5spd

""crm"" <tb.crm@verizon.net> wrote in message news:007e01c222ab$e6f3e210$7c6445a1@vatican2... > > Steven, the vibration is felt in the gas pedal. it occurs when i accelerate > enough to where it would shift at about 2800-3000rpm. starts at about 2400 > though. > > it didnt happen when i had just the Z-tube on there though. i only noticed > it after the Fastman TB. i had been told it was because of the lack of a > resonator from the stock airhat and it appears to have been amplified by all > the extra air flowing thru the new TB. so last night i went back to the > stock setup with the exception of the TB. still had the vibration. Bernd and > Dan Arcand both said it was nothing dangerous for the engine, but i'll still > see if i can fix it with the little vortex wing thingie inside the tube that > they told me how to make. > > other than that, the truck really seems to be liking the mods i've added. > i've got about 175 miles on it since the TB swap and PCM reset and i can > definitely tell a difference in performance. i'll prolly drive it another > week and then take it back to the dyno to tell for sure. and then i'll have > another baseline prior to the cams and intake install. > > -adam > > ----- Original Message ----- > From: "Stlaurent Mr Steven" <STLAURENTS@MCTSSA.USMC.MIL> > To: <dakota-truck@dakota-truck.net> > Sent: Wednesday, July 03, 2002 10:26 AM > Subject: DML: RE: Re: Help!! Get rid of the Z-tube?? > > > > > > When I installed the Z-tube I never did experienced this problem. > > > > Where is the vibration occurring and what RPM range is the resonation or > > vibration is being felt, Adam? > > > > -------------------------------------- > > Steven St.Laurent > > C4i System Engineer > > C4i Engineering Branch, PSD, MCTSSA > > MARCORSYSCOM, U.S. Marine Corps > > Office (760) 725-2506 (DSN Prefix: 365) > > "Never be content with somebody else definition > > of you. Instead, define yourself by your own beliefs, > > your own truths, your own understanding of who > > you are. Never be content until you are happy with > > the unique person GOD has created you to be." > > > > -----Original Message----- > > From: crm [mailto:tb.crm@verizon.net] > > Sent: Wednesday, July 03, 2002 7:51 AM > > To: dakota-truck@dakota-truck.net > > Subject: DML: Re: Help!! Get rid of the Z-tube?? > > > > > > just to let you guys know, i installed the stock intake last night and > still > > had the vibration. so it's either always been there and i never looked for > > it and therefore didnt notice it. or, it's all the extra airflow from the > > TB, which in one sense is cool since it's obviously flowing more. > > > > either way, i am keeping both the Z-tube and the new TB. i bought some > stuff > > last night to make a little vortex wing (or whatever it should be called) > > inside the tube so i might get to that this weekend. and even if it doesnt > > completely fix it, i'll not worry about it... > > > > thanks to all who offered suggestions! > > > > -adam > > > > ----- Original Message ----- > > From: "Bernd D. Ratsch" <bernd@texas.net> > > To: <dakota-truck@dakota-truck.net> > > Sent: Wednesday, July 03, 2002 12:04 AM > > Subject: DML: RE: RE: Help!! Get rid of the Z-tube?? > > > > > > > > > > The vibration is not due to the intake or throttle body...but rather a > > > resonance from the intake plenum. If you look at the factory airbox (on > > > the TB)...you'll notice a resonance chamber (or two depending on year) > > > which cut the noise to a minimum (if not completely). > > > > > > - Bernd > > > > > > -----Original Message----- > > > From: owner-dakota-truck@dakota-truck.net > > > [mailto:owner-dakota-truck@dakota-truck.net] On Behalf Of Ronald Wong > > > Sent: Tuesday, July 02, 2002 6:03 PM > > > To: dakota-truck@dakota-truck.net > > > Subject: DML: RE: Help!! Get rid of the Z-tube?? > > > > > > > > > > > > I have no problems with a K&N FIPK but then I have an F&B TB instead of > > > a Fastman. I don't know what the differences are but I know there's no > > > vibration. The only time I've ever had a vibration problem was one of > > > my headers being too close to the transmission case. > > > > > > Ron > > > 00 PB SLT QC 4X2 5.9 46RE 3.92 LSD > > > For modifications see my DML Profile (URL follows) > > > http://www.twistedbits.net/WWWProfile/dakota/Kw9pV1EkFeOYY > > > > > > > > > -----Original Message----- > > > From: owner-dakota-truck@dakota-truck.net > > > [mailto:owner-dakota-truck@dakota-truck.net]On Behalf Of crm > > > Sent: Tuesday, July 02, 2002 11:38 AM > > > To: dakota-truck@dakota-truck.net > > > Subject: DML: Help!! Get rid of the Z-tube?? > > > > > > > > > > > > hey guys, i have quite a quandry on my hands. i am having the gas pedal > > > vibration problem that some seem to get after installing an intake and > > > new/ported TB. it's serious enough to where i know it should be fixed, > > > but i am not sure how i wanna fix it. > > > > > > i feel fairly confident that the problem can be resolved by going back > > > to the stock airhat that has the resonator on it, but that would mean > > > getitng rid of my Z-tube. the dyno doesnt lie, and i know it helped out > > > in the power. but, i know i want to keep the Fastman TB, so that means > > > finding a fix somewhere else. > > > > > > Dan (the Fastman) suggested putting a little piece of sheet metal in the > > > Z-tube perpendicular to the TB butterfly to help create some turbulence > > > and help cancel/dampen the harmonics to where the vibration lessens. > > > however, he said he cant guarantee that it would completely resolve the > > > vibration. his idea was similar to what Bernd posted a while back. > > > > > > my other options would be to send back the Z-tube and exchange it for a > > > Stage II. or, i could go back to the stock setup with a drop-in K&N, > > > minus that oddly directed airhorn and a larger opening in the front of > > > the airbox. > > > > > > so help me out PLZ! i wanna make the best decision that will produce the > > > most power while at the same time getting rid of the vibration. i only > > > have a couple days left to my 30 days on the Z-tube and i'm definitely > > > keeping the TB. any help would be greatly appreciated. > > > > > > -adam > > > > > > > > > > > > >



This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:05:00 EDT