quattro digest, Vol 1 #3468 - 16 msgs

[Larry C Leung]

Suitable shims for wastegates that won't bind (only matters if you are
tightening the allen screw) are
shims for Bottom Bracket cups or freewheels (those are becoming
increasingly rare and bicycle mechanics
that are younger than 30 may not know what you are speaking about) from a
bicycle shop are quite suitable
and cheap. Due to metallurgy issues, I'd actually opt for steel rather
than the aluminum spacers when
possible, or galvanic action may eat away (fortunately) the spacer. BTDT
(the spacer thing, not the galvanic
action part)

Good luck,

LL - NY




> Date: Tue, 28 May 2002 10:26:23 -0700
> From: Ken <auditude at get.net>
> To: quattro at audifans.com
> Subject: regulator-based MBC for 5kcstq, 15psi [long]
>
> I changed my '88 5kcstq over from WGFV operation of the WG to what's
> been c=
> alled the "Timmerman Mod".  It's basically a pneumatic manual boost
> control=
> ler.
>
> As some or most of you know, this puts regulated boost pressure on
> the uppe=
> r chamber of the wastegate.  This allows for the wastegate to remain
> closed=
>  until the boost pressure on the bottom WG chamber exceeds the
> regulated pr=
> essure at the top.
>
> My attempt at understanding how this works, is that below the
> pressure the =
> regulator is set at, pressure is equalized on both sides of the WG
> diaphrag=
> m, and the wastegate is held closed by spring pressure.
>
> Then, as the lower wastegate pressure rises above the pressure in
> the upper=
>  chamber, the WG will remain closed until the pressure differential
> exceeds=
>  that which the WG spring will hold.  So, let's say my WG spring is
> suppose=
> d to be a 1.8 bar spring.  So, with my car set at 15psi, that means
> that th=
> e WG spring is providing about 12psi of boost, and the regulator mod
> is pro=
> viding the extra 3psi, by providing a regulated 3psi to the top of
> the wast=
> egate chamber.
>
> The regulator is one of the cheap ones you can get at Sears or Home
> Depot. =
>  I'm running the Home Depot version, which is a Campbell
> Hausfield(sp?), an=
> d cost under $20.  That, some hose and clamps, and a "T" fitting was
> all it=
>  took.  The regulator is located behind the firewall in the cowl
> area.
>
> My car is fairly quick at 15psi.  While dialing it in at the high
> side, I t=
> hink I may have heard some knock, which caused me to get my foot off
> the pe=
> dal quickly of course.  What I basically heard wasn't what I
> thought/expect=
> ed  knock to sound like (diesel rattling type sound), but did sound
> like so=
> me kind of "new" metal-parts-doing-something noise that I've never
> heard be=
> fore.  I have it dialed back to where that noise doesn't happen.  I
> would l=
> ike to have a wideband 02 sensor setup, fer sure.
>
> Of course, this is a very simplified boost control setup, and my TAP
> ECU is=
>  not in control of boost pressure anymore, if it even was before.
> Not that=
>  it was much with the 1.8 bar spring installed.
>
> I'm considering swapping back in the stock WG spring, since I can
> control b=
> oost with the regulator, and it may help WG responsiveness at the
> set boost=
>  level.  I don't know if this would be better, but it seems like it
> would.
>
> I was originally collecting parts to convert a WG cap over to
> adjustable st=
> yle, so I could get some of the boost I had when I blew the lower WG
> hose. =
>  But then I read that it wouldn't increase max boost, just the WG
> cracking =
> pressure.  That makes sense.  I may still do the mod, just to be
> able to tw=
> eak things.
>
> Btw, if you take out the WG allen bolt from the underside, you can
> just pus=
> h out the plug, you don't need to drill a hole and pull on a screw
> or anyth=
> ing.
>
> Where can I get the valve spring shim washers that are recommended
> as WG sp=
> ring seats, so that the spring doesn't bind when adjusting the
> preload?
>
> A word of warning to others who may be wanting to cryogenically
> treat parts=
> , I think the process made the WG diaphragm brittle and possible
> cracked it=
> .  It was all stiff and torn, and I would have remembered if it was
> that wa=
> y when I bought the donor car.  I actually couldn't get the WG to
> fully sea=
> l, which I think was the diaphragm being stiff.  Luckily I have a
> couple re=
> placements now.  A cheaper way would be to take out the diaphragm
> before tr=
> eatment.
>
> Anyway, for those of you who fully understand, can, and are willing
> to, swi=
> tch to manual boost control, I recommend the mod.  It's a cheap mod
> that co=
> uld be used to bring the boost up to just below the fuel pump cutoff
> at 1.5=
>  bar, for a little extra boost.  Unlike a lower WG chamber bleeder
> type of =
> a setup, it's a closed system so metered and boosted air isn't let
> out, whi=
> ch seems better.
>
> Thanks to Ben Swann for the "Boostin'" webpage compilation, to Paul
> Timmerm=
> an for the idea, and to the lower WG hose that blew to show me the
> extra po=
> wer potential.
>
> Now, I'm interested in single-pass intercooler options, and need to
> install=
>  a bypass valve before something becomes its own blowoff valve.
>
> Let me know if there are any questions.
>
> Later,
>
> Ken
>