[s-cars] Bypass Valves and Pressure Losses (Uh, Pizzo??)

Mon Dec 22 15:31:58 EST 2003

Well, after tuning K26/27/29-equipped S2s and RS2s, with either #6 and #8 
hot sides, I think my next turbo will be an RS2 hot side (BTW, that one 
isn't the smallest #6 hot side, the smallest one is the one used on oil 
cooled K26s, 50mm exducer bore vs. 54 on the RS2 turbo) bolted on a K27/29 
cold side (which means a K29 compressor wheel in a machined K27 cold side 
housing), running a 360 degree thrust bearing. This way, I should get 
pretty close to what the "best of both worlds" means for me, i.e. good low 
RPM performance and close to 420 HP at the top end. I still have to work on 
the K29 compressor map to figure how much boost it can take at low RPMs 
without surging but the thing should go like mad above 3k RPMs.

I love the way the #8 K26 hot side hits you at 4.2k RPM (no way it can do 
anything interesting below that) but that's just a bit too high for a car 
that should be still driven on the street IMO... the point (as you said it 
too) is that everyone has different driving styles and preferences so what 
suits one probably won't suit someone else...

Cheers,

Mihnea

At 12:20 22/12/2003 -0800, Lewis, Gary M wrote:
>Agreed Mihnea.
>
>The REAL RS2 turbo is limited by the turbine side wheel being the smallest 
>of the K26 line.  I don't have that limitation, and I also have a much 
>larger compressor wheel and housing.  I have a 600RPM penalty vs. the Rs2, 
>but I also have the rpm range above 3,200 in performance.  I understood 
>the trade-off vs. a $1,000 premium for the RS2, and I took the custom 
>K26.  I have no regrets.
>
>My suggestion?  If someone is into high-performance at low rpm, go with 
>the RS2.  If you want all out performance above 3,000 rpm, check out some 
>of the other turbo's available (Custom K26's/K27's or Garretts').
>
>I have all the parts to build a psuedo RS2 comp, but I don't think I'm 
>going to.  I'm having too much fun with the turbo I have.
>
>Thanks,
>
>Gary Lewis
>
>1995.5 S6 Avant, Green/Ecru, RS2 MAF, RS2 Exhaust Manifold, RS2 Injectors, 
>Custom Turbo (K26 Turbine, Factory K26 Cold side (Audi Works '999' P/N) 
>with 50mm intake and custom Innovative Turbo compressor wheel), TurboXS 
>Type 25 Bypass Valve, Bilsteins, Eibachs, Big Reds, Spec II Clutch.
>
>
>
>
>
> > -----Original Message-----
> > From: Mihnea Cotet [mailto:mik at info.fundp.ac.be]
> > Sent: Monday, December 22, 2003 12:51 PM
> > To: Lewis, Gary M; s-car-list at audifans.com
> > Subject: RE: [s-cars] Bypass Valves and Pressure Losses (Uh, Pizzo??)
> >
> >
> > Gary,
> >
> >
> > If you had had a real RS2 turbo (I know the turbo itself is way too
> > expensive, I know!), you could have gotten 26 psi at 2.6k in
> > 4th gear while
> > accelerating WOT from 2k RPM.
> >
> > Just my 0.02 Euros worth of 20vt engines tuning,
> >
> > Mihnea
> >
> > At 11:43 22/12/2003 -0800, Lewis, Gary M wrote:
> > >Hi Hap,
> > >
> > >I oriented it from the bottom (pressure side), as the instructions
> > >indicated, with 6 shims, as Pizzo indicated.  It works far
> > better than the
> > >old 710N unit from a pressure loss standpoint (I gained 200
> > rpm in 4th
> > >gear).  My current automotive goal in life is to reduce
> > pressure losses in
> > >hope of getting 26 psi at 3,000 rpm.  I'm making progress.
> > >
> > >I think the idea you postulate is really a neat one.  It
> > should provide
> > >far better response than a shimmed-to-the-max BPV.  Uses vaccuum
> > >primarily, not pressure and vaccum to open the valve.  I will try it.
> > >
> > >Sorry I took so long to answer, but I needed to think about
> > this for a
> > >few
> > >days.
> > >
> > >That Trevor is something else, ain't he?  The more I talk to him
> > >(virtually of course), the more I want to drive his car.  No
> > to mention
> > >your of course...
> > >
> > >Thanks Again,
> > >Gary Lewis
> > >
> > >1995.5 S6 Avant, Green/Ecru, RS2 MAF, RS2 Exhaust Manifold, RS2
> > >Injectors,
> > >Custom Turbo (K26 Turbine, Factory K26 Cold side (Audi Works
> > '999' P/N)
> > >with 50mm intake and custom Innovative Turbo compressor
> > wheel), TurboXS
> > >Type 25 Bypass Valve, Bilsteins, Eibachs, Big Reds, Spec II Clutch.
> > >
> > >         -----Original Message-----
> > >         From: CaptMagu at aol.com [mailto:CaptMagu at aol.com]
> > >         Sent: Thursday, December 18, 2003 1:23 PM
> > >         To: Lewis, Gary M; s-car-list at audifans.com
> > >         Subject: Re: [s-cars] Bypass Valves and Pressure
> > Losses (Uh,
> > > Pizzo??)
> > >
> > >
> > >         Gary
> > >
> > >         I have the H34 TurboXS right now. Do you have it
> > plumbed from
> > > the
> > > side? In other words is the pressure feed from the turbo
> > plumbed into the
> > > side of the piston. If not you'll want to reorient it this
> > way and then
> > > you won't need any washers. In fact I went to a
> > softer/shorter spring. I
> > > had shimmed my old H34 like crazy, well beyond the provided
> > washers and
> > > was still having a problem getting it to hold boost. I
> > talked directly to
> > > the TurboXS folks a while back when there was a thread running on
> > > mounting BPVs backwards. They admitted that for high hp
> > applications that
> > > this was the way to go and sent me a brand new H34
> > configured for a hard
> > > mount at the side. Tha's what I have now but even with the
> > softer/shorter
> > > spring I'm still getting that boost surge at throttle lift
> > from boosted
> > > runs. It was Trevor Frank's idea to try a softer spring and it has
> > > greatly improved the problem but has not totally fixed it.
> > My next try is
> > > a beefier diaphram unit. The stock Mitsu EVO BPV couldn't
> > hold my turbo's
> > > force.
> > >
> > >         Hap, boostin and surgin in Everboost, Maguire
> > >
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> >
> >