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

[Lewis, Gary M]

Scott, 
I don't think your logic applies to my situation.  I haven't got a "Mongosized"(SJMtm) turbo charger.  It is smaller than the K26#6 turbine/K27 compressor hybrid. Far smaller than the K26#8/Garrett stuff.  In fact, I have something much more like the RS2 modified cold side, mated to a K26#6 turbine, from 1986tq fame.  I interpret what you just said as my cold side compressor and housing is good for 480+ hp.  Nice, I never knew...

What I do have is a solution to the RS2 that is a total bolt-on (a requirement I wanted), bullet-proof KKK reliability, with a very modern compressor, for $950, that loses a bit on the bottom end, and gains a bit on the top end.  I couldn't get ANYBODY to sell me an RS2.  Turns out I am deliriously happy I couldn't get one.  

In other words, I got 200 rpm back from the install of the BPV, and I have no surge (Thanks Pizzo and Hap).  And I haven't even optimized it yet, using Hap's, and Pizzo's, and Trevor's suggestions.

I must say that I completely and utterly do not understand how increasing pressure losses will get me 26 psi at 3,000 rpm.  I apologize for my ignorance, but simply stated, if I'm experiencing say a 5 psi pressure loss between the air filter and the intake manifold, cutting that to say 2 psi thru improvements of BPV, IC, wastegate, RAIS, etc, I gain 3 psi, which is the equivalent of my turbo running 28 psi to make 26 psi, as opposed to 31 psi to make 26 psi.  Call it a 10% improvement.  I'll bet money there is 2 psi loss at the stock IC alone at 26 psi.  

I have re-read your sentence (more than once), and are you suggesting that pressure losses will increase more at part throttle as opposed to full throttle?   I don't understand how, but in my case (sea level, I run full boost or like a kitten, rarely in between), I'm not concerned.

On the altitude thing, I drive lightly when I am in Mammoth.  You trained me a long time ago on the altitude thing.

Now someone reading all this could easily postulate that "If I'm going to make all these improvements, why not just get an RS2 turbo in the first place?"  Great question.  I haven't got an RS2 turbo, and would rather spend the remaining $1,000 I saved on my turbo making pressure loss improvements.  Also, assuming I'm correct, and improving pressure losses net improved rpm/boost thresholds (as Hap's and others experience with the FMIC and 400 rpm boost improvements empirically suggest), imagine what can be gained with the smaller turbos.

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: QSHIPQ at aol.com [mailto:QSHIPQ at aol.com] 
> Sent: Tuesday, December 23, 2003 5:36 AM
> To: mik at info.fundp.ac.be; Lewis, Gary M; s-car-list at audifans.com
> Subject: Re: [s-cars] Bypass Valves and Pressure Losses (Uh, Pizzo??)
> 
> 
> I agree Minhea.  Look guys, if you are looking for 26psi on 
> the I5, the RS2 
> will hit it.  If you are looking for Flow at 26psi for xxxhp, 
> the RS2 (modified 
> cold side) can hit it (I say up to about 480 or so - 
> Minhea?).  If you are 
> looking for 26psi at low RPM's on a 2.3L motor, I can't think 
> of a better turbo 
> for the task (well I can think of one, but Herr Meyer gets a 
> lot of money for 
> it).  If you take a big turbine and try to get it to do big 
> things with a 
> small motor, you will hit the surge line very quickly.  Surge sucks.
> 
> Someone really (hey let's get Mikey) should put a couple of 
> these mongosized 
> turbo hybrids on a turbo dyno.  Chassis dynos only give part 
> of the story, as 
> several here are finding out.  I'm intrigued by solving turbo 
> problems with 
> bypass valves.  In fact Gary, using this logic, you are 
> actually going to 
> 'increase' pressure losses to get 26psi at 3k.  Part throttle 
> may just require 
> bleeding of boost as several here will find out.  Especially 
> at altitude, these 
> problems are going to get worse, cuz the turbo is spinning 
> faster to attain the 
> same pressure ratio, which means a bigger problem at part throttle.
> 
> IMO, you are going to see dual sequential turbos (already 
> here) and modified 
> scroll design (already here) as alternatives to one monster 
> turbo trying to be 
> both a lamb and a lion.
> 
> My .02 arbitraged thru the peso
> 
> Scott Justusson
> QSHIPQ Performance Tuning
> 
> 
> 
> 
> 
> In a message dated 12/22/2003 1:52:22 PM Central Standard Time, 
> mik at info.fundp.ac.be writes:
> 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
>