RE: 5ktq Mods - Math vs Claims - long

[QSHIPQ@aol.com]

In a message dated 97-10-25 02:31:47 EDT, Scott & S.O.c.(>) banter:
... (deleted)

 >Let me just   say this though, what I have in the car now
 >will outrun just about any 
 > other MC engine around. Especially any of the "Rs2"
 >wannabe's.........  
 > Even Ned is damned impressed.
 
 Great, it is about time someone around here gets to drive a
 fast Audi. 
 
 > Well chippendude......... I know for a fact what is being
 >done in my box 
 > is much more extensive than your Qlcc chip (which I do
 >belive you 
 > sell....)  
 
 Well, actually my tag line was/is CHIPDIPPINDUDE, I know it
 is hard
 to remember, < ... >
 
 >Does your mod provide over 16psi of boost in FIRST gear
> with 
 > no brake torquing? 2nd through 5th gear gives 26psi of
 >boost.  
 
 No, of course not, as stated above, but then I didn't
 realize I entered into
 a contest of "mine is bigger than yours"
 
 >And yes I   have the fuel to support that boost as
 >evidenced by my Exhaust Gas Temp 
 > readings of 1325F peak temp.  We did more than just raise
 >the boost limit.  >>>>>>>>>>>>>>>>>>>>>>>>>>

With tongue in cheek, Scott M., you are much more patient than some of the
rest of us.   Re: the supercalafragilistic chip extraordinaire:
 "Forgetaboutit" - Donnie Brasco.   What the S.O.c. is describing above has
NOTHING to do with the chip, everything to do with the turbo and wastegate.
  A couple of claims made are really interesting.  First, 16psi in first gear
is NOT a chip or computer mod or turbo mod, it's a WG spring issue (baseline
and preload), of which many on this list have some of the best.  A rock bone
 stock k26 turbo with stage II mod will reach a 2.1PR (that's 16psi
corrected) faster than a larger turbo (self proclaimed) near it's Surge Line
(see below, defined by most experts as <60% Compressor Efficiency), so that
"claim" has no basis or warrant, nor is it chip related (see Popping
Wastegates post - archives).  Assuming 16psi in first to be a "good" (?)
thing, an enormous bypass valve is necessary, the pressure spike is gonna be
ugly.  2)  Since a 26psi boost level is 2.8 bar in St Louis, I wonder, how is
that at all "chip" controlled with a 2.5 bar Pressure Transducer?  3)  Claims
of bigger better and faster are no different than Ross' were a couple months
ago.  Whether S.O.c. claims it, or Randall butt-benchmarks it, it's still a
claim.  Calibrating these to some instrument would suffice, no expounding on
mods necessary.  4)  Ned was impressed with WHAT exactly?  His own "RSR"
turbo?   5)How does one know an RS2 is a "wannabee" anything.  "...RSR, a Ned
Ritchie turbo, blows the RS2 into the weeds."  - quoting archives.  Well, I'm
game, let me expound on just the claims made.  Ah yes, here's a Mr. Turbo hat
(tipped to you Mr. Head, for the lead:).

CLAIMS:
*  16 psi first gear (see above)
*  26psi 2nd thru 5th
*  EGT = 1325

How bout some turbo math to put this in perspective, given just the 2nd one
above.  Some math deleted for summary, certainly available.

if PR = Po + Pb/Po, then by definition,  26psi in St. Louis is a PR of 14.5 +
26/14.5 = 2.79 PR (pretty high for a 2.5 PT) 

Baseline N/A motor airflow for a 134ci (MC) engine at 85% VE = 184 CFM
Claimed 2.79PR, by math means:
184CFM * 2.79 = 513.36 CFM @ 5500  (26/27 hybrid @ ??  efficiency @5500)

Compare, say the RS2 turbo
184CFM * 2.50 = 460 CFM (Stock RS2 @ 72+% efficiency @ 5500)

Ok, and the stage II mods (assuming 2.0bar)
184CFM * 2.00 = 368 CFM

Assuming one WANTS ONLY 513 CFM a cold side change of a stock RS2 unit is
easily done, btdt X a few, and at a much lower PR, and with a better surge
line, specifically, with a higher Compressor efficiency.  So, by math AND
btdt,  this "wannabee" is smiling some.

Assuming all that 513cfm is all going into the 10vt motor at a reasonable
density ratio, might be optimistic.  Especially if the claimant is using a
K27 based cold side, no engine mods.  Dave and Dave could prolly extrapolate
what runner and valve size might be needed for this to happen.  I argue that
the WG is doing more of the work than is necessary in this case.  Since there
is no Computer control of boost function beyond 2.5, chances are really good
that 2.79 is the measured spring limit for the WG as configured (baseline and
preload), and it just opens after that.  In fact, by the very claims made, I
can clarify the statement "we did more than just raise the boost limit", in
fact by definition,  it was eliminated all together. Take that a step
further, a different spring could get 3.0PR the same way (hey that would be
30psi!!!), and safer, especially if a 1.9bar spring is preloaded to 2.8, the
WG can't open to the full range of the valve (danger danger).   WG control
has nothing to do with any "top secret" computer mods, or "RSR" turbos.  Or
more... or better...  or faster...   IN fact, read on...

A more interesting operation of physics applies to the PR vs Compressor
Discharge temps.  If one takes a 2.79 PR we can see that at a 72% compressor
efficiency (that's another B.O.D. assumption of a high number), the discharge
temps would be  ~375 degrees (less than 72%CE it immediately exceeds 400
degrees) (for the detailed and really nerdy calculations , see Dave, Dave et.
al. - archives)  At 2.50PR @ 72% efficiency, ~315 degrees.  Let's work on
these numbers a little to get t-body inlet temps.

S.O.c. is also known to have written: " ...audi IC VERY inefficient" -
quoting archive post.  OK, let's math that out whilst we're here.

Let's assume the audi single pass IC to be "inefficient" = 72%  (BTW, the
audi design isn't inefficient in single pass configuration, it's actually
very efficient, even compared to the best aftermarket, but I digress).
 Giving S.O.c. the benefit of the doubt (B.O.D.), let's assume he halved
again the area of the core (prolly less, calculator ready to stand corrected)

So, a 10% increase in core area will yield approx 10% of the Missing
Efficiency (100 - 72 = 28%), this is consecutive, so the % efficiency gain
diminishes as you increase size.  So a 50% increase in core area of a 72% IC
will yield an IC that is 83.4% efficient.  Since IC is only efficient to the
increase in Charge Air OVER ambient in an Air to Air cooler, this means:

*  At 2.79 PR and discharge temp @ 375f, subtract 70 degrees ambient = 305f
charge air increase * 83.4% = 254.4f.   
*  375f - 254.4f = 120.6f @ t-body.

*  At 2.50 PR and discharge temp @ 315f, subtract 70 degrees ambient = 245f
charge air increase * 83.4% = 204.3f
*  315f - 204.3f = 110.7f @ t-body, a 8.3% increase in air DENSITY. 

*  At 2.00 PR and discharge temps @ 250f, subtract 70 degrees ambient = 180f
charge air increase * 83.4 = 150.1f
*  250f - 150.1f = 99.9f @ t-body, a 17.2% increase in air DENSITY

This really confirms:
TURBO/SUPERCHARGER INTERNAL COMBUSTION ENGINE RULE OF THUMB:  INTERNAL
COMBUSTION ENGINES PERFORM BEST WITH CHARGE AIR AT THE HIGHEST DENSITY AT THE
LOWEST PRESSURE

Truly a case where more isn't necesarily better.  The "claim" by math is just
over 300hp.  I also argue that 300+hp can be achieved at a lower PR than 2.8,
actually, don't need to, several audi cars run at less PR and have more HP.
 And WG boost is ALL of the claim, since there is no computer control past
2.5bar, by definition of a 2.5 bar Pressure Transducer.  I also argue, by
only the EXACT boost claims, that the wrong turbo is doing the wrong job on
the wrong motor.  Given correct sizing of a turbo via it's MAP (PR vs CFM vs
CE vs speed), it shouldn't take a 2.79 PR to get 513CFM.  Even the Porsche
motor, for which the k27 is designed gets 500CFM at a 2.0PR.  More likely the
compressor is putting out more heat than flow @ 2.8PR on the audi app.  I
might suggest some calibration of the 2.8 is in order.  Hint:  what is the
actual turbo outlet temp vs post IC vs ambient?  A PR of 2.8 should give a
much bigger CFM at a 72% efficiency, but physics of the 134ci 10v engine with
the hybrid turbo, prolly is a good indication of choking> wrong turbo.
 Something isn't right when the Audi RS2 gets 310hp at a lower PR than 2.8
AND at lower CFM (and maybe porsche does know what they are doing with
turbines sometimes).  

Does it work?  I suppose, haven't driven the car.  Can it work?  I guess so,
I've been in plenty of turbo cars with owners that don't care what happens
below 4000rpm, or just don't care what happens, period.  Does it mean it's
"better," fast and faster?  "Than what?" would be my question.  Randall
proposed, "better and faster than before."  Ok, but numbers were given.  And
claimed.  A 134ci motor and 2.8PR is needlessly high, by physics and math,
and a real indication something ain't totally right here.  Effective CR
(BMEP) is sky high too, alas, another discussion. So Scott, Chipindippindude
away sir, sonic booms sometimes can be mistaken for head gaskets.  "Motors by
the dozen at 300USD" might get scarce quickly.

Simplistically stated, I need more salt for my margarita, been ingesting big
grains recently.  Specific formulas and variations available to anyone via a
variety of sources.  Only "claims", extrapolated for calculations.  More of
them could indicate more specifically where improvements could be made.  
Claims facinating.  As always, initial consultations are at no charge.

Good to see CIS control and lower chamber pressures finally are being
addressed.  1325 EGT?  Whatever is happening at that 2.79PR, fuel doesn't
seem to be a problem.  

Hmmmmm...  Cough.  I know I saw that S2 badge somewhere...  

Scott Justusson, RS2 wannabe
QSHIPQ@aol.com
'87 5ktqwRS2 
'87 5ktq
'86 5ktqw
'84 Urq