RE: New Math

[Anton Gaidos III <anton_gaidos_iii@firepower.com>]

Okay, I feel I have a better understanding now. I should have thought of
this myself. So it would stand to reason that to open the exhaust as
much as possible is a real plus provided the turbo can spin up quickly
enough to achieve zero pressure (sequential turbos come to mind). So if
you cannot spin up your turbo quickly  any effort to increase exhaust
flow works against you until the turbo is spooled up. This must be where
the benefit of advancing the timing early on comes into play - to get
out of the off-boost phase. I run 14 degree advance on my Scirocco for a
similar reason - I use a crude ram air setup on my car and the faster I
go the more air I get. 
 How would this pertain to exhaust ports or the exhaust manifold itself?
For that matter, how would this effect exhaust valve sizing? If you have
a setup that gives you boost quickly would these modifications pay out.
Keep in mind this all hypothetical for me. I am really planning on
keeping my Quattro basically stock.
 The heat reduction I fully understand and must be considered critical
for any forced induction motor. Hence the Sport Quattro front end. That
gives me a thought. We have been playing around with various
heatexchangers on some experimental 400Mhz multi-processor cards that
are pretty cool. We switched to some very high volume fans but the
coolers have remained in my thoughts. However, for some highly
experimental applications... Oh well, another day but out of curiosity
has anyone converted turbo inlet air temperature into watts radiated?
 Thanks Scott for the lesson. These things should of occurred to me!
>----------
>From: 	QSHIPQ@aol.com[SMTP:QSHIPQ@aol.com]
>Sent: 	Thursday, February 13, 1997 3:15 PM
>To: 	Anton Gaidos III
>Cc: 	quattro@coimbra.ans.net
>Subject: 	Re: New Math
>
>>upgrade always cam and exhaust? Is it not best to first find a good
> >compromise in a cam, free up restrictions in the exhaust and then play
> >around with boost, mixture and timing? Again a compromise with low end
> >torgue vs free flow 
> >needs to be delt with. Unrestrict your exhaust too much you lose low
> >end. Get too much lift you get lousy idle and again move your torgue to
> >high up the rev limit.
>>>>> 
> This is ok for a N/A car, turbos are a special case (there's always one...)
> I would look at a turbo map first, then address boost equation, the cam
>really is pretty far down on the mod list for performance gains in a turbo
>motor...  If you got everything else, it;s the place to go...  Exhaust yes,
>but for different reasons...  A turbine wants the free-est exhaust possible,
>it really could car less about back pressure for torque, the faster the turbo
>spools the faster the car will go....  Really torque is increased, what
>decreases is "off boost" performance, remember a turbo is really N/A motor up
>to 0 vaccuum, and a pretty low compression one at that...  Once on boost, no
>restriction gives more torque on a turbo motor...  So really the trick is
>back at the box, get the car moving with ignition advance to get to 0>
>vacuum.....  So, basically, a 3in exhaust system is an improvement on a turbo
>motor without regard to <0 vacuum....
>>>>>>>>>>> 
> With forced induction there is the overlap
> problem too. Also what about manifolds and cylinder heads. There is that
> equation to contend with too. Do you port you head and manifolds to
> really enjoy a good ECU upgrade even though your ECU is more a timing
> map? As I said I'm a rookie here but it seems to me many of the age old
> rules apply. Get a good balance with a cam, exhaust and porting first to
> eliminate the factory restrictions.
>>>>>>>>>>>
>
>Careful on this....  Porting the heads and manifolds is a air flow argument,
>one of many to apply to a turbo car...  What are you really doing by that in
>a turbo car?  Eliminating restriction, which gives more flow and less heat...
> Back up some though....  Wouldn't you first want to address heat elsewhere
>in the tweeks to increase volumetric efficiency?  Say a cooler running turbo,
>or a larger IC, nary cracking the head on the audi....  Beware that turbos
>also change inversely the design of the head work...  Since a turbo works
>more efficiently as the flow to it increases, what does one do with the
>valvetrain?
>  >>>>So where is the starting point with forced induction? Do you go
> straight to the ECU and WG or follow the old rules first?
> Anton J.  >>
>I have simpler rules, the racing one....  Bang 4 Bux, what do you get the
>most from...  Easy answer there...  A box and WG mod runs you 500-1000USD
>depending on "service" (see archives)...  2.0 bar pressure (and conveniently,
>kkk designed the turbo to run here), all other things being equal, raises an
>MC motor to the 220-225HP level....   That's 55 hp for 500USD = 9bux per
>hp...  I've spent triple that for less....  So the rules have changed...  B4B
>is the rule to follow now....  For that, the cam is waaaay down on the
>list...  Your best cam profile will yield prolly 30hp on a totally tweeked MC
>motor...  At what cost?  A decent Schrick is 600USD+++  and yields more like
>20hp (since it is not a turbo cam, a N/A one) , that translates to 30USD++B4B
>hp.... Lots of other places to play first....  And you haven't addressed the
>inherent fuel problem that cam will exponentially create... 
>
>So, really no surprise there are no turbo cams stock available after 4
>years....  Turbos require some different thinking from the "old" school, the
>audis make it easy to do the "new" math however...
>
>My .02 arbitraged thru the peso
>
>Scott
>
>