Re: thoughts on breathing - long

["Dan Bubb" <jdbubb@ix.netcom.com>]

I read an interesting article about the Audi R8 direct injection V8 recently
in Race Tech magazine. Although the Direct injection engine had up to 35
ft-lbs more torque than it's predecesor the drivers all thought the engine
had less performance because the power came in sooner so there was less of a
hump to the torque curve.
The lesson here is that making changes to your engine will make it FEEL
faster or slower, but this doesn't necessarily correlate to whether the
engine is ACTUALLY faster or slower. The butt dyno is a liar. You have to
actually measure to know whether your change was effective or not.
Having said that, installing the larger TB will increase power somewhat if
done properly by porting the manifold to match it. But, it should really be
one of the last things you do to your engine since it will make little
difference until you've done all the other stuff i.e. exhaust, cam, P & P,
blah, blah. Just installing the TB with no other mods will make the engine
feel stronger since you'll be letting in more air for less throttle foot
movement, but the full throttle power difference is negligible.
Colin at TT once told me that you could have an 8V 2.0 breath through a 1.0"
diameter restrictor and it would make no difference in power when I asked
him about the exact same mods you are thinking of doing. But, whatever! Feel
free to bust your ass for 2 hp!
On another note, while everybody's saying how much power they're getting
from swiss cheesing their airbox since they're removing that HUGE intake
restriction, I'd just like to point out that using the stock intake location
(drawing air from the front crossmember) the intake air temp is typically 20
deg hotter than ambient. In stop and go traffic it's typically 40-50 deg
hotter than ambient. Sit parked with your engine running for 5minutes and it
will get up to 135 deg! (data from Haltech datalogs) NOW, the message on
this is that anybody that thinks drawing air from ANTWHERE in the engine
compartment (MY holes are only on the FENDER side!!!) is a benefit is NUTS!
The mod that Patrick Bureau has on his website about relocating the inlet to
in front of the radiator is the only good input I've seen on this subject.
Dan

----- Original Message -----
From: Colin <cwass99@home.com>
To: <scirocco-l@scirocco.org>
Sent: Wednesday, November 28, 2001 8:14 PM
Subject: thoughts on breathing - long


> Hi,
>      I've been thinking about how to improve my 8v breathing and I figured
I'd
> better get opinions before I did something permanent and annoying.  There
are 2
> basic problems to breathing on my stock CIS system and they each attach
> directly to the air box/fuel distributor assembly.  The first is the teeny
> little pipe that lets air in.  I removed the nasty little valve that was
there
> and re-ran the hose directly from the box to the connection in the back of
the
> air dam (yes, it stretched that far without difficulty and stays put).
> I was thinking, though, that this needs to be improved upon.  My first
thought
> was to 'swiss cheese' the box, but then I had a better idea.  If I were to
get
> a 2 inch floor drain and cut an appropriate hole in the bottom of the box,
I
> could attach a second pipe and run it to the grill for a bit of a ram air
> effect.  Done correctly and carefully, it should look quite neat and tidy.
> I've also considered cutting off the hose connection originally there and
> replacing it with a 3 inch bit of pipe.  Again, it should be simple to
make
> this look quite appropriate.  Any thoughts or comments?
>      The second breathing problem I see needing addressed is the pipe that
> joins the air box to the throttle body.  If you look closely, you'll
notice
> it's somewhat skinnier in the middle than on the ends.  I've seen a couple
> advertised replacements for this and they all seem to be based on somewhat
> flattened 3 inch piping with a 48 degree bend on one side to make it fit.
They
> also seem to be based on copper pipe.  My thought was to use 3 inch abs
pipe.
> Does anybody know if this stuff can be bent?  I would guess liberal use of
a
> propane torch would be helpful here, but I'm open to suggestions.  I think
> staying with black abs would look most like the stock piece there now
which is
> important when you're building a sleeper ;)  Besides, I don't have a pipe
> bender that will take 3 inch copper and I don't like the idea of paying
lots of
> cash for something I should be able to build myself for under $10.
>      I see both those things as extremely simple and inexpensive things
that
> should improve the air flow into the system substantially.  My biggest
concern
> is that opening up things that much might be more than a basic CIS system
can
> stand.  I'd appreciate any comments on this.
>      The whole point of this exercise is to make sure I have decent
airflow for
> the bigger throttle body I'm going to try and get from the wrecker's this
> week-end.  Any thoughts on which TB's I should be looking for?  I'm also
going
> to try to get a spare intake manifold for my engine to do the carving on
to fit
> the new throttle body.  Worst case, I go get another and try again if I
screw
> it up.
>      I appreciate any thoughts or comments (except on spelling or
grammar...;)).
>
> Cheers,
> Colin
>
>
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