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RE: WTB 272 Cam + comparison numbers

On Wed, 15 Dec 1999, Bruce Bell wrote:

> The comparison numbers comparing stock, Schrick and Schrick + exhaust are at
> the bottom of this post with little editorial.

	Great thanks.

> Yes, I understand Ned found another 200 rpm under the rev limiter. He tells
> me that's about all you can get with a FPR hack or change as the ecu
> apparently manipulates the signal to the control pressure regulator.

	I still dont fully understand the 4kq RPM cutout.  The FPR
supposedly controlls it by counting Rev's.  But if thats so then why the
huge disparity between cars.  My GF's cuts out at 6,700 as well.  I'll be
putting the MC cam into it for a poor mans upgrade when I get a custom
ground one for the turbo MC.  Then I'll really be bouncing off the
limiter. :-)  Anyhow, other 4kq's I've driven cut in anywhere from 6k to
6,700.  Mine cut in at 6k.  Put my GF's FPR in and it didn't change.  So
that wasn't the difference.  My car was still charging hard at 6k but I
couldn't go much higher.  I used to be able to, then that
started.  (havent tried with the turbo motor but they seem to be all
closer to the same.  every MC I've driven cuts in at around 6,600 from
what I remember.  
	On this note, my friends VW Jetta has a cam and charges really
hard to 6,500.  Its an 86' 8v motor.  Anyhow, about 1 in 10 times you
charge hard the rev limiter will suddenly cut in at about 5,700 or
so.  Wierd.  Really wakes you up.  
	So figure that one out.  Bad Relay maybe???

> We could be comparing apples and oranges as far as exhaust goes. Mine is an
> Urq SS cat back with a short glass pack for a center muffler and a cheap,
> most defiantly not Borla quality, rear turbo style muffler. If you have one
> of the Borla universal mufflers for a normally aspirated motor then you are
> way ahead of me here.

	Could be.  But my system is hardly tuned.  But the muffler is
about the best you can get.  Sure sounds nice. :-)  I've seen a couple
situations where this showed.  ON a friend VW GTI.  Had a 2.25" custom cat
back with a turbo muffler.  Was louder but not really that much more
powerful.  A little at the top end maybe.  THen he put on a Techtonics
tuning system.  BIG difference.  Sound was still audible but was mellowed
out a bit (much nicer)  and lower.  But the power was Definately
better.  2.25" system as well.  For the 1.8 that seems to work well.  BUt
a 2.2 or 2.3 seems to work with a well done 2.5".
	The other situation was a friends A4 2.8.  Put on a custom
system.  Sound was a little better.  Gained a TON of torque but it DIED at
high RPM.  To bad.   Then put on another system from....Doh...starts with
an S...uhh...SUPER Sprint.  There it is.  Supposedly they wont even sell a
system if it doenst build more power.  It made a big difference, lost a
little low end compared to the other but still strong, but pulled like a
banchee all the way to Redline.  (well, as much as a 2.8 12v can pull like
a banshee) :-)
	Anyhow, definately food for though.  Boy, turbo's really simplify
things dont they.  With them, Free Always equals better.  3" no
muffler.  Sure, turbo wont mind. :-)

> Decide for yourself. To really see the picture graph these numbers in Excel.
> The first two column are from my review of the Schrick cam and the third is
> after I installed the exhaust. The testing with the exhaust was done at an
> altitude considerably lower than the 5300' where I live, so I used the
> correction factors from SAE J1349 to standardize the results to 5300'

	Interesting.  See below

> And yes, that surge really is there at 5250 with the exhaust and it makes
> the dip at 4800 all the more obvious. (I noted you observed it too). I think
> this shows the value of having a properly tuned exhaust. Mind you I never,
> certainly hope not, said 2.5" exhaust systems are bad. Just bigger and freer
> flowing aren't always better with a NA motor.

	Well, thats eye opening.  How did you get these figures.  I'm
assuming they are Torque figures of some sort at the
wheel??   G-tech???  I thought it only did HP.  Hmm.  
	ANyhow, you had a SERIOUS drop.  My GF's car has a 2.5" aluminized
system with no Center muffler and a $30 Dynomax (normally $70 but Summit
has them for $30) 2.5" Turbo muffler.  Hers didn't have the results my
Borla did but seemed to work well.  Breatherd easier above 4k and didn't
seem to lose any down low.  Actually, she still has 2.25" back to where
the Center Resonator used to be and then it goes 2.5".  short on money at
the time and the Extra $40 or whatever it was, was needed for a Radiator
Temp switch. :-)
	I was just thinking.  The ur-q system is all mandrel bent, and I
believe it also is slightly bigger than 2.5" right??  Its metric and
thought it was slightly larger.  Like 2.5" plus a few mm.  Anyhow, with
the mandrel bends etc, maybe it actually flows better than my
system???  WHo knows.  But if thats the case then maybe I'm at the upper
edge of the flow envelope for HP gains.  I wonder.  Maybe I'll take the
cat off and do some back to back tests and see if I lose power by ditching
the cat or get results like you did.