Can A Stock 16v Exhaust Cam Be Used As An Intake Cam?
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If you've been reading vortex forum, a tuner/builder/racer of
championship A2s since '90 gave some concrete data concerning
the use of the exhaust cam as the intake cam. Here's his quote:
"If you want some cheap horse power then take a second exhaust cam,
cut off the end and install as an intake(this as 10.2mm of lift over
the 9.6mm euro intake and I think, only 8.8ish on the US spec) you
then re-machine the woodruff key slots in both cams to enable a phase
angle of 106 degrees. You then need to install them with a 106 degree
peak opening point on both symetrically. This coupled with fitting
larger exhaust valve seats that enable the use of the 28mm valve and
not the 27mm seat you have now with your 28mm valve, makes a good 155hp
with a suitable exhaust system. You also get an additional 800rpm
attached to your power band (60% of this at the lower end I may add).
However this would be classed as cheating so we didn't actually do this
to our motors. (Pinochio comes to mind!!)".
I've heard/read this many times and have actually test driven a
Scirocco 2.0 16v w/the exhaust cam as the intake but it wasn't in
the best state of tune so it was hard to tell the performance of the cam.
The above is the first somewhat concrete data of the exhaust cam. It
looks like it would be a better cam than the euro intake cam at least on
the high end. I'm assuming that it could be used w/ the stock valve
springs.
Son Nguyen (snguyen@uci.edu)
Here is yet another view, from Todd at Air & Water Enterprise:
The 16V exhaust cam does have the duration and lift to produce
quite a jump in horsepower at the expense of some torque, when modified
into an intake cam. Major downside is idle. On CIS-E cars it's almost
impossible to get it to idle, without cranking the bypass screw wide
open (to over 1500 rpms), and even then it is very rough. The idle can
be smoothed out a tad with a custom chip in the Motronic 16Vs, but is still
quite lumpy. To convert over an exhaust cam to intake specs, cut off the
cam gear snout and approximate a timing mark 180 degrees off on the chain
sprocket. Actual timing will still be about 6 degrees off, which you cannot
compensate for. An adjustable sprocket will only change the intake/exhaust
index to the crank, not to each other. I recommend springing for the
Neuspeed cam for a couple reasons: no one has the Euro 16V intake cam
available stateside, and the Neuspeed profile actually produces a better
powerband. The shorter duration (250 vs 252) and lower lift (.378 vs .380)
seems to retain all of the stock torque curve, while adding some noticable
hp above 5k rpms. I'm not sure if NS profiles the cam this way for emissions
or power reasons, but it definitely has a stronger low end vs the Euro
version. Couple this cam with a Garrett chip, TT exhaust, and a 2.0l and
you'll have a low 15 sec GTI. We built a 2.0l 16V for a Scirocco customer,
using a 1.8l p&p'd head, tweaked CIS-E FI, Borla exhaust and this cam and
he runs the quarter in 14.6 on street tires.
Todd
Air & Water
VW Tuning
Philadelphia
