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Hi all,
We dynoed a Genie header on a 93 SLC equipped with Schrick 268s and manifold,
as well as Garrett chip and Techtonics exhaust. The header is a beautiful
piece, with very long primary runners. Fit is very nice, all stainless
construction. Unfortunately, it made no appreciable power. There was a gain
of 3-4hp between 59-6500rpms, but losses of 2-3hp at various other parts of
the curve. Initial runs looked promising, but after full heat soak the gains
disappeared. This is actually not very surprising, since the standard
"header" system is nicely designed, and certainly not a restriction like the
old single downpipe VWs.
Next on the car was a set of Schrick 276s. These are hairly lumpy cams, with
ultimate hp in mind. My prediction was that they would be hard pressed to
improve on the 268s without head work, since the 268s basically maximize the
higher rpms so tangibly without a torque hit or gain. The 276 gains would
theoretically start even later, meaning that their benefit would be seen at
6500rpm+ levels, which is not only way higher than anyone keeps their motor
revving on the street (even me on a road course), but should be restricted by
the standard 2 valve head configuration at that point.
Sure enough, the 276s made no more power up top, and took a 6-7hp hit down
low. Ignition timing was maxxed, and fuel mixtures were just about perfect.
The problem is that the overlap is so large on these cams that cylinder
pressures are compromised. But if the head/motor has the ability to move the
extra air they introduce the gains will be there. I predict these cams will
work well with a big valve head. We'll see. That is next.
Todd
Air & Water
www.awe-tuning.com
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Tue May 18 09:19 CDT 1999
