Re: Mystery cam

["Bruce Bell" <bbell@surview.com>]

They could have done that for fuel economy or emissions. I stand by my
statements and suggest that with this knowledge a NF or NG motor could
benefit from a cam upgrade. The turbo cam obviously isn't an upgrade in this
case.  Contrary to my generalisation suggesting turbo cams are not
appropriate for normally aspired motors, I would agree it is quite possible
the JT or KX also shared cams with turbo motors. Certainly the JT W/turbo
cam I drove a couple of months ago didn't "feel" much different than a stock
JT, However a JT with a Schrick has a much, much different feel, with good
power pulling through 6000+ rpm.

Curious, I know the NF/NG have 40 mm intake valves, does the MC?

Bruce

-----Original Message-----
From: Buchholz, Steven <Steven.Buchholz@kla-tencor.com>
To: Q list <quattro@coimbra.ans.net>
Date: Tuesday, July 14, 1998 12:24 AM
Subject: RE: Mystery cam


>> First, if it is indeed from an '82, it is not a hydraulic lifter cam.  In
>> the second place, unless you want the torque peak to happen at a lower
>> rpm,
>> then this isn't an upgrade. Factory Audi turbo cams do not have any
>> appreciable overlap. Generally they have none.  As a rule, as the overlap
>> increases, the torque curve moves higher in the rpm range.  With a turbo
>> obstructing the exhaust (read back pressure) the cam is designed with
>> little
>> or no overlap as an anti-reversionary  measure. Also, because of that
>> obstruction any scavenging effect from the exhaust pulses which would be
>> beneficial to a normally aspired motor are lost.
>>
>... well ... as was discussed on the list some time back, it certainly
>appears that the cam for the MC engine is identical to that of the
>high-compression NA 2.3 liter engine.  I did confirm this with both the
5000
>and 100/200 Bentleys (NOTE: The high compression MC in the late '89-'90
200Q
>is different).  I realized that I had the fiche for all the cars, so I
>looked it up.  Sure enough the NF and early MC engines all use the same cam
>(034 109 021 K) while the later MC's use (034 109 021 AK) and the normally
>aspirated KZ engine uses 034 109 021 P.
>
>Seems like Audi thought that the cam worked fine in both turbos and NAs ...
>what it will do in a 4k's JT engine I can't _yet_ say ...
>
>HTH!
>Steve Buchholz
>San Jose, CA (USA)
>