rws <rwsam2002@yahoo.com> wrote:
> Jon.
> The Vacuum went up to 23-24"/hg when increasing to 1500-2000 rpm.
> So,I thought what Bernd said (in another post) was that if what I'm
> seeing (increased vacuum) there might be a plugged exhaust system,
> true?
I'm not sure that there was a satisfactory conclusion from that
thread, but regardless of who said what, a restricted exhaust system
will always result in less vacuum, not more. For example, say your
idle vacuum was 18", and when you go to 2000 RPM, the vacuum goes down
to 13". THAT would be indicitave of a restrictive exhaust system. If
your idle vacuum is 18" and it goes up to 24" at 2000 RPM, that does
not indicate a restrictive exhaust to me.
If you still aren't sure, I highly recommend doing a google search
or browse through the auto repair section at your local library. Auto
tech and DIY web sites, Chiltons, Haynes, etc. They all say that a
restrictive exhaust (or clogged cat) results in less intake manifold
vacuum.
Another test you can do is to actually measure the pressure in the
exhaust system, which is pretty easy if you've got the style of vacuum
gauge that indicates pressure as well as vacuum. You can remove your
upstream O2 sensor and get something to screw in there in its place -
either a bolt that you've drilled out or an old spark plug that you've
hollowed out, etc. (the thread is 18mm x 1.5), and weld/braze
whatever adapter on there that you need to be able to hook your
pressure gauge to. I would have to do some searching to find the
answer for sure, but IIRC, around 1psi at idle is normal and higher
than 3psi overall would indicate a restriction.
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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