Date:         Wed, 3 Sep 1997 02:59:19 UT
Reply-To:     Tom Brunson <TABRUN@CLASSIC.MSN.COM>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From:         Tom Brunson <TABRUN@CLASSIC.MSN.COM>
Subject:      Re: Vanagon Ignition Timing
Comments: To: Dennis Haynes <dhaynes57@CLASSIC.MSN.COM>

Dennis,

Thanks for the clear reply on the reasons for the Vanagon timing specs. I do
set the timing "by the book" by disconnecting the temp sensor while the engine
is running, etc. However when checking with a timing light I'd noticed that
both my cars "from the factory" were set slightly more advanced than the 5 deg
BTDC timing mark. "Correcting" back to nominal made the low end response
suffer - even though it was only a 2 deg or so change. This made me wonder how
close the pulley mark is compared to the TDC sensor and digital test rig that
VW uses. (I've also compared two timing lights - same result.)

Since the spec is 3-7 deg BTDC and such a small change makes a noticeable
difference in engine response, I think it makes sense to adjust to the upper
limit. I find negligible difference in idle speed with such a small change.
The car is still within spec, but drives much better.

Of course it would be best to check CO and verify - and with tightening EPA
testing I expect to be looking for a reasonable CO meter soon. I see a lot of
posts about repeated smog tests before people get their cars to pass, and
trying to find the problem by shooting in the dark and paying for a retest
doesn't make much sense. I'd rather pay the money up front for the test
equipment, and KNOW my cars will pass the first time.

Tom
Austin, TX
'87, '91, '97, etc.

>Advancing the timing this way causes two problems.  You increase the
>possibility of engine knock and you also increase the production of NOx.  VW
>sets the timing to reduce the "Peak Flame Temperature"  and uses the 3-way
cat
>to control this most harmful emission.  <snip>

>Hope this helps,
>Dennis.