Date: Thu, 17 Jun 2010 15:29:59 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Question about ignition timing..
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Hi..
my advise..
first one is do not run premium.
run mid-grade, but not premium.
on timing .....basically you want as much advance as it can take without
pinging .
You can test for pinging by intentionally lugging it and giving it a fair
amount of go-pedal.
If it pings, back off timing a little.
higher altitude requires less octane of course.
but ...basically ...as much timing as she'll take and still not ping.
pay attention to timing curve of course ...
'usually' timing curve is ok.....though I find stuck centrifugal advance
mechanisms, and loose wandering ones too ...if your dist has centrifugal
advance.
if advance is entire computer controlled ( like it is in a 2.1 wbxr ) then
it's likely working.
if it's centrifugal and vacuum advance/retard, like on a 1.9 wbrx ...
make sure the timing curve is working fairly correctly.
but really .....'before emissions reasons' ....the best timing is the most
you can get away with without detonation.
too advanced base timing causes hard starter cranking, you don't want it
that advanced initially.
10 degrees btdc is 'about right.'
20 btdc for a base timing is too much.
too advanced initial timing causes a high idle speed too.
you also want to make sure it's not extremely too advanced reved up ...
like check it at 3,.500 rpm .......50 degrees there would be too much,
roughly.
don't use premium.
start out with mid-grade and time for 'the most you can get with no sign of
any detonation or pinging' ,
and be sure the timing curve happens too.
premium 'burns to slow' ........it is just not right. I am not the only
professional that says this either.
I sold a Porsche 914-6 to a guy who owns a 8 bay german car shop in
Oakland, Ca ...
so he should know something ...and he said the same thing.
mid-grade.
and I don't care to have an octane war discussion either !! lol.
re : " I have forgotten what the reasons and the direction is to
> adjust the timing for pre-ignition and regular vs premium fuel.
for higher alttitude, less octane is needed.
I would think you could run more igntion advance at altitude, compared to
sea level, in a naturally apserated engine.
You advance timing more to take advanatage of higher octane fuel.
You use less advance if you need to, for lower octane fuel.
just so she goes good and don't ping !
that's your goal...
nice starting, smoth idle, good acceleration, no pinging, and lastly , good
fuel milage.
you get that, and she's about right.
Scott
www;turbovans.com
----- Original Message -----
From: "Don Hanson" <dhanson928@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, June 17, 2010 10:54 AM
Subject: Question about ignition timing..
> I'm swapping blocks and distributors, re-configuring an inline four gas
> VW
> motor for my van. 92 digifant 1.8 liter heads onto a 94 Jetta ABA 2.0
> liter
> block. Keeping the 1.8 head will raise my compression ratio to 10:1, I am
> told. The digifant EMS does not have a knock sensor provision. For now I
> am planning on running the new motor set-up on premium 92 octane fuel or
> maybe mid-range..I am daily driving at around sea level. I often go to
> elevation in the van... but not too often above about 6000' maybe a few
> times per year.
>
> So the Bentley book calls for 6-8 degrees BTDC on the 1.8 and the 2.0
> liter. They are both in the 9-9.2:1 compression ratio range.. It has
> been
> some time since I timed a vehicle. The last ones I messed with still had
> points ignition. I used to have to change the timing on my air cooled
> German cars...Beetle, Splitty Van and a 356 S-90 Porsche when I went from
> altitude down to sea level because they would knock or run too hot
> sometimes...but I have forgotten what the reasons and the direction is to
> adjust the timing for pre-ignition and regular vs premium fuel.
>
> Anybody care to give a short run-down on how to adjust the timing for
> various conditions..like raised compression ratio, regular vs premium
> fuel,
> trading power for peace of mind about knocking motors, etc etc?
>
> I should be OK just running premium for now, but I might like to switch to
> regular if the motor makes sufficient power on the cheaper fuel and
> doesn't
> want to destroy itself too quickly by pinging badly.. If I do try to
> 'shade' the timing towards regular gas or if I plan on heading through
> some
> high mountains, what's the drill?
>
> Thanks in advance
> Don Hanson
