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Re: [T3] timing question

On 3 Nov 2001, at 14:02, Eric Helton wrote:

> First of all, which is better for this car, static
> or dynamic timing?  The section in Muir's book
> on static timing seems to make sense, but when I
> tried it, the car ran very poorly.  However, that
> could have been my problem and not the procedure...
> Also, just to check, I should use the Bentley dynamic
> setting (5 btc) if I do it dynamically, right? (Muir
> shows 0 or 5 AFTC, depending on engine #)

Dynamic is always better, because then you are setting it under 
conditions the same as it when it is in use. Dynamic setting also 
allows you to watch the advance mechanisms and this takes all 
the mystery out of them, and is a great education (and sometimes, 
an eyeopener.)

The 72 timing is complicated. Only Bentley gets it right, so follow 
that book. 5deg BTDC at 800-900 RPM with the green retard hose 
off is the right figure. Don't skip steps, you have to follow all the 

> Secondly, Muir suggests advancing the timing 1 degree
> for every 1k ft above 4000 ft.  Since I just moved
> to Denver at ~5600 ft, I should advance it about 1.6 
> degrees (like I can really measure that accurately!).
> But, he also suggests retarding the ignition a degree
> or two for using gas of lower than 91 octane.
> So, despite the difference in timing being beyond
> my ability to read and set it anyway, it seems that
> if I'm using low and medium grade gas, I should keep
> the timing where I had it when I was in Portland
> at sea level...  Any input on this?

If you still have the FI, I wouldn't try to outthink it. It is actually 
measuring the manifold vacuum as it is running, so it will give you 
the right amount of gas no matter the altitude. I don't think you can 
make up for low octane gas with timing changes, either. Your 
engine has reduced compression ration already, so it should do 
pretty well with today's gas.

You will get less power out of your engine at 5500', but this is just 
a fact of life that every normally aspriated engine faces. There's no 
way around it.

> Also, while I'm thinking about engine numbers, Muir
> shows V and U numbers for 72 and 73 Type 3's; however,
> Bentley says that August 71 on should have engine
> code with X.  (Mine is X...)  Does that have anything
> to do with the disparity between Muir and Bentley's
> timing settings?

I don't think there were any V engines, certainly not in type 3s. 
This is just a mistake in Muir. For 72-3 there were both U and X FI 

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org

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