Unleaded Information.
 
Bit of a can of worms this one, some say this some say that, this is my take on it. From the 1970's all VW's have the ability to run on unleaded due to hardened valve seats, i.e. if you run your VW on unleaded you will not suffer from valve seat recession but you can still have problems.
Higher performance engines have a higher compression ratio, this gives a hotter combustion temperature as your squashing the air more making it more volatile, lower quality fuels which unleaded basically is has less protection against pre-ignition (ignition before the spark plug ignites the mixture) and due to the hotter cylinder temperature engines with higher compression ratios are more susceptible to pre-ignition (pinking). Pinking is the light metallic rattling noise you hear when you put your engine under load, the noise is actually the sound waves of the igniting mixture hitting the piston and cylinder bores and head.
Octane ratings of petrol refer to its ability to resist pinking, the higher the number the higher its resistance to pre ignition.

So, what can you do if you have a car with a higher compression ratio and want to run it on unleaded? You can retard the ignition timing bay a few degrees, retarded timing not only makes the spark occur later but it also runs cooler thus combating pre-ignition on two fronts.

Nearly all petrol engined VW T3 Transporters will run on unleaded without adjustment except the following engines.

1900cc GW code engine made between 1983 and 1985 - 90 bhp
2100cc DJ    code engine bade between 1985 and 1989 - 112 bhp.

The ignition timing must be reset to the following specification.

GW engine 4° - 5° degrees Before Top Dead Centre without vacuum advance at 880 RPM
DJ   engine 4° - 5° degrees Before Top Dead Centre without vacuum advance at 800 RPM

The buffers amongst you will spot that the GW engine is not normally found on these shores and is infact a 1900cc waterboxer injection, the DJ is also injection, so I would suggest that if you have a carburetor engines Transporter then you will be okay and if you have an injection engine then check for pinking.

Setting ignition timing by the seat of your pants.

This is the method that you sometimes have to use when setting the ignition timing to predetermined parameters and it still pinks, it can be better to set your timing like this anyway as every engine is different and different engines can cope with varying amounts of advance.
So, you set the timing and it still pinks, get your timing light and retard the ignition by a further degree at a time until it stops, simple, it may take a few road tests but you'll get there and you'll get the optimum amount of ignition advance without the pinking, and remember kids have as much advance as you can cope with, you'll go faster!

Remember..
Once you have messed with your ignition timing you may notice a slight change in you idle speed, this will require resetting as advancing ignition timing makes it run faster, retarded timing runs slower, so you may have cutting out type faults, this is normal after messing with the timing and your idle mixture will have changed also, its worth booking in at a garage for them to reset your idle mixture and idle speed.
 
Other pages worth a visit.
Timing with DIS.

 

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