Club 80-90 Forums

Petrol octane

What octane are people runing in ther vans?

Iv had my van a year now and have been running premium fuel which i believe shooed be 93-95 octane. I am running a 2.1 injection motor which vw state shooed be run on 98 octane.
iv had problems with pinking but i advanced the timing and it has been a lot better and over the winter has been not a problem at all. However the first hot run up a steep hill of this year and theirs the pinking again.
I'm now running on 97octan and i am amazed at the power difference , the all round smoother driving and the cleaner starting.
But it still has a slit pink under heavy lowed. Im puting this dawn to the 97octane and not 98octan that it wants.

I'm thinking of running hi-octane in summer and low in the winter as the heat seems to effect it . Iv also considered fitting an inter cooler to coll the intake air.

I seem to be getting better mpg from the 97 octane.

I think about 98 octaine then think so far so good and put 95 in my 2.1 i runs fine and has for at least 3 years.....but i do sometimes worry about what i might be doing to the engine thingie.

Andrew

2.1 injection should be 10 deg Before Top Dead Centre.
the V notch is on the pulley at the correct position, NOT the U notch that's TDC
If that is correct your post suggests the distributor is not advancing properly
Check the vac lines and centrifugal weights
suck on the vac pipe to see if the advance mechanism is working

Other reasons are ...
Inlet side air leaks weakening the mixture.

kevtherev wrote:2.1 injection should be 10 deg Before Top Dead Centre.
the V notch is on the pulley at the correct position, NOT the U notch that's TDC
If that is correct your post suggests the distributor is not advancing properly
Check the vac lines and centrifugal weights
suck on the vac pipe to see if the advance mechanism is working

Other reasons are ...
Inlet side air leaks weakening the mixture.

Don't understand a word of that

I just chuck premium in. I've chucked 97 RON and 99 RON in - runs fine on both. Coughs like a seasoned smoker if I so much as consider putting bog standard unleaded (95) in - which I have had to on occassion due to a choice of that or diesel (Wales)

Nathan Baker wrote:Petrol octane
I've had my van a year now and have been running premium fuel which i believe should be 93-95 octane. I am running a 2.1 injection motor which vw state should be run on 98 octane.
I've had problems with pinking but I advanced the timing and it has been a lot better and over the winter has been not a problem at all. However the first hot run up a steep hill of this year and theirs the pinking again

A few things best put in bullit points
1) If you get pinking you 'retard' NOT advance the timing.
2) VW state 98 Octane so you must have a 'DJ' 2.1 which has the highest compression ratio of 10.5:1 compared to the other 2.1's SS & MV which only run 9:1 compression.
3) The higher compression of the DJ produces more heat and so has a greater tendancy to 'pre-ignite' it's fuel especially when hot.
4) Higher octane fuel 'has a greater resistance' to knock/pre-ignite/pink as in... ignite the fuel BEFORE the spark and that is why it is needed in a DJ 2.1.
5) Higher octane DOES NOT MEAN more power BUT...as it resists pre-ignition, it will give the impression that your engine is running smoother/better, which obviously it is!
6) Running an engine long term with pre-ignition issues can produce all sorts of engine damage, these may include: burning spark plug electrodes, pitting and or melting of piston crowns or even holeing pistons.

Martin