My cab is running a factory unleaded setup. What is it that allows a VW motor to run on unleaded. Is it the compression ratio of the motor, different cylinder heights etc etc?

Just curious I suppose, given that sometime in the future we may all have to do some sort of mod to our motor.

Also, given that I have a catalytic converter, does anyone know of any exhaust specialists that will keep my cat in if I was to have some extractors made? I have been told V-Force will be able to do this.

Squiz....

it has to do withthe valve seats, the lead used tolubricat them to prevent wear, now you can get harden valve seats to run unleaded

Do a search on unleaded. This q. has been asked heaps of times.

The question I'm asking is what is the difference - and it appears only the valves seats are harder. Is that all? No compression ratio differences?

I did a search and found this thread http://www.aussieveedubbers.com/forum/viewthread.php?tid=2909 
which covers the debate unleaded v leaded, but doesn't technically really cover the motor differences.

Re the exhaust setup then - it appears that a lot of people on the forum might be running unleaded in their motors then without a catalytic converter? So theoretically, I could just go and get an after market exhaust and not worry about putting a cat on?

Squiz....

Sqiz

I think you will find the cat is more to do with exhaust emissions.

Yes - you could do a standard exhaust. It would fail emissions for that year though if it was tested. This is more a Cali thing. Never really heard of it being done here.
What year is yours?? 1978? later??

"IF" you were to modify yours and need an engineers certificate you "may" need it again

The difference between leaded / un leaded is the seats. Unleaded ones are harder.
ALL post 1967 VW's had these heads
Yes - some people lower the compression, but that is more to do with the lower octane of unleaded than unleaded itself

Thanks for the reply Barry. Mines a '76. So if I do replace the exhaust, I could just keep my old exhaust anyway and put it back on if I get hassled. I haven't seen the RTA do any emission test lately [touch wood] so I'll add this to my list of things to do.

Cheers,

Squiz.....

All VW heads have always have had hard steel seats as the heads are alloy. Unleaded isnt a problem and you dont need to modify anything to run unleaded IMO.

Running unleaded fuel on an old car is more a problem when the car has a soft cast iron head with soft cast iron valve seats.

[Edited on 8-12-2004 by Che Castro]

as I said previously in another posting... VW Engines have had Hardened Valve seats and guides otherwise the engine wouldn't last a week as the very soft Aluminium/Magnesium alloy would be worn away....

I believe it could be the Valves themselves...
I have seen Stainless steel Valves for sale...
Maybe these are needed for Unleaded fuel...
If You have a higher than normal compression ratio then Premium unleaded - should be used... plus anything else that will lower the high head temperatures...
and Valvemaster etc just for added protection...
it can't hurt....

I haven't seen this question asked before..... and I don't mind answering the same questions over & over ..
[but only if I know the answer etc]

Lee Noonan -- 20C Heavy Rain - 12.20am SCONE NSW

I forgot about the Catalytic converter...
I don't know of anyone still using them on Beetles...
Most have been replaced by a standard replacement Muffler or Extractors..

The charcoal canister is usually thrown away etc...
although if You want to keep using yours, pull it apart and buy some charcoal from a pet supply as its used for filtering water for tropical fish etc... and replace the old stuff....

I don't believe anyone will be checking old cars exhausts IMHO..

Lee --

http://community.webshots.com/user/vw68autobug 

i have a cat converter on my 72 bug, and run premium in it and has this weird exhaust twin pipes that join to one and stick out the back so when you walk around the back of car you burn leg if not careful

I found this article, might help....

http://www.johnmaherracing.co.uk/technotes_fuel.htm 

That'd be our luck Barls. I think I'll definitely keep the cat converter locked up safe and out of the rain for when I need to reattach it. Thanks for the tip.

However how will that set everyone else up who is running unleaded without a cat? Will every possibly be up for an emmissions violation?

Squiz....

im willing to risk it for the moment as i know mine is running well with in the specs

cat=catalistic....think thats how its spelt

I think people are getting mixed up between the charcoal canister (fitted to post '72 beetles in Australia) and Catalytic converters, these were never fitted to any Beetles in Australia, they are only fitted to some late model US imports

The charcoal canister has nothing to do with exhaust emissions, it filters fuel tank vapours only.

An original VW head should have hardened valve seats suitable for unleaded but when heads got reconditioned back in the day it was unlikly that hardened valve seats got put back it. If you do run unleaded on an old set of heads check the valve lash frequently as a receding valve seat will close up your adjustment.