I was wondering if anybody is using just 91 octane pump gas and, what is the highest compression ratio you can have using this fuel. I have a hard time paying $3.75 / gal. for pump gas and $9 / gal. for racing fuel sends my wallet running. (I'll find my wallet several days later, hiding out in a dark cave shaking uncontrollably!) ;)

Anyone?

Hey Kurt, we run straight 91 octane gas in our 11 and am quite happy with the way the motor performs. Not quite sure what the compression ended up being but it is relatively low. On the dyno we went up to 34 degrees total advance with no sign of pinging although the motor made its best power at 30 degrees total advance. Keep in mind every motor combination is different in relation to timing. Yes, a lot of compression = free horsepower but for me, the cons far out weigh the pros when it comes to compression. I run low compression in all my VWs from my buggy to my daily driven street car with 2275cc power with no problems. Hope this helps.

Some 9 car guys run premium pump gas in their motors or splash in an octane booster in the fuel cell every tank. Those motors run 7.5:1 and a cam like an engle 110 or a FAT FC411. Make sure you are running a big enough jet with that engine or it might ping and that's no fun. 30 degrees total advance on an 009 and probably a 135 or so mainjet.

We played with main jets from 125 to 150. The motor liked the 135 main at 30 degrees total. That is on straight 91 octane. No boosters or half and half concoctions. The motor was built with longevity in mind. OK I'm not gonna lie. Our compression is top secret. A recent tear down to freshen up revealed nice wear patterns on all bearing surfaces. The pistons had burred wrist pin bores making it difficult to remove them but that's typical from the side load that is placed on them by the rods from the non counter weighted crankshaft flexing at high rpms. Other than that, everything worked well and looked sweet.

I will let you all in on a secret, at sky hi compression I have 0 engine issues, and have not had the bottom end apart since 2003. one and only reason the top[ end came off, was to put duel port heads. I will give you another secret, Castrol syntek 5-50 keeps everything and I do mean everything inside the motor looking brand new and 0 burning of anything. As hot as my motor runs compaired to a low compression motor is big, but the oil I have found out over the last 33 years of trying everything on the shelf that nothing else compaires. I have run low and had the light blinding me with no issues.

To answer Kurt's original question, yes you can run a pump gas motor in an 11 and still be competitive. Our last race was 118 miles and our fuel costs came to a grand total of about 45 bucks. I have no idea what it would have cost with race fuel since I haven't bought any in long long time. We also always have a bit of gas left over. It comes in handy to light the campfires at night and dump the rest in the motorhome for the ride home.

My compression ratio is currently 9.0:1 but the engine is not yet in the car. Is 9.0 to 1 too high to run 91 octane pump gas or is it OK? I don't want to pull the heads and reset my valve geometry if I don't have to. Thanks again for your insight.
VW Kurt

For 9:1 you're definately pushing what's possible for a vw type 1 and 91 octane. I know 9 cars run 7.5 and they run 91. 9:1 on a liquid cooled engine would be totally safe, even higher with electronic tuning of the timing advance and fuel delivery would be possible but given the items we work with on a vw racing engine (solex pic and 009 dizzy) I would use octane as a band-aid for not always having the perfect mixture/timing for the engine load/rpm.

You only need the extra power of a race engine if you want to go fast, but then I guess your suspension needs to keep up as well. Ah, so many considerations.....

I'm thinking something mild for the cam on a 7.5:1 like an engle 110 with a stock flywheel would chug along over anything. It would certainly be drivable! Add in some good jetting and a gutted exhaust and you could probably have some decent power, it would last forever too!

I appreciate the insight. I've got the 110 cam in it already, so now I'll add some copper head gaskets and cylinder shims to get my C/R down to a respectable level. Then all I have to do is cut some new pushrods to length and bolt it all back together.

Thanks!

VW Kurt

You're basically running a class 9 engine at that point. Their motors last forever. About 135-140 on the mainjet, 60 pilot, and 30 degrees total advance. Use a stock muffler that has been gutted and don't forget to remove the heat riser to the intake manifold, that will add a couple of HP by itself. You should be fine with this setup and single HD valve springs.