100 av fuel

[82turboruf]

Any problem running a mix of non ethenol 93 with 100 LL in a 82 930
turbo with no cats, a 1 bar spring and andial fuel enrichener?

[darrin]

what problem are you trying to solve for with 100 octane? Higher octane can lessen detonation problems, but actually provides less energy/power than lower octane. So, it's my understanding that (in general) if not detonating on 93 octane and you don't have electronics that can adjust timing to account for the higher octane fuel, you shouldn't see an advantage from adding av gas

[RedCoupe]

My understanding is that, despite the term low lead, 100LL has much more lead in it than leaded premium did back in the day. Could cause combustion chamber deposits and new problems.

[Steam Driver]

You are correct about 100 Low Lead avgas. “Low Lead” is a relative term in comparison to the older 100 octane avgas only, not leaded motor fuel.

When 100LL became the standard and 87 avgas went away it caused, and continues to cause, plug fouling issues on the aircraft engines designed for lower octane.

Besides the lead there’s another issue, that of lower vapor pressure of avgas. (I guess to forestall vapor lock at altitudes.) This causes difficult cold weather starting, although with fuel injection that may not be as big an issue. But with carbureted engines and generally much smaller batteries it is with airplanes.

Since avgas is usually hard to come by (because it’s against the law to sell it for road use since it's untaxed) why not just look for a Sunoco station? They generally have high-octane fuel. But in a lot of areas they’re thinner on the ground than airports!

[82turboruf]

I was told that leaded is a lubricant.
Does anyonr know if the avgas retains its octane rating longer than other
which degrades with time?

[GH85Carrera]

AvGas will last a long time and not “get old” as many hobbits pilots may not start an airplane for months on end during annual inspection issues, and getting the problems fixed. So yea, it is great for long term storage. It sucks as a car fuel, as if it designed for aviation engines with 2,400 RPM red line, at altitudes where air tens can be -20.

[spuggy]

Originally Posted by GH85Carrera

It sucks as a car fuel, as if it designed for aviation engines with 2,400 RPM red line, at altitudes where air tens can be -20.

This.

Additionally, even 100 & 110 octane race gas (formulated for cars) will not make the difference you probably think it will to the susceptibility of your motor to detonate.

State-of-the-art 40 years ago for a CIS 930-based motor hasn't aged well. There are much better ways now to control fuel/ignition/knock, even while retaining CIS (the real limiting factor/root of the problem). If you've still got the pancake manifold, the 7th injector hack into a manifold designed to run dry is also not considered a great idea - those manifolds are well known to flow unevenly, and fuel distribution wouldn't be ideal. And the period-correct manual boost controller knob is known colloquially as the "dial'o death" for good reason.

Go say "hello" on the 930 forum (and for maximum response, be sure to post some pictures of the car). You'll get expert device from guys that've been tuning and running these cars for a long time. My CIS 930 made 370 at the wheels with great mid-range response from bolt-on mods, safely, for years, on pump gas before EFI. It would never have occurred to me to modify it before hanging out there...