Can I mix race gas and 93 Octane a little at a time without it hurting the sensors? How much can I mix? I have about 5 gallons and would like to mix it to see if I have false knock and to get rid of the gas too.

 

Depends how much lead is in it. Stock O2 sensors are supposed to be able to handle 50 hours of lead exposure. But you always run the risk that one of yours will be in the statistical minority that is killed quickly by lead exposure.

Why not just find some 100-octane (or even 104-octane) unleaded? Most tracks will have some high octane unleaded available.

 

My home track doesn't have unleaded and the three other tracks in my area are over 3 hours away.

 

As Fred said it just depends on how much they are exposed to. I was in a pinch at a race and had no fuel left in my container(forgot to get fuel before the race) So I put 2 gallons of leaded fuel in my car to get thru the race. Trashed the O2's that day. They were stock sensors

 

Lead poisoning slows the response of the sensor over time. It does not render them useless immediately. I would not hesitate to splash 4-5 gallons of C12 for instance to allow you to determine if you're experiencing false knock. Just make sure your fuel filter is fairly new as you cannot be sure of the purity of the gas you put in. Of course this goes for anywhere but unless you purchase a drum from your fuel vendor any kind of gunk could be included in your fill.

 

I've run quite a bit of C16 through my engine, over a period of several years. The O2 sensors are only there to plug the holes in the collectors, but I can still monitor them on my ScanMaster. One of them "appears" to be normal, and one of them seems to read low. But that's just observing the readings and knowing what they should be from a wideband. There is no way to measure if they have slowed down, and that's what would worry me if I was still running closed loop.

I remember when NGK came out with their "lead tolerant" O2 sensors (which actually means they can stand twice as long an exposure as a standard sensor). A magazine picked up a couple and tested them. One of them failed immediately on exposure to leaded fuel. The replacement lasted longer.

Check the local performance shops... some of them will sell 5 gallon pails of VP Fuels or Sunoco racing fuels.

 

Maybe mine were on the way out or something then. My car ran fine at previous races. That day I ran leaded fuel (added 2 gallons into a near empty tank) and when I got home the SES had been set for O2's.... I dont remember the exact fault but I had to replace them to get the faults to clear.

I had run 2 or 3 rounds after that and idle time around the pits and home.

 

I was thinking on the order of running maybe a couple gallons race fuel mixed with maybe 10 gallons of 93 unleaded to boost the 93 to see if I still experience the knock. Maybe I shouldn't even mix the two? I really believe I have false knock. looking at my Datamaster logs. Anyone care to take a look?

 

I was allways told Lead kills O2's real quick.
Do we have some kind of old mechanics tale here?
Would there be a difference between 1 wire and heated?