SKFengineer

Okay so I have a 1987 IROC with a 355 TPI motor that has a laundry list of engine work and modifications. For race days auto-X, drag race etc, I run without a CAT and I use a mixture of half 93 Oct pump gas and Sunoco Leaded 110 race fuel.

I know that leaded race fuel with the CAT is a no-no but someone told me last time I need to worry about messing up my O2 sensor also. I've been using this fuel combo during racing for a couple of years with no issues but was just wondering if I should also keep an eye on my O2 sensor. FYI -the last time I had the scanner hooked up to the car the O2 sensor was still active with lots of "crosscounts".

Thanks in advance.

BLWR PWR

If used enough it will degrade your o2 sensor to the point where it wont "read" as well as it should. I have a well built 383 with a supercharger. I used to do this on track day as well(3-4 times a year). Thought it would give me more power and keep me out of detonation on 100degree days. It got to be a pain in the a$$. The mixing of the fuel etc. Tried without the race gas and ran the same numbers!! On hot days I add some octane boost to help with (imagined) detonation. This is a street car that runs pretty well(7.45 in the 1/8 mile). You can also make your own race gas using tuoelene or xylene mixed with 92 octane, but this proves to be a pain in the butt also. Why not use unleaded race gas if your car needs it?

SKFengineer

I actually have tried the Tuolene route after visiting the Turbo GrandNational forums some years back and the car ran very well on a 10 part gas 1 part Tuolene ratio. The mixing of that fuel was a real pain in the tail, it cost an arm and I leg I was never sure if I was really getting 100% pure Tuolene from the paint store. The race fuel I've been using now is available at the local speed shop around the corner from my house and I get a five gallon VP fuels bottle full when I stop down. Before I fill the tank with pump gas I add enough to be about a 1/4 to 1/3 race fuel vs. pump gas. The compression of my motor is about 10.5:1 to 11:1 so 93 oct pump gas is an option as far as the detonation goes but the scanner does pick up more "knock" events when I'm using only standard pump gas. Also the other thing I like about the race fuel is there is no ethanol which makes it stable for over a year so it's good for storing the car too. I'll admit I mostly use the "mix" for auto-X these days so I don't have a good apples to apples comparison of the power it may or may not be producing but the car feels very strong.

Thanks for your information about the O2 sensor, I guess I need to rethink the mixing thing but I really liked the method I've been going with the last few years. I wonder how long I can go without a loss in O2 sensitivity... As a matter of maintenance I change the O2 sensor every 4-5 years anyway. The one wire sensors are so cheap anymore.

SKFengineer

I feel like I'm coming up flat on input here, is there a different sub-forum or site that might be able to help give a more detailed description of how the O2 sensor will react.

Thanks

ntomsheck

iTrader: (1)

There's not a definitive answer, because of the chemistry involved in tetraethyllead.

If TEL is burned completely, a fine mist of elemental lead is sprayed from the engine. In the presence of excess oxygen, it will oxidize to lead oxide. This can happen in the combustion chamber itself, or at any point in the exhaust pipe. Where it happens is temperature dependent, oxygen concentration dependent, and exhaust velocity dependent. Elemental lead conducts electricty, which can short the sensor. Lead oxide doesn't conduct electricty, but could just block it. You may have a mix of unknown proportions of either depositing on the o2 sensor. How much deposits on/in the oxygen sensor depends on oxygen sensor placement, whether it's recessed or not, number of vents on the head, etc. With this amount of variables, the scientific term is 'crap-shoot'.

Maybe have a spare, untainted sensor you can use as a reference and then test yours after each race weekend against it. The problem with oxygen sensors is that they don't fail either off or on, but rather the readings just get skewed in one direction or another.

SKFengineer

Thanks for the replies... So the short answer (which I sort of knew but didn't want to admit to myself) is "yes", leaded fuel can harm the O2 sensor. The rate at which this occurs can vary but the message is user beware.

TTOP350

iTrader: (8)

The 02 sensor will eventually get lazy or slow from being coated, if you're seeing cross counts and they are still rapid, you're good.

I run no lead 110 in my 11.5-1 motor and we both like it.