100 Octane unleaded track gas
 

Two laps after filling my 2.7 S build with track gas, the engine lost power and went lean. Anyway the gas itself could cause that condition? That is the last thing I changed.

Thanks
John

I’ve heard of race gas being oxygenated to make more power but it causes a different fuel need/stoichiometric balance kind of lol methanol or ethanol fuels.

On a car that’s already leaned out for max power N/A, you’d likely lose power.

I normally run rich
 

It was raining very hard so I suspected water in the fuel. But I have a screw canister Fuel filter on the firewall near the engine so I drained that into a jug with another couple of pints but I found no water.


I pulled the jets looking for debris but They were all clean.

I pulled the top set of plugs and found cylinder 3 and 5 lean, all others rich or perfect


If I had a failing fuel pump I would expect a lean condition in all cylinders, but I did not find that.


I still suspect the gas but I don't know why....

Since I had a lean condition on both sides of the engine, I doubt it was a sticking float or needle valve.

What else could cause a lean condition. It went seriously lean, pegged the AF meter in the red and immediate loss of power.

Thanks, I suppose the easiest test would be to drain the tank, but at 8.75 a gallon I hate to run in my lawn tractor!

I've known of engine failures due to bad pump gas, but I'd not suspect race fuel from a track of that.

You might do a specific gravity test on this stuff. General aviation airports test each tanker load of fuel they put into their storage tanks for this and other characteristics. Maybe you could contact a nearby one to see if they would do a test on a sample you bring them?

You might have hit the nail on the head.


https://www.hotrod.com/articles/ctrp-1212-oxygenated-racing-fuels-new-fuel/

If the car had a brain and Fuel Injection it would probably adjust for it, but the old Webers can not adjust on the fly.

Sunoco has a tech page on it. That's what I put in

https://www.sunocoracefuels.com/tech-article/fuel-metering-basics-oxygenated-fuels

Alcohol is pretty hard on some of the parts in the fuel system. And the 100 octane unleaded is 10% ethanol. It could have loosened up some old debris in the tank and plugged up a line or the fuel filter.

This is it I am sure. EXO2 is dyed light orange. That is what is draining out of the car.

Thank you 993 Speedster!

Due to its high oxygen content, Sunoco EXO2 requires a richer air/fuel mixture. Using EXO2 without proper air/fuel mixture changes can lean out your engine. Please consult the stoichiometric air/fuel ratio data in the Technical Details section below. Since non-oxygenated race fuels typically have a stoichiometric air/fuel ratio of 14.6:1 to 15.1:1, you may need to richen your fuel mixture by 10 to 15 percent when using EXO2 depending on the fuel you are currently using.

Your mixture would have to be pretty lean to lose power. Here in the northeast most pump gas has 10% ethanol. At the track most people run it in their street cars including older 911s. I haven’t heard of the ethanol being an issue. Easy to test though - measure your AFR with a wideband O2, or drain the tank and try some of whatever gas you normally use and see if the issue goes away.

The problem was not the ethynol. It is the oxygenation. 10% by weight.

Sunoco has high octane ethynol race fuels and now they have the oxygenated fuels. It is a different mixture. Reading though the links above you can see why they are doing it. But my carbs can not enrichen on the fly and I did not rejet just to run one tank of gas. My guess is the Series cars running this weekend are set up for this fuel. I just happened to be a lucky one to test it on a old 911 engine with Webers. Not knowing what I was really putting in the car.

Its out now, I will have the plugs replaced later today.

Guess what fuel manufacturers commonly use to oxygenate fuel ...

I read the Sunoco link above - they don’t specify.

https://en.m.wikipedia.org/wiki/Oxygenate

Can't tell you, but I bought 3 5 gallon gas cans and drained 15 gallons of the orange fuel out and replaced with standard Sunoco 93 octane pump gas. Car now runs fine. All I know is what I know. Ran well before I put it in, didn't run with it, ran well after I took it out.

Thankfully my engine seems ok. Thanks for the comments.

A casual glance at the SDS reveals the contents.

https://www.sunocoracefuels.com/wp-content/uploads/2017/04/SUNOCO-EXO2_US-SDS_13April2017.pdf

Well there you go. Pretty easy fix.

Yes Sir. Now Who Wants it? Pick Up only -New Tanks Free!

If only fuel injected you'd bump fuel pressure a bit and be on your merry way for the day.

Lean conditions aside running highly oxygenated fuel tends to be corrosive from what I am told. The Sunoco Street 100oct should be good for your application. It has a small amount of alcohol but nothing that should effect your tune.

You don't want that EX02 110 oct anyway. That lead causes all kinds of problems. It's really nasty stuff to breath too.