Catalytic converters and E85

[wparsons]

Originally Posted by zooki

If I'm not mistaken I think E85 burns cooler than normal gasoline. I think it would actually take longer to heat up the converters to optimum temperature. But I could be mistaken.

Originally Posted by unsurety

You're right in a way, it does have a cooling effect. It lower IATs if I'm not mistaken.

The problem he described is the deposits clump up. If it doesn't clog the cat, it forms a mass that absorbs more heat and takes longer to dissipate heat. And so the HFC turns into a straight pipe.

How hot it burns is very different from how much it cools IAT's by evaporating. EGT's will be driven more by a/f ratio and timing. Running less timing generally raises EGT's and since running e85 lets you run more timing advance you'll probably see similar or lower EGT's on e85. Plus you run e85 richer which also has a cooling effect on EGT's (assuming it's not so rich it's still burning on the way out of the head).