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JoeCee

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If you want to prioritize cat longevity over performance I think I’d run stock cats with 8 psi or less, 19-20 deg timing, and super rich at wot like .72-.73. Have cot drop it to around .68 if it will do it without misfires.
TY! Much appreciated!
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Joshinator99

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If you want to prioritize cat longevity over performance I think I’d run stock cats with 8 psi or less, 19-20 deg timing, and super rich at wot like .72-.73. Have cot drop it to around .68 if it will do it without misfires.
That’s too rich for a DI motor in my humble opinion. I’ve found .82 to be very safe for DI engines and of course you richen a bit more under COT. Guys who shut COT off usually have the biggest cat melting issues (obviously lol).
 

engineermike

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The idea of running it at .72-.73 is to reduce thermal shock and keep the egt cool as long as possible before cot kicks in. It also allows a little more timing that cools egt further.
 

Joshinator99

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The idea of running it at .72-.73 is to reduce thermal shock and keep the egt cool as long as possible before cot kicks in. It also allows a little more timing that cools egt further.
Interesting, thanks Mike.
 

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engineermike

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5 sets of gt500 cats on eBay currently if anyone wants to convert over.
 

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22Coyoti

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Note the 5.2 manifolds do not mate to coyote heads.
How Challenging is it to get it to work? I really wanted to leave the stock headers and cats and the reasoning is kinda making me want to stay away from boost even tho I only want to be conservative and use whipples tune. If i were to do it I would do the gt500 cats
 

engineermike

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In hindsight I think I would try a gen1 drivers side header. It has a 2-bolt flange already and will bolt to the coyote head. The flange is clocked 90 deg out, so a short adapter would be needed but I think this would be easier and better than modifying a stock gen2/3 header to accept a 2-bolt flange.
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