Does manifold discoloration mean too high exhaust gas temps?

[gruff511]

So im looking for some info on tuning e85. Mainly my question is; is what does it mean for the exhaust/turbo manifold to get a purplish burn color too it? does it mean exhaust gas temps are too high? im running a stainless steel manifold and after a couple days of driving its starting to get this purple color to it. It looks like a too hot burnt look so it made me wonder if im running too much timing or not enough timing. Id like to add i will be getting an egt gauge soon to monitor that.

[mrx79]

Guessing EGT's from Manifold color is not very accurate. It's normal for every saintless steel manifold to change color over time as the material went thru some heat cycles.
It starts from plain over some golden/purple color and after a few weeks they become gray/brownish (at least all mine did with EGT's in ok regions).

If you are worried, get yourself a good EGT gauge, but if your ignition timing is not too far off and AFRs are in the ballpark and you are not suffering from a clogged cat or tiny turbine, EGTs are in acceptable regions most of the time.

Best regards

[Yves]

Can you tune the ignition timing based on the egt's ?

[mrx79]

Not realy, there are some guy's who say that you can see knock on EGT's but that's not what i experienced. There are more reliable way's to determine knock.
For me, EGT's are some kind of safety measurement. I never tune after EGT, unless i have to on very restricted setup's to prevent component failure due to temperature.
On cheap manifolds/turbo's looking for low temp's might be resonable, but if you work with professional equipment, EGT's most likely will not be a concern.