In addition to piston crown which will fail catastrophically, the
turbine in turbo
will erode, slowly erasing the turbine blades. You hope it's slow.
breaking a turbine
blade usually eats the entire turbo. Thank god it rarely happens.
I have forgotten what the suggested max was on the Rayjay 400F I used. I
can
look it up if it's important.
I think it was 1700. When I ran 1800, I didn't notice problem with the
turbine, but
I didn't have a Pro. look at it. Only made two runs at 15 PSIG.
Also, with a turbo, EGT at one port 6" from the valve seat will be lower
than just
after the primary pipes merge. Significantly lower. On a dyno with the
lights out
and at night, this becomes very apparent. On a turbo Offy, the primary's
are a nice
bright read until they merge. At that point the secondary pipe becomes
almost white
hot! It drips down to bright all the way to the turbine inlet. The
turbine housing is
red but not so bright and the pipe out of the turbo is barely red hot.
The blend of gasoline is important when you have more than about 10 PSIG
boost.
ERC E8 has additives that carry more heat out of the combustion chamber than
normal racing gas. The additive isn't cheap.
Bryan
Karl Payne wrote:
> Totally agree with the piston-before-valve comment. Ask Rick Byrnes how his
> pistons looked after a half-dozen passes with the monster turbo boost he was
> running. The weak link in the thermal system is the piston crown, not the
> valve material.
> I think I heard Rick say that once...
>
> Karl P.
>
>
> Skip,
>
> RE: 1750F EGT
>
> My engineering book shows that the melting temperature of Aluminum (ie.
> pistons) is 1250F
> Iconnel is 2450F
> Stainless Steel is 2750F
>
> I think I'd worry more about the pistons than the valves.
>
> I know the pistons are an alloy of Aluminun, but still.....
>
> JG
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