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Dominic:

Do this. Place a probe 3" from the exhaust flange, then place another one a foot from the exhaust flange (same cylinder with no other exhaust stream joining in). The one further away will read lower. Why? The gas is expanding and cooling as it flows down the pipe. The TIT reading is higher because the TIT is getting more pulses of exhaust gas per 720 cycle. As a result it has less time to cool between hot pulses. It READS higher. It is not actually hotter. You don't really think the gas gets hotter the further it gets from the exhaust valve, do you?

Walter

On Jul 9, 2007, at 12:39 PM, Dominic V Crain wrote:

“The TIT GAS is cooler than the exhaust GAS... it's further down the line... it's had time to cool more.”

HUH?

Now- let’s see.

TIT’s are cooler than EGT’s?

Hmm.

So, on that premise, the engine is putting more energy into the gas than it’s extracting.

Which would mean the prop is driving the engine.

Nah!

I reckon the old theory still works.

Burn the gas, measure the TIT, punch the expanding gas through the turbine. Pull out the heat energy to drive the compressor then the prop. Measure the EGT, and PRESTO, the EGT is COOLER that the TIT.

Guaranteed. Or Allison’s rear end doesn’t point backwards!

Regards

Dom Crain

VH-CZJ