Before installing EGT gauge . . .

[Noam]

Was wondering if you might know what the normal operating EGT temp. are for the 1.8T?

At what temparture are pistons, rings, valves damage damaged or in danger of being fried??

How much can the exhaust manifold sustain?
Thanks for any input,
Cheers,
Noam.

[Sim]

The turbos are up to 1050C.

[max_torque]

For a turbo charged production engine typical maximum pre-turbine temperature will be set to betweem 940 and 975 degC. I can't remember if the 1.8T has the Bosch closed loop EGT control fitted (small black box on end of braided wire coming from pre-turbine thermocouple, def fitted to V6 twin turbo engine in old S4. sensor range between 905 and 995 degC)

Things like exhaust manifolds are most likely to fail due to stress build up and localised work hardening when they are subject to repeated temperature cycles. but never the less, much over 980 degC will start to weaken material properties for a cast manifold

Excessive EGT does not tend to damage pistons and rings as they are cooled, but exhaust valves will fail at excessive temps (>850 to 900degC)(actually less temp at exhaust valve due to cyclic nature of cylinder events, whereas turbo is always getting a blast of hot gas from each cylinder so it runs hotter)

On a competition enigine you can push these limits at the expense of durability and requiring higher grade materials, ie Myram 247 shafted turbo charger for antilag applications will withstand approx 1050 to 1100 degC for short periods, and Inconel stainless steel manifolds are good for 1100degC

[Noam]

So wouldn't a chipped Ibiza 20vt run anywhere in excess of 900c, hence perhaps damaging the exhaust valves?

What would be the heat in c at each stage of the combustion cycle, through to the turbo, and ending at the CAT approximately??

Thanks,
Noam.

[Sim]

I dont think that a stock but chipped beezer would fail at all ;).

[max_torque]

The problem with trying to work out how hot the exhaust valves get is that you can't measure it accurately. The actual gas temp is not important, it's how hot the actual valve gets, and the only way to determine that is to run several engines at different EGT's and then strip out the valve and have them metalurgically sectioned to determine how the material properties have changed and hence how hot they ran and if they are likely to fail at this temp.

Put a thermocouple in an exhaust port and it will read typically 100degC short of the actual gas temp because each exhaust event is cyclic, between which the Tc will cool.

Personnaly i would not map a turbo engine to run beyond 975 degC measured pre turbine entry, remembering that if inlet temps go up then exhaust temps follow, ie depends on how efficient your intercooler is etc.

if the 1.8T has the Bosch EGT control box fitted this will control max temp to typically 940 DegC.

[max_torque]

Maximum combustion temperature during the burn phase of the power cycle for a 4 stroke engine will approach 2000 DegC, this falls to say 900deg as it exits the cylinder via the exhaust port, due to the expansion of the gas and the heat removed as work from the piston.

you can see why the cooling system is important, as alluminium melts at 1300degC, without thay water circulating your engine would be scrap in a very short time!

[Noam]

Max_torque . .
You say that temp. between 850-900 degC can damage the exhaust valves.
But then you say that a turboed engine experiences around 900 degC after heat dissipiates at the exhaust port - so wouldn't that be too much for the exhaust valves??

Another thing, can the EGT gauge really monitor safe temp. at the exhaust port, seeing as gasses have such a quick heat dissipiation at each stage of their travel through the engine?

It is pretty amazing how these engines manage these kind of tempertaures!!!

[max_torque]

exhaust port gas temp is above 900 degC when exhaust valve is open, falling rapidly to below 600 degC for the rest of the time. typically a high grade exhaust valve will withstand 800 degC metal temperature within the valve stem / head itself

I would put an EGT gauge sensor in the exhaust manifold collector after all the cylinders have joined, and ideally first measure the peak temperature here with a standard car, then decide how much beyond this (if any) you want to risk going)

If you say run in 2nd gear on a rolling road at WOT peak power rpm (or against brakes on road) you should see the temps climb then stabilise after 30secs or so. record this value and use it as basis for further tuning, assuming that the std production engine is durable you know that your engine should be ok if you do not exceed this temp. (assuming you do not rev engine higher or fit a more agressive cam that will mechanically load valves more than std)

[Noam]

So let me see if I got this right:)

the temp. of the gasses passing on their way to the turbo are at 600 degC aprox.?
What's the temp. of the compressed air leaving the turbo towards the intercooler?

[ibizacupra]

How hot a day is it?

[max_torque]

Compressor exit air temp depends on 3 things

1) how hot the air is entering the compressor
2) what the compressor pressure ratio is (outlet pressure / inlet pressure)
3) how efficient the compressor is

But assuming a 15degC day at 1 bar boost and with a typical 70% efficiency compressor the exit air temp will be 110.9 degC

[ibizacupra]

Originally posted by max_torque
But assuming a 15degC day at 1 bar boost and with a typical 70% efficiency compressor the exit air temp will be 110.9 degC

Blimey!

Blummin hot...

Intercooler anyone? :D

Bill

[Sim]

"Intercooler anyone?"

me. soon.