Exhaust question for TD5

Free flowing the exhaust only makes a difference to the outlet side of the turbo. The turbo is the first point of heatloss in exhaust temps. Depending on turbo and exhaust size and other factors such as load, you can register as much as a 200C drop over the turbine alone rendering what you are reading grossly inaccurate from a dump pipe mounted sensor compared to the actual EGT figure at the turbine inlet.

EGT is combustion temp, not the temperature in the exhaust pipe.




Using Capitals, the difference between helping your Uncle Jack off a horse or helping your uncle jack off a horse...

ummmm I didnt know the TD5 had a catalytic converter. I'm sure mine didnt. It had a bloody great materess sized muffler in the middle. There was nothing forward of that and only the resonator behind.

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Originally Posted by ramblingboy42

ummmm I didnt know the TD5 had a catalytic converter. I'm sure mine didnt. It had a bloody great materess sized muffler in the middle. There was nothing forward of that and only the resonator behind.

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only latter td5's had cats.

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Originally Posted by twr7cx

True only to a point. if the exhaust gases are sitting there not flowing out, then there's additional heat up there. Having the exhaust gases flowing away quicker will reduce the EGT's (however, they can only reduce them so much). Try it for yourself - disconnect your exhaust system and watch the drop. QUOTE]

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Don't confuse overall engine temps with Combustion temps and exhaust gas temps.
Exhaust temps post combustion will read lower with a free flowing exhaust. But this isnt the point of the EGT probe or temp monitoring.
This is merely a result of hot gases with a larger volume to expand and cool prior to influencing the probe. It is no different to mounting the probe at the rear of the pipe and noting the temp difference. If we were only interested in the ACTUAL Exhaust Gas Temperature, rather than what these temps are actually influenced by, then any big sucker exhaust is the answer.

With this theory you could liquid cool the exhaust and have sub 100 EGT readings and apparently have made gains, yet in reality, no performance increase nor change in actual combustion temps.


As previously posted EGT's are a direct function of combustion. The EGT's happen to be the easiest method for the average punter to monitor the combustion temps. What ever is modified post combustion may help or impair turbo spool, fuel consumption or performeance.

If dropping meaningful EGT was that simple, Bigger I/Coolers and boost mods wouldnt be as necessary.


cheers