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Old 06-07-2010, 07:11 PM   #21 (permalink)
Basjoos Wannabe
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I would be willing to blame a faulty boost gauge on that one.

IIRC EGT indicates temperature of the exhaust. I know, that's making it awful simplistic, lol. But for a high EGT, think lots of air and lot of fuel that is kept close to stoichiometric, whatever that would be for a diesel. One method some hotrodders use on the dragstrip with their diesels is turn up the fuel: it creates a ton of smoke, but that extra fuel lowers the EGT and keeps it in the happy place. Keep the engine from smoking and it requires a computer control to keep it close to the burn off the manifold temp.

Higher boost would raise the egt, especially if not accompanied with increased fuel injection. I'm no expert, so correct me if I'm wrong.

I do know higher EGTs spell death for a diesel engine, so it's best to avoid that scenario.

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Originally Posted by jamesqf View Post
I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
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Old 09-21-2010, 03:52 AM   #22 (permalink)
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I recently read an article on start&stop systems (which are expected to be present in 70% of new cars in Europe within a few years) and one of the problems to be overcome (beside the battery and starter) was the turbo. Since start/stop systems are usually added to "eco" versions of existing models, they are usually paired with an already efficient turbodiesel. To overcome the problem, turbines are now built to withstand being shut down while hot, much better than a few years ago. One company (Mitsubishi, I think) has an extra pump for lubing the turbo after shutdown.
e·co·mod·ding: the art of turning vehicles into what they should be

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Piwoslaw's Peugeot 307sw modding thread

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Old 09-21-2010, 05:32 PM   #23 (permalink)
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i take it my petrol turbo would see similar issues regarding fried turbos or seals..
The low pressure turbo setup on my saab is weird as it drives like a tdi.. Lots of low end boost!

What is a guideline % increase from engine OFF cruising vs engine ON?
I doubt it'd cover the £600+ for a new turbo..
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Old 09-21-2010, 05:51 PM   #24 (permalink)
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Originally Posted by ShadeTreeMech View Post
Higher boost would raise the egt, especially if not accompanied with increased fuel injection. I'm no expert, so correct me if I'm wrong.

I do know higher EGTs spell death for a diesel engine, so it's best to avoid that scenario.
Higher boost lowers EGTs when not accompanied with increased fuel. The reason is that there is more air to heat in the cylinder with the same amount of fuel. Note that a diesel doesn't get hot when running lean like a gas engine.

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