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Old 10-18-2004, 12:29 PM   #4
Scooby Specialist
Member#: 40501
Join Date: Jul 2003
Location: Paris, FR
2005 Decathalon 21sp
One WheelSeanPower


The Subaru WRC car hits something ridiculous like 3.5bar of boost at less than 2500 rpm. Lots of diesels max out boost (which might well be 4 or 5bar+) below 2000rpm (hell, 1200 in the case of Semis) and fall off from there.

I think what the Scooby Guru must have meant is that the stock EJ205 is likely to have breathing issues down there, leading to det, pre-ignition or something else ranging from mildly to massively catastrophic.

The EJ205 also has cute, cast, pencil-thin rods that will happily snap if cylinder pressures are too extreme. If you got 3.5bar of boost at 2500rpm in an EJ205, you would no longer have moving pistons. You would have a box of snapped aluminum.

Now, if it was a specific situation, it's very possible that the poster was referring to surge at a very high PR but low flow situation, or the added det risk caused by running way, way out of the efficiency range of a given turbo. But unless the poster you refer to elaborates, we're just guessing.

If you have sufficient force on the turbine and a sufficiently efficient compressor, combined with a strong engine, I don't think low boost would ever be bad.

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