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Hot/cold Boost Pressure Difference


Vrdesign

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  • Member For: 10y 2m 28d

Hi,

Ive been logging some boost pressures at different ambient temps, also I hooked up a second boost gauge on the wastegate line out of the turbo to see the pressure drop accros the whole system.

14 psi Manifold, 18 psi Turbo @ 30 deg C

16 psi Manifold, 20 psi Turbo @ 20 deg C (tune was done at this temp, 340 rwkw)

17 psi Manifold, 21 psi Turbo @ 15 deg C

Are other people seeing these sorts of numbers?

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  • Member For: 11y 2m 21d
  • Gender: Male
  • Location: Wollongong

I like data logging.....Maybe someone more knowledgeable could chime in,,,,.....is the variation in boost pressure with the change of temperature the ecu adjusting boost and timing to suit intake air temps when tuned in closed loop???

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  • Member For: 16y 4m 4d
  • Gender: Male
  • Location: Probably above atmospheric pressure

Good question, I imagine if humidity was constant that 15PSI is the same volume of air regardless of temp...so ECU might be allowing more power in colder conditions.

The number of years I've been reading here you'd think I'd know by now, hahaha.

Also, good to see someone logging it.

Edited by -Stever-
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  • Member For: 10y 2m 28d

It defiantly seems like safety built into the tune as the compressor efficiency seems to change predictably with temp, I'm not sure what else could cause this.

Also, Is a 4 psi pressure drop across the system a typical result? 2.5 hot side, plaz1000, 3" cold side into std plenum

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  • Member For: 18y 3m 11d
  • Gender: Male
  • Location: North West Hot Hell,VIC

Did this quite a few years ago on the stock system and iirc came up with the same results, 4 psi drop across the system.

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  • Member For: 10y 11m 26d
  • Gender: Male
  • Location: Liverpool

There are a few variables when I comes to boost, mainly if it was tuned in closed loop or open loop... Open loop is just like a bleed valve that can be adjusted for a different RPM, this is quite commonly used and you will see variances in boost pressure through the gears, but I didn't really think that IAT came into play... Closed loop is a PI based system where you command a boost level and the pcm will try to target this value all the time

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