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Torque » Torque OBD ECU Scanner » Torque Discussion / Ideas » Diesel Boost / Vacuum

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Author Topic: Diesel Boost / Vacuum
jmelford
Member
Posts: 3
Post Diesel Boost is Vacuum @ Idle
on: August 2, 2018 (GMT)

Hi,
Loving Torque Pro, running on my 2009 Toyota Hilux (aka Surf, Tacoma) with 3ltr diesel 1KD-FTV engine. Data being fed via SCANTool LX bluetooth.

Wondering why Turbo boost comes up negative (vacuum) at idle and decelerating using the MAP (default) Boost setting.

@ idle its sitting on 7.7 psi vacuum.
Manifold is 11 psi
MAF is 15 g/s
bara is 14.4

Torque is using my profile, 3ltr diesel engine, 0 boost adjust, 85% VE.
Under load the boost seems about right – peaking on road around 10 – 11psi

If i change to MAF or ALT Boost setting, it idles at 0 PSI boost but hits 16 – 18 PSI on road driving which feels too high.

Any ideas?
thanks

Capp777
Member
Posts: 2861
Post Re: Diesel Boost / Vacuum
on: August 2, 2018 (GMT)

What does your boost read KOEO? Does it
read zero?

I thought the Turbo Boost/Vacuum gauge
read vacuum in inHg.

Your baro of 14.4 leads me to believe that
you are not at sea level?

jmelford
Member
Posts: 3
Post Re: Diesel Boost / Vacuum
on: August 2, 2018 (GMT)

Never thought to look at KOEO (silly me)

Boost is floating around 5.6 – 6.0 inHg (vacuum), and yes not PSI when in vacuum. The Manifold is also around 11 psi at KOEO if that means anything.

I’m about 180m above sea level

Capp777
Member
Posts: 2861
Post Re: Diesel Boost / Vacuum
on: August 2, 2018 (GMT)

Your MAP sensor is in absolute pressure where
sea level is typically 14.7. Your 11 PsiA reading
may be due to altitude, weather or a faulty
sensor. With KOEO the reading should match
atmospheric conditions where you live.

Try changing your boost adjust setting to achieve
a zero boost reading with KOEO.

If my math is correct…

11 PsiA = 75.8 kPaA

which is equivalent to ~2400 meters elevation
based upon my calculations.

14.4 PsiA = 99.3 kPaA (Baro seems more realistic
for an elevation of 180 meters).

Sea level under standard conditions 101.325 kPaA.

Doubt weather is contributing to your low
readings.

jmelford
Member
Posts: 3
Post Re: Diesel Boost / Vacuum
on: August 3, 2018 (GMT)

Coded the boost offset by difference between baro and manifold pressures at KOEO (roughly 4 psi) so it’s reading zero, and seems right amount of boost while driving now.
A few forums report difference between inlet pressure and MAF baro is not unheard of in my engine. As long as the ECU doesn’t mind, I don’t mind :-)

Thanks for help.

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