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940 Soft Turbo - how many different specs ?


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#21
glock19

Posted 04 March 2005 - 11:10 PM

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Better still, SMS me @ 016-455-0085

#22
jaylee

Posted 05 March 2005 - 03:15 PM

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Hi glock19,

Have you given me the correct mobile number?

#23
glock19

Posted 05 March 2005 - 10:15 PM

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Jaylee,

I called the potential and he said he's not ready to let go of his 240
yet, so I guess the meeting tomorrow would not be necessary. I'll sms you
a note too after this.

#24
sawai1

Posted 10 March 2005 - 08:49 AM

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vol940,

could i say maintaining a s/t is cheaper than the turbo?...can put blow
valve or not in s/t hah?Big Smile

#25
vol940

Posted 10 March 2005 - 05:13 PM

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sawai1,

The answers could be "NO" but never cheaper. Preventive maintenance
remains at the same order. Both are turbocharges, the only difference is
the Aspect Ratio.

Low Pressure Turbo has low Aspect Ratio (around 0.41)- less quantity of
compressed air, allowing spool-up at low rpm (2000), descreasing the
turbo lag. While High Pressure Turbo has higher Aspect Ratio (up to 0.63
or more at some extent) - higher quantity of compressed air, spool-up
beyond 3500 RPM or above, increasing turbo lag.

The reason behind most turbo failures is due to a great amount of built
up crystalized carbon, or"coking". Next cause is poor balance
(unbalance), and the rest are blade erosion on the turbine blades, blade
strike and exhaust chemical build-up on the turbine blades.

The coking occurs in varying degrees at primarily two locations. In most
Turbo Garretts, it usually occurs inside the bearing housing, or center
section, and inhibits oil flow to the hot side bushing. In most Turbo
Mitsubishis it usually occurs behind the heat shield on the turbine side
and eventually presses the shield against the back of the blades and
machining material of the turbine away rendering it unbalanced (poor
balance) or causing it to sieze.

For driving habits less than 3500 rpm all the time, the carbon built up
at the bearings and connecting shaft turbine-compressor for LPT will be
relatively faster than HPT. Hence, less (shorter) service life time.
Unless you have a good preventive maintenance. You see why the the answer
could be NO and never cheaper.

1. The best oils for turbocharge are full synthetics for reducing this
problem however the combustion chamber chemicals suspended in older
synthetic will release from the oil at very high temps and "coke" as
well. The best way is frequent changes, synthetic or petroleum based, to
ensure that the oil in the crankcase has a fresh additive package at all
times.(The additives are what inhibits wear, evaporation, shear, etc).

2. Spend few minutes of idle after starting and before switching off the
engine. Why ? ... In the first few seconds after starting (even after the
oil warning light is off!) the oil pressure is lower, and fresh oil may
not have reached the turbo yet - and if you race the engine, the turbo
will spin fast with insufficient oiling of the bearing - not good -
better to wait a couple of minutes.
The reason few minutes cool down period was required is that after a long
drive they could be glowing red! This is very hot. And it can burn the
oil. This does not cause a problem while the car is running, because the
oil pump keep recirculating the oil around, so it doesn't stay in the
turbo long enough to burn. The problem is that as soon as you shut down
the engine, the oil pump stops. If the turbo is still spinning, it has no
pressurized lubricating oil. The oil that sits in the turbo stays there
and can burn and coke. If solid sludge particles form in the turbo
bearing (which is an oil bearing), they can score the bearing journals -
kind of like your very own grinding machine inside the turbo. Even you
have also water cooler for your turbo - it is better to cool down the
turbo for a few minutes.

Regarding the Blow Off Valve (BOV), there are two type : "Close System"
and "Open System". Most LPT (not always) use Close System and Open System
(external BOV) for HPT (also not always). Close System is a system
allowing pressurized air returned to the turbo compressor inlet for
reuse - the device called as "Compressor Bypass Valve (CBV)". A CBV is
found on many "OEM" original engine manufactured EFI turbo systems.

Blow-off valve (BOV) - Open System is a system to vent the pressurised
air directly to atmosphere (and wooshtssh.............life is good and
running well).

Why vent the pressure? - Primary reason is to reduce strain on the
compressor turbine wheel due to compressor surge, allowing the turbine to
continue spinning freely. When back on the throttle, boost pressure
qy tint ßsawai1,

The answers could be "NO" but never cheaper. Preventive maintenance
remains at the same order. Both are turbocharges, the only difference is
the Aspect Ratio.

Low Pressure Turbo has low Aspect Ratio (around 0.41)- less quantity of
compressed air, allowing spool-up at low rpm (2000), descreasing the
turbo lag. While High Pressure Turbo has higher Aspect Ratio (up to 0.63
or more at some extent) - higher quantity of compressed

#26
sawai1

Posted 10 March 2005 - 05:24 PM

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vol940,

wow....thnxs for the long explanation...u must be really good. now i know
wat to expect maintaning a 940...By the way who is Turbo Lim?...i m new in
here.

cheers.

#27
cheahcl

Posted 10 March 2005 - 07:50 PM

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wahahhaa
something to ponder... AR.63 for HPT? sure ah..... in volvo's case i
think its all AR.48 or so. the diff between LPT and HPT is the boost
level lah i think not the turbos! AR.60 AKA 60 trim is considered big in
a volvo!

as for BOV, volvo runs a stock BOV also known as the CBV - compressor
bypass valve. what vol940 is saying about the OPEN sytem is actually
VENTING TO THE AIR and the CLOSE system is VENTING BACK into the system.
since volvos run air mass meters(AMM/MAF) and NOT manifold pressure meters
(MAP), if you vent the system's air into the atmosphere, the ECU cannot
calculate for the missing air and thus with the ECU thinking there is
still the SAME amount of air, it will give the same amount of fuel
instead of the lesser required bcoz of less air(after venting out). thus
the car runs rich and most of the time dies. then u gotto start the car
again... veli MALU one ahhh! Shock

therefore, if u think BOV sound is sweet, you can always get GFB or
GREDDY TYPE-S. GFB allows u to tune how much air goes BACK into the
system and how much air vents out (SO U GET A PSHhhhhh). with this
function u can tune the BOV till the car doesn't die when the air is
released into the atmosphere. as for greddy, u can choose to plumb back
the air into your system (i think still got a little pshhhhh sound) or u
can vent it out to the atmosphere and risk ur car dying like running
other BOVs.

last but not least, remember to SEAL OFF your stock BOV aka CBV! so that
all the air gets out thru ur new BOV Wink

#28
vol940

Posted 10 March 2005 - 10:12 PM

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sawai1,

Turbo Lim is very famous for volvo owners in this forum and he is very
expert in mods and upgrading your brick to get more HP.

Turbo Lim, hope that you don't mind me to give your contact number for
the benefit of sawai1, thanks before. HP No. : 019-3309426.

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#29
vol940

Posted 10 March 2005 - 10:23 PM

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cheahcl,

Waooow ... you are very informed on sweet sound`s BOV, wan?. What BOV did
you use?, or just maintaining your stock CBV ?.

BTW, thanks for your more elaborated explanation for the benefit of our
bro`s sawai1.

Only S40T4 uses MHI TD04L-12-8.5cm2 or AR-0.61

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