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Old 14th February 2006, 16:42   #1
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Default Scorpio boost pressure question

Does anyone know how much boost the Scorpio CRDe is running?
Does it have a BOV ?
Is it possible to fix a boost gauge?

Thanx & regards
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Old 14th February 2006, 17:02   #2
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boost pressure - do you mean the rail pressure??? if yes, it is 1600 bar.

BOV - is this Blow Off Valve??? if yes, may i know the reason for you to fix one, because i own a crde as well.
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Old 14th February 2006, 19:02   #3
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Tifosi, he means bosst pressure as in the case of the turbo. I know the non CRDE runs 1.4 to 1.6 bar which is about 22 to 23 Psi. i know it sounds a lot but I have verified this with Turbo Energy who make the turbos for the Scorpio. I also know that the CRDE runs a slightly smaller tubo than the Non CRDE version.

The scorpio has an EGR valve - Exhaust gas recirculation which is bascially a BOV. But you don't get to hear the Pshhh sound cause it is a recirculating type.

Yes you can fix a boost gauge. You will need a simple "T" to tap into the pressure line.

Hope this helps.
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Old 14th February 2006, 19:29   #4
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Yes,A Boost guage can be fit in any/most of the turbo engines (petrol/Diesel) .

@Sideways: Does ur scorpio have one??
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Old 14th February 2006, 20:15   #5
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@Sideways, 22 psi turbo boost ? is it verified ?

As far as I know the CRDe runs Borg (previously kkk) K03 turbo.

egr valve ? how does this help? when you get off the throttle, does this makes the exhaust gases to bypass the turbo fan?
http://www.misterfixit.com/egrvalve.htm if you read through this link, EGR valve is there on the engines for some other reason.

how can this work so to replace a BOV ? Can you pls explain ?

Thanx
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Old 14th February 2006, 20:18   #6
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Yes,Renamo.

We're sure its 22 psi.
Infact, we were searching for a Scorpio's waste-gate actuator when the one in the EVO-VI gave up. The EVO was spooling somewhere around 18-22 psi.
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Old 14th February 2006, 20:33   #7
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BOV is only for petrol turbos. Diesels dont need a BOV because they have no throttle plate.

EGR is exhuast gas recirculation. Its used to reduce emissions.

You can Tee in the boost gauge into the intake manifold.
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Old 14th February 2006, 21:39   #8
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somewhere i hv read that bhp doubles when the boost is above 14 psi.

Now if scorpio does run 22 psi boost, doesnt it mean, take out the boost from the equation then you have a 60 bhp (roughly) motor ?

I am also getting little confused because sideways says that EGR is kind of BOV, and Mpower says no BOV needed for diesel..

no flaming, i just want to learn some more...

thanx

Last edited by renamo : 14th February 2006 at 21:41.
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Old 15th February 2006, 02:48   #9
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Quote:
Originally Posted by renamo

I am also getting little confused because sideways says that EGR is kind of BOV, and Mpower says no BOV needed for diesel..

no flaming, i just want to learn some more...

thanx
EGR is used to circulate the exhaust gas back to the engine to reduce the rate of combustion and hence reduce NOX emission. Higher rate of combustion produces more NOX and at low speed you don't need the full power of engine and thus EGR is used.


BOV is used to blow off the air from air manifold to prevent surge when you suddenly stop or reduce speed. When the air consumption is reduced (when you suddenly stop) the turbo will cross the surge line because the turbo will continue to run due to inertia and also air mass will continue to flow. In simple terms it will set up huge air flow pulsations and will
damage the turbo or air intake elements of the engine. Blow off valve simply maintains the air flow above surge line by releasing the pressure.
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Old 15th February 2006, 04:04   #10
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Quote:
Originally Posted by jat
BOV is used to blow off the air from air manifold to prevent surge when you suddenly stop or reduce speed. When the air consumption is reduced (when you suddenly stop) the turbo will cross the surge line because the turbo will continue to run due to inertia and also air mass will continue to flow.
The air consumption is not reduced when you suddenly reduce load in a diesel. Its the fuel flow is reduced. THe air continues to flow causing a lean mixture.

Regarding NOx, it produced at high temperatures. Using EGR reduces the combustion temperatures and hence Nox.

Last edited by Mpower : 15th February 2006 at 04:05.
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Old 15th February 2006, 04:47   #11
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Wink Confusion?? May be my posting technique is not right!

Quote:
Originally Posted by Mpower
The air consumption is not reduced when you suddenly reduce load in a diesel. Its the fuel flow is reduced. THe air continues to flow causing a lean mixture.

Regarding NOx, it produced at high temperatures. Using EGR reduces the combustion temperatures and hence Nox.
You reduce speed by reducing fuel supply. But when engine rpm comes down, the air flow through engine has reduced that is consumption is reduced although due to inertia of the mass of air as well as the turbo inertia air flow may be higher than the required air. Now if you look at any turbo H-Q map, you will find that for a given rpm, the air pressure increases with the increases in air flow (positive slope - gives unstable operation of turbo) upto a certain point and then developed air pressue starts to reduce with the increase in air flow (negative slope - required for stable operation of turbo). The point at which the slope changes is called surge point and if you plot for different rpms and join the surge point, you will get a surge line. Modern turbos are designed to operate as close to this surge line (they remain on the right hand side) to get maximum efficiency and best perfomance but then they are very delicate and can be upset from stable operation very easily. Now when the air flow is right of surge line, the turbo is operating dynamically in stable condition. The moment it shifts to left side of the curve, the increase in flow will create a further increase in pressure and thus will continue to increase flow till it just comes to surge point. Once it comes to surge point, the air pressue reduces immediately after the blower. This will cause the reversal of air flow in the air stream. Which will again cause pressure to build up immediately after blower and again the air flow is reversed towards the engine. This reversal set up pressure pulsation and can be heard as high pitch hammering noise in smaller high speed engines or heavy hammering noise in slow speed engines. These surgings can damage the turbocharger or just blow up the inlet air manifold in extreme conditions. This can be set up when the engine speed is rapidly reduced, intercooler is chocked really bad, something is blocking air flow in air manifold, leaking air intake valve etc etc.


Rate of combustion decides the temperature produced. In gas welding, acetylene is burnt at a very high rate (oxygen is used instead of air) produces very high temperature but same gas burnt by many road side vendors for lighting purpose or LPG burnt in your home at slow rate does not produce the high temperature to melt the metals.

High rate of combustion is used in engines to produce high combustion pressures to higher thermal efficiencies and that is why in diesel engines, the fuel pressure has been increasing to get higher rate of combustion (you burn more fuel in less time). With EGR, although your fuel amount is same, but it continues to burn at a slower rate due to less oxygen available. Hence the temperature produced is lower.

I hope this clarifies your doubt.

Sorry for creating confusion.
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Old 15th February 2006, 05:50   #12
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Quote:
Originally Posted by jat
You reduce speed by reducing fuel supply. But when engine rpm comes down, the air flow through engine has reduced that is consumption is reduced although due to inertia of the mass of air as well as the turbo inertia air flow may be higher than the required air.
Jat, you are right about the compressor and that it should always operate to the right of the surge line, but the point I am trying to make is that there is no cause for surge when the foot is lifted off the throttle. The excess air simply flows through the engine. The amount of air dosent matter in a diesel because its the amount of fuel that determines the torque produced.

The bottom line is that diesels dont have a BOV, surge or no-surge. I suggest you get hold of a service manual and see for yourself.
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Old 15th February 2006, 12:47   #13
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Quote:
Originally Posted by Mpower
Jat, you are right about the compressor and that it should always operate to the right of the surge line, but the point I am trying to make is that there is no cause for surge when the foot is lifted off the throttle. The excess air simply flows through the engine. The amount of air dosent matter in a diesel because its the amount of fuel that determines the torque produced.

The bottom line is that diesels dont have a BOV, surge or no-surge. I suggest you get hold of a service manual and see for yourself.
Oops, messed it up again. Sorry for that.

You are right, BOV is not found in dieselcar or for that matter in normal petrol car (only the rating is high then you will find BOV along with other factors, just think about a 1.5 L diesel producing about 120 PS) because the turbos performance is kept much below than maximum possible as engine opertion is not going to be montiored by trained personnel.

What I was trying to explain was about the fundtion of BOV and EGR.

And you are right about amount of air doesn't matter whether it is diesel or petrol when fuel is cut off. But when you apply brakes suddenly without disengaging clutch, then what happens. Surge does not occur all the time, but only for a short time (from a fraction of a second to few seconds) when the speed change is there. After that it is back to normal. It is difficult to go over the entire air dynamics to explain the surge but to realise what I am talking about, try to visualise what happens when you reduce the engine rpm RAPIDLY or SUDDENLY STOP ENGINE FROM A FULL LOAD (where the inertia effect is maximum) at 0.01 seconds interval (FEA - right) because the whole imbalance is over in say 0.5 to 2 seconds. The rpm is reducing. But air flow is same. Turbo goes over the surge line. Air flow reveral takes place - your 0.02 seconds is over. Balance is restored. Air flow shoots up bur engine rpm is still going down. You hear the first BOOM. The cylcle starts again as engine rpm is still not stabilized. 2nd BOOM. After 1 second, rpm has stabilized. You have already heard 50 BOOMs which means a sound frequency beat with natural frequency of turbo system at 50 Hz for just 1 second.

(In bigger high performance engines, the noise or exlosion type sound can give a real shock, if you are anywhere near the engine and under certain conditions you can really feel the air pulsation if you are very close to turbocharger air inlet).

Please note that this is only explaination for surge with RAPID CHANGE IN RPM and please do not mix with diesel or petrol or turbo or surge due blockage or air passage etc.

RK
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Old 15th February 2006, 14:14   #14
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I was also surprised when I heard the boost the Scorp was running, but can assure you that I have verified the same with the manufacturers. Are you sure the CRDE runs a Warner Borg ? I was pretty sure turbo energy supplied the turbo's for the CRDE as well.

Like I said the EGR acts like a BOV. And as Jat and Mpower have rightly said no BOV in diesels.
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Old 15th February 2006, 14:31   #15
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Quote:
Originally Posted by Sideways
Are you sure the CRDE runs a Warner Borg ? I was pretty sure turbo energy supplied the turbo's for the CRDE as well.
Borg warner electric 4wd sytem does the duty for 4x4, but donno about the turbo, ... i guess he is mistaken.

kkk (3k warner systems) is the technical collaborator for turbo energy. so kkk in india is turbo energy.

Last edited by tifosikrishna : 15th February 2006 at 14:41.
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