Factory boost levels

[cookie monster]

hi all,
i have a 4M40 2.8 turbo intercooler pajero. the factory boost setting is approx 12psi. the turbo is currently only pushing 8psi.
my question is : if i use a manual boost control valve to up the boost pressure to the factory 12psi, will the fueling still be ok? my thinking is that the pump would have been setup for 12psi at the factory so should be ok?
i know it would be best to get the thing dyno'd, but was wanting to wait for the exhaust to cark it, so i can fit a 2.5in system and then get the whole lot done in one hit.
the motor currently does put out a resonable amount of black smoke when under load(is this due to overfueling?).
cookie monster

[HotFourOk]

My question is why is your boost setting so much lower than what it should be? Where have you installed your line?

The fuel 'on boost' should be controlled by the compensator on the fuel pump for any extra psi.. but as you said, it should be setup from factory to work at 12psi no dramas.

The black smoke could be unburnt fuel due to less air going into the motor.

[cookie monster]

the boost gauge is T'd off the line going from the turbo to the wastgate.
cookie monster

[tweak'e]

the boost gauge is T'd off the line going from the turbo to the wastgate.
cookie monster

thats why your seeing incorrect levels.

connect it to the inlet manifold.

[cookie monster]

the boost gauge is T'd off the line going from the turbo to the wastgate.
cookie monster

thats why your seeing incorrect levels.

connect it to the inlet manifold.

but surely the wastgate controls the ultimate amount of boost. the line to the inlet manifold comes off the wastgate actuator(from memory).
the way i see it, for the wastgate to operate the 'whole' inlet system(all lines and inlet manifold) has to be pressurised and when the wastgate reaches its limit it controls the pressure.
or am i missing something?
cookie monster

[tweak'e]

turbo's don't actually compress air much. all the compression (boost) is acheived by flinging out the air at high speed and ramming it into the motor. the boost in the inlet manifold is higher than at the turbo (assuming no loss from plumbing).

plumbing the wastegate off the inlet manifold will mean it opens a lot earlier and you wil have a lot more lag and wastegate creep. however some systems are done like that to smoothen out the touque curve (eg so you don't snap axels when you plant boot)

with boost gauges its best to connect to inlet manifold as you want to see what boost is going into the motor which is much more important than whats at the turbo.

[cookie monster]

so if i fit the boost gauge hose to a blanking plate on the top of the inlet manifold, i should get a better idea of the correct boost level?
i think there is a blanking plate were the EGR valve fits, in other countries.
i will try that and see what result i get.
cookie monster

[460cixy]

anywhere on the inlet on a diesel should be fine for a boost gauge and remember : pressure is equal and un deminished in all directions

[tweak'e]

remember : pressure is equal and un deminished in all directions

what has that got do with it. please explain

[460cixy]

means you can stick the farkin thing anywhere on the inlet side of your engine and it will read the same

[tweak'e]

no. as i've already explained that is not the case. the further away from the head you get the less it reads.

edit: just to add, fitting it on the intake runners is not normally a good idea as the pulses in the runner can make the gauge bounce up and down. fitting it where the runners join up together is usually a good place.

[460cixy]

and you also said it does not compress the air. theres a bit of shit dribbleing from your mouth i recon ya should wipe it off

[ISUZUROVER]

no. as i've already explained that is not the case. the further away from the head you get the less it reads.

edit: just to add, fitting it on the intake runners is not normally a good idea as the pulses in the runner can make the gauge bounce up and down. fitting it where the runners join up together is usually a good place.

Hold on, all of what you have said is WRONG!

Turbochargers ARE air compressors, the air will be at the highest pressure IMMEDIATELY AFTER the turbo, and due to drag effects (pressure drop) through the ducting/intercooler will reduce in pressure as it gets further from the turbo. The LOWEST pressure will be in the inlet manifold.

What you are suggesting (increase in pressure) is completely wrong and breaks a fundamental law - CONSERVATION OF ENERGY.

[tweak'e]

sorry mayby i have things backwoulds. the old theory i'm working on (20 odd years ago) was that turbos threw air out at high speed and bulk of the compression was done when it slowed going into the motor, hence boost built up from the motor end first.

even if i'm totaly wrong, completely arse about face, the point still remains the best place for the gauge is on the inlet manifold.

apologies to cookie monster for the hijack and the fingers to the insulting little **** 460cixy !

[460cixy]

well ya hardly going to put a boost gauge on the exaust manifold are ya and the fact of the matter is that boost like vacume is un deminished in all directions so the presure you get at the compressor wheel will be the same at the inlet manifold so as i said it does not make a scrap of diffrance where you mount the gauge how ever mounting it on a intake port will make the gauge flutuate as the inlet valve opens and closes or if theres an artifical restriction in the line like an intercooler thats too small then boost will be higher on the turbo side then the inlet side as for youe 20 years ago the the therory remains the same if you want to prove it otherwise best of luck mate

[-Scott-]

boost is un deminished in all directions so the presure you get at the compressor wheel will be the same at the inlet manifold so as i said it does not make a scrap of diffrance where you mount the gauge how ever mounting it on a intake port will make the gauge flutuate as the inlet valve opens and closes or if theres an artifical restriction in the line like an intercooler thats too small then boost will be higher on the turbo side then the inlet side as for youe 20 years ago the the therory remains the same if you want to prove it otherwise best of luck mate

Air is like any other fluid - where it has flow, it has pressure drop. The issue here is the size of the pressure drop.

A non-intercooled system shouldn't see much drop from compressor outlet to inlet manifold, but once you throw in an intercooler and associated piping the pressure differential becomes significant.

Either way, the 8psi which cookie monster is measuring is too low.

[KaMo]

turbo's don't actually compress air much. all the compression (boost) is acheived by flinging out the air at high speed and ramming it into the motor. the boost in the inlet manifold is higher than at the turbo (assuming no loss from plumbing).

An added bit of trivia: As you should know the air side of the turbo consists essentially of a vaned impeller with a central eye. The suction air, flowing through the inlet to the eye of the rotating impeller, is forced outward to the tip of the impeller by centrifugal force. This displacement of air creates a continual suction at the entry thus inducing more air to flow into the eye. As the air passes through the impeller, work is done on the air by increasing its momentum, and it finally leaves the impeller at high velocity and with high kinetic energy. On leaving the impeller the air enters a number of stationary divergent passages which convert the kinetic energy of the air into PRESSURE energy. This process of conversion is known as diffusion, and hence this part of the compressor is termed the diffuser. Some compression also occurs in the impeller, with the air leaving the impeller at a higher static pressure than at entry. Overall, the static pressure rise in the compressor takes place about equally in the impeller as it does in the diffuser. When the compressed air leaves the diffuser section it enters a spiral volute which acts as a collector, conveying the air at constant velocity and pressure to the discharge flange.

And I don't think it wasn't any different 20 years ago.

[tweak'e]

turbo's don't actually compress air much. all the compression (boost) is acheived by flinging out the air at high speed and ramming it into the motor. the boost in the inlet manifold is higher than at the turbo (assuming no loss from plumbing).

An added bit of trivia: As you should know the air side of the turbo consists essentially of a vaned impeller with a central eye. The suction air, flowing through the inlet to the eye of the rotating impeller, is forced outward to the tip of the impeller by centrifugal force. This displacement of air creates a continual suction at the entry thus inducing more air to flow into the eye. As the air passes through the impeller, work is done on the air by increasing its momentum, and it finally leaves the impeller at high velocity and with high kinetic energy. On leaving the impeller the air enters a number of stationary divergent passages which convert the kinetic energy of the air into PRESSURE energy. This process of conversion is known as diffusion, and hence this part of the compressor is termed the diffuser. Some compression also occurs in the impeller, with the air leaving the impeller at a higher static pressure than at entry. Overall, the static pressure rise in the compressor takes place about equally in the impeller as it does in the diffuser. When the compressed air leaves the diffuser section it enters a spiral volute which acts as a collector, conveying the air at constant velocity and pressure to the discharge flange.

And I don't think it wasn't any different 20 years ago.

cheers thaks for that

[tweak'e]

hi all,
i have a 4M40 2.8 turbo intercooler pajero. the factory boost setting is approx 12psi. the turbo is currently only pushing 8psi.
my question is : if i use a manual boost control valve to up the boost pressure to the factory 12psi, will the fueling still be ok? my thinking is that the pump would have been setup for 12psi at the factory so should be ok?
i know it would be best to get the thing dyno'd, but was wanting to wait for the exhaust to cark it, so i can fit a 2.5in system and then get the whole lot done in one hit.
the motor currently does put out a resonable amount of black smoke when under load(is this due to overfueling?).
cookie monster

seeing as noone seem to be interested in helping i'll give it a shot..

a couple of poeple on the surf site have had similar problems. some have been cam belts slipping a tooth and also pump problems. i suspect the timing isn't being adavanced ie running retarded timing which means the fuel dosn't burn well giving low power (hence the low boost) and black smoke.

also check inlet manifolds for leaks and EGR valve which could have stuck open.

[cookie monster]

thanks for all your reply's guys.
looks like the best course of action is to get the thing on the dyno and get it set up properly. then tweek the boost if needed whilst im there.
cookie monster