Outer Limits 4x4 Board

Hi all - just wondering if any knows how much boost a NL 2.8 turbo diesel makes and what would the highest boost it could handle - Mine at the moment is running 9psi. Thanks

My NJ was running 9psi also but I think they should be around 12-14psi. I put in a bleed valve and now run 12psi, I think it spools up quicker now.
Regrds Glenn

hay glen,
how did you go about installing the bleed valve and boost gauge, have got it on my list of things to play with. any info would be great.
according to the owners manual the factory boost setting is 80kpa, which i think does work out to about 14psi.
cookie monster

I fitted the boost gauge in place of the voltmeter, looks pretty good and the bleed valve goes between turbo and waste gate. I will send you some photos when I get a chance.
Regrds Glenn

Hi - just fitted manual boost control and set to 12psi - spools up faster and makes a nice performance gain esp on hwy going uphills. Im just about to fit boost gauge permantly inside vehicle - would be good to see some pics if possible if you have any glenn. Thanks

In the notes I have it lists :-
4D56 (2.5TDI) = 12psi
4M40 (2.8TDI) = 13psi
4M41 (3.2DiD) = 23psi (which I find very hard to believe)

just been messing around with conversion tables at work , so thought id double check what the owners manual says for factory boost setting on the NL 2.8tdi.
factory setting is 80kpa(so x by 0.145) = 11.6psi
now i used to have a nj 2.8tdi and im sure that owners manual stated 0.9 bar boost pressure ?
that works out to (0.9bar = 90kpa x .145) = 13psi, which tie's in with bitsamissin's post.
has anyone out there with an nj 2.8tdi got the factory owners manual to check the figure ?
also the Haynes manual states that the max boost is
2.5tdi = 85kpa or 12.3 psi
2.8tdi = 95kpa or 13.77 psi
wastgate opens at
2.5tdi = 82kpa or 11.89psi
2.8tdi = 89kpa or 12.9psi

also the 4m40 pdf file states that the actuator(wastgate) operates at
91kpa or 13.2psi for up to 2001 model
&
96kpa or 13.92 for 2001 on models

so it seams that nobody can put a specific figure on max boost pressure for the 4m40 motor. i think when i get round to putting in a boost control valve / boost gauge and having my motor dyno'd, i will set the boost to 14psi. then the insurance cant say ive increased boost as it depends on what you read, im just setting it to factory !
cookie monster

Look at doing the same thing. I know where and how to fit the manual boost adjuster, not sure where to fit the boost guage. There are 2 lines coming from the turbo, one going to the waste gate and the other to the fuel pump, is one of these lines where I would fit to measure the boost? I have been told that the boost should be measured in the inlet manifold there are no lines going into the inlet manifold. There is an alloy plate held in by 2 bolts on the inlet mainfold is this removed and another plate fitted, so when the vehicle is dyno tuned and the boost measured there? Is it advisable to drill and tap that plate and fit the boost guage hose to it?
Any suggestions would be appriciated

The line from the turbo to the actuator is where you install a bleed valve.

The line from the turbo to the fuel pump is for the boost compensator inside the pump. As it hits boost, the higher pressure sends more fuel into the motor.
These two places will provide a boost reading, although not the most accurate one regarding boost entering the engine.

You should install a boost gauge as close to the inlet manifold as possible. My Rocky has line for the actuator from the inlet manifold, and I teed off this for my boost gauge line.

By putting it in the inlet manifold, you are getting the amount of boost that the engine is actually recieving.

If you install the boost gauge or actuator from the outlet of the turbo, you will see the boost the turbo is producing, but the motor will actually be recieving less boost than this. Especially if an intercooler is fitted, as this increases the drop in boost through the intake.

For an accurate boost reading, tap into your manifold perpendicular to the flow.

HotFourOk,
Thanks for the info. I have a couple of other questions, if I measure the boost at the inlet manifold at the recommended psi (13.77psi) will that mean an increase in the psi at the turbo ( I have the 2.8 ICTD - 4M40 engine). Will that cause a problem for the turbo? Will there be an increased delivery of fuel if there is a pressure difference between the turbo and inlet manifold? A general question can anyone tell me where the boost is measure from the factory, the line from the turbo to the actuator, turbo to the fuel pump or elsewhere.

personally i will be plumbing my boost guage into the line from the turbo, between it and the boost controller. after that comes the wastegate that ultimately dumps the boost pressure. that would be the factory set point.
to me you want to monitor the pressure going to the wastegate, not the pressure in the inlet manifold. if you measure the pressure in the manifold and alter the turbo to suit that, you will be putting too much strain on the turbo.
eg if there was 3psi boost drop from turbo to manifold, you would have to run the turbo at 16-17psi to get factory 13-14psi at manifold. i will stick to max factory boost at wastgate.
cookie monster

Thanks for the info, I'll get around to fitting a guage in the next couple of weeks.

Ok, I have now fitted a boost gauge in the line between the turbo and waste gate. The gauge shows a reading of 9.5-10psi, is there a way that I am able to adjust the boost without having to either adding a manual boost control or taking it to a diesel specialist. I really only want to have the boost set once to the factory setting of 13.77psi. I'm using a 2" Speco boost gauge which I fitted into the clino. Unfortunately the clino has split and lost the oil, I have repaired it a couple of times, still leaks though.

The princible been that you need to restrict the line to the waist gate. In alot of cases with a manual boost controller, if you wanted to do away with this, then a little bit of solid brass or there like inline, with an appropriate sized jet. .9 - 1.2mm is prolly a good starting point. But yeh, drill it, put it in and check your pressure.

6G74,
Thanks for the info. I've used a small piece of brass rod which I have drilled a 1mm hole, the gauge is showing 10psi boost. Can't seem to get it over 10psi. However, saying that the turbo boost up to 10 psi very quickly and holds it, also has more pulling ability i.e.; accelerating in 5th, the gauge will go up to 10psi and hold it and the vehicle accelerates quite well. I tow an off-road camper trailer weighing around 1.2tone so I want all the power I can get and if 13psi is factory setting that’s what the vehicle to be set at.

The piece of brass rod I have used is 1cm long, don't know if I used a longer piece if that would make a difference? I have tired clamping the hose with a pair of vice grips that made a difference got the boost to 15psi.

A question on the setup, the manual indicated that the vehicle should be running 0.9 bar boost pressure (approx 13psi) does this mean that I have a problem with my turbo which runs at 10psi? Is there something that can be adjusted in the actuator to give the diagram more resistance?

1cm should be enough, but for an example, put the end of a straw, blow though, and now do it to the long lengh.

You can always go down to .9 or .8. As for adjustment, you could change the spring, but i doubt this is your problem, most seem to operate simular pressure to you, id imaigne the 13psi isnt constant.

Cheers

Thanks for the input James; I think I’ll leave as it is now set. The proof will be in the towing, I’ll take the trailer out for a drag over the long weekend and see how the vehicle pulls.

Lawrie