Boost Pressure

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
Fox

Fox

New Member
Posts
133
Hi All,
Can anyone tell me how to adjust the boost pressure on my 1998 Tdi is it a job I can do myself or is it best left to the professionals if the latter can anyone recommend a garage near Sutton coldfield.

Thanks

Trevor.
 
mr alford seems to know his thing about turbo's, yes its somthing that yer can do yerself but fit a boost gauge so yer know just how much yer running and never be tempted to go too far with it.
 
Fox said:
Hi All,
Can anyone tell me how to adjust the boost pressure on my 1998 Tdi is it a job I can do myself or is it best left to the professionals if the latter can anyone recommend a garage near Sutton coldfield.

Thanks

Trevor.
Click to expand...

Hi Trevor,

First, the word "adjust" is a bad word. The word you should have used was "INCREASE".

Find the little bottle-screw rod on the turbo between the circular capsule and the hot end of the turbo and work out or find out how to shorten it.

You really don't want to do this till you have fitted a boost gauge, 'cos if you hoick it up too far you may end up doing in your engine eventually.

You want about 1.2 BAR boost at about 2,000 rpm with your foot to the deck.

CharlesY
 
RAZ8550TDI said:
whats it standard charles?
Click to expand...

It varies a little between the models, but many or most are set to a maximum pressure between 0.7 and 0.8 BAR. Once it reaches that pressure the waste-gate valve allows some exhaust to by-pass the turbine, and then it holds that pressure even as the revs increase and the engine breathes more air. The engine must be working reasonably hard to make enough exhaust to drive the turbine fast enough to attain full pressure from the impeller.

Keep in mind that if you keep your foot to the deck, the engine will consume twice as much air at 4,000 rpm as it will at 2,000 rpm, so the turbo has a lot of work to do at high revs and loadsa throttle.

Upping the maximum pressure to about 1.2 BAR is quite an increase, and you should notice perkier performance across the rev range.

CharlesY
 
Hi, just ajusted my 300tdi as per my topic I posted Tuning 300tdi, and can tell you the results are worth 30 minutes of adjustments etc - basically 12 psi is the standard setting for the turbo boost, max allowable boost recommended by Landrover is 21 psi. Adusting the length on the turbo by 5mm gives approx 16 psi boost. There's some simple adjustments to the pump that requires no special tools also, fuel cons goes up but of coarse it does if you want more power!! Have a look at the reply to my posted topic on this...:D
 
Hi all would these adjustments also apply to an L series freelander?
And is it right that i can remove the vacum hose off the EGR valve on the same? If so which one is it, sorry to but in on another thread but its a goodun and really informative....
Cheers
 
can anyone give a better explanation as to what he it doing with the fuel pump? am no a diesle mechanic as petrols are my thing but i do know the basics. i can cant get the grasp of what he is doing with the pump? andy one give me a better explanation???:confused:
 
RAZ8550TDI said:
can anyone give a better explanation as to what he it doing with the fuel pump? am no a diesle mechanic as petrols are my thing but i do know the basics. i can cant get the grasp of what he is doing with the pump? andy one give me a better explanation???:confused:
Click to expand...

The fuel pump has a "maximum delivery" valve which limits the amount of fuel that can be injected to JUST BELOW the point of making a lot of black smoke out the exhaust due to too much fuel for the amount of AIR the engine can suck in at atmospheric pressure.

Now, if we add an AIR COMPRESSOR PUMP, which is what the turbo is, we can create BOOST PRESSURE and stuff in about TWICE the amount of air that the engine could suck by itself, and so, as there is heaps more air, we can inject extra fuel, and make more POWER.

The snag is we must arrange the thing so that the extra fuel can only come when the BOOST PRESSURE is present, and it would be good to fix it so the extra fuel matched the BOOST which can vary a lot depending on how you are driving. Fit a boost gauge - it is fun to watch what's going on.

So on the injection pump (usually on top) is a 'plain to see' diaphragm assembly which is connected by a little plastic pipe to the inlet manifold (or turbo casing) where the BOOST pressure is, and as the BOOST pressure goes UP the pressure in the little pipe shoves the diaphragm DOWN, and that open up the maximum fuel delivery valve to suit the extra boost air.

If you increase your BOOST, you may need to increase the setting of that diaphragm to suit, that is, as extra air is available, so to will be extra fuel let through to match it.

Does that help?

CharlesY
 
it does charles yer, but............... isnt the fuel pump on the other side of the engine bay? therefore i cant think of any plastic pipe that runs from the turbo to the pump off the top of my head?
 
its ok, i broke it all down and imagined doing it in my head so i think i have picked up on it now, while on the subject no one mentions a dump valve on it, in theory if yer running more pressure through the tubby dont yer wanna relase it a tad quicker?? so its not under constant pressure when yer dont really want it?
 
We are referring to the INJECTION PUMP here, not the LIFT pump.

I hope you are too.

If it's a diesel and has a turbo and an injection pump, you can be sure enough there's a pipe about the size of screen washer tube between the injection pump boost diaphragm and the turbo or inlet manifold. Gotta be there!

Now the next snag with a turbo is keeping the brute under control, stopping it from over-speeding and / or over pressuring.

This is achieved by the WASTE GATE VALVE, which is actuated by a round diaphragm capsule near the cold inlet end of the turbo which pushes a rod (sometimes it pulls it) attached to a valve in the hot exhaust side. That valve allows a heap of exhaust to bypass the turbine, which reduces the power developed by the turbine. As soon as the BOOST is up to pressure, the diaphragm opens the valve, and then there's no higher boost pressure.

If you SHORTEN the rod you INCREASE spring pressure in the system, and so there has to be HIGHER BOOST before the pressure in the capsule is enough to open the waste gate valve.

So there are TWO diaphragms involved in controlling turbo boost.


CharlesY
 
RAZ8550TDI said:
was working on it today and found the hose in question, turn the turbo up and half way through the smoke screw, cheers.
Click to expand...

Let us know what happens.

When you test it, be sure to have a video camera running so that if you blow the head off the top of the block we can all see it happen.

You were told .... FIT A TURBO GAUGE!

But it sounds like you're well on with the job.

CharlesY
 
iannotts said:
Turbo Gauge

Some thing like this?
Click to expand...


Just the job!

Like mine and most (but not all) diesels, it should NEVER go into the vacuum section of the guage.

The only diesels that should do that are the ones with throttle valves across the air inlets to make vacuum for servo brakes, or for some crazy anti-pollution reasons.

Any Boost at all is good, and more is better, but you do want to limit the maximum boost to some sensible pressure so you don't cook your engine.

You'll be interested seeing the boost pressure and what makes it rise.

High boost, high gears and light throttle (a delicate balance to achieve!) makes for best fuel consumption usually. But you will need enough revs so that the turbo gets enough exhaust to begin working, which means some speed between 50 and 55 in 5th gear in most Discos. Any more and the airdrag rises too much and uses up power, and any less means the motor isn't making enough exhaust to do the business.

My TD5 Disco on cruise control at about 55/56 mph can easily top 42 miles per gallon on a motorway run. Not bad for a sleek streamlined lightweight.
Fantastic for a two and a half ton 4x4 shaped like a brick!
CharlesY

CharlesY
 
You must log in or register to reply here.

Similar threads

L
2002 Freelander 1 TD4 Boost Presure Sensor (MAP)
Replies
10
Views
574
landfr
L
N
Loss of Power
Replies
0
Views
237
Nasos
N
A
10P won't rev past 3K
Replies
7
Views
528
sierrafery
sierrafery
J
Discovery 1 1992 refurbishment
Replies
4
Views
330
Anaconda
A
Dan333
Skew gear timing
Replies
8
Views
509
Dan333
Dan333
Back
Top