losing boost pressure?

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stevedehtiar

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hi all, i carried out a 200tdi conversion on my 90.. :D i drove the discovery for 40miles ish before i swapped all the bits over.. the landys all finished now and drives 100% better:D:D the only problem i have is that it seems to be losing turbo boost pressure, or at least it sounds like it! ive checked all my extended intercooler hoses etc and everything seems nice and secure? but when i put my foot down a get a realy loud air escaping noise from the engine bay and not a great deal of acceleration... im thinking of getting a boost pressure meter and plumbing it into the inlet manifold (there seems to be a threaded blanking plug there??) if i do manage to fit the boost gauge what sort of pressures should i be looking for?:blabla:
cheers, steve
 
check the exhaust/inlet manifold gasket. i've had a stud come loose before (it was one right at the end) and it blew all the pressure out of there (exhaust) instead of spinning the turbine.
 
i'll check that one when i get home.. its odd- it was absolutley fine when in disco, wasnt mistreated coming out or into defender..
 
stevedehtiar said:
i'll check that one when i get home.. its odd- it was absolutley fine when in disco, wasnt mistreated coming out or into defender..
Click to expand...

You will only get the turbo to BLOW when the engine is under a bit of load from nearly 2,000 revs and up.

The pressure you should be able to get is about 1 BAR, 15 psi or so.

Sounds like a hose may have come off, or split, or similar.

15 psi leaking at such a big volume as a turbo can blow will make a serious whooshing noise.

But it should be easy to find. Start at the turbo compressor stage (the alloy end) and the outlet connection (the one on the outside of the alloy volute casing) and check every joint and all hoses.

You'll need to check the intercooler isn't split too.

CharlesY
 
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If you're seeing more than 18psi at the manifold turn it down. Absolute max for a performance tuned diesel is about 21psi but not for a Landy lump. You'll blow the head gasket and burn the valves. You cant get a quart into a pint pot.
 
Check the back of the inlet manifold, when I fitted my TDI I heard a wooshing noise, I found there was a threaded hole at the back of the manifold with nothing in it - a brake calliper bolt soon fixed it and boy you want to have seen the difference!

I really ought to get a boost guage fitted into the hole.
 
Most peeps fit the boost gauge to the small tube that operates the wastegate because its easy and its where you're told to fit it.
If you can, fit it to the inlet manifold, because this is where you get a true boost pressure reading after all of the losses through the pipework and intercooler. On my TD5 I found a small core plug on the rear of the manifold. I knocked it out, drilled and soldered a brass fitting in to it. Tapped it to take the fitting from the boost gauge pipe and Robs your mothers brother. Mine is boosting to 18psi max at the manifold which equals about 21psi at the turbo outlet. The standard Garrett turbo is easily capable of blowing at more than 30psi if you wind it up or disconnect the wastegate linkage but your hoses will bulge and the exhaust manifold will glow red before you frag your engine. All the rice rocket boy racers crank their turbos up and then fit dump valves to loose the excess pressure ???????? They think it is increasing their engine performance but all it is doing is overstressing things .
 
hey guys, cheers for the sound advise:) after a good look at things i found the bottom of the intercooler outlet hose had 'missed' the jubilee clip, i rectified this and there was a slight difference, although im still getting the wooshing noise and still feel its down on performance (compared to the disc it came out of...) im waiting for the boost gauge to arrive in the post and will have a look at plumbing it into the phlenum(?) chamber.. (inlet manifold) hopefully this will give me some kinda idea if im actualy loosing boost or just my mind...:doh:
 
I'm having probs with the turbo on my TD. Any advice on which boost guage would be best to get? - would like it to fit in the space on the dash if this is pos?

The prob is basicly its not spinning up to a decent pressure - i used to feel it kick in around 2000rpm, now all i get is nothing at all _ think the wastegate may be stuck open / come out of adjustment, and therefore it is never spinning up to pressure so want to reset it again.

James
 
Take off the inlet tubing and you should see the turbo compressor vanes spinning when you get somebody to rev the engine. Keep your fingers out or you'll loose them.
If its not spinning or not spinning very fast when the engine is revved its possible the wastegate has stuck open.
You can should be able to operate it with a pair of pliers. It takes a little effort to overcome the diaphragm. So long as you dont twist the operating rod it wont do any damage. If you cant move the rod towards the wastegate housing then it is probably stuck in the open position so try to get it to close by moving the rod towards the diaphragm unit. It may take some effort to get it to move. Once you free it up operate it back and forwards several times. You should have about a half inch of movement between extremes. You can oil the linkage but it will only burn off once the manifold and turbo casing gets hot. If the rod is covered in rust give it a clean with some wire wool especially where it enters the wastgate housing as this is where it will be getting stuck. You can try putting some copper grease on it as this will last longer than oil.

Any boost gauge that reads up to 1.5 bar will do. Most of them are meant for petrol engines and show neg pressure but a diesel does not create any vacuumn to speak of which is why you have a vacuumn pump. You can get diesel only boost gauges but they cost more and are quite rare. Save your money.
Good luck.
 
Thanks, the rod is moving, but it has about 1 1/2 of movment! has something fallen off inside? - Still waiting for battery to charge up following sidelight issue (see other thread) so have not had chance to start up power plant yet, the turbine spins free when spun by hand.

Interestingly it is a new turbo charger (about 1 year old) it never quite had as much power as it did before the new one was fitted (by a garage i do not trust that much and not diesel specalist) - but was miles away from home when oil seal went so was stuck with who ever coudl get it going again! - I have a fealing that they have not set up the waste gate properly, and the boost pressure is very low

Hopefully all will become clear later when i start it up!
 
Had the hoze off last night, was spinning round nicely at tickover - reved it up, and seemed to spin a bit more, reved it up to around 3000rpm ish (a guess) and the linkage on the wastegate did not move at all.

Surely is the likage had come away from the diaphram then it would not spring back and stay open? - The linkage returns towards to front of the car. Quite abit of force is required to move it though. Presume in this stae it would just keep going and never dump the excess pressure?

However I think the real reason i am loosing pressure is the big puff of smoke that came from the manifold / head joint - time for a new manifold gasket i think - This will be done after the head gasket gets replaced and valves get reground.

James
 
jamescronin said:
Had the hoze off last night, was spinning round nicely at tickover - reved it up, and seemed to spin a bit more, reved it up to around 3000rpm ish (a guess) and the linkage on the wastegate did not move at all.

Surely is the likage had come away from the diaphram then it would not spring back and stay open? - The linkage returns towards to front of the car. Quite abit of force is required to move it though. Presume in this stae it would just keep going and never dump the excess pressure?

However I think the real reason i am loosing pressure is the big puff of smoke that came from the manifold / head joint - time for a new manifold gasket i think - This will be done after the head gasket gets replaced and valves get reground.

James
Click to expand...

No amount of revving the engine up in NEUTRAL will make the turbo start to blow.

For that you need to be IN DRIVE, foot well down on the GO pedal, and near enough 2,000 rpm.

THEN it should be blowing hard.

Fit a gauge. It's the ONLY way to tell what is happening and if it's enough.

You can happily go up to 1.5 BAR boost on any Landy except TD5 Discos.

CharlesY
 
CharlesY said:
No amount of revving the engine up in NEUTRAL will make the turbo start to blow.

For that you need to be IN DRIVE, foot well down on the GO pedal, and near enough 2,000 rpm.

THEN it should be blowing hard.
Click to expand...
Surely 2000rpm is the same when the engine is under load or not ? The exhaust gases are still impinging on the turbo vanes until the wastegate opens and diverts them around the turbo. If the turbo outlet is open to the air the compressor will spin but the wastegate wont operate because there will be no pressure build up to operate the servo.

CharlesY said:
Fit a gauge. It's the ONLY way to tell what is happening and if it's enough.

You can happily go up to 1.5 BAR boost on any Landy except TD5 Discos.

CharlesY
Click to expand...
Are you talking about boost measured at the turbo or the inlet manifold? 1.5 Bar is 22.5 psi as near as makes no difference and its generally accepted that you lose 3 to 4 psi across the intercooler and tubing between the turbo and inlet manifold which brings us back to near 18psi boost at the inlet manifold. I've seen exhaust manifolds and turbo casings glowing red hot at little more than 18psi boost which is not a good idea in my book. I dont know about the Tdi engines but my TD5 Defender does not produce any noticable gains over 18psi boost at the manifold no matter how much fuel you force into it. Dont forget that the TD5 ECU logs an overboost error which is factory set at apprx 1 Bar. My TD5Alive remap took care of this and my ECU will now accept up to 2 bar before it logs an overboost error and goes into limp mode.

CharlesY how things in your neck of the woods?
 
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Shifty1962 said:
Surely 2000rpm is the same when the engine is under load or not ?

ABSOLUTELY NOT!

Think of it like a jet engine in an aeroplane, because that is what a turbo is like.

A jet engine can run at tickover, cruise, and go full blast for take-off. So can your turbo.

The turbine (the wee bladey thing the exhaust impinges on) is driven by the flow of hot gas from the cylinders.

The flow of gas to 2000 rpm in neutral using hardly any throttle will be hatrdly any gas at all, perhaps about 10 bhp worth at the very most. Bugger-all. But in drive/3rd gear with the foot to the floor at 2,000 rpm the engine will be making nearly 100 bhp worth of power because it is using MASSES MORE FUEL which makes MASSES MORE EXHAUST GAS that is FASTER and HOTTER and AT HIGHER PRESSURE. That is what drives the turbine which drives the compressor impeller.

When passing through the turbine, the exhaust gases EXPAND as they give up energy to the turbine (about 10 -even 20 bhp in some cases!) , and the expanding process causes the velocity and temperature and pressure of the exhaust gases to go down.

It's a combination of Boyle's Law and Charles's Law.

CharlesY
Click to expand...
 
OK that seems a reasonable explanation, but does anybody have experience of the turbo making a high pitched wine when running, as it used to do this, and does not do it anymore! Is this good or bad?

Think i'm just going to dismantle the whole engine, and get its power back as lost one cylinder this afternoon after one of the injectors blocked - a bit of high pressure flow (foot to floor) soon cleared it but i think rebuild is just around the corner
 
jamescronin said:
OK that seems a reasonable explanation, but does anybody have experience of the turbo making a high pitched wine when running, as it used to do this, and does not do it anymore! Is this good or bad?

Think i'm just going to dismantle the whole engine, and get its power back as lost one cylinder this afternoon after one of the injectors blocked - a bit of high pressure flow (foot to floor) soon cleared it but i think rebuild is just around the corner
Click to expand...

Whip out the injectors (assuming it isn't a TD5!) and get someone like me to POP test them, and maybe strip and clean them. It takes about half an hour each one, and the guy who does it MUST have an injector pressure setter such as my Hartridge Pop Tester.

It may be too soon to tear the whole engine apart unless you are needingh something to do because the TV is so dire these days.

CharlesY
 
hey all, just fitted my boost gauge:) plugged it into the threaded hole in the back of the inlet manifold, foot down to the floor in 5th gear im reading 0.8 bar(11.5psi)?? (im still getting a whooshing noise, but from nowhere obvious) im gonna try adjusting the waste gate actuating rod to get a bit more boost and see what happens..
 
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