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Turbo boost problem - Alisport upgrade


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Hi all,

A couple of weeks ago I fitted a full width intercooler and uprated turbo (Allards phase 3 upgrade) to my 90. I have adjusted the fuel pump as per instructions and am pleased with the power gain so far.

Today I finally got round to setting the boost pressure as instructed. As anyone who has done this will know it is a fiddly job on a 300TDi, hence the reason for putting it off for a while. The maximum advised boost pressure in the documentation is 18.5 PSI so I shortened the wastegate actuator arm 3 or 4 turns from its factory setting and set out to road test it. The pressure gauge was fixed to the drilling at the rear of the inlet manifold and fed through the passenger window so that I could read it on the move. Unfortunately the maximum boost pressure I could manage even travelling up hill, flat stick was only 15PSI. No matter how I adjusted the actuator I could achieve no more boost pressure. I therefore removed the tube that connects the the wastegate actuator to the t-piece and plugged it to try to see if the actuator was faulty. No difference! There never seems to be enough boost pressure to open the actuator anyway. (by the way, the actuator also seemed fine when I connected it directly to a compressor to check its operation). I even tried a second pressure gauge in case the first was faulty

I have checked and rechecked all the hoses and cannot identify any leaks. I have also pressure tested the intercooler and hoses (by means of an ingenious contraption involving a compressor and several parts of an old inner tube). It all seems fine - inflated it to 20PSI and pressure held. All I can think is that either the new turbo is faulty (not likely I wouldn't have thought) or the wastegate valve in the exhaust manifold itself is bust.

Does anyone have any idea where I should go from here? I don't really want to replace the exhaust manifold without being pretty sure it's at fault.

Cheers,

Keith

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I found shortening the rod on my 200tdi had no effect at all, and I have been told it can actually damage the wastegate. I fitted a boost controller which is much simpler to adjust once it's fitted as I believe this to be the "proper" way of doing things

I got mine from www.armval.co.uk but it seems they are temporarily unavailable.

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I found shortening the rod on my 200tdi had no effect at all, and I have been told it can actually damage the wastegate. I fitted a boost controller which is much simpler to adjust once it's fitted as I believe this to be the "proper" way of doing things

I got mine from www.armval.co.uk but it seems they are temporarily unavailable.

If you mean by air bleeding (venting) , not according to Allards. They supplied an adjustable air bleed valve but say that they would prefer me to adjust the actuator arm to increase the pressure at which the wastegate opens.

It makes no difference to my problem really. I can't get above 15PSI without the actuator connected!

Cheers,

Keith

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No, the one I fitted isn't a bleed valve, they are available everywhere (Halfrauds) and are cra*. Mine seals off the line to the actuator until the desired pressure is reached, it is far more accurate than the bleed type as it works on the actual pressure rather than being just a "controlled leak"

Have you got enough fuel on full throttle, You need to be burning enough diesel to produce the boost in the first place. I didn't get full boost until I changed the fuel filter!

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No, the one I fitted isn't a bleed valve, they are available everywhere (Halfrauds) and are cra*. Mine seals off the line to the actuator until the desired pressure is reached, it is far more accurate than the bleed type as it works on the actual pressure rather than being just a "controlled leak"

Have you got enough fuel on full throttle, You need to be burning enough diesel to produce the boost in the first place. I didn't get full boost until I changed the fuel filter!

That's probably why Allards preferred me not to fit it (even though they supplied it). A needle valve didn't seem to me to be such a good idea anyway. I understand the intention but it seemed to me that a 'gate' rather than needle vent would be a better solution. If I understand it correctly your's works on the 'gate' principle.

On the fuel front, I don't think that this is the problem. The only adjustment I have made is to rotate the diaphragm in the fuel pump about a quarter of a turn. (Oh, and a friend adjusted the 'star wheel' underneath the diaphragm to allow the boost to kick in a bit earlier - I think?) I get a bit of black smoke on hard acceleration plus a damn great puff on changedown at high revs. Ultimately that was the prompt for me to set the boost pressure. I thought I might be 'overfuelling' on occasions. Smoke free in normal driving though.

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Seems strange that if it was a whole replacement turbo, it wasn't set to the required boost by Allards?

Don't know if you know Edgar Morrison, but he did something to a 200Tdi turbo on one of his old 90s once, and accidentally increased the boost quite considerably. I went in it as a passenger once and without knowing anything had been done to it the difference was very noticeable!

What does the Phase 3 turbo offer if it only has the same boost pressure as a standard one? My normal 300Tdi turbo pushes out 15psi (I have a gauge too)

I'd also bear in mind that standard 300Tdi manifold gaskets don't last that long before they start leaking so winding the boost up too much might be counter productive :)

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Mmmm - I also thought that. That's why I've only been carrying out the adjustments suggested by Allards at this point. I have deliberately not gone for any of the more 'exotic' suggestions made by Marty at this stage in case it introduces further complications.

I agree the boost pressure is low. Marty's standard 110 put out 16PSI with the same test rig last night.

The problem is, where do I go from here? (By the way, I fitted a new manifold gasket when I swapped the turbo)

Cheers,

Keith

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Mmmm - I also thought that. That's why I've only been carrying out the adjustments suggested by Allards at this point. I have deliberately not gone for any of the more 'exotic' suggestions made by Marty at this stage in case it introduces further complications.

I agree the boost pressure is low. Marty's standard 110 put out 16PSI with the same test rig last night.

The problem is, where do I go from here? (By the way, I fitted a new manifold gasket when I swapped the turbo)

Cheers,

Keith

To get more boost you'd either need a new uprated actuator, or a boost control device... not a bleed valve. My last one came from a local pneumatics place and is spot on (can supply one if needed)

Above 17psi (ish) the turbo on a 300Tdi will start to become inefficient under proglonged full boost applications - this is because it will start to heat the air. To get around this you'd need a bigger hybrid turbo. But for short bursts it's not going to make that much difference.

Some people also blank off the actuator, and run it disconnected... you will get more boost, but not the ideal method.

Ian

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To get more boost you'd either need a new uprated actuator, or a boost control device... not a bleed valve. My last one came from a local pneumatics place and is spot on (can supply one if needed)

Above 17psi (ish) the turbo on a 300Tdi will start to become inefficient under proglonged full boost applications - this is because it will start to heat the air, so it's even hotter before it goes into the intercooler. To get around this you'd need a bigger hybrid turbo. But for short bursts it's not going to make that much difference.

Some people also blank off the actuator, and run it disconnected... you will get more boost, but not the ideal method.

Ian

The phase 3 kit included an uprated turbo (and, I assume, actuator). As a test, I did run it with the actuator disconnected with the pipe blanked off but could get no more than 15PSI anyway.

Cheers,

Keith

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if i read the original post correctly your measuring the boost off the inlet manifold?

this will give a lower reading than off the actuator pipe due to the intercooler etc & could well be why you cant get over 15psi on the gauge.

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if i read the original post correctly your measuring the boost off the inlet manifold?

this will give a lower reading than off the actuator pipe due to the intercooler etc & could well be why you cant get over 15psi on the gauge.

I know it will be a bit lower (1-2PSI) measured from the inlet manifold but this is where a fitted boost gauge should connect (to measure the boost being received by the engine). However, if the actuator input feed pipe is disconnected (and the ends blocked), this should cause the gauge to go off the scale because there would be no wastegate bypass at all. In my case, when I tried this, I still couldn't get more than 15PSI.

Cheers,

Keith

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Keith,

The fact that you have only gotten 15 psi, with the actuator disconnected, means that the problem is not the actuator. No boost controller (bleed type or otherwise) will have any affect. I have exceeded 18 psi (for a short time) with the boost line disconnected.

IMHO, considering what you have done/found, there are 5 possibilities left:

1. the replacement turbo is not a suitable match for your engine

2. the waste gate is faulty and not shutting off properly - I am referring to the valve which opens to allow exhaust gasses to bypass the turbine, not the actuator, which controlls the position of the wastegate valve.

3. the actuator may not be allowing the wastegate to close properly - possible if the actuator was not assembeled correctly. The actuator has a spring which pulls the wastegate closed. Air pressure from the compressor acts on a diaphram to appose the spring and open the wastegate. When you adjusted the actuator, you should have noticed that it was necessary to pull the rod against the spring to get the rod end over the pin on the lever/arm for the wastegate valve - so the spring should provide some preload on the lever/arm.

4. air is leaking from somewhere between the compressor and the cylinder head

5. there is too much pressure drop (restriction) between the compressor and the inlet manifold.

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To get more boost you'd either need a new uprated actuator, or a boost control device... not a bleed valve. My last one came from a local pneumatics place and is spot on (can supply one if needed)...

Those are 2 ways, but not the only ways - so your statement is missleading.

...

Above 17psi (ish) the turbo on a 300Tdi will start to become inefficient under proglonged full boost applications - this is because it will start to heat the air, so it's even hotter before it goes into the intercooler. To get around this you'd need a bigger hybrid turbo. But for short bursts it's not going to make that much difference...

The air will start to be heated at a much lower pressure than 17 psi. :rolleyes: This is why a 300Tdi has an intercooler.

Keith has fitted a larger intercooler, to remove more heat from the air. It is reasonable in that case, to increase the boost pressure.

Please explain how fitting a bigger hybrid turbo will get around the air getting hotter as the boost presure increases. :rolleyes:

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Another possibility is that when the cambelt was last changed, the injector timing is not quite right?

Also I could not increase the boost very much with my snorkel connected, so I cut a hole and fitted a large gate valve to the air filter housing to increase air flow for road use. It made a hell of a difference. The valve came from a local fishpond supplier.

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Those are 2 ways, but not the only ways - so your statement is missleading.

Sorry, my mistake.

The air will start to be heated at a much lower pressure than 17 psi. :rolleyes: This is why a 300Tdi has an intercooler.

Keith has fitted a larger intercooler, to remove more heat from the air. It is reasonable in that case, to increase the boost pressure.

Please explain how fitting a bigger hybrid turbo will get around the air getting hotter as the boost presure increases. :rolleyes:

This is my understanding and I'm prepared to be shot down in flames.

(ref: various sources)

A turbo has the ability to flow certain amounts of air at specific pressures, and will have a window where it will do so with the most efficiency.

Go outside of this, i.e. running more boost, and a turbo will start to generate more heat. A less efficient turbo will generate more heat when producing the same amount of boost as an efficient one.

Running over 15 psi of boost with any standard Land Rover spec turbo will lead you into a point of diminishing returns. Even though the turbo can reach higher boost pressures, there will not be a linear correlation between boost and gain in power.

Above standard boost levels, the exhaust side of the turbo isn't big enough to flow the required amount of exhaust gas, which leads to increased back pressure behind the turbine. There is also the risk of over-speeding the turbo.

When the boost is increased over standard, and especially over 17psi, the pressure in the exhaust manifold starts to increase rapidly.

If the back pressure becomes higher than the pressure in the inlet manifold it is possible to get a backflow of hot exhaust gas in to the engine.

Normally during the valve overlap period, an engine relies on the rush of cool air to cool to cool the valves, piston crowns etc etc. But if the air is heated (due to increased back pressure) the internals of the engine start to get heat saturated.

This increased heat will lead to power loss.

You can offset this effect by running a bigger intercooler, and a better exhaust. But all this does is change the point where the problem occurs, it doesn't take it away.

Running a correctly spec'd Hybrid turbo will mean you will be able to flow more exhaust gas, without the problems mentioned above.

Ian

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Another possibility is that when the cambelt was last changed, the injector timing is not quite right?

Also I could not increase the boost very much with my snorkel connected, so I cut a hole and fitted a large gate valve to the air filter housing to increase air flow for road use. It made a hell of a difference. The valve came from a local fishpond supplier.

It's never had the cambelt changed. It is only just over 3 years old and I've had the vehicle from new.

However - I do have a snorkel fitted!! Mmmmm - I'll test it by disconnecting

Cheers,

Keith

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Keith,

The fact that you have only gotten 15 psi, with the actuator disconnected, means that the problem is not the actuator. No boost controller (bleed type or otherwise) will have any affect. I have exceeded 18 psi (for a short time) with the boost line disconnected.

IMHO, considering what you have done/found, there are 5 possibilities left:

1. the replacement turbo is not a suitable match for your engine

2. the waste gate is faulty and not shutting off properly - I am referring to the valve which opens to allow exhaust gasses to bypass the turbine, not the actuator, which controlls the position of the wastegate valve.

3. the actuator may not be allowing the wastegate to close properly - possible if the actuator was not assembeled correctly. The actuator has a spring which pulls the wastegate closed. Air pressure from the compressor acts on a diaphram to appose the spring and open the wastegate. When you adjusted the actuator, you should have noticed that it was necessary to pull the rod against the spring to get the rod end over the pin on the lever/arm for the wastegate valve - so the spring should provide some preload on the lever/arm.

4. air is leaking from somewhere between the compressor and the cylinder head

5. there is too much pressure drop (restriction) between the compressor and the inlet manifold.

I think that about sums it up. I don't think 1 or 3 can be the case though. Allards have sold thousands of these intercooler/uprated turbo combinations so it can't be an unsuitable turbo. Also, when I adjusted the actuator arm I did have the pull the rod to get the end back onto the pin on the wastegate lever (which was pretty difficult actually, given its location!). I have also tried a second actuator (just in case)

It could also be an air inflow restriction by the snorkel (as suggested by Simon) or a fuelling problem (or even I suppose an injector pump problem). I'm just not sure where to go from here

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It's never had the cambelt changed. It is only just over 3 years old and I've had the vehicle from new.

However - I do have a snorkel fitted!! Mmmmm - I'll test it by disconnecting

Cheers,

Keith

Keith,

Quick way to check is to take the front off the air filter can - it'll still be breathing through the filter but won't be coming through all the snorkel piping.

Restrictiveness was one reason I changed to a Safari, but the main reason was waterproofing - the Safari is easy to waterproof 100%, the Mantec type one is not. There's a thread in the LR4x4 tech archive that I put some photos in when I fitted it, if you are interested. The in-wing plumbing on the standard breather is a massive bodge up!

Tech Archive Thread

Edited by BogMonster
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Sorry, my mistake.

This is my understanding and I'm prepared to be shot down in flames.

(ref: various sources)

A turbo has the ability to flow certain amounts of air at specific pressures, and will have a window where it will do so with the most efficiency.

Go outside of this, i.e. running more boost, and a turbo will start to generate more heat. A less efficient turbo will generate more heat when producing the same amount of boost as an efficient one.

Running over 15 psi of boost with any standard Land Rover spec turbo will lead you into a point of diminishing returns. Even though the turbo can reach higher boost pressures, there will not be a linear correlation between boost and gain in power.

Above standard boost levels, the exhaust side of the turbo isn't big enough to flow the required amount of exhaust gas, which leads to increased back pressure behind the turbine. There is also the risk of over-speeding the turbo.

When the boost is increased over standard, and especially over 17psi, the pressure in the exhaust manifold starts to increase rapidly.

If the back pressure becomes higher than the pressure in the inlet manifold it is possible to get a backflow of hot exhaust gas in to the engine.

Normally during the valve overlap period, an engine relies on the rush of cool air to cool to cool the valves, piston crowns etc etc. But if the air is heated (due to increased back pressure) the internals of the engine start to get heat saturated.

This increased heat will lead to power loss.

You can offset this effect by running a bigger intercooler, and a better exhaust. But all this does is change the point where the problem occurs, it doesn't take it away.

Running a correctly spec'd Hybrid turbo will mean you will be able to flow more exhaust gas, without the problems mentioned above.

Ian

Valid points.

My problem with your earlier post is, that some people would believe, that the temp of the air would not increase at all if a hybrid turbo was used. No matter what was used to compress the air, the thermodynamic laws for adiabatic and isothermal expansion of gasses will still apply.

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i cant see a proper snorkel restricting the airflow that much to limit the boost. ive got a safari snorkel on my 200tdi & ive seen 21psi of boost when i was setting my actuator up.

as for the 'turbos heat air' thing, i think the missing word was 'excessivley'. all turbos heat the air, but heat it too much & it expands so far you loose the advantage of the higher boost.

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