TD04 turbo advice please!

[Sammyboy]

G'day everybody, I would like to seek some advice on the rebuild of my 1990 Mitsubishi Pajero TD04-9B turbocharger. I will be buying this kit from e-bay http://cgi.ebay.com.au/Turbo-Rebuild-Ki ... 45f437b02e" onclick="window.open(this.href);return false; , and I don't think that I will have too much difficulty in re-assembling it (I have already dismantled and cleaned the turbo, just waiting on rebuild kit). I will also be having the CHRA professionally balanced before fitting it to my car.

I am contemplating buying this turbo actuator http://cgi.ebay.com.au/ws/eBayISAPI.dll ... AQ:AU:1123" onclick="window.open(this.href);return false; which is set at 1 bar or 14.7psi boost. My fuel pump was professionally upgraded in 2007 to allow for more fuel/more boost, but I don't think that the boost level was set that high (boost was increased somewhere between 12 and 14psi). If I fit up this rebuilt turbo and this turbo actuator, can the boost pressure be increased or decreased to suit my set-up? Will it damage my engine or drivetrain?

I am also thinking about buying this oil feed line for my turbo http://cgi.ebay.com.au/ws/eBayISAPI.dll ... AQ:AU:1123" onclick="window.open(this.href);return false; . Having a look in the engine bay tonight, there are two hoses from the top of the compressor section (I think) of the turbo. One goes to the fuel pump and the other goes towards the intercooler. There is also what looks to be a metal pipe line going from the left side of the turbo to the cylinder head. Which one is which, and what exactly does this kit replace? Is it really necessary to get this kit or is it ok to re-use the one I have?

Just so you know, I am really keen to have a go at rebuilding this turbo. It is a spare one that I have, so if I ruin it in the process, there is still a turbo fitted to my car. The CHRA will be properly balanced before being fitted to the housing. The turbo, turbo actuator and oil feed line will be fitted by mostly by me, but with the help of my good mechanic friend (who knows much more than I do!). After this my car will be fully serviced, then have the injectors replaced and then dyno tuned. On 13/9/10, my family and I will be leaving Melbourne and heading west towards Esperance , so I want my car to be just right!

I'm really keen to get some advice on these questions, so I can make some more clear decisions. Big thanks from Sam.

[KiwiBacon]

If you reinstall the compressor wheel, nut and turbine shaft in the same orientation, then it doesn't need rebalanced.

[Bush65]

Assuming the spare turbo that you are using is the same as the one currently on your engine, why not re-use your existing waste gate actuator and oil feed line?

As Dougal indicated, if you have marked the turbine shaft, compressor wheel and nut before dismantling so they are re-assembled in the same orientation, then the assembly should not need to be re-balanced. However if they may be in a different orientation then balancing is called for.

The difference between 1 bar and 12-14 psi is not significant and will not cause engine failure.

The usual way to increase/decrease the boost pressure is to shorten/lengthen the actuator rod. I can't see any screw adjustment in the rod of the actuator in the ebay pics so you would have to be creative - possibly bending the crank in the rod to suit.

Another way to increase the boost pressure required to open the waste gate is to fit a boost controller in the pressure line between the compressor outlet (or inlet manifold) and the actuator.

Remember that boost pressure is also a result of what is happening with the exhaust gas. More load on the engine, with resulting increase of fuel from the injection system creates more heat/energy in the exhaust gasses resulting in the turbine spinning the compressor at higher rpm - boost pressure is related to the tip speed (squared) of the compressor wheel. The waste gate opens at the setting of the actuator so that some of the exhaust gas bypasses the turbine.


Note the above comments on boost are assuming the engine is not computer controlled.

Edit: don't forget oil in the turbo bearings before starting the engine.

[Sammyboy]

KiwiBacon- I was planing on having my turbo balanced right from the start. That's why I never worried about marking the positions of the turbines. My $10 turbo was in need of alot of work...

Bush65- My engine is not computer controlled so all your advice would be accurate. If my turbo boost in 2007 was set at 12psi, would that psi change or alter over time, or would it still be exactly the same as the level it was set at back then? This is the reason that I was contemplating buying a new Turbo Actuator. If this is not the case, then there is probably no need to buy one... I just want my turbo to be running at 100% before I leave for Western Australia (which is 90% long distance driving at highway speeds, 10% 4WDing over sand and rocks), and I have read about the benefits of driving with a rebuilt turbo. The turbo that I picked up from ebay is a TD04 9B, which is exactly the same as the turbo fitted to my 4WD (which is exactly why I bought it). When I have a spare moment, I will take some photos so you know exactly what I am talking about (i'm stuck at work for 15.5 hours straight as we speak). Thanks for your advice, it has helped me alot!

[KiwiBacon]

Your turbo was balanced before you started. Getting it rebalanced isn't going to make it better or more reliable, it's just going to cost more.

Your wastegate setting shouldn't have changed unless the rubber diaphragm is leaking. In that case it won't open and you'll have more boost than expected. Just remember there is a bigger potential for a rebuilt turbo to have issues than one that has been working well for a long time. Make sure you test any new work well before you embark on your trip.

[Bush65]

The waste gate actuator has a spring in the lower section which pulls on the rod to hold the waste gate closed against the pressure in the exhaust manifold. The spring needs preload (installed compression force on the spring) to prevent the gate opening at low pressure.

There is a diaphragm in the actuator above the spring and boost pressure acting on this diaphagm acts to push the rod against the spring force. When the total force due to boost pressure on the diaphragm plus exh manifold pressure on the waste gate increases to the spring preload setting the waste gate will start to open. Because of the spring rate, the boost pressure will need to increase further to fully open the waste gate.

The spring preload (and thus boost pressure required to overcome it) is determined by how much the spring is compressed to hook the actuator rod up to the lever on the waste gate. Shortening the length of the actuator rod will compress the spring further an increase the preload - moving the actuator mounting bracket further away from the waste gate lever can achieve a similar result.

Because of manufacturing and assembly differences/tolerances, I wouldn't assume that fitting a different turbo or actuator will give exactly the same spring preload - should be checked with a boost pressure gauge and adjusted as required.

The actuator and waste gate only control what pressure will open the waste gate. Boost pressure is produced by the rotational speed of the compressor wheel. The torque required to spin the compressor increases with impeller speed and has to be provided by the turbine which is converting heat energy in the exhaust gas to mechanical energy. If any of these is up to it the desired boost pressure won't be achieved.

In your case with the same turbo rebuilt you should expect to be able to obtain at least the same boost pressure before.

If the boost pressure is lower than before, the actuator may be allowing the waste gate to open earlier, so shorten the rod length or adjust the mounting bracket away from the waste gate lever.

Similarly if you want more boost pressure than before. But remember the boost pressure may be low because the turbo is not spinning fast enough. As the load on the vehicle increases due to acceleration, hills, wind resistance, or vehicle payload the engine will get more fuel and the exhaust gas gains energy to spin the turbo faster.

The turbo on a particular engine is only capable of producing a certain amount of air flow and pressure. Assuming the compressor is operating within its range of air flow and pressure, and the waste gate is held closed, adjusting the fuel injection pump will adjust the boost pressure by changing the compressor speed.

Also setting the waste gate so the compressor is operating well away from where it is efficient will increase the heat that is added to the charge air and the performance will not improve at anywhere near the same rate as boost pressure - a typical situation for small turbos.

[Sammyboy]

I cleaned up the spare turbo, but was told that the turbine shaft had worn out quite a bit, so I thought that I would remove my existing turbo and check that one out. I am in the process of undoing the compressor and exhaust turbines but cannot get the bolts to move. I used a 12mm socket on the exhaust turbine (pictured) and an 8mm socket on the compressor turbine, but cant shift them (I know hat the turbine is reverse threaded). It feels like the nut has been welded onto the shaft! Any suggestions that could work without damaging the turbine shaft?

[UGOTNUFN]

I cleaned up the spare turbo, but was told that the turbine shaft had worn out quite a bit, so I thought that I would remove my existing turbo and check that one out. I am in the process of undoing the compressor and exhaust turbines but cannot get the bolts to move. I used a 12mm socket on the exhaust turbine (pictured) and an 8mm socket on the compressor turbine, but cant shift them (I know hat the turbine is reverse threaded). It feels like the nut has been welded onto the shaft! Any suggestions that could work without damaging the turbine shaft?

Your not seriously trying to undo thst nut in the picture are you???

[Dzltec]

To be honest, I would stop where you are and let someone do it for you. If you don't know or can't figure out why it won't undo, it will only cause some troubles down the track. However i am also for anyone learning. The nut in the pic is all one, ie the shaft turbine wheel and nut are one piece. The only nut that can be undone is the compressor wheel.


Andy

[KiwiBacon]

Come on guys, give him some credit. He's obviously trying to undo the compressor nut. He mentions a 12mm socket on one end and an 8mm socket on the other.

[Sammyboy]

Your not seriously trying to undo thst nut in the picture are you???

That is right, I am serious, and i'm not trying to undo the nut on the exhaust turbine (which takes a 12mm socket), as it wont come off no matter how hard I try. KiwiBacon was right in saying that I was trying to undo the compressor nut on the other end of the shaft (which takes an 8mm socket). I didn't want to damage the shaft or anything else, so I took it to somebody who knew exactly what they were doing, who got the nut off for me. I stripped the turbo bare, took the shaft and compresor turbine to get it professionally balanced, and now it's all ready to go back in. The problem with the new nut that came with the rebuild kit is that the thread pattern is wrong, so I have to re-use the not so good nut that came off the shaft to begin with. I will put a photo up to show the way that my CHRA turned out, and hopefully by the end of the week, my car will be up and running again (I have to fit a new alternator, and re-fit my turbo).

[KiwiBacon]

You can't get the shaft and wheel balanced without the nut because they're already individually balanced.
They are assembled with the shaft part of the labrinth seal and the nut is trimmed to take out any stackup balance. This is why your original compressor nut will have a nick or two out of it.

[Sammyboy]

This is the nut that I am talking about. It is badly worn almost to the point where the spanner turns around on the nut! That's why I was concerned in the first place about undoing the compressor nut and damaging the shaft.



This is what I hope is the finished product, all assembled with a new nut. Because my old nut was worn out, I went and replaced the nut, which seems to be just fine. I'm thinking that I will take the CHRA to the person that balanced the shaft and turbines for me just to let him check it over and give me the green light to fit it back on my car. If what you say is true KiwiBacon, then I'll probably have to balance it all over again because of the new nut, but I don't really mind if it comes to that.

Last night and this morning, my shaft and compressor turbine were spinning individually and not together, and the compressor nut was either tightening of loosening depending on the direction that I spun the wheel. I took the CHRA back to the guy this morning who told me to dismantle it (again!), clean it (again!), and reassemble it. So now that it's re-assembled, I am hoping that it will be now ok to re-fit back on my empty engine!

[KiwiBacon]

What's with the 6mm or so of spare thread? I've never seen a turbo with more than a thread or two (if that) protruding.

[Sammyboy]

What's with the 6mm or so of spare thread? I've never seen a turbo with more than a thread or two (if that) protruding.

I don't know. I noticed that myself. With the second hand turbo I planned to rebuild, there wasn't as much spare thread on that one.

[Sammyboy]

My turbo is now re-fitted onto my Paj. As explained to me by may people on this and other forums, I did put all the bearings in engine oil before fitting them back into my turbo. As I expected, for the first minute or so after I had driven with this turbo for the first time, the exhaust turbine housing was smoking a bit (probably due to the oil in the bearings, CHRA and possibly the exhaust housing) but it's ok now. My car drives well, but I think some things may need to be adjusted. My car is being serviced this wednesday 25/8/10, and dyno tuned next monday 30/8/10 so I may just hold off until these days to have the turbo checked over.

When I drive my car, I can certainly hear the turbo, but cant necessarily feel it as much as I would like to. Earlier on in this entry when questioning members about the wastegate and boost pressure, Bush65 said that the spring needs pre-loading to prevent the wastegate from opening at low pressure. This is what I think may be happenning as the turbo does spool up very quickly, but the momentum of my car doesn't really increase...

This is my main concern. As mentioned, i'm getting it tuned next week by a turbo specialist. If I just take it easy driving my car without taking too much notice of the turbo pressure or wastegate, is this going to damage anything? If the problem that I mentioned is because the wastegate is letting most of the boost escape, is that cheap and easy for a specialist to fix? Could it be related to anything else?

What I actually did to my turbo was replace the bearings in the CHRA, fit new o-rings to the CHRA, fit new gasket to the manifold/turbo (I had to re-use a gasket from turbo to exhaust, as the one provided was incorrect), unbolted the wastegate without adjusting it, and then re-fitted everything.

At the same time as the turbo, I also replaced my alternator, which has been given the approval by my mechanic friend, now I just need to wait it out to get an approval from A) the person servicing my car B) the person tuning my car...

Thanks for all your help through this project guys, it really made things much clearer for me...