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Discussion Starter · #1 ·
Help!

Arrghh. Please bear with me.. I don't know if all of this is related however :

The 9000 was running great boosting to 1.2bar @3000rpm.. trailing to 0.9bar @ 5000 rpm. It's boost was stable and only a whistling noise along with the growl of the engine could be heard. When I came of the throttle the boost gauge would show -0.7bar on the over run.. and at idle a very steady -0.5bar.

As of last night.. and today.

The 9000 has started to make an intermittent higher-pitched groaning noise when boosting.. at around 0.7bar... i.e as the car boosts .. at a certain point a very audable groaning noise is heard as the car boosts through 0.7 to 0.9 bar.. then it goes away again.. it does it on every acceleration and at every speed... and I don't think it's transmission related.

The car will sometimes boost to 1.1bar at 3000rpm but as the revs increase, boost drops rapidly to 0.6-0.7bar.

On the over run I show -0.5bar now.. and at idle -0.4bar.

I've been under the car and checked all the vacuum hoses. They are in good condition and secure. All the pipes connecting the turbo are in good condition and are secure. The wastegate actuator is fairly new and is properly connected to the wastegate. The dumpvalve is also fairly new piston type from Forge and is working properly.

What could be wrong?

I've got a horrible feeling that one of my problems (i.e. the groaning noise under boost conditions) may perhaps be caused by a bearing letting go in the turbo..
 

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It could be the turbo vanes catching the housing as your symptoms are what I experienced when my 2 turbos failed in quick succession due to overboosting. Quick check would be to take the inlet flexy off the turbo and see if the turbo vane has sideways and longitudinal movement large enough to catch the casing.
 

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Hmm... I'm afraid it does rather sound like a turbo problem. The turbos on standard models don't have the full 360 degree thrust bearing like the Mitsu TD04 on Aeros, so will not be as resistant to long term boost.

As Mark suggests, see if there's any slack on the shaft...
 

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I would say the Mitsubishi TD04 as fitted to the Aero. It might require a little bit of re-positioning of pipes, but it is a far more robust unit.

I reckon you'll lose out slightly on bottom end torque 'cos it's bigger, but get more capacity higher up the rev range. This shoud be kinder to your auto box.
 

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If you're sure that the vacuum on overrun and idle has dropped, it's definitely worth looking a bit farther for leaks. I can't see how the turbo could cause this. Have you checked the dump valve? Any other hoses apart from vacuum hoses? (I'm not too familiar with the TCS setup).

All that pressure will find any loose clips or hoses. I know - it has done on mine, on several occasions...
 

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Originally posted by BillJ:
[qb]If you're sure that the vacuum on overrun and idle has dropped, it's definitely worth looking a bit farther for leaks. I can't see how the turbo could cause this.  [/qb][/b]
Yes, sorry, I missed that bit, but I'm not sure how a leak would cause the noises Mark describes though
 

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Discussion Starter · #8 ·
I think the two are perhaps unconnected...

I've got a vacuum leak somewhere.. I'm starting to think that the solinoid on the strut turret might be defective..because when I pull the right hand hose off and put my thumb over the end of the hose, the vacuum pressure drops back to the way it should be.

The noise is starting to very much sound like an unbalanced turbo...

I see that speedparts does a T25/28 hybrid with a 360degree thrust bearing.. this sounds like a drop in replacement... what do people think about this turbo.. and it's suitability for my car.
 

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Info on the Speedparts T25/28...

It's a hybrid of the T25 and T28
. The T25 element refers to the turbine wheel, which is the same as fitted to standard models, the T28 to the compressor wheel.

The T25 section is cut back, which means that the blades have been ground down slightly in order to limit the maximum rotational speed- it doesn't need to go as fast as a regular unit to pump the same volume of air 'cos it has a bigger compressor.

It's had some CNC work to the compressor housing, although that isn't specified.

In practice, it will have a bit more lag than your standard unit, but will be able to reliably deliver higher sustained boost levels. At the top end, it will be well within it's flow map, so will be operating more efficiently.

Or in other words, less
low down. more
up top...

What your box will make of this, I'm not sure, but I would have thought that moving the major part of the delivery higher up the rev range would be kinder to it.

As it retains the standard turbine section, I would think it would be an easy drop in replacement.
 

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Discussion Starter · #10 ·
Interesting...

Going back to BillJ's point... The dumpvalve that's currently fitted, was fitted over 6 months ago by me. I've checked the physical hoses serving the valve and they are all sound, however, what would be the symptoms if the diaphragm in the valve has failed?

It would certainly cause a vacuum leak, it would also certainly cause erratic boost, and indeed a lot of boost leakage at higher RPMS... but would it also make the noise?

Anyone with any thoughts on that?
 

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Discussion Starter · #13 ·
Well I think I may have found the problem...

Going on the simplest thing first principal.

I've removed the Forge recirculating dumpvalve.. cleaned it.. and dismanteled it... guess what.. the rubber seal was perforated... I reckon that's what was causing the noise.. the lack of pressure.. and the drop in vacuum on overrun and idle...



 

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Discussion Starter · #14 ·
You know.. the more I look at this dumpvalve.. the more I'm realizing.. this isn't a Forge Piston dumpvalve!!!!.. it's just a metal valve with a diaphragm!!!!!

I'm right aren't I?

Can you confirm ?

If so Beisheuvel motorsport are in for some stick tomorrow!
 

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Discussion Starter · #17 ·
I've reassembled the valve... and refitted it upside down until tomorrow.. when I can replace it with the real thing.

I've driven the car.. and no noise right now and it's holding boost right now.. so it's for sure the dumpvalve!

Great!.. better a proper piston valve replacement than a new turbo... for now!

Thanks everyone for your wisdom!
 

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Discussion Starter · #20 ·
Well.. I went out and got my shiny new Forge *piston* recirculating valve...

The difference between the one I had and the Forge is startling. Firstly the Forge is HUGE!.. plus it has several allen-key bolts holding it together, the spring is very stiff and the whole thing looks like it could take alot more than my car could give it... just as well really since the car destroyed the old 'diaphragm' type in under 6 months.

Old and new...



The adaptation run was erm.. interesting.. at 23c ambient temperature the car boosted way past 1.5bar boost before hitting fuel cut off...

After the run everything settled down to 1.1bar boost @ 3000rpm and 0.9bar boost @ 5000rpm.

I'm thinking that baseboost is set too low.. I reckon that 1.3bar for 3000 and tapering to 1.1bar would be about right.

What do you all reckon? Oh and replacing the valve has cured all the problems mentioned above!..
 
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