Turbo glowing red when it shouldn't

I noticed the other night that after a 30 minute drive, the turbo exhaust housing was glowing red! I would expect that after a hard run with prolonged boosting, but not after 30 mins of part throttle and the occasional boost (no more than 180kpa).

My first thoughts were cam timing. Could have slipped a couple of teeth and is too retarded, but I checked that and it's fine.

Next thought was a blocked exhaust / collapsed silencer internals. Can't really check that without taking the whole lot off.

Third thought is inadequate water flow through the turbo, but glowing red hot after 30 mins highlights something more severe? I've had trouble with the water hoses splitting, mainly the original VW throttle body coolant outlet, which T's off the head to matrix hose. I replaced that with a metal T and -6 AN fittings etc.

I cut the VW hose up and examined the T off and noticed it's actually blanked off with a small hole drilled in it at the matrix end, which must create a pressure build up to force water through the throttle body (or turbo in this case)? Since my metal T is bigger bore and not blocked off like that, I'm wondering if the water is just ignoring the T off and just going straight through the matrix? I can hear air gurgling in the system (mainly in the matrix) when I shut the engine down.

The turbo spins down as normal when switched off, so isn't siezed.

Supposed to be going to stealth on Friday (for exhaust work oddly enough!) but I don't want to drive 140 miles and potentially fry the turbo to death.

Any thoughts?

Oil flow is good, checked that.

Oh and the car feels reluctant to rev and course off boost.

Bloody thing. It's really trying my patience at the moment!

What's the AFR's? Sounds like you are running lean under part throttle cruising, also are you consuming any water? Likewise what are the water temps like?

What are your EGTs like? Is it just the turbo housing that is glowing red or does the manifold and downpipe look suspiciously hot too? Could there be a blockage in the water line to and from the turbo? Where does the water go after it's been through the turbo?

The AFRs target is set to 14.7 on cruise and the lambda display seems to read that, but I need to get the lambda checked / calibrated.

Nothing's really changed map wise, so I don't understand why it's suddenly doing this.

Water temp is 85 deg on a cruise and I've set the DTA to switch the fans on at 95 deg C. You have to on a VR6 really! I recently replaced the theromstat, main water pump, radiator and fans as I was having over heating problems. It used to cruise at 95 deg, so it worked.

I don't appear to be using any water, it's hard to say because the level rises up and down when you turn it off, but it's certainly not using any in a major way. I do smell coolant in the car occasionally (no visible leaks in the engine bay), so I'm wondering if the matrix needs doing - again

EGTs - 70mph cruise - 680ish Deg C, 80mph - 750ish, 90mph - 780ish. On boost, 850-880 max. They've been like that for 2 years and never really caused an issue before and seem to be average from what I've gathered from other VRT users.

The water exits the turbo and joins the expansion tank inlet with the radiator top hose.

I'm seriously considering either going big capacity normally aspirated, or getting shot of the Corrado. It's constantly causing me grief

Probably already checked but, can you see the water exiting into the expansion tank when running?


P.S. Don't sell it

That's the thing Stu, there's not a constant flow back into the tank like there should be, just dribs and drabs occasionally.

I've ordered a new head to matrix hose from VW and see if it helps.

Just had an interesting conversation with Jon at Stealth. He's been running his 3.3 24V with Borg Warner GT42 for a few weeks now and he says his turbo glows red like mine too! Our EGTs seem to be the same too.
He's got a 4.25" outlet into full 3" exhaust and running the stock 24V ME7 ECU. He's not convinced it's a water problem as his is an oil only turbo and does the same thing.

I'm starting to think VR/24V Ts just don't like running at 14.7 AFR. I think I'll turn closed loop off in the meantime and richen the map up and see if it helps!

Might it be worth having an additional electric water pump to provide steady flow to the turbo?

It could be that your lambda has drifted somewhat, I've heard that widebands do tend to do that. How close the turbo is the sensor itself? Could your high exhaust temps cause it to drift?

(I bet that 3.3T is a bit of an animal)

Be sad to see it sold as its always been comforting to know that such a tuned car can be used often with a level of reliability albeit with the occasional bit of maintenance.
So no recent changes at all?
Must be something local to the turbo then?!????

kevhaywire wrote:

I'm starting to think VR/24V Ts just don't like running at 14.7 AFR. I think I'll turn closed loop off in the meantime and richen the map up and see if it helps!

Goes back to my original statement regarding the AFR being an average of two uneventies on the VR's the rear three cylinders running lean compared to the front 3 running rich. The fact it has just started happening though seams to indicate you got an airpocket somewhere.

Thanks guys

Yeah DirtyT, it's done 30K miles with very little trouble, so I did jump the gun with my with my giving me grief comment. No recent changes. I did have some cooling issues a couple of weeks back and I noticed the MOT tester got the water temp up to 120 degs according to the logs
I guess the fans didn't kick in, hence why replacing the entire cooling system practically.

Stu, the lambda is in the downpipe in the stock position, about 2 feet from the turbo, so if anything, it's probably running too cold!

You're right JNLRacing. I was previously tuning against plug colour, but I think from now I will run the rear bank richer.
The 24V shouldn't need that as it has combustion chambers in the head and far better balanced ports. Every 24V head I've seen lifted shows perfect and uniform burn across all 12 exhaust valves. Same can't be said of the 12V.

I'm going to take the turbo and manifold off this weekend and inspect the turbine wheel and look for any restrictions / damage. I'm pretty sure if coolant was an issue, the centre housing would show signs of overheating, rather than the whole back housing glowing red!
Good time to get the ATP manifold etc on I suppose....

kevhaywire wrote:<SNIP>Stu, the lambda is in the downpipe in the stock position, about 2 feet from the turbo, so if anything, it's probably running too cold!

Lambda needs around 400 degrees to operate successfully, but even a normal lambda in the stock position would be fine once the engine has been running for a little while, can't see it being too cold, to be fair.

kevhaywire wrote:<SNIP>I'm going to take the turbo and manifold off this weekend and inspect the turbine wheel and look for any restrictions / damage. I'm pretty sure if coolant was an issue, the centre housing would show signs of overheating, rather than the whole back housing glowing red!
Good time to get the ATP manifold etc on I suppose....

Well, you've got the manifold there, so defo a good opportunity. Do you think that getting the water temps up to 120 deg at that point may have been enough to cause the oil in the turbine housing to go all gunky and hence restrict the free movement somewhat? 120 deg water wont cool the oil around the turbo down very much, that's for sure...

I dunno mate. I checked the turbo the other day and it steel feels the same as the day I got it, in terms of shaft play and free spinning.

120 deg is where the 3rd fans speed kicks in on standard VRs, so VW would have tested the engine at those kind of temperatures, so fingers crossed it survived the ordeal.

Hopefully I'll take the downpipe off and just discover I dropped a tea towel in there by mistake

Just had a thought where are you measuring the EGT's from as you need to take a reading approx 4" away from the back of the exhaust valve before the turbo otherwise you get a false reading due to heat dissapation through the exhaust and turbo housing.

My EGT probe is about 2" from the turbo outlet in the downpipe.

I know that's not ideal but at the time I didn't know how good or bad my EGT kit was, so didn't want the probe breaking off and wrecking the turbo!

So would the readings be lower or higher if placed before the turbo?

much much higher before the turbo can be as much as 300+ celsius depending on size of turbo and length of exhaust runners

Why have you noticed the turbo glowing red? has it not always been like that?

I would think the turbo temps would be a good 200 deg + hotter before the turbo on the manifold,being compressed gasses.

edit JNL beat me to it.

JNLRacing wrote:much much higher before the turbo can be as much as 300+ celsius depending on size of turbo and length of exhaust runners

Hmmmm. Something's not right then because if I'm seeing 750 deg C on an 85mph cruise where the probe is now, you're saying it could actually be as high as 1050 deg C? My EGT probe can't be reading right then. Cruising at 1050 deg C is ridiculously high, but then again, that could be why the turbo is glowing.

I've seen tuned RS4's hit 1060's before. Remember doesn't have to be 300, could be 100 or 200. However it seems to be a definite indication that your EGT's are way of the mark if they are reading 750 and the turbo is glowing. Be an idea to knock a little timing out in the map around part throttle cruising that will help reduce your temps a lot better than overfueling. For example the amount of extra fuel you add to change the AFR from say 12:1 to 11:1 (using latent heat maths) is only sufficient to drop your piston temperature by a few degrees relative to knocking 1 degree of timing out which is much more effective.

Thanks for the advice JNL. I was led to believe more timing reduces EGTs, but good to read it's the other way round!

OK, well I stripped the turbo this afternoon and both wheels are fully intact, but as you can see, the turbine one definitely showing signs of high EGTs I'd say. Other than that, the turbo looks and feels normal.

Definitely getting plenty of water, so that can be outruled now.

Feeling hot, hot, hot!
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Compressor looks good, not that I had reason to suspect it was damaged.

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Turbo is a ball bearing one and done ~ 30K miles. Is it normal to have a thin film of oil on the compressor back plate and the turbine sealing plate? Literally just a fine film, nothing drastic.

Oh and the huge crack right round the manifold isn't helping matters

I was aware of a small crack last time I took the heatshield off a few months ago, but it's spread big time. The picture doesn't do it justice, there are actually holes along the crack! Mr Lambda probably wasn't happy about that, or Mr turbo!

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More timing = too advanced which = dieseling/detonation = hot hot hot = cracked exhaust mani.

Turbo is showing signs of running incredibly lean and hot. Not to sound silly have you checked whether your dump valve can hold a vacuum? Also any vacuum lines that may have leaks in them drawing in false air. It's a common fault for a turbo car suddenly going lean.

Thanks again JNL. The engine's in bits now so I can check all that as I go along.

I guess it caught it in time before permanent damage occurred.