2 cracked exhaust elbows - MTU

[Deleted User YDKXO]

Nice bit of welding that. Welding stainless really is an artform

 

[BartW]

waw they look nice,
is there a reason why they didn't drill mounting holes in the flanges before the welding ?

 

[markc]

waw they look nice,
is there a reason why they didn't drill mounting holes in the flanges before the welding ?

They are held on by clamps, no holes needed in the flange

 

[MapisM]

Cost was £465 each plus vat, compared to £2800 each plus vat from MTU.

Well, as boaters, we are all used to be ripped off.
But in this case, the fact that MTU part costs SIX (!) times the custom one is nowhere near as surprising as the difference in quality, which is clearly the other way round, even just judging from some pics.
Kudos to your fabricator! :encouragement:

 

[[2068]]

That's looking really good.
My only thought is around single wall vs double wall in terms of the temperature of that external surface, and what, if anything, you were planning to put around it.

 

[markc]

My only thought is around single wall vs double wall in terms of the temperature of that external surface, and what, if anything, you were planning to put around it.

It should be single wall anyway for OEM spec. All the exhaust is wrapped / jacketed from turbos onwards. I'm sure theses elbows get pretty warm - I suspect around 600 c

 

[MapisM]

I'm sure theses elbows get pretty warm - I suspect around 600 c

I don't think they'll get anywhere near that, M.
The dry section in my s/steel exhausts is not comparable, because it's extremely short (see pic in post #27), so it's much cooler "by definition", so to speak.
But also in your setup, the elbow will dissipate heat on both side, i.e. the outlet, where the pipe is eventually connected with the wet section, but also the flange, which is very close to (and in direct contact with) the cooled section of the turbo.

Anyway, I'm actually curious to hear about your findings, as soon as you will have an opportunity to try the new exhaust and check it with a thermal gun while under way! :encouragement:

 

[Portofino]

I read somewhere when researching EGTs, that turbos take a fair slug of heat out around 200 degrees .
So the 600 figure is about right for manifold side preturbo .If that slug reduction is ball park then the elbow will feel about 400 degrees .
That said there are variations with each manufacturer regarding EGT s some run hotter than others , stuff like combustion chamber shape ,compression ratios ,injector position relative to the exhaust valve s + a whole load of other stuff .
CAT s are at the high end of the spectrum .
MAN at the other end - low .
Just an observation not criticism btw .

Can,t give Marc 10 out 10 , A + because there’s no probe ( or inspection ) port .This is usually a 10mm threaded bolt .
Handy to shove a camera periodically to sight the other side of the turbo blades .And possibility turn the other way and inspect for corrosion *
Or a conciencous engineer doing a presale survey - saves tearing off the elbow with inherent resealing risks .

Any exhaust bandage followed by Al foil wrap will do to cover it .Theres a shop was in Antibes sell all this stuff .

Just wondering about gaskets ?
There’s needs to be sufficient give at the U/W box end to compensate for minor misalignment at the fixed elbow end .
Or the gasket technique be able to cope if the riser is stiff unable to 100 % mate true ?

Anyways 9/10 and a normal A

* stainless steel in a marine environment is wonderful stuff no dought .But here we are talking the products of diesel combustion.Further up where the sea water meets the gad it’s sulpuric type acids that attract the metal not corrosion/ rust like say your guardrails .
This vapour after stop will drift back and start to eat the SS .
Just don’t want folks thinking using SS in the marine exhaust is a fit and forget .
To tbh it really depends on the type of SS the % of the stuff that reacts with sulphuric acid - chrome etc ?
Spent a career working with SS in a “ hostile environment “ seen a few things .

 

[MapisM]

Can,t give Marc 10 out 10 , A + because there’s no probe ( or inspection ) port

Coming to think of it, that's a good point - in fact, there was one also in the OEM elbows.
I suppose it can still be done thought, also in the future, whenever required.
In fact, the fabrication of it would have been ex-post also if included at design stage, I would think.

 

[markc]

Coming to think of it, that's a good point - in fact, there was one also in the OEM elbows.
I suppose it can still be done thought, also in the future, whenever required.
In fact, the fabrication of it would have been ex-post also if included at design stage, I would think.

Actually, there isn't one in the correct OEM ones. In the cracked ones there was the water inlet if the water jacket was being used, and a blank as the result of casting - nothing that would allow an EGT sensor or endoscope. Considering the other cylinder bank on both engines does not have the provision for this (with the correct OEM elbows), it seemed pointless doing so on these now. However, as MapisM said, if I change my mind in future it would be simple to drill, tap and weld a nut on the outside.

 

[vas]

I read somewhere when researching EGTs, that turbos take a fair slug of heat out around 200 degrees .
So the 600 figure is about right for manifold side preturbo .If that slug reduction is ball park then the elbow will feel about 400 degrees .

agree.
It's a known fact hence on highly pushed engines they want the EGT probe before the turbo (faster response and easier to tune apparently)

Can,t give Marc 10 out 10 , A + because there’s no probe ( or inspection ) port .This is usually a 10mm threaded bolt .

also agree would be handy no mater there's none on the other bank(s) Still good to be able to monitor that on your plotter/display

* stainless steel in a marine environment is wonderful stuff no dought .But here we are talking the products of diesel combustion.Further up where the sea water meets the gad it’s sulpuric type acids that attract the metal not corrosion/ rust like say your guardrails .
This vapour after stop will drift back and start to eat the SS .
Just don’t want folks thinking using SS in the marine exhaust is a fit and forget .
To tbh it really depends on the type of SS the % of the stuff that reacts with sulphuric acid - chrome etc ?
Spent a career working with SS in a “ hostile environment “ seen a few things .

true, but I mean do you see HOW THICK that elbow is?
Probably gonna crack due to heat cycling rather than get wasted due to corrosion...

anyway the problems with winter, doubt we'd bother that much on a brilliant solution if it wasn't Dec


cheers

V.

 

[markc]

agree.
It's a known fact hence on highly pushed engines they want the EGT probe before the turbo (faster response and easier to tune apparently)


also agree would be handy no mater there's none on the other bank(s) Still good to be able to monitor that on your plotter/display

Understood, now I think of it, when MTU did the engine survey they recorded EGT values across the rev range, so I assume these were taken from ports pre-turbos. I agree that it would be good to see these values live at the helm. I feel a project coming on!

 

[Assassin]

With T304 exhaust temperatures are not an issue as it is designed for 925 degrees C working continually and above 1500 for intermittent working and no MTU exhaust gases will ever reach this.

Putting an EGT probe in is a simple affair as you can get the stainless steel sockets in T 304, ready threaded, and with the correct profile of the outer diameter of the pipe and these are simply drill and weld items readily available for peanuts, all you need is the thread dimensions of the probe.