4722 replies to this topic

[Nev]

What kind of temps do you think your exhaust is withstanding around the turbo part

 

Hard to guesstimate really, the best way would be to insert a tiny pyrometer in there, which I did consider doing when I built it all up 7 years ago, but I didn't want the risk of it cracking and dropping into the turbo (with dire consequences).

 

The map is pretty rich (11.0:1 in places), but basically you have the equivalent heat of 500 electric bar heaters passing though this tiny 1" x 2" restriction at 24 PSI. The problem is exacerbated by taking already super hot gases and then compressing them and possibly causing them to get even hotter as per combined gas laws calcs. Then against this you have to offset the radiated heat loss, basically all too complicated for me to work out.

 

If I had to guess, maybe 950 to 1000 degree C when at full chat perhaps. It's certainly enough to melt and fuse the glass strand heat wrap on it - I only needed to tap it with a hammer to break it off the manifold in places.  

Edited by Nev, 03 July 2016 - 09:59 AM.

[CHILL Gone DUTCH]

I also thing my sc exhaust is reaching in access of 850 degrees

[Nev]

I also thing my sc exhaust is reaching in access of 850 degrees

 

I wouldn't be surprised if the gas exiting your cylinder head is more than that, but as soon as it can expand in the downpipe and exhaust it cools off surprisingly fast.

[smiley]

One of the germans measured near 1000.

But that was just after the cilinder head.

 

[CHILL Gone DUTCH]

One of the germans measured near 1000. But that was just after the cilinder head.  

Is this on a sc spec car ?

[redvts]

 

What kind of temps do you think your exhaust is withstanding around the turbo part

 

Hard to guesstimate really, the best way would be to insert a tiny pyrometer in there, which I did consider doing when I built it all up 7 years ago, but I didn't want the risk of it cracking and dropping into the turbo (with dire consequences).

 

The map is pretty rich (11.0:1 in places), but basically you have the equivalent heat of 500 electric bar heaters passing though this tiny 1" x 2" restriction at 24 PSI. The problem is exacerbated by taking already super hot gases and then compressing them and possibly causing them to get even hotter as per combined gas laws calcs. Then against this you have to offset the radiated heat loss, basically all too complicated for me to work out.

 

If I had to guess, maybe 950 to 1000 degree C when at full chat perhaps. It's certainly enough to melt and fuse the glass strand heat wrap on it - I only needed to tap it with a hammer to break it off the manifold in places.  

 

 

thermal imaging camera?

Edited by redvts, 03 July 2016 - 12:13 PM.

[chris_uk]

I also thing my sc exhaust is reaching in access of 850 degrees

 

is it glowing?

[CHILL Gone DUTCH]

I also thing my sc exhaust is reaching in access of 850 degrees

  is it glowing?

I don't know I'm normally driving the car Might try and set a camera up on it to see But I may have to wrap my exhaust as its starting to discolour the subframe and

[chris_uk]

best getting a thermal gun  thingie and pointing it at the manifold when it comes in, just to get an idea.

[CHILL Gone DUTCH]

best getting a thermal gun  thingie and pointing it at the manifold when it comes in, just to get an idea.

I might try a tape the gun trigger on and set up a camera on the gun & exhaust Lol

[Mopeytitan]

I also thing my sc exhaust is reaching in access of 850 degrees

  is it glowing?

I don't know I'm normally driving the car Might try and set a camera up on it to see But I may have to wrap my exhaust as its starting to discolour the subframe and

Very likely it will be before I wrapped mine, during the emissions test on MoT last year mine was glowing

[stu8v]

My guess is its a 304 grade stainless. Not really the ideal grade for turbo application, that coupled to insufficient bracing. Normally it's a case of going thicker wall or more expensive material inconel or such.

[CHILL Gone DUTCH]

I think mine is 307 grade not 100% as I know very little about grades of SS Does 307 sound right ?

[Mopeytitan]

308 I imagine? I'm sure they're 304, 308 and 316?... I might be wrong though

[TFD]

SS Grades normally implies the way they withstand corrosion as what I was told. 316 for more corrosion/salty conditions, 304 for the rest.

Exhaust gasses are normally 800-900C. 1000C sounds as not great, get your EGT's down. The cast iron exhaust housings of turbo tend to glow red when on full temp.... that hot.

 

Why do you run AFR 11:1 ? Did you monitior your EGT's?

[TFD]

Edit.

Edited by TFD, 03 July 2016 - 01:10 PM.

[stu8v]

304 is common general grade of which most use as it's cheap.

[Arno]

Peculiar crack, especially as the big flange went which is not something you usually see on tubular exhaust manifolds like these. Usually it will crack in/along the welds and likes to go onto the thinner wall sections like the pipes.

 

Might be able to have it cut/groove all the cracked sections out and then weld it back up. Then afterwards have the flange sanded flat again.

 

Might still distort/warp the position of the wastegate connnection but that's simply the risk of any repairs like these...

 

304/316 for manifolds is OK'ish, but not too great. Heat cracking is simply one of the things that will occur to it as the material is not really rated for these service temperatures (AFAIK it's only rated for sustained temperatures up to 300C)  and accelerated crack development is one of the issues. Especially in turbo manifolds with the extra heat and pressure before the turbo they will degrade and fail over some time and must really be seen a little as 'consumable'

 

An Inconel 625 based one would have a much longer lifespan as it is rated for these operating temps seen in a turbo manifold, but the material is much, much more expensive so it's a bit of an economic tradeoff between X cheaper stainless 304 manifolds vs. 1 inconel one and at what amount of 'X' the inconel one becomes interesting.

 

Bye, Arno.

[stu8v]

I know of folk using homemade SCH40 Carbon steel tubular manifolds with no issue. That many trackday miles too. Worth a thought if you're looking into making another. At the very least I'd cut that flange off and make another if you must re use your manifold. Given the work involved it's no more trouble imho.

[CHILL Gone DUTCH]

  Why do you run AFR 11:1 ? Did you monitior your EGT's?

Who is running 11:1