Exhaust gas temperatures 6/1

[oliver90owner]

If these temperatures measured are external pipe temperatures they will bear no correlation to the gas temperature inside.  Try this.  Measure the temperature, say at the pipe just prior to the muffler; now direct a compressed air jet onto that pipe and measure while doing this.  QED.

Regards, RAB

[oliver90owner]

I just worked out the percent of water produced by burning diesel fuel, and it ends up that about 7.5% by weight of the fuel you burn ends up as water vapor.  

Quinn, you may be quite right in what you say but at that time of night you may be giving the wrong impression to some less numerate or chemical......

Cetane C₁₆ H₃₄ will indeed have about 15 % of it's mass converted to water during combustion.  12*16 +1*34 = 226    and 34*100%/226  = approx 15%

However that 15% will produce  15%/2*18 = 135% water by weight of the fuel burned.

Just  a subtle difference in how the reader reads, and might be led to understand, your post.

Regards, RAB

[BruceM]

Geno, I'd sure like to learn more about your masonry muffler!

[quinnf]

RAB,

I counted the mass of atmospheric O2 into the calculation so our numbers are a little different.  
Point was, anytime you burn hydrocarbon fuel, you're going to generate water.  So to avoid ruining your exhaust, you need to keep the temperature high enough so you don't end up condensing the water vapor.  Even 316 stainless steel pinholes in marine exhausts, so that can be a real problem.  I think black iron pipe is still the material of choice for marine exhausts.  My bias is to keep the exhaust well wrapped with insulation.

Quinn

[Rom]

Just a lil thing on marine exhaust

Over here, we are actually running fibreglass pipe with silicone rubber exhaust hose to couple the engine exhaust elbows to the glass pipes. Most everyone over here agrees, as long as the exhaust is wet, fibreglass pipe can be run right to the water/exhaust jacket.

Rom

[Ronmar]

yep, that is one school of thought for marine exhaust systems.  Keep it all wet.  I have seen several now that have a water spray ring right at the turbo outlet...  Hot turbo with cold salt water spraying an inch away has never made me very comfortable, but it works.

[Rom]

Indeed, I must say I forget about turbos in boats.

The 2 family boats have Detroit Diesels in, one has twin NA 671s, and the other, twin NA 8v53s. No computers and no turbos!

Keeping it simple
Rom

[quinnf]

Ron,

Pleasure boats I can understand, but I can't recall ever seeing a fishboat (I mean a real one, not a Bayliner with outriggers) with any other than a dry exhaust. 

Quinn